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PubMed1979

Some functional abnormalities in amblyopia.

In discussing the relationship between anomalous retinal correspondence and amblyopia, it is suggested that amblyopia may be due not only to suppression and/or non-use of the deviated eye, but also to a mis-use of this eye. The interaction of the 'focal' and 'ambient' systems in amblyopia and the relationship of the 'ambient' system to the interocular transfer of the motion after-effect are discussed. This effect has been found to be of no clinical significance in predicting the presence or absence of binocular cooperation. It is concluded that in cases of amblyopia there is either no disturbance in the 'ambient' system or an adaptation of the latter to the pathological condition.

Adolescent↗
PubMed1988

Clinical suppression and amblyopia.

In individuals with abnormal binocular vision, such as strabismics and anisometropes, it is common for all or part of one eye's view to be suppressed so binocular confusion and diplopia are eliminated. We examined the relation between the depth of suppression (the amount by which the monocular contrast increment threshold for an eye was elevated by stimulation in the contralateral eye) and the degree of amblyopia (difference in monocular contrast thresholds for the two eyes). There was a significant negative correlation between suppression and amblyopia, so that clinical suppressors with no amblyopia exhibited deep suppression (ie, large threshold elevation) while observers with amblyopia exhibited weaker or no suppression. This negative correlation was found when the two eyes viewed orthogonally oriented contours as well as identically oriented contours. These results suggest that when an eye is amblyopic there is no longer a need for strong suppression of that eye by the contralateral eye.

Amblyopia↗
PubMed1985

[Current epidemiology of strabismic amblyopia in France].

It is well known that good early management of squint prevents the appearance of functional amblyopia and, when it exists, allows a cure in more than 90% of cases. The authors report a series of 1 552 esotropias. Statistical analysis reveals that the present epidemiologic state of functional amblyopia is dismal. 47% of cases have an amblyopia in spite of 64.6% of children being previously treated. The mean age is 7 years 6 months. The therapeutic results after a 6 months range still shows 38% of poorly applied treatment, but 57% of well-managed patients recover normal visual acuity. The long range results (average 33 months) show that in 47% of cases the treatment was badly applied. On the contrary, 70% of patients having good management were successful. Two main reasons explain such a situation : firstly the lack of information and casualness of parents; and on the other hand faltering and unsuitable medical technics. The only real answer to such a problem is early medical management of every squint. According to the author's experience it seems that such a state is not a special feature of amblyopia epidemiology in the western part of France, but it is observed in the same way in many countries having high level medical care.

Age Factors↗
PubMed1979

Fixational eye movements in amblyopia and strabismus.

Horizontal eye position was monitored using a photoelectric method during monocular and binocular fixation in four patients having amblyopia without strabismus, thirteen patients having constant strabismus with amblyopia, and five patients having intermittent strabismus. Four abnormalities of fixation were found: increased drift, saccadic intrusions, manifest nystagmus, and latent nystagmus. Increased drift was related to the presence of amblyopia, while saccadic intrusions and nystagmus were related to the presence of strabismus. Understanding dynamic aspects of oculomotor control can provide insight into clinical assessment of fixation in amblyopia and strabismus.

Adolescent↗
PubMed1982

Competitive neuronal interactions underlying amblyopia.

Amblyopia, a Greek word meaning "blunt sight" refers to a common clinical condition characterised by lowered visual capacities in one or both eyes. Several different types of amblyopia have been defined and in the most common forms, strabismic and anisometropia amblyopia, one eye finds itself at a severe disadvantage relative to its counterpart. The evidence to be presented in this article will show that the reduction of visual capacities in one eye results from competition between binocular inputs rather than simply reflecting disuse of one eye. In addition, evidence will be represented to show that this binocular competition occurs in the visual cortex rather than in the periphery. In fact, there appear to be at least two separate levels of binocular competition within the visual cortex. Under most circumstances, it is possible to induce or to reverse amblyopia only during a well-defined sensitive period early in the life of the organism. With special efforts, however, prolongation of this sensitive period can be achieved and plasticity of cortical ocular dominance maintained into adulthood.

Amblyopia↗
PubMed1982

[Prevention and treatment of amblyopia in children under two years of age (author's transl)].

Numerous observations in children under two years of age tend to demonstrate that the functional amblyopia of esotropia is not congenital in origin, but develops progressively between the ages of 3 months and 2 years. The initial motor disorder is an abduction deficiency. When this is symmetrical there is no amblyopia, but there is a greater risk for the deviated eye to become amblyopic when the deficiency is, or becomes, asymmetrical. Preventive treatment of the amblyopia involves the wearing of symmetrical nasal sectors, with associated partial occlusion in established cases, duration of which depends upon the child's age. Marked amblyopia with nasal fixation requires the use of a nasal sector placed in front of the amblyopic eye (associated with occlusion of the normal eye).

Amblyopia↗
PubMed1995

Conjugacy of saccades in deep amblyopia.

PURPOSE: To determine the degree of conjugacy of saccades in humans with one deeply amblyopic eye, to assess whether Hering's law requires good binocular visual acuity. METHODS: By means of magnetic search coils, horizontal saccades were recorded accurately in 11 subjects with unilateral, deep amblyopia. The recordings were compared to those made in 11 normal subjects. In addition, three subjects with amblyopia were submitted to artificial anisometropia, which called for nonconjugate adaptation of their saccades. RESULTS: The saccades of most subjects with amblyopia were nonconjugate. These nonconjugacies often were larger in one direction than in the opposite one. The magnitude of the nonconjugacies varied inconsistently with the size of the saccades. In addition, the amblyopic eye often showed conspicuous drift. The saccades adapted nonconjugately to the imposed anisometropia. CONCLUSIONS: In deep amblyopia, the two eyes often make saccades that are unequal in size. The amblyopic eye does not move aimlessly, roughly following the movements of the normal fellow eye. Instead, the saccades of the amblyopic eye appear to reflect a deliberate oculomotor strategy, bringing visual targets to presumed retinal points of preference.

Adaptation, Ocular↗
PubMed1995

[The visual evoked potentials of non-amblyopic eyes in children with amblyopia].

We investigated the characteristics of visual evoked potentials (VEPs) of the eyes with normal visual acuity in 84 children of whom 20 were normal, 28 of anisometropic amblyopia, 8 of anisometropic amblyopia already cured, 8 pairs of monozygotic and 6 pairs of dizygotic twins with amblyopia. The results showed that although the fellow eye of an amblyopic eye or the cured amblyopic eye had normal visual acuity, the VEPs presented abnormal, the marked abnormality being the prolongation of the latency of P100 peak. No significant difference was found in VEPs between the eye with normal visual acuity and the eye with amblyopia in the monozygotic twins with the same genetic background (P > 0.05). This study demonstrated that possibly the clinical examinations of visual acuity and VEPs reflect different visual information processes, and the "normal" eyes of amblyopes are not normal.

Amblyopia↗
PubMed1996

Neuronal basis of amblyopia: a review.

Amblyopia is an acquired defect in vision due to an abnormal visual experience during a sensitive period of visual development. The neuronal basis of amblyopia is the study of the effects of "abnormal" environmental influences on the genetically programmed development of the visual processing system. Visual pathway development commences with ganglion cells forming the optic nerve. The process that guides these neurones initially to the lateral geniculate nucleus (LGN) and then onto the visual cortex is genetically programmed. Initially this process is influenced by spontaneously generated impulses and neurotrophic factors. Following birth, visual stimuli modify and refine the genetically programmed process. Exposure to the visual environment includes the risk of abnormal inputs. Abnormal stimuli disrupt the formation of patterned inputs allowing alteration of visual cortical writing with reduction in ocular dominance columns driven by the abnormal eye. Correction of the abnormal visual input and penalisation of the "normal" input is the mainstay of therapy for amblyopia. Further understanding of the mechanisms involved in the development of a normal visual processing system will allow trialing therapies for amblyopia not responding to occlusion therapy. Levodopa is one agent providing insights into recovery of visual function for short periods in apparently mature visual systems.

Amblyopia↗
PubMed1996

A comparison of tests to determine acuity deficits in children with amblyopia.

The usefulness of the Cardiff Acuity Test in the detection of amblyopia was evaluated. Visual function was measured using pattern visual evoked potentials (VEPs), the Cardiff test, and the Bailey-Lovie Chart in 21 visually normal children and 12 children with amblyopia. The Cardiff test gave higher scores than the Bailey-Lovie test. The Cardiff test identified five of the 12 children who were classified as amblyopic by the Bailey-Lovie test. Interocular VEP latency differences identified eight of the 12 children with amblyopia; interocular VEP amplitudes correctly identified nine. We suggest that the challenging Bailey-Lovie test be used for older children who know their letters well. If the Bailey-Lovie test cannot be used, VEPs give the most accurate assessment of interocular differences. The Cardiff test holds a bored child's attention and allows the examiner to obtain a useful measure of visual acuity, but it cannot detect mild amounts of amblyopia.

Adolescent↗
PubMed1996

[Amblyopia, refractive errors and strabismus in congenital ptosis].

The incidence of amblyopia in the normal population is 2-6%, whereas among patients with congenital ptosis it can be as high as 50%. We reviewed 146 cases of congenital ptosis in patients aged between 5 months and 15 years and compared them to a control group of 34 age- and sex-matched patients. In 78 children (156 eyes) reliable optotype visual acuity could be obtained. Fifty-three eyes (34%) were amblyopic. Ametropia was responsible for 34% and anisometropia for 28.3% of the amblyopia cases. In 25.4% of cases strabismus, and in 11.34% stimulus deprivation, was the reason for the development of amblyopia. Children with congenital ptosis should have retinoscopy done in cycloplegia, and refractive errors should be corrected early. Controlled patching therapy should also be started early. Since stimulus deprivation amblyopia is rare, congenital ptosis need not be corrected early in life.

Amblyopia↗
PubMed1997

Improvement in Vernier acuity in adults with amblyopia. Practice makes better.

PURPOSE: To determine the nature and limits of visual improvement through repetitive practice in human adults with naturally occurring amblyopia. METHODS: A key measure the authors used was a psychophysical estimate of Vernier acuity; persons with amblyopia have marked deficits in Vernier acuity that are highly correlated with their loss of Snellen acuity. The experiment consisted of three phases: pretraining measurements of Vernier acuity and a second task (either line-detection thresholds or Snellen acuity) in each eye with the lines at two orientations; a training phase in which observers repetitively trained on the Vernier task at a specific line orientation until each had completed 4000 to 5000 trials; and posttraining measurements (identical to those in the first phase). Two groups of amblyopic observers were tested: novice observers (n = 6), who had no experience in making psychophysical judgments with their amblyopic eyes, and experienced observers (n = 5), who had previous experience in making Vernier judgments with their amblyopic eyes (with the lines at a different orientation) using the signal-detection methodology. RESULTS: The authors found that strong and significant improvement in Vernier acuity occurs in the trained orientation in all observers. Learning was generally strongest at the trained orientation but may partially have been transferred to other orientations (n = 4). Significant learning was transferred partially to the other eye (at the trained orientation) in two observers with anisometropic amblyopia. Improvement in Vernier acuity did not transfer to an untrained detection task. In two observers, the improvement in Vernier acuity was accompanied by a commensurate improvement in Snellen acuity. CONCLUSIONS: Some adults with amblyopia retain a significant degree of neural plasticity. Although several observers (primarily novices) showed evidence of generalized learning, several amblyopic patients showed evidence for improvement that was orientation and task specific. In this latter group of observers, the improvement appeared to reflect alterations that were, at least in part, in early neural processes that were orientation specific and were localized beyond the site of convergence of the two eyes.

Adult↗
PubMed1998

Nutritional amblyopia.

A review was conducted to examine the characteristics and pathogenesis of nutritional amblyopia. Published cases of amblyopia among malnourished allied prisoners of the Japanese during World War II and among Cubans malnourished during the recent economic embargo were analyzed. The picture of nutritional amblyopia derived from these publications is somewhat at variance with the conventional image of the disease. Surprising features include premonitory keratopathy, rapid onset of visual loss, a high incidence of hearing loss, and the presence of peripapillary retinopathy in some cases. No single causative factor can be identified. Genetic susceptibility rarely, if ever, plays a role. Vitamin deficiency may not be important. Protein deficiency, antioxidant deficiency, physical labor, and tobacco smoking are likely to contribute to the occurrence of amblyopia.

Amblyopia↗
PubMed1998

[Results of investigations of visual evoked potentials in the treatment of amblyopia].

PURPOSE: The aim of the study is to demonstrate the changes in visual evoked potentials (VEP) in treatment of amblyopia. MATERIAL AND METHODS: Pattern reversal VEP of 28 children treated because of amblyopia and 16 healthy persons were analysed. Before treatment and after treatment the results of the interocular amplitude difference ratio and interocular latency difference ratio were compared with standards. RESULTS: After treatment of amblyopia the percentage of normal interocular amplitude and latency difference ratios increased. CONCLUSION: Study of pattern VEP enables monitoring of amblyopia treatment.

Amblyopia↗
PubMed2002

[Amblyopia of the fellow eye in assumed unilateral congenital fibrosis syndrome].

BACKGROUND: Amblyopia of the ptotic eye in spite of head posturing and of the fellow eye in ptosis with motility disorders are well known. We emphasize the importance of exact ophthalmological and orthoptic examinations to avoid amblyopia in both ptosis and fellow eye, even in cases of mild ptosis, especially if they are combined with motility disorders. PATIENT: A 5 year-old girl presented to our outpatient clinic because of ptosis of the left eye and hypertropia of the right eye. Visual acuity of the right eye was 0.32 and of the left ptotic eye 1.0. Cycloplegic retinoscopy showed + 2.0 sphere in both eyes. Ocular motility showed a mild reduction of elevation of the left eye in ad- and abduction. This led to the diagnosis of congenital fibrosis syndrome of the inferior rectus muscle of the left eye. Due to the preferred fixation with the left ptotic eye and the consecutive deviation of the fellow eye amblyopia of the right eye had developed. Occlusion therapy of the left eye resulted in an improvement of visual acuity of the right eye to 0.9 and centralisation of fixation within one month. CONCLUSION: Even children with mild ptosis, especially in combination with motility disorders, require a complete ophthalmological and orthoptic examination to avoid amblyopia also of the fellow eye.

Blepharoptosis↗
PubMedDate not supplied

Considerations in the routine assessment and treatment of anisometropic amblyopia.

Anisometropic amblyopia has traditionally been treated by direct occlusion with or without refractive correction of the anisometropia. This treatment has generally been considered so successful that practitioners prescribe occlusion for a time and consider treatment complete when visual acuity is no longer improving. The aetiology of anisometropic amblyopia, addressing the functional deficits of the amblyopic system and patient compliance issues, are important to the success of amblyopia treatment in anisometropia and are briefly reviewed in this paper. We propose that, while each case of anisometropic amblyopia may have slightly different attributes, initially they should all be treated with occlusion and full-time spectacle correction. Some presentations may be responsive to individual treatment strategies to correct binocular functions such as stereopsis, accommodative response and fusional vergences.

Journal Article↗
PubMed2002

A randomized trial of atropine vs. patching for treatment of moderate amblyopia in children.

OBJECTIVE: To compare patching and atropine as treatments for moderate amblyopia in children younger than 7 years. METHODS: In a randomized clinical trial, 419 children younger than 7 years with amblyopia and visual acuity in the range of 20/40 to 20/100 were assigned to receive either patching or atropine at 47 clinical sites. MAIN OUTCOME MEASURE: Visual acuity in the amblyopic eye and sound eye after 6 months. RESULTS: Visual acuity in the amblyopic eye improved in both groups (improvement from baseline to 6 months was 3.16 lines in the patching group and 2.84 lines in the atropine group). Improvement was initially faster in the patching group, but after 6 months, the difference in visual acuity between treatment groups was small and clinically inconsequential (mean difference at 6 months, 0.034 logMAR units; 95% confidence interval, 0.005-0.064 logMAR units). The 6-month acuity was 20/30 or better in the amblyopic eye and/or improved from baseline by 3 or more lines in 79% of the patching group and 74% of the atropine group. Both treatments were well tolerated, although atropine had a slightly higher degree of acceptability on a parental questionnaire. More patients in the atropine group than in the patching group had reduced acuity in the sound eye at 6 months, but this did not persist with further follow-up. CONCLUSION: Atropine and patching produce improvement of similar magnitude, and both are appropriate modalities for the initial treatment of moderate amblyopia in children aged 3 to less than 7 years.

Amblyopia↗
PubMed2003

A randomized trial of patching regimens for treatment of moderate amblyopia in children.

OBJECTIVE: To compare 2 hours vs 6 hours of daily patching as treatments for moderate amblyopia in children younger than 7 years. METHODS: In a randomized multicenter (35 sites) clinical trial, 189 children younger than 7 years with amblyopia in the range of 20/40 to 20/80 were assigned to receive either 2 hours or 6 hours of daily patching combined with at least 1 hour per day of near visual activities during patching.Main Outcome Measure Visual acuity in the amblyopic eye after 4 months. RESULTS: Visual acuity in the amblyopic eye improved a similar amount in both groups. The improvement in the visual acuity of the amblyopic eye from baseline to 4 months averaged 2.40 lines in each group (P =.98). The 4-month visual acuity was at least 20/32 and/or improved from baseline by 3 or more lines in 62% of patients in each group (P>.99). CONCLUSION: When combined with prescribing 1 hour of near visual activities, 2 hours of daily patching produces an improvement in visual acuity that is of similar magnitude to the improvement produced by 6 hours of daily patching in treating moderate amblyopia in children aged 3 to 7 years.

Amblyopia↗