Effectiveness of occlusion therapy in ametropic amblyopia: a pilot study

Amblyopia and Routine Eye Exam in Children: Parent's Perspective

Amblyopia is a reduced best-corrected visual acuity of one or both eyes that cannot be attributed to a structural abnormality; it is a functional reduction in the vision of an eye caused by disuse during a critical period of visual development. It is considered the leading cause of visual defects in children. With early diagnosis and treatment, children with amblyopia can significantly improve their vision. However, if it is neglected and not treated during childhood, unfortunately, it permanently decreases vision. Therefore, prevention, detection, and treatment largely depend on parents. This article explores parents' perspectives on amblyopia and routine examination of their children's eyes. A cross-sectional study used an electronic questionnaire consisting of five main sections to assess the level of awareness of amblyopia among parents. As a result, a total of 325 participants were included in our analysis. 209 (64.3%) were mothers, and 116 (35/7%) were fathers. The age groups were 35-50 years of age (61.5%), 20-34 years (23.4%), and older than 50 years (15%). Participants with a history of amblyopia numbered 23 (7.1%), and 39 had an amblyopic child (12%). A good awareness level of amblyopia among parents was found in only 10 (3%) participants, a fair awareness level in 202 (62%), and 113 (35%) participants were classified as having a poor awareness level of amblyopia. Only 13.8% of the parents took their children for yearly routine eye exams, while the majority (72%) took their children only if they had a complaint, and 14.2% took them for eye checkups only before school entry. In conclusion, parents' awareness of amblyopia in Tabuk City, KSA, was low. In addition, a limited proportion of parents reported consistently taking their children for routine eye exams. Therefore, raising awareness should be considered in public education regarding the disease.

Patching and Suppression in Amblyopia: One Mechanism or Two?

Purpose

To determine if benefits from occlusion therapy are due to decreased suppression from the fellow eye in children with amblyopia.

Methods

Ten newly diagnosed amblyopes (7.2 ± 1.4 years old), two with strabismus and eight with anisometropia, participated. Patients were first given a 2-month period of refractive adaptation, followed by occlusion therapy (i.e., patching their fellow eye with an opaque patch for 4 h/day). Visual acuity of the amblyopic eye and interocular suppression were measured before and after 0.5, 1, 2, 4, and 6 months of occlusion therapy. We quantified interocular suppression with a binocular phase combination task.

Results

Visual acuity (in logMAR) improved from 0.50 ± 0.22 (mean ± SD) to 0.33 ± 0.20 for patients who finished a short-term (2 months) occlusion (A1–A10), from 0.53 ± 0.20 to 0.32 ± 0.22 for patients who finished a medium-term (4 months) occlusion (A1–A9), and from 0.48 ± 0.19 to 0.22 ± 0.10 for patients who finished a long-term (6 months) occlusion (A1–A8). Although their visual acuity significantly improved, their degree of suppression, which was abnormal in all cases, did not change consistently. This was true in all durations of occlusion therapy.

Conclusion

Reduced suppression from the fixing eye might not be result from occlusion therapy.

The awareness of amblyopia among parents in Saudi Arabia

Purpose

Amblyopia is the most common cause of unilateral visual impairment. This study investigated parents' awareness of amblyopia in different regions of Saudi Arabia.

Methods

This was a cross-sectional population study. The survey consisted of two main sections; the first section contained 13 general background questions, and the second section (10 questions) focused on awareness of amblyopia, routine vision checks and how to raise awareness of amblyopia in the community. The survey was distributed to respondents using email and social media.

Results

The responses of 1649 families were received. Respondents' age range was from 22-62 years (mean ± standard deviation = 33.6 ± 8.7 years). Most respondents had no previous knowledge of amblyopia (1155 participants, 70%), and 313 participants (19%) had no idea if their children had amblyopia. In total, 990 participants (60%) did not visit the eye clinic with their children for a routine eye exam. A total of 495 parents (30%), who were aware of amblyopia, knew of it mainly from eye clinic visits and from Internet websites. A total of 140 respondents reported that their children had amblyopia; 58.3% of those children underwent routine eye examinations once a year, and the rest underwent routine eye examinations twice a year.

Conclusion

The results clearly showed a lack of amblyopia awareness among the Saudi community. This lack of awareness can lead to visual impairment among children. More efficient efforts are urgently needed from health professionals, education centres, the media and social organizations to promote awareness of amblyopia.

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.

Compliance and patching and atropine amblyopia treatments

In the past 20 years, there has been a great advancement in knowledge pertaining to compliance with amblyopia treatments. The occlusion dose monitor introduced quantitative monitoring methods in patching, which sparked our initial understanding of the dose-response relationship for patching amblyopia treatment. This review focuses on current compliance knowledge and the impact it has on patching and atropine amblyopia treatment.

Clinical aspects of different types of amblyopia

nema

Laser refractive correction of myopia in visually impaired patients improves visual acuity

PURPOSE

To retrospectively evaluate the visual and refractive outcome of visually impaired adults treated with refractive surgery (photorefractive keratectomy or laser-assisted in situ keratomileusis).

METHODS

We searched a refractive surgery database comprising 1716 mildly visually impaired patients [best spectacle-corrected visual acuity (BSCVA) on a logMAR scale ≤ -0.1 (Snellen ≤ 0.8)] who had undergone either PRK or LASIK (n = 96). PRK patients who had visits at 5-7, 8-13 and 14-24 months postoperatively were selected. Eleven patients and nine PRK control myopic patients were found (cohort 1). From the same database, 41 visually impaired patients and 54 controls who had a postoperative control at 14-24 months postoperatively were chosen. These patients formed cohort 2.

RESULTS

Preoperatively, in cohort 1, the mean BSCVA on a logMAR scale was -0.15 ± 0.13 (Snellen 0.73 ± 0.16) in visually impaired patients and 0.04 ± 0.02 (Snellen 1.11 ± 0.17) in myopic controls. At 14-24 months postoperatively, the mean BSCVA improved to 0.05 ± 0.04 (Snellen 1.13 ± 0.10) in visually impaired patients and 0.05 ± 0.08 (Snellen 1.13 ± 0.21) in control patients. In cohort 2, preoperatively the mean BSCVA on a logMAR scale was -0.15 ± 0.12 (Snellen 0.74 ± 0.14) in visually impaired patients and 0.01 ± 0.03 (Snellen 1.04 ± 0.10) in myopic controls. At 14-24 months postoperatively, the mean BSCVA improved to 0.02 ± 0.07 (Snellen 1.06 ± 0.16) in visually impaired patients and 0.06 ± 0.06 (Snellen 1.15 ± 0.16) in control patients.

CONCLUSION

Refractive surgery improves BSCVA in visually impaired patients, possibly through plastic changes in the visual cortex. Consequently, refractive surgery may be used successfully for the treatment of visually impaired adults to enhance their visual acuity.

Visual outcome in 879 children treated for strabismus: insufficient accommodation and vision deprivation, deficient emmetropisation and anisometropia

PURPOSE

To identify the effect of infant hypermetropia on residual amblyopia in children remaining after treatment.

MATERIALS AND METHODS

879 strabismic children had cycloplegic retinoscopy at the age of 6 months and later when strabismus was diagnosed. A total of 26 hypermetropes consistently wore glasses from the age of 6 months, and 305 other hypermetropes had their accommodation periodically assessed by dynamic retinoscopy before strabismus was diagnosed. The relation between the last known visual acuity after treatment and all other clinical findings was analysed using t-tests and regression analysis.

RESULTS

Vision less than 6/12 in nonfixing eyes was associated with infantile hypermetropia > +5.0D, and in rare instances in excess of -3.0D of myopia. In hypermetropes only, anisometropia was associated with worse amblyopia. Astigmatism was associated with myopia and low levels of hypermetropia but not with worse vision. The vision of fixing eyes that were hypermetropic was significantly worse than that of emmetropic or myopic eyes. Wearing spectacles from the age of 6 months was associated with better vision in the nonfixing eye. Vision in the nonfixing eye of 19 hypermetropic heterotropes who started wearing glasses between 6 and 18 months of age also was better than that of those who started wearing glasses after 18 months of age. Insufficiency of accommodation was related to the degree of infantile hypermetropia, to worse vision and to failure to emmetropise. Difference in amplitude of accommodation between the eyes was largest in hypermetropes with anisometropia > +1.50 D and was marginally associated with worse vision in microtropes who became anisometropic after infancy. Hypermetropia decreased more in fixing eyes than in nonfixing eyes, thereby causing anisohypermetropia to increase after infancy. This change was most pronounced in hypermetropic microtropes. Conversely, failure of fixing eyes to emmetropise was associated with an increase in their inability to accommodate and heterotropia.

CONCLUSIONS

On the basis of these findings, severe residual amblyopia in children remaining after treatment could be explained by additional vision deprivation. It can be reduced by starting spectacle correction of hypermetropia before the age of 18 months. Anisometropia seemed the result of deficient emmetropisation.

Relationship between anisometropia, patient age, and the development of amblyopia

PURPOSE

Previous studies evaluating the effect of anisometropia on amblyopia development have been biased because subject selection occurred as a result of decreased acuity. Photoscreening identifies anisometropic children in a manner that is not biased by acuity, and allows an opportunity to evaluate how patient age influences the prevalence and depth of amblyopia.

DESIGN

Retrospective observational study of preschool children with anisometropia.

METHODS

A statewide preschool photoscreening program screened 119,311 children and identified 792 with anisometropia >1.0 diopters. We correlated age with visual acuity and amblyopia depth. Results were compared with 562 strabismic children similarly identified.

RESULTS

Only 14% (six of 44) of anisometropic children aged 1 year or younger had amblyopia. Amblyopia was detected in 40% (32 of 80) of 2-year-olds, 65% (119 of 182) of 3-year-olds, and 76% of 5-year-olds. Amblyopia depth also increased with age. Moderate amblyopia prevalence was 2% (ages 0 to 1), 17% (age 2), and rose steadily to 45% (ages 6 to 7). Severe amblyopia was rare for children aged 0 to 3, 9% at age 4, and 14% at age 5. Children with strabismus had a relatively stable prevalence (30% ages 0 to 2; 42% ages 3 to 4; and 44% ages 5 to 7) and depth of amblyopia.

CONCLUSIONS

Younger children with anisometropia have a lower prevalence and depth of amblyopia than older children. By age 3, when most children undergo traditional screening, amblyopia has usually already developed. New vision screening technologies that allow early detection of anisometropia provide ophthalmologists an opportunity to intervene early, perhaps retarding or even preventing the development of amblyopia.

Treatment of anisometropic amblyopia in children with refractive correction

OBJECTIVE

To evaluate the effectiveness of refractive correction alone for the treatment of untreated anisometropic amblyopia in children 3 to <7 years old.

DESIGN

Prospective, multicenter, noncomparative intervention.

PARTICIPANTS

Eighty-four children 3 to <7 years old with untreated anisometropic amblyopia ranging from 20/40 to 20/250.

METHODS

Optimal refractive correction was provided, and visual acuity (VA) was measured with the new spectacle correction at baseline and at 5-week intervals until VA stabilized or amblyopia resolved.

MAIN OUTCOME MEASURES

Maximum improvement in best-corrected VA in the amblyopic eye and proportion of children whose amblyopia resolved (interocular difference of < or =1 line) with refractive correction alone.

RESULTS

Amblyopia improved with optical correction by > or =2 lines in 77% of the patients and resolved in 27%. Improvement took up to 30 weeks for stabilization criteria to be met. After stabilization, additional improvement occurred with spectacles alone in 21 of 34 patients observed in a control group of a subsequent randomized trial, with amblyopia resolving in 6. Treatment outcome was not related to age, but was related to better baseline VA and lesser amounts of anisometropia.

CONCLUSION

Refractive correction alone improves VA in many cases and results in resolution of amblyopia in at least one third of 3- to <7-year-old children with untreated anisometropic amblyopia. Although most cases of resolution occur with moderate (20/40-20/100) amblyopia, the average 3-line improvement in VA resulting from treatment with spectacles may lessen the burden of subsequent amblyopia therapy for those with denser levels of amblyopia.

A randomized trial to evaluate 2 hours of daily patching for strabismic and anisometropic amblyopia in children

OBJECTIVE

To compare 2 hours of daily patching (combined with 1 hour of concurrent near visual activities) with a control group of spectacle wear alone (if needed) for treatment of moderate to severe amblyopia in children 3 to 7 years old.

DESIGN

Prospective randomized multicenter clinical trial (46 sites).

PARTICIPANTS

One hundred eighty children 3 to 7 years old with best-corrected amblyopic-eye visual acuity (VA) of 20/40 to 20/400 associated with strabismus, anisometropia, or both who had worn optimal refractive correction (if needed) for at least 16 weeks or for 2 consecutive visits without improvement.

INTERVENTION

Randomization either to 2 hours of daily patching with 1 hour of near visual activities or to spectacles alone (if needed). Patients were continued on the randomized treatment (or no treatment) until no further improvement was noted.

MAIN OUTCOME MEASURE

Best-corrected VA in the amblyopic eye after 5 weeks.

RESULTS

Improvement in VA of the amblyopic eye from baseline to 5 weeks averaged 1.1 lines in the patching group and 0.5 lines in the control group (P = 0.006), and improvement from baseline to best measured VA at any visit averaged 2.2 lines in the patching group and 1.3 lines in the control group (P<0.001).

CONCLUSION

After a period of treatment with spectacles, 2 hours of daily patching combined with 1 hour of near visual activities modestly improves moderate to severe amblyopia in children 3 to 7 years old.

Successful treatment of anisometropic amblyopia with spectacles alone

BACKGROUND

The efficacy of treating anisometropic amblyopia with occlusion therapy is well known. However, this form of treatment can be associated with risks. Spectacle correction alone may be a successful and underutilized form of treatment.

METHODS

The records of 28 patients treated successfully for anisometropic amblyopia with glasses alone were reviewed. Age, initial visual acuity and stereoacuity, and nature of anisometropia were analyzed to assess associations with time required for resolution, final visual acuity, and stereoacuity. Incidence of amblyopia recurrence and results of subsequent treatment, including patching, were also studied.

RESULTS

Mean time to amblyopia resolution (interocular acuity difference <or=1 line) was 5.8 months (range 2 to 15 months). Worse best corrected initial visual acuity was associated with longer time to resolution (Spearman's rho = 0.37, P = 0.05), while age, initial stereoacuity, amount, and type of anisometropia were not (P = 0.43, 0.68, 0.26, 0.47, respectively). None of the astigmatic or myopic patients achieved visual acuity of 20/20 in the amblyopic eye, while seven (39%) of the hyperopic patients did. This difference was significant (P = 0.03). Better initial stereoacuity predicted good final stereoacuity (P = 0.01). Only four (14%) patients developed amblyopia recurrence over an average follow-up period of 1.7 years. All were successfully treated with updated spectacles or patching.

CONCLUSIONS

Treatment of anisometropic amblyopia with spectacles alone can be a successful option. Patients treated with spectacles alone may experience a lower amblyopia recurrence rate than those treated with occlusion therapy.

Protein synthesis-independent plasticity mediates rapid and precise recovery of deprived eye responses

Monocular deprivation (MD) for a few days during a critical period of development leads to loss of cortical responses to stimulation of the deprived eye. Despite the profound effects of MD on cortical function, optical imaging of intrinsic signals and single-unit recordings revealed that deprived eye responses and orientation selectivity recovered a few hours after restoration of normal binocular vision. Moreover, recovery of deprived eye responses was not dependent upon mRNA translation, but required cortical activity. Interestingly, this fast recovery and protein synthesis independence was restricted to the hemisphere contralateral to the previously deprived eye. Collectively, these results implicate a relatively simple mechanistic process in the reactivation of a latent set of connections following restoration of binocular vision and provide new insight into how recovery of cortical function can rapidly occur in response to changes in sensory experience.

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.

Contrast sensitivity in amblyopia: the fellow eye of untreated and successfully treated amblyopes

PURPOSE

We sought to investigate contrast sensitivity on the fellow eyes of amblyopic and successfully treated amblyopic subjects.

METHODS

Contrast sensitivity was tested monocularly on both eyes of 48 amblyopic patients (mean age, 11.51 years) and of 22 successfully treated amblyopic subjects (visual acuity 20/20 in each eye; mean age, 11.22 years). Inclusion criteria were visual acuity in the amblyopic eye 20/40 or better (mild amblyopia) and 20/20 or better in the fellow eye, steady fixation, no signs of congenital, latent or manifest/latent nystagmus on clinical examination. Twenty normal subjects (20 eyes) were used as age-matched controls.

RESULTS

Contrast sensitivity functions from the fellow eye of the 48 amblyopic patients, even those who had never been treated with occlusion therapy before, were significantly decreased (P < 0.001) compared with control subjects. Both the previously amblyopic and the fellow eye of the 22 "cured" amblyopic subjects demonstrated significantly lower values (P < 0.001) compared with control patients.

CONCLUSIONS

We suggest that the nonamblyopic, "normal" eye of amblyopic patients behaves abnormally when evaluated for contrast sensitivity functions. Neither the previously amblyopic nor the fellow eyes of successfully treated subjects were comparable with controls. Occlusion therapy may not be implicated for depressed contrast sensitivity of the fellow eye in amblyopia. The assessment of contrast sensitivity can provide important information on the visual function and the influence of occlusion therapy in amblyopia.

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.

The relationship between anisometropia, patient age, and the development of amblyopia

PURPOSE

Anisometropia is a common cause of amblyopia. The relationship between anisometropia, patient age, and the development of amblyopia is unknown. Photoscreening identifies children with anisometropia in a manner that is not biased by visual acuity and allows a unique opportunity to evaluate how patient age influences the prevalence and depth of anisometropic amblyopia.

METHODS

A statewide preschool photoscreening program screened 120,000 children and identified 792 with anisometropia greater than 1.0 diopter. Age was correlated with visual acuity and amblyopia depth. Data were compared with those from 562 strabismic children similarly identified.

RESULTS

Only 14% (6/44) of anisometropic children aged 1 year or less had amblyopia. Prevalence was 40% (32/80) for 2-year-olds, 65% (119/182) for 3-year-olds, and peaked at 76% (age 5). Amblyopia depth also increased with age. Moderate amblyopia prevalence was 2% (ages 0 to 1), 17% (age 2), and rose steadily to 45% (ages 6 to 7). Severe amblyopia was rare prior to age 4, 9% at age 4, 14% at age 5, and 9% at ages 6 to 7. In contrast, children with strabismus had a stable prevalence of amblyopia (30% at ages 0 to 2, 42% at ages 3 to 4, 44% at ages 5 to 7).

CONCLUSIONS

Younger children with anisometropic refractive error have a lower prevalence and depth of amblyopia than do older children. By age 4, when most children undergo traditional screening, amblyopia has usually already developed. New vision screening technologies that allow early detection of anisometropia provide ophthalmologists an opportunity to intervene early, perhaps retarding, or even preventing, the development of amblyopia.

Recovery of Cortical Binocularity and Orientation Selectivity After the Critical Period for Ocular Dominance Plasticity

Cortical binocularity is abolished by monocular deprivation (MD) during a critical period of development lasting from approximately postnatal day (P) 35 to P70 in ferrets. Although this is one of the best-characterized models of neural plasticity and amblyopia, very few studies have examined the requirements for recovery of cortical binocularity and orientation selectivity of deprived eye responses. Recent studies indicating that different mechanisms regulate loss and recovery of binocularity raise the possibility that different sensitive periods characterize loss and recovery of deprived eye responses. In this report, we have examined whether the potential for recovery of binocularity and orientation selectivity is restricted to the critical period. Quantitative single unit recordings revealed recovery of cortical binocularity and full recovery of orientation selectivity of deprived eye responses following prolonged periods of MD (i.e., >3 wk) starting at P49, near the peak of plasticity. Surprisingly, recovery was present when binocular vision was restored after the end of the critical period for ocular dominance plasticity, as late as P83. In contrast, ferrets that had never received visual experience through the deprived eye failed to recover binocularity even though normal binocular vision was restored at P50, halfway through the critical period. Collectively, these results indicate that there is potential for recovery of cortical binocularity and deprived eye orientation selectivity after the end of the critical period for ocular dominance plasticity.

The emotional impact of amblyopia treatment in preschool children

PURPOSE

To investigate the emotional status of children undergoing active treatment for amblyopia.

DESIGN

Postal survey, in the context of a prospective, multicenter, randomized controlled trial.

PARTICIPANTS

Parents of 177 children with a unilateral visual impairment referred from preschool vision screening. The children had been recruited to a randomized controlled trial of treatment for unilateral visual impairment and randomly assigned to receive either glasses with or without patches, glasses alone, or treatment deferred for 1 year.

METHODS

A self-completion questionnaire, including a psychometric behavioral scale, was sent to the parents of all children recruited to the trial at age 4 years, to 66 whose deferred treatment began at age 5 years, and finally to 151 remaining in the trial at the end of follow-up.

MAIN OUTCOME MEASURES

Mean scores per treatment group on the Revised Rutter Parent Scale for Preschool Children. Comparison of parent responses to questions assessing the child's general well-being and difficulties associated with treatment.

RESULTS

Completed questionnaires were returned for 144 of 177 (81%) children at a mean age (standard deviation) of 48 months (5.0), for 45 of 66 (68%) at a mean age of 61 months (5.8), and for 78 of 151 (52%) at a mean age of 67 months (5.0). Most parents reported having difficulty with patching their child regardless of age (77% at age 4 years and 73% at age 5 years), with fewer reporting difficulties with glasses alone (42% and 53%, respectively). Children were significantly more upset by patching than by glasses only (chi-square test, P = 0.03 for age 4 years and P = 0.01 for age 5 years), as were the parents of 4-year-olds (chi-square test, P = 0.01). Most parents thought their children were happy, cooperative, and good tempered, and behavioral scores did not differ between treatment groups.

CONCLUSIONS

Treatment for unilateral visual impairment is not easy to implement and is commonly associated with some degree of distress. Despite this, no impact on the child's global well-being or behavior was seen either during or after the treatment period.

Randomised controlled trial of treatment of unilateral visual impairment detected at preschool vision screening

OBJECTIVES

To test the efficacy of treatment for unilateral visual loss detected by preschool vision screening and the extent to which effectiveness varies with initial severity.

DESIGN

Randomised controlled trial of full treatment with glasses and patching, if required, compared with glasses only or no treatment. Masked assessment of best corrected acuity after one year of follow up.

SETTING

Eight UK eye departments.

PARTICIPANTS

177 children aged 3-5 years with mild to moderate unilateral impairment of acuity (6/9 to 6/36) detected by screening.

RESULTS

Children in the full and glasses treatment groups had incrementally better visual acuity at follow up than children who received no treatment, but the mean treatment effect between full and no treatment was equivalent to only one line on a Snellen chart (0.11 log units; 95% confidence interval 0.050 to 0.171; P < 0.0001). The effects of treatment depended on initial acuity: full treatment showed a substantial effect in the moderate acuity group (6/36 to 6/18 at recruitment) and no significant effect in the mild acuity group (6/9 to 6/12 at recruitment) (P = 0.006 for linear regression interaction term). For 64 children with moderate acuity loss the treatment effect was 0.20 log units, equivalent to one to two lines on a Snellen chart. When all children had received treatment, six months after the end of the trial, there was no significant difference in acuity between the groups.

CONCLUSIONS

Treatment is worth while in children with the poorest acuity, but in children with mild (6/9 to 6/12) unilateral acuity loss there was little benefit. Delay in treatment until the age of 5 did not seem to influence effectiveness.

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.

Pediatric Eye Disease Investigator Group. 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.

Differences in the management of amblyopia between European countries

BACKGROUND

Amblyopia treatment is not standardised and differences between centres and countries have not been systematically investigated. This survey compares the different patterns of orthoptic treatment of amblyopia in the United Kingdom (UK) and three German speaking countries (GSC).

METHODS

Questionnaires were sent to orthoptists in the UK and the GSC asking for their preferred choices of treatment of amblyopia between the ages of 6 months to 10 years.

RESULTS

The following significant differences in management of amblyopia were found: (1) the number of hours of occlusion per week was higher in the GSC, p<0.0001, (2) orthoptists in the GSC treat amblyopia up to an older age. Orthoptists in the GSC and in the UK predicted similar treatment outcomes.

CONCLUSION

Orthoptists in the GSC usually treat patients more intensively and for longer, while the prediction of visual outcome does not differ significantly between countries. These results highlight the lack of standardisation in the treatment of the various types of amblyopia.

Prediction of improved vision in the amblyopic eye after visual loss in the non-amblyopic eye

Amblyopia arises from abnormal visual experiences in early childhood. Improved function of the amblyopic eye after visual loss in the non-amblyopic eye could be a model for residual neural plasticity. We aimed to establish the likelihood of, and predictive factors for, this improvement in function. We identified 254 individuals aged 11 years or older with unilateral amblyopia who were visually impaired after loss of vision in their non-amblyopic eye but had no other disorder affecting their amblyopic eye. 25 (10%) of 254 people had improved visual acuity in their amblyopic eye. These findings suggest there is some plasticity in the visual system of a few visually mature individuals with amblyopia, which warrants further study. Children should remain the focus of detection and treatment.

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

BACKGROUND/AIMS

The effectiveness of occlusion therapy for the treatment of amblyopia is a research priority. The authors describe the design of the Monitored Occlusion Treatment for Amblyopia Study (MOTAS) and its methodology. MOTAS will determine the dose-response relation for occlusion therapy as a function of age and category of amblyopia.

METHODS

Subjects progress through up to three study phases: (1) Assessment and baseline phase: On confirmation of eligibility, and after parental consent, baseline visual functions are determined, and spectacles prescribed as necessary; (2) Refractive adaptation phase: Subjects wear spectacles full time and return to clinic at 6 weekly intervals until 18 weeks, by which time all improvement due to refractive correction is complete; (3) Occlusion phase: All subjects are prescribed 6 hours of occlusion per day. Daily occlusion is objectively monitored using an occlusion dose monitor (ODM).

OUTCOME VARIABLES

visual acuity (logMAR charts), log contrast sensitivity (Pelli-Robson chart), and stereoacuity (Frisby) are assessed at 2 weekly intervals until gains in visual acuity cease to be statistically verifiable.

CONCLUSION

Four methodological issues have been addressed; firstly, baseline stability of visual function; secondly, differentiation of refractive adaptation from occlusion; thirdly, objective measurement of occlusion dose and concordance; fourthly, use of validated outcome measures.

Remediation of refractive amblyopia by optical correction alone

Amblyopia--the commonest vision abnormality of childhood--is characterized by a loss of visual acuity usually of one eye only. Treatment aims to promote function of the amblyopic eye and does this by restricting, usually through occlusion, the competitive advantage of the fellow eye. Recent experimental evidence demonstrates that the recovery of vision following early deprivation is facilitated by increasing visually evoked activity. An analogous approach in humans is to minimise image blur by correcting refractive error prior to treatment--a practice which may account for the poorly quantified improvements in visual acuity sometimes attributed to 'spectacle adaptation'. Here we describe clinically significant gains in visual acuity obtained over a period of 4-24 weeks in a group of amblyopic children arising solely in response to the correction of refractive error. Consequences for the clinical management of refractive amblyopia are discussed.

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.

Amblyopia: is visual loss permanent?

AIM

To ascertain whether recovery of visual function in amblyopic eyes is likely to occur when the fellow eye is lost as a result of age related macular degeneration.

METHODS

The records of 465 patients with an established diagnosis of age related macular degeneration who had attended a specialist macular clinic between 1990 and 1998 were scrutinised. A full clinical examination and standardised refraction had been carried out in 189 of these cases on a minimum of two occasions. Cases were looked for where an improvement of one or more lines of either distance or near acuity was recorded in the eye unaffected by macular disease. In each one of these cases the improvement in visual acuity could not be attributed to treatment of other existing pathology.

RESULTS

12 such cases were detected. In nine of these the eye showing improvement of acuity had a history of amblyopia. The mean improvement in distance and near acuity in amblyopic eyes by 12 months was 3.3 and 1.9 lines logMAR respectively. The improvement in acuity generally occurred between 1 and 12 months from baseline and remained stable over the period of follow up.

CONCLUSIONS

Older people with a history of amblyopia who develop visual loss in the previously normal eye can experience recovery of visual function in the amblyopic eye over a period of time. This recovery in visual function occurs in the wake of visual loss in the fellow eye and the improvement appears to be sustained.

Efficacy of occlusion for strabismic amblyopia: can an optimal duration be identified?

BACKGROUND/AIMS

The study of occlusion efficacy in amblyopia has been hampered by the use of non-logMAR acuity tests and a failure to assess threshold acuity for both eyes. These issues are addressed in the current study which compares the effect of spectacles alone and spectacles in combination with occlusion, with the use of the logMAR crowded test.

METHODS

Changes in uniocular and interocular acuity differences were compared for two age matched groups of previously untreated children with strabismic amblyopia: one compliant with spectacles only (n = 17, mean 6.2 (SD 2.5) years) and the other with spectacles and occlusion (n = 69, mean 5.1 (1) years) over a 1 year period. Changes in logMAR acuity were also analysed for a larger occluded group (n = 119) in response to successive 200 hour blocks of occlusion up to > or =1000 hours, in an attempt to isolate an optimal occlusion regime.

RESULTS

Visual acuity improved for more of the amblyopic eyes of the occluded (74%) than the spectacles only group (59%), and only one child from the latter group deteriorated. Mean visual acuity improved for both eyes of both treatment groups, but the change was significantly larger for the strabismic eyes of the occluded group overall and within the first 6 month period (p <0. 05). Occlusion was only effective for the first 400 hours worn. Subsequent visual improvement was bilateral and symmetrical.

CONCLUSION

Occlusion is more effective in the treatment of strabismic amblyopia than spectacles alone, and the effect is optimal within the first 6 months of wear. In terms of occlusion duration, maximal improvement occurs in response to 400 hours of occlusion wear or less, and to full time occlusion. Visual maturation continues, but is retarded for amblyopic eyes.