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PubMed1976

The tropical amblyopia syndrome (or tropical nutritional amblyopia) in the Mid-Western State of Nigeria.

One hundred and seven patients from the Mid-Western State of Nigeria with the tropical amblyopia syndrome are reported. Ninety-five patients (88.8%) had the amblyopia syndrome mainly; twelve patients (11.2%) had amblyopia and other manifestations of the tropical ataxic neuropathy. The young, aged 10-20 years, represented by sixty-six patients (61.8%), are predominantly affected by the uncomplicated syndrome. Thirteen patients (12.1%) showed muco-cutaneous evidence of avitaminosis. Fifty patients (46.7%) had temporal pallor of the optic discs, bilaterally, another fifty (46.7%) had normal discs, two (2.8%) showed pink discs. Generalized field constriction is the common field defect, though central or centro-caecal scotoma can occur. Red/green defect was present in seven patients. It is a disease of the poor or those living on a basic monotonous diet consisting mainly of cassava (mannihot) and its derivatives. It is a significant cause of defective vision in Mid-Western Nigeria.

Adolescent↗
PubMed1992

[Refractive error and amblyopia in children].

The refractive status of 3,099 children was analyzed. The result showed that the incidence and degree of hyperopia decreased gradually and those of myopia increased along with the growing up of children in ametropia. In binocular refractive amblyopia, high and medium hyperopia and myopia in severe and medium amblyopia were significantly more than those in mild amblyopia. In monocular refractive amblyopia, high and medium hyperopia and high myopia in the amblyopic eyes were more than those in the nonamblyopic eyes. The refractive status of binocular esotropic amblyopia had no significant difference in various ages and degrees of amblyopia. There was also no significant difference between the refractive status of the amblyopic and nonamblyopic eyes in monocular esotropic amblyopia. It was considered that refractive amblyopia was closely related to high ametropia and the deviation of the eye might be the main cause of strabismic amblyopia.

Adolescent↗
PubMed1977

Refraction as a basis for screening children for squint and amblyopia.

+2-00 to +2-75 dioptres of spherical hypermetropia in the more emmetropic of a pair of eyes is significantly associated with esotropia (P less than 0-001) and the presence of amblyopia (P less than 0-01). Anisometropia is not significantly associated with esotropia (P = 0-31) unless there is spherical hypermetropia of +2-00 dioptres or more in the more emmetropic eye (P less than 0-001). Hypermetropic anisometropia of +1-00 DS or +1-00 D.Cyl. is associated with the presence of amblyopia (P less than 0-001). In the absence of esotropia there is also a significant association between the amount of anisometropia and the initial depth of amblyopia (P less than 0-01). The additional presence of esotropia increases the depth of amblyopia further (P less than 0-05) but not the incidence of amblyopia (P greater than 0-30). The level of significance of the association of refractive errors with squint/amblyopia was itself significantly higher (P less than 0-01) than that between a family history of squint or "lazy eye" on the one hand and squint and/or amblyopia on the other hand. 72 +/- 3% of all cases of esotropia and/or amblyopia in this sample of children had a refractive error of +2-00 DS or more spherical hypermetropia in the more emmetropic eye, or +1-00 D. or more spherical or cylindrical anisometropia. Since there is a close association between the refraction and how, when, and whether a child presents with squint and/or amblyopia, it would seem reasonable to reconsider refraction as a basis for screening young children for visual defects.

Amblyopia↗
PubMed1992

Defective processing of motion-defined form in the fellow eye of patients with unilateral amblyopia.

The following three measurements were made on a group of 20 pediatric and 5 adult patients with unilateral amblyopia: (1) speed threshold for recognizing motion-defined dotted letters; (2) recognition acuity for isolated solid letters of 4% contrast; and (3) Snellen line acuity for high-contrast letters. Normal limits were established with a group of 30 pediatric and 10 adult control subjects. The main finding was that, in amblyopic children, a high percentage (83%, 15 of 18) of fellow eyes showed a degraded ability to recognize motion-defined letters, even though Snellen acuity and 4% letter acuity were normal for age. The fellow eyes of all nine patients with strabismic amblyopia showed this pattern of loss, as did four of six fellow eyes of patients with anisometropic amblyopia and two of three fellow eyes of patients with anisometropic plus strabismic amblyopia. Only two clinically unaffected eyes were normal for motion-defined letters. These eyes belonged to patients with anisometropic amblyopia. Eighteen of the 19 previously amblyopic eyes tested were abnormal for motion-defined letters even though Snellen acuity was within normal limits for 6 of these eyes. In adults, only one of five fellow eyes failed the motion-defined letter test. It was concluded that the degradation of form perception associated with amblyopia can be different for luminance-defined and motion-defined form and that defective processing of motion-defined form is common in the fellow eyes of children with unilateral amblyopia.

Adolescent↗
PubMed1992

Asymmetric inferior oblique overaction and its association with amblyopia in esotropia.

To evaluate the frequency of asymmetric inferior oblique overaction and its relationship to amblyopia, the authors reviewed the records of all patients who presented to Children's Hospital of Dallas with esotropia over a 2-year period. A total of 368 patients were identified and classified as infantile esotropia, acquired accommodative or partially accommodative esotropia, or acquired nonaccommodative esotropia. Two hundred forty-two patients (66%) had no amblyopia, of which 90% had symmetric inferior oblique activity. One hundred twenty-six patients (34%) had amblyopia; of these patients, 93 (74%) had symmetric inferior oblique action. Amblyopia was strongly associated with increased inferior oblique overaction in the amblyopic eye (P less than 0.001). This finding was consistent for all subgroups. The relative risk for having amblyopia as opposed to normal vision in an eye with increased inferior oblique activity relative to the contralateral eye was 5.6 to 8.6 depending on the eye. Amblyopia should be strongly suspected in patients with esotropia and asymmetric inferior oblique activity, specifically in the eye with more inferior oblique overaction.

Amblyopia↗
PubMed1991

[VECP (pattern threshold, amplitude, latency) in different light levels. A comparison between healthy eyes, organic and functional amblyopia eyes].

According to Bjerrum [5] and Ammann [2], light attenuation decreases visual acuity at different rates in normals, organic and functional amblyopes. In 27 normal subjects, 19 patients with central fixating squint amblyopia and 12 with organically poor vision, we determined the visually evoked cortical potential (VECP) threshold check size, P100 latency and P2 amplitude for reversing checkerboards of variable size at different levels of luminance. After light attenuation, we found a different rate of change for VECP threshold check size in normal subjects and patients with squint amblyopia, which lessened after the fovea was occluded. With suprathreshold checks, normal subjects and patients with squint amblyopia exhibited significantly smaller amplitude/latency changes after light attenuation than patients with organically poor vision. Only patients with squint amblyopia exhibiting a visual acuity of greater than 0.2 showed smaller VECP changes than normal subjects during light attenuation. According to these findings, the different rate of change in visual acuity after light attenuation in normal subjects and patients with squint amblyopia is locus specific [7] rather than luminance specific [12, 13]. We conclude that cortical disinhibition of the parafoveal retina [20] is responsible for the preservation of visual acuity in squint amblyopia during light attenuation.

Adolescent↗
PubMed1991

A study of amblyopia in 18-19 year old males.

During a vision screening of 6,556 National Service pre-enlistees aged 18-19 years at the Medical Classification Centre of Central Manpower Base, 48 subjects were found to have visual acuity of 6/12 or less in one or both eyes in the absence of ocular pathology. The prevalence of amblyopia in this population is 0.73%. Amblyopia was due to anisometropia in 24 cases (50%), strabismus in 9 cases (18.7%), high astigmatism (meridional) in 7 cases (14.5%) and other causes or a combination of factors in 8 cases (16.7%). Strabismic amblyopia is most commonly associated with esotropia. There is a positive association between the severity of amblyopia and the degree of strabismus in strabismic amblyopes. Meridional amblyopia tends to be less severe than most other types of amblyopia. The amblyopes were detected late (average 7-10 years of age) and orthoptic treatment of a small minority of them upon diagnosis was unsuccessful.

Adolescent↗
PubMed1991

Microtropia versus bifoveal fixation in anisometropic amblyopia.

Microtropia with identity is a unique condition in which amblyopes have parafoveal eccentric fixation in the amblyopic eye in either monocular or binocular viewing, plus a macular scotoma. The condition has previously been described in anisometropic amblyopia. The records of 55 consecutively presenting anisometropic amblyopes were scrutinised and the cases divided into microtropes or non-microtropes (bifoveal fixators). The features of the two groups were then compared to identify factors associated with microtropia and to determine whether microtropes or bifoveal patients responded better to amblyopia therapy. Results show that 45% of anisometropic amblyopes have microtropia rather than bifoveal fixation. There appears to be no association between the microtropic phenomenon and age, depth of amblyopia or amount of anisometropia. Bifoveal patients may respond better to amblyopia therapy although the difference between groups was not great. The sensitive period during which amblyopia may be treated is the same for each group.

Age Factors↗
PubMed1992

Amblyopia: etiology, detection, and treatment.

Amblyopia is a preventable cause of visual loss in children that may be permanent unless it is detected and treated early. It may be caused by strabismus, refractive errors, or cataracts. Primary strabismus may lead to loss of vision from amblyopia and the loss of binocularity. Secondary strabismus may be a sign of primary visual loss in one or both eyes. The most serious disorder that may present as secondary strabismus is retinoblastoma. It is imperative to detect retinoblastoma early because of its morbidity and mortality. Amblyopia is detected by assessing the visual acuity of each eye. Strabismus is detected by using the corneal light reflex test and the cover test. Focusing problems are detected by assessing the visual acuity and the red reflex. Cataracts and retinoblastoma may be detected by examining the red reflex of the eye. Treatment of amblyopia consists of correcting the amblyogenic factor with appropriate glasses and surgery. The preferred eye is patched with an adhesive patch to stimulate visual development in the amblyopic eye. The pediatrician plays a crucial role in the early detection of amblyopia, strabismus, and cataracts. The key to successful visual outcome is early recognition by the pediatrician, referral to the pediatric ophthalmologist, and prompt treatment.

Amblyopia↗
PubMedDate not supplied

The diagnosis of amblyopia in cross-fixation.

Customarily, it is taught that cross-fixation, in a patient with congenital esotropia, obviates the development of amblyopia. However, our clinical experience has shown significant amblyopia in 50% of cross-fixators. In our hands, the diagnosis of amblyopia is made based on the point at which alternation of fixation takes place. By this method, if there is equal visual acuity, alternation will occur at the midline with each eye. If amblyopia exists, the sound eye will continue to follow the target beyond midline, into abduction, before the poorer seeing eye picks up fixation. In order to test the reliability of this method, using Teller acuity cards as the standard, we compared estimates of objective and subjective vision in 25 consecutive patients with congenital esotropia and cross-fixation. Our findings suggest that there may be a significant prevalence of amblyopia in cross- fixating patients and that the point at which alternation of fixation occurs is a reliable means of detecting a difference in visual acuity between the two eyes.

Amblyopia↗
PubMed1992

[Measuring the threshold of stereopsis for 111 children with amblyopia].

The threshold of stereopsis was measured by static stereopter for 111 children with amblyopia aged from 4 to 13 years. They were divided into three groups: 38 cases ranging in age from 4 to 5 years, 43 cases 6 to 7 and 30 cases 8 to 13. Fifty six cases were unilateral and 55 bilateral amblyopia. The average threshold of stereopsis was 149.64 second angle for the 4-5 group, 66.69 for the 6-7 and 48.48 for the 8-13. The average threshold for unilateral amblyopia was 65.3, in which mild type was 38.6 and under moderate type was 88.84, whereas the average threshold for bilateral cases was 115.81, in which mild type was 44.09 and under moderate type was 175.44. The distribution of stereopsis for different age groups, the threshold of stereopsis influenced by different types of amblyopia and the comparison of amblyopia between bilateral and unilateral are also discussed.

Adolescent↗
PubMed1979

Is amblyopia a peripheral defect?

A class of retinal ganglion cells, the 'sustained' or 'X' cells in the area centralis of the retina, provides the physiological basis of high visual acuity. Our hypothesis, that amblyopia is a functional loss of X-cells due to inappropriate stimulation of the fovea by habitually blurred images during the critical period of development, has been supported by experiments on kittens reared with various types of surgically produced squint or with penalization. Amblyopia was associated with a loss of visual acuity of X-cells in the area centralis of the squinting eyes which had lost the ability to fix or of the penalized eyes, i.e. amblyopia occurred in the eyes which received habitually blurred images during the critical period of development. Thus amblyopia has a peripheral (retinal) cause. Regardless of whether or not the eye was amblyopic, a loss of binocularly driven cells in the visual cortex was a common feature in all uniocularly treated cases. When one eye was amblyopic the cortical cells tended to favour the non-amblyopic eye and the number of cells driven by the amblyopic eye was reduced. These central effects may play a role in suppressing unwanted images from the amblyopic eye while the fixing eye is in use. But the central effects do not cause amblyopia.

Amblyopia↗
PubMed1992

The spatial localization deficit in amblyopia.

There have now been numerous reports of a spatial localization deficit in amblyopia but none so far have tackled (1) the relationship between the contrast sensitivity and spatial localization deficits and (2) whether the spatial localization deficit is best described in units of visual angle or in terms of the underlying filter size. These issues are germane because they lie at the very heart of our understanding of the underlying deficit in amblyopia. To answer these questions we use spatially bandpass stimuli so that we can readily compare detection and localization for the same stimuli at each of a number of spatial scales. For some amblyopes (all strabismics and a minority of anisometropes) the contrast sensitivity defect neither underlies nor covaries with the spatial localization deficit. In the majority of anisometropic amblyopes, the contrast sensitivity loss is a complete description. The spatial localization deficit in amblyopia is of two independent kinds; positional inaccuracy and positional distortion. The positional inaccuracy deficit which can occur in varying degrees in both strabismic and anisometropic amblyopia, affects all spatial scales equally and therefore is best thought of in terms of a constant fraction of the underlying filter size in the space-frequency plane. The positional distortion deficit which can also occur to varying degrees in both strabismic and anisometropic forms can not be easily understood within this metric at least for strabismics.

Amblyopia↗
PubMed2026

Genome-Wide and Rare Variant Association Studies of Amblyopia in Admixed American and African Ancestry Groups.

OBJECTIVE: To identify genetic variants associated with amblyopia in African (AFR) and Admixed American (AMR) ancestry groups, expanding on previous studies conducted in European ancestry. DESIGN: Retrospective ancestry-stratified genome-wide association study (GWAS) and gene-level rare variant association study (RVAS). PARTICIPANTS: Participants in the All of Us Research Program from AFR and AMR ancestry groups who had whole-genome sequencing available. Cases and controls were distinguished based on the presence of International Classification of Diseases 9/10/SNOMED diagnosis codes for amblyopia in electronic health records. This yielded ancestry-stratified subsets of 269 cases and 71 585 controls of AMR ancestry and 366 cases and 79 460 controls of AFR ancestry. METHODS: Stratified logistic regression models were adjusted for age, biological sex, and the top 10 principal components of genomic ancestry. GWAS was limited to common variants (minor allele frequency &#x2265;1%), and RVAS was limited to rare variants with coding sequence-altering effects (minor allele frequency >1%, exonic only, excluding synonymous variants) aggregated at the gene level using the SKAT algorithm. Downstream analyses of the significant variants were performed using KEGG and GO pathway analysis and STRING database queries for protein-protein interactions and gene-gene interactions. MAIN OUTCOME MEASURES: Single-nucleotide polymorphisms were determined to have genome-wide significance if P < 5e-8 in the GWAS, and genes were determined to have significant association with amblyopia in the RVAS if P < 8.0 &#xd7; 10-4. RESULTS: In the AMR GWAS, 245 unique single-nucleotide polymorphisms mapping to 97 distinct loci were identified, notably within neurodevelopmental and axonal guidance genes, including ROBO1, SEMA4B, PTPRD, NRXN1, and CAMK2D. The AFR GWAS identified 11 significant variants corresponding to 6 loci mapping primarily to long noncoding RNAs and pseudogenes. The AMR RVAS identified 15 genes, including axonal transport genes (KIF1B and KIF7) and growth factor signaling genes (EGF, ERBIN, and AKAP17A). The AFR RVAS identified a single gene, DLG2, which encodes the postsynaptic protein PSD-93, which promotes the closure of the sensitive period of neuroplasticity for vision in early childhood. CONCLUSIONS: Genetic risk architectures for amblyopia differ across ancestries but fundamentally converge on neurodevelopmental signaling, cortical synapse assembly, and sensitive period plasticity rather than ocular structural dynamics. FINANCIAL DISCLOSURE(S): The authors have no proprietary or commercial interest in any materials discussed in this article.

Amblyopia↗
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↗
PubMed1992

Anisometropic amblyopia: is the patient ever too old to treat?

Amblyopia is an example of abnormal visual development that is clinically defined as a reduction of best corrected Snellen acuity to less than 6/9 (20/30) in one eye or a two-line difference between the two eyes, with no visible signs of eye disease. We describe a sequential management program for anisometropic amblyopia that consists of four steps: (1) the full refractive correction, (2) added lenses or prism when needed to improve alignment of the visual axes, (3) 2 to 5 h/day of direct occlusion, and (4) active vision therapy to develop monocular acuity and improve binocular visual function. We examined records of 19 patients over 6 years of age who had been treated using this sequential management philosophy. After 15.2 (+/- 7.7) weeks of treatment the Amblyopia Success Index (ASI) documented an average improvement in visual acuity of 92.1% +/- 8.1 with a range from a low of 75% by a 49-year-old patient to a maximum of 100% achieved by 42.1% of the patients (8 of 19). Patients who had completed therapy 1 or more years ago (N = 4) maintained their acuity improvement. From these results we conclude that following a sequential management plan for treatment of anisometropic amblyopia can yield substantial long-lasting improvement in visual acuity and binocular function for patients of any age.

Adolescent↗
PubMedDate not supplied

Unexpected good results after therapy for anisometropic amblyopia associated with unilateral peripapillary myelinated nerve fibers.

Unilateral extensive myelination of the peripapillary nerve fibers may be associated with anisometropic myopia, strabismus, and reduced vision. Despite aggressive occlusion of the normal eye, visual results are often disappointing, presumably due to associated structural abnormalities in the macula which limit visual potential. We report two cases, a 21-month-old child and a 23-month-old child with unilateral peripapillary myelination, ipsilateral high myopia, and dense amblyopia. Despite an abnormal macular reflex in each child, vision improved to 20/30 in one child and 20/50 in the other child after occlusion therapy. Visual results in these patients suggest that aggressive amblyopia therapy should be considered in patients with anisometropic amblyopia associated with extensive myelination continuous with the optic nerve. Not all patients with unilateral peripapillary myelinated nerve fibers, an abnormal macula, and myopia will have refractory amblyopia.

Amblyopia↗