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PubMed2005

Two-year follow-up of a 6-month randomized trial of atropine vs patching for treatment of moderate amblyopia in children.

OBJECTIVE: To compare patching and atropine sulfate as treatments for moderate amblyopia in children 18 months after completion of a 6-month randomized trial. METHODS: In a randomized, multicenter (47 sites) clinical trial, 419 children younger than 7 years with amblyopia (20/40 to 20/100 in the affected eye) were assigned to receive either patching or atropine eye drops for 6 months. Between 6 months and 2 years, treatment was at the discretion of the investigator. Main Outcome Measure Visual acuity in the amblyopic eye and sound eye after 2 years. RESULTS: At 2 years, visual acuity in the amblyopic eye improved from baseline a mean of 3.7 lines in the patching group and 3.6 lines in the atropine group. The difference in visual acuity between treatment groups was small: 0.01 logMAR (95% confidence interval, -0.02 to 0.04). In both treatment groups, the mean amblyopic eye acuity was approximately 20/32, 1.8 lines worse than the mean sound eye acuity, which was approximately 20/20. CONCLUSIONS: Atropine or patching for 6 months followed by best clinical care until 2 years produced similar improvement of moderate amblyopia in children between 3 and 7 years of age at enrollment. However, on average the amblyopic eye acuity was still approximately 2 lines worse than the sound eye.

Amblyopia↗
PubMed1984

Functional amblyopia associated with abnormalities of the optic nerve.

Seven patients with structural abnormalities of one or both of their optic nerves had decreased visual acuity partly due to functional amblyopia. They were treated with conventional amblyopia therapy and their visual acuities improved. Functional amblyopia can coexist either secondary to, or coincidentally with, structural optic nerve abnormalities.

Amblyopia↗
PubMed2006

Interventions for stimulus deprivation amblyopia.

BACKGROUND: Stimulus deprivation amblyopia (SDA) develops due to an obstruction to the clear passage of light, preventing clear formation of an image on the retina for example, cataract, ptosis (droopy eyelid). It is particularly severe and can be resistant to treatment and the visual prognosis is often poor. Stimulus deprivation amblyopia is rare and precise estimates of prevalence difficult to come by; it probably constitutes less than 3% of all cases of amblyopia. In developed countries most patients present under the age of one; in less developed parts of the world presentation is likely to be significantly later than this.The mainstay of treatment is patching of the better-seeing eye but regimes vary, treatment is difficult to execute and results are often disappointing. OBJECTIVES: The objectives of this review were to evaluate the effectiveness of occlusion treatment for SDA, determine the optimum treatment regime and factors that may affect outcome. SEARCH STRATEGY: We searched the Cochrane Central Register of Controlled Trials - CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) on The Cochrane Library (2006, Issue 1), MEDLINE (1996 to April 2006), EMBASE (1980 to April 2006) and LILACS (Latin American and Caribbean Literature on Health Sciences) (to November 2004). There were no date or language restrictions. SELECTION CRITERIA: We aimed to include randomised and quasi-randomised controlled trials of subjects with unilateral SDA defined as worse than 0.2 LogMAR or equivalent. There were no restrictions with respect to age, gender, ethnicity, co-morbidities, medication use, and the number of participants. DATA COLLECTION AND ANALYSIS: Two authors independently assessed study abstracts identified by the electronic searches. MAIN RESULTS: No trials were identified that met the inclusion criteria. AUTHORS' CONCLUSIONS: It is not possible to conclude how effective treatment for SDA is or which treatment regime produces the best results. There is a need for further study in this area.

Amblyopia↗
PubMed2005

Perceptual learning in adults with amblyopia: a reevaluation of critical periods in human vision.

Critical periods for experience-dependent plasticity are ubiquitous. The idea that experience-dependent plasticity is closely linked with the development of sensory function is still widely held; however, there also is growing evidence for plasticity in the adult nervous system. This article reviews the notion of a critical period for the treatment of amblyopia in light of recent experimental and clinical evidence for neural plasticity. Specifically, adults with amblyopia can improve their perceptual performance via extensive practice on a challenging visual task, and this improvement may transfer to improved visual acuity. Amblyopes achieve this improvement via the mechanisms that have been shown to explain perceptual learning in the normal visual system. It is hypothesized that these same mechanisms account for at least some of the improvement that occurs in the treatment of amblyopia.

Adult↗
PubMed1992

Binocular contrast summation and inhibition in amblyopia. The influence of the interocular difference on binocular contrast sensitivity.

The monocular contrast sensitivity loss in amblyopia is well documented. We investigated the influence of interocular sensitivity difference on binocular contrast sensitivity in amblyopia. Monocular and binocular contrast sensitivity functions of six amblyopes (three strabismic and three anisometropic) were measured. The monocular contrast sensitivity loss depended on the type of amblyope. Anisometropic amblyopes generally showed high frequency losses. Strabismic amblyopes showed losses at both low and high spatial frequencies. Binocular performance was assessed in terms of binocular ratios (binocular/non-amblyopic). A binocular ratio greater than 1 indicates binocular summation (binocular > monocular) while a ratio less than 1 shows binocular inhibition (binocular < monocular). In all subjects, the binocular ratio depended on the difference between the amblyopic and the non-amblyopic eye. Minimal interocular difference produced binocular summation, the magnitude of which decreased as the difference between the two eyes increased. Further increases in the monocular difference produced binocular inhibition. Anisometropic amblyopes showed a greater degree of binocular summation at low spatial frequencies compared to strabismic amblyopes. Both types of amblyopes showed binocular inhibition at high spatial frequencies. Clinical implications of binocular summation and inhibition in amblyopia are discussed.

Adolescent↗
PubMed1995

Effect of citicoline on visual acuity in amblyopia: preliminary results.

BACKGROUND: Citicoline has been used to improve consciousness levels in cerebral trauma and as a complement for levodopa in Parkinson's disease. It has also been shown that severe glaucomatous visual field deficits improve for at least 4 months with the use of citicoline. In this paper, preliminary results are presented of an open and a double-blind study on the effect of citicoline in amblyopia. METHODS: The open study was started in 1991. Fifty patients with amblyopia were treated with citicoline (1000 mg i.m. daily for 15 days). They were selected from an age group beyond the plastic period of the visual system. Occlusion or other types of anti-amblyopic treatment were never used at the same time as citicoline. A double-blind study was conducted on 10 more patients, randomly assigned to a treatment or placebo group and followed for 6 months. A statistical test for repeated measures was performed on all the results. RESULTS: A statistically significant improvement in visual acuity was found both for the amblyopic and the sound eye in 46 of the 50 patients (92%). The behaviour was different for normal and amblyopic eyes. The improvement remained stable for at least 4 months. These results have been substantiated by the double-blind study. No side effects were observed. CONCLUSION: Citicoline improves visual acuity, at least temporarily, in amblyopic patients beyond the plastic period of the visual system. Our results suggest that trials of citicoline as a medical treatment of amblyopia are warranted.

Adolescent↗
PubMed1990

Neural site of strabismic amblyopia in cats: spatial frequency deficit in primary cortical neurons.

The acuities of cells in the primary visual cortex of five tenotomized strabismic cats were measured. Previous behavioural studies have shown such animals to possess a severe amblyopia of approximately 1.5 octaves of spatial frequency, yet the acuities of both retinal ganglion and lateral geniculate X-cells are normal. The receptive fields of the cortical cells sampled were within 5 degrees of the area centralis projection. On average, the acuities of cortical cells driven by the amblyopic eye were nearly 1 octave less than those for the non-deviating eye. However, the best cell acuities for each eye were nearly the same. The relationship between ocular dominance and cell acuity was found to be different for the two eyes despite a symmetrical ocular dominance distribution. The acuity deficit for cells driven through the amblyopic eye was present at all depths along the electrode tracks. We conclude that in this model amblyopia, the initial spatial processing deficit lies in the visual cortex, and most probably in the cells of layer IV. Furthermore, the presence of a few cells driven by the amblyopic eye which can perform nearly as well as those from the fellow eye in processing high spatial frequencies gives new insight into the way in which strabismic and deprivation amblyopias differ.

Amblyopia↗
PubMed1982

Relationship between amblyopia, LGN cell "shrinkage" and cortical ocular dominance in cats.

Six cats were reared with surgically produced squint or atropinisation of one eye during the sensitive period of development. Five cats were reared without an ocular interference but in the same environment as the experimental cats. Four of these normally reared cats provided control data for perikaryal size. When the cats were 5-8 months old, the ocular dominance distribution of cells in area 17 of the visual cortex was determined, and measurements of visual acuity of cells in the LGN receiving inputs from the area centralis were carried out. Following the neurophysiological experiments, the perikaryal sizes of LGN cells receiving fibres from the area centralis of the left and right eye were measured from Nissl stained sections of the brain of each cat. Cats which showed greater amblyopia (loss of acuity) of LGN cells driven from the area centralis of the experimental eye, showed a greater degree of apparent "shrinkage" of Nissl stained LGN cells and greater proportion of cortical cells excited by the control eye than by the experimental eye. All experimental cats showed a loss of binocularly driven cells, regardless of whether their LGN cells were amblyopic or not, and whether they had "shrunk" or not. However, when LGN cell amblyopia was present, the degree of amblyopia and "shrinkage" of the LGN cells were correlated with the degree of loss of binocular cells also.

Amblyopia↗
PubMed1980

Functional amblyopia in kittens with unilateral exotropia. I. Electrophysiological assessment.

In two cats in which surgically induced, unilateral divergent strabismus had led to behaviourally determined amblyopia, a variety of electrophysiological parameters were determined in search of neuronal correlates of squint amblyopia. Tests that assess global neuronal excitability along the pathways from the two eyes to the visual cortex (areas 17 and 18) failed to reflect the functional inferiority of the squinting eye: retinographic responses and cortical evoked potentials elicited by Ganzfeld-stimulation and by stimulation of the optic nerves were identical for the two eyes. The ocular dominance distribution of neurons in area 17 showed the expected disruption of binocularity but failed to provide clear evidence for a functional inferiority of the squinting eye. At other levels of analysis, however, a clear difference between the two eyes was apparent: 1. Responses to optimally aligned light stimuli tended to be more sluggish and the under-representation of neurons with vertically oriented receptive fields was more pronounced in neurons driven from the deviated eye than in cells dominated by the normal one. 2. Interocular inhibition as assessed from electrically evoked potentials was found to be asymmetric; responses evoked from the amblyopic eye were suppressed more readily and over longer periods by conditioning shocks applied to the normal nerve than vice versa. 3. Numerous abnormalities reflecting the functional inferiority of the squinting eye became apparent in cortical potentials evoked by phase reversal of gratings of variable spatial frequency and contrast. A laminar analysis of these field potentials suggests impaired transmission along the intracortical pathways which relay activity to supragranular layers as a major cause for abnormal responses from the squinting eye. It is concluded that squint amblyopia is associated with a variety of neuronal changes at various levels of the visual levels of the visual system, the present data providing evidence for alterations at the cortical level.

Amblyopia↗
PubMed1988

Successful treatment of functional amblyopia associated with juvenile glaucoma.

Twelve patients with either unilateral or bilateral juvenile glaucoma underwent standard amblyopia management for the treatment of suspected functional amblyopia secondary to their glaucoma. Despite the presence of glaucomatous cupping or corneal changes, the amblyopia therapy was successful in ten patients.

Amblyopia↗
PubMed2002

[Some aspects of the current controversy about the treatment of amblyopia].

Occlusion has been used for centuries for treating amblyopia but in recent years an intensive debate about the treatment has arisen. The aim of this article is to summarize some of the new aspects of this discussion: on the one hand the effect of occlusion treatment during childhood is being questioned and on the other hand experimental approaches are being tested which are aimed at treating amblyopia in adults. Evidence from own experimental work is presented showing the influence of occlusion on the spatial localization of visual stimuli. A continuation of research on amblyopia and the effect of the therapy is urgently needed.

Adolescent↗
PubMed1998

[Model for cost-benefit relations of amblyopia screening].

BACKGROUND AND PURPOSE: In Germany, 750,000 children are born per year who should be screened for developmental visual defects in the age range 24-48 months. However, the established pediatric screening program is not sufficient to prevent amblyopia. The purpose of this study was to examine the cost-effectiveness of alternatives for amblyopia and microtropia screening. METHODS: Three options were compared: (1) an orthoptic screening carried out in the field, for instance in kindergartens, (2) an examiner-independent objective apparatus-based screening, and (3) a complete ophthalmological and strabismological examination carried out in a practice. The costs of screening, follow-up examinations and of the treatment were modelled for prevalences of 1% (microtropia) and 5% (amblyopia). The benefit due to treatment was calculated as the result of an avoided whole-person impairment of 3% and 1%. The income related, increased tax and health care payments were used to cover the costs. RESULTS AND CONCLUSIONS: In options (1) and (2) there were favorable cost-effective ratios. The practice-based option 3 was economically less promising. The higher the prevalence was, the higher the resulting cost-effectiveness.

Amblyopia↗
PubMed2004

Perceptual salience of global structures and the crowding effect in amblyopia.

BACKGROUND: The crowding effect refers to stronger deficits in linear acuity (e.g., letters in a line) than in single letter acuity in amblyopia. The current work investigated whether the salience of a global structure in which the target for identification is embedded influences the crowding effect in amblyopia. METHODS: Compound shapes were presented to the amblyopic and fellow eyes respectively of 12 anisometropic amblyopes. The compound stimuli were presented on either a blank or a cross background so that the salience of global structures were manipulated. Reaction times (RTs) and response error rates were recorded when subjects identified global or local shapes, respectively. RESULTS: RTs were shorter to global than local shapes for both the amblyopic and the fellow eyes. The global RT advantage was larger for the amblyopic than the fellow eye. Interestingly, when viewing the stimuli with the amblyopic eye, subjects made more errors to local targets when the compound stimuli were presented against the blank than the cross background. CONCLUSION: The results suggest that the salience of global structures of visual stimuli contributes to the crowding effect in amblyopia.

Adolescent↗
PubMed2004

Deficits of spatial localization in children with strabismic amblyopia.

BACKGROUND: Besides loss of visual acuity and binocularity, spatial localization deficits (comprising both increased spatial uncertainty and spatial distortions) are an important feature of strabismic amblyopia. Although they have been extensively investigated in adult amblyopes, there are still many open questions concerning their substrate and relationship to clinical parameters. Our aim was to develop a procedure for assessing vertical alignment, which enabled us to find out whether children with strabismic amblyopia had similar spatial localization deficits, and their relation to the children's clinical condition. METHODS: Vertical alignment was assessed in children by comparing the visual direction in space of three loci along the vertical meridian, separated by 5 deg of visual angle. We tested alignment in the amblyopic and dominant eyes of 32 strabismic and in both eyes of 35 control children from 4.5 to 10 years, together with a careful orthoptic examination. RESULTS: In the amblyopic eyes, increased uncertainty and systematic distortions outside the normal range occurred. Large angles of deviation and pathological fixation patterns were necessary, but not sufficient conditions for gross spatial deficits to occur. The fellow dominant eyes showed spatial localization similar to normal eyes. CONCLUSIONS: Children with strabismic amblyopia exhibited localization deficits and relationship to clinical data similar to those in adult amblyopes. These data are important for further investigations about the substrate, plasticity and the clinical relevance of perceptual distortions.

Amblyopia↗
PubMed2006

Unilateral retinitis pigmentosa with amblyopia in the fellow eye.

PURPOSE: The purpose was to report a case of unilateral retinitis pigmentosa with amblyopia in the other eye. METHODS: Eight years ago, a 36-year-old woman complained of peripheral visual field loss in her left eye when she covered her right eye. Complete ophthalmological examinations including fundus photography and fluorescein angiography, full-field electroretinography, dark adaptation, and microperimetry were performed. RESULTS: Best-corrected visual acuity of the patient was 0.2 with +2.5 diopters in her right eye and 0.3 with +1.5 diopters in her left eye. Fundus examination did not reveal any abnormalities in the right eye, but narrow retinal vessels, optic disc pallor, and peripheral retinal pigment clumping was found in the left eye. The full-field electroretinography was normal in the right eye, but rod response, cone response, and combined response were non-recordable, and 30-Hz response was very small in the left eye. Dark adaptation thresholds were normal in the right eye, but were dramatically elevated in the left eye. Microperimetry was normal in the right eye, but the visual field was reduced to a 2x5 degrees central field in the left eye. CONCLUSION: Unilateral retinitis pigmentosa with amblyopia in the other eye is a rare condition. The patient presented here had a case of unilateral retinitis pigmentosa with the other eye with ametropic amblyopia. It is necessary to perform functional and morphological ophthalmological examinations to confirm the diagnosis.

Adult↗
PubMed2000

Lea symbols: visual acuity assessment and detection of amblyopia.

OBJECTIVE: Lea symbols can be used for measuring visual acuity in childhood. Therefore, these symbols might be useful for early detection of amblyopia. We evaluated whether the visual acuity determined with Lea symbols (LS) corresponds to the visual acuity determined with the Landolt-C (LC). PATIENTS AND METHODS: In 55 strabismic amblyopic volunteers aged 5-59 years, the monocular visual acuity of both eyes was determined using LC and LS. For comparison, the right eye of 20 healthy volunteers was examined. Single optotypes (LC, LS) were used in 55 amblyopes and crowded optotypes (LC(17.2), LC(2.6), CLS) in 40 amblyopes. The luminance of the test charts was 180-200 cd/m(2), with a contrast >85%. The refraction of the subjects was corrected beforehand. RESULTS: In the 40 amblyopic eyes tested under each condition, LS exceeded CLS and LC by about 1 line (dB), LC(17.2) by 2 lines and LC(2.6) by 3 lines (mean values +/- SD: LS 0.62+/-1.8 dB, CLS 0.46+/-1.7 dB, LC 0.5+/-2. 0 dB, LC(17.2) 0.41+/-2.3 dB, LC(2.6) 0.29+/-2.3 dB). The non-amblyopic fellow eyes and healthy eyes showed smaller differences (fellow eyes LS 1.32+/-1.1 dB, CLS 1.17+/-1.1 dB, LC 1. 15+/-0.9 dB, LC(17.2) 1.05+/-0.9 dB, LC(2.6) 0.93+/-1.1 dB; healthy eyes LS 1.74+/-0.9 dB, CLS 1.58+/-0.8 dB, LC 1.48+/-0.6 dB, LC(17.2) 1.41+/-0.7 dB, LC(2.6) 1.32+/-1.1 dB). In the amblyopic eyes, the reduction of LC was more distinct than the reduction of LS. Fifty-two amblyopes had an amblyopia >1 dB of LC, LC(17.2) and LC(2. 6), while 50 had an interocular acuity difference >1 dB CLS. CONCLUSIONS: Using Lea symbols, a recognition acuity can be determined and amblyopia can reliably be detected. Due to their design, the Lea symbols are particularly suitable and recommendable for application in young children. However a slight systematic difference between LS and LC has to be considered.

Adolescent↗
PubMedDate not supplied

Multifocal VEP difference between early- and late-onset strabismus amblyopia.

PURPOSE: To measure and compare the multifocal visual evoked potentials (mfVEP) difference between early- and late-onset strabismus amblyopia. METHODS: Eleven patients with early- and 11 with late-onset strabismus amblyopia with similar range of visual acuity and 11 normal control subjects were recorded with mfVEP. RESULTS: There was no significant difference in latency or amplitude between amblyopic and fellow eyes for the early-onset amblyopic group, whereas in the late-onset amblyopic group, latencies were significantly prolonged and amplitudes were attenuated in the central region of visual field in the amblyopic eye. The responses in the central region of visual field in both amblyopic and fellow eyes of the early-onset amblyopic group were of longer latency and smaller amplitude than normal. In the late-onset group, the responses from amblyopic eye were of increased latency and decreased amplitude in the central visual field compared with normal, but either latency or amplitude from fellow eye did not differ from normal significantly. CONCLUSIONS: There is significant difference in the mfVEP characteristics of patients with early- and late-onset strabismus amblyopia.

Adolescent↗
PubMed1979

Myelinated retinal nerve fibers associated with ipsilateral myopia, amblyopia, and strabismus.

Four patients had extensive unilateral myelinated nerve fibers associated with ipsilateral myopia, amblyopia, and strabismus. Their profound visual impairment, exotropia, and the early age onset of symptoms indicated that the amblyopia may have been organically caused. Prognosis is poor for even partial correction but good results have been obtained with intense therapy that includes full correction of the refractive error in each eye and extraocular muscle surgery if cosmetically necessary. In patients with axial myopia, images of a similar size will be produced by placing a lens of the correct power at the spectacle plane. In younger patients, a contact lens should not be used to correct the refractive error because it creates an undesirable anisometropia. Younger patients who have parafoveal fixation and no strabismus respond best to amblyopia therapy.

Adolescent↗