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PubMedDate not supplied

[Visual evoked potentials in patients with refraction amblyopia in the presence of high myopia].

The informative value of a method for assessing the degree of amblyopia, developed by the author, was assessed in examinations of 16 children (29 eyes) with ametropic amblyopia caused by high myopia and 41 healthy controls. The method consists in recording the pattern-reversal visual evoked potentials (VEP) evoked by 4 patterns of different checksize and contrast. A relationship has been revealed between the VEP types detected by the proposed method and the degree of amblyopia (degree of vision acuity loss). The author came to a conclusion that in ametropic amblyopia, similarly as in stimulus deprivation amblyopia, changes of VEP develop that reflect the deterioration of contrast sensitivity function in low spatial frequencies. The developed VEP method with the modifications described in this paper may be useful in the diagnosis and objective evaluation of the degree of amblyopia.

Adolescent↗
PubMed1997

[Binocular functions in amblyopia and strabismus].

Regarding the changing trends in the concept, definition, etiological classification, and criteria for diagnosis of amblyopia, we reviewed a total of 4,693 cases of amblyopia seen during the past 37 years. The amblyopia was divided into four types: strabismic, anisometropic, ametropic, and form vision deprivative. There was a definite trend for the incidence to decrease and for the diagnosis to be made during earlier age in recent years. Although favorable recovery of visual acuity is obtained after treatment of amblyopia and strabismus, there are difficulties in obtaining good binocular functions in early-onset amblyopia and strabismus. This feature was evaluated in regard to motion perception asymmetry (MPA) and binocular depth from motion (DFM). Many cases of early-onset amblyopia and strabismus showed no disparity stereopsis, or position stereopsis, in spite of the presence of DFM. The MPA appeared to be closely related to early-onset esotropia regardless of age, while it disappeared and motion perception became symmetric 4 to 5 months after birth in normal infants. The DFM seemed to play an important role in maintaining good motor alignment for several years after surgery. I developed a checkerboard pattern stimulator in 1978. This method proved to be useful in developing binocular functions and motor alignment by applying simultaneous bifoveolar stimulation and anti-suppression. Extensive exposure to the stimulation was essential for therapeutic success.

Adolescent↗
PubMed1998

Neuronal correlates of amblyopia in the visual cortex of macaque monkeys with experimental strabismus and anisometropia.

Amblyopia is a developmental disorder of pattern vision. After surgical creation of esotropic strabismus in the first weeks of life or after wearing -10 diopter contact lenses in one eye to simulate anisometropia during the first months of life, macaques often develop amblyopia. We studied the response properties of visual cortex neurons in six amblyopic macaques; three monkeys were anisometropic, and three were strabismic. In all monkeys, cortical binocularity was reduced. In anisometropes, the amblyopic eye influenced a relatively small proportion of cortical neurons; in strabismics, the influence of the two eyes was more nearly equal. The severity of amblyopia was related to the relative strength of the input of the amblyopic eye to the cortex only for the more seriously affected amblyopes. Measurements of the spatial frequency tuning and contrast sensitivity of cortical neurons showed few differences between the eyes for the three less severe amblyopes (two strabismic and one anisometropic). In the three more severely affected animals (one strabismic and two anisometropic), the optimal spatial frequency and spatial resolution of cortical neurons driven by the amblyopic eye were substantially and significantly lower than for neurons driven by the nonamblyopic eye. There were no reliable differences in neuronal contrast sensitivity between the eyes. A sample of neurons recorded from cortex representing the peripheral visual field showed no interocular differences, suggesting that the effects of amblyopia were more pronounced in portions of the cortex subserving foveal vision. Qualitatively, abnormalities in both the eye dominance and spatial properties of visual cortex neurons were related on a case-by-case basis to the depth of amblyopia. Quantitative analysis suggests, however, that these abnormalities alone do not explain the full range of visual deficits in amblyopia. Studies of extrastriate cortical areas may uncover further abnormalities that explain these deficits.

Amblyopia↗
PubMedDate not supplied

Strabismic amblyopia. Part 1. Psychophysics.

This is a two-part survey of current literature concerning strabismic amblyopia. The aim of this review is to bring the optometric practitioner up to date on the status of scientific research into strabismic amblyopia. Part 1 in this series discusses research into strabismic amblyopia from the viewpoint of psychophysical experiments that investigate both spatial and temporal behavioural deficits accompanying strabismic amblyopia. These include deficits in contrast sensitivity, spatial localisation, fixation, ocular motility, accommodation, crowding, attention, motion perception and temporal processing. Part 2 will evaluate neural processing in regard to strabismic amblyopia. It will discuss current understanding of aspects of central processing of visual information and theories regarding neural sites and mechanisms involved in amblyopia.

Journal Article↗
PubMedDate not supplied

Strabismic amblyopia. Part 2. Neural processing.

This is the second of a two-part survey of current literature concerning strabismic amblyopia. The aim of this review is to bring the optometric community up to date on the status of scientific research into strabismic amblyopia. Part 1 in this series discussed research into strabismic amblyopia from the viewpoint of psychophysical experiments, which investigate both spatial and temporal behavioural deficits accompanying strabismic amblyopia. These include deficits in contrast sensitivity, spatial localisation, fixation, ocular motility, accommodation, crowding, attention, motion perception and temporal processing. Part 2 concerns neural processing in regards to strabismic amblyopia. It discusses current understanding of more fundamental aspects of central processing of visual information and in particular current theories regarding neural sites and mechanisms involved in amblyopia.

Journal Article↗
PubMed2003

Impact of patching and atropine treatment on the child and family in the amblyopia treatment study.

OBJECTIVE: To assess the psychosocial impact on the child and family of patching and atropine as treatments for moderate amblyopia in children younger than 7 years. METHODS: In a randomized, controlled clinical trial, 419 children younger than 7 years with amblyopic eye visual acuity in the range of 20/40 to 20/100 were assigned to receive treatment with either patching or atropine at 47 clinical sites. After 5 weeks of treatment, a parental quality-of-life questionnaire was completed for 364 (87%) of the 419 patients. Main Outcome Measure Overall and subscale scores on the Amblyopia Treatment Index. RESULTS: High internal validity and reliability were demonstrated for the Amblyopia Treatment Index questionnaire. The overall Amblyopia Treatment Index scores and the 3 subscale scores were consistently higher (worse) in the patching group compared with the atropine-treated group (overall mean, 2.52 vs 2.02, P<.001; adverse effects of treatment: mean, 2.35 vs 2.11, P =.002; difficulty with compliance: mean, 2.46 vs 1.99, P<.001; and social stigma: mean, 3.09 vs 1.84, P<.001, respectively). CONCLUSION: Although the Amblyopia Treatment Index questionnaire results indicated that both atropine and patching treatments were well tolerated by the child and family, atropine received more favorable scores overall and on all 3 questionnaire subscales.

Adult↗
PubMed2003

Axial length-disc area ratio in esotropic amblyopia.

BACKGROUND: Hyperopia is a risk factor for esotropia and amblyopia. A previous study indicated that disc areas (DAs) are reduced in patients with amblyopia. OBJECTIVE: To determine if there is a difference in the relative size of the optic disc in hyperopic eyes without strabismus or amblyopia compared with esotropic and amblyopic eyes, the relationship of axial length (AXL) to DA in subjects with hyperopia was evaluated. METHODS: Eight hundred fifty records from my private practice, which included AXL measurements and optic disc photographs or digital images, were analyzed to locate 122 subjects with bilateral refractive errors greater than +2.00 diopters. Disc areas were measured using objective techniques. Axial lengths were determined by ultrasonographic biometry. A ratio, AXL/DA, was derived by dividing the AXL in millimeters by the DA in square millimeters. RESULTS: The mean (SD) AXL/DA for the group with hyperopia was 9.48 (2.70) mm and 12.30 (3.45) mm for the group with hyperopic strabismus (P =.01). The mean (SD) AXL/DA was 15.24 (4.61) mm in the amblyopic eyes and 13.61 (3.67) mm for the nonamblyopic fellow eye (P =.02). CONCLUSION: The optic discs of eyes with hyperopic strabismus with and without amblyopia were disproportionately and markedly reduced when compared with hyperopic eyes without amblyopia or esotropia.

Adult↗
PubMed1981

10-Diopter fixation test for amblyopia.

Fixation-preference testing has been useful in detecting amblyopia in children unable to give reliable visual acuities, except for children with small-angle tropias and those without manifest deviations. This study introduces a method of fixation testing that includes all children, regardless of the presence or size of the deviation. By placing a 10-diopter vertical prism over one eye, we induce a vertical deviation. Once the eyes are dissociated, fixation preference is evaluated and used to predict the presence of amblyopia. We prospectively studied fixation patterns in 98 children with either small-angle tropia or essentially straight eyes. All children with amblyopia of two lines or more showed abnormal fixation patterns, and those without amblyopia showed normal patterns. We were able to obtain fixation patterns on all children studied, including 13 infants less than 24 months of age. This test proved to be a reliable, objective method for detecting amblyopia in children with straight eyes or in children with microstrabismus of almost any age.

Adolescent↗
PubMed1984

Amblyopia and congenital esotropia. Visually evoked potential measurements.

Amblyopia in patients with congenital esotropia was studied using visually evoked cortical potentials. In only four of 31 patients with esotropia and no abducting nystagmus was amblyopia detected before surgery. Postoperatively, 19 of these patients had amblyopia. In contrast, nine of the 11 patients with esotropia and nystagmus exhibited amblyopia before surgery. We conclude that amblyopia occurs infrequently in patients with congenital esotropia and no nystagmus until surgery reduces the angle of deviation and breaks down the cross-fixation reflex.

Amblyopia↗
PubMed1993

Leber's hereditary optic neuropathy masquerading as tobacco-alcohol amblyopia.

OBJECTIVE: To determine the frequency of known primary mitochondrial DNA (mtDNA) mutations for Leber's hereditary optic neuropathy (LHON) in patients previously diagnosed as having tobacco-alcohol amblyopia. DESIGN: A case series of 12 patients with tobacco-alcohol amblyopia. Follow-up ranged from 2 months to 15 years. SETTING: Tertiary care. PATIENTS: Twelve patients diagnosed as having tobacco-alcohol amblyopia, based on the classic clinical presentation, were tested for all the known primary mtDNA mutations associated with LHON. All patients had a history of heavy alcohol or tobacco use or both. Twelve other patients who fit inclusion criteria were unable to be contacted or refused to participate in the study. MAIN OUTCOME MEASURES: Presence of a known primary mutation for LHON at nucleotide positions 11778, 3460, 15257, or 14484 of mtDNA. RESULTS: Two (17%) of 12 patients previously diagnosed as having tobacco-alcohol amblyopia tested positive for known LHON genetic mutations, one for the 11778 mutation and one for the 3460 mutation. CONCLUSIONS: The diagnosis of LHON should be considered in all patients diagnosed as having tobacco-alcohol amblyopia, particularly those with visual acuities of 20/200 or less. The availability of molecular genetic testing for LHON now allows confirmation of the diagnosis of LHON in patients who otherwise may be misdiagnosed.

Adult↗
PubMed1988

Short latency visual evoked potentials in functional amblyopia shown using moving topography.

The conduction from the eye to the visual cortex through the brainstem was investigated in 43 cases of functional amblyopia by means of moving topography of short latency visual evoked potential (SVEP). Anomaly of the SVEP such as a defect of the main component and remarkable reduction of amplitude was found in cases with severe amblyopia whose visual acuity was less than 0.5. The incidence of abnormal SVEP was recognized in 44% of anisometropic amblyopia (18 cases), 52% of strabismic amblyopia (15 cases), and 50% of deprivation amblyopia (10 cases). The results suggested a reduction of electric activity in the subcortical visual pathway including transmitting nuclei.

Adolescent↗
PubMed1996

Is the motion system relatively spared in amblyopia? Evidence from cortical evoked responses.

Visual evoked potentials (VEPs) produced by pattern reversal were compared with those elicited by onset of motion in 37 amblyopic children (20 with anisometropic amblyopia, seven with strabismic amblyopia and 10 with both anisometropia and strabismus). The amplitudes and peak latencies of the main P1 peak in the pattern-reversal VEP and of the motion-specific N2 peak in the motion-onset VEP through the amblyopic eye were compared with those through the normal fellow eye. Regardless of the type of amblyopia, the amplitude of the pattern-reversal VEP for full-field stimulation was significantly smaller and its latency significantly longer through the amblyopic eye (P < 0.001). In contrast, neither the amplitudes nor the latencies of the N2 motion-onset VEPs differed significantly between amblyopic and non-amblyopic eyes. For pattern-reversal VEPs through the amblyopic eyes, the extent to which amplitude was reduced and latency prolonged correlated well with the reduction of visual acuity, whereas the amplitudes and latencies of motion-onset VEPs did not vary with visual acuity. Even for stimuli restricted to the central visual field (5 or 2 deg diameter) or to the peripheral field (excluding the central 5 deg), motion-onset responses were indistinguishable through the two eyes, while pattern-reversal responses always differed significantly in amplitude. These results suggest that the source of motion-onset VEPs (probably an extrastriate motion-sensitive area) is less affected in amblyopia than that of pattern-reversal VEPs (probably the striate cortex). The motion pathway, presumably deriving mainly from the magnocellular layers of the lateral geniculate nucleus, may be relatively spared in amblyopia.

Adolescent↗
PubMed2005

Visual outcome and success of amblyopia treatment in unilateral small posterior lens opacities and lenticonus initially treated nonsurgically.

PURPOSE: We sought to assess the success of amblyopia treatment in patients with small posterior lens opacities as well as the factors associated with a good visual outcome. METHODS: This was a retrospective study of patients with posterior lens opacities that initially were thought to be too small in size to warrant cataract surgery. The following variables were examined: cataract type, location, diameter, persistent hyaloid vessel, anisometropia, strabismus, and age of detection. Success of treatment of amblyopia was defined as improvement by at least 0.3 logMAR units. Good visual outcome was defined as 20/40 or better. Amblyopia was treated by glasses, patching, and/or atropine. Patients who failed with conservative treatment or had an increase in cataract size underwent surgery. RESULTS: Forty-eight (91%) of 53 eyes were amblyopic. Thirty amblyopic eyes had pre- and post-treatment Snellen acuities. Twenty (67%) had their visual acuity (VA) improved by 0.3 logMAR units or greater. None of the measured variables were associated with successful amblyopia treatment. Twenty-five (49%) of 51 patients had a final VA of 20/40 or better. The only variable associated with good visual outcome was cataract type: 18 of 25 (72%) posterior subcapsular cataract and 6 of 23 (32%) posterior lenticonus eyes achieved VA of 20/40 or better (P = 0.008). Six patients who went on to have cataract surgery experienced a larger improvement in BCVA (4.50 logMar units +/- 2.52 lines) compared with patients treated without cataract surgery (2.36 logMar units +/- 3.11 lines). DISCUSSION: Amblyopia treatment was successful in most cases. A small group of patients who underwent cataract surgery experienced a greater VA improvement; however, it was not statistically significant. Further studies are needed to determine which patients would benefit from cataract surgery.

Amblyopia↗
PubMed2005

The effect of amblyopia therapy on ocular alignment.

PURPOSE: We sought to describe the change in ocular alignment at 2 years after treatment of amblyopia in children younger than 7 years of age at enrollment. METHODS: A randomized clinical trial of patching versus atropine for 6 months followed by standard clinical care for 18 months was conducted in 357 children with anisometropic, strabismic, or combined amblyopia (20/40-20/100) whose ages ranged from 3 to younger than 7 years at enrollment. Ocular alignment was evaluated at enrollment and after 2 years of follow-up. RESULTS: At enrollment when tested at distance fixation, 161 (45%) children were orthotropic, 91 (25%) had a microtropia (1-8 Delta), and 105 (29%) had a heterotropia >8 Delta. Of the 161 patients with no strabismus, similar proportions of patients initially assigned to the patching and atropine groups developed new strabismus by 2 years (18% vs. 16%, P = 0.84). Of these cases of new strabismus, only 2 patients in the patching group and 3 patients in the atropine group developed a deviation that was greater than 8 Delta. Microtropia at enrollment progressed to a deviation greater than 8 Delta with similar frequency in both treatment groups (13% vs. 15%, P = 1.00). Of the 105 patients with strabismus greater than 8 Delta at enrollment, 13% of those in the patching group and 16% of those in the atropine group improved to orthotropia without strabismus surgery. Strabismus surgery was performed in 32 patients during the 2-year study period. CONCLUSIONS: Patients who had amblyopia treatment with patching or atropine for 6 months followed by standard clinical care were found to have similar rates of deterioration and improvement of ocular alignment. When parents begin amblyopia treatment for children without strabismus, they should be warned of the possibility of development of strabismus, although it is most often a small angle deviation. Strabismus resolved after amblyopia therapy in some cases.

Amblyopia↗
PubMed2006

Strabismus and amblyopia in bilateral Peters anomaly.

BACKGROUND: Peters anomaly is a rare form of anterior segment dysgenesis in which abnormal cleavage of the anterior chamber occurs at the end of the third week of gestation. We examined the prevalence of strabismus and amblyopia and analyzed predictive factors for their development, as well as the visual outcome and associated anomalies in patients with bilateral Peters anomaly. METHODS: Using a retrospective review, we identified 25 consecutive patients with bilateral Peters anomaly who were observed between August 1995 and February 2005. Ocular structural and systemic anomalies, amblyopia therapy, visual acuity, and binocular alignment at last visit were recorded. Fisher's exact test was used to identify any association between defined predictive factors and the development of strabismus. RESULTS: Mean follow-up time was 5.1 year (range, 0.5-21 years). Median age at presentation was 2.5 months (range, 1 day to 13 years). Penetrating keratoplasties were performed on 34 eyes in 20 patients. Final best-corrected visual acuity ranged from 20/25 to no light perception. Thirteen of 18 patients with recorded motility (72%) developed strabismus: esotropia (n = 7), exotropia (n = 5), and variable (n = 1); one also had dissociated vertical deviation. Patients with equal vision were either orthophoric (n = 4) or had intermittent esotropia (n = 1), whereas strabismus occurred in 100% of patients whose vision was asymmetric by more than 1.5 octaves. Asymmetric vision was the only statistically significant predictive factor for the development of strabismus (P = 0.002). Amblyopia treatment resulted in improved vision in 3 of 5 patients. CONCLUSION: Strabismus occurs frequently in bilateral Peters anomaly. Asymmetric vision, (because of ocular structural anomalies) postoperative complications, and amblyopia may predispose to strabismus. Despite ocular structural limitations, amblyopia therapy is recommended in the aggressive rehabilitation of these eyes.

Amblyopia↗
PubMed2006

Risk factors for amblyopia in children with capillary hemangiomas of the eyelids and orbit.

INTRODUCTION: Capillary hemangiomas are the most common orbital tumors of childhood and can cause amblyopia secondary to occlusion of the pupil, anisometropia, or strabismus. We undertook this study to describe the clinical characteristics of children with capillary hemangiomas and to propose a classification system to guide clinical treatment decisions. METHODS: A retrospective review of the records of 129 patients with 132 capillary hemangiomas in two pediatric ophthalmology practices was conducted. Hemangiomas were classified based on size. Presence of aniosometropic astigmatism, ptosis, pupillary occlusion, lid margin change, proptosis, globe displacement, and strabismus was recorded. RESULTS: Thirty-one hemangiomas measured less than 1 cm in greatest dimension and were not associated with amblyogenic factors. Seventy-five patients had hemangiomas that measured greater than 1 cm, 40 of which were associated with amblyopia. Eighteen children had diffuse hemangiomas that could not be measured and 14 of these were associated with amblyopia. Five of seven hemangiomas in six patients with PHACES syndrome were associated with amblyopia. CONCLUSION: This study is the largest review of capillary hemangiomas of the orbit and eyelids. Our findings suggest that size greater than 1 cm in largest diameter is an important predictor of amblyogenic factors and approximately half of these patients will require treatment. Diffuse hemangiomas and hemangiomas in patients with PHACES syndrome will cause amblyopia in the majority of cases.

Amblyopia↗
PubMed2005

Long-term outcomes of photorefractive keratectomy for anisometropic amblyopia in children.

PURPOSE: To evaluate the long-term visual acuity (VA) and refractive error responses to excimer laser photorefractive keratectomy (PRK) for treatment of anisometropic amblyopia in children. DESIGN: Prospective interventional case-control study. PARTICIPANTS: Eleven children, 2 to 11 years old, with anisometropic amblyopia who were noncompliant with conventional therapy with glasses or contact lenses and occlusion therapy were treated with PRK. A cohort derived retrospectively of 13 compliant and 10 noncompliant children with refractive errors similar to those of the PRK group who were treated with traditional anisometropic amblyopia therapy served as control groups. INTERVENTION: Photorefractive keratectomy for the eye with the higher refractive error. MAIN OUTCOME MEASURES: (1) Refractive error reduction and stability in the treated eye, (2) cycloplegic refraction, (3) VA, (4) stereoacuity, and (5) corneal haze up to 3 years after PRK. Compliant and noncompliant children with anisometropia amblyopia were analyzed as controls for refractive error and VA. RESULTS: Preoperative refractive errors were -13.70 diopters (D) (+/-3.77) for the myopic group and +4.75 D (+/-0.50) for the hyperopic group. Mean postoperative refractive errors at last follow-up (mean, 31 months) were -3.55 D (+/-2.2.5) and +1.41 D (+/-1.07) for the myopic and hyperopic groups, respectively. At last follow-up, cycloplegic refractions in 4 (50%) of 8 myopes and all hyperopes (100%) were within 3 D of that of the fellow eye. Five (63%) of 8 myopic children achieved a refraction within 2 D of the target refraction. Two (67%) of 3 hyperopic patients maintained their refractions within 2 D of the target. Refractive regressions (from 1 year after surgery to last follow-up) were 0.50+/-1.41 D (myopes) and 0.60+/-0.57 D (hyperopes). Seven children (77%) were able to perform psychophysical VA testing preoperatively and postoperatively. Five (71%) of the 7 children had uncorrected VA improvement of at least 2 lines, and 4 (57%) of 7 had best spectacle-corrected VA improvement of at least 2 lines, with 1 improving 7 lines. Five (55%) of 9 children had improvement of their stereoacuity at last follow-up. Subepithelial corneal haze remained negligible. The mean final VA of the PRK group was significantly better than that of the noncompliant control group (P = 0.003). The mean final refractive error for both myopic and hyperopic groups was also significantly better that that of the control groups (P = 0.007 and P<0.0001, respectively). CONCLUSIONS: Photorefractive keratectomy for severe anisometropic amblyopia in children resulted in long-term stable reduction in refractive error and improvement in VA and stereopsis, with negligible persistent corneal haze.

Amblyopia↗
PubMed2006

Identification of contrast-defined letters benefits from perceptual learning in adults with amblyopia.

Amblyopes show specific deficits in processing second-order spatial information (e.g. Wong, Levi, & McGraw (2001). Is second-order spatial loss in amblyopia explained by the loss of first-order spatial input? Vision Research, 41, 2951-2960). Recent work suggests there is a significant degree of plasticity in the visual pathway that processes first-order spatial information in adults with amblyopia. In this study, we asked whether or not there is similar plasticity in the ability to process second-order spatial information in adults with amblyopia. Ten adult observers with amblyopia (five strabismic, four anisometropic and one mixed) were trained to identify contrast-defined (second-order) letters using their amblyopic eyes. Before and after training, we determined observers' contrast thresholds for identifying luminance-defined (first-order) and contrast-defined letters, separately for the non-amblyopic and amblyopic eyes. Following training, eight of the 10 observers showed a significant reduction in contrast thresholds for identifying contrast-defined letters with the amblyopic eye. Five of these observers also showed a partial transfer of improvement to their fellow untrained non-amblyopic eye for identifying contrast-defined letters. There was a small but statistically significant transfer to the untrained task of identifying luminance-defined letters in the same trained eye. Similar to first-order spatial tasks, adults with amblyopia benefit from perceptual learning for identifying contrast-defined letters in their amblyopic eyes, suggesting a sizeable degree of plasticity in the visual pathway for processing second-order spatial information.

Adaptation, Ocular↗