Design of the Monitored Occlusion Treatment of Amblyopia Study (MOTAS)

Advanced Visualization Engineering for Vision Disorders: A Clinically Focused Guide to Current Technology and Future Applications

Head-mounted visualization technology, often in the form of virtual, augmented, and mixed reality (VAMR), has revolutionized how visual disorders may be approached clinically. In this manuscript, we review the available literature on VAMR for visual disorders and provide a clinically oriented guide to how VAMR technology has been deployed for visual impairments. The chief areas of clinical investigation with VAMR are divided include (1) vision assessment, (2) vision simulation, and (3) vision rehabilitation. We discuss in-depth the current literature of these areas in VAMR and upcoming/future applications to combat the detrimental impact of visual impairment worldwide.

Factors affecting the benefit of glasses alone in treating childhood amblyopia: an analysis of PEDIG data

BACKGROUND

To evaluate factors associated with better outcomes from optical treatment alone in amblyopic children from 3 up to 7 years.

METHODS

Data extracted from two studies with similar protocols, Amblyopic Treatment Studies 5 (n = 152) and 13 (n = 128) from the Pediatric Eye Disease Investigator Group database, were used to determine by regression analysis the factors associated with improvements in visual acuity in the amblyopic eye, inter-ocular visual acuity difference and stereoacuity. Input variables were aetiology of amblyopia (anisometropic, strabismic and combined-mechanism amblyopia), treatment compliance, visual acuity, interocular visual acuity difference, stereoacuity, tropia size at distance and near, age and refractive error at baseline.

RESULTS

Despite the range of clinical factors considered, our models explain only a modest proportion of the variance in optical treatment outcomes. The better predictors of the degree of optical treatment success in amblyopic children are visual acuity of the amblyopic eye, interocular visual acuity difference, stereoacuity, treatment compliance and the amblyopic eye spherical-equivalent refractive error. While the aetiology of the amblyopia does not exert a major influence upon treatment outcome, combined-mechanism amblyopes experience the smallest improvement in visual acuity, tropia and stereoacuity and may need longer optical treatment periods.

CONCLUSIONS

While results identify the factors influencing optical treatment outcome in amblyopic children, clinicians will be unable to predict accurately the benefits of optical treatment in individual patients. Whether this is because relevant clinical or non-clinical factors (e.g. nature and volume of daily activities undertaken) influences the outcomes from optical treatment has not yet been identified and remains to be discovered.

Binocular versus standard occlusion or blurring treatment for unilateral amblyopia in children aged three to eight years

BACKGROUND

Current treatments for amblyopia, typically patching or pharmacological blurring, have limited success. Less than two-thirds of children achieve good acuity of 0.20 logMAR in the amblyopic eye, with limited improvement of stereopsis, and poor adherence to treatment. A new approach, based on presentation of movies or computer games separately to each eye, may yield better results and improve adherence. These treatments aim to balance the input of visual information from each eye to the brain.  OBJECTIVES: To determine whether binocular treatments in children, aged three to eight years, with unilateral amblyopia result in better visual outcomes than conventional patching or pharmacological blurring treatment.

SEARCH METHODS

We searched CENTRAL (which contains the Cochrane Eyes and Vision Trials Register), MEDLINE, Embase, ISRCTN, ClinicalTrials.gov, and the WHO ICTRP to 19 November 2020, with no language restrictions.

SELECTION CRITERIA

Two review authors independently screened the results of the search for relevant studies. We included randomised controlled trials (RCTs) that enrolled children between the ages of three and eight years old with unilateral amblyopia. Amblyopia was classed as present when the best-corrected visual acuity (BCVA) was worse than 0.200 logMAR in the amblyopic eye, with BCVA 0.200 logMAR or better in the fellow eye, in the presence of an amblyogenic risk factor, such as anisometropia, strabismus, or both. To be eligible, children needed to have undergone cycloplegic refraction and  ophthalmic examination, including fundal examination and optical treatment, if indicated, with stable BCVA in the amblyopic eye despite good adherence with wearing glasses. We included any type of binocular viewing intervention, on any device (e.g. computer monitors viewed with liquid-crystal display shutter glasses; hand-held screens, including mobile phones with lenticular prism overlay; or virtual reality displays). Control groups received standard amblyopia treatment, which could include patching or pharmacological blurring of the better-seeing eye. We included full-time (all waking hours) and part-time (between 1 and 12 hours a day) patching regimens. We excluded children who had received any treatment other than optical treatment; and studies with less than 8-week follow-up.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane. The primary outcome of the review was the change from baseline of distance BCVA in the amblyopic eye after 16 (± 2) weeks of treatment, measured in logMAR units on an age-appropriate acuity test.

MAIN RESULTS

We identified one eligible RCT of conventional patching treatment versus novel binocular treatment, and analysed a subset of 68 children who fulfilled the age criterion of this review. We obtained data for the mean change in amblyopic eye visual acuity, adverse events (diplopia), and adherence to prescribed treatment at 8- and 16-week follow-up intervals, though no data were available for change in BCVA after 52 weeks. Risk of bias for the included study was considered to be low. The certainty of evidence for the visual acuity outcomes at 8 and 16 weeks of treatment and adherence to the study intervention was rated moderate using the GRADE criteria, downgrading by one level due to imprecision. The certainty of evidence was downgraded by two levels and rated low for the proportion of participants reporting adverse events due to the sample size.  Acuity improved in the amblyopic eye in both the binocular and patching groups following 16 weeks of treatment (improvement of -0.21 logMAR in the binocular group and -0.24 logMAR in the patching group, mean difference (MD) 0.03 logMAR (95% confidence interval (CI) -0.10 to 0.04; 63 children). This difference was non-significant and the improvements in both the binocular and patching groups are also considered clinically similar. Following 8 weeks of treatment, acuity improved in both the binocular and patching groups (improvement of -0.18 logMAR in the patching group compared to -0.16 logMAR improvement in the binocular-treatment group) (MD 0.02, 95% CI -0.04 to 0.08). Again this difference was statistically non-significant, and the differences observed between the patching and binocular groups are also clinically non-significant. No adverse event of permanent diplopia was reported. Adherence was higher in the patching group (47% of participants in the iPad group achieved over 75% compliance compared with 90% of the patching group).  Data were not available for changes in stereopsis nor for contrast sensitivity following treatment.

AUTHORS' CONCLUSIONS

Currently, there is only one RCT that offers evidence of the safety and effectiveness of binocular treatment. The authors are moderately confident that after 16 weeks of treatment, the gain in amblyopic eye acuity with binocular treatment is likely comparable to that of conventional patching treatment. However, due to the limited sample size and lack of long term (52 week) follow-up data, it is not yet possible to draw robust conclusions regarding the overall safety and sustained effectiveness of binocular treatment. Further research, using acknowledged methods of visual acuity and stereoacuity assessment with known reproducibility, is required to inform decisions about the implementation of binocular treatments for amblyopia in clinical practice, and should incorporate longer term follow-up to establish the effectiveness of binocular treatment. Randomised controlled trials should also include outcomes reported by users, adherence to prescribed treatment, and recurrence of amblyopia after cessation of treatment.

Contrast Sensitivity and Stereoacuity in Successfully Treated Refractive Amblyopia

Purpose

To assess whether monocular contrast sensitivity and stereoacuity impairments remain when visual acuity is fully recovered in children with refractive amblyopia.

Methods

A retrospective review of 487 patients diagnosed with refractive amblyopia whose visual acuity improved to 0.08 logMAR or better in both eyes following optical treatment was conducted. Measurements of monocular contrast sensitivity and stereoacuity had been made when visual acuity normalized. All patients had been treated with refractive correction for approximately 2 years following diagnosis. No other treatments were provided. Monocular contrast sensitivity was measured using the CSV-1000E chart for children 6 years of age or younger and a psychophysical technique called the quick contrast sensitivity function in older children. Stereoacuity was measured using the Random Dot Test that includes monocular cues and the Randot Stereoacuity Test that does not have monocular cues.

Results

Statistically significant interocular differences in contrast sensitivity were observed. These differences tended to occur at higher spatial frequencies (12 and 18 cycles per degree). Stereoacuity within the age-specific normal range was achieved by 47.4% of patients for the Random Dot Test and only 23.1% of patients for the Randot Stereoacuity Test.

Conclusions

Full recovery of visual acuity following treatment for refractive amblyopia does not equalize interocular contrast sensitivity or restore normal stereopsis. Alternative therapeutic approaches that target contrast sensitivity and/or binocular vision are required.

Recent Advances in Screening and Treatment for Amblyopia

Amblyopia is the most common cause of monocular visual impairment in children, with a prevalence of 2-3%. Not only is visual acuity reduced in one eye but binocular vision is affected, fellow eye deficits may be present, eye-hand coordination and reading can be affected, and self-perception may be diminished. New technologies for preschool vision screening hold promise for accessible, early, and accurate detection of amblyopia. Together with recent advances in our theoretical understanding of amblyopia and technological advances in amblyopia treatment, we anticipate improved visual outcomes for children affected by this very common eye condition. This article is based on previously conducted studies and does not contain any new studies with human participants or animals performed by any of the authors.

Electronically monitored occlusion therapy in amblyopia with eccentric fixation

Purpose

Amblyopia with eccentric fixation, especially when not diagnosed early, is a therapeutic challenge, as visual outcome is known to be poorer than in amblyopia with central fixation. Consequently, treatment after late diagnosis is often denied. Electronic monitoring of occlusion provides us the chance to gain first focussed insight into age-dependent dose response and treatment efficiency, as well as the shift of fixation in this rare group of paediatric patients.

Methods

In our prospective pilot study, we examined amblyopes with eccentric fixation during 12 months of occlusion treatment. We evaluated their visual acuity, recorded patching duration using a TheraMon®-microsensor, and determined their fixation with a direct ophthalmoscope. Dose-response relationship and treatment efficiency were calculated.

Results

The study included 12 participants with strabismic and combined amblyopia aged 2.9–12.4 years (mean 6.5). Median prescription of occlusion was 7.7 h/day (range 6.6–9.9) and median daily received occlusion was 5.2 h/day (range 0.7–9.7). At study end, median acuity gain was 0.6 log units (range 0–1.6) and residual interocular visual acuity difference (IOVAD) 0.3 log units (range 0–1.8). There was neither significant acuity gain nor reduction in IOVAD after the 6th month of treatment. Children younger than 4 years showed best response with lowest residual IOVAD at study end. Efficiency calculation showed an acuity gain of approximately one line from 100 h of patching in the first 2 months and half a line after 6 months. There was a significant decline of treatment efficiency with age (p = 0.01). Foveolar fixation was achieved after median 3 months (range 1–6). Three patients (> 6 years) did not gain central fixation.

Conclusion

Eccentric fixation is a challenge to therapy success. Based on electronic monitoring, our study quantified for the first time the reduction of treatment efficiency with increasing age in amblyopes with eccentric fixation. Despite some improvement in patients up to 8 years, older patients showed significantly lower treatment efficiency. In younger patients with good adherence, despite poor initial acuity, central fixation and low residual IOVAD could be attained after median 3 months. Hence, the necessity of early diagnosis and intensive occlusion should be emphasized.

Action Fluency Facilitates Perceptual Discrimination

Perception and action interact in nearly every moment of daily life. Previous studies have demonstrated not only that perceptual input shapes action but also that various factors associated with action-including individual abilities and biomechanical costs-influence perceptual decisions. However, it is unknown how action fluency affects the sensitivity of early-stage visual perception, such as orientation. To address this question, we used a dual-task paradigm: Participants prepared an action (e.g., grasping), while concurrently performing an orientation-change-detection task. We demonstrated that as actions became more fluent (e.g., as grasping errors decreased), perceptual-discrimination performance also improved. Importantly, we found that grasping training prior to discrimination enhanced subsequent perceptual sensitivity, supporting the notion of a reciprocal relation between perception and action.

Treatment of Amblyopia Using Personalized Dosing Strategies: Statistical Modelling and Clinical Implementation

PURPOSE

To generate a statistical model for personalizing a patient's occlusion therapy regimen.

METHODS

Statistical modelling was undertaken on a combined data set of the Monitored Occlusion Treatment of Amblyopia Study (MOTAS) and the Randomized Occlusion Treatment of Amblyopia Study (ROTAS). This exercise permits the calculation of future patients' total effective dose (TED)-that predicted to achieve their best attainable visual acuity. Daily patching regimens (hours/day) can be calculated from the TED.

RESULTS

Occlusion data for 149 study participants with amblyopia (anisometropic in 50, strabismic in 43, and mixed in 56) were analyzed. Median time to best observed visual acuity was 63 days (25% and 75% quartiles; 28 and 91 days). Median visual acuity in the amblyopic eye at start of occlusion was 0.40 logMAR (quartiles 0.22 and 0.68 logMAR) and at end of occlusion was 0.12 (quartiles 0.025 and 0.32 logMAR). Median lower and upper estimates of TED were 120 hours (quartiles 34 and 242 hours), and 176 hours (quartiles 84 and 316 hours). The data suggest a piecewise linear relationship (P = 0.008) between patching dose-rate (hours/day) and TED with a single breakpoint estimated at 2.16 (standard error 0.51) hours/day, suggesting doses below 2.16 hours/day are less effective.

CONCLUSION

We introduce the concept of TED of occlusion. Predictors for TED are visual acuity deficit, amblyopia type, and age at start of occlusion therapy. Dose-rates prescribed within the model range from 2.5 to 12 hours/day and can be revised dynamically throughout treatment in response to recorded patient compliance: a personalized dosing strategy.

Paediatric Eye Services: How Much of the Workload Is Amblyopia-Related?

AIMS

The proportion of patients seen by the paediatric eye service that attend for reasons related to amblyopia has not been quantified. The purpose of this study was to quantify the proportion of patients seen in the paediatric eye service attending for reasons related to amblyopia.

METHODS

Records of all eye appointments of children attending the Hillingdon Hospitals NHS Foundation Trust and St Mary's Hospital Imperial College Healthcare NHS Trust over one month in 2009 were examined to determine the diagnosis and reason for attendance.

RESULTS

Seven hundred and four patients had appointments booked at St Mary's and Hillingdon in March 2009. The fail-to-attend rates were not significantly different at the 2 sites (19% at St Mary's and 9% at Hillingdon; P=0.75). Of the 704 patients, 533 (St Mary's, 252 [75%]; Hillingdon, 281 [76%]) were attending for amblyopia-related reasons. Of the overall 982 booked appointments, 770 (79%) were amblyopia-related.

CONCLUSIONS

Amblyopia diagnosis and management is clearly the most common cause of attendance to the paediatric eye service, accounting for over three-quarters of outpatient visits.

Dynamics of Interocular Suppression in Amblyopic Children during Electronically Monitored Occlusion Therapy: First Insight

PURPOSE

Interocular suppression is assumed to be the mechanism leading to impaired visual acuity, especially in strabismic amblyopia. Little is known about the dynamics of suppression during treatment. The aim of our study was to assess the development of the depth of suppression and its relation to changes in visual acuity during electronically monitored occlusion treatment.

METHODS

In a prospective pilot study, 15 amblyopes (8 with and 7 without strabismus) aged 5 to 16 years (mean 10.24 years) were examined before initiation of patching and then every 3 to 6 weeks for 4 months. To quantify suppression, a red filter ladder (Sbisa bar) was used, attenuating the image of the dominant eye until the patients reported a binocular perception (diplopia, rivalry, color mixture) or a change in eye dominance. Acuity was assessed with crowded Landolt rings. Daily occlusion was recorded using occlusion dose monitors.

RESULTS

The depth of interocular suppression showed a biphasic change: it increased significantly during the first month (P=0.02), while visual acuity improved (mean 0.14 log units ±0.13; P<0.01). During the following 3 months, median suppression decreased back to the initial values. This reduction in suppression was more pronounced in anisometropic patients without strabismus than in amblyopes with strabismus. The average visual acuity steadily improved (P<0.01) during the 4 months of treatment. Mean recorded patching dose rate was 3.91 h/d. The correlation between mean daily occlusion and suppression changes was not statistically significant.

CONCLUSIONS

This first insight into the functional changes during electronically monitored patching suggests a complex relationship between visual acuity and interocular suppression that seems to be influenced by the presence of strabismus. Knowledge of the dynamics of interocular suppression is crucial for enhancing the outcome of occlusion treatment and also for the evaluation of its future role compared to emerging dichoptic treatments.

Binocular versus standard occlusion or blurring treatment for unilateral amblyopia in children aged three to eight years

BACKGROUND

Current treatments for amblyopia in children, occlusion and pharmacological blurring, have had limited success, with less than two-thirds of children achieving good visual acuity of at least 0.20 logMAR in the amblyopic eye, limited improvement of stereopsis, and poor compliance. A new treatment approach, based on the dichoptic presentation of movies or computer games (images presented separately to each eye), may yield better results, as it aims to balance the input of visual information from each eye to the brain. Compliance may also improve with these more child-friendly treatment procedures.

OBJECTIVES

To determine whether binocular treatments in children aged three to eight years with unilateral amblyopia result in better visual outcomes than conventional occlusion or pharmacological blurring treatment.

SEARCH METHODS

We searched the Cochrane Eyes and Vision Group Trials Register (last date of searches: 14 April 2015), the Cochrane Central Register of Controlled Trials (CENTRAL; 2015, Issue 3), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE (January 1946 to April 2015), EMBASE (January 1980 to April 2015), the ISRCTN registry (www.isrctn.com/editAdvancedSearch), ClinicalTrials.gov (www.clinicaltrials.gov), and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic searches for trials.

SELECTION CRITERIA

Two review authors independently screened the results of the search in order to identify studies that met the inclusion criteria of the review: randomised controlled trials (RCTs) that enrolled participants between the ages of three and eight years old with unilateral amblyopia, defined as best-corrected visual acuity (BCVA) worse than 0.200 logMAR in the amblyopic eye, and BCVA 0.200 logMAR or better in the fellow eye, in the presence of an amblyogenic risk factor such as anisometropia, strabismus, or both. Prior to enrolment, participants were to have undergone a cycloplegic refraction and comprehensive ophthalmic examination including fundal examination. In addition, participants had to have completed a period of optical treatment, if indicated, and BCVA in the amblyopic eye had to remain unchanged on two consecutive assessments despite reportedly good compliance with glasses wearing. Participants were not to have received any treatment other than optical treatment prior to enrolment. We planned to include any type of binocular viewing intervention; these could be delivered on different devices including computer monitors viewed with LCD shutter glasses or hand-held screens including mobile phone screens with lenticular prism overlay. Control groups were to have received standard amblyopia treatment; this could include occlusion or pharmacological blurring of the better-seeing eye. We planned to include full-time (all waking hours) and part-time (between 1 and 12 hours a day) occlusion regimens.

DATA COLLECTION AND ANALYSIS

We planned to use standard methodological procedures expected by The Cochrane Collaboration. We had planned to meta-analyse the primary outcome, that is mean distance BCVA in the amblyopic eye at 12 months after the cessation of treatment.

MAIN RESULTS

We could identify no RCTs in this subject area.

AUTHORS' CONCLUSIONS

Further research is required to allow decisions about implementation of binocular treatments for amblyopia in clinical practice. Currently there are no clinical trials offering standardised evidence of the safety and effectiveness of binocular treatments, but results from non-controlled cohort studies are encouraging. Future research should be conducted in the form of RCTs, using acknowledged methods of visual acuity and stereoacuity assessment with known reproducibility. Other important outcome measures include outcomes reported by users, compliance with treatment, and recurrence of amblyopia after cessation of treatment.

Prescribed computer games in addition to occlusion versus standard occlusion treatment for childhood amblyopia: a pilot randomised controlled trial

BACKGROUND

Amblyopia ("lazy eye") is the commonest vision deficit in children. If not fully corrected by glasses, amblyopia is treated by patching or blurring the better-seeing eye. Compliance with patching is often poor. Computer-based activities are increasingly topical, both as an adjunct to standard treatment and as a platform for novel treatments. Acceptability by families has not been explored, and feasibility of a randomised controlled trial (RCT) using computer games in terms of recruitment and treatment acceptability is uncertain.

METHODS

We carried out a pilot RCT to test whether computer-based activities are acceptable and accessible to families and to test trial methods such as recruitment and retention rates, randomisation, trial-specific data collection tools and analysis. The trial had three arms: standard near activity advice, Eye Five, a package developed for children with amblyopia, and an off-the-shelf handheld games console with pre-installed games. We enrolled 60 children age 3-8 years with moderate or severe amblyopia after completion of optical treatment.

RESULTS

This trial was registered as UKCRN-ID 11074. Pre-screening of 3600 medical notes identified 189 potentially eligible children, of whom 60 remained eligible after optical treatment, and were enrolled between April 2012 and March 2013. One participant was randomised twice and withdrawn from the study. Of the 58 remaining, 37 were boys. The mean (SD) age was 4.6 (1.7) years. Thirty-seven had moderate and 21 severe amblyopia. Three participants were withdrawn at week 6, and in total, four were lost to follow-up at week 12. Most children and parents/carers found the study procedures, i.e. occlusion treatment, usage of the allocated near activity and completion of a study diary, easy. The prescribed cumulative dose of near activity was 84 h at 12 weeks. Reported near activity usage numbers were close to prescribed numbers in moderate amblyopes (94 % of prescribed) but markedly less in severe amblyopes (64 %). Reported occlusion usage at 12 weeks was 90 % of prescribed dose for moderate and 33 % for severe amblyopes.

CONCLUSIONS

Computer-based games and activities appear acceptable to families as part of their child's amblyopia treatment. Trial methods were appropriate and accepted by families.

The effect of amblyopia treatment on stereoacuity

PURPOSE

To explore how stereoacuity changes in patients while they are being treated for amblyopia.

METHODS

The Monitored Occlusion Treatment for Amblyopia Study (MOTAS) comprised 3 distinct phases. In the first phase, baseline, assessments of visual function were made to confirm the initial visual and binocular visual deficit. The second phase, refractive adaptation, now commonly termed "optical treatment," was an 18-week period of spectacle wear with measurements of logMAR visual acuity and stereoacuity with the Frisby test at weeks 0, 6, 12, and 18. In the third phase, occlusion, participants were prescribed 6 hours of patching per day.

RESULTS

A total of 85 children were enrolled (mean age, 5.1 ± 1.5 years). In 21 children amblyopia was associated with anisometropia; in 29, with strabismus; and in 35, with both. At study entry, poor stereoacuity was associated with poor visual acuity (P < 0.001) in the amblyopic eye and greater angle of strabismus (P < 0.001). Of 66 participants, 25 (38%) who received refractive adaptation and 19 (29%) who received occlusion improved by at least one octave in stereoacuity, exceeding test-retest variability. Overall, 38 (45%) improved one or more octaves across both treatment phases. Unmeasureable stereoacuity was observed in 56 participants (66%) at study entry and in 37 (43%) at study exit.

CONCLUSIONS

Stereoacuity improved for almost one half of the study participants. Improvement was observed in both treatment phases. Factors associated with poor or nil stereoacuity at study entry and exit were poor visual acuity of the amblyopic eye and large-angle strabismus.

Amblyopia and binocular vision

Amblyopia is the most common cause of monocular visual loss in children, affecting 1.3%-3.6% of children. Current treatments are effective in reducing the visual acuity deficit but many amblyopic individuals are left with residual visual acuity deficits, ocular motor abnormalities, deficient fine motor skills, and risk for recurrent amblyopia. Using a combination of psychophysical, electrophysiological, imaging, risk factor analysis, and fine motor skill assessment, the primary role of binocular dysfunction in the genesis of amblyopia and the constellation of visual and motor deficits that accompany the visual acuity deficit has been identified. These findings motivated us to evaluate a new, binocular approach to amblyopia treatment with the goals of reducing or eliminating residual and recurrent amblyopia and of improving the deficient ocular motor function and fine motor skills that accompany amblyopia.

Compliance to patching in the treatment of amblyopia

PURPOSE

To evaluate compliance of amblyopic patients to patching, and to identify reasons of poor compliance and suggest methods to overcome the problem.

METHODS

We conducted a cross-sectional, retrospective study that included 37 families with a child diagnosed with unilateral amblyopia (age range 3-16 years) and attending the Pediatrics Ophthalmology clinic at the King Abdulaziz University Hospital (a tertiary eye hospital). Data were collected through interviews and from hospital charts. In the interviews we asked questions that sought information with regard to four aspects (domains); knowledge, attitude, insight and community's effect. A score representing each domain was given to every family then we correlated these scores with family's compliance percentage.

RESULTS

When correlated with compliance, the insight and attitude domains showed a statistically significant correlation; p-value 0.002 and 0.004, respectively. However, the knowledge and community's effect domains were not; p-value 0.084 and 0.114, respectively. Other qualitative factors affecting compliance were identified with open questions. Quotes from families of what they think can improve compliance are shown.

CONCLUSION

To improve compliance, merely educating patients is not sufficient and more efforts should be undertaken toward ensuring true sense of the problem and its impact. Factors affecting compliance due to the physical properties in the patch itself should be addressed too (heat, irritation, poor adhesive material and design).

Amblyopia therapy: an update

We review the findings of trials of mainstay amblyopia treatment conducted within the last 5 years. These have confirmed that an initial period of full-time refractive correction is beneficial in all types of amblyopia. Adopting this practice may allow up to 30% of children to avoid any further treatment. Studies that have investigated the role of atropine occlusion as a first-line treatment for amblyopia have shown "weekend atropine" to be as effective as patching for children with both moderate and severe amblyopia. Where patching is prescribed, 2-4 hours/day of occlusion appears sufficient to provide an optimum outcome for the majority of children, although those over 6 years tend to require a larger dose to achieve best outcome, their amblyopia being more resistant to treatment. Educational interventions such as cartoons and written and video explanations of treatment aimed at improving compliance appear to raise it to a therapeutic level in those who may otherwise have poor compliance or drop out from treatment. Formal, evidence-based practice guidelines for the management of amblyopia have emerged although their adoption by practitioners, at least in the United Kingdom, has been questioned.

Can perceptual learning be used to treat amblyopia beyond the critical period of visual development?

BACKGROUND

Amblyopia presents early in childhood and affects approximately 3% of western populations. The monocular visual acuity loss is conventionally treated during the 'critical periods' of visual development by occluding or penalising the fellow eye to encourage use of the amblyopic eye. Despite the measurable success of this approach in many children, substantial numbers of people still suffer with amblyopia later in life because either they were never diagnosed in childhood, did not respond to the original treatment, the amblyopia was only partially remediated, or their acuity loss returned after cessation of treatment.

PURPOSE

In this review, we consider whether the visual deficits of this largely overlooked amblyopic group are amenable to conventional and innovative therapeutic interventions later in life, well beyond the age at which treatment is thought to be effective.

RECENT FINDINGS

There is a considerable body of evidence that residual plasticity is present in the adult visual brain and this can be harnessed to improve function in adults with amblyopia. Perceptual training protocols have been developed to optimise visual gains in this clinical population. Results thus far are extremely encouraging; marked visual improvements have been demonstrated, the perceptual benefits transfer to new visual tasks and appear to be relatively enduring. The essential ingredients of perceptual training protocols are being incorporated into video game formats, facilitating home-based interventions.

SUMMARY

Many studies support perceptual training as a tool for improving vision in amblyopes beyond the critical period. Should this novel form of treatment stand up to the scrutiny of a randomised controlled trial, clinicians may need to re-evaluate their therapeutic approach to adults with amblyopia.

The pattern of learned visual improvements in adult amblyopia

PURPOSE

Although amblyopia is diagnosed in terms of a monocular letter acuity loss, individuals typically present with deficits on a wide range of spatial tasks. Many of these deficits can be collapsed along two basic visual dimensions (visual acuity and contrast sensitivity) that together account for most of the variability in performance of the amblyopic visual system. In this study, this space was exploited, to target the main deficits and fully characterize the pattern of learned visual improvements in adult amblyopic subjects.

METHODS

Twenty-six amblyopic subjects (mean age, 39 ±12 years) were trained on one of four tasks, categorized as either visual acuity (letter or grating acuity) or contrast sensitivity (letter or grating contrast) tasks. Performance was measured on all tasks before and after training, to quantify learning along each dimension and generalization to the other dimension. Performance in 35 visually normal subjects (mean, age 24 ± 5 years) was used to establish normal variation in visual performance along each dimension, against which the learned improvements in amblyopic subjects was compared.

RESULTS

Training on the contrast sensitivity tasks produced substantial within-task learning and generalization to measures of visual acuity. The learned improvements in performance after training on the letter acuity task were also substantial, but did not generalize to contrast sensitivity.

CONCLUSIONS

Mapping the pattern of learning onto the known deficit space for amblyopia enabled the identification of tasks and stimulus configurations that optimized learning, guiding further development of learning-based interventions in this clinical group.

Recovery of stereo acuity in adults with amblyopia

Disruption of visual input to one eye during early development leads to marked functional impairments of vision, commonly referred to as amblyopia. A major consequence of amblyopia is the inability to encode binocular disparity information leading to impaired depth perception or stereo acuity. If amblyopia is treated early in life (before 4 years of age), then recovery of normal stereoscopic function is possible. Treatment is rarely undertaken later in life (adulthood) because declining levels of neural plasticity are thought to limit the effectiveness of standard treatments. Here, the authors show that a learning-based therapy, designed to exploit experience-dependent plastic mechanisms, can be used to recover stereoscopic visual function in adults with amblyopia. These cases challenge the long-held dogma that the critical period for visual development and the window for treating amblyopia are one and the same.

Using Directed Acyclic Graphs to detect limitations of traditional regression in longitudinal studies

INTRODUCTION

Longitudinal data are increasingly available to health researchers; these present challenges not encountered in cross-sectional data, not the least of which is the presence of time-varying confounding variables and intermediate effects.

OBJECTIVES

We review confounding and mediation in a longitudinal setting and introduce causal graphs to explain the bias that arises from conventional analyses.

CONCLUSIONS

When both time-varying confounding and mediation are present in the data, traditional regression models result in estimates of effect coefficients that are systematically incorrect, or biased. In a companion paper (Moodie and Stephens in Int J Publ Health, 2010b, this issue), we describe a class of models that yield unbiased estimates in a longitudinal setting.

Spatial frequency discrimination learning in normal and developmentally impaired human vision

Perceptual learning effects demonstrate that the adult visual system retains neural plasticity. If perceptual learning holds any value as a treatment tool for amblyopia, trained improvements in performance must generalise. Here we investigate whether spatial frequency discrimination learning generalises within task to other spatial frequencies, and across task to contrast sensitivity. Before and after training, we measured contrast sensitivity and spatial frequency discrimination (at a range of reference frequencies 1, 2, 4, 8, 16 c/deg). During training, normal and amblyopic observers were divided into three groups. Each group trained on a spatial frequency discrimination task at one reference frequency (2, 4, or 8 c/deg). Normal and amblyopic observers who trained at lower frequencies showed a greater rate of within task learning (at their reference frequency) compared to those trained at higher frequencies. Compared to normals, amblyopic observers showed greater within task learning, at the trained reference frequency. Normal and amblyopic observers showed asymmetrical transfer of learning from high to low spatial frequencies. Both normal and amblyopic subjects showed transfer to contrast sensitivity. The direction of transfer for contrast sensitivity measurements was from the trained spatial frequency to higher frequencies, with the bandwidth and magnitude of transfer greater in the amblyopic observers compared to normals. The findings provide further support for the therapeutic efficacy of this approach and establish general principles that may help develop more effective protocols for the treatment of developmental visual deficits.

Estimation of dose-response functions for longitudinal data using the generalised propensity score

In a longitudinal study of dose-response, it is often necessary to adjust for confounding or non-compliance, which may otherwise compromise the estimation of the true effect of a treatment. Using an approach based on the generalised propensity score (GPS)--a generalisation of the classical, binary treatment propensity score--it is possible to construct a balancing score that provides an estimation procedure for the true (unconfounded) direct effect of dose on response. Previously, the GPS has been applied only in a single interval setting; in this article, we extend the GPS methodology to the longitudinal setting to estimate the direct effect of a continuous dose on a longitudinal response. The methodology is applied to two simulated examples, and a real longitudinal dose-response investigation, the Monitored Occlusion Treatment of Amblyopia Study (MOTAS). In the treatment of childhood amblyopia, a common ophthalmological condition, occlusion therapy (patching) was for many decades the standard medical treatment, despite the fact that its efficacy was not quantified. MOTAS was revolutionary, as it was the first study to obtain precise measurements of the amount of occlusion each study participant received over the course of the study.

The optical treatment of amblyopia

The role of refractive correction has been underestimated as a distinct component of amblyopia therapy. Until relatively recently, the extent to which it could ameliorate the amblyopic acuity deficit remained unquantified and the time course of its effect unknown. Improvement of vision after refractive correction appears to occur in all the major types of amblyopia, including, somewhat surprisingly, in the presence of strabismus. Although the neurophysiological basis of the remediative effect of such "optical treatment" is unknown, some insight is now available from animal models and psychophysical investigations in humans. An appreciation of the role that refractive correction can play in the overall management of amblyopia has led to the formulation of new treatment guidelines, whereby a defined period of spectacle or contact lens wear always precedes traditional therapies, such as occlusion or penalization.

Neural mechanisms of recovery following early visual deprivation

Natural patterned early visual input is essential for the normal development of the central visual pathways and the visual capacities they sustain. Without visual input, the functional development of the visual system stalls not far from the state at birth, and if input is distorted or biased the visual system develops in an abnormal fashion resulting in specific visual deficits. Monocular deprivation, an extreme form of biased exposure, results in large anatomical and physiological changes in terms of territory innervated by the two eyes in primary visual cortex (V1) and to a loss of vision in the deprived eye reminiscent of that in human deprivation amblyopia. We review work that points to a special role for binocular visual input in the development of V1 and vision. Our unique approach has been to provide animals with mixed visual input each day, which consists of episodes of normal and biased (monocular) exposures. Short periods of concordant binocular input, if continuous, can offset much longer episodes of monocular deprivation to allow normal development of V1 and prevent amblyopia. Studies of animal models of patching therapy for amblyopia reveal that the benefits are both heightened and prolonged by daily episodes of binocular exposure.

Different corrections of hypermetropic errors in the successful treatment of hypermetropic amblyopia in children 3 to 7 years of age

PURPOSE

To evaluate the improvement in visual acuity (VA) in children 3 to 7 years old with hypermetropic amblyopia after full or partial hypermetropic correction.

DESIGN

Retrospective interventional case series.

METHODS

Medical records of 182 children with hypermetropic amblyopia treated with partial or full hypermetropic correction from January 1, 2001 to July 31, 2007 were evaluated. Improvement in the VA of the amblyopic eye, changes in the power of glasses, and the reduction in hypermetropia were assessed.

RESULTS

Ninety-three children underwent full hypermetropic correction and the mean VA of their amblyopic eyes improved by 0.46 logarithm of minimal angle of resolution (logMAR). Eighty-one children underwent partial hypermetropic correction and the mean VA of their amblyopic eyes improved by 0.48 logMAR. The reduction in hypermetropia was 0.44 diopters (D)/year and 0.43 D/year, respectively. Changes in glasses at four to eight weeks of follow-up were noted in 11 children receiving full correction, all of whom were older than 5 years. Ten children, aged 3 to 5 years, with hypermetropia of more than 3 D and receiving partial correction, required a change of glasses and most (seven children) had underdiagnosed accommodative esotropia.

CONCLUSIONS

Both full correction and partial correction of hypermetropic errors improved the VA of 3 to 7-year-old children with hypermetropic amblyopia. The reduction in hypermetropia was similar after full and partial hypermetropic correction. However, for children older than 5 years, full correction should be undertaken with care because the accompanying blur at distance can hinder compliance. For younger children, especially with a high degree of hypermetropia, full correction might be required to avoid strabismus, which would cancel the effects of spectacle correction.

Objectively monitored patching regimens for treatment of amblyopia: randomised trial

OBJECTIVES

To compare visual outcome in response to two prescribed rates of occlusion (six hours a day and 12 hours a day).

DESIGN

Unmasked randomised trial.

SETTING

Research clinics in two London hospitals.

PARTICIPANTS

97 children with a confirmed diagnosis of amblyopia associated with strabismus, anisometropia, or both.

INTERVENTIONS

18 week period of wearing glasses (refractive adaptation) followed by occlusion prescribed ("patching") for six or 12 hours a day.

MAIN OUTCOME MEASURES

Visual acuity measured by logMAR letter recognition; objectively monitored rate of occlusion (hours a day).

RESULTS

The mean age of children at study entry was 5.6 (SD 1.5) years. Ninety were eligible for occlusion but 10 dropped out in this phase, leaving 80 children who were randomised to a prescribed dose rate of six (n=40) or 12 (n=40) hours a day. The mean change in visual acuity of the amblyopic eye was not significantly different (P=0.64) between the two groups (0.26 (95% confidence interval 0.21 to 0.31) log units in six hour group; 0.24 (0.19 to 0.29) log units in 12 hour group). The mean dose rates (hours a day) actually received, however, were also not significantly different (4.2 (3.7 to 4.7) in six hour group v 6.2 (5.1 to 7.3) in 12 hour group; P=0.06). The visual outcome was similar for those children who received three to six hours a day or more than six to 12 hours a day, but significantly better than that in children who received less than three hours a day. Children aged under 4 required significantly less occlusion than older children. Visual outcome was not influenced by type of amblyopia.

CONCLUSIONS

Substantial (six hours a day) and maximal (12 hours a day) prescribed occlusion results in similar visual outcome. On average, the occlusion dose received in the maximal group was only 50% more than in the substantial group and in both groups was much less than that prescribed. Younger children required the least occlusion.

TRIALS REGISTRATION

Clinical Trials NCT00274664.

Anisometropic amblyopia treated with spectacle correction alone: possible factors predicting success and time to start patching

PURPOSE

To evaluate factors predicting resolution of amblyopia and the time course of improvement in VA in children 3 to 7 years old with anisometropic amblyopia treated with spectacles alone.

DESIGN

Prospective, noncomparative intervention.

METHODS

Measurement of corrected amblyopic logMAR visual acuity (VA) in newly diagnosed children at four-weekly intervals until VA stabilized or amblyopia resolved. The time course of improvement in VA and the factors related to amblyopia resolution were assessed.

RESULTS

Sixty children with a mean age of 5.3 years and mean anisometropia of 2.95 diopters (D) were included. Amblyopia improved by 2 or more logMAR lines in 56 patients (93%) and resolved in 27 patients (45%), with a mean improvement in VA of 0.38 logMAR. The improvement in VA in the amblyopic eye was considerable at four to 12 weeks then reached a plateau, after which it improved only slowly. Resolution of amblyopia was related to better initial VA (0.2 to 0.6 logMAR) and lesser amounts of anisometropia (<4 D). The time to resolution ranged from four to 40 weeks, but no patient with residual amblyopia showed an improvement in VA of more than 0.1 logMAR over four consecutive visits.

CONCLUSIONS

With spectacle correction alone, 3- to 7-year-old children with previously untreated anisometropic amblyopia achieved approximately four-line improvement and resolved nearly in half. The nearly two-month plateau periods during improvement of VA should be noticed. After four months with no improvement in VA, occlusion therapy or atropine penalization may be considered.

Preliminary results from the use of the novel Interactive binocular treatment (I-BiT) system, in the treatment of strabismic and anisometropic amblyopia

BACKGROUND

We have developed a novel application of adapted virtual reality (VR) technology, for the binocular treatment of amblyopia. We describe the use of the system in six children.

METHODS

Subjects consisted of three conventional treatment 'failures' and three conventional treatment 'refusers', with a mean age of 6.25 years (5.42-7.75 years). Treatment consisted of watching video clips and playing interactive games with specifically designed software to allow streamed binocular image presentation.

RESULTS

Initial vision in the amblyopic eye ranged from 6/12 to 6/120 and post-treatment 6/7.5 to 6/24-1. Total treatment time was a mean of 4.4 h. Five out of six children have shown an improvement in their vision (average increase of 10 letters), including those who had previously failed to comply with conventional occlusion.

CONCLUSIONS

Improvements in vision were demonstrable within a short period of time, in some children after 1 h of treatment. This system is an exciting and promising application of VR technology as a new treatment for amblyopia.

Intermediate spatial frequency letter contrast sensitivity: its relation to visual resolution before and during amblyopia treatment

We examined the loss of letter contrast sensitivity (LCS) measured using the Pelli-Robson chart, and the extent to which any such loss was modulated by spectacle wear and occlusion therapy in children participating in an amblyopia treatment trial. Their initial mean interocular difference in logMAR acuity was approximately three times that of their LCS (0.45 vs 0.14 log units). Log LCS was weakly though significantly correlated with logMAR visual acuity (VA) for all VAs better than 0.90 (r = -0.19, 95% CI: -0.28 to -0.10) whereas for all VAs of 0.90 or poorer, log LCS was markedly and significantly correlated with VA (r = -0.72, 95% CI: -0.83 to -0.53). LCS in those children with a > or =0.1 log unit interocular difference on this test improved commensurately with VA during treatment. We conjecture that the spatial visual loss in all but the most severe amblyopes occurs in an area of resolution and contrast space that lies beyond that sampled by the Pelli-Robson chart.

Amblyopia: diagnostic and therapeutic options

PURPOSE

To provide an overview of the current state of knowledge of amblyopia and highlight recent advances in diagnosis and treatment.

DESIGN

Review of literature and perspective.

METHODS

MEDLINE search for amblyopia, with a review of all recent literature adding authors' personal perspectives on the findings.

RESULTS

Increased awareness of amblyopia and better screening techniques are required to identify children who are at risk for amblyopia at a younger age. Randomized, controlled trials have established atropine penalization as a viable alternative to occlusion therapy, have suggested that less treatment may be better tolerated and as effective as more traditionally used dosages, and have found no compelling evidence that treatment is beneficial clinically for older (over age 10) children with amblyopia.

CONCLUSION

Early detection and treatment of amblyopia can improve the chances for a successful visual outcome. Considering that the conditions that place a patient at risk for amblyopia can be identified, that amblyopia responds to treatment, and that well-tolerated treatments for the condition are now recognized, it is not unreasonable to imagine that, in the near future, severe amblyopia could be eliminated as a public health problem.

Prevalence and outcomes of childhood visual disorders

PURPOSE

This population-based study examines the prevalence of childhood visual disorders: amblyopia (strabismus, refractive errors) and organic disease. It also assesses treatment outcomes, visual impairment and residual amblyopia.

METHODS

1582 children were retrospectively analysed on treatment completion (age 8-9 years). Significant visual disorders included: esotropia, exotropia, anisometropia (hyperopia > or = 1.50DS, astigmatism > or = 1.00DC, myopia > or = 1.50DS), ametropia (hyperopia > or = 1.50DS, astigmatism > or = 1.0DC, myopia > or = 0.75DS) and organic defects.

RESULTS

198 children (12.5%) had a significant visual disorder: strabismus (3.98%), eso:exo rate 5:1, anisometropia (2.34%), ametropia (5.82%), organic defects (0.38%). Organic disease caused visual handicap (< 6/18 in better eye) in 0.13%. Amblyopic visual impairment (6/18; 6/24-6/60) occurred in 1.13%; 2.02% had residual amblyopia (6/12 or worse).

CONCLUSIONS

Childhood visual disorders are a common problem. Unfavourable visual outcomes in esotropia are related to two sub-groups and particularly with poor concordance to treatment. Suggested strategies to improve outcomes include health promotion, an "Amblyopia Nurse" and a "Patch Club".

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.

Refractive adaptation in amblyopia: quantification of effect and implications for practice

AIM

To describe the visual response to spectacle correction ("refractive adaptation") for children with unilateral amblyopia as a function of age, type of amblyopia, and category of refractive error.

METHOD

Measurement of corrected amblyopic and fellow eye logMAR visual acuity in newly diagnosed children. Measurements repeated at 6 weekly intervals for a total 18 weeks.

RESULTS

Data were collected from 65 children of mean (SD) age 5.1 (1.4) years with previously untreated amblyopia and significant refractive error. Amblyopia was associated with anisometropia in 18 (5.5 (1.4) years), strabismus in 16 (4.2 (0.98) years), and mixed in 31 (5.2 (1.5) years) of the study participants. Mean (SD) corrected visual acuity of amblyopic eyes improved significantly (p<0.001) from 0.67 (0.38) to 0.43 (0.37) logMAR: a mean improvement of 0.24 (0.18), range 0.0-0.6 log units. Change in logMAR visual acuity did not significantly differ as a function of amblyopia type (p = 0.29) (anisometropia 0.22 (0.13); mixed 0.18 (0.14); strabismic 0.30 (0.24)) or for age (p = 0.38) ("under 4 years" 0.23 (0.18); "4-6 years" 0.24 (0.20); "over 6 years" 0.16 (0.23)).

CONCLUSION

Refractive adaptation is a distinct component of amblyopia treatment. To appropriately evaluate mainstream therapies such as occlusion and penalisation, the beneficial effects of refractive adaptation need to be fully differentiated. A consequence for clinical practice is that children may start occlusion with improved visual acuity, possibly enhancing compliance, and in some cases unnecessary patching will be avoided.

Reliability and Validity of the Melbourne Edge Test and High/Low Contrast Visual Acuity Chart

PURPOSE

The purposes of the study were to investigate the test-retest reliability and the validity of new versions of the Melbourne Edge Test (MET) and the High/Low Contrast Visual Acuity (H/LCVA) chart and to investigate the agreement between the original and new versions.

METHODS

The MET original photographic version, MET new light box version, H/LCVA Chart original photographic version, H/LCVA Chart new printed version, and the Pelli-Robson chart were administered twice to one eye of 22 subjects with low vision and 20 soft contact lenses wearers.

RESULTS

For the low vision group, the test-retest 95% limits of agreement were +/- 5.2 dB for the MET new light box version and +/- 0.39 logarithm of the minimum angle of resolution (logMAR) for the LCVA component of the H/LCVA new printed version. For the soft contact lens group, the test-retest 95% limits of agreement were +/- 2.1 dB for the MET new light box version and +/- 0.26 logMAR for the LCVA component of the H/LCVA new printed version. Moderate to high correlations were obtained between contrast sensitivity tests, thus providing evidence of validity. Scores obtained for the new test versions were significantly higher than the original versions (p < 0.01).

CONCLUSIONS

Of all the tests administered, the MET original photographic version and the Pelli-Robson Chart had the highest test-retest reliability for the low vision group. For the soft contact lens group, the H/LCVA original version (low contrast letters, 18% Weber) and the Pelli-Robson Chart had the highest reliability.

Objective survey of the prescription of occlusion therapy for amblyopia

PURPOSE

To identify the variation within and consistency amongst orthoptists when prescribing occlusion therapy for amblyopia in an objective survey.

METHODS

A questionnaire was designed with five case examples of amblyopic children and distributed at annual meetings of orthoptists in The Netherlands and Germany. It was filled in simultaneously within 15 min in complete silence to avoid any exchange of opinions between orthoptists that would reduce variability. For each case the orthoptists were asked to give their prescription of hours or days of occlusion.

RESULTS

The questionnaire was filled in by 177 Dutch orthoptists and 227 German orthoptists. Their prescriptions of occlusion therapy were classified into five main regimens: part-time; part-time not every day; full-time; also occluding the amblyopic eye; alternating; and no occlusion therapy. The variation was large: the standard deviation was half the average prescribed hours of occlusion for each regimen in each of the five cases. All orthoptists were assigned a rank number for each of the five cases depending on whether their prescription was above or below average. These five rank numbers were not consistently above or consistently below average value per case.

CONCLUSIONS

The number of prescribed hours of occlusion varied widely per regimen per case. Orthoptists were not consistently strict or lenient in their prescription of occlusion therapy.

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.