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Contents 

OPTICS/ REFRACTION/ CONTACT LENS 

Refractive Status of Eyes Treated for Retinopathy of Prematurity (ROP) with 

Avastin and/or Laser ....................................................................................... 403 

Dr. Rohan Chauhan, Dr. Alay S Banker, Dr. Usman Memon, Dr. Chatura Hutheesing, 

Dr. Kinnari Thakkar 

Accommodation Amplitude and Lag Study in Relation to Different 

Variables............................................................................................................ 407 

Prof. R Maheshwari, Dr. Ankita Phougat, Prof. R R Sukul 

To Study the Effect of Advanced Overnight Ortho-Keratology as a Corrective 

Modality for Myopia...........................................................................................411 

Dr. (Col) Ashish Saksena, Dr. (Maj) Shrikant Waika 

Evaluating The Efficacy of Orthokeratology Lenses in Myopia Regression... - 

.............................................................................................................................415 

Dr. Kirti Singh, Dr. Abhishek Goel, Dr. Ritu Arora 

Anterior Chamber Depth Changes in Accommodation Measured with Optical 

Coherence Tomography....................................................................................417 

Dr. Mukesh Taneja, Dr. Debarun Dutta, Dr. Tamal Chakraborty, Dr. Preetam Kumar, 

Dr. Virender Sangwan 

Role of Optical Coherance Tomography in Boston Ocular Surface Prosthesis 

Fitting................................................................................................................. 420 

Dr. Varsha Rathi, Dr. Preeji Mandathara Sudharrman, Dr. Srikanth D, Dr. Virender 

Sangwan S

Anton Chekhov (1860-1904): 

He studied medicine, but was 

famous for his plays. His one 

eye was myopic & the other 

hyperopic. He lost his RE due 

to HZO. 

Degas Edgar (1834-1907): 

A French painter, is best known for his ballerina paintings. 

In 1880s, when his eyesight began to fail from myopic 

degeneration, Degas started working with two new media 

(Sculpture & pastel) that did not require intense visual acuity. 

He was permanently blind when he was 63. 

Benjamin Franklin (1706-90): 

First invented the bifocal lens.

Optics/Refraction/Contact Lens Free Papers 

OPTICS/ REFRACTION/ CONTACT LENS 

Chairman: Dr. Shreekant Kelkar B; Co-Chairman: Dr. Deepak Mehta C 

Convenor: Dr. Amit Tarafder; Moderator: Dr. R R Battu 

Dr. ROHAN RAMCHANDRA CHAUHAN: MBBS (2005), B J Medical 

College, Ahmedabad; DO (2007), Smt. N H L Municipal Medical College, 

Ahmedabad; Long Term Fellowship in Vitreo Retinal Diseases, Surgery & 

Intra Ocular Imflammation (2007-09). Presently, Associate Vitreo-Retinal 

Surgeon, Banker’s Retina Clinic & Laser Centre, Ahmedabad. 

E-mail: rohan_28782@yahoo.co.in; Contact: 9825203022 

Refractive Status of Eyes Treated for Retinopathy 

of Prematurity (ROP) with Avastin and/or Laser 

Dr. Rohan Chauhan, Dr. Alay S Banker, Dr. Usman Memon, Dr. Chatura 

Hutheesing, Dr. Kinnari Thakkar 

Retinopathy of prematurity (ROP) is a leading cause of childhood blindness 

worldwide. Treatment for ROP has evolved from the past from more 

destructive (cryo therapy) to lesser destructive (laser therapy) peripheral 

retinal ablation. Although these ablative treatments reduce the incidence of 

blindness by 25% in infants with severe disease, visual acuity post-treatment 

remained considerably impaired. 1 

The role of vascular endothelial growth factor (VEGF) in the pathogenesis of 

ROP has been identified. It is believed that exposure to high levels of oxygen 

during the neonatal period leads to obliteration of vessels. Vaso-obliteration 

leads to ischemia which further leads to the release of vascular growth 

factors and neovascularization. 2 VEGF increases permeability of vessels 3 

and promotes endothelial cell proliferation. 4 Transcription of VEGF mRNA 

increases with hypoxia and has been identified to play a vital role in retinal 

angiogenesis. 5 Recent studies have identified that insulin-like growth factor 

1 (IGF-1) plays a permissive role—in its absence VEGF is unlikely to fully 

stimulate vessel growth. 1 If evidence-based data supports early findings, 

the use of Avastin may be recommended without the need for ablative laser 

therapy and before retinal detachment develops. 

To evaluate refractive status of eyes with ROP treated with laser and/or avastin. 

MATERIALS AND METHODS 

Prospective, Nonrandomized, Non comparative case series. 

The procedure and the side effects of atropine were explained in details to the 

patient’s parents. Informed consent was obtained from the parents prior to the 

study with clear guidelines on the procedures and tests involved. 

403

69th AIOC Proceedings, Ahmedabad 2011 

Atropine was advised three times a day for 3 days prior to retinoscopy. 

Thereafter retinoscopy of the patient was performed on the fourth day. Out 

of 29 patients, only 1 patient had to be examined under general anaesthesia 

due to the hyperactivity and lack of co-operation of the patient. Based on 

cycloplegic retinoscopy, the patient was prescribed glasses depending on 

degree of refractive error. The refraction values of the patient’s parents were 

also noted. All patients were examined and evaluated by single optometrist. 

57 eyes of 29 patients were being evaluated in the study. 26 eyes were treated 

with laser, 26 eyes with only avastin and 5 eyes, with both laser and avastin. 

All patients underwent atropinized refractive evaluation under sedation. 

Based on cycloplegic retinoscopy with streak retinoscope, the patients were 

prescribed glasses depending on his/her age and degree of refractive error. 

RESULTS 

26 Avastin treated eyes at the mean age of 1 year showed a mean spherical 

equivalent (MSE) of -3.087 DS and -0.920 DC. 6/26 eyes were high myopic 

(-10.50 DS). 26 eyes in laser group at the mean age of 2 years showed a MSE of 

-2.058 DS and -1.00 DC. 3/26 eyes were high myopic (-13.16 DS). 5 eyes treated 

with laser and avastin at the mean age of 2 years showed MSE -2.30 DS and 

-1.00 DC. 

Amongst the avastin treated patients, 18/26 eyes were myopic and 7 were 

hyperopic with a mean spherical refractive error to be -3.087DS. 22/26 eyes 

were astigmatic with a mean astigmatic error of -0.920D. Amongst the laser 

treated patients in study, 12/26 eyes were myopic and 12 were hyperopic 

with a mean spherical refractive error as -2.058DS. 23/26 eyes were astigmatic 

with a mean astigmatic error as -1.00D. Amongst the patients treated with 

laser as well as avastin in study, 3/5 eyes were myopic and 2 were hyperopic 

with a mean spherical refractive error of -2.30 DS. 4/5 eyes were astigmatic 

with a mean astigmatic error of -1.00 D. Therefore myopia was seen to be the 

most predominant refractive error amongst all the 3 sub-groups of patients 

– avastin treated, laser treated as well as both, laser and avastin treated. It 

was found that 6/26 eyes in the avastin treated group of patients were highly 

myopic (that is, greater than -8.00 DS). If we exclude those highly myopic eyes 

from the study, the mean spherical refractive error was found to be -0.8625 

DS. Similarly, in the laser treated group of patients, 3/26 eyes were found to 

be highly myopic. On excluding those highly myopic eyes, the mean spherical 

refractive error of the patients treated with laser was found to be -0.609 DS. 

In this study, the mean age on retinoscopy of the patients treated with avastin 

is 1 year. Whereas the mean age on retinoscopy of the patients treated with 

laser photocoagulation is 2 years. As these two groups are incomparable 

due to the vast difference in the mean age group of the patients, for better 

404


comparison, the patients whose age on retinoscopy was equal to or greater 

than 3.5 years where excluded. Thereby the mean age on retinoscopy of 

the patients treated with laser photocoagulation was 1 year 4 months. On 

excluding the above mentioned patients, the mean spherical refractive error of 

the laser treated patients was found to be -1.579 DS instead of -2.058 DS and the 

mean astigmatic error was found to be -0.96 D. The mean spherical refractive 

error of the avastin treated patients was found to be -3.087 DS and the mean 

astigmatic error was found to be -0.920 D. 

DISCUSSION 

Myopia 

Correlating to this, simple cross-sectional studies comparing premature with 

full-term infants have revealed that premature infants are more prone to 

development of myopia from an early age and may remain myopic later on in 

childhood and adolescence. This is known as myopia of prematurity, 6,7,8,9,10,11 

and it can continue to increase up to 2 years of age. 12,13 

Hypermetropia 

Which can be supported by a study carried out by Anne cook et al 5 which 

states that there is consistently less hypermetropia noted at term in premature 

infants, with or without ROP, when compared with full-term infants. By 3 

months’ corrected age, this difference is much less in those premature eyes 

without ROP. Eyes with ROP, however, still maintain less hypermetropia than 

full-term eyes by the end of 3 months’ corrected age. 15,16 

A second study of infants with and without ROP reported a similar prevalence 

of astigmatism > 1.00 D in 652 infants and in 551 infants, with all refractions 

during the first week of life. 17 Some studies have documented a decreasing 

prevalence of astigmatism between infancy and childhood in preterm 

infants. 18,19,20,21 In contrast, a recent study, in which 293 low birth weight (< 1701 

g) children were refracted at six months corrected age and again at age 10 to 

12 years, reported little change in astigmatism power or axis over this long 

period, with 75% of children showing a change in cylinder power of no more 

than 0.75 D.6 

Avastin being a new mode of treatment for ROP, not many studies regarding 

the refractive outcomes of ROP patients treated with avastin have been done. 

Hence, this study can be considered as first of its kind. This can be correlated 

with a study carried out by Dhawan A et al. 21 which resulted in a mean 

spherical equivalent of -4.71 D at follow up of 1 year after laser treatment. 

Myopia was seen in 80.43% of 184 eyes in this study. Another study that can be 

correlated is the one in which the mean spherical equivalent values obtained 

as -3.87 D in patients with age of 7 years or more in a study carried out by Yang 

405


CS et al. 22 A study by Yang CS et al showed that out of 60 laser treated eyes, 46 

eyes (77.0%) were myopic, the overall mean spherical equivalent was -3.87D. 

Anisometropia (>/= 1,50 D) was also noted in 14 patients (46.7%). Strabismus 

was present in 4 patients (30%). Davitt BV et al. 23 proved that by the age of 

3 years, nearly 43% of eyes treated at high risk prethreshold ROP developed 

astigmatism of >or= 1.00D and nearly 20% had astigmatism of >or= 2.00 D. 

Presence of astigmatism was not influenced by timing of treatment of acute 

phase ROP or by characteristics of acute phase or cicatricial ROP. 

Myopia was found to be the predominant refractive error in the ROP population 

at the clinic, irrespective of the treatment group and with no correlation with 

the family history of myopia. 

REFERENCES 

1. Chen J, Smith LE. Retinopathy of prematurity. Angiogenesis. 2007;10:133–40. 

2. Patz A. Clinical and experimental studies on retinal neovascularization.XXXIX 

Edward Jackson Memorial Lecture. Am J Ophthalmol. 1982;94:715–43. 

3. Senger DR, Galli SJ, Dvorak AM, Perruzzi CA, Harvey VS, Dvorak HF. Tumor cells 

secrete a vascular permeability factor that promotes accumulation of ascites fluid. 

Science. 1983;219:983–5. 

4. Leung DW, Cachianes G, Kuang WJ, Goeddel DV, Ferrara N. Vascular endothelial 

growth factor is a secreted angiogenic mitogen. Science. 1989;246:1306–9. 

5. Aiello LP, Northrup JM, Keyt BA, Takagi H, Iwamoto MA. Hypoxic regulation of 

vascular endothelial growth factor in retinal cells. Arch Ophthalmol. 1995;113:1538– 

44. 

6. O’Connor A, Stephenson T, Johnson A, et al. Long term ophthalmic outcome of low 

birth weight children with and without retinopathy of prematurity. Paediatrics. 

2002;109:12–8. 

7. Fledelius HC. Myopia of prematurity: changes during adolescence. Doc Ophthalmol 

Proc Series. 1981;28:63–9. 

8. Hungerford J, Stewart A, Hope P. Ocular sequelae of preterm birth and their 

relation to ultrasound evidence of cerebral damage. Br J Ophthalmol. 1986;70:463–8. 

9. Fledelius HC. Pre-term delivery and subsequent ocular development: a 7–10 year 

follow up of children screened for ROP 1982–4. Acta Ophthalmol Scand. 1996;74:297– 

300. 

10. Birge H. Myopia caused by prematurity. Trans Am Ophthalmol Soc 1955;292–8. 

11. Gordon RA. Donzis PB. Myopia associated with retinopathy of prematurity. 

Ophthalmology 1986;93:1593–8. 

12. Page J, Schneeweiss S, Whyte H, Harvey P. Ocular sequelae in premature infants. 

Paediatrics. 1993;92:787–90. 

13. Gallo JE, Fagerholm P. Low-grade myopia in children with regressed retinopathy 

of prematurity. Acta Ophthalmol 1993;71:519–23. 

406


14. Mayer DL, Hansen RM, Moore BD, Kim S, Fulton AB. Cycloplegicrefractions in 

healthy children ages 1 through 48 months. Arch Ophthalmol. 2001;119:1625–8. 

15. Quinn G, Dobson V, Kivlin J et al. The Cryo-ROP Group.Prevalence of myopia 

between 3 months and 5 1⁄2 years in premature infants withand without ROP. 

Ophthalmology. 1998;105:1292–1300. 

16. Varughese S, Varghese RM, Gupta N, et al. Refractive error at birth and its relation 

to gestational age. Curr Eye Res. 2005;30:423–8. 

17. Saunders KJ, McCulloch DL, Shepherd AJ, Wilkinson AG. Emmetropisation 

following preterm birth. Br J Ophthalmol. 2002;86:1035–40. 

18. Larsson EK, Holmström GE. Development of astigmatism and anisometropia in 

preterm children during the first 10 years of life: a population-based study. Arch 

Ophthalmol. 2006;124:1608–14. 

19. O’Connor AR, Stephenson TJ, Johnson A, et al. Change of refractive state and eye 

size in children of birth weight less than 1701g. Br J Ophthalmol. 2006;90:456–60. 

20. Holmström G , el Azazi M, Kugelberg U. Ophthalmological long term follow up 

of preterm infants: a population based, prospective study of the refraction and its 

development. Br J Ophthalmol 1998;82:1265–71. 

21. Dhawan A, Dogra M, Vinekar A, Gupta A, Dutta S. Structural sequelae and 

refractive outcome after successful laser treatment for threshold retinopathy of 

prematurity. J Pediatr Ophthalmol Strabismus. 2008;45:356-61. 

22. Yang CS, Wang AG, Sung CS, Hsu WM, Lee FL, Lee SM. Long term visual outcomes 

of laser-treated threshold retinopathy of Prematurity: a study of refractive status 

at 7 years. Eye (Lond). 2010;24:14-20. Epub 2009 Apr 3. 

23. Davitt BV, Dobson V, Quinn GE, Hardy RJ, Tung B, Good WV; Early Treatment 

for Retinopathy of Prematurity Cooperative Group. Astigmatism in the Early 

Treatment of Retinopathy Of Prematurity Study: findings to 3 years of age. 

Ophthalmology. 2009116:332-9. Epub 2008 Dec 16. 

Accommodation Amplitude and Lag Study in 

Relation to Different Variables 

Prof. R Maheshwari, Dr. Ankita Phougat, Prof. R R Sukul 

To evaluate amplitude (AA) and lag (AL) of accommodation with respect to 

ametropia, emmetropia and amblyopia. 

To study lens thickness (LT), anterior chamber depth (ACD) and axial length 

(AxL) changes during accommodation. 

Accommodation is the process by which vertebrate eye changes refractive 

power to maintain a clear image (focus) of an object as its distance from eye 

changes. The word accommodation was given by Burrow (1841). 1 The functional 

significance of active accommodation is evident from the inconvenience that 

results from its gradual age-related loss in presbyopia, manifests earliest in 

407


hyperopes and in emmetropes at about 40 years of age, when the accommodative 

reserve becomes insufficient to focus on near objects. However, the loss of 

accommodative amplitude begins early in life 2 and progresses to about age 

55, when accommodation, as measured objectively, is completely lost. 3 Near 

work has been claimed to induce myopia and accommodation loss has been 

considered a risk factor for amblyopia. This study is undertaken to see the 

variation in accommodation with refractive errors, age and amblyopia. Also, 

various biometric changes with accommodation have been studied using 

A-scan. 


75 patients in the age group of 11-30yrs were included in the study after taking 

informed consent. The assessment of selected patients included a detailed 

history, general and ocular examination, including biomicroscopy and direct 

ophthalmoscopy. All patients underwent a wet retinoscopy followed by dry 

retinoscopy a week later. Emmetropes, ammetropes and amblyopes without 

any ocular pathology (normal anterior and posterior segments) or systemic 

illness presenting to us in the OPD were selected. 

Measurements included AA using method of spheres (MOS) and RAF rule, AL 

using dynamic retinoscopy; LT, ACD and AxL changes during accommodation 

using A-scan. Eyes were divided based on: age (11-15,15-20,20-25 and 25-30), 

refractive error (emmetropia, myopia4,hypermetropia4), 

presence or absence of amblyopia. Accommodation lag, amplitudes; LT, ACD 

and AxL changes during accommodation, were compared in different groups. 

Also, two methods of measuring accommodation i.e. the RAF rule and MOS 

were compared. 

RESULTS 

Mean of accommodation amplitude(AA) by RAF rule for myopes4D 

was 11.37D, hypermetropes 4 is 9D. Corrected low myopes showed a significantly higher 

amplitude of accommodation compared to emmetropes (p< 0.005) and 

hypermetropes (p


RAF AA was 9.82. AA values by MOS were significantly lower compared to 

RAF rule (p


DISCUSSION 

Our study showed that AA was highest in myopes followed by emmetropes 

and least in hypermetropes. Similar results have been initially obtained by 

McBrien et al. 4 Schaeffel et al 5 have shown that refractive errors do not affect 

the dynamics of natural accommodation. AA is highest in myopes and lowest 

in hypermetropes till the age of 44yrs after that no difference exists (Lekha 

Mary Abraham et al). 6 

In regards to other methodology, AA by MOS showed lower values 

compared to RAF. The minus lens technique has found reduced amplitudes 

of accommodation compared to the far to near technique, possibly due to 

the apparent minification of the image; 7 the smaller image interpreted as 

being further away may stimulate less effort to accommodate. The plus lens 

technique used to neutralize the reduced accommodative effort seen with 

dynamic retinoscopy is thought to reduce the accommodative response 

to blur and simultaneously relax the subject’s accommodation during 

testing (Rosenfield M et al). 8 Leat and Gargon (1996) 9 reported that lags of 

accommodation increases with an increase in age. Lens thickness increases 

and anterior chamber depth decreases during accommodation for near 

(Matthias Bolz, Ana Prinz, Wolfgang Drexler and Oliver Findl, 2007). 10 In a 

study of accommodation in amblyopia (Goel et al 1981) 11 it has been observed 

that accommodation is considerably less in the amplyopic eye than the nonamblyopic 

and control eyes similar to our findings of low AA in amblyopes. 

Duane 12 has shown that AA falls with age but fall not significant in 10-20yr 

age group. Edward A. H. Mallen et al 13 reported that Axial length increased in 

both emmetropic and myopic subjects during short periods of accommodative 

stimulation. Greater transient increases in axial length were observed in 

myopic than in emmetropic subjects. 

Accommodation is highest in corrected low myopes followed by emmetropes 

and lowest in corrected hypermetropes. It decreases with increasing age 

but the decrease is not significant in 11-20yr. Amblyopes have low AA and 

higher AL compared to non-amblyopes. AC depth decreases while LT and 

AxL increases during accommodation and the increase is significantly more 

in myopes(especially in 10-20yr age group). 

REFERENCES 

1. Burrow.Beitr.2 Physiologieu.Physik d. menseh. Auges. Berlin, 94(1841). 

2. Duane A. Normal values of the accommodation at all ages. J Am Med Assoc 1912; 

59:1010–3; also Trans Sect Ophthalmol AMA 1912;383–91. 

3. Hamasaki D, Ong J, Marg E. The amplitude of accommodation in presbyopia. Am 

J Optom Arch Am Acad Optom 1956;33:3–14. 

410


4. Mc Brien NA, Millodot M. Amplitude of Accommodation and Refractive Error. 

Invest Ophthalmol Vis Sci 1986;27:1187-90. 

5. Schaeffel F, Wilhelm H, Zrenner E. Inter individual variability in the dynamics of 

natural accommodation in humans in relation to age and refractive errors. Journal 

of Physiol (Lond) 1993;461:301-20. 

6. Lekha Mary Abhram et al. Amplitude of Accommodation and its relation to 

refractive errors, IJO 2005;53:105-8. 

7. Rosenfield M, Cohen A: Repeatability of clinical measurements of the amplitude of 

accommodation. Ophthal Physiol Opt 1996;16:247–9. 

8. Rosenfield M, Portello J, Blustein G, Jangs C: Comparison of clinical techniques to 

assess the near accommodative response. Optom Vis Sci 1996;73:382–8. 

9. Leat SJ, Gargon JL. Accommodative response in children and young adults using 

dynamic retinoscopy. Ophthalmic Physiol Opt 1996;16:375-84. 

10. Matthias Bolz, Ana Prinz, Wolfgang Drexler and oliver findl. Linear relationship of 

refractive and biometric lenticular changes during accommodation in emmetropic 

and myopic eyes. British Journal Of Ophthalmology 2007;91:360-5. 

11. Goel, B.S., Maheshwari, R., and Saiduzzafar, H., Subjected for publication in Indian 

Journal of Ophthalmology, 1981. 

12. Duane A., Amer. Ophtlialmol 1922;5:865. 

13. Edward A.H. Mallen, Priti Kashyap and Karen H. Hampson. Transient axial 

length change during the accommodation response in young adults. Investigative 

Ophthalmology and Visual Science 2006;47:1251-4. 

To Study the Effect of Advanced Overnight 

Ortho-Keratology as a Corrective Modality for 

Myopia 

Dr. (Col) Ashish Saksena, Dr. (Maj) Shrikant Waika 

Orthokeratology is the temporary reduction of myopia achieved by reshaping 

the cornea with specially designed reverse geometry gas permeable 

Orthokeratology shaping lenses worn during sleep. It was first introduced in 

1960’s when few hard contact lens wearers reported improvement in vision after 

removal of their lenses. Gearge Jessen created the first Orthokeratology lens 

design from PMMA material. The early lenses were flat fitting with frequent 

decentration leading to significant with the rule corneal astigmatism. These 

lenses were not suitable for overnight wear. A series of lenses were needed 

each lens flattening the cornea a small amount until the desired results were 

attained. This took months to years to accomplish. The advent of space-age 

oxygen polymers, computer assisted lathes and technological advancements 

in corneal measuring and mapping has made it possible to reverse myopia in 

a matter of hours. 

411


Hence, modern Orthokeratology is called accelerated Orthokeratology. 

Accelerated Orthokeratology utilises reverse geomerty lens design made of 

high Dk material. These can be worn overnight and do not cause induced 

with the rule astigmatism and result in corneal sphericalisation. Reverse 

geometry lenses are fitted with a base curve flatter than the central corneal 

curvature. This exerts a positive pressure as a result of which the central 

corneal epithelium is thinned out, the sagittal corneal height is decreased 

which shortens the length of the eye reducing the corneal power resulting in 

correction of myopia. And evaluation of correction of myopia by accelerated 

advanced overnight Orthokeratology using third generation 5 curve reverse 

geometry corneal reshaping lens has been carried out in this study. 


710 eyes of 355 patients of Myopia with or without astigmatism underwent 

advanced overnight Orthokeratology using third generation 5 curve reverse 

geometry corneal reshaping lens. 

Inclusion Criteria 

• Age group between 7yrs to 52yrs. 

• Myopia (Spherical equivalent) upto -7.5D. 

Exclusion Criteria 

• Corneal dystrophies. 

• Dry eyes. 

• Any other associated ocular disease. 

• Any ocular surgery in the past. 

• Any refractive procedure in the past. 

• Any ocular surface pathology. 

Pretreatment and post treatment unaided visual acuity, Objective and 

Subjective refraction, slit lamp examination and corneal topography findings 

were recorded. Orthokeratology lens was selected based on flat K on corneal 

topography and placed on patient’s eye. Ideal fitting was confirmed using 

fluoroscein staining. Orthokeratology lens was removed after 8 hours. 

Improvement in unaided visual acuity was recorded which was an indicator 

of the correction of Myopia by advanced overnight Orthokeratology over a 

period of 8 hours. 

RESULTS 

710 eyes of 355 patients were included in this study. The youngest patient was 

7 years old and the oldest 52 years. There were 88 patients in the 7-12 year age 

412


group, 161 in the 13-20 years group and 106 in the 21-52 years group out of 

which 160 were males and 195 females. 300 eyes had simple myopia and 410 

had compound myopic astigmatism. 320 eyes had with the rule astigmatism 

ranging between -1.0D to -2.0D. 50 eyes had the same ranging between -2.0D to 

-3.0D and 10 eyes with -3.5D. 30 eyes had against the rule astigmatism varying 

between -0.5D to -1.0D. The spherical equivalent refraction was calculated 

and the effect of advanced overnight orthokeratology with 5 curve reverse 

geometry corneal reshaping lenses was assessed. 236 eyes with myopia 

(spherical equivalent) of up to -2.0D with pre-application unaided visual 

acuity between 6/9 to 6/18 achieved unaided vision of 6/6 after removal of 

the 5 curve reverse geometry orthokeratology lens after overnight wear for 7 

hours. These eyes had a complete reversal of myopia. 

Out of 266 eyes with myopia (spherical equivalent) ranging between -2.0D to 

-4.0D and pre-application unaided vision ranging between 6/60 to 6/24,148 

regained vision of 6/6 and 118 eyes a vision of 6/9 after removal of overnight 

applied lenses. 208 eyes in myopic range of -4.0D to -7.5D with unaided vision 

range 1/60 to 5/60 pre lens application achieved unaided visual range of 6/18 

to 6/12. There was more than 2 snellen line correction in every case. Some 

eyes showed improvement of upto 9 snellen lines. Statistical analysis showed 

that correction of myopia as reflected in improvement of visual acuity was 

statistically highly significant at p


were noticed in this study which is ongoing and will assess the safety of these 

lenses over a long term. 

Advanced overnight orthokeratology with 5 curve reverse geometry corneal 

reshaping lens corrects myopia rapidly and dramatically. It is very useful 

for patients who wish to be spectacle free to participate in contact sports 

like boxing or wrestling or those who work in dusty areas and cannot wear 

conventional contact lens. It is especially useful in professions like police, 

firemen and athletes. It is non-invasive and reversible and can be safely 

used in children unlike LASIK. The effect of orthokeratology in slowing the 

progression of myopia in children is also under evaluation at some centres. 

Orthokeratology is a viable option for correction and treatment of myopia ad 

should be a part of the armamentarium of all ophthalmologists. 

REFERENCES 

1. Kerns RL. Research in Orthokeratology. Part VIII: results, conclusions and 

discussion of techniques. J Am Optom Assoc 1978;49:308-14. 

2. Binder PS, May CH, Grant SC. An evaluation of Orthokeratology. Ophthalmology 

1980;87:729-44. 

3. Nichols JJ, Marsich MM, Nguyen M, et al. Overnight Orthokeratology optom Vis Sci 

2000;77:252-9. 

4. Swarbrick HA, Alharbi A. Overnight Orthokeratology induces central corneal 

epithelial thinning. Invest Ophthalmol Vis Sci 2001;42:S597. 

5. Mountford J. An analysis of the change in corneal shape and refractive error 

induced by accelerated orthokeratology. ICLC 1997;24:128-44. 

6. Lui W-O, Edwards MH. Orthokeratology in low myopia. Part 1: efficacy and 

predictability. Cont Lens Anterior Eye 2000;23:77-89. 

7. Wlodyga RJ, Bryla C. Corneal molding: the easy way. Contact Lens Spectrum 

1989;4:58-65. 

8. Johnson KL, Carney LG, Mountford JA, Collins MJ, Cluff S, Collins PK. Visual 

performance after overnight Orthokeratology. Cont Lens Anterior Eye. 2007;30:29- 

36. Epub 2007 Jan 9. 

9. Soni PS, Nguyen TT; XO Overnight Orthokeratology Study Group. Overnight 

Orthokeratology experience with XO material. Eye Contact Lens. 2006;32:39-45. 

10. Cheung SW, Cho P, Chui WS, Woo GC. Refractive error and visual acuity changes 

in Orthokeratology patients. Optom Vis Sci. 2007;84:410-6. 

11. Chan B, Cho P, Cheung SW Orthokeratology practice in children in a university 

clinic in Hong Kong. Clin Exp Optom. 2008;91453-60. Epub 2008 Mar 18. 

12. Walline JJ, Rah MJ, Jones LA The children’s Overnight Orthokeratology 

Investigation (COOKI) pilot study. Optom Vis Sci. 2004;81:407-13. 

13. Rah MJ, Jackson JM, Jones LA, Marsdem HJ, Bailey MD, Barr JT Overnight 

Orthokeratology: preliminary results of the Lenses and Overnight Orthokeratology 

(LOOK) stugy. Optom Vis Sci. 2002;79:598-605. 

414


14 Chan B, Cho P, Cheung SW. Orthokeratology practice in children in a university 

clinic in Hong Kong. Clin Exp Optom. 2008;91:453-60. Epub 2008 Mar 18. 

15. Watt KG,Swarbrick HA. Trends in Microbial keratitis associated with 

Orthokeratology. Eye Contact Lens. 2007;33:373-7; discussion 382. 

16. Shehadeh-Mashaour R, Segev F, Barequet IS, Ton Y, Garzozi HJ. Orthokeratology 

associated microbial keratitis. Eur J Opthalmol. 2009 Jan-Feb. 

Evaluating The Efficacy of Orthokeratology 

Lenses in Myopia Regression 

Dr. Kirti Singh, Dr. Abhishek Goel, Dr. Ritu Arora 

Orthokeratology is the temporary reduction of myopia by programmed 

application of specially designed contact lenses which reshapes the cornea. 

These reverse geometry lenses are made of highly oxygen transmissible Boston 

XO material with Dk value exceeding 140. The flat base curve applies gentle 

pressure to central corneal zone, causing sphericalisation of the prolate cornea 

leading to reduction of myopia. Tear film meniscus behind the contact lens 

hydraulically redistributes epithelial cells from the centre towards periphery. 

A secondary curve steeper than central base curve aids centration of lens. 

To evaluate efficacy of overnight wear of in mild to moderate myopia and 

evaluate its effect if any on the corneal health. 


Orthokeratology lenses (OK) were used in fifteen adults with myopia ranging 

from 1.75 - 5.75 D. The change in refractive status was assessed over a 3 month 

period. Corneal changes and health was evaluated by corneal thickness, 

topography, endothelial cell count and tear film status. Cases of astigmatism 

exceeding 1.5Ds, dry eyes, prior ocular surgery and retinal pathology were 

excluded. Initial overnight wear was supervised and subsequently patient 

was allowed to use the lens on his/her own. Follow up was fortnightly for 1 

month and monthly for 3 months. 

RESULTS 

An unaided visual acuity improvement of 6/6 was attained in 9 cases (60%) 

with a prior myopia of 2.75Ds (2.0Ds-3.5Ds) after an initial 8 hours of overnight 

OK lens wear. The mean improvement was 5.98 lines (4-7lines). Subsequent 

lens wear schedule given to these patients was daily wear of overnight 

orthokeratology lenses for 3weeks, followed by alternate overnight lens wear 

of 6-8 hours. This subgroup maintained unaided visual acuity of 6/6 over the 

entire follow up of 3 months. 

415


An unaided visual acuity improvement of 6/6 was attained in 5 cases (33.33%) 

having a pre lens prescription myopic refractive error of 4.95Ds (4.5-5.5Ds) 

after 4 days of continuous overnight lens usage. The mean improvement was 

9.2 lines (8-10lines). The lens prescription schedule given to these patients was 

daily wear of overnight orthokeratology lenses of 6-8 hours for 3 months. This 

unaided visual acuity of 6/6 was maintained in these patients over 3 months 

follow up. On trying alternate OK lens wear for this subgroup the unaided 

visual acuity dropped by 2.6 lines (2-3 lines)and patient dissatisfaction dictated 

resumption of daily OK lens wear. 

An unaided visual acuity improvement till 6/9 only occurred in 1 case (6.66%) 

after 3 days of continuous OK lens use. This patient had myopia of 3.75Ds and 

the aided visual acuity also was 6/9, probably due to anisometropic amblyopia. 

The mean improvement in this patient was 7.0 lines. The lens prescription 

schedule given to this patient was daily wear of overnight orthokeratology 

lenses of 6-8 hours for 3 months. 

Three patients developed hypermetropia after an average lens usage time of 

14 hours. This could be reverted by alternate day lens usage and/or shortening 

the usage time. 

The increase noted in central corneal thickness was to the tune of 30 microns 

from a pre lens average value of 546 microns. This increase was noted in only 4 

cases (26.66%) and it regressed to its baseline value after 3 weeks of continuous 

OK lens use. In the residual patients no increase in central corneal thickness 

was noted. 

Corneal endothelial cell count was not significantly affected by OK lens wear. 

The pre lens prescription 

mean value of cell count 

was 2256cells/mm 3. 

Post OK usage corneal 

endothelial cell count 

documented was 2173 

cells/mm 3. 

Tear film stability was 

evaluated by tear break 

up time (BUT). There 

was no change in the 

BUT value of 13 seconds 

(pre lens prescription) 

after consecutive OK 

lens wear. 

416 

Lens intolerance and 

Graphical representation of time in days and months 

versus improvement in unaided vision as measured by 

lines read on Snellen’s chart.


punctate keratitis were noted in 1 case respectively in this follow up period. 

Giant papillary conjunctivitis was noted after 2 months of use in 1 case 

necessitating mast cell stabilizer therapy and abstinence of OK lens for 2 

weeks. 

The mean keratometry value noted prior to lens fitting was 43.78/44.31 

(42.5-46.5)/ (42.5-46.5): mean (range). After complete follow up of 3 months 

keratometry values noted were 44.0/44.55 (42.0-46.0)/ (42.5-46.5): mean (range). 

The following figure depicts the sequential improvement in vision over a 

period of time. 

Graphical representation of time in days and months versus improvement in 

unaided vision as measured by lines read on Snellen’s chart. 

DISCUSSION 

In Indian eyes OK lens wear translates into significant and stable visual acuity 

correction. We found that patient with myopic refractive error of less than 

3.5Ds required alternate night lens wear over a follow up period of 3 months. 

With myopic error greater than 3.5Ds daily night wear schedule was needed. 

This needs to be reconfirmed on long term follow up to clarify the wearing 

schedule of OK lenses vs amount of myopia. 

Anterior Chamber Depth Changes in 

Accommodation Measured with Optical 

Coherence Tomography 

Dr. Mukesh Taneja, Dr. Debarun Dutta, Dr. Tamal Chakraborty, Dr. 

Preetam Kumar, Dr. Virender Sangwan 

The thickness of the human crystalline lens varies during accommodation. 1 

The thickness remains constant when a person fixates at non accommodative 

target. 

It is generally accepted that during accommodation, the lens thickness 

increases thus changes Anterior Chamber Depth (ACD). 2 It is well known that 

the accommodation has deep impact on the ACD of eye ball and the curvature 

of crystalline lens, but there few relevant study available which objectively 

determines how ACD changes with the different accommodative status of the 

eye. 3 

It is prudent, therefore, to establish a relationship between accommodation 

and its effect on ACD in different accommodative age group. The purpose of 

the study is to compare the changes of ACD in different modes of objective 

accommodation in different age group. 

417



The study was done with Visante Optical Coherence Tomomography (OCT) 

system which produces high resolution cross-sectional tomograms of the eye 

without contact. It comes equipped with built-in callipers and angle tools, 

and a flap tool in high resolution mode. The callipers measure to the tenth 

of a millimetre and the flap tool measures to the micron level. This is an 

effective tool to produce different objective accommodative target along with 

to measure proper ACD. 

Evaluation with Visante anterior segment OCT was done with 0, 3.0 and 5.0 

Diopter of accommodative stimuli in 3 different age group of 10-20 years 

(group A- 18 individuals), 20-40 years (group B-10 individuals) and more than 

40 years of age (group C-11individuals). 

Inclusion criteria: 

1. Age equal or more than 10 yrs 

418 

2. Male/female 

3. No previous ocular pathology 

4. No systemic illness 

5. Best corrected visual acuity is 6/12 (20/40) or better in each eye 

Exclusion criteria 

1. Any previous ocular disease 

2. Not able to cooperate with the test 

3. Any diagnosed/ symptoms of accommodative discrepancy 

Anterior Chamber depth measurement was performed using the Visantae 

anterior segment OCT (Model 1000, Software version 2), along through the 

optical axis. This is entirely a non-invasive method. During the examination 

subjects were asked to fix eyes straight at the starburst fixation target against a 

dark background. Three consecutive reading were taken with three different 

accommodative stimuli (0, 3Diopter, 5Diopter), and average was considered 

for analysis. 

RESULTS 

Total of 78 healthy eyes of 39 individuals in different age groups (36, 20 and 22 

eyes in group A, B and C respectively) were evaluated. 

The mean ages were 11.33 ± 1.15 years, 24.76 ± 4.97 years and 47.8 ± 4.18 years in 

group A, B and C respectively and average anterior chamber depths were 3.42 

± 0.22 mm, 2.98 ± 0.33mm and 2.77 ± 0.38 mm for group A, B and C respectively 

in resting condition. Anterior chamber depth was reduced by 0.223mm,


0.16mm and 0.040 mm with 3.0 Diopter and 0.233mm, 0.14mm and 0.060mm 

with 5.0 Diopter of accommodative stimuli in group A, B and C respectively. 

(Table-1). 

Table 1: ACD changes noted in group A, B and C 

Age groups ACD change with 3.0 Diopter ACD change with 5.00 Diopter 

A 0.223 ± 0.156 mm 0.233 ± 0.085 mm 

B 0.160 ± 0.220 mm 0.140 ± 0.130 mm 

C 0.040 ± 0.053 mm 0.060 ± 0.108 mm 

DISCUSSION 

Anterior Chamber Depth changes are inversely related to age, as expected in all 

Phakic subjects. Anterior Chamber Depth change per diopter accommodation 

is highest in young age groups and reduces progressively with age. ACD 

change is negligible between 3 diopter and 5 diopter accommodative stimuli 

– suggesting that as age increases, high accommodation stimuli do not have 

increased reduction of ACD and changes are almost same as 3 - 4 diopter of 

accommodation. Similar results have been published by Yan et al 4 recently in 

their modified Slit lamp OCT. 

In the presbyopic age groups the ACD changes with 3.00 dioptre of 

accommodation stimuli was less compared to all the other groups. There was 

no ACD changes with 5.00 dioper of accommodation stimuli in the presbyopic 

age group – suggesting that the presbyopic subjects failed to focus the target 

and was beyond their amplitude of accommodation. 

Anterior chamber depth decreases with increasing accommodation stimuli 

and this change is inversely related with age. 

Anterior chamber depth has significant reduction rate with increasing 

accommodation stimuli however this rate of reduction is significantly less in 

high accommodative stimuli compared with low accommodative stimuli. 

REFERENCES 

1. Richdale K et al. Lens thickness with age and accommodation by optical coherence 

tomography Ophthalmic Physiol Opt. 2008;28:441-7. 

2. Adrian Glasser, PhD. Accommodation: Mechanism and Measurement. Ophthalmol 

Clin N Am 2006;19:1-12. 

3. Tsobatzoglou A, Nemeth G, Szell N, Biro Z, Berta A. Anterior segment changes with 

age and during accommodation measured with partial coherence interferometry. J 

Cataract Refract Surg. 2007;33:1597-601. 

4. Pi-Song Yan, Hao-Tian Lin, Qi-Lin Wang, Zhen-Pin Zhang. Anterior Segment 

Variations with Age and Accommodation Demonstrated by Slit-Lamp–Adapted 

Optical Coherence Tomography. Ophthalmology. 2010 Jun 28. [Epub ahead of print]. 

419


Role of Optical Coherance Tomography in 

Boston Ocular Surface Prosthesis Fitting 

Dr. Varsha Rathi, Dr. Preeji Mandathara Sudharrman, Dr. Srikanth D, 

Dr. Virender Sangwan S 

Scleral contact lenses, also known as haptic lenses, rest on sclera and vault 

over the cornea (Figure 1.) 

The indications for these lenses include irregular astigmatism as in patients 

with keratoconus, pellucid marginal degeneration or ocular surface disease 

such as dry eye, graft versus host disease(GvHD), Stevens-Johnson syndrome 

(SJS). 1-9 The fitting is dependent on the proper apposition of haptic part of the lens 

to the sclera. The fitting of these lenses is based on direct clinical observation 

of the vault, the compression pattern of the blood vessels and impingement 

near the edge of the scleral lens. 1,9,10 The selection of the first trial lens is based 

on the clinician’s expertise in the scleral contact lens fitting. Usually the fitting 

involves the extended trial 

with the lens after lens 

wear for four to six hours 

and then reassessing the 

vault, haptic compression 

and the impingement on 

the sclera .9 

Optical coherence 

tomography (OCT) is 

a well known imaging 

method that provides 

the information about 

cornea, anterior segment, 

the angle, etc. 11 The 

clinical applications 

include measuring the 

angles in patients with Figure 1: The slit view on slit lamp biomicroscopy 

showing the vault i.e. the space between back surface of 

glaucoma, the vaults in 

the lens and the front surface of the cornea. 

case of phakic intraocular 

lenses. 11,12 Gemoules and Shen et al have shown that contact lenses can be 

imaged with OCT. 13,14 The aim of our study is to describe the role of OCT ( 

Visante OCT from Carl Zeiss, AS-OCT) in measuring the changes in the vault 

and angle after fitting the patients with fluid ventilated scleral contact lens i.e. 

Boston Ocular Surface Prosthesis (BOSP). 

420



A prospective analysis of eight eyes of 5 patients who had undergone OCT 

before and after fitting of the scleral contact lenses was done. All patients were 

referred patients to our scleral contact lens clinic. Among them 2 were males 

and 3 were females and the mean age was 36.5 (range 18 to 55 years). AS-OCT 

was performed before fitting of the BOSP, then one hour and four hours of the 

lens wear. The vault and the angle were measured with the calliper. 

BOSP fitting: The fitting of Boston scleral contact lenses is based on by noting 

the mid haptic compression, impingement and edge lift on clinical evaluation 

by slit lamp biomicroscopy. The vault is noted by noting the distance between 

the front surface of the cornea and the back surface of the lens and it is noted 

as touch (which is not desired with fluid ventilated lenses), minimal, adequate, 

generous and excessive by comparing that to the peripheral corneal thickness. 

Depending on the primary indication such as keratoconus where a generous 

vault would be desired keeping in mind the progressive nature of keratoconus 

and can be adequate for the patients with ocular surface disease where too 

much fluid would increase the debris collection within the vault and may 

result in foggy vision. 

The Visante OCT 

is equipped with 

built-in callipers 

and angle tools 

and a flap tool in 

high resolution 

mode. The 

callipers measure 

to the tenth of a 

millimeter and the 

flap tool measures 

to the micron 

level. The vault 

is measured from 

the back surface 

of the lens and 

the front surface 

of the cornea in 

the centre before 

and after lens 

insertion (Figure 

2). 

Figure 2: The vault is measured in the central area as demonstrated 

with the calliper. The normal vault for a scleral lens is between 0.25 

to 0.40 microns 

Figure 3: The angle as measured by drawing two lines in the angle 

recess. 

421


Anterior chamber angle was measured in degrees i.e. the angle recess formed 

at the apex of the anterior chamber angle, the arms being formed by drawing 

lines through the points defining the angle open distance. See Figure 3. The 

p value was calculated by student’s t-test using the Microsoft 2007 excel sheet. 

OCT 

Prior to fitting the scleral lens AS-OCT (anterior segment single and quadrant) 

was performed and then following scleral contact lens trial, AS-OCT was 

performed in the central area to have the measurements done at the same 

points in subsequent OCT measurements. The fitting involves challenging the 

eye for longer hours of lens wear. The AS-OCT was performed after 1 hour of 

lens challenge and then after 4 hours of lens challenge with scleral lenses. 

This was done using the same map, mainly comparing the height of the vault 

and the anterior chamber angles were measurement. 

RESULTS 

8 eyes of 5 patients were included in the study. The mean value of height of 

vault after 1 hour challenge with scleral contact lenses was 0.80mm and after 

4 hour challenge 

with scleral 

contact lenses 

was 0.54mm. 

Figure 4: The chart shows the reduction in vault after one hour and 

4 hours of lens wear indicating that the reduction in vault after lens 

settling may result in touch and the fitting should be assessed after 

a minimum of four hours for final ordering of the lens. 

See Chart 1. Pre 

lens wear the AC 

angles mean value 

were 39.95 (±7.45), 

38.925(±9.285). 

Post lens wear 

after 1hour the AC 

angle mean value 

were 41.75(±6.161), 

39.76(±8.121) and 

after 4hours 

the AC angle 

mean value were 

40.25(±9.839), 38.87(±7.805), the difference was not significant statistically (p 

>0.05). 

DISCUSSION 

Our analysis showed the reduction in vault after four hours of lens wear 

compared to one hour after lens wear. Till now, the fitting of scleral contact 

lenses is subjective. Measurement of vault with the AS-OCT may help in 

422


preventing the contact of scleral lens to the cornea. This is important as these 

lenses are indicated for patients with keratoconus and constant rubbing of the 

contact lens or cornea may result in scarring. Scleral contact lenses are used 

for irregular astigmatism as in keratoconus, pellucid marginal degeneration 

and post graft high irregular astigmatism or for ocular surface disease such 

as SJS, GvHD. Keratoconus is usually bilateral and is progressive disease. As 

keratoconus progresses, the vault may reduce resulting in scarring. Hence, 

measuring the vault in the initial fitting may help us in increasing the vault in 

cases which would progress such as keratoconus and the same may be can be 

applied to post LASIK or sometimes post graft ectasia. 

This is important as the same lens can be worn for a longer duration of days if 

the other parameters of the fitting remain same. As these lenses rest on sclera 

and do not touch the cornea, the fitting is not affected by corneal curvature 

and even when the corneal curvature increases, with adequate vault the 

fitting may remain the same provided the haptic bearing scleral does not have 

any changes. With the reduction in vault there was a theoretical possibility 

of haptic compressing the globe but there was no statistically significant 

difference between the angles before and after lens wear. So, assessment of 

vault with OCT may help in titrating the vault in patients of keratoconus and 

ocular surface disease. Gemoules et al have reported OCT being used in the 

fitting of the scleral lenses routinely by noting the toricity of peripheral sclera. 

12 In our analysis, the vault reduced after four hours of lens wear, which 

helped us in ordering the lenses with more vault. This is especially important 

in finalizing the fitting of these lenses especially when the vault is borderline. 

To conclude, OCT is helpful in determining the vault and angle compression 

in fitting patients with fluid ventilated scleral lens and, though our number is 

less, the results were promising. 

REFERENCES 

1. Rathi VM, Mandathara P, Dumpathi S, Vaddavalli PV, Sangwan VS. Boston ocular 

surface prosthesis: an Indian Experience. Indian Journal Ophthalmol. In Press 

2 Ridley F. Scleral Contact Lenses. Their Clinical Significance. Arch Ophthalmol 

1963;70:740-5. 

3. Ridley F. Therapeutic uses of scleral contact lenses. Int Ophthalmol Clin 1962;2:687- 

716. 

4. Pullum KW, Whiting MA, Buckley RJ. Scleral contact lenses: the expanding role. 

Cornea 2005;24:269-77. 

5. Romero-Rangel T,Stavrou P, Cotter J et al. Gas-permeable scleral contact lens 

therapy in ocular surface disease. Am J Ophthalmol 2000;130:25-32. 

6. Rosenthal P, Cotter J. The Boston Scleral Lens in the management of severe ocular 

surface disease. Ophthalmol Clin North Am 2003;16:89-93. 

423


7. Rosenthal P, Croteau A. Fluid-ventilated, gas-permeable scleral contact lens is 

an effective option for managing severe ocular surface disease and many corneal 

disorders that would otherwise require penetrating keratoplasty. Eye Contact Lens 

2005; 31:130-134. 

8.. Jacobs D S, Rosenthal P. Boston scleral lens prosthetic device for treatment of 

severe dry eye in chronic graft-versus-host disease. Cornea 2007;26:1195-9. 

9. Rathi VM, Mandathara PS, Vaddavalli PK, Sangwan VS. Boston ocular surface 

prosthesis in vernal keratoconjunctivitis. Eye and Contact Lens. (In Press) 

10. Visse E S, Visser R, van Lier HJ et al. Modern scleral lenses part I: clinical features. 

Eye Contact Lens 2007;33:13-20. 

11. Ramos JL, Li Y, Huang D. Clinical and research applications of anterior segment 

optical coherence tomography-a review. Clin Experiment Ophthalmol 2009;37:81-9. 

12. Alfonso JF, Lisa C, Palacios A et al. Objective vs subjective vault measurement after 

myopic implantable collamer lens implantation. Am J Ophthalmol 2009;147:978-83 

e1. 

13. Gemoules G. A novel method of fitting scleral lenses using high resolution optical 

coherence tomography. Eye Contact Lens 2008;34:80-3. 

14. Shen M, Wang MR, Wang J et al. Entire contact lens imaged in vivo and in vitro 

with spectral domain optical coherence tomography. Eye Contact Lens 2010;36:73-6. 

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