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PubMed1993

Depth of anisometropic amblyopia and difference in refraction.

Disagreement exists as to whether the depth of anisometropic amblyopia correlates with the degree of anisometropia. We reviewed the charts of 303 consecutive patients with the diagnosis of amblyopia. Thirty-five patients with untreated anisometropia without strabismus were identified. The best-corrected visual acuities, manifest refractions, and autorefractions were recorded. The differences in spherical equivalent, root mean square, and an index of anisometropia, which we defined, were calculated. The depth of amblyopia was strongly correlated to all three measures of anisometropia for both hyperopic and myopic individuals. Our new index of anisometropia was an excellent predictor of the depth of amblyopia.

Adolescent↗
PubMed1999

Automated perimetry in amblyopia: a generalized depression.

PURPOSE: To quantitate the visual field abnormalities associated with amblyopia. METHODS: In a prospective study, 37 amblyopic patients (11 anisometropic, 13 strabismic, 9 combination, 4 deprivation) performed automated perimetry in each eye using the Humphrey 30-2 program. Primary outcome measures were foveal threshold, mean deviation, and average threshold. RESULTS: When the probability plots were examined, 21 visual fields in amblyopic eyes were normal, 8 had central scotomas, and 7 had diffuse depressions. No focal defects other than mild central scotomas were seen. However, the foveal threshold of amblyopic eyes was decreased by an average of 7.2 +/- 8.0 dB (P < .0001) compared with fellow eyes; intereye differences in mean deviation (3.2 +/- 5.4 dB; P < .001) and average threshold (2.9 +/- 5.3 dB; P < .005) were also seen. This decrease in sensitivity for the amblyopic eye occurred for all types of amblyopia. The depression in threshold was greatest at the fovea but was detectable and significant at all eccentricities of the 30-degree field. The average threshold in the amblyopic eye was highly correlated with visual acuity (r = .839; P < .001). CONCLUSIONS: Although automated visual fields in amblyopic eyes typically appear normal, all four types of amblyopia are associated with a generalized depression of light sensitivity, which is proportionately greatest at the fovea and highly correlated with visual acuity loss. In general, amblyopia is not associated with any area of focal loss of threshold light sensitivity. If a focal defect is present in the visual field of the amblyopic eye, organic causes of visual loss should be suspected. The Humphrey visual field analyzer STATPAC program (Allergan-Humphrey, Inc, San Leandro, California) may artifactually transform small and generalized full-field depressions in a manner that makes them appear to be isolated central defects.

Adult↗
PubMed1987

Amblyopia: definition, classification, diagnosis, and management considerations for pediatricians, family physicians, and general practitioners.

Amblyopia is a reduction in the quality of central, corrected vision resulting from a disturbance in retinal image formation during the first decade of human life. Although the neurophysiology and neuropathology of amblyopia are now better understood than in the past, treatment has not changed significantly in more than 200 years. The earlier amblyopia is detected, the shorter the duration of treatment required to reduce its severity. The mainstay of treatment still consists of forcing the use of the amblyopic eye, most often by occlusion of the sound eye. Complications of treatment include occlusion amblyopia and induction of strabismus in straight-eyed patients.

Amblyopia↗
PubMed1998

Contour integration in anisometropic amblyopia.

Contour integration was measured in a group of anisometropic amblyopes to test the idea recently put forward that positional uncertainty sets a fundamental limit to contour integration in amblyopia. Anisometropic amblyopia, unlike strabismic amblyopia, has little or no positional uncertainty once the initial filtering loss has been taken into account. Therefore, according to the explanation put forward to explain strabismic amblyopia, anisometropes should exhibit normal contour integration. We show that this expectation is realized for five of our six anisometropic amblyopes.

Adult↗
PubMed1999

The orientation discrimination deficit in strabismic amblyopia depends upon stimulus bandwidth.

We show that the previously reported orientation deficit in amblyopia (Skottun, B. C., Bradley, A., & Freeman, R. D. (1986). Orientation discrimination in amblyopia. Investigative Ophthalmology and Visual Science, 30, 532-537) also occurs for arrays of randomly positioned Gabor micropatterns for which explanations based on either neural disarray or local neural interactions would not hold. Furthermore, when using Gabors, we show that the deficit varies with the spatial frequency and orientational bandwidth of the stimuli used to measure it. We discuss two competing explanations for this, one based on a broader underlying detector bandwidth in amblyopia (both orientation and spatial frequency) and the other based on a selective deficit of first-order, as opposed to second-order orientation processing in strabismic amblyopia. Our results favour the latter interpretation.

Amblyopia↗
PubMed2002

The minimum occlusion trial for the treatment of amblyopia.

OBJECTIVE: To determine whether the traditional regimen of three intervals of full-time occlusion (FTO) for amblyopia without any measurable improvement in visual acuity constitutes an adequate trial. DESIGN: Retrospective, noncomparative, interventional case series. PARTICIPANTS: Sixty-four children younger than 10 years of age with unilateral amblyopia. METHODS: The medical records of patients treated for amblyopia in a university outpatient clinic were reviewed. Patients who underwent one FTO interval without an improvement in visual acuity followed by at least one additional FTO interval were included in the study. MAIN OUTCOME MEASURES: Improvement in visual acuity. RESULTS: Sixty-four patients underwent 81 occlusion trials consisting of one FTO interval without improvement followed by one or more FTO intervals. Visual acuity improved after the second FTO interval in 25 (31%) of the trials. Of the 44 occlusion trials consisting of two FTO intervals without improvement, visual acuity improved after the third FTO interval in 12 (27%) of the trials. Of the 11 occlusion trials consisting of three FTO intervals without improvement followed by one or more additional FTO intervals, acuity did not improve with any of the trials. CONCLUSIONS: A minimum of three intervals of FTO is necessary to determine whether an amblyopia patient will be unresponsive to occlusion therapy. After three FTO intervals without improvement, additional FTO is unlikely to result in an improvement in visual acuity.

Amblyopia↗
PubMed1993

The sensitive period for strabismic amblyopia in humans.

PURPOSE: In order to assess the sensitive period for strabismic amblyopia, the period of susceptibility to monocular occlusion was investigated in 407 children who ranged in age from 21 months to 12 years. METHODS: Patients were treated between 1975 and 1990 by occlusion of the best eye. The efficiency of the treatment was measured as the ratio of reduction of the amblyopia at the end of the occlusion. RESULTS: The efficiency of the occlusion is shown to depend on the age of the onset of the treatment: recovery of acuity of the amblyopic eye was maximum when the occlusion was initiated before 3 years of age, decreased as a function of age and was about null by the time the patient was 12 years of age. CONCLUSION: This is assumed to be an indication of the sensitive period for strabismic amblyopia in humans. The results are discussed on the basis of the neurophysiological mechanisms of amblyopia established in animals.

Age Factors↗
PubMed1978

Application of basic research data to clinical amblyopia.

The rhesus monkey has evolved as a useful model for the study of amblyopia caused by neonatal lid closure and experimental strabismus and anisometropia. In view of the behavioral and anatomic similarities of the visual system in humans and rhesus monkeys, there is reason to believe that the neurophysiologic and anatomic anomalies identified in animals as part of the "visual deprivation syndrome" occur in humans as well. Animal research has led to better understanding of the basic mechanisms responsible for the development of amblyopia and the manner in which form vision deprivation and abnormal binocular interaction contribute to the various forms of unilateral and bilateral amblyopia. The period of susceptibility to abnormal visual stimulation in humans needs to be better defined, and the clinician must take precautions to avoid uncontrolled occlusion or prolonged unilateral cycloplegia in infants. Even though the factors leading to amblyopia in patients with unilateral or bilateral congenital cataracts are now better understood, the visual results are still disappointing. It is possible that the residual aniseikonia after contact lens correction may be amblyopiogenic in these patients.

Adult↗
PubMed1992

Results of amblyopia therapy in eyes with unilateral structural abnormalities.

PURPOSE: The purpose of this study is to analyze the visual results of full-time occlusion therapy in pediatric patients with monocular structural abnormalities and amblyopia. METHODS: The authors reviewed the charts of visually immature patients with unilateral structural abnormalities and decreased visual acuity, who presented to the University of Iowa Hospitals and Clinics over a 20-year period, and underwent amblyopia therapy. The results were categorized according to the type of structural abnormality (i.e., partial media opacity, macula lesion, or optic nerve abnormality). Associated factors, including anisometropia, strabismus, age of presentation, and pupillary responses, were analyzed. RESULTS: Fifty-one percent of the 51 patients in the study achieved a visual acuity of at least 20/80, including 72% of the patients with media opacities, 42% with macular lesions, and 21% with optic nerve anomalies. Strabismus and anisometropia occurred frequently and were not prognostically significant. Relative afferent pupillary defects did not contraindicate good results. Amblyopia recurred in 31% of patients and was successfully treated with resumption of full-time occlusion. Occlusion amblyopia occurred in only one patient and was easily reversed. CONCLUSION: The authors recommend a trial of full-time occlusion for patients with all three types of unilateral structural abnormalities. The patients with partial media opacities have a high success rate. Despite lower success rates for the other two groups, good results are possible; no better treatment option exists.

Amblyopia↗
PubMed1997

Penalization versus part-time occlusion and binocular outcome in treatment of strabismic amblyopia.

OBJECTIVE: The purpose of the study is to compare the visual outcome of occlusion versus penalization treatment of strabismic amblyopia, with particular attention to binocularity outcome. DESIGN: The study design was a retrospective study. PARTICIPANTS: Patients with strabismic amblyopia, 75 receiving penalization alone, 87 with a history of occlusion treatment who were later treated by penalization, and 30 treated by means of part-time occlusion (2 to 6 hours/day) participated in this study. MAIN OUTCOME MEASURES: Logarithm of the minimum angle of resolution (logMAR) visual acuity and binocularity index were measured. RESULTS: No statistically significant difference was found between outcomes for the penalization groups with and without a history of occlusion, either by univariate analysis or by multivariate analysis controlling for initial-visit age, acuity, and binocularity status. One marginally significant outcome difference was found between the pure penalization and part-time occlusion groups by univariate analysis, but no significant difference was found in the multivariate analyses controlling for the same three variables at the initial visit. All visual outcome differences between the pure penalization and part-time occlusion groups were less than 1 logMAR line visual acuity or less than a half-unit on the binocularity index. CONCLUSIONS: The study provided no evidence of a difference in visual function outcome between penalization and occlusion, in terms of either statistical or clinical significance, although limitations of the patient samples used preclude these data from showing conclusively that there was no such difference. The lack of any other study adequately comparing these two treatment methods, in combination with the current study's demonstration of the difficulty of making adequate retrospective-based comparison despite a large patient base (n = 1413), suggests that a large prospective, randomized comparative treatment trial is needed. If atropine penalization, with its high acceptability to patients and parents, is found to produce results comparable with those of occlusion in cases of mild-to-moderate amblyopia, as the current and previous smaller studies suggest, then reconsideration of the standard of care for such amblyopia cases is indicated.

Accommodation, Ocular↗
PubMed2004

[Extensive peripapillary myelinated nerve fibers, high ipsilateral myopia and refractory amblyopia].

INTRODUCTION: Extensive peripapillary myelinated nerve fibers can be associated with myopic anisometropia amblyopia. Despite aggressive occlusion of the good eye, visual results are often disappointing, probably because of structural anomalies of the macula, limiting visual potential. OBSERVATION: The authors report the case of a 5-year-old girl presenting extensive peripapillary myelinated nerve fibers associated with myopic anisometropia. Amblyopia did not respond to optical correction and continuous occlusion of the good eye for 9 weeks. DISCUSSION: Certain authors report obtaining good results with aggressive treatment of amblyopia associated with extensive peripapillary myelinated nerve fibers and myopic anisometropia. However, the majority of the few series published in the literature report that amblyopia related to this pathology is particularly refractory to treatment, as confirmed by the case study presented herein. CONCLUSION: Despite a certain number of cases with a good prognosis reported in associated peripapillary myelinated nerve fibers and ipsilateral myopia, we believe that its visual prognosis remains reserved and that patients and/or their families should be provided with appropriate information.

Amblyopia↗
PubMed2004

[Amblyopia and peri-ocular capillary hemangioma of infancy: screening and clinical course before and after surgery].

PURPOSE: The analysis of visual complications provoked by infantile periocular hemangiomas and the understanding of their evolution before and after surgery. MATERIAL: and methods: A retrospective study including 30 children (31 eyes) who were operated for a periocular hemangioma with a surgical technique with the aid of ultrasonic scalpel Cavitron. Ophthalmological evaluation before and after surgery included: appreciation of the palpebral occlusion, strabismus, ocular motility, objective refraction and amblyopia. RESULTS: Surgical operation was performed within an average age of 9.5 months. The excision of periocular hemangiomas was effective on the release of the visual axis and on the amblyopia: 51.7% (16 eyes) of palpebral occlusion before surgery against 6.4% (2 eyes) after surgery and 77.4% (24 eyes) of amblyopia before surgery against 38.7% (12 eyes) after surgery. The anisometropia decreased after surgery. The ocular motility and the strabismus also improved. CONCLUSION: Surgical excision of periocular hemangiomas with the aid of ultrasonic scalpel is an effective technique presenting few complications. This surgery can be suggested early in infancy. It has a very good result in the release of the visual axis and the astigmatism which aided the reeducation of the amblyopia.

Amblyopia↗
PubMed1998

Changes in conceptions of meaning, effects and treatment of amblyopia. A phenomenographic analysis of interview data from parents of amblyopic children.

The research reported is an experimental study on the effects of intensified education of parents of children with amblyopia on their understanding of the nature of the defect, its origins and treatment. Parents in the control group were exposed to the ordinary information provided at two departments of paediatric ophthalmology, whereas parents in the experimental group, attending the same clinics, were asked to read a booklet aiming at enhancing their understanding of amblyopia and its treatment. Experimental as well as control subjects were thereafter interviewed about their understanding of the meaning of amblyopia and amblyopia-related phenomena. Data were generated in single subject, semi-structured, in-depth interviews which were taped and transcribed in extenso. The interviews were analyzed according to the phenomenographic approach: i.e. the outcome is a description of the various conceptions that emerged in the interviews. In almost all cases the categories of meaning could be hierarchically ordered with regard to the level of understanding implied. Parallel to the interviews the subjects had also filled out a questionnaire assessing general and specific attitudes towards disease and treatment (the Health Belief Model, HBM). The results reveal a superior understanding among parents in the experimental group. The experimental group had also changed attitudes towards disease and treatment in a direction that would favour compliance, more than could be observed in the control group. The outcome is discussed in terms of the role of understanding for a compliant behaviour. It is also emphasised that health care personnel would profit from being aware of the nature of common misconceptions of diseases and their treatment, in the sense that they would be better prepared for entering instructional dialogues with patients or, as in this case, other persons responsible for the management of prescriptions provided.

Adult↗
PubMed1982

Hyperacuity and amblyopia.

The most frequent cause of visual loss in childhood is functional amblyopia, an abnormality of visual acuity usually associated with either anisometropia (unequal refractive errors) or strabismus (turned eye) during early development. The usual clinical investigation of the visual acuity of amblyopes involves discrimination of the high contrast letters of a Snellen chart; however, there are other aspects of acuity, for example, grating acuity (the high spatial frequency limit of vision) and Vernier acuity (the smaller perceptible misalignment). Because of the extreme precision of Vernier acuity compared with either grafting or Snellen acuity, it is considered to be a form of hyperacuity which requires very precise positional information. In an effort to understand the nature of the neural abnormalities which cause the reduced acuity of amblyopes, we have measured here the Vernier acuity of amblyopic observers using an extended Vernier grating stimulus, and compared these results with their Snellen acuity and grating acuity. The results showed that different acuity losses are associated wih anisometropic versus strabismic amblyopia. When scaled with respect to their grating acuity, anisometropic amblyopes, like normals, showed hyperacuity, even at high spatial frequencies, while strabismic amblyopes showed severe losses in Vernier acuity. Snellen letter acuity showed a similar deficit relative to grating acuity in strabismic but not in anisometropic amblyopes. Contrary to some previous theories which have considered that all forms of amblyopia share a common neural basis, these results strongly support the view that different neural losses are associated with amblyopias of different aetiologies.

Amblyopia↗
PubMed1998

Untreated essential infantile esotropia: factors affecting the development of amblyopia.

PURPOSE: A concomitant esotropia, presenting within the first 6 months of life, associated with a high incidence of dissociated vertical deviation, manifest latent nystagmus and asymmetric optokinetic nystagmus is termed essential infantile esotropia. Most studies concern patients diagnosed in infancy and treated throughout childhood. This paper addresses the factors that may influence the development of amblyopia in patients who remain untreated until visual adulthood. METHODS: During a 3 year period 113 patients aged 8 years or more with a history of esotropia occurring within the first 6 months of life were examined for the study. All patients underwent full ocular motility assessment and cycloplegic refraction, and only those with one or more signs of essential infantile esotropia were included. RESULTS: Of the 113 patients, 16 (14.3%) had a difference of 2 or more lines in the visual acuity of the two eyes and were diagnosed as having amblyopia. Anisometropia was present in 10 of the 16 (62.5%). The correlation between anisometropia and amblyopia was statistically significant (p = 0.0001). CONCLUSIONS: Amblyopia following early surgical intervention in essential infantile exotropia is well documented, but the risk is outweighed by the chance of obtaining some form of binocular vision. However, where access to ongoing therapy is not available, patients with essential infantile esotropia, free alternation and no anisometropia have a significant chance of retaining good visual acuity in both eyes if surgery is delayed until visual adulthood.

Adolescent↗
PubMed2001

[Supportive amblyopia treatment by means of computer games with background stimulation; a placebo controlled pilot study of 10 days].

BACKGROUND: Computer programmes for visual stimulation may give new impulses to the field of amblyopia treatment by offering an option to shift the apparative visual training into the domestic sphere. Regarding this aspect we report on a placebo controlled study on a newly developed vision training consisting of a background stimulation by a drifting sinusoidal grating combined with a foreground game aimed to maintain the attention. MATERIALS AND METHODS: Fourteen amblyopia patients aged from 6 to 13 years participated in the study. Seven were allocated to a placebo and seven to a treatment group. Both groups had to train at the computer for a period of 10 working days by two sessions of about 20 minutes daily. Whilst the placebo group played in front of a neutral background, the treatment group did this with a drifting sinusoidal grating in the background. RESULTS: The treatment condition resulted in a greater increase of visual acuity than the placebo condition. Near vision improved in the treatment group from 0.20 (SD +/- 4.51 steps) to 0.39 (SD +/- 3.06 steps), i.e. by 3.0 steps of visual acuity (SD +/- 1.8 steps), in the placebo group from 0.14 (SD +/- 6.02 steps) to 0.17 (SD +/- 5.85 steps), i.e. by 0.8 steps of visual acuity (SD +/- 1.6 steps). Far vision improved in the treatment group from 0.29 (SD +/- 2.57 steps) to 0.44 (SD +/- 3.16 steps), i.e. by 1.9 steps of visual acuity (SD +/- 1.3 steps), in the placebo group from 0.24 (SD +/- 5.20 steps) to 0.28 (SD +/- 5.51 steps), i.e. by 0.7 steps of visual acuity (SD +/- 1.1 steps). CONCLUSIONS: Stimulation with drifting sinusoidal gratings improves the visual acuity of amblyopic eyes in a specific way. The effect might be accounted for by a synergy of spatial and temporal frequency in form vs. motion channels. A preliminary hypothesis is discussed and will be the subject of ongoing research. The presented method has been developed for the treatment of "delayed" amblyopia in the elder child. It is aimed to support and complement occlusion therapy. However, the reported results obtained over 10 days should be estimated only within the context of evaluation. By no means should the results be interpreted as a renewed pledge for a short-term treatment of amblyopia.

Amblyopia↗
PubMed2002

[Congenital ptosis: amblyogenic refractive errors, amblyopia, manifest strabismus and stereopsis related to the types of ptosis. Data on 77 patients and review of the literature].

BACKGROUND: Former reports on amblyogenic refractive errors, amblyopia and binocular vision in congenital ptosis usually comprise all forms of ptosis without any differentiation. This study is an analysis of different kinds of ptosis. PATIENTS AND METHODS: 154 eyes (98 ptotic eyes) of 77 patients with congenital ptosis aged > or = 1 year (56 unilateral ptoses: 45 simple, 1 with rectus superior paresis, 7 with Marcus Gunn's syndrome, 2 congenital oculomotor palsies, 1 unilateral fibrosis syndrome; 21 bilateral ptoses: 10 simple, 2 with bilateral double elevator paresis, 7 blepharophimosis syndromes and 2 bilateral fibrosis syndromes) were investigated concerning visual acuity, refractive error (94 % in cycloplegy), strabismus and stereo acuity. As amblyogenic refractive errors were defined: astigmatism > or = ldpt, anisometropia > or = 1 dpt (spherical equivalent) and hyperopia > or = 3 dpt; amblyopia was defined as visual acuity less than 1.0 or a difference between both eyes of at least 0.2. RESULTS: Altogether were found: Hyperopia > or = 3 dpt in 28.6 % (n = 28); astigmatism > or = 1 dpt in 63.3 % (n = 62), anisometropia in 27.3 % (n = 21), amblyopia in 65.3 % (n = 64), strabismus in 29.9 % (n = 23) and stereopsis in 76.6 % (n = 59). In unilateral simple ptosis, astigmatism of the fellow eye was found in 26.8 % (n = 14). In unilateral ptosis, esotropia was 21.4 % (n = 12), in bilateral ptosis, exotropia 19 % (n = 4), as well as astigmatism > or = 3 dpt 26.2 % (n = 11). As was to be expected, ptosis groups with motility disorders were associated with higher rates of strabismus and amblyopia. The blepharophimosis syndrome could be differentiated by the typical lid anomalies. CONCLUSION: The subgroups of congenital ptosis differ in frequency of amblyogenic factors. In unilateral ptosis these are also frequent in the fellow eye.

Adolescent↗
PubMed2006

[Landolt C and snellen e acuity: differences in strabismus amblyopia?].

BACKGROUND: Assessment of visual acuity depends on the optotypes used for measurement. The ability to recognize different optotypes differs even if their critical details appear under the same visual angle. Since optotypes are evaluated on individuals with good visual acuity and without eye disorders, differences in the lower visual acuity range cannot be excluded. In this study, visual acuity measured with the Snellen E was compared to the Landolt C acuity. PATIENTS AND METHODS: 100 patients (age 8 - 90 years, median 60.5 years) with various eye disorders, among them 39 with amblyopia due to strabismus, and 13 healthy volunteers were tested. Charts with the Snellen E and the Landolt C (Precision Vision) which mimic the ETDRS charts were used to assess visual acuity. Three out of 5 optotypes per line had to be correctly identified, while wrong answers were monitored. In the group of patients, the eyes with the lower visual acuity, and the right eyes of the healthy subjects, were evaluated. RESULTS: Differences between Landolt C acuity (LR) and Snellen E acuity (SE) were small. The mean decimal values for LR and SE were 0.25 and 0.29 in the entire group and 0.14 and 0.16 for the eyes with strabismus amblyopia. The mean difference between LR and SE was 0.55 lines in the entire group and 0.55 lines for the eyes with strabismus amblyopia, with higher values of SE in both groups. The results of the other groups were similar with only small differences between LR and SE. CONCLUSION: Using the charts described, there was only a slight overestimation of visual acuity by the Snellen E compared to the Landolt C, even in strabismus amblyopia. Small differences in the lower visual acuity range have to be considered.

Adolescent↗