GLAUCOMA SESSION-II - All India Ophthalmological Society

254 AIOC 2009 PROCEEDINGSGLAUCOMA SESSION-IIChairman: Dr. Rama Krishnan R, Co-Chairman: Dr. Rajiv ZutshiConvenor: Dr. Kriti Singh, Moderator: Dr. Ajeet JakharAUTHORS’S PROFILE:DR. DEBASISH DUTTA: M.B.B.S. (1995), N.R.S. Medical College, Calcutta University,Kolkata; M.S. (2000), M.K.C.G Medical College, Berhampur University; Fellowship (2004),Sankara Nethralaya, Chennai. Recipient of K.R. Dutta award (1999) in EIZOC, Cuttack.Presently, Consultant, Disha Eye Hospital & Research Centre, Barrackpore, Kolkata-120.It is Sufficient to Measure Central Corneal Thickness in One EyeOnly to Correct Applanation Tonometry in Both EyesDr. Debasish Dutta, Dr. Amitabha Kundu, Dr. Prashant Kumar Singhal,Dr. Saurabh Sanyal, Dr. Tushar Kanti Hazra(Presenting Author: Dr. Debasish Dutta)The only time tested treatable parameter ofglaucoma is intra ocular pressure (IOP).Manometry is unequivocally the best way ofmeasuring IOP. This being too invasive in vivoother means have been devised over the ages,like (1) Indentation Tonometry (Schiotz), (2)Applanation Tonometry (Goldmann / Perkins),(3) Ocular Blood Flow Tonometry, (4) NonContact Tonometry /Air Puff Tonometry.Amongst all these, Goldmann ApplanationTonometry GAT (Working on Imbert –FickPrinciple) has been accepted to be the mostreliable and reproducible.But it assumes all corneas to be about 520 micronthick.GAT corresponds best with manometry at a CCTof 520 micron.Anatomically thicker corneas overestimate IOPand vice versa.Imbert Fick principle assumes the eye to be1. Dry (but in reality tear film exerts a surfacetension pulling the tip of AT towards thecornea)2. A perfect sphere with infinitely thin wall(cornea has neither)Surface Tension (ST) attracts the tip towards it;while corneal deformation (Rigidity) throws thetip away. Now modulus of elasticity of cornealdeformation depends very much on CCT.The force of surface tension of tear film cancel outwith the force of corneal deformation at a CCT of520 micron.Goldmann was largely theoretical and thenumber of variables were to be reduced. Largepopulation based statistical analysis was notdone. CCT was chosen to be a constant at 500microns to reduce and simplify the equation.Ultrasound (US) pachymetry is currentlyconsidered as the gold standard in measuringcorneal thickness since it has a high degree ofintra operator and inter instrumentreproducibility.The drawbacks of US pachymetry are1. The handheld probe produce applanation of avariable degree displacing a variable amountof tear film.2. The compression may thin the epitheliumthus resulting in a slightly thinner CCT.3. No fixation target is available in theinstrument.Materials and MethodsIt is a retrospective, randomized, comparative,non-interventional case series in which 437patients (437 X 2 Eyes), between November 2006and March 2008, were chosen. CCT was done byAlcon ultrasound pachymeter.Age more than 40years was chosen keeping inmind that glaucoma develops in the middle age.

GLAUCOMA SESSION-II255Exclusion criteria :Spherical Refractive error > 4 DioptresCylindrical Refractive error > 2 DioptresAny corneal pathology (Fuchs and cornealdegeneration affecting curvature and thickness),Pregnancy, Diabetes Mellitus, Angle closureGlaucoma, any ocular surgery, Contact Lenswearers.Inclusion Criteria :Primary open angle glaucoma patients fulfillingthe following criteria. IOP more then 22mmhg atdiagnosis. Both newly diagnosed and old caseswere taken into account.Glaucomatous optic disc with its characteristicfeatures (Vertical C/D > horizontal C/D)asymmetric cupping, Polar or focal notch,Hemorrhage at disc margin, Peripapillaryatrophy, Bayoneting of blood vessels, Baring ofcircum linear vessels, Overpass cupping,Laminar dot Sign, Bean pot cupping etc.With or without nerve fibre layer defects.Glaucomatous field defects. (Fulfilling at leasttwo out of the 3 Andersons criteria).Open angle on gonioscopy with or withoutpigmented trabecular meshwork.All had at some point of time undergone 24-2program of Humphrey field analyser.All had been screened for retinal nerve fiber layerdefects by stratus OCT.All patients have undergone routine :Non contact tonometry, Auto refractokeratometry,Visual acuity and refraction, Slit lampexamination, Applanation Tonometry,Gonioscopy, Dilated Fundus examination, Discand nerve fiber layer examination with 78D/90D.Ocular Hypertensives are defined as : open angleon Gonioscopy. IOP>22mmHg, No Disc changes,No Fulfilling Andersons Criteria, No NFL defectson OCT.CCT was performed by a single operator.Corneal velocity is preset at 1641m/sec. Acalibration check was performed before actualmeasurements. All readings are noted between 9am and 5 pm, Patients were awake for 3 hoursbefore measuring to reduce swelling of corneafrom overnight eye closure.Topical anesthesia was achieved by 1drop ofproparacaine USP 0.5% in both the eyes.The patient is seated upright and made to fix at alight across the room by the other eye. Thehandheld probe is aligned as perpendicular aspossible on the central cornea; the hand is madesteady by placing it on the malar prominence ofthe patient. The ergonomics are favorable in theright eye of the patient with a right handedexaminer. 10 readings are taken in each eye andthe average is noted; the highest value is givenpriority and the lower values are discarded so asto keep the standard deviation within 2.ResultsTotal of 437 patients were chosen. 290 from theGOPD register which includes ocular hypertensives,normal tension glaucoma.147 patient werechosen from the general OPD register who hadundergone CCT as glaucoma suspects.Pearson correlation is 0.87(almost equal to 1) t-statistics is 0.65 ( less than 1.96)A paired t-test was performed on the CCT datato determine whether the CCT of both the righteye and the left eye are significantly differentfrom each other.We note from the above obtained results that thetwo-tail p value is 0.5133 which indicates that thenull hypothesis of equal CCT of right eye and lefteye is accepted .Hence we can conclude that theCCT of both right eye and left eye are notsignificantly different from each other.Next a paired t-test was performed on the samedata to determine whether the CCT of right eye issignificantly less than that of the left eye. Againwe note from the results that the one tail p valueis 0.256657 indicating that the null hypothesis ofequal CCT of both right eye and left eye isaccepted. Hence we can conclude that the CCT ofright eye is not significantly less than that of lefteye.Paired t-test was performed between CCT ofright eye of males and CCT of right eye offemales. It is found that two-tail p value is 0.589which means that equal CCT of male and femaleis accepted. This holds good for left eye of maleand female also.Arithmetic mean was (6.48micron) with range(maximum 41 and minimum is “0” Zero)MEAN DEVIATION - 3.69 Micron

256 AIOC 2009 PROCEEDINGSSTANDARD DEVIATION - 6.14 Micron.So 99.7% of values will fall under 3SD ie. 3 X 6.14=18.42Micron.DiscussionAccurate measurement of IOP is extremelyimportant in making the diagnosis of glaucomaand in its management and treatment plans suchas choosing medications, laser treatment andsurgery.So CCT adds a feather in the cap in the diagnosisof true glaucoma, true ocular hypertension, andtrue low tension glaucoma as suggested byOcular Hypertension Treatment Study. Otherfactors to be taken into account for accurate IOPvalues are ethnicity, flat or thin corneas.So CCT correction of AT is more of a routinepractice rather than as and when required.Now the question is do we need to do itseparately in both the eyes of the same individualto correct AT.There being no significant difference in the CCTbetween the two eyes; it can be said that it issufficient to perform CCT in one eye only of anindividual. Now AT is a subjective measurement.The inter observer variation is 4mm Hg and theintra observer variation is 1.5 to 2mm Hg.Corneal thickness varies considerably during theawake hours upto 4%.A 13.5 micron change in CCT corresponds to1mm of Hg of correction;For every 18.42 (3SD ie. 99.7% micron correctionfactor is 1.36 mm of Hg.So if CCT is measured in the second eyeseparately to correct AT we will be getting ATmore precise by 1.36mm of Hg. The interobserver variation is 4 mm of Hg (much morethat 1.36) and intra observer variation is 1.5 - 2mm of Hg (more that 1.36). So it is definite thatCCT for one eye only is sufficient.Some studies have found systematic right –leftdifference; The left cornea being significantlythicker. The cause has been attributed tomeasurements not done perpendicularly to thecornea. In our selected group no such variationwas noted.AUTHORS’S PROFILE:DR. MAITHILI KULKARNI: M.B.B.S. (’98), N.K.P. Salve Institute of Medical Sciences, NagpurUniversity; D.O.M.S. (2003), Terna Institute of Medical Sciences, Mumbai University;Fellowship in Glaucoma and Cataract (2006), Suraj Eye Institute, Nagpur. Senior clinical fellow(2007), Suraj Eye Institute. Presently, working as research associate at Suraj Eye Institute,NagpurE-mail: maithili1kulkarni@yahoo.com.Cup Disc Area Ratio in an Adult Population in Central India. TheCentral India Eye and Medical StudyDr. Maithili Kulkarni, Dr. Monica Yadav, Dr. Vinay Kumar Nangia ,Dr. Krishna Bhojwani, Dr. Arshia Matin, Dr. Jost Jonas(Presenting Author: Dr. Maithili Kulkarni)The Cup Disc Area ratio is an importantassessment and follow up parameter indeciding the normality or otherwise of the opticnerve. The optic disc cup shows highinterindiviual variability just as the optic discsize. In normal eyes, the cup and disc size showcovariance. 1 It was the purpose of this study todetermine the CD area ratio in a populationbased study in Central India. The cup disc ratiosare low in small optic discs and high in largeroptic discs. 2 The cup disc relationship is alsosignificantly important for the definition ofglaucoma. 3 Baseline cup disc ratios have beenidentified to be important predictors ofdevelopment of glaucoma in ocular hypertensiveindividuals. 4 . The cup disc area ratios have beenmeasured previously with the CSLO 5 and inSouthern India with fundus photography. 6 It wasthe purpose to ascertain the CD area ratios in apopulation in Central India with the CSLO forwhich data are not available.

GLAUCOMA SESSION-II257Materials and MethodsThe Central India Eye and Medical Study(CIEMS) is a population based study conductedin a rural area about 40 kms from Nagpur. 6 In aninterim analysis, 3393 of 4291 subjects (responserate 79.1%) aged 30 and above were examined.The medical ethics committee of the Suraj EyeInstitute had approved the study protocol and allparticipants had given informed consentaccording to the declaration of Helsinki. Entirepopulation in the villages included in the studywas enumerated. The ophthalmic evaluationincluded visual acuity using ETDRS charts,refraction, slit lamp biomicroscopy, applanationtonometry, gonioscopy, biometry, pachymetry,fundus examination and photography afterdilatation, and confocal scanning laserophthalmoscopy with the Heidelberg RetinaTomography II (software V 3). Medicalevaluation included pulse, blood pressure,height, weight, ECG, X-ray, complete bloodcount and serum and blood biochemistry,including kidney function tests. Intraocularpressure was recorded with the slit lampmounted Goldmann applanation tonometer. Thecorneal thickness was measured usingultrasound pachymetry. A total of 1817 subjectswere included in the present investigation. Theoptic disc of one randomized eye of includedsubjects was measured by confocal scanning lasertomography. The contour line was drawn bykeeping the image of the optic disc adjacent to thescanning laser image. The instrumentautomatically generates several optic discparameters including disc size, cup area andneuroretinal rim area. Aphakes, pseudophakeswere excluded from analysis. The mean age ofsubjects included in the study was 46.74 ±12.81yrs. (range 30-95) there were 818 males. The meanIOP was 13.80±3.03 mm Hg (range 4 to 35).ResultsThe mean disc area was 2.23±0.48 mm 2 (range1.04-4.61); cup area was 0.56±0.40 (range 0.00-3.25). Cup disc area ratio was 0.236±1.36 (range0.00-0.87). There was no significant differencebetween males and females (p=0.13) The CD arearatio showed a significant positive correlationwith age (P

258 AIOC 2009 PROCEEDINGSassociation with larger disc area which is knownto correlate with myopic spherical equivalent andincreasing axial length. CD area ratio has not yetbeen determined on the CSLO for such a largegroup of subjects in a population based study.Further data from Central India are not availableReferencesfor the optic disc morphometry. This study givea large population based data on the values ofCD area ratio which may prove to be valuable indevelopment of indices based on imagingtechnology to predict, diagnose and follow upglaucoma.1. Bengtsson B. The variation and covariation of cupand disc diameters. Acta Ophthalmol 1976;54:804-18.2. Jonas JB, Zach FM, Gusek GC and Naumann GOH.Pseudoglaucomatous physiologic large cups. Am. J.Ophthalmol. 1989;107:137-44.3. Foster PJ, Buhrmann, R, Quigley HA, Johnson GJ.The defintion and classification of glaucoma inprevalence surveys. Br. J. Ophthalmol 2002;86:238-42.4. Gordon MO, Beiser JA, Brandt JD, et.al. The OcularHypertensive Treatment Study. Baseline FactorsThat Predict the Onset of Primary Open AngleGlaucoma. Arch. Ophthalmol. 2002;120:714-20.5. Hermann MM, Theofylaktopoulos I, Bangard N,et.al. Optic Nerve Head Morphometry In healthyAdults using Confocal Laser ScanningTomography. Br J Ophthalmol 2004;88:761-5.6. Jonas, JB, Thomas R, George R, Berenshtein E, MuliyilJ. Optic Disc Morphology in South India: TheVellore Eye Study. Br J Ophthalmol 2003;87:189-96.7. Vernon SA, Hawker GA, Hillman JG, MacNab HKand Dua HK. Laser Scanning Tomography of theOptic nerve Head in a Normal Elderly Population:The Bridlington Eye Assessment Project.Investigative Ophthalmology and Visual Science.2005;46:2823-8.8. Hermann MM, Theofylaktopoulos I, Bangard N,et.al. Optic Nerve Head Morphometry in HealthyAdults Using Confocal Laser ScanningTomography. Br J Ophthalmol 2004;88:761-5.9. Nangia V, Matin, A, Bhojwani K, Kulkarni M,Yadav M, and Jonas J. Optic Disc Size In aPopulation Based Study In Central India: theCentral India Eye and Medical Study. (CIEMS). ActaOphthalmol. Scandinavia. 2008;86:103-4.Association Between Neuroretinal Rim and Age in TheAdult Population in Central India. The Central India Eye andMedical StudyDr. Monica Yadav, Dr. Vinay Kumar Nangia, Dr. Ajit Kumar Sinha,Dr. Arshia Matin, Dr. Jost Jonas(Presenting Author: Dr. Monica Yadav)The neuroretinal rim area is an importantmorphometric clinical sign of glaucomatousdamage and represents the intrapapillaryequivalent of the retinal nerve fibers. 1 It is knownto be associated with optic disc size and optic discsize has a correlation with the retinal nerve fibercount. 2 There is significant variation in the size,shape and appearance of the neuroretinal rim aswith the optic disc. Therefore diagnosis in earlyglaucoma may be difficult. Besides thedependence of the neuroretinal rim on the opticdisc size, it may be influenced therefore by allocular and systemic parameters that influencethe optic disc size such as myopia, age andgender. 3,4 Studies have shown that theneuroretinal rim area and retinal nerve fiberthickness decreases with increasing age. 5,6 Otherstudies 7,8 did not find a correlation of age anddecrease in the neuroretinal rim area. It was thepurpose of this study to assess the correlation ofthe neuroretinal rim with age in a populationbased study in Central India using the ConfocalLaser Scanning Ophthalmoscope on a largenumber of subjects.Materials and MethodsThe Central India Eye and Medical Study(CIEMS) is a population based study conductedin a rural area about 40 kms from Nagpur. In aninterim analysis, 3393 of 4291 subjects (responserate 79.1%) aged 30 and above were examined.The medical ethics committee of the Suraj EyeInstitute had approved the study protocol and allparticipants had given informed consent

GLAUCOMA SESSION-II259according to the declaration of Helsinki. Entirepopulation in the villages included in the studywas enumerated. The ophthalmic evaluationincluded visual acuity using ETDRS charts,refraction, slit lamp biomicroscopy, applanationtonometry, gonioscopy, biometry, pachymetry,fundus examination and photography afterdilatation, and confocal scanning laserophthalmoscopy with the Heidelberg RetinaTomography II (software V 3). Medicalevaluation included pulse, blood pressure,height, weight, ECG, X-ray, complete bloodcount and serum and blood biochemistry,including kidney function tests. Intraocularpressure was recorded with the slit lampmounted Goldmann applanation tonometer. Thecorneal thickness was measured usingultrasound pachymetry. A total of 1797 subjectswere included in the present investigation. Theoptic disc of one randomized eye of includedsubjects was measured by confocal scanning lasertomography. The contour line was drawn bykeeping the image of the optic disc adjacent to thescanning laser image. The instrumentautomatically generates several optic discparameters including disc size, cup area andneuroretinal rim area. Aphakes, pseudophakesand those with IOP greater than 21 mm Hg wereexcluded from analysis. The mean age of subjectsincluded in the study was 46.70 ±12.79 yrs. (range30-95) there were 808 males.ResultsThe mean IOP was 13.72 ± 2.86 mm Hg (range 4to 21). The mean optic disc area was2.23±0.47mm 2 . The mean rim area was1.67±0.34mm 2 (range 0.38, 3.97mm2). Meanvalues for spherical equivalent were -0.18±1.43D.Mean rim area showed significant correlationswith age (P=0.013;r=-0.058), male gender(p=0.003;r=0.071), myopic refractive error(P

260 AIOC 2009 PROCEEDINGS1. Jonas JB, Budde WM, Panda-Jonas S.Ophthalmoscopic evaluation of the optic nervehead. Surv Ophthalmol 1999;43:293-20.2. Quigley HA, Coleman AL, and Dorman-Pease ME.Larger Optic nerve heads have more nerve fibers innormal monkey eyes. Arch. Ophthalmol. 109:1441-3.3. Garway-Heath DF, Wollstein G, Hitchings RA.Aging Changes of the optic nerve head in relation toopen angle glaucoma. 1997;81:840-5.4. Vernon SA, Hawker MJ, Ainswoirth G, et. al. LaserScanning Tomography of the Optic Nerve Head ina Normal Elderly Population: The Bridlington EyeAssessment Project. Investigative Ophthalmology andVisual Science. 2005;46:2823-8.5. Tsai CS, Ritch R, Shin DH, Wan JY and Chi T. AgeReferencesrelated decline of disc rim area in visually normalsubjects. Ophthalmology 1992;99:29-35.6. Parikh RS, Parikh SR, Chandrasekhar G, et.al.Normal Age-Related Decay of Retinal Nerve FiberLayer Thickness. Ophthalmology 2007;114:921-6.7. Funk J, Dieringer T and Grehn F. Correlationbetween neuroretinal rim area and age in normalsubjects. Graefe’s Arch Clin Exp Ophthalmol1989;227:544-8.8. Kee C, Koo H, Ji Y and Kim S. Effect of optic discsize or age on evaluation of optic disc variables.British Journal of Ophthalmology 1997;81:1046-9.9. Jonas JB, Schmidt AM, Muller-Bergh JA, et. Al.Human optic nerve fiber count and optic disc size.Investigative ophthalmology and visual science.1992;33:2012-8.AUTHORS’S PROFILE:DR. VINAY KUMAR NANGIA: M.B.B.S. (’80) and M.S. (’84) from Government MedicalCollege, Nagpur University; Fellowship (’86), FRCS (’89), Royal College of Physician andSurgeon. Formerly, Fellow and Consultant, Vitreo Retinal Surgery, Medial Research Founation,Madras, Sankara Nethralaya, Chennai; Resident Ophthalmology, Royal Eye Hospital,Manchester, U.K.; Registrar and Clinical Tutor, Aberdeen University, UK;Presently Director, Suraj Eye Institute, Nagpur. Contact: 9890020804.Pattern of Retinal Nerve Fiber Layer Loss in Primary Open AngleGlaucomaDr. Vinay Kumar Nangia , Dr. Monica Yadav, Dr. Ajit Kumar Sinha,Dr. Nikhil Khanorkar, Dr. Krishna Bhojwani(Presenting Author: Dr. Vinay Kumar Nangia)Loss of retinal nerve fiber layer is a sign ofglaucomatous damage. The retinal nervefiber bundles are known to be significantly moreoften better detectable in the inferotemporalregion than in the superotemporal reg ion. 1 Thecharacteristic double hump pattern with thenerve fiber layer thickest inferiorly, thensuperiorly, then nasally and thinnest temporallyhas also been demonstrated in histologicalstudies of the normal optic disc. 2 Clinicalevaluation of the retinal nerve fiber layer defectsallows one to detect classical wedge shapeddefects in glaucoma 3,4 Experimental studies haveshown that localized RNFL defects can beopthalmoscopically detected if more than 50% ofthe thickness of the retinal nerve fiber layer islost. 5 Diffuse loss of retinal nerve fiber layer iswell known in glaucoma and one may need tocompare the different quadrants of the retina fornerve fiber layer visibility to ascertain a relativelygreater loss. 6 The optic disc rim is considered torepresent the retinal nerve fiber. The pattern ofrim loss involves loss of superior and inferior rimin modest glaucomatous damage. In moderatelyadvanced glaucomatous damage the temporalhorizontal disc region shows the most markedrim loss. In very advanced glaucoma the rimremnants are located mainly in the nasal discsector with a larger remnant in the upper nasalarea. 7 Based on the above knowledge it was thepurpose of this study to ascertain the pattern ofretinal nerve fiber layer loss using the confocallaser scanning ophthalmoscope in eyes withprimary open angle glaucoma and compare theloss with normative data from a populationbased study.Materials and MethodsIn a clinic based study 149 eyes of 79 POAGsubjects were included. All underwent an

GLAUCOMA SESSION-II261ophthalmic evaluation, including gonioscopy,applanation tonometry, optic disc evaluation andconfocal scanning laser ophthalmoscopy.Drawing the contour line around the disc yieldedthe optic disc area and retinal nerve fiber layerthickness (RNFLT) along the optic disc margin onCSLO. There were 17 females. Mean refractiveerror was -0.81±2.24 D. Mean age was 57.3±11.5yrs. Mean defect was 9.2±8.68dbs. Mean discarea was 2.43±0.52mm. 2 Normal RNFLTdistribution values available from The CentralIndia Eye and Medical Study (CIEMS) is apopulation-based study conducted in a rural areaabout 40 kms from Nagpur. In an interimanalysis, 3393 of 4291 subjects (response rate79.1%) aged 30 and above were examined. Themedical ethics committee of the Suraj EyeInstitute had approved the study protocol and allparticipants had given informed consentaccording to the declaration of Helsinki. Entirepopulation in the villages included in the studywas enumerated. The ophthalmic evaluationincluded visual acuity using ETDRS charts,refraction, slit lamp biomicroscopy, applanationtonometry, gonioscopy, biometry, pachymetry,fundus examination and photography afterdilatation, and confocal scanning laserophthalmoscopy with the Heidelberg RetinaTomography II (software V 3). The referenceplane height was calculated 50 um posterior tothe mean height contour along a small temporalsection of the contour line. Parameters weremeasured using this reference plane. . Thecontour line was drawn keeping in view thecolour optic disc photograph on the samecomputer screen. A total of 1797 subjects wereincluded in the present investigation. The opticdisc of one randomized eye of included subjectswas measured by confocal scanning lasertomography. Aphakes, pseudophakes and thosewith IOP greater than 21 mm Hg were excludedfrom analysis. The mean age of subjects includedin the study was 46.70 ±12.79 yrs. (range 30-95)there were 808 males. The mean IOP was13.72±2.86 mm.Hg. The mean optic disc area was2.23±0.47mm2.ResultsThe mean RNFLT values in glaucoma andnormals and the percent difference in thesegments are given in the table below.The percentage loss for all segments rangedbetween 40-47%, except for the temporal segmentwhere it was 25%.RNFLT Normals Glaucoma % Diff-(mm)erenceGlobal 0.25±0.07 0.143±0.08 42.8Nasal Superior 0.35±0.11 0.21±0.11 40Nasal Inferior 0.36±0.11 0.21±0.14 41.3Temporal Superior 0.283±0.09 0.16±0.10 43Temporal Inferior 0.267±0.09 0.14±0.14 47.56Nasal 0.288±0.10 0.152±0.11 47.22Temporal 0.08±0.02 0.06±0.035 25DiscussionIn this study a group of subjects with POAG witha mean deviation of 9.2±8.68dbs. underwentretinal nerve fiber layer analysis with theconfocal laser scanning ophthalmoscope. TheRNFLT values were then compared to valuesobtained from normal eyes from a populationbased study. By the time the retinal nerve fiberlayer loss whether focal or diffuse becomesvisible a significant degree of glaucomatousdamage may have occurred. In addition it isoften hard to differentiate the degree of lossclinically in different segments related to theoptic disc. Using the CLSO in this group ofsubjects it was seen that RNFLT was reduced inall segments of the Heidelberg RetinaTomograph. The RNFLT was reduced in allsegments compared to the normal eyes.Minimum RNFLT was seen in the Temporalsegment and the loss of thickness was least, thisis in keeping with the histological finding that theRNFLT is thinnest in this region than in otherareas (2). The maximum loss compared tonormal eyes was seen in the temporal inferiorthen in the nasal sector followed by the temporalsuperior, nasal inferior and nasal superior.During clinical evaluation normally the superotemporal nerve fibers along arcades are morevisible and therefore assessed. However due tothe vast variation it may be that significantclinical expertise may be required to assess theretinal nerve fiber. The CLSO offers an objectivemethod of assessing the RNFLT. While in thecurrent group of subjects the maximum loss wasseen in the temporal inferior sector it was notpossible to evaluate the evolution of the pattern

262 AIOC 2009 PROCEEDINGSof RNFL loss, since it was one time assessment.While it reinforces the clinical guideline thatemphasis should be paid to the superior andinferior poles most, further studies may enable1. Jonas JB, Nguyen NX, and Naumann GOH. Theretinal nerve fiber layer in normal eyes.Ophthalmology 1989;96:627-32.2. Dichtl A, Jonas J, Naumann GOH. Retinal nervefiber layer thickness in human eyes. Graefe’s ArchClin Exp Ophthalmol. 1999;237;474-9.3. Hoyt WF, Frisen, LL, an d Newman N.M.Fundoscopy of nerve fiber layer defects inglaucoma. Invest. Ophthalmol. 1973;12:313-9.4. Jonas JB, Schiro D: Localised wedge shaped defectsThe multifocal electroretinogram (mfERG)technique records multiple local responsesfrom the central retina. The mfERG recordedfrom monkeys varies across the retina. Theaveraged responses obtained from hexagonalzones equidistant from the fovea but at varieddistance from the optic nerve head, shownasotemporal disparity in monkeys. Thisdisparity in mfERG disappeared on repeatedrecording following intravitreal injection oftetrodotoxin and n-methyl DL aspartate thatprevents activation of ganglion cells.Nasotemporal disparity was demonstrated inhuman mfERG in standard second order kernelresponse. The latency of the waveform increasedwith distance of the stimulated patch from theoptic nerve head. This component is thought tobe originating from the ganglion cell axonsaround the optic nerve head. The first orderkernel response although initially thought todemonstrate little of nasotemporal disparity, wassubsequently shown to demonstrate thisphenomenon with high as well as low contrast.High contrast demonstrated a small latencydifference in the responses between zones nasaland temporal to fovea. However, thisphenomenon is similar to what is seen in monkeymfERG in first order kernel responses with alower stimulus contrast of 50%. TheReferencesus to assess specific sectors for progressive RNFLloss. Patterns of progressive loss may increaseour understanding of the course of the diseaseand its management.of the retinal neve fiber layer in glaucoma. Br JOphthalmol 1994;78:285-90.5. Quigley HA, Addicks EM: Quantitative studies ofretinal nerve fiber layer defects. Arch Ophthalmol1982;99:137-43.6. Jonas JB, Dichtl A. Evaluation of the retinal nervefiber layer. Survey of Ophthalmology 1996;40:369-78.7. Jonas J, Budde WM. Diagnosis and Pathogenesis ofGlaucomatous Optic Neuropathy: MorphologicalAspects. Progress in retinal and eye research. 2000:19:1-40.Differential Functional Involvement of Cone Photorecetors inAdvanced GlaucomaDr. Ajoy Vincent, Dr. Rohit Shetty, Dr. Sathidevi A.V., Dr. Bhujang Shetty(Presenting Author: Dr. Ajoy Vincent)nasotemporal disparity saturates at 60% contrast 7settings and at higher contrast the outer retinalcontribution to mfERG continues to grow. Thenasotemporal disparity was not demonstrable insubjects with primary open angle glaucoma(POAG) and diabetic retinopathy. However,another report found that nasotemporal disparitywas still demonstrable in some cases of POAG.The mfERG implicit time values were delayed inpatients with glaucoma and the delay wasinversely proportional to mean sensitivity valuesof static perimetry.The density of human cone photoreceptors hasbeen reported to be significantly higher in thequadrant nasal to the fovea. The currentknowledge suggests that the ‘N1’ and ‘P1’ wavesof first order kernel response of photopic mfERGarise from the cones and the cone bipolar cellsrespectively. Thus the histological difference incone density across retina may be functionallydemonstrated as nasotemporal disparity usingmfERG. Hence one of the purposes of the studyis to demonstrate an amplitude component ofnasotemporal disparity and to explain its conephotoreceptor origin, in first order kernelresponses, of photopic mfERG using high framerate and high contrast setting in normal subjects.In glaucoma, the neuroretinal rim thins in a

GLAUCOMA SESSION-II263sequential manner, the nasal rim to be affectedlast. Photopic and scotopic full field ERGresponses from glaucoma subjects showedchanges in ‘a’ and ‘b’ wave parameters.Sequential mode of functional impairment ofunderlying cone photoreceptors is possible inglaucoma. An attempt therefore has been madeto see if the amplitude component ofnasotemporal disparity can be used to detect thepotential presence of sequential, functional conephotoreceptor damage in glaucoma.Materials and MethodsProspective, cross sectional, case control series.The protocol adhered to the Declaration ofHelsinki and was approved by InstitutionalEthical Board.Human Subjects: The mfERG was recorded fromthirty eyes of normal, healthy volunteers andthirty eyes of glaucoma subjects (age range 38 –79 years). All the glaucoma subjects hadmoderate (15 eyes) or advanced (15 eyes) visualfield defects as per Hodapp, Parrish andAnderson’s classification. The intraocularpressure (IOP) of all glaucoma subjects wasunder good control. The glaucoma patientsunderwent detailed ophthalmological evaluationincluding, best corrected distant and near vision,applanation-tonometry, gonioscopy, slit lampbiomicroscopic evaluation of optic disc,Humphreys 30 – 2 visual field analysis and RNFLthickness measurement by Stratus OcularCoherence Tomography (OCT). None of thepatients had any other retinal pathology. All thesubjects had best corrected distance visual acuity> 20/40. Before recording, the pupil was fullydilated with 1% tropicamide and 2.5%phenylepherine. The cornea was anaesthetizedwith 0.5% proparacaine and mfERG wasrecorded with jet electrodes.Methods of Analysis: The mean N1 and P1amplitudes from all the local responses of thenasal quadrant and temporal quadrant of theretina (relative to the fovea) were compared toeach other (Figure 1). The response from the zoneof the optic nerve head and its correspondingzone in the temporal side was not considered asphotoreceptor density in the zone including theoptic nerve head would be less. This pattern ofanalysis was used, as the cone density is highestalong the horizontal raphe nasal to the fovea.ResultsAnalysis of Normal subjects: The figure 1demonstrates the amplitude component ofnasotemporal disparity in normal subjects.Figure 2 shows the mean and 95% confident limitvalues of nasotemporal disparity for each waveparameter of N1 and P1. Only the amplitudeparameters of N1 and P1 show nasotemporaldisparity.Comparison of nasotemporal disparity ratioamong normal subjects, patients with moderateglaucomatous field defects and patients withadvanced glaucomatous field defects.The mean nasotemporal disparity in the threegroups is given in Table-1.Table-1: Mean nasotemporal disparity ratio forN1 and P1 amplitude in the groupsNasotemporal Group Mean ± Std.disparityDeviationParameterN1 Amplitude Normal 1.23 ± 0.15Moderate visualfield defect 1.21 ± 0.09Advanced visualfield defect 1.01 ± 0.10P1 Amplitude Normal 1.16 ± 0.13Moderate visualfield defect 1.11 ± 0.09Advanced visualfield defect 0.96 ± 0.10A statistically significant difference was foundfor both N1 and P1 amplitude parameterbetween normal and advanced visual field defectgroup (p

264 AIOC 2009 PROCEEDINGShigher than the summed local responses obtainedfrom corresponding zones temporal to foveawhen analyzed in normal subjects. Previousreports on cone photoreceptor density inenucleated human and monkey eyesdemonstrated a significantly high coneconcentration in the region nasal to fovea. Theganglion cell density is also higher in the regionnasal to fovea. However, ganglion cellcontribution to mfERG is seen more in secondorder kernel response and its cell contribution tofirst order kernel response is significantly highonly when lower contrast setting is used.Moreover, the nasotemporal disparity ofganglion cell origin contributes to the doublepeaking of responses obtained from the zonenasal to fovea with a comparative delay inimplicit time of the waveform responses obtainedtemporal to fovea. The summed first orderresponse for N1 and P1 obtained from the twozones neither shows a latency delay in thewaveform obtained from the temporal zone norshows a double peaking of the response from thenasal zone. The stimulus parameters of highframe rate, high luminance and high contrastfavored isolation of responses from the conesystem. This strongly suggests that nasotemporaldisparity seen in amplitude component of N1and P1 waveform has its origin from the retinalcone photoreceptors and bipolar cellsrespectively.The neuroretinal rim of the optic nerve isbroadest inferiorly, followed by superior, nasal,and temporal region. RNFL thickness analysis byOCT confirms this pattern thickness ofneuroretinal rim. Glaucoma is primarily a diseaseinvolving the ganglion cell layer. In glaucoma,the neuroretinal rim is lost in all sectors of theoptic disc with regional preferences, dependingon the stage of disease. The neuroretinal rimthinning occurs in a sequential manner and thenasal rim is affected at last. Anatomical studiesin enucleated eyes of glaucoma subjects,demonstrated varied results. Enucleated eyeswith primary open angle glaucoma failed toshow histological evidence of photoreceptordamage. However, the sample size of the studybeing modest was capable of detectingphotoreceptor damage only if more than onefourthphotoreceptor cells were affected. Theenucleated eyes of secondary angle closureglaucoma subjects showed decreasedphotoreceptor count. However, a subset ofpatients in this group had other co-morbid eyepathology, which may have influenced theresults. Earlier electrophysiological studies donewith full field/ flash ERG in glaucoma has shownaffection of both scotopic and photopicresponses. The changes were more pronouncedin glaucoma subjects with advanced optic nervedamage suggesting that photoreceptors are moresignificantly affected in advanced glaucoma.Later studies report the reduction of ‘a’ waveamplitude and prolongation of ‘b’ wave implicittime of scotopic flash ERG in advancedglaucoma. However, a recent study on photopicfull field ERG in experimental glaucoma did notreveal any change of amplitude of ‘a’ and ‘b’wave. However, an absence of photopic negativeresponse was reported in the same study. Thefact that photopic responses are much smallerthan scotopic responses and the fact that onlyadvanced glaucoma shows changes in scotopicresponses are the probable reasons for the normal‘a’ and ‘b’ wave parameters of photopic ERG asreported by some. These evidences suggest thatthere is a definite functional impairment ofphotoreceptors in glaucoma, more so inadvanced cases. In the study, the N1 and P1amplitude component of nasotemporal disparityof photopic mfERG seen in normal subjects wasseen to be preserved in glaucoma subjects withmoderate visual field defects. However, both theN1 and P1 amplitude component ofnasotemporal disparity was not demonstrable inglaucoma subjects with advanced visual fielddefects. The preservation of nasotemporaldisparity in patients with moderate visual fielddefects suggests that cone photoreceptors are notdifferentially affected at this stage. If the conephotoreceptor impairment followed the samesequential pattern as for RNFL damage inglaucoma, then the amplitude components ofnasotemporal disparity should have increased insubjects with moderate visual field defects.Further, the absence of nasotemporal disparityratio in patients with advanced field defectsstrongly suggests a differential conephotoreceptor functional damage in the regionnasal to the fovea in patients with advanced fielddefects. Hence, the cone photoreceptor damagein glaucoma does not appear to be following the

GLAUCOMA SESSION-II265Fig-1: Method of analysis showing nasotemporal disparity in normal subjects.Fig-2: Error plot showing the mean and 95% confidence limit values fornasotemporal disparity. The x axis represents wave parameters and y axis representsnasotemporal disparity ratio. It shows the mean and 95% confidence limitsof nasotemporal disparity for all parameters of N1 and P1 as calculated.same sequential pattern of RNFL thinning.However, there appears to be a severedifferential functional affection of cones nasal tothe fovea as the disease progresses to reach theadvanced stage. Surprisingly, reversal ofnasotemporal disparity ratio for both N1 and P1amplitude parameters was seen in some patients.The reversal of nasotemporal disparity furtherconfirms the differential involvement of conephotoreceptors and cone bipolar cells inadvanced glaucoma. However, the functionalimpairment of the cone photoreceptors need notnecessarily translate into a structural impairment,which possibly explains the normalphotoreceptor density reported in glaucoma.Thecause for photoreceptor impairment in glaucomahas been attributed to multiple factors includingretrograde degeneration of bipolar cells andphotoreceptors, ischaemiaand vascular pathologysecondary to prolongedincrease in IOP. Thedifferential cone systeminvolvement in advancedglaucoma may be explainedbased on the pressure effect.The nasal rim is affected lastin glaucoma and hence theretrograde degeneration ofcone photoreceptors in theregion nasal to fovea happensonly when the RNFLthickness in the regionreduces beyond a criticallevel. Since the cone density is highest in thisregion, once RNFL thins beyond the critical level,higher numbers of cones in the region aredamaged causing disappearance ofnasotemporal disparity.To conclude, in normal subjects, the amplitudecomponent of nasotemporal disparity in firstorder kernel responses of mfERG, originatesfrom the cone photoreceptors and bipolar cells.Any normal, regional, anatomical variations ofdifferent cell types across the retina may befunctionally demonstrated by using customizedstimulus setting of mfERG. To the best of ourknowledge, this is the first report on thedifferential functional impairment of conephotoreceptors and cone bipolar cells inadvanced glaucoma.Comparison of Visual Field Defects and Retinal Nerve Fibre LayerAnalysis by OCT in Established Cases of GlaucomaDr. Reena Manchanda Choudhry, Dr. Tanushree Chakraborty(Presenting Author: Dr. Tanushree Chakraborty)Glaucoma, a disease characterized byprogressive degeneration of retinal nervefibres affects around 65 million peopleworldwide . According to various studies theprevalence of glaucoma in India ranges from2.6% to 4.15%.Evaluation of visual fields by Standardautomated perimetry is considered as the goldstandard for the diagnosis and monitoring theprogression of glaucoma. But, it has its ownlimitations as visual field defects become evidentonly after at least 30% of retinal nerve fibres haveundergone damage and being a subjective test, isdependant on the patients’ co-operation andperformance. Optical coherence tomography(OCT), based on low-coherence interferometryhelps in pre-perimetric diagnosis of glaucomaand is independent of the patient factors in

266 AIOC 2009 PROCEEDINGSmonitoring theprogression ofglaucoma. Theobjective of thecurrent study is tocorrelate theaverage retinalsensitivity of thesuperior andinferior hemi-fieldon StandardautomatedFig-1: Scatterplot of F-RNFLIavg vs. Superior Visual Field perimetry with theaverage retinalnerve fibre layer thickness in Optical CoherenceTomography (Fast 3.4 RNFL Scan) of the inferiorand superior quadrants respectively.Materials and MethodsThis is a prospective study being conducted atICARE Eye Hospital and Glaucoma ResearchInstitute, NOIDA in U.P. All POAG patientsshowing optic nerve head changes characteristicof glaucoma with visual field defects inHumphrey’s automated perimetrycorresponding to ONH changes, attending theHospital since November 2007, were enrolled inthe study. The criteria to get included in thestudy were that these patients should have bestcorrected visual acuity (BCVA) of equal to orbetter than 6/18 and they should be able toperform visual field test. Patients having smallpupil and significant media haze where OCT wasnot possible were excluded from the study.After obtaining the verbal consent and completeocular examination the patients were subjectedto 24-2 SITA standard test on HVF withundilated pupils. Each patient underwent fastRNFL thickness (3.4) scan (with resolution of 256scan points) under dilation in the same sitting.Average retinal sensitivity of superior andinferior hemifields was compared with averageRNFL thickness of the inferior and the superiorfields respectively.Statistical analyses were done with SPSS (Version16.0; SPSS, Chicago). Pearson’s linear regressionanalysis was used to correlate the retinalsensitivity of both the hemifields on Humphrey’sautomated perimetry with the average retinalnerve fibre layer thickness in Optical CoherenceTomography of the both quadrants respectively.Pearson correlation coefficients with absolutevalues equal to or greater than 0.5 suggesting astrong association with p

GLAUCOMA SESSION-II267evaluate the strength and pattern of therelationship between VF sensitivity and RNFLthickness as measured by Stratus OCT found outthat in POAG eyes, RNFL and both MS (r = 0.733)and MD (r= 0.718) correlated significantly. Linearregression plots of MS or MD against RNFLthickness demonstrated a fit curvilinearregression model (R2: 0.6947 and 0.723) in thePOAG group. Miglior S et al in a prospectivestudy to define the relationship between retinallight sensitivity and peripapillary RNFLthickness as measured using the Stratus OCT1. Quigley HA. Number of people with glaucomaworldwide. Br. J. Ophthalmol. 1996;80:389-93.2. Ramakrishan R, Nirmalan PK, Krishnadas R,Thulasiraj RD, Tielsch JM, Katz J, et al . Glaucoma ina Rural Population of Southern India, The AravindComprehensive Eye Survey. Ophthalmology 2003;110:1484-90.3. Jacob A, Thomas R, Koshy SP, Braganza A, MuliyilJ. Prevalence of primary glaucoma in an urbanSouth Indian population. Indian J Ophthalmol 1998;46:81-6.4. Shields’ Textbook of Glaucoma. Fifth Edition. R.Rand Allingham, Karim F. Damji, SharonFreedman, Sayoko E. Moroi, George Shafranov.Lippincot Williams and Wilkins. 2005.5. A. F. Fercher, K. Mengedoht, W. Werner, "Eyelength measurement by interferometry withpartially coherent light," Optics Letters vol. 13, no. 3,Central Corneal thickness is known toinfluence the IOP measurement with theGoldmann Applanation tonometer. Ehlers et.al. 1found that GAT most accurately reflected trueintracameral IOP when CCT was 520 um. TheOcular Hypertension Treatment Study (OHTS)found that subjects with lower corneal thicknessand ocular hypertension has a higher risk ofdeveloping glaucoma. 2 Lower corneal thicknesshas been thought to be a risk factor in thedevelopment of glaucoma. Lower cornealthickness has also been associated with moresevere visual field loss on initial examination asReferencesfound a statistically significant, age-adjustedcorrelation between function and structure inmost sectors both using the decibel (logarithmicregression analysis r2 0.24 to 0.61, P < .001), andthe unlogged scale (r 2 0.37 to 0.53, P < .001 in bothlinear and logarithmic regression analyses)Based on the result of this study, there is a directcorrelation between the visual field loss inautomated perimetry and the RNFL loss in OCT.Therefore OCT can be considered as anindependent tool for monitoring the progressionof glaucoma.pp. 186-188, 1988. (Available from URL:www.opticsinfobase.org; accessed on 28th ofSeptember 2007).6. Kanamori A, Nakamura M, Escano MF, Seya R,Maeda H, Negi A. Evaluation of the glaucomatousdamage on retinal nerve fiber layer thicknessmeasured by optical coherence tomography. Am J.Ophthalmol. 2003;135:513-20.7. Ajtony C, Balla Z, Somoskeoy S, Kovacs B.Relationship between visual field sensitivity andretinal nerve fiber layer thickness as measured byoptical coherence tomography. Invest OphthalmolVis Sci. 2007;48:258-63.8. Miglior S, Riva I, Guareschi M, Di Matteo F,Romanazzi F, Buffagni L, Rulli E. Retinal sensitivityand retinal nerve fiber layer thickness measured byoptical coherence tomography in glaucoma. Am JOphthalmol. 2007;144:733-40.The Influence of Central Corneal Thickness in PrimaryOpen Angle GlaucomaDr. Monica Yadav, Dr. Ajit Kumar Sinha, Dr. Nikhil Khanorkar, Dr. Krishna Bhojwani,Dr. Vinay Kumar Nangia(Presenting Author: Dr. Monica Yadav)compared to those with greater central cornealthickness. 3 Similarly in another study Jonas et.al. 4 found that when referred to hospitals,patients with POAG have more advancedglaucomatous optic nerve damage if the corneais relatively thin than if the corneal thickness isgreater. It was the purpose of this study toascertain the influence or association of centralcorneal thickness on the severity of primary openangle glaucoma status at presentation.Materials and MethodsIn a clinic based study 164 eyes of 87 subjects

GLAUCOMA SESSION-II269normal disc, and elevated undetected IOP due toa low CCT the patient may progress to developglaucoma, or that in the early stages of glaucoma,with early disc and retinal nerve fiber changes, anormal or low IOP due to a low CCT may notresult in significant clinical suspicion leading toprogressive glaucomatous damage, with thepatient presenting with greater degree of opticdisc and visual field loss to the clinic. There is stillno definite evidence to state that lower CCT may1. Ehlers N, Bramsen T, Sperling S. Applanationtonometry and central corneal thickness. ActaOphthalmol (Copehn) 1975;53:34-43.2. Gordon MO, Beiser JA, Brandt JD, et. Al. TheOcular Hypertension Treatment Study: baselinefactors that predict the onset of primary open angleglaucoma. Arch Ophthalmol 2002;120:714-20.(discussion 829-30).3. Herndon LW, Weizer JS, Stinnet SS. Central cornealthickness as a risk factor for advanced glaucomadamage. Arch Ophthalmol. 2004;122:17-21.4. Jonas J, Stroux A, Velten I, et. Al. Central cornealReferencespredispose to greater glaucomatous damagethrough an anatomic relationship in structure ofthe optic disc, making it more predisposed todeveloping of glaucomatous damage or itsprogression. It may be prudent that in patientswith suspect discs, and in those with a familyhistory of glaucoma, or other features that areassociated with development of glaucoma,measurement of CCT may be an importantclinical indicator.thickness correlated with glaucoma damage andrate of progression. Invest Ophthalmol Vis Sci.2005;46:1269-74.5. Ehlers N, Hansen FK, Aasved H. Biometriccorrelations of corneal thickness. Acta ophthalmol(Copenh) 1975;53:652-9.6. Ehlers N, Hanssen FK. Central corneal thickness inlow-tension glaucoma. Acta Ophthalmol (Copenh)1974;52:740-6.7. Argus WA. Ocular Hypertension and centralcorneal thickness. Ophthalmology 1995;102:1810-2.AUTHORS’S PROFILE:DR. MAITHILI KULKARNI: M.B.B.S. (’98), N.K.P. Salve Institute of Medical Sciences, NagpurUniversity; D.O.M.S. (2003), Terna Institute of Medical Sciences, Mumbai University;Fellowship in Glaucoma and Cataract (2006), Suraj Eye Institute, Nagpur. Senior clinical fellow(2007), Suraj Eye Institute. Presently, working as research associate at Suraj Eye Institute,NagpurE-mail: maithili1kulkarni@yahoo.com.Regional Distribution of The Normal Retinal Nerve FiberLayer in an Adult Population in Central India. The Central IndiaEye And Medical StudyDr. Maithili Kulkarni, Dr. Monica Yadav, Dr. Vinay Kumar Nangia,Dr. Krishna Bhojwani, Dr. Jost Jonas(Presenting Author: Dr. Maithili Kulkarni)The retinal nerve fiber layer is the site ofglaucomatous damage. The normaldistribution of the retinal nerve fiber layer formsa baseline. This may be assessed by thestereoscopic clinical viewing of the optic disc,and by fundus photography. The neuroretinalrim which is the intraoptic disc representation ofthe retinal nerve fibers is usually broadest in theinferior disc region, followed by the superior discregion, the nasal disc area and finally theTemporal disc region. 1 The retinal nerve fiberbundles are known to be significantly more oftenbetter detectable in the inferotemporal regionthan in the superotemporal region. 2 Thecharacteristic double hump pattern with thenerve fiber layer thickest inferiorly, thensuperiorly, then nasally and thinnest temporallyhas also been demonstrated in histologicalstudies of the normal optic disc. 3 Newertechnologies that image the optic disc and theretinal nerve fiber layer also enable us to studythe normal distribution. 4,5,6 Loss of the retinal

270 AIOC 2009 PROCEEDINGS-Table-1: Showing General Parameters and RNFLT Thickness MeasurementsGeneral parameters Values. Mean and SD RNFLT Segments Values Mean and SD (mm)Age (yrs) 46.70±12.79 RNFLT Global 0.25±0.07Sph. Equ. (D) -0.18±1.43 RNFLT Temp Sup 0.28±0.09Axial Length (mm) 22.66±0.84 RNFLT Temp Inf 0.28±0.09IOP (mmHg) 13.72±2.86 RNFLT Temporal 0.08±0.02nerve fiber layer is an important sign ofglaucomatous disc damage and may be a veryinitial preperimetric presentation. The RNFL isalso important for the follow up of glaucomasubjects and may provide a benchmark to assessthe management of such patients. Knowledge ofthe normal distribution may therefore be ofimportance. It was the purpose of this study todetermine the normal distribution of the retinalnerve fiber layer in a population-based study –The Central India Eye and Medical Study.Materials and MethodsThe Central India Eye and Medical Study(CIEMS) is a population based study conductedin a rural area about 40 kms from Nagpur. In aninterim analysis, 3393 of 4291 subjects (responserate 79.1%) aged 30 and above were examined.The medical ethics committee of the Suraj EyeInstitute had approved the study protocol and allparticipants had given informed consentaccording to the declaration of Helsinki. Entirepopulation in the villages included in the studywas enumerated. The ophthalmic evaluationincluded visual acuity using ETDRS charts,refraction, slit lamp biomicroscopy, applanationtonometry, gonioscopy, biometry, pachymetry,fundus examination and photography afterdilatation, and confocal scanning laserophthalmoscopy with the Heidelberg RetinaTomography II (software V 3). Medicalevaluation included pulse, blood pressure,height, weight, ECG, X-ray, complete bloodcount and serum and blood biochemistry,including kidney function tests. Intraocularpressure was recorded with the slit lampmounted Goldmann applanation tonometer. Thecorneal thickness was measured usingultrasound pachymetry. A total of 1797 subjectswere included in the present investigation. Theoptic disc of one randomized eye of includedRNFLT Nas Sup 0.35±0.10RNFLT Nas Inf 0.35±0.11RNFLT Nasal 0.28±0.10subjects was measured by confocal scanning lasertomography. The contour line was drawn bykeeping the image of the optic disc adjacent to thescanning laser image. The instrument automaticallygenerates several optic disc parametersincluding disc size, cup area and neuroretinal rimarea. Aphakes, pseudophakes and those withIOP greater than 21 mm Hg were excluded fromanalysis. The mean age of subjects included in thestudy was 46.70 ±12.79 yrs. (range 30-95. Therewere 808 males. The mean IOP was 13.72±2.86mm.Hg. Themeanopticdiscareawas2.23±0.47mm2.ResultsThe retinal nerve fiber layer thickness wasdetermined as: Mean global retinal nerve fiberlayer 0.25±0.07mm, Supero temporal,0.28±0.09mm, supero nasal, 0.35±0.10mm, nasal0.28±0.10 mm, infero nasal, 0.36±0.11mm, inferotemporal0.26±0.09, and temporal 0.08±0.02mm.Maximum nerve fiber layer thickness was seen inthe infero nasal quadrant followed by the superonasal segment. The bipolar distribution of RNFLwas seen with the superior and inferior poleshaving greater RNFL thickness compared to thenasal and temporal segments.DiscussionThe distribution of the retinal nerve fiber layer isan important normative parameter, speciallysince the RNFL is an important component ofglaucomatous damage. Using the Confocal laserscanning ophthalmoscope using the HRT II(Software V 3) the regional distribution of theretinal nerve fiber layer was determined in apopulation based study the Central India Eyeand Medical Study. The infero nasal RNFLT asmeasured by confocal scanning lasertomography at the optic disc border was foundto be the maximum followed by the supero nasalRNFLT, the supero temporal RNFLT and infero

GLAUCOMA SESSION-II271nasal RNFLT. These segments are according tothe division of the optic disc on the HRT. Thebipolar distribution with the inferior pole and thesuperior pole having the maximum retinal nervefibers is borne out by this investigation in a largenumber of subjects. The bipolar distributioncorrelated well with previous studies done byvarious methods including histological studies,and those done by using the confocal scanning1. Jonas JB, Gusek GC, Naumann GOH. Optic disc,cup and neuroretinal rim size, configuration andcorrelations in normal eyes. Invest. Ophthalmol. Vis.Sci. 1988;29:1151-8.2. Jonas JB, Nguyen NX, and Naumann GOH. Theretinal nerve fiber layer in normal eyes.Ophthalmology. 1989;96:627-32.3. Dichtl A, Jonas J, Naumann GOH. Retinal nervefiber layer thickness in human eyes. Graefe’s ArchClin Exp Ophthalmol. 1999;237:474-9.4. Burk ROW, Rohrschneider K, Takamoto T, VolckerHE, Schwartrz B (1993). Laser scanning tomographyand stereophotogrammetry in three-dimensionalTrabeculectomy is the universally acceptedfiltering surgery for treatment of Glaucoma.In guarded filtering surgery the partial thicknessscleral flap, which is closed with help of one ormore sutures, guards the full thickness scleralwindow underneath, through which the aqueoushumor filters out to subconjunctival space.Tightness of suture has effect on the amount ofaqueous filtering out of the eye and hence theIntraocular pressure. Laser suturolysis orreleasable sutures helps to improve filtration if itis inadequate. Use of Antimetabolites has distinctadvantage to prevent failure of trabeculectomy.There is no universal agreement about the size ofthe scleral flap. Also its effect on outcome of theIOP control has not been published. Weprospectively studied two groups of patientsundergoing trabeculectomy with different flapsize and compared the outcome.To study the effect of size of Scleral flap in Phacotrabeculectomy on outcome of intraocularPressure (IOP).Referenceslaser ophthalmoscope, optical coherencetomography and laser polarimetry. 3,4,5,6 Data fromlarge studies may enable us to detect the earliestloss from a specific segment of the optic disc andretinal nerve fiber layer. This may allow evenearlier detection of glaucomatous nerve fiber loss.A significant negative influence of age, axiallength and systolic blood pressure was seen onthe RNFLT.optic disc analysis. Graefe’s Arch Clin Exp Ophthalmol1993;231:193-8.5. Schuman JS, Hee MR, Puliafito CA, Wong C, Pedut-Kloizman T, Lin CP, Hetzmark E, Izatt JA SwansonEA, Fujimoto JG. Quantification of nerve fiber layerthickness in normal and glaucomatous eyes usingoptical coherence tomography: a pilot study. ArchOphthalmol 113:586-96.6. Weinreb RN, Shakiba S, Zangwill L. Scanning laserpolarimetry to measure the nerve fiber layer ofnormal and glaucomatous eyes. Am J Ophthalmol.1995;119:627-36.Effect of Scleral Flap Size on Outcome of TrabeculectomyDr. Jansari Piyush Himatlal(Presenting Author: Dr. Jansari Piyush Himatlal)Materials and Methods57 consecutive patients underwent Phacotrabeculectomy, and prospectively studied forpostoperative IOP control. These patientsconsisted of Primary open or closed angleglaucoma along with cataract that requiredcombined surgery. In patients (group A) whoselected foldable intraocular lens, triangulartrabeculectomy flap was sized 3x3x3 mm. Inpatients (group B) opting for nonfoldableintraocular lens, triangular flap was sized 5x4x4mm. In all patients standard stop and chopphacoemulsification technique was performedfollowed by standard trabeculectomy of abovementioned flap sizes and 2mmx 1mm scleralwindow followed by surgical iridectomy. Thescleral flap was sutured with single apical sutureof 10-0 nylon. Conjunctiva was closed with twowing sutures of 8-0 vicryl. Postoperatively, theywere followed-up on day one, weeks one, twoand six and three monthly thereafter. Ifintraocular pressure was above 20 mmHg in first