The amblyopia treatment study visual acuity testing protocol

Amblyopia characterization, treatment, and prophylaxis

Amblyopia has a 1.6-3.6% prevalence, higher in the medically underserved. It is more complex than simply visual acuity loss and the better eye has sub-clinical deficits. Functional limitations appear more extensive and loss of vision in the better eye of amblyopes more prevalent than previously thought. Amblyopia screening and treatment are efficacious, but cost-effectiveness concerns remain. Refractive correction alone may successfully treat anisometropic amblyopia and it, minimal occlusion, and/or catecholamine treatment can provide initial vision improvement that may improve compliance with subsequent long-duration treatment. Atropine penalization appears as effective as occlusion for moderate amblyopia, with limited-day penalization as effective as full-time. Cytidin-5'-diphosphocholine may hold promise as a medical treatment. Interpretation of much of the amblyopia literature is made difficult by: inaccurate visual acuity measurement at initial visit, lack of adequate refractive correction prior to and during treatment, and lack of long-term follow-up results. Successful treatment can be achieved in at most 63-83% of patients. Treatment outcome is a function of initial visual acuity and type of amblyopia, and a reciprocal product of treatment efficacy, duration, and compliance. Age at treatment onset is not predictive of outcome in many studies but detection under versus over 2-3 years of age may be. Multiple screenings prior to that age, and prompt treatment, reduce prevalence. Would a single early cycloplegic photoscreening be as, or more, successful at detection or prediction than the multiple screenings, and more cost-effective? Penalization and occlusion have minimal incidence of reverse amblyopia and/or side-effects, no significant influence on emmetropization, and no consistent effect on sign or size of post-treatment changes in strabismic deviation. There may be a physiologic basis for better age-indifferent outcome than tapped by current treatment methodologies. Infant refractive correction substantially reduces accommodative esotropia and amblyopia incidence without interference with emmetropization. Compensatory prism, alone or post-operatively, and/or minus lens treatment, and/or wide-field fusional amplitude training, may reduce risk of early onset esotropia. Multivariate screening using continuous-scale measurements may be more effective than traditional single-test dichotomous pass/fail measures. Pigmentation may be one parameter because Caucasians are at higher risk for esotropia than non-whites.

A randomized pilot study of near activities versus non-near activities during patching therapy for amblyopia

BACKGROUND

To plan a future randomized clinical trial, we conducted a pilot study to determine whether children randomized to near or non-near activities would perform prescribed activities. A secondary aim was to obtain a preliminary estimate of the effect of near versus non-near activities on amblyopic eye visual acuity, when combined with 2 hours of daily patching.

METHODS

Sixty-four children, 3 to less than 7 years of age, with anisometropic, strabismic, or combined amblyopia (20/40 to 20/400) were randomly assigned to receive either 2 hours of daily patching with near activities or 2 hours of daily patching without near activities. Parents completed daily calendars for 4 weeks recording the activities performed while patched and received a weekly telephone call in which they were asked to describe the activities performed during the previous 2 hours of patching. Visual acuity was assessed at 4 weeks.

RESULTS

The children assigned to near visual activities performed more near activities than those assigned to non-near activities (by calendars, mean 1.6 +/- 0.5 hours versus 0.2 +/- 0.2 hours daily, P < 0.001; by telephone interviews, 1.6 +/- 0.4 hours versus 0.4 +/- 0.5 hours daily, P < 0.001). After 4 weeks of treatment, there was a suggestion of greater improvement in amblyopic eye visual acuity in those assigned to near visual activities (mean 2.6 lines versus 1.6 lines, P = 0.07). The treatment group difference in visual acuity was present for patients with severe amblyopia but not moderate amblyopia.

CONCLUSIONS

Children patched and instructed to perform near activities for amblyopia spent more time performing those near activities than children who were instructed to perform non-near activities. Our results suggest that performing near activities while patched may be beneficial in treating amblyopia. Based on our data, a formal randomized amblyopia treatment trial of patching with and without near activities is both feasible and desirable.

Amblyopia treatment studies

PURPOSE OF REVIEW

Amblyopia continues to be a major cause of vision loss in children. Several different treatment modalities exist. Research in the field of amblyopia has been very active over the past few years, and clinical practice patterns are changing.

RECENT FINDINGS

Atropine has been found to be effective in the treatment of amblyopia. Less intense patching regimens have been found to be effective as well. Many other aspects of amblyopia therapy are being investigated.

SUMMARY

Herein are current reviews of the major clinical amblyopia studies. Various treatment options are reviewed, and controversies in the field are discussed.

Comparison of visual acuity levels in pediatric patients with amblyopia using Wright figures, Allen optotypes, and Snellen letters

PURPOSE

To compare and correlate the clinical performance of Wright figures in visual acuity assessments of pediatric patients with amblyopia to those obtained through Allen cards and Snellen letters.

SUBJECTS AND METHODS

Best-corrected visual acuity of 26 amblyopic children were measured with the Wright figures(c), Snellen letters, and isolated Allen optotypes, respectively. Amblyopia was defined as two lines of visual acuity difference or a visual acuity level of 20/30 or lower as determined by Snellen chart. The results were evaluated for statistical intergroup differences using the Wilks' Lambda multivariate analysis of variance and for correlation using the Pearson correlation coefficient test.

RESULTS

The mean age of the subjects was 8.27 +/- 2.46 years (range: 5 to 15 years). The mean logMAR values for the Wright figures(c), Snellen letters, and Allen optotypes were 0.40 +/- 0.20, 0.47 +/- 0.23, and 0.29 +/- 0.28, respectively. When compared with Snellen letters, the Wright figures correlated to a higher degree ( r = 0.46, P < 0.001) than Allen optotypes ( r = 0.67, P < 0.001). With a visual acuity of 20/40 or worse on Snellen letter testing, the sensitivity of Wright figures(c) and Allen cards in diagnosing amblyopic eyes was 87.0 and 56.5%, respectively ( P = 0.016).

CONCLUSIONS

Wright figures, designed primarily to evaluate the vision in the preliterate pediatric population, correlate more closely to Snellen letters and have a higher rate of correctly identifying amblyopia than isolated Allen optotypes in pediatric patients.

Testing distance stereoacuity with the Frisby-Davis 2 (FD2) test

PURPOSE

To develop a presentation protocol for the new Frisby-Davis 2 (FD2) distance stereoacuity test.

DESIGN

Prospective data collection.

METHODS

Stereoacuity was tested monocularly and binocularly in 95 patients with a variety of strabismic and nonstrabismic conditions, using the FD2, employing a modified staircase procedure. The Preschool Randot Stereoacuity test and the near Frisby test were used to determine whether a patient was stereoblind.

RESULTS

Under monocular conditions, 35 (37%) of 95 patients passed at least the largest disparity of the FD2 indicating a problem with monocular cues. The binocular protocol was then modified to include a monocular test phase. Using the new protocol, if a patient could achieve the same stereoacuity under monocular and binocular conditions, they were deemed to have no stereopsis. Testing 28 additional stereoblind patients using the new modified protocol revealed no false positives.

CONCLUSION

The FD2 stereotest is a useful measure of distance stereoacuity, provided the presentation protocol accounts for monocular cues.

Effects of extraocular muscle surgery on 15 patients with oculo-cutaneous albinism (OCA) and infantile nystagmus syndrome (INS)

PURPOSE

The purpose of this report is to characterize the clinical and electrophysiological effects of extraocular muscle surgery in 15 patients with oculo-cutaneous albinism (OCA) and infantile nystagmus syndrome (INS). Our hypothesis is that surgery on the extraocular muscles of patients with OCA and INS changes their nystagmus and their visual function.

DESIGN

Interventional, prospective, cohort, noncomparative case series.

METHODS

All 15 patients had surgery on all four virgin horizontal recti; three for strabismus alone, three for nystagmus alone, five for an eccentric gaze null zone alone, and four for an eccentric gaze null zone plus strabismus. All patients have been followed for at least six months. All 15 patients had the subjective outcome measure of pre- and postoperative binocular best optically corrected acuity (BBOCA). Objective outcome measures included anomalous head posture (AHP) in nine patients, eye movement recording measures of expanded nystagmus acuity function (NAFX) in 10 patients, null zone position (NUZP) and null zone width (NUZW) in 10 patients, and foveation time (FOV) in nine patients.

RESULTS

The results are summarized as follows; BBOCA increased 0.1 LogMar or greater in 14 of 15 patients. In those operated on for an AHP with or without associated strabismus the AHP improved significantly (P < .01 for all). The NAFX, NUZP, NUZW, and FOV measured from eye movement recordings showed persistent, significant increases in all patients (P < .01 for all).

CONCLUSIONS

This report adds to the evidence that surgery on the extraocular muscles in patients with INS has independent neurologic and visual results.

Risk factors for treatment failure of anisometropic amblyopia

PURPOSE

This study sought to explore factors which might predict the lack of vision improvement following therapy of anisometropic amblyopia.

METHODS

We retrospectively reviewed the records of 104 children aged 3 to 8 years who had anisometropic amblyopia with a difference in the refractive power between the two eyes of at least 1 diopter, a difference in corrected visual acuity between the two eyes of at least 3 logMAR units, visual acuity in the amblyopic eye of 20/50 or worse, and no ocular structural abnormalities. Patients were treated with either patching or atropine penalization therapy. Patients with strabismus were included. Treatment failure was defined in two ways: (1) functional failure indicating a final visual acuity in the amblyopic eye worse than 20/40 and (2) relative failure indicating less than three lines of logMAR visual acuity improvement regardless of final vision.

RESULTS

Failure risk factors were as follows: age above 6 at the onset of treatment (adjusted odds ratio [OR] (95% confidence limits [CL] = 4.69 [1.55, 14.2]), the presence astigmatism of more than 1.50 diopters in the amblyopic eye (adjusted [OR] (95% CL) = 5.78 [1.27, 26.5]), poor compliance with treatment (adjusted [OR] (95% CL) = 5.47 [1.70, 17.6]), and initial visual acuity in the amblyopic eye of 20/200 or worse (adjusted [OR] (95% CL) = 3.79 [1.28, 11.2]). Strabismus was not found to be a significant risk factor. Neither the type or amount of refractive error nor the difference in the refractive power between the two eyes was a significant risk factor for treatment failure.

CONCLUSION

Eyes with poor initial visual acuity, the presence of significant astigmatism, and age over 6 years were less likely to achieve successful outcome. The clinical profile of patients with anisometropic amblyopia may be useful in predicting response to therapy, but compliance with treatment has a major effect on response to therapy.

Parent-administered visual acuity testing: is it reliable and can it improve office efficiency?

PURPOSE

To evaluate the accuracy of a parent-administered visual acuity test, using the electronic visual acuity tester (EVA) (JAEB Center, Tampa, FL) and evaluate its use as a means to improve efficiency of office acuity testing.

METHODS

This was a prospective experimental study. Part I: Sixty-four children had their visual acuity determined using the EVA, first by their parents and then by an ophthalmic technician. Acuity scores were compared. Part II: Forty-four other children were randomly assigned to one of 2 groups. Group A (parent-prescreen) children had their visual acuity determined first by the parents using the EVA. The visual acuity result in that child was then rechecked by the technician using the Reinforcement Phase and Phase 2 of the Amblyopia Treatment Study (ATS) visual acuity testing protocol. Group B (full ATS protocol) children had their acuity determined by the technician using the full ATS protocol. The number of optotypes presented by the technician in order to determine the acuity in each group was compared.

RESULTS

Part I: Reliability of parent-determined visual acuity scores was high (r = 0.91 and 0.81 for right eyes (OD) and left eyes (OS), respectively), with 93% of right eye parent scores and 85% of left eye parent scores within 0.11 logarithm of minimal angle of resolution (logMAR) units (ie, within one line of vision) of the technician score. Part II: The parent prescreen group (Group A) required presentation of 66% fewer optotypes to the OD and 68% fewer optotypes to the OS than the full ATS protocol group (Group B) (OD: P = 5.4 x 10(-18); OS: P = 6.5 x 10(-18)).

CONCLUSIONS

Visual acuity testing results by parents using the EVA are reliable. Electronic visual acuity prescreening by parents reduces the number of optotype presentations required to be shown by the technician to accurately determine acuity. Use of a parent-assisted screening system in the waiting room may translate to increased office efficiency.

The Electronic Visual Acuity Tester: Testability in Preschool Children

PURPOSE

To evaluate the ability of preschool children to have their threshold visual acuity assessed using a standardized, computer-based letter test.

METHODS

Participants were 1195 3.5- to 5-year-old children enrolled in the Vision in Preschoolers Study. Monocular visual acuity was assessed by licensed eye care professionals (optometrists and pediatric ophthalmologists experimented in the examination of children), using the Electronic Visual Acuity tester, which uses the letters H, O, T, and V with a crowded surround.

RESULTS

Overall, 99.1% of children passed the training that consisted of identifying the letters H, O, T, and V by naming or matching the letters at 60 cm. Among those who passed the training, 99.6% completed the binocular pretest at 3 m, and 97.6% of those passing the training and the pretest completed monocular threshold visual acuity testing of each eye with the Electronic Visual Acuity tester. Testability increased with age for training (p = 0.03), pretesting (p = 0.04), and acuity testing (p = 0.07). Overall, 93.3% of 3.5-year-olds, 96.7% of 4-year-olds, and 98.8% of 5-year-olds completed training, pretesting, and monocular threshold acuity testing of each eye using standard letter optotypes.

CONCLUSION

Using the computer-based Electronic Visual Acuity system, nearly all 3.5- to 5-year-old children can complete monocular acuity testing of each eye.

Comparison of the amblyopia treatment study HOTV and electronic-early treatment of diabetic retinopathy study visual acuity protocols in children aged 5 to 12 years

PURPOSE

To compare two established visual acuity protocols: the Amblyopia Treatment Study HOTV (ATS HOTV) visual acuity protocol and the Electronic-Early Treatment of Diabetic Retinopathy Study (E-ETDRS) protocol, in children aged 5 to 12 years.

DESIGN

Prospective cohort study.

METHODS

Crowded HOTV optotypes and crowded ETDRS optotypes were presented to 236 consecutive children aged 5 to 12 years using an electronic visual acuity tester (Palm handheld, personal computer, and monitor). Twenty-three percent of the children were classified as amblyopic, 35% as having uncorrected refractive error, 36% as normal, and 6% as other. Visual acuity test results were converted to logarithm of minimal angle of resolution (logMAR) units for analysis.

RESULTS

In developmentally normal children (n = 230), testability was 100% for HOTV in 5- to 12-year-olds and 100% for E-ETDRS in 7- to 12-year-olds. The E-ETDRS testing could be completed in 52% of 5-year-olds and in 87% of 6-year-olds. Visual acuity performance was better when measured by HOTV compared with E-ETDRS (median difference 0.06 logMAR [three letters on a chart with five letters/line], P =.0001), and the difference was found in normal eyes, eyes with refractive error, and amblyopic eyes.

CONCLUSIONS

The ATS HOTV protocol yields slightly better visual acuity performance compared with E-ETDRS in 5- to 12-year-olds, but on average by less than a logMAR level. This systematic difference is important when a physician changes testing modality as a child matures and should be considered when interpreting the results of recent and ongoing clinical trials in amblyopia.

Altered global shape discrimination in deprivation amblyopia

To assess the effect of deprivation amblyopia on global shape discrimination, sensitivity to radial deformation of circular patterns was assessed in patients treated for congenital (N=7) or developmental (N=1) cataracts. Elevation in radial deformation threshold was dependent on circular contour frequency and the depth of amblyopia. Analysis of thresholds expressed as Weber fractions indicated a shift in global integration to a larger scale. In a pedestal experiment, equivalent intrinsic noise increased in proportion to the depth of amblyopia. The results suggest neural undersampling in V1 and/or higher visual cortical areas in deprivation amblyopia and a possible role for neural disarray.

Threshold visual acuity testing of preschool children using the crowded HOTV and Lea Symbols acuity tests

PURPOSE

To compare the testability and threshold acuity levels for very young children on the crowded HOTV logMAR distance visual acuity test presented on the BVAT apparatus and the Lea Symbols logMAR distance visual acuity chart.

METHODS

Subjects were 87 Head Start children from age 3 to 3.5 years. Testing consisted of binocular pretraining at near using a lap card as needed, binocular pretraining at 3 m, and threshold testing for each eye. The testing procedure, adapted from the Amblyopia Treatment Study, presented optotypes until the child was unable to correctly name or match three of three or three of four optotypes of a given size. Threshold acuity was the smallest size for which at least three optotypes were correctly identified.

RESULTS

Both near and distance pretraining were completed by 71% of children for HOTV and by 75% for Lea Symbols (P =.39). The distribution of threshold acuities differed between the two tests. For the 69 eyes of 53 children who were successfully tested with both optotypes, results from the crowded HOTV acuity test were on average 0.25 logMar (2.5 lines) better than those from the Lea Symbols acuity test (P <.001).

CONCLUSIONS

The proportion of children between 3 and 3.5 years of age whose monocular visual acuity could be assessed was high and was similar for the two charts tested. Crowded HOTV acuity results were better on average than results using Lea symbols. The different formats of the two tests may explain the observed differences in threshold acuity level.

The accuracy of the amblyopia treatment study visual acuity testing protocol

PURPOSE

To study the accuracy of the newly proposed Amblyopia Treatment Study (ATS) visual acuity testing protocol for 3- to 6-year-old children. Because no "gold standard" is available for acuity testing in pediatric patients, accuracy was evaluated using computer simulations based on a psychometric model.

METHODS

Monte Carlo simulations of ATS acuity data were generated using a psychometric model that accounts for true acuity, noise in the visual system, and the rate of inadvertent misses. We varied true acuity from 20/15 to 20/400 (-0.1 to 1.3 logMAR). Visual system noise was represented by the slope beta of the psychometric function and ranged from 1 (noisy) to 8 (not noisy). The rate of inadvertent misses ranged from 0% to 10%. Accuracy of the ATS protocol was evaluated in terms of precision, bias, and stimulus range limitations. The same model was fitted to experimental ATS acuity data, thus allowing us to study the distributions of acuity, visual system noise, and level of attentiveness in 126 children ages 3 to <7 years.

RESULTS

For conditions with little noise in the visual system (beta > 2), precision was well within 0.1 logMAR (corresponding to one line on a logMAR letter chart), except for acuities worse than 1.2 logMAR, and decreased to 0.15 to 0.2 logMAR for beta = 1. Bias was negligible, except in noisy conditions, where the ATS protocol tended to overestimate acuity by one line at the poor end of the true acuity range and underestimate acuity at the good end of the true acuity range. Effects of the rate of inadvertent misses were small. Fits to the real data showed a wide range of slope parameters, but only 11% had beta < or = 2. The rate of inadvertent misses was < or = 2% in 89% of cases.

CONCLUSION

The simulations suggest that the ATS protocol offers an accurate method for assessing visual acuity in children in the range of 3 to 6 years of age with both precision and bias within 0.1 logMAR for typical values of the psychometric parameters.

A randomized trial of prescribed patching regimens for treatment of severe amblyopia in children

OBJECTIVE

To compare full-time patching (all hours or all but 1 hour per day) to 6 hours of patching per day, as prescribed treatments for severe amblyopia in children younger than 7 years.

DESIGN

Prospective, randomized multicenter clinical trial (32 sites).

PARTICIPANTS

One hundred seventy-five children younger than 7 years with amblyopia in the range of 20/100 to 20/400.

INTERVENTION

Randomization either to full-time patching or to 6 hours of patching per day, each combined with at least 1 hour of near-visual activities during patching.

MAIN OUTCOME MEASURE

Visual acuity in the amblyopic eye after 4 months.

RESULTS

Visual acuity in the amblyopic eye improved a similar amount in both groups. The improvement in the amblyopic eye acuity from baseline to 4 months averaged 4.8 lines in the 6-hour group and 4.7 lines in the full-time group (P = 0.45).

CONCLUSION

Six hours of prescribed daily patching produces an improvement in visual acuity that is of similar magnitude to the improvement produced by prescribed full-time patching in treating severe amblyopia in children 3 to less than 7 years of age.

The course of moderate amblyopia treated with atropine in children: experience of the amblyopia treatment study

PURPOSE

To assess the course of the response to atropine treatment of moderate amblyopia and to assess factors predictive of the treatment response in children 3 years old to younger than 7 years old.

DESIGN

Multicenter, randomized clinical trial comparing atropine and patching (one of the amblyopia treatment studies).

METHODS

A total of 195 children 3 years old to younger than 7 years of age with amblyopia in the range of 20/40 to 20/100 from the atropine treatment arm of this trial were enrolled and included in this analysis. At baseline, daily topical atropine was prescribed for the sound eye. During follow-up, a plano spectacle lens was prescribed for the sound eye for patients whose amblyopia had not been successfully treated with atropine alone. Follow-up examinations were performed at 5 weeks, 16 weeks, and 6 months. The primary outcome measure was visual acuity in the amblyopic eye at 6 months.

RESULTS

Mean visual acuity improved from baseline by 1.3 lines after 5 weeks of treatment, by 2.4 lines after 16 weeks, and by 2.8 lines at 6 months. Visual acuity of 20/30 or better and/or 3 or more lines of improvement from baseline was achieved by 75% of the patients. Improvement occurred over the entire range of baseline acuities (20/40 to 20/100) and was not related to patient age (P =.36). Among the 134 patients improving 3 or more lines from baseline, 7% achieved their maximum improvement by 5 weeks and 46% by 16 weeks. Among the 55 patients who did not respond adequately to atropine alone and were prescribed a plano lens for the sound eye, the mean improvement before the use of the plano lens was 1.0 lines, compared with 1.6 lines after prescribing the plano lens (P =.11). None of the demographic or clinical factors assessed was predictive of the response to treatment. A shift in fixation preference at/near from the atropinized sound eye to the amblyopic eye was not required for the amblyopic eye to improve; amblyopic eye acuity improved 3 or more lines in 29 (60%) of the 48 patients who were found to be using the atropinized sound eye on fixation preference testing. A 2 or more line decrease in sound eye visual acuity occurred more frequently when a plano lens was prescribed in addition to atropine (7 of 43, 16%) compared with treatment with atropine alone (4 of 123, 3%; P =.01).

CONCLUSIONS

A beneficial effect of atropine is present throughout the age range of 3 years old to younger than 7 years old, and with an acuity range of 20/40 to 20/100. A shift in near fixation to the amblyopic eye is not essential for atropine to be effective in all cases. Sound eye acuity should be monitored when a plano spectacle lens is prescribed for the sound eye to augment the treatment effect of atropine.

The course of moderate amblyopia treated with patching in children: experience of the amblyopia treatment study

PURPOSE

To assess the course of the response to patching treatment of moderate amblyopia and to assess factors predictive of the response in children 3 years old to younger than 7 years old.

DESIGN

Multicenter, randomized clinical trial comparing patching and atropine (one of the amblyopia treatment studies).

METHODS

A total of 209 children 3 years old to younger than 7 years of age with amblyopia in the range of 20/40 to 20/100 from the patching treatment arm of this trial were treated with patching of the sound eye from 6 hours per day up to all waking hours. Follow-up examinations were performed at 5 weeks, 16 weeks, and 6 months. The primary outcome measure was visual acuity in the amblyopic eye at 6 months.

RESULTS

After 5 weeks of treatment, mean amblyopic eye acuity improved from baseline by 2.2 lines. For patients with baseline acuity of 20/80 or 20/100, a greater number of hours of prescribed patching was associated with greater improvement in the first 5 weeks (P =.05). However, this relationship was not present when baseline acuity was 20/40 to 20/60 (P =.57). At 6 months, visual acuity was improved from baseline by a mean of 3.1 lines, with the amount of improvement no longer related to the number of hours patching prescribed at baseline (P =.93). Among the 157 patients improving at least 3 lines from baseline, 15% achieved their maximum improvement by 5 weeks and 52% by 16 weeks. None of the demographic or clinical factors assessed was predictive of the response to treatment.

CONCLUSIONS

In the treatment of moderate amblyopia, a beneficial effect of patching is present throughout the age range of 3 years old to younger than 7 years old and the acuity range of 20/40 to 20/100. At 6 months, the amount of improvement appears to be similar when 6 hours of daily patching are initially prescribed vs a greater number of hours. However, when the baseline acuity is 20/80 to 20/100, a greater number of hours of prescribed patching may improve acuity faster.

A comparison of atropine and patching treatments for moderate amblyopia by patient age, cause of amblyopia, depth of amblyopia, and other factors

OBJECTIVE

To assess whether the relative treatment effect of patching compared with atropine for moderate amblyopia varies according to patient age, cause of amblyopia or depth of amblyopia, and initial number of patching hours prescribed.

DESIGN

Multicenter, randomized clinical trial.

PARTICIPANTS

Four hundred nineteen children younger than 7 years of age with amblyopia in the range of 20/40 to 20/100.

METHODS

Patients were assigned randomly to receive treatment with either patching or atropine and followed up for 6 months.

PRIMARY OUTCOME MEASURE

Single-surrounded HOTV optotype visual acuity in the amblyopic eye after 6 months.

RESULTS

Improvement in the amblyopic eye visual acuity was slightly greater in the patching group compared with the atropine group in all subgroups based on patient characteristics. The relative treatment effect did not vary with age (P = 0.84), cause of amblyopia (P = 0.68), or baseline amblyopic eye acuity (P = 0.59). Patients with acuity of 20/80 to 20/100 who were prescribed 10 or more hours a day of patching showed a more rapid improvement in acuity than did patients prescribed a lesser amount of patching (P = 0.01) or than did patients in the atropine group (P < 0.001), but by 6 months, the differences were not significant (P = 0.47 and 0.15, respectively).

CONCLUSIONS

A beneficial effect of both patching and atropine is present throughout the age range of 3 to younger than 7 years old and the acuity range of 20/40 to 20/100. Patients with acuity of 20/80 to 20/100 improve faster when a greater number of hours of patching is prescribed, but by 6 months, the amount of improvement is not related to the number of hours of patching initially prescribed.

A computerized method of visual acuity testing: adaptation of the early treatment of diabetic retinopathy study testing protocol

PURPOSE

To develop a computerized method of visual acuity testing for clinical research as an alternative to the standard Early Treatment for Diabetic Retinopathy Study (ETDRS) testing protocol, and to evaluate its test-retest reliability and concordance with standard ETDRS testing.

DESIGN

Test-retest reliability study.

METHODS

Multicenter setting of a study population of 265 patients at three clinical sites. Visual acuity was measured with both the electronic visual acuity testing algorithm (E-ETDRS) and standard ETDRS protocol (S-ETDRS) twice on one eye of each patient. E-ETDRS testing was conducted using the electronic visual acuity tester (EVA), which utilizes a programmed Palm (Palm, Inc, Santa Clara, California, USA) hand-held device communicating with a personal computer and 17-inch monitor at a test distance of 3 meters.

RESULTS

For the E-ETDRS protocol, test-retest reliability was high (r = 0.99; with 89% and 98% of retests within 0.1 logMAR and 0.2 logMAR of initial tests, respectively) and comparable with that of S-ETDRS testing (r = 0.99; with 87% and 98% of retests within 0.1 logMAR and 0.2 logMAR of initial test, respectively). The E-ETDRS and S-ETDRS scores were highly correlated (r = 0.96 for initial tests and r = 0.97 for repeat tests). Based on estimates of 95% confidence intervals, a change in visual acuity of 0.2 logMAR (10 letters) from a baseline level is unlikely to be related to measurement variability using either the E-ETDRS or the S-ETDRS visual acuity testing protocol.

CONCLUSIONS

The E-ETDRS protocol has high test-retest reliability and good concordance with S-ETDRS testing. The computerized method has advantages over the S-ETDRS testing in electronically capturing the data for each tested letter, requiring only a single distance for testing from 20/12 to 20/800, potentially reducing testing time, and potentially decreasing technician-related bias.

Clinical research in pediatric ophthalmology: the Pediatric Eye Disease Investigator Group

The Pediatric Eye Disease Investigator Group (PEDIG) is a network of university-based and community-based pediatric eye care practitioners that is conducting multiple clinical research studies. The group has conducted the Congenital Esotropia Observational Study, which assessed the early course of esotropia in infants, and the Amblyopia Treatment Studies, a series of randomized trials, the first of which compared atropine and patching for treatment of moderate amblyopia in children 3 to <7 years old. Herein, the results of these studies are summarized, and the current and future studies of the group are described.

Amblyopia treatment outcomes after screening before or at age 3 years: follow up from randomised trial

OBJECTIVE

To assess the effectiveness of early treatment for amblyopia in children.

DESIGN

Follow up of outcomes of treatment for amblyopia in a randomised controlled trial comparing intensive orthoptic screening at 8, 12, 18, 25, 31, and 37 months (intensive group) with orthoptic screening at 37 months only (control group).

SETTING

Avon, southwest England.

PARTICIPANTS

3490 children who were part of a birth cohort study.

MAIN OUTCOME MEASURES

Prevalence of amblyopia and visual acuity of the worse seeing eye at 7.5 years of age.

RESULTS

Amblyopia at 7.5 years was less prevalent in the intensive group than in the control group (0.6% v 1.8%; P=0.02). Mean visual acuities in the worse seeing eye were better for children who had been treated for amblyopia in the intensive group than for similar children in the control group (0.15 v 0.26 LogMAR units; P<0.001). A higher proportion of the children who were treated for amblyopia had been seen in a hospital eye clinic before 3 years of age in the intensive group than in the control group (48% v 13%; P=0.0002).

CONCLUSIONS

The intensive screening protocol was associated with better acuity in the amblyopic eye and a lower prevalence of amblyopia at 7.5 years of age, in comparison with screening at 37 months only. These data support the hypothesis that early treatment for amblyopia leads to a better outcome than later treatment and may act as a stimulus for research into feasible screening programmes.

Darkness and near work: myopia and its progression in third-year law students

PURPOSE

To evaluate myopia prevalence, myopia progression, and various potential myopia risk factors in third-year law students.

DESIGN

Cross-sectional study and survey.

PARTICIPANTS

One hundred seventy-nine third-year law students at the University of Pennsylvania.

METHODS

We administered a questionnaire to assess the prevalence of myopia, myopia progression, and risk factors, including near work, family history, and daily light/dark exposure. We conducted a screening eye examination to ascertain myopia status. Myopia was defined as the mean spherical equivalent of the two eyes of </=-0.5 diopters; myopia progression was defined by the self-reported need for a stronger eyeglass prescription during law school.

MAIN OUTCOME MEASURES

(1) prevalence of myopia, (2) progression of myopia.

RESULTS

Seventy-nine percent of the class participated (n = 179, two were excluded for amblyopia leaving 177 students). Fifty-eight percent were male, 75% were Caucasian, and the mean age was 27 years. Seventy-nine percent reported parental myopia. The mean amount of near work was 7.4 hours/day; mean sleep was 7.9 hours/day; mean darkness was 5.3 hours/day. Sixty-six percent of the students were myopic. Of 96 participants myopic before law school, myopia increased in 83 (86%) during law school. Among 75 students not myopic at the beginning of law school, 14 (19%) became myopic. The onset of myopia could not be determined for 6 patients. There were trends for higher myopia prevalence among those with a parental myopia history (P = 0.14) and for increased myopia progression among those reporting more daily near work (P = 0.18). Students with </=5.6 hours of daily darkness were more likely to report myopia progression than those with >5.6 hours of darkness per day (95% vs. 80%, P = 0.07). To account for possible confounding effects of risk factors with myopia progression, logistic regression with categorization of the continuous exposure variables (hours of near work, sleep, and darkness) above or below median values weakened the near work association (odds ratio 1.8, 95% confidence interval 0.5-6.7, P = 0.35) but continued to identify darkness association with daily hours of darkness (odds ratio 4.8, 95% confidence interval 1.0 >/= 23.3, P < 0.05). Among the 77 students with myopia onset before college, those with </=5.6 hours of daily darkness were more likely to progress than those with more hours of daily darkness (97% vs. 76%, P = 0.01).

CONCLUSIONS

This study confirms high rates of myopia prevalence and myopia progression among law students. The strongest association, especially in those with myopia onset before college, was a relation of myopia progression during law school with less daily exposure to darkness, a potential risk factor previously identified in childhood myopia. The role of exposure to darkness in refractive development warrants additional study.

Computerized method of visual acuity testing: adaptation of the amblyopia treatment study visual acuity testing protocol

PURPOSE

To report a computerized method for determining visual acuity in children using the Amblyopia Treatment Study visual acuity testing protocol.

METHODS

A computerized visual acuity tester was developed that uses a programmed handheld device that uses the Palm operating system (Palm, Inc, Santa Clara, California). The handheld device communicates with a personal computer running a Linux operating system and 17-inch monitor. At a test distance of 3 m, single letters can be displayed from 20/800 to 20/12. A C program on the handheld device runs the Amblyopia Treatment Study visual acuity testing protocol. Using this method, visual acuity was tested in both the right and left eyes, and then the testing was repeated in 156 children age 3 to 7 years at four clinical sites.

RESULTS

Test-retest reliability was high (r =.92 and 0.95 for and right and left eyes, respectively), with 88% of right eye retests and 94% of left eye retests within 0.1 logarithm of minimal angle of resolution (logMAR) units of the initial test. The 95% confidence interval for an acuity score was calculated to be the score +/- 0.13 logMAR units. For a change between two acuity scores, the 95% confidence interval was the difference +/- 0.19 logMAR units.

CONCLUSIONS

We have developed a computerized method for measurement of visual acuity. Automation of the Amblyopia Treatment Study visual acuity testing protocol is an effective method of testing visual acuity in children 3 to 7 years of age.

Early binocular visual experience may improve binocular sensory outcomes in children after surgery for congenital unilateral cataract

PURPOSE

To compare the effect of intensive and reduced occlusion therapy regimens on binocular sensory outcomes, visual acuity, and the prevalence of strabismus in children after surgery for congenital unilateral cataract.

METHODS

Two nonrandomized groups of patients were studied prospectively: (1) an intensive occlusion group (n = 29) patched 80% of waking hours were followed for a median 6.9 years and (2) a reduced occlusion group (n = 8) patched 25% to 50% of waking hours were followed for a median 4.3 years. Six subjects in the intensive group and 4 in the reduced occlusion group had secondary intraocular lenses. Two subjects in the intensive group had epikeratophakia surgery. Binocular sensory function was assessed with random dot and contour stereoacuity tests and the Worth 4-dot test. The prevalence and age at onset of strabismus were determined from the patients' charts.

RESULTS

A higher proportion of subjects in the reduced occlusion group (50%) had stereoacuity or fusion compared with the intensive occlusion group (14%), a borderline significant difference (P =.08). No significant difference (P =.55) was found in median visual acuity between the intensive (20/50) and the reduced occlusion (20/55) groups. The 90% prevalence of strabismus in the intensive occlusion group was slightly higher than the 63% prevalence in the reduced occlusion group, although this difference was not significant (P =.18).

CONCLUSIONS

These results suggest that a reduced occlusion protocol may be associated with better binocular sensory outcomes and a reduced prevalence of strabismus without compromising good visual acuity in children treated for congenital unilateral cataract.

The Amblyopia Treatment Index

OBJECTIVE

To develop a questionnaire to assess the acceptability of amblyopia treatment and its effect on the child and family.

METHODS

A 20-item parental survey was developed and pilot tested on 64 subjects, aged 3 to 6 years, participating in the Amblyopia Treatment Study, a randomized trial comparing patching and atropine as treatments for moderate amblyopia. The survey was administered after 4 weeks of treatment. A descriptive item analysis and an internal consistency reliability analysis were performed.

RESULTS

Nineteen of the 20 items demonstrated adequate variability as evidenced by the frequency distributions for item responses. Only 4 (<1%) of 1280 possible item responses were missing, one each by 4 different respondents. Factor analysis identified 3 treatment-related factors--"adverse effects," "compliance," and "social stigma"--among 11 of the 20 items. The internal-consistency reliability alpha for the 5-item adverse effects subscale was 0.82, the 4-item compliance subscale alpha was 0.81, and the 2-item social stigma subscale alpha was 0.84.

CONCLUSIONS

The Amblyopia Treatment Index appears to be a useful instrument for assessing the impact of amblyopia treatment in 3- to 6-year-old children.