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PubMedDate not supplied

Decreased activation of the lateral geniculate nucleus in a patient with anisometropic amblyopia demonstrated by functional magnetic resonance imaging.

Although postmortem morphological changes in the lateral geniculate nucleus (LGN) have been reported in human amblyopia, LGN function during monocular viewing by amblyopic eyes has not been documented in humans. We used functional magnetic resonance imaging (fMRI) to study monocular visual activation of the LGN in a patient with anisometropic amblyopia. Four normal subjects, a patient with optic neuritis and a patient with anisometropic amblyopia were studied with fMRI at 1.5 T during monocular checkerboard stimulation. Activated areas in the LGN and visual cortex were identified after data processing (motion correction and spatial normalization) with SPM99. In the 4 normal subjects, comparable activation of the LGN and visual cortex was obtained by stimulation of either the right or left eye. In the patient with unilateral optic neuritis, activation of the LGN and visual cortex was markedly decreased when the affected eye was stimulated. Similarly, decreased activation of the LGN as well as the visual cortex by the affected eye was demonstrated in the patient with anisometropic amblyopia. Our preliminary results suggest that activation of the LGN is diminished during monocular viewing by affected eyes in anisometropic amblyopia. fMRI appears to be a feasible method to study LGN activity in human amblyopia.

Adolescent↗
PubMed2006

Brief daily periods of unrestricted vision can prevent form-deprivation amblyopia.

PURPOSE: To characterize how the mechanisms that produce unilateral form-deprivation amblyopia integrate the effects of normal and abnormal vision over time, the effects of brief daily periods of unrestricted vision on the spatial vision losses produced by monocular form deprivation were investigated in infant monkeys. METHODS: Beginning at 3 weeks of age, unilateral form deprivation was initiated in 18 infant monkeys by securing a diffuser spectacle lens in front of one eye and a clear plano lens in front of the fellow eye. During the treatment period (18 weeks), three infants wore the diffusers continuously. For the other experimental infants, the diffusers were removed daily and replaced with clear, zero-powered lenses for 1 (n=5), 2 (n=6), or 4 (n=4) hours. Four infants reared with binocular zero-powered lenses and four normally reared monkeys provided control data. RESULTS: The degree of amblyopia varied significantly with the daily duration of unrestricted vision. Continuous form deprivation caused severe amblyopia. However, 1 hour of unrestricted vision reduced the degree of amblyopia by 65%, 2 hours reduced the deficits by 90%, and 4 hours preserved near-normal spatial contrast sensitivity. CONCLUSIONS: The severely amblyogenic effects of form deprivation in infant primates are substantially reduced by relatively short daily periods of unrestricted vision. The manner in which the mechanisms responsible for amblyopia integrate the effects of normal and abnormal vision over time promotes normal visual development and has important implications for the management of human infants with conditions that potentially cause amblyopia.

Amblyopia↗
PubMed2006

The VF-14 and psychological impact of amblyopia and strabismus.

PURPOSE: To assess the impact of amblyopia, strabismus and glasses on subjective visual and psychological function among amblyopes. METHODS: Questionnaires were administered to 120 teenagers with amblyopia (cases), with residual amblyopia after treatment, or with or without strabismus and 120 control subjects (controls) Cases underwent ophthalmic examination including cycloplegic refraction. Two questionnaires (visual function 14 [VF-14] and a newly designed eight-item questionnaire) were administered to assess the psychological impact score of general daily life, having a weaker eye, glasses wear, and current noticeable strabismus. Questionnaires were validated in 60 subjects in each group by a second administration of the questionnaire. The VF-14 scores, psychological impact scores, and clinical data were compared. RESULTS: The VF-14 and psychological impact scores were highly reproducible. The mean VF-14 score for the control group was 95.5 and for the cases was 78.9 (P < 0.0001), but the scores did not correlate with the severity of amblyopia. The psychological impact score in general daily life was sensitive in discriminating between mild (median score 31) and moderate to severe (median score 56) amblyopes (P < 0.02). The cases segregated into two clear groups; those who scored high (large detrimental psychological impact) on psychological impact, with subjectively noticeable manifest strabismus, and those who scored low (low detrimental psychological impact), without noticeable strabismus. The subjective experience of patching treatment differentiated the two groups best of all. CONCLUSIONS: Subjective visual and psychological functions are altered compared with normal subjects due to amblyopia, strabismus, and a previous unpleasant patching experience. The mean VF-14 score was similar to that previously published for patients with glaucoma. The study underlines that amblyopia and/or strabismus have an impact on teenagers' subjective visual function and well-being.

Activities of Daily Living↗
PubMedDate not supplied

Visual outcome after excimer laser refractive surgery in adult patients with amblyopia.

PURPOSE: To evaluate the visual and refractive outcome in adult patients wi th refractive and anisometropic amblyopia treated with photorefractive keratectomy. METHODS: An interventional non-comparative study was performed on 50 consecutive patients with amblyopia treated with photorefractive keratectomy. Sixty-eight eyes of 18 participants with bilateral refractive amblyopia and 32 participants with unilateral anisometropic amblyopia were studied. The photorefractive keratectomy was performed with MEL 70 G-Scan excimer laser. Follow-up was 1, 3, 6, and 12 months after the treatment. The mean outcome measures were uncorrected visual acuity (UCVA), best spectacle corrected visual acuity (BCVA), refraction, and corneal transparency. RESULTS: In 64.7% of eyes, the UCVA at 12 months after the treatment was better than or equal to their preoperative BCVA. A total of 82.4% of eyes improved their BCVA one or more lines. No eye lost lines of BCVA, 17.6% remained unvaried, 50% gained one line, 20.6 % gained two lines, and 11.8% gained three lines of BCVA. The number of lines gained correlated strongly with diopters of anisometropia between eyes (p<0.01). The mean sphere changed from -5.62+/-3.37 D to -0.47+/-1 D, mean cylinder varied from -2.36+/-1.57 to -0.18+/-0.41 D, and the spherical equivalent varied from -6.82+/-3.1 to -0.45+/-1.08 D. No clinically significant haze was observed. CONCLUSIONS: Excimer laser refractive surgery appears to be a safe and efficient procedure in the treatment of ametropic and anisometropic amblyopia in adults. Adult patients with anisometropic and refractive amblyopia could benefit from the refractive treatment with significant improvement of the visual acuity.

Adult↗
PubMed2006

[Strabismic amblyopia: a retrospective study on patients from a university hospital].

PURPOSE: To evaluate the influence of compliance with treatment, severity of amblyopia and age at the beginning of treatment in patients with strabismic amblyopia submitted to patching. METHODS: The data were selected from medical records of 569 patients seen at the Department of Ophthalmology, University of São Paulo during the period of 1983 to 2000. EXCLUSION CRITERIA: loss of follow-up, age over 12 years, presence of nystagmus and other ocular diseases. The patients were divided into four groups according to age and classified based on the type of strabismus, compliance with treatment and severity of amblyopia. Statistical analysis was performed using Fisher's test. RESULTS: 198 (34.8%) patients were enrolled in the study. There was no difference regarding compliance among the age groups. The best success rate was obtained when there was good compliance with the treatment, independent of the degree of amblyopia. But worse compliance was observed among the patients with more severe amblyopia, who were the majority of patients of the study, and who showed the worst success rate. The success rate was not related to the patients' age. CONCLUSION: The study showed that compliance with patching plays a fundamental role in therapeutic efficacy. Thus, age at the beginning of treatment alone did not influence the success rate since it was possible to obtain good compliance independent of age. In addition, worse results were associated with severe amblyopia and less compliance.

Age Factors↗
PubMedDate not supplied

The role of drug treatment in children with strabismus and amblyopia.

Strabismus, or misalignment of the eyes, is a common ophthalmic problem in childhood, affecting 2 to 5% of the preschool population. Amblyopia is an important cause of visual morbidity frequently associated with strabismus, and both conditions should be treated simultaneously. Pharmacological means for treating strabismus and amblyopia can be divided into 3 categories: paralytic agents (botulinum toxin) used directly on the extraocular muscles to affect eye movements; autonomic agents (atropine, miotics) used topically to manipulate the refractive status of the eye and thereby affect alignment, focus and amblyopia; and centrally acting agents, including levodopa and citicoline, which affect the central visual system abnormalities in amblyopia. Botulinum toxin, the paralytic agent that causes the clinical symptoms of botulism poisoning, can be injected in minute quantities to achieve controlled paralysis of the extraocular muscles. Although the role of botulinum toxin is established in adults with paralytic strabismus, its usefulness in the treatment of comitant childhood strabismus (primary esotropia and exotropia) is not universally accepted. Botulinum injections tend to be more effective with smaller degrees of strabismus, in patients with good binocular fusion, and in managing overcorrections or undercorrections after traditional muscle surgery. Inadvertent ptosis and paralysis of adjacent muscles, unpredictable responses and technical constraints of the injections limit its use in children. Miotic therapy, by altering the refractive state of the treated eye, offers an alternative to optical correction with bifocals in treating esotropia due to excessive accommodative convergence. It is also effective in treating residual esotropia following surgery. The ease of use of glasses restricts the wide application of miotics in these common strabismus syndromes. Atropine, an anticholinergic agent, paralyses the ability of the eye to focus or accommodate. In amblyopia therapy, atropine is used to blur vision in the non-amblyopic eye and offers a useful alternative to traditional occlusion therapy with patching, especially in older children who are not compliant with patching. The neurotransmitter precursor levodopa and the related compound citicoline have been demonstrated to improve vision in amblyopic eyes. The therapeutic role of these centrally acting agents in the clinical management of amblyopia remains unproven.

Amblyopia↗
PubMedDate not supplied

Treatment for amblyopia: results using occlusive contact lens.

PURPOSE: Amblyopia treatment occasionally is complicated by patch intolerance, resulting in a poor outcome. Therefore, a prospective study was designed to examine the efficacy and safety of using occlusive contact lenses in the treatment of amblyopia. METHODS: Twenty-five patients, aged 2.5 to 9.5 years, who were using an opaque hydrogel contact lens for the treatment of amblyopia, were followed prospectively. RESULTS: Overall, 92% of patients improved at least one line of visual acuity. Eight patients improved > or = 2 octaves and 12 other patients improved > or = 1 octave. In three patients, the change in visual acuity was < 1 octave. Complications were seen in nine patients: contact lens irritation in five; poor contact fit in three; and peeking around the lens in one. The recurrence rate was high. In 11 of 25 patients, amblyopia rapidly returned to a reduced level when the contact lens was discontinued. CONCLUSIONS: Occlusive contact lenses can be used in treating amblyopia in children. This treatment is ideal in patients who were patch-intolerant and failed with conventional treatment. Patients should have close follow up, however, to monitor any anterior segment complications from contact lens use and to identify the patients in whom amblyopia recurs.

Amblyopia↗
PubMed1997

[Macular light sensitivity and afferent pupillary function in children's amblyopia].

OBJECTIVE: To study the characteristics of macular light sensitivity (MLS) and relative afferent pupillary defect (RAPD) in anisometropic and ametropic amblyopia in school-aged children. METHODS: By using the static perimetry technique and swinging light test, we assessed MLS and RAPD in normal subjects, anisometropic and ametropic amblyopia in school-aged children. RESULTS: In comparison with the normal group, the MLS in both anisometropic and ametropic amblyopic eyes was significantly depressed. The MLS of the fellow eyes of the amblyopic eyes in anisometropic subjects was also depressed as compared with that of the normal group. The rate of RAPD was positive in 34.29% in the anisometropic amblyopic group. CONCLUSIONS: The static perimetry technique demonstrates a marked depression of MLS in all amblyopic eyes tested, suggesting a defect of visual X-channel. The pathogenesis of monocular amblyopia and binocular amblyopia is probably different, thus MLS examination can help assess prognosis. RAPD in anisometropic amblyopia may reflect a deficiency of peripheral visual system. The fellow eye of the anisometropic amblyopia eye may also be abnormal in terms of psychophysical standard.

Afferent Pathways↗
PubMed2001

Poor correlation between "fix-follow-maintain" monocular/binocular fixation pattern evaluation and presence of functional amblyopia.

PURPOSE: To assess the reliability of visual screening with fix- follow-maintain (FFM) method in early detection of amblyopia in children who are not able to cooperate in testing with Allen Figures or Snellen E-chart. METHODS: Followup records of 89 patients that were examined in our pediatric ophthalmology department between May 1996 and May 1999 were evaluated retrospectively. The visual acuities that were measured with FFM method at the first visit were compared with the visual acuity levels that were measured with the Snellen E-chart at later followup visits. Functional amblyopia was defined as a difference of 2 or more Snellen lines between the two eyes. RESULTS: Amblyopia was later definitively diagnosed on the E-chart in only 17 (32.6%) of the 52 eyes that were estimated to have a significantly lower visual acuity than the fellow eye with the FFM method. Sensitivity of the FFM method in diagnosing amblyopia was found to be 53.1% and the specificity was 38.5%. CONCLUSIONS: The use of the FFM monocular/binocular fixation pattern to determine visual acuity and the possible presence of amblyopia is so insensitive, and so unspecific, that its reliability is very low and the results of such testing are therefore virtually useless, if not medically hazardous. There is, therefore, a need to make more universally available more sophisticated tests of vision (preferential looking, VEP); where they are not available, further emphasis should be placed on Snellen equivalent vision testing as with Allen Cards, Tumbling E, HOTV Test, Lea Figures etc. so as to obtain an accurate direct visual acuity at as young an age as possible. Amblyopia treatment should not be initiated solely on the basis of FFM testing.

Amblyopia↗
PubMed2002

[Amblyopia in myopia in patients with strabismus and without strabismus].

PURPOSE: To determine factors, which have influence on presence of strabismus among myopic patients with amblyopia. MATERIAL AND METHODS: Material covers 21 myopic patients with amblyopia, aged 6-15. All children presented have a different amount of anisometropia, 12 of them had strabismus. Authors, compared the group of patients with amblyopia and strabismus (12) with the group of patients with pure anisometropic amblyopia (9), according to the following criteria: age of presentation, best corrected visual acuity, mean refraction error of amblyopic eye, mean amount of anisometropia, percentage of patients with central fixation and binocular vision. RESULTS: Patients with strabismus presented oneself earlier than patients without squint. Best corrected visual acuity was better in patients without strabismus. Refraction error in both groups has similar value. Amount of anisometropia was slightly smaller in the group with squint. Central fixation and binocular vision were better preserved among patients without strabismus. Authors didn't find the following correlations too: correlation between amount of anisometropia and amount of amblyopia in both groups, correlation between amount of anisometropia and the amount of the deviation of squinting eye, correlation between depth of amblyopia and the amount of deviation of the squinting eye. CONCLUSION: It seems, that primary factor leading to presence of strabismus among patients with anisometropic myopia, is motor dysfunction of extraocular muscles.

Adolescent↗
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↗
PubMed1985

Amblyopia: a multidisciplinary approach. Proctor lecture.

Clinically different forms of amblyopia share as common denominators an inability to form well-defined and focused images in one or both eyes and, in the case of unilateral amblyopia, unequal visual input to the brain. This suggests two amblyopiogenic mechanisms which are effective, individually or in unison, in the various forms of amblyopia. The first is lack of adequate visual stimulation during infancy, causing visual deprivation. The second mechanism is based on abnormal binocular interaction. The clinical evidence and data from the animal laboratory will be reviewed in support of this dual etiological concept of amblyopia. An etiological classification of amblyopia suggested in 1972 on hypothetical grounds can be upheld on the basis of information that has accumulated since that time. Amblyopia is not a static condition but has a strong dynamic component since its severity can be modified by the type of stimulation received by the sound eye. Special emphases is placed in this lecture on this unique feature which is based on binocular interaction and is similar to the inhibition of afferent visual stimulation during suppression.

Amblyopia↗
PubMed1994

[An investigation of 4,125 cases of Kazak childhood strabismus and amblyopia].

An investigation was made on 4,125 Kazak pupils (aged from 4 to 14 years) with strabismus and amblyopia in 9 schools of 5 countries. Among the subjects examined, 48 cases (1.1%) were strabismus including 32 (66.67%) external and 16 (33.33%) internal strabismus; 15 cases (31.25%) suffered from both strabismus and amblyopia and 33 (68.75%) were strabismus but had normal visual acuity; 139 cases (209 eyes) were amblyopia (morbidity rate: 3.37%) including 70 binocular and 69 monocular amblyopia, 73 males and 66 females. Out of the 209 amblyopia eyes, 84 (40.19%) were slight, 104 (49.76%) medium and 21 (10.05%) serious. Ametropia was also found to be in the majority in Kazak childhood amblyope. Only 106 of 209 eyes were simple farsighted. To prevent the occurrence of amblyopia the writer suggests that efforts of finding and correcting ametropia at early stage should be made.

Adolescent↗
PubMed1994

Prevalence of amblyopia among schoolboys in Abha city, Asir Region, Saudi Arabia.

The aim of this study is to estimate the prevalence of amblyopia among schoolboys in Abha City and to examine its relations with anisometropia and strabismus. A total of 971 male school children were selected randomly from the elementary schools for male in the city. Using the criterion of a visual acuity of 6/9 or worse, with no obvious structural disease of the eye, to define amblyopia, 18 cases have been found to have the condition, with a prevalence of 1.85%. Those cases consisted of 7(47%) with anisometropic amblyopia and strabismus, and 2(13%) with deprivation amblyopia. Amblyopia showed a prevalence equal to 27% and 31% among children with anisometropia and those with strabismus respectively. An effective screening program for early detection of amblyopia through the well baby clinics is recommended.

Amblyopia↗
PubMedDate not supplied

Amblyopia: etiology, diagnosis, and treatment. American Academy of Ophthalmology.

1. Sometimes called "lazy eye," amblyopia is poor vision in an eye that did not develop normal sight during early childhood. Amblyopia is common, affecting approximately 2 or 3 out of every 100 people. The best time to correct amblyopia is during infancy or early childhood. 2. Amblyopia has three major causes: strabismus (misaligned eyes), unequal focus (refractive error), and cloudiness in the normally clear eye tissues. 3. To correct amblyopia, a child must be made to use the weak eye. This is usually done by patching or covering the strong eye. Amblyopia cannot be cured by treating the cause alone; the weaker eye must be made stronger in order to see normally.

Amblyopia↗
PubMedDate not supplied

Amblyopia in congenital ptosis.

This study evaluates the association between congenital ptosis and amblyopia. Amblyopia was detected in 7 of 36 (19%) patients with congenital ptosis. Two patients (6%) with amblyopia had no contributing factors other than the presence of congenital ptosis. A statistically significant correlation between severe nonocclusive ptosis (greater than or equal to 4 mm) and the development of amblyopia was identified. No new cases of amblyopia developed after surgical repair of the ptosis, suggesting early surgery for severe nonocclusive congenital ptosis may decrease the incidence of amblyopia.

Adolescent↗