Varikuti PhD thesis final.pdf - Anglia Ruskin Research Online

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Tables 5.3(A) and 5.3(B): Depicts the normalised thresholds and the meannormalised thresholds obtained for the SGRL chart and SGCI chart respectivelyfor all the separations and isolated letter condition for the normal subjects.A Normalised Repeat letter thresholdsSeparation Abutting 0.2 0.4 0.6 1.0 IsolatedSubjectsEO 0.22 0.10 0.06 0.04 0.01 0.00JS 0.28 0.14 0.07 0.05 0.02 0.00VV 0.12 0.00 -0.03 -0.06 -0.04 0.00Mean 0.21 0.08 0.03 0.01 0.00 0.00Std error 0.08 0.07 0.06 0.06 0.03 0.00B Normalised Complex letter thresholdsSeparation Abutting 0.2 0.4 0.6 1.0 IsolatedSubjectsEO 0.30 0.18 0.13 0.08 0.03 0.00JS 0.37 0.25 0.18 0.15 0.11 0.00VV 0.21 0.11 0.07 0.03 0.02 0.00Mean 0.29 0.18 0.13 0.09 0.05 0.00Std error 0.08 0.07 0.06 0.06 0.05 0.00225
The data for the mean and the normalised mean (threshold value at eachseparation - isolated letter threshold value) for the SGRL and SGCI thresholdsfor the normal subjects are shown in Figure 5.4. The difference between theSGRL and SGCI thresholds was nearly constant across letter separationconditions. A regression analysis was carried out between the SGRL andcomplex interaction thresholds in subjects with normal vision. The difference inthresholds between the SGRL and SGCI was plotted as a function of inter-letterseparation and is shown in Figure 5.4. Each point represents the meandifference between the SGCI and SGRL thresholds at each separation condition.The data were fit using a straight line function and the correspondingregression analysis showed that the slope of the line was not significantlydifferent from zero (p>0.05).A two factor within subject factorial ANOVA was performed for the normalsubjects using letter separation and charts (SGRL and SGCI) as the mainfactors. There was a significant main effect of separation on recognitionthresholds F (1.15, 2.30) = 81.14, p < 0.01 and a significant main effect of thetype of chart on recognition thresholds F (1, 2) = 48.22, p < 0.05. There was nosignificant interaction effect between the range of letter separations used foranalysis and type of the charts used in the study F (1.21, 2.42) = 8.40, p >0.05.226
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ANGLIA RUSKIN UNIVERSITYFURTHER INS
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ANGLIA RUSKIN UNIVERSITYABSTRACTFAC
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TABLE OF CONTENTSACKNOWLEDGEMENTS .
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...................................
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Table 4.5(A) and 4.5(B): Depicts th
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Tables 5.8(A) and 5.8(B): Depicts t
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Chapter 1General IntroductionVision
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Visual acuity chartsSnellen chartTh
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Bailey-Lovie LogMAR chartThe LogMAR
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An accurate and repeatable measurem
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elimination of one or more of these
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1985; 1988). Greater crowding in yo
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In order to study the reliability o
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A significant difference in visual
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has gained increased attention foll
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Figure 1.3: Depicts the picture of
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Landolt C surrounded by flanking ba
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Figure 1.4: Depicts the picture of
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normal vision and at the fovea and
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educed at the abutting condition wh
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Figure 1.5: Depicts the data obtain
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fixations in normal eyes. Further,
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Figure 1.6: Example of a Regan repe
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and adults had better isolated lett
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(Glasgow acuity poorer than the iso
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closer separations based on the fin
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identify. On the other hand a 10 mi
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Figure 1.7: Example of a PVA test c
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the inner letters resulting in miss
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gaze instability in amblyopes. A se
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each letter in the low contrast Sne
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1999a), the findings are contradict
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RationaleTo determine the effect of
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In most of the studies (Stuart and
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study the effect of contour interac
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contour interaction effect and not
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contour interaction as the Snellen
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In this experiment, the effect of l
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The final set of experiment will in
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Chapter 2The effect of contour inte
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laterality (unlike the Illiterate E
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ProcedureGeneral conditionSix adult
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Figure 2.2: Schematic showing examp
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Figure 2.3: Schematic of the SGRL s
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were corrected by adjusting the deg
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Figure 2.4: The data shown in the f
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thresholds normalised against the i
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Table 2.1: (A) Depicts high contras
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IH was replaced by his slope value
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Table 2.2: Depicts slopes obtained
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Figure 2.7: The data shown are a la
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Table 2.3: (A) Depicts recognition
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Figure 2.9:93
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Figure 2.1196
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Figure 2.13:99
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error bars represent ± 1 SD.101
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The effect of the relative letter l
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Figure 2.15: The graph shows mean l
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Normalised recognition thresholds (
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DiscussionThe main results of this
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Since the experiment of Flom, Weymo
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showed that the target flanker simi
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gaze instability and attention comp
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MethodsMethod of generating low con
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the low contrast letters were more
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was the same as that described in C
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isolated letter in each slide was l
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the identification of the isolated
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Threshold of psychometric functions
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The threshold values obtained from
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AB133
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Figure 3.4: Depicts normalised thre
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Slopes of psychometric functionsThe
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Figure 3.5: Average slope of the ps
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esulting in improved threshold visu
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employed the same size target for t
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Freeman, 1981). As a result of the
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Table 4.1: Depicts the visual featu
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same as that of the main experiment
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Figure 4.2: The recognition thresho
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Table 4.2: Depicts the test distanc
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Figure 4.3: The percentage correct
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2 X contrastSubject Eye Contrast th
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A (amblyopic eyes) B (non-amblyopic
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Figure 4.5: Recognition thresholds
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Figure 4.6(A) shows mean recognitio
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Figure 4.6: (A) Recognition thresho
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Figure 4.7: Depicts normalised thre
Page 188 and 189: Further, the estimates of slopes ob
Page 190 and 191: Table 4.6(A) and 4.6(B): Depicts th
Page 192 and 193: Low contrast conditionFor all the f
Page 194 and 195: A (non-amblyopic eyes) B (amblyopic
Page 196 and 197: Table 4.7(A) and 4.7(B): Depicts th
Page 198 and 199: Figure 4.10: Depicts the layout of
Page 200 and 201: Figure 4.11(A) shows mean absolute
Page 202 and 203: A189
Page 204 and 205: The threshold values of all the sep
Page 206 and 207: Figure 4.12: Depicts normalised thr
Page 208 and 209: Further, the estimates of slopes fo
Page 210 and 211: 197
Page 212 and 213: High and low contrast conditionThe
Page 214 and 215: DiscussionThe current experiment in
Page 216 and 217: ecognition thresholds were nearly t
Page 218 and 219: on the target size and the extent o
Page 220 and 221: the contrast sensitivity loss was d
Page 222 and 223: Simmers, Gray, McGraw and Winn, 199
Page 224 and 225: separations are also immune to the
Page 226 and 227: SGCI chart was surrounded by an add
Page 228 and 229: ProcedureGeneral conditionThree adu
Page 230 and 231: Chapters 2 and 4 where the effect o
Page 232 and 233: ResultsGeneral conditionFor the 3 n
Page 234 and 235: The effects of crowding on visual a
Page 236 and 237: Tables 5.2(A) and 5.2(B): Depicts t
Page 240 and 241: Figure 5.4(A): The top panel depict
Page 242 and 243: Further, the estimates of slopes ob
Page 244 and 245: Table 5.4(A) and (B): Depicts the s
Page 246 and 247: and mean complex interaction thresh
Page 248 and 249: 235
Page 250 and 251: A (non-amblyopic eyes) B (amblyopic
Page 252 and 253: Figure 5.8: The difference between
Page 254 and 255: Std error 0.05 0.06 0.06 0.07 0.07
Page 256 and 257: For the amblyopic subjects, a three
Page 258 and 259: Tables 5.7(A) and 5.7(B): Depicts t
Page 260 and 261: Control conditionError analysisData
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Page 264 and 265: DiscussionThe current experiment in
Page 266 and 267: Based on these findings, we attribu
Page 268 and 269: and Spowart, 1997), multiple E opto
Page 270 and 271: Chapter 6Summary and conclusionsThe
Page 272 and 273: The effect of contour interaction o
Page 274 and 275: demonstrable at the abutting condit
Page 276 and 277: SGCI thresholds when measured for s
Page 278 and 279: REFERENCESABRAHAMSSON, M. and SJOST
Page 280 and 281: BERNARD, J.B. and CHUNG, S.T.L., 20
Page 282 and 283: ELLIOTT, D., BULLIMORE, M., PATLA.
Page 284 and 285: HARIHARAN, S., LEVI, D.M. and KLEIN
Page 286 and 287: JACOBS, R.J., 1979. Visual resoluti
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LEVI, D.M., KLEIN, S.A. and HARIHAR
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OWSLEY, C., 1994. Vision and drivin
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ROBINSON, D.A., 1964. The mechanics
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SIMMERS, A.J., GRAY, L.S. and WINN,
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AppendicesAppendix 1: Depicts the p
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three and two amblyopic subjects re
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Appendix 3:287
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Appendix 4: The percentage of subst
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Appendix 5: Depicts the letter conf
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