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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↗

PubMed1991

Factors associated with delay in diagnosis of childhood amblyopia.

The prevention of permanent visual impairment from amblyopia is an important goal of pediatric vision screening. Unfortunately, many cases of amblyopia are not diagnosed until the child is too old to benefit maximally from treatment. A review of patient records from the practice of a private pediatric ophthalmologist confirmed that late detection is a frequent occurrence among children with amblyopia who have had good access to health care. A case-control study was then used to identify factors associated with delayed diagnosis, in which children with an adverse outcome (diagnosed at or after 5 years of age) were compared with those with an optimal outcome (diagnosed before 5 years of age). The chart review identified 161 children with amblyopia who participated in this study; 75 had late diagnoses (case patients) and 86 served as control patients. Children with early diagnoses more often had the following characteristics: a positive family history of strabismus, greater degrees of strabismus (when strabismus was present), higher maternal educational level, greater parental suspicion that an eye problem existed, and an increased chance that the parents requested the eye examination that led to the diagnosis. The parents of children with late diagnoses expressed less concern over the seriousness of amblyopia but were more likely to report that their children had suffered adverse consequences of amblyopia. When diagnosed early, amblyopia was more often detected by the child's primary health care provider. Physicians of the children with early diagnoses more often reported compliance with both the American Academy of Pediatrics guidelines for vision screening in infancy and referral for vision problems.(ABSTRACT TRUNCATED AT 250 WORDS)

Amblyopia↗

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↗

PubMed1990

Risk factors in amblyopia.

Any intervention to prevent serious amblyopia is based on the knowledge about normal versus subnormal visual development. Our ability to predict with high degree of certainty which children will develop amblyopia will be dependent on the characteristics of various risk factors for initiating the development of squint or amblyopia. We have used longitudinal studies of population based cohorts of young children to define some of these risk factors such as refractive errors. Three hundred and ten children with an astigmatism greater than or equal to 1.0 D at one year of age were refracted yearly between the age one and four years. Astigmatism and anisometropia were found to be highly variable during infancy and early childhood. Longitudinal follow-up seems to be needed to separate the normal from the abnormal refraction development, which initiates the development of the amblyopia. Children with constant or increasing astigmatism or anisometropia between one and four years were 'at risk'. In parallel we have studied important factors for successful treatment of amblyopia. Based on these findings we conclude that a population screening at four years of age seems to be advantageous in Sweden in order detect and successfully treat most cases of amblyopia.

Age Factors↗

PubMed1990

A longitudinal study of a population based sample of astigmatic children. I. Refraction and amblyopia.

The refraction changes in 310 children with astigmatism greater than or equal to 1.0 D in at least one eye at one year of age were followed during a period of 3 years. At the age 4 years amblyopia was found in 23 children (7%). The refraction data of these children were compared to the rest of the sample. We found that an increasing astigmatism during the test period was associated with an increased risk to develop amblyopia. The majority of children (n = 280) showed a decrease of their astigmatism, whereas all cases with a marked amblyopia (V.A. less than 0.5) or binocular amblyopia, except one, had an increasing or unchanged astigmatism during the age period 1 to 4 years. Strabismus and oblique astigmatism at any time during the test period was also strongly related to amblyopia. The incidence of strabismus (1%) was unexpectedly low. The study also showed that independent of age there was no simple relationship between amblyopia and refraction errors measured at a single test session. The main conclusion of this study is that failure of emmetropization may play an important role in visual development.

Amblyopia↗

PubMed1991

Anisometropic and strabismic amblyopia in the age group 2 years and above: a prospective study of the results of treatment.

Forty-four children aged 2-9 years with strabismic and anisometropic amblyopia were prospectively followed up during amblyopia treatment. The efficacy of optimised treatment in terms of number of cured children, time to achieve cure, and rate of initial improvement of visual acuity was evaluated in relation to age at start of treatment, type and initial degree of amblyopia, and adherence to treatment regimen. Compliance with treatment was the most critical factor predicting a successful outcome. Among the compliant children 35 out of 36 were cured (visual acuity difference between amblyopic and non-amblyopic eyes not more than one line) within five months regardless of age, treatment regimen, and type or initial degree of amblyopia as compared with none in the group with low compliance. Most of these compliant children were cured within three months, with shorter treatment times on average for the younger children. The initial improvement of visual acuity was also faster at 2 years than at 4 years of age. Anisometropes with moderate amblyopia at the start of treatment were over-represented in the group with low compliance. We conclude that early diagnosis of strabismus in combination with general population screening at the age of 4 to detect amblyopia caused by anisometropia or microstrabismus seems to be efficacious for the cure of most cases. The major factor in treatment failure was found to be inadequate adherence to the treatment regimen.

Age Factors↗

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↗

PubMed1990

[Treatment of amblyopia].

Animal experiments have explored the structural and functional alterations of the afferent visual pathways in amblyopia and have emphasized the extraordinary sensitivity of the immature visual system to abnormal visual stimulation. The practical consequences of these experiments are obvious: early diagnosis of amblyopia and energetic occlusion therapy as early in life as possible. At the same time, measures must be taken to prevent visual deprivation amblyopia in the occluded eye. After successful treatment, alternating penalization with two pairs of spectacles is recommended. Pleoptics involves an enormous commitment in terms of time, personnel and costs. In view of the fact that the superiority of this treatment over occlusion therapy has yet to be proven, the current value of pleoptics appears dubious. Moreover, overtreated patients may end up with intractable diplopia. Diverging opinions exist with regard to the use of penalization as a primary treatment of amblyopia. We employ it only in special cases as an alternative to occlusion therapy. Visual deprivation in infancy caused by opacities of the ocular media, especially when they occur unilaterally, must be eliminated, and deprivation amblyopia must be treated without delay to regain useful vision. Brief periods of bilateral occlusion are recommended to avoid the highly amblyopiogenic imbalance between binocular afferent visual input. Future developments will hopefully include new objective methods to diagnose amblyopia in preverbal children and infants. The application of positron emission tomography is perhaps the first step in the direction of searching for new approaches to this problem.(ABSTRACT TRUNCATED AT 250 WORDS)

Amblyopia↗

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↗

PubMed1990

[The prevalence of refractive, anisometropic amblyopia in adults without strabismus and with contact lens correction].

The paper presents results after examination of 1260 adults (2547 eyes), aged from 18 to 55 years, for the period from 1982 to 1988. The examination was carried out in order to reveal the incidence of refractive, anisometropic amblyopia without strabismus in persons using glasses (a control group) and contact lenses as well as to determine a degree of spheric, astigmatic refraction in development of amblyopia on the background of contact lenses. It was found that amblyopia on the background of contact correction, as compared with glass correction, develops rarer making up 22.03% of them low degree of amblyopia is recorded in 51,16%, moderate--in 35,65% high--in 13,19% to the total number of amblyopic eyes examined. Direct relationship between the number of amblyopic eyes and degree of astigmatism and anisometropia is revealed. Detection of amblyopia in adults without strabismus with subsequent contact correction and treatment is considered to be necessary for medical and labour rehabilitation of such patients.

Adolescent↗

PubMed1990

[Case finding of amblyopia in young children using the TNO-depth-vision-test].

To evaluate the policy in amblyopia detection by pre-school health care workers we studied the prevalence of amblyopia that had not previously been detected among 1975 children at the ages of 4 years 6 months to 5 years 10 months. Seventy-eight (3.9%) of the children had insufficient stereo-acuity, though no form of ocular abnormality had been noted in the past. Twenty-one (1%) of the children had a previously undetected amblyopia. After 1 1/2 years 74% of the children with amblyopia had a visual acuity of 0.9 or more, while most of the children--at the time of referral--were 4 1/2 years or older. Amblyopia can be identified earlier by (a) a proper transfer of information from pre-school health care workers to the school doctor; (b) taking into consideration low vision if assessment of vision was not successful in the first examination, and (c) performing at least the TNO-stereotest when in doubt.

Amblyopia↗