The effect of glare upon visual performance in keratoconus

Besides a loss in resolution acuity, amblyopia results in deficits in a number of visual functions in the amblyopic eye. We describe impairment in oscillatory movement displacement thresholds (OMDT) in childhood amblyopia. 50 subjects (aged 74 ± 16 months) with strabismic, anisometropic or mixed aetiology amblyopia were compared to a group of 24 age-matched controls. Thresholds were demonstrated to be in the hyperacuity range and were not related to the visual acuity. OMDT was significantly reduced in the amblyopic eye compared to the dominant and control eyes ( P < 0.05) only when no stereoscopic responses were demonstrated. When gross stereopsis was present, thresholds for the amblyopic eyes were comparable with both the dominant and control eyes. The results are discussed in terms of binocular competition and developmental anomaly.     

Long term effect of hypermetropic anisometropia on the visual acuity of treated amblyopic eyes

AIM—To evaluate the effect of the extent of hypermetropic anisometropia on the long term visual acuity results in amblyopic eyes following their treatment by occlusion.
METHODS—The visual acuity of 86 patients, who had been treated for unilateral amblyopia by occlusion of the fellow eye and followed up at least to the age of 9 years, was examined 6.4 years, on average, after cessation of treatment. Patients were divided into two groups—those with a small amount of hypermetropic anisometropia, where the spherical equivalent difference between the eyes ranged between 0 and +1.50 dioptres, and those with a large amount of hypermetropic anisometropia, where the difference was +1.75 dioptres or greater.
RESULTS—Deterioration of visual acuity after cessation of occlusion treatment occurred in 51% of the patients in the group with a small amount of anisometropia and in 75% of the patients in the group with a large amount. At cessation of treatment, the average visual acuity in both groups was 20/40+. At the long term follow up examination, however, the average visual acuity was 20/40− and 20/70, respectively. This difference was statistically significant.
CONCLUSIONS—Hypermetropic anisometropia greater than 1.50 dioptres appears to be a risk factor for deterioration of visual acuity in the long term, following treatment of amblyopic eyes by occlusion of the fellow eye.

Keywords: amblyopia; hypermetropic anisometropia; strabismus     

Effectiveness of occlusion therapy in ametropic amblyopia: a pilot study

AIMS/BACKGROUND—To examine the relative contributions of non-specific (for example, spectacle correction) and specific (that is, occlusion therapy) treatment effects on children with ametropic amblyopia. To assess the importance and practicality of objectively confirming the prescribed occlusion dose.
METHODS—Subjects were entered into a two phase trial. In the first (`pretreatment') subjects were provided with spectacle correction and underwent repeat visual acuity (VA) and contrast sensitivity (CS) testing until acuity in their amblyopic eye had stabilised. Subjects then progressed to the second phase (`treatment') in which they underwent direct, unilateral occlusion for 1 hour per day for 4 weeks. Patching was objectively monitored using an occlusion dose monitor.
RESULTS—Eight subjects completed the trial, all but one of whom achieved >80% concordance with the occlusion regimen. Within the pretreatment phase, mean amblyopic eye VA improved by 0.19 log units (p=0.008) while mean CS gained 0.09 log units (p=0.01). An identical improvement in mean VA was recorded in the fellow eyes (p=0.03) while mean CS gained 0.11 log units (p=0.02). Within the treatment phase, mean VA further improved (0.12 log units, p=0.009) although this gain had halved by the end of treatment and was no longer statistically significant (p=0.09).
CONCLUSIONS—Visual performance improved significantly during pretreatment whereas further gains seen during occlusion were not sustained. Evaluation of occlusion regimens must take into consideration the potentially confounding influence of `pretreatment effects' and the necessity to confirm objectively the occlusion dose a child receives.

     

Atropine penalisation versus occlusion as the primary treatment for amblyopia

AIMS/BACKGROUND—Pharmacological penalisation of non-amblyopic eyes is an infrequently used alternative to occlusion for treating amblyopia. The authors compared the efficacy of atropine penalisation and that of occlusion as a primary treatment for amblyopia.
METHODS—Thirty six newly diagnosed patients with amblyopia were allocated to two groups for treatment. Eighteen patients in each group were treated either with atropine penalisation (group A) or occlusion therapy (group P).
RESULTS—There was a statistically significant improvement in visual acuity in both groups treated. In group A improvement of the geometric mean visual acuity of the amblyopic eye was from 6/50 to 6/11 (p<0.001). In group P improvement of the geometric mean visual acuity was from 6/60 to 6/19 (p<0.001). In group A non-compliance with treatment was only 6% (2/18). Non-compliance in group P was 45% (8/18) at some stages of the treatment. Neither group produced an incidence of occlusion amblyopia.
CONCLUSIONS—In this study atropine penalisation has been shown to be as effective as occlusion therapy in the treatment of amblyopia. Patient acceptance of atropine penalisation was superior to that for occlusion therapy as was shown by the compliance rate. Atropine treatment was also advantageous in that compliance could be readily checked by inspection.

     

An inner city preschool visual screening programme: long term visual results

AIMS—The aim of this study was to investigate the long term outcome of the treatment of amblyopia as a sequel to preschool screening, which has not hitherto been described.
METHODS—All patients originally referred from a preschool screening programme were recalled for examination by letter. 255 patients were reviewed at least 4 years after discharge of which 88 were definitely amblyopic at presentation and 107 were not amblyopic at presentation and were used as controls.
RESULTS—79% of the amblyopes improved or maintained visual acuity after discharge but this was reduced to 42% after an age induced increase (estimated from the controls) was compensated for. The mean drop in visual acuity in the amblyopic eyes which deteriorated was 0.23 (SD 0.15) logMAR units. Stepwise multiple linear regression showed that the best single predictor of post-discharge deterioration in visual acuity was the improvement in visual acuity seen during treatment (R² = 19%). Eccentric fixation at time of follow up (increasing R² to 47%) and good presenting acuity (further raising R² to 57%) contributed additional information, and were both associated with greater post-discharge deterioration in visual acuity.
CONCLUSIONS—The majority of amblyopes who attended for follow up maintained or improved their visual acuities after discharge. Those patients who demonstrated deterioration of their amblyopia had usually improved well during the programme and were often fixating eccentrically at follow up.

Keywords: screening; amblyopia; children     

Visual outcome after paediatric cataract surgery: is age a major factor?

AIMS—To determine functional results after unilateral and bilateral cataract surgery in children with different aphakic optical correction.
METHODS—In this retrospective study, we evaluated visual acuity and binocular vision in 107 children who underwent cataract surgery during the 10 year period from 1985 to 1995. Aphakia was corrected by an intracapsular intraocular lens (IOL), spectacles or contact lenses.
RESULTS—Mean visual acuity was >20/40 (<0.3 log MAR) with normal binocular vision in 58 children over 7 months of age operated on for bilateral cataracts. Pseudophakic eyes regained visual acuity >20/63 (<0.5 log MAR) more often (90%) than aphakic eyes (46%) (p<0.001). Binocular vision was also achieved more often after IOL implantation (p<0.001). Visual outcome of early bilateral cataracts was less satisfactory in children with abnormal foveolar function. For 49 children who had surgery for unilateral cataracts, prognosis was poor when surgery was performed before the age of 7 months. For cataract surgery in older children (7 months) mean visual acuities were better with IOL implantation (p<0.05).
CONCLUSION—Cataract surgery with unilateral and bilateral IOL implantation can provide a beneficial effect on final visual outcome in children who are operated on before abnormal foveolar function develops.

Keywords: binocular vision; intraocular lens; paediatric cataract; visual outcome     

A clinic based survey of blindness and eye disease in Cambodia

AIMS—To survey the spectrum of eye disease presenting to rural eye clinics in Cambodia.
METHODS—A total of 1381 patients seen consecutively at 13 eye clinics were examined and the findings recorded.
RESULTS—231 (16.7%) were bilaterally blind (visual acuity <3/60 in both eyes); 263 (19%) were unilaterally blind, and 169 (12%) had low vision (visual acuity <6/18 in the better eye). Cataract was the commonest cause of visual loss in all three categories and was responsible respectively in 69%, 40%, and 55% of each group. Trachoma was diagnosed in 13% of patients. Thirty three of them needed lid surgery for trichiasis.
CONCLUSION—With the difficult practical and political situation in Cambodia there seems little prospect of making substantial inroads into the backlog of avoidable blindness in the near future.

     

Prospective study of New Zealand infants with birth weight less than 1500 g and screened for retinopathy of prematurity: visual outcome at age 7-8 years

AIM—To determine the visual outcome at 7-8 years in very low birth weight (VLBW: birth weight <1500 g) infants screened for retinopathy of prematurity (ROP).
METHODS—In 1986 all 413 VLBW infants admitted to neonatal units in New Zealand were enrolled in a prospective study of acute ROP. Surviving infants were traced and assessed at a home visit. Visual assessment comprised examination for abnormal and range of eye movements, visual fields, distance and near visual acuity, stereopsis, and photorefraction.
RESULTS—Of 338 infants surviving to discharge, 313 (93%) had been examined for acute ROP. ROP was present in 66 (21%: ROP+), absent in 247 (ROP−), with 25 not examined (NA). 298 children (96% survivors resident in New Zealand: 91% all survivors) were assessed. Any visual problem occurred in 79% ROP+ and 60% ROP−/NA (p<0.01). Distance visual acuity less than 4/10 in the worse eye occurred in 29% ROP+ and 15% ROP−/NA (p<0.05); and in the better eye in 19% ROP+ and 5% ROP−/NA (p<0.001). Any myopia in the worse eye occurred in 36% ROP+ and 18% ROP−/NA (p<0.01); and in the better eye in 25% ROP+ and 11% ROP−/NA (p<0.01). Strabismus, including treated, occurred in 33% ROP+ and 19% ROP−/NA (p<0.05). Overall, 11% had astigmatism and 18% hypermetropia with no difference between the groups.
CONCLUSION—In a population based study it was confirmed that VLBW is associated with an increased risk of visual problems at school age. A history of ROP is associated with an additional risk of poor outcome, including a near doubling of poor distance acuity, myopia, and strabismus.

     

Screening for amblyopia: a comparison of paediatric letter tests

AIMS/BACKGROUND—The measurement of visual acuity is the most widely accepted indicator of amblyopia and is thought by some to be the only effective screening test. The aim of this study was to investigate the effectiveness of the traditional single optotype Sheridan-Gardiner test (SGT) in the measurement of visual acuity and the detection of amblyopia, compared with the log based linear format Glasgow acuity cards (GAC).
METHODS—In the present study visual acuity was measured monocularly in 702 primary 1 schoolchildren using both acuity tests.
RESULTS—A significant difference was found in the mean (SD) visual acuity measured with GAC (0.9 (0.08) modified logMAR) and SGT (1.13 (0.09) modified logMAR), df=632, t=−59.08, p=0.0001. The majority of children (89.3%) achieved visual acuities better than 6/6 in either eye when using the single optotype test. If the 95% confidence limits for a significant interocular difference in acuity are used as criteria for the detection of unilateral amblyopia, GAC were found to be the most sensitive, correctly identifying 100%, while SGT identified 55% of the children with unilateral amblyopia.
CONCLUSION—The results of this study highlight several problems with both the test format and testing procedure in the present school screening system.

     

Longer term visual outcome of eyes with retinopathy of prematurity treated with cryotherapy or diode laser

AIMS—Visual outcome of 66 eyes in 37 patients who had undergone treatment with either cryotherapy or diode laser for threshold retinopathy of prematurity was assessed.
METHODS—17 patients, representing 30 eyes treated with cryotherapy, were examined at between 56 and 98 months corrected age (median 68 months). 20 patients representing 36 eyes treated with diode laser, were examined at between 30 and 66 months corrected age (median 51 months). Structural outcome was categorised as: optimal—flat posterior pole; suboptimal—macular ectopia, optic nerve hypoplasia, retinal fold involving the macula, and retinal detachment involving the macula.
RESULTS—Optimal structural outcome was, in the absence of amblyopia, associated with optimal visual acuity (of 6/12 or better) in all cases, with most eyes achieving a visual acuity of 6/9 or 6/6. Suboptimal structural outcome was invariably associated with suboptimal visual acuity. Amblyopia was present in eight out of 20 cryotherapy treated eyes and in five out of 26 laser treated eyes with an optimal structural outcome. Refractive errors were significantly less in laser treated eyes as was the incidence of anisometropic amblyopia.
CONCLUSION—Eyes treated with either cryotherapy or diode laser for threshold retinopathy of prematurity with optimal structural outcome are associated with development of optimal visual acuity—that is, 6/12 or better. Treatment with either cryotherapy or laser does not in itself reduce the visual potential of these eyes.

Keywords: retinopathy of prematurity; cryotherapy; laser; visual acuity     

Visual functioning and quality of life outcomes among cataract operated and unoperated blind populations in Nepal

BACKGROUND—Visual acuity and vision related quality of life outcomes in cataract surgery were evaluated in a population based survey in two geographic zones in Nepal.
METHODS—Case finding was based on random sampling using a stratified cluster design with door to door enumeration of people aged 45 years followed by eye examinations at village sites. All aphakics/pseudophakics, those with visual acuity less than 6/60 in either eye, and a sample of those with normal visual acuity were administered visual functioning (VF) and quality of life (QOL) questionnaires.
RESULTS—15% of the 159 cataract operated cases had presenting visual acuity 6/18 in both eyes, 38% with best corrected visual acuity. 21% were still blind with presenting visual acuity <6/60 in both eyes, 7% with best correction. On a 0-100 scale, mean VF and QOL scores were 87.2 and 93.9 respectively in normally sighted unoperated individuals, dropping to 15.6 and 29.5 for those severely blind (<3/60). Among the cataract operated, mean VF and QOL scores were 47.5 and 55.4, respectively. VF and QOL scores correlated with vision status at statistically significant levels (p <0.0001)
CONCLUSION—Cataract surgery outcomes, whether measured by traditional visual acuity or by patient reported VF/QOL, are at levels many would consider unacceptably low. It is apparent that in the quest to reduce cataract blindness much more attention must be given to improving surgery outcomes.

Keywords: cataract surgery; visual acuity; visual functioning; quality of life     

Factors Influencing the Prevalence of Amblyopia in Children with Anisometropia

Purpose

To evaluate factors that can influence the prevalence of amblyopia in children with anisometropia.

Methods

We retrospectively reviewed the records of 63 children 2 to 13 years of age who had anisometropic amblyopia with a difference in the refractive errors between the eyes of at least two diopters (D). The type of anisometropia (myopia, hyperopia, and astigmatism), degree of anisometropia (<2-3 D, <3-4 D, or >4 D), best corrected visual acuity (BCVA) of the amblyopic eye at the time of initial examination, BCVA differences between sound and amblyopic eyes, whether or not occlusion therapy was performed, compliance with occlusion therapy, and the patient''s age when eyeglasses were first worn were investigated.

Results

There was an increase in the risk of amblyopia with increased magnitude of anisometropia (p=0.021). The prevalence of amblyopia was higher in the BCVA <20/40 group and in patients with BCVA differences >4 lines between sound and amblyopic eyes (p=0.008 and p=0.045, respectively). There was no statistical relationship between the prevalence of amblyopia and the type of anisometropia or the age when eyeglasses were first worn. Poor compliance with occlusion therapy was less likely to achieve successful outcome (p=0.015).

Conclusions

Eyes with poor initial visual acuities of <20/40, a high magnitude of anisometropia, and a >4 line difference in the BCVA between sound and amblyopic eyes at the initial visit may require active treatment.     

Cryotherapy and laser treatment for acute retinopathy of prematurity: refractive outcomes, a longitudinal study

BACKGROUND—Infants who require treatment for threshold retinopathy of prematurity are at increased risk of developing refractive errors. Following the introduction of laser treatment for threshold disease, the clinical impression was that the degree of myopia was reduced compared with cryotherapy.
METHODS—A longitudinal study was carried out of refractive error at 3 and 12 months in 19 patients undergoing cryotherapy and 15 patients undergoing laser treatment.
RESULTS—At 3 months the median spherical equivalent refractive error in the right eye was −3.25 dioptres after cryotherapy and +0.25 dioptres after laser therapy (similar results left eye). The median spherical equivalent refractive error in the right eye at 12 months was -5.25 dioptres following cryotherapy and -0.50 dioptres after laser (similar results left eye). There was a statistically significant difference in median spherical refractive error between the therapies at 3 months and 12 months (p<0.05 Wilcoxon rank sum) in both eyes.
CONCLUSION—Laser therapy is associated with lower degrees of myopia during the first year of life, which is clinically significant in terms of visual performance and development.

     

A new computer program for mass screening of visual defects in preschool children

AIMS—To test the effectiveness of a PC computer program for detecting vision disorders which could be used by non-trained personnel, and to determine the prevalence of visual impairment in a sample population of preschool children in the city of Beer-Sheba, Israel.
METHODS—292 preschool children, aged 4-6 years, were examined in the kindergarten setting, using the computer system and "gold standard" tests. Visual acuity and stereopsis were tested and compared using Snellen type symbol charts and random dot stereograms respectively. The sensitivity, specificity, positive predictive value, negative predictive value, and kappa test were evaluated. A computer pseudo Worth four dot test was also performed but could not be compared with the standard Worth four dot test owing to the inability of many children to count.
RESULTS—Agreement between computer and gold standard tests was 83% and 97.3% for visual acuity and stereopsis respectively. The sensitivity of the computer stereogram was only 50%, but it had a specificity of 98.9%, whereas the sensitivity and specificity of the visual acuity test were 81.5% and 83% respectively. The positive predictive value of both tests was about 63%. 27.7% of children tested had a visual acuity of 6/12 or less and stereopsis was absent in 28% using standard tests. Impairment of fusion was found in 5% of children using the computer pseudo Worth four dot test.
CONCLUSIONS—The computer program was found to be stimulating, rapid, and easy to perform. The wide availability of computers in schools and at home allow it to be used as an additional screening tool by non-trained personnel, such as teachers and parents, but it is not a replacement for standard testing.

Keywords: screening; visual defects; amblyopia; computer program; stereopsis     

Effects of 0.5% apraclonidine on optic nerve head and peripapillary retinal blood flow

AIMS—To examine the effects of 0.5% apraclonidine on optic nerve head (ONH) and peripapillary retinal blood flow by scanning laser Doppler flowmetry (SLDF).
METHODS—ONH and peripapillary retinal blood flow of 17 healthy subjects were measured by SLDF before and 1 hour and 3 hours after unilateral administration of 0.5% apraclonidine. The fellow eyes were treated with balanced salt solution and the examiners were masked as to which eye was treated with apraclonidine. On each occasion, three scans were obtained and haemodynamic variables (volume, flow, and velocity) were analysed at eight locations, four in the neural rim and four in the peripapillary retina, avoiding ophthalmoscopically visible vessels. The statistical significance of changes from the baseline value of variables and the differences in the measured quantities between apraclonidine treated eyes and fellow eyes at each time point were evaluated using Wilcoxon signed rank test.
RESULTS—The intraocular pressure was reduced significantly in apraclonidine treated eyes by 15.0% (p=0.001) at 1 hour and 30.0% (p=0.000) at 3 hours after administration. In the volume, flow, or velocity of ONH and peripapillary retinal blood flow, there were no significant changes from the baseline values at 1 hour and 3 hours after apraclonidine administration in either apraclonidine treated eyes (p >0.4) or fellow eyes (p >0.2). Also, no significant differences were found in the measured quantities between apraclonidine treated eyes and fellow eyes at each time point (p >0.1).
CONCLUSION—A single dose of topical apraclonidine 0.5% in healthy subjects does not have adverse effects on the ONH and peripapillary retinal blood flow.

     

Successful visual rehabilitation after neonatal penetrating keratoplasty

BACKGROUND—Penetrating keratoplasty in infancy and childhood has traditionally met with limited visual success due to a combination of unique physiology and technical problems in this patient population. With the advances in microsurgical instrumentation, corneal preservation, and visual developmental physiology ophthalmologists are finding increasing indications for penetrating keratoplasty in the childhood population. The long term results of neonatal penetrating keratoplasty in two patients with unilateral congenital corneal opacification are reported.
METHODS—Penetrating keratoplasty was performed on one eye in each of two infants within the first 3 weeks of life. Amblyopia treatment and optical therapy have been continued since surgery.
RESULTS—After 6 years both grafts have remained clear. One patient developed the infantile esotropia syndrome. Visual development using Snellen optotypes is age normal for both transplanted eyes.
CONCLUSIONS—Penetrating keratoplasty when combined with optical correction and amblyopia therapy may restore and preserve vision in selected patients with congenital corneal opacification if performed in the neonatal period.

     

Macular and peripapillary retinal nerve fiber layer thickness in children with hyperopic anisometropic amblyopia

AIM:To compare the retinal nerve fiber layer (RNFL) thickness and macular thickness in the amblyopic eye with that in the sound eye of children with hyperopic anisometropic amblyopia using optical coherence tomography (OCT).METHODS: A prospective, nonrandom, intraindividual comparative cohort study includes 72 children with hyperopic anisometropic amblyopia in a single center. Macular thickness, macular foveola thickness, and peripapillary RNFL thickness were compared between the amblyopia eyes and the contralateral sound eyes.RESULTS:There were 38 male and 34 female patients, with a mean age as 9.7±1.9 years (range, 5–16 years). Hyperopic was +3.62±1.16D (range +2.00D to +6.50D) in the amblyopic eyes, which was significantly higher in the control eyes with +0.76±0.90D (range 0D to +2.00D) (P < 0.01). The mean peripapillary RNFL thickness was 113.9±7.2µm and 109.2±6.9µm in the amblyopic eye and the normal eye, respectively, reaching statistical significance (P = 0.02). The mean macular foveola thickness was significantly thicker in the amblyopic eyes than the contralateral sound eyes (181.4±14.2µm vs 175.2±13.3µm, P < 0.01), but the 1mm, 3mm or 6mm macular thickness central macular thickness was not significantly different. Degree of anisometropia in the contralateral eyes was not significantly correlated with differences of peripapillary RNFL, macular foveola thickness or central macular thickness.CONCLUSION:Eyes with hyperopic anisometropic amblyopia are found thicker macular foveola and peripapillary RNFL than the contralateral eyes in children.     

Clinical characteristics of microtropia—is microtropia a fixed phenomenon?

BACKGROUND/AIMS—Microtropia is believed to be a static condition, in which accepted achievable levels of vision are those of 6/12-6/9 maximum, with the inability to achieve "normal" levels of stereopsis. The aim of this paper was to present the results of treatment of 30 consecutively presenting primary microtropes, and assess their outcomes using a more active treatment strategy than that conventionally used.
METHODS—Visual acuity, stereoacuity, fixation, and the presence of a central suppression scotoma were assessed in all patients before, during, and after treatment, which comprised wearing maximum refractive correction, and an occlusion strategy aiming for equal visual acuity.
RESULTS—Equal visual acuity of 6/5 Snellen was achieved in 43% of the 30 patients, while 87% achieved 6/9 Snellen or better visual acuity in the microtropic eye. Stereoacuity of better than 60" of arc was attained in 37%, and foveal fixation on visuscopy in 55%. The treatment outcome was not affected by the patient's age, initial visual acuity, or the amount of anisometropia. A change in the patient's diagnosis was noted in 50%, with nine patients recovering completely.
CONCLUSIONS—The results show that microtropia is not static. Equal 6/5 vision is attainable, as is high grade stereoacuity. The pattern of fixation may change during treatment and elimination of the microtropia is possible in some cases. There is a requirement for management protocols to be changed in order to treat this condition more effectively.

Keywords: microtropia; amblyopia; eccentric fixation     

Recovery in microtropia: implications for aetiology and neurophysiology

AIMS/BACKGROUND—The basis of binocular single vision in microtropia remains a matter of contention. This paper discusses the implications of recovery, in a group of primary microtropes following treatment, in relation to current concepts on the aetiology of the condition and proposed retinocortical correspondence.
METHODS—Nine previously untreated primary microtropes whose condition resolved, were reviewed in detail to assess the patterns of change in retinal correspondence, uniocular fixation, stereoacuity, and visual acuity in response to treatment.
RESULTS—Anomalous retinal correspondence (ARC), a central scotoma, reduced or absent stereoacuity, amblyopia, and uniocular eccentric fixation were present in all patients before treatment. Following treatment, all cases attained normal retinal correspondence (NRC), elimination of the central scotoma, stereo acuity levels of between 20 and 40 seconds of arc, 6/5 Snellen visual acuity in both eyes, and foveal fixation in both eyes.
CONCLUSION—A hypothesis is put forward that for the patients described, a period of normal development is likely to have preceded the onset of microtropia, during which the retinocortical "foundations" for NRC were established. Precise pairing of foveo-foveal receptive fields was not abolished by the presence of amblyopia and a central scotoma, but this relation was temporarily suspended and binocular single vision was sustained via the neural substrate of paired receptive fields over a wide retinocortical area.

Keywords: anomalous retinal correspondence; stereoacuity; retinocortical connections     

RA/DA cumulative curve analysis of local and diffuse neuroretinal rim area damage in glaucoma patients

AIM—To evaluate the validity of cumulative rim/disc area (RA/DA) curve analysis as a clinical tool for the identification of glaucoma induced optic disc pathology.
METHODS—71 normal and 83 glaucomatous eyes were evaluated from a series of 154 subjects recruited for this study. For each eye, the cumulative distribution of RA/DA was calculated from 36 equally spaced rim sectors of each optic disc obtained by the automatic evaluation of simultaneous videographics (Image-net X Rev.3/51b). To increase the sensitivity of this analysis in early glaucoma and in normal eyes, these cumulative curves were subsequently divided into two equal segments and the slopes of their respective regression lines compared.
RESULTS—The median RA/DA value obtained from the 36 sectors was significantly different in glaucomatous eyes compared with normals (p <0.001). Nevertheless, the curves (5th-95th percentile of the cumulative curves distribution) of early glaucomatous eyes fell within the normal range. When the cumulative curve of these marginal cases was then divided into two equal segments, the comparison of the slopes of the regression lines showed a significant difference (p <0.05) in 100% of early glaucomatous eyes. Furthermore, normal eyes were shown to be true negatives in 93% of the cases in which no significant difference between the two slopes was observed.
CONCLUSION—Analysis of the RA/DA cumulative curve from 36 sectors of the optic disc was a valid method for the identification of glaucomatous disc pathology; however, a further calculation of the slopes of the two RA/DA regression lines was needed to identify early glaucomatous damage.

Keywords: glaucoma; optic disc morphometry; rim/disc area cumulative curves