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1. The foveal visual evoked response is diminished or absent in strabismic amblyopia. This confirms the early report of van Balen & Henkes. 2. There is no such finding in hysterical amblyopia. 3. On the basis of the work of Hubel & Wiesel in experimental animals this confirms the idea that strabismic amblyopia corresponds to an anatomical defect and hysterical amblyopia does not. 4. Practical applications of these findings are suggested.

Introduction Investigations into the nature of amblyopia ex anopsia and into the behavior of the amblyopic eye have aroused renewed interest during recent years. In 1952 Brock and Givner, 1 and somewhat later Jaffe and Brock, 2 reported on a test by means of which they attempted to show that many amblyopic eyes fixated eccentrically. This work has been widely cited, and some rather far-reaching conclusions have been drawn from it (Linksz 3 ). However, to our knowledge no one has troubled actually to repeat this test and to determine its validity or limitations. We have, therefore, undertaken to do this and are presenting our findings in this paper. Methods and Clinical Material The test of Brock and Givner applies to patients with amblyopia the well-known fact that an after-image, produced in one eye, can be accurately localized by most subjects when the exposed eye is occluded and the contralateral, unexposed

To compare the visual evoked potential (VEP) responses of amblyopic eyes with VEP responses of sound eyes in amblyopic children. A study of 65 amblyopic children with pattern-reversal VEPs elicited by checkerboard stimuli with large, medium and small checks. The children were classified into three groups: Group A, 22 children with anisometropic amblyopia; Group B, 16 children with exotropic strabismic amblyopia; and Group C, 27 children with esotropic strabismic amblyopia. Visual acuity (VA) was significantly worse in the amblyopic eye as compared to the sound eye. However, no statistically significant difference was found between the amblyopic and sound eye of amblyopic children in the three groups for VEP P1 amplitude and latencies for any check sizes. VEP is a very important tool in understanding the complex amblyopic mechanism. Although the sound eye has superior VA, the absence of differences in VEP P1 amplitudes and latencies demonstrate the functional abnormality of the eye considered 'good'. More studies are necessary to explain why the sound eye in amblyopic children cannot be considered completely normal. Special attention should therefore be paid to amblyopic treatment, as patching can have a negative effect on the sound eye.

We compared detectability of a dotted line masked by random-dot noise for the amblyopic versus non-amblyopic eye of two strabismic amblyopes. Small but consistent deficits in the amblyopic eye of these observers were found, and shown to be limited to dotted-line targets composed of greater than seven dots (with performance being normal for targets of less than seven dots). These deficits were unrelated to impaired visual acuity, impaired sensitivity to dot density, and differential positional uncertainty between the eyes of our observers. The deficits were also unlikely to be due to CSF losses due to abnormal low-spatial-frequency filters involved in detecting long chains of collinear dots. Instead, the results of simulations indicate that the inefficiency in utilising large numbers of dots is due to deficits of global, integrative processes in strabismic amblyopes. These simulations also show that while neither undersampling nor positional uncertainty of inputs into integrative processes can themselves account for the amblyopic deficits, if such abnormal inputs lead to the development of stunted integrative processes then impaired sensitivity to long chains of collinear dots is indeed predicted.

A recent report suggests that amblyopes are deficient in processing local orientation at supra-threshold contrasts. To determine whether amblyopes are also poor at integrating local orientation signals, we assessed performance for an orientation integration task in which the orientations of static signals are integrated across space. Our results show that amblyopic visual systems can integrate local static oriented signals with the same level of efficiency as normal visual systems. Although internal noise was slightly elevated, there was no indication that fewer samples were used to achieve optimal performance. This finding suggests normal integration of local orientation signals in amblyopia.

Monocular afterimages of a vertical line were generated in each eye of binocularly normal individuals and of those lacking binocular single vision or stereopsis as a consequence of childhood strabismus. Fragmentations and disappearances of the afterimages occurred less frequently in the strabismic than in the normal subjects; they were also less frequent in the dominant (nonamblyopic) eyes of the strabismics than in their amblyopic eyes. The afterimages remained visible for longer when presented to the dominant eyes of the strabismic subjects, and a similar effect was found between the sighting dominant and nondominant eyes of normal subjects.

Six patients are presented with ametropic amblyopia secondary to bilateral hypermetropia. Two patients had a strabismic amblyopia superimposed upon the ametropic amblyopia. All patients had a marked improvement in their visual acuity with the use of constant glass wear only No associated ocular pathology was identified. It is the authors' belief that these patients are seen occasionally in general ophthalmologic practice. The diagnosis and treatment is straightforward; however, the diagnosis can be perplexing and unnecessary referrals and neuro-ophthalmologic investigation can ensue if this entity is not recognized.

A total of 6 patients, 2 with anisometropic, 2 with strabismic and anisometropic, and 2 with strabismic amblyopia treated with the 'gratings method' showed more than 2 lines of improvement in linear visual acuity. Patient attention and interest and repeated testing of the visual acuity were uncontrolled factors in this study. Moreover, the detailed visual tasks performed by the amblyopic eye may in themselves be the reason for improvement. Clearly a careful study which controls these possibilities is needed before a claim can be made that the 'gratings' per se offer an improved method of treatment of amblyopia.

(1976). Relationship between Amblyopia and the Angle of Strabismus. American Orthoptic Journal: Vol. 26, No. 1, pp. 31-33.

Background : Aberrant regeneration of the third cranial nerve is most commonly due to its damage by trauma. Case : A ten-month old child presented with the history of a fall from a four-storey building. She developed traumatic third nerve palsy and eventually the clinical features of aberrant regeneration of the third cranial nerve. The adduction of the eye improved over time. She was advised for patching for the strabismic amblyopia as well. Conclusion : Traumatic third nerve palsy may result in aberrant regeneration of the third cranial nerve. In younger patients, motility of the eye in different gazes may improve over time. DOI: http://dx.doi.org/10.3126/nepjoph.v4i1.5872 NEPJOPH 2012; 4(1): 176-178

A detailed report is presented on the first published case of a concomitant squint in an adult, with deep amblyopia with eccentric fixation in the left eye, in which operative intervention alone normalized inhibition, fixation and correspondence simultaneously. The mechanism of this normalization is explained.

Visual acuity was examined in patients successfully treated for strabismic amblyopia, and with equal refractive error in the two eyes (no more of 4 diopters of hyperopia). Patients able to freely alternate fixation showed equal visual acuity in the two eyes without optical correction. An optical correction in front of the ex-amblyopic eye was needed, in order to achieve equal visual acuity in patients unable to freely alternate fixation. No correction was necessary for the sound eye. This difference is attributed to a residual anomaly of accomodation of the ex-amblyopic eye. It is concluded that the concept of cure of strabismic amblyopia based on the attainment of equal visual acuity needs re-evaluation.

17 amblyopic children between 4 and 9 years were fitted with high power plus extended wear soft contact lenses (Scanlens 24 h, Duragel 75) for optical occlusion of strabismic amblyopia. Amblyopia and eccentric fixation responded quickly to treatment between 2 to 13 weeks. Only one patient failed to reach 6/9, and 11 patients achieved equal visual acuity. Out of 10 patients with eccentric fixation only two remained eccentric after treatment. The contact lenses were tolerated by the children. Among the problems, concerning the use of extended wear soft contact lenses, should be mentioned fitting problems, deposits, loss of lenses (1 child needed 4 lenses) and occurrence of conjunctivitis (5 eyes). No major infections were seen. A one year follow-up showed that almost all the children needed renewed occlusion treatment. It is therefore recommended to continue with contact lens occlusion for at total period of 3 months.

Of a series of 57 formerly amblyopic patients who attained equal visual acuities (20/20 or better in each eye), only 29 were able to alternate after treatment. The oldest patient was 5 years old. The pattern visual-evoked response of the previously amblyopic eye in nonalternators showed a reduced amplitude as compared with that of the sound eye. This probably occurred because of a reduced number of cortical cells subserving the formerly amblyopic eye. Lack of alternation may be the result of cortical competition. More cortical cells are connected to the originally normal eye even after successful treatment of the amblyopic eye in the nonalternating patient.

We investigated whether in strabismic amblyopia deficiencies of color vision may exist which are inaccessible to conventional testing methodologies. More specifically, we compared amblyopic contrast sensitivities for luminance- and wavelength-modulated gratings in the same patients

A horizontal concomitant strabismus produced optically in kittens with prisms caused a decrease in the proportion of binocularly excitable striate neurons with approximately equal percentages of neurons being driven by each eye. In addition, preventing fusion with prisms resulted in alterations in interocular alignment and in some cases a mild strabismic amblyopia. The changes in ocular dominance were dependent on the amount and direction of the prism induced deviation; however, regardless of the type of prisms worn, the kittens which demonstrated interocular misalignments were esotropic.

Of 78 consecutive cases with constant unilateral esotropia diagnosed during screening and treated from the ages of seven months to three years, 82% ended up with visual acuity of 6/12 or better toward end of active treatment at the age of six to eight years. Of the cases with visual acuity of 6/12 or better at the end of treatment, 59% retained their vision when re-examined four to ten years later. The most important single parameter for the achievement of normal visual acuity was age of onset of treatment below two years and for long-term stability of the result this age dropped to 18 months. Initial large angles of esotropia had better prognosis probably because they were associated with an earlier onset of treatment. Poor prognosis was associated with faulty or no fixation of the esotropic eye when first diagnosed, with the failure to achieve alternation and with marked ansiometry. The optimal age for screening for strabismic amblyopia was suggested to be 12-18 months.

Using the binocular fixation pattern (BFP) and the visually evoked potential (VEP), thirteen amblyopic patients with comitant, non-accommodative esotropia with an angle range up to 30 delta were studied before and during occlusion therapy. A graded BFP with a stronger preferred fixation could be used to diagnose amblyopia. The BFP, however, showed no significant change with therapy despite improvement in acuity. In contrast, the VEP amplitudes, initially reduced in amblyopia, increased significantly as the vision responded to patching. The VEP was useful in diagnosing strabismic amblyopia and giving a predictive range of acuities.

One hundred thirty patients with strabismic amblyopia who underwent full-time occlusion therapy (FTO) and were followed through to at least 9 years of age were evaluated to determine the stability of visual acuity after visual maturity (after 9 years of age). Of these 130 patients, 89 are included in this review. At the conclusion of the FTO therapy, 92% (82/89) had attained a visual acuity of 20/40 or better, 6% (5/89) had attained 20/50-20/100, and 2% (2/89) remained at 20/200 or less. Of the nine patients in this series in whom patching was initiated between the ages of 6 and 9 years of age, a good visual result was seen in 89% (8/9), with 63% (5/8) of those attaining 20/20 vision. The final visual acuity in this group of patients was taken at an average patient age of 15.9 years. In 75% of the patients (67/89) there was no change in visual acuity over time, while 17% (15/89) showed a one- or two-line decrease, and in 8% (7/89) vision dropped more than two lines. Of those patients who had greater than or equal to 20/40, 88% (56/64) who had a posttreatment visual acuity of 20/20 showed no change at the final evaluation, but only 50% (9/18) of those whose posttreatment vision was between 20/25 and 20/40 were stable. In those patients who needed part-time occlusion (PTO) to maintain equal visual acuity, their stability appeared to be the same as the vision of those whose vision was maintained without PTO.

The effect of reducing background luminance on contrast thresholds for different forms of amblyopia was investigated. As expected from previous acuity studies strabismic and organic amblyopia exhibit dramatically different behaviour; for a particular spatial frequency the degree of strabismic amblyopia reduces with reducing luminance whereas organic amblyopia does not. Unexpectedly, there is a similar difference in the behaviour of strabismic and anisometropic amblyopia. This difference suggests that these two forms of “functional” amblyopia do not have identical neural bases. An hypothesis concerning the extent of the abnormality within the visual field is advanced to explain these luminance dependent results.

Optical penalization for distance is a useful alternative to occlusion for treating amblyopia, and as maintenance therapy following occlusion. It is particularly useful in cases of patching noncompliance. The major key to patient acceptance is choosing the minimal amount of penalization necessary, while still ensuring that the patient actually switches fixation to the amblyopic eye. We have found the vectographic letter slide reliable for identifying the fixing eye for distance vision. Thirty-four patients were treated for anisometropic or strabismic amblyopia with distance optical penalization without the use of cycloplegic agents. Twenty-two patients had improvement of their visual acuity, and 10 patients remained the same during an average follow-up period of 22.5 months. The average visual acuity improved from 20/40 to 20/32. The dominant eye required an average of only +1.25 diopters of fogging for the patient to switch fixation to the amblyopic eye, significantly less than the arbitrary +3.00 diopters advocated by some clinicians.

The grating acuity of 181 patients from 6 weeks to 18 years of age who had neurological abnormalities and documented developmental delay was assessed using preferential looking (PL) procedures. PL acuities were estimated by a staircase procedure in 79% of all patients (143 of 181) on the first attempt. PL acuities were poorer than normal on the average in all patient groups, including those without ophthalmological disorders. However, PL acuities varied systematically with the severity of the eye disorder in each category, with two exceptions, high refractive error and nystagmus. Interocular acuity differences were sensitive to such asymmetric eye disorders as strabismic amblyopia and unilateral ocular abnormalities and enabled monitoring of occlusion therapy for these conditions. Many patients who were ‘visually inattentive’ despite the absence of major ophthalmological abnormalities were testable but had very poor acuity. This study evaluates the clinical applicability of PL procedures for routine assessment of visual acuity in pediatric patients with developmental disabilities.

In binocular rivalry the time during which different stimuli are perceived depends--amongst other things--on their spatial frequency (sf) contents, on contrast and on orientation. Limiting the sf-range of both periodic and aperiodic stimuli in different ways (while keeping the contrast constant) decreased their predominance. This result seems to corroborate the concept of spatial frequency channels in human vision. Decreasing the contrast also decreased predominance. Thus blurred patterns are suppressed by sharply focused ones because of both their lower contrast and their loss of high sf's. This has consequences for the therapy of strabismic amblyopia. Obliquely oriented patterns were almost as dominant as vertical ones and much more than horizontal ones. Instead of a conventional "oblique-effect" we found a "vertical-effect".

Binocular mixtures of equiluminous components of different wavelengths were matched with additive monoptic mixtures of the same components. After a satisfactory match had been achieved, the luminance of each colour in the monoptic mixture was measured photometrically. After presentation of an orthogonal grating superimposed on the colour shown to one eye, the colour matching was repeated. The grating induced a strong dominance of the colour with which it was combined. Yet the uncontoured colour was not entirely suppressed, but contributed to the binocular colour to various degrees. In three subjects with anisometropic amblyopia in one eye the colour presented to the amblyopic eye contributed little or nothing to the haploscopic colour mixture, depending on the degree of amblyopia. This diminished contribution could not be enhanced by a grid. In three cases with strabismic amblyopia and in one case with strabismus alternans no haploscopic colour mixture effects could be demonstrated. The observations are discussed in the context of neurophysiological findings in the visual system of primates, and it is suggested that colour and contour are not transmitted through independent channels from the retina to the cortex.

Reduced visual acuity is the most notable feature of functional amblyopia--so much so that it is common to think that it is the only, main, or even the fundamental defect. To identify all amblyopic eyes by acuity alone would require an acuity criterion of 6/6 (20/20) or somewhat better acuity--a criterion that would necessarily include more normal than amblyopic eyes. The association of amblyopia with strabismus and anisometropia is sufficiently specific to make these two nonacuity features useful in identifying amblyopia. The diagnosis of amblyopia derives from a syndrome of features, most of which are nonacuity features. Two recently quantified nonacuity features--spatial uncertainty and distortion--are not only clinically useful but they may be the fundamental defects in strabismic amblyopia, with impaired resolution being fundamental in anisometropic amblyopia.

We used a neutral density filter to assess motor responses in the fixation patterns of 25 patients, ranging in age from 5 to 54 years, with strabismic amblyopia. Shifts of fixation back to the preferred eye occurred when the visual acuity of the preferred eye through the filter was marginally better than that of the amblyopic eye. Thus, we were able to correlate the level of the filter at which this shift occurred with the level of amblyopia. This technique may be particularly helpful in the examination of preliterate children and in monitoring the progress in the treatment of amblyopia.

The postnatal development of the visual field in human infants is less well understood than that of visual acuity. Recent studies indicate that the visual field is not yet fully expanded at birth. Especially the nasal field appears to be rather constricted or even blind as compared to the temporal field, and its development lags behind (Maurer et al 1983). Similar findings have been obtained in kittens (Sireteanu & Maurer 1982). Experiments in kittens have further shown that the normal development of the visual field depends on a normal visual stimulation as does the development of visual acuity. Monocular deprivation and strabismus hamper the normal expansion of the visual field, especially that of the nasal field (Gordon et al 1979; Ikeda & Jacobson 1977; Peck et al 1980; Sherman 1973; Tumosa et al 1982; Van Hof-Van Duin 1977; Zablocka & Van Hof-Van Duin 1980).

Tolhurst (1973) had suggested that movement-sensitive mechanisms were the human analogues of transient (Y) neurones in the cat (Enroth-Cugell and Robson 1966) and monkey (Gouras 1968) visual system. We challenged this view in a previous study (Rentschler et al. 1981): in strabismic amblyopia the detection of apparent movement of counterphased gratings is impaired considerably more than pattern detection, whereas no such anomaly is found when the sensitivity to temporal transients is tested. This would imply that with a grating target the detection of lateral movement and of transients is not mediated by the same class of mechanisms. Moreover, we have shown that normal peripheral vision suffers qualitatively from the same kind of movement insensitivity as the amblyopic eye. In this study, we have used a wider range of stimulus parameters to seek more definite evidence.

Penalization therapy for strabismic amblyopia is indicated in the group over six years of age. Good visual acuity of 6/12 or better was achieved and maintained at least for two years in 74% of the 38 cases reported. Deep amblyopia of 6/60 or less is no contraindication to treatment, success being achieved in 50% of this group. It seems that previous occlusion treatment diminishes the rate of success. Close supervision during the treatment is mandatory to assure the desired use of the amblyopic eye.

Cone increment thresholds were measured in 18 patients with strabismic amblyopia using a hand-held stimulator ophthalmoscope that allowed the examiner to visualize the stimulus on the fundus and test known retinal loci. With this technique of static fundus perimetry, all patients with amblyopia showed small to moderate elevations in threshold at the foveola and 50% had a nasal-temporal asymmetry in thresholds. Nasal retinal thresholds were elevated in patients with esotropia while temporal retinal thresholds were elevated in patients with exotropia. In contrast, patients with juvenile macular degeneration showed profound threshold elevations at the foveola with symmetrical elevations of threshold at paracentral retinal loci.

Bilateral fluorescein retinal angiographic studies were performed on six persons with unilateral functional strabismic amblyopia. The angiograms were studied using single-blind method for changes that might be attributable to the amblyopia. No such changes were found.

2 cases of strabismic amblyopia which were successfully treated are examined. Later on, a slight myopia appeared in the fixating eye only, while the amblyopic eye remained practically emmetropic. The 2 patients had to wear monocular myopic correction, otherwise the visual acuity of the other eye would have been reduced below the visus (without correction) of the fixating but myopic eye. A third case was reported of a hypermetropic patient with a right amblyopic eye and a left fixating but myopic eye. After the appearance of myopic lesions in the dominating eye, pleoptical treatment was successfully given to the amblyopic eye, so that in the end it turned out better than the other eye. Also, in this case the patient was quite disturbed for a long time due to the interference of the eye which was originally better. The authors underline the importance of these interocular effects, both from the standpoint of practical and medical information.

Conventional occlusion of the sound eye improved visual acuity in 11 of 12 patients with latent nystagmus and strabismic amblyopia. The successful results reported in this study are in contradiction to current views that occlusion therapy is futile or even contraindicated in patients with amblyopia and latent nystagmus.

In the 47 months from September, 1981, 1531 new cases of amblyopia were identified in the ophthalmic clinics of Leicestershire. Amblyopia was due to strabismus in 689 (45%), combined strabismus and anisometropia in 540 (35%), anisometropia alone in 252 (17%), and form deprivation in 50 (3%). The median age at presentation for strabismic amblyopia (3.64 years) was significantly lower than for combined strabismus and anisometropia (4.68 years) and anisometropia (6.27 years). Boys presented later than girls, as did Asians compared with Caucasians. Only 38 (15%) of children with a visual defect without strabismus (anisometropia) were identified before the age of 5 years. The major reason for this late identification is the lack of a reliable single test for preschool vision assessment.

Focosi & Parducci (1978) reported two particular cases: two children in whom the vision of their ambliopic eye had practically returned to normal after rehabilitation. They were subsequently operated on and strabismus was satisfactorily corrected.

The amplitude of the visual-evoked cortical response (VER) elicited by stimulating one eye was compared with that elicited by stimulation of the fellow eye in one normal subject on 30 occasions and in 30 normal subjects on single occasions. The extent to which these responses varied was then used as a basis in evaluating the VER differences seen in patients with unilateral macular disease, refractive amblyopia and strabismic amblyopia. Significant VER differences were found in those patients with unilateral macular disease and in one patient with probable organic amblyopia. No significant VER differences were found in patients with refractive or strabismic amblyopia.

Strabismic amblyopia is one of several sensory adaptations produced by a malalignment of the visual axes. The disparity of images on corresponding portions of the two retinas during binocular vision leads to active inhibition (suppression) of images formed in the deviated eye. Under conditions yet unknown, suppression that is originally present only in binocular vision may develop into the complex sensory-motor syndrome of amblyopia, thus persisting even when the sound eye is covered. If the functions of the amblyopic eye are tested when the sound eye is closed, the resultant monocular situation is different from that under which the amblyopic eye functions in everyday seeing. Since the binocular problem that originally led to the development of amblyopia is thereby temporarily suspended, one would expect a decrease of the visual inhibition under these circumstances. The present study was undertaken in order to investigate the influence of different types of stimulation of

Twelve subjects with functional strabismic amblyopia were tested for aniseikonia under conditions of normal binocular viewing. Controls consisted of ten subjects with normal binocular single vision and ten with alternating strabismus and no amblyopia. A polarizing filter haploscope "direct visual comparison" eikonometer was used. In comparison with the controls, the amblyopic group showed a small degree of aniseikonia, averaging 0.3%. In the majority of these subjects, the amblyopic eye "perceived" the target pattern as being smaller than the identical target pattern "perceived" by the normal eye.

To investigate the effect of anisometropic and strabismic amblyopia on the nerve fiber layer thickness. This cross-sectional study was done on 54 amblyopic subjects, equally in both strabismic and anisometropic groups. The thickness otonerve fiber layer measured in superior, inferior, nasal, temporal quadrants and as a whole in both eyes of both groups. The means of thickness were compared in amblyopic and sound eyes. In strabismus group, the average nerve fiber layer thickness of the sound eye , in superior, inferior, nasal and temporal quadrants and as a whole were 113.23±14, 117.37±25, 68.96±6, 69.55±14 and 93.40±8 microns respectively. In amblyopic eyes of the same group, these measurements were 103.11±18, 67.74±11, and 69.59±16 and 89.59±12 microns in superior, inferior, nasal, temporal quadrants and as whole respectively. In anisometropic groups, the sound eye measurements were as 130.96±22, 129.07±29, 80.62±12, and 83.88±20 and 107.7±13 microns in superior, inferior, nasal and temporal quadrants and as a whole orderly. In amblyopic eyes of this group the mean thicknesses were 115.63±29, 133.15±25, 78.8±15, 80.2±16 and 109.17±21 microns in superior, inferior, nasal, temporal quadrants and as a whole respectively. Statistically, there were no significant differences between amblyopic and sound eyes (P0.5). Our study did not support any significant change in a nerve fiber layer thickness of amblyopic patients; however, decreased thickness in superior and nasal quadrants of strabismic amblyopia and except inferior quadrant and as a whole. These measurements may be a clue for management and prognosis of amblyopia in old age.

To the Editor: —In an article entitled "Fixation Patterns in Strabismic Amblyopia," by Paul J. Hauser and Hermann M. Burian, which appeared in the February, 1957, issue of the A. M. A.Archives of Ophthalmology, p. 254, the authors state in their introduction that the purpose of the paper is to determine the validity and limitations of the Brock test as reported by Brock and Givner in the A. M. A.Archives of Ophthalmology(47:775-786, 1952). In this article we concluded (1) that the vast majority of uniocular amblyopes fixate eccentrically and that the shift away from the center is greater the more profound the amblyopia; (2) that only about 20% of persons with uniocular amblyopia fixate along the central-fovea axis of the poor eye on occlusion of the good eye; their amblyopia is always moderate; (3) that 80% with alternating strabismus are incapable of after-image transfer, while 75% of