Normal and disordered visual development with preferential looking

Normal and disturbed development of grating acuity in preverbal infants has been studied using the Teller acuity card procedure. The results of 195 normal and 34 premature children are in good accordance with those reported in the literature. In more than 86% no interocular differences of grating acuity could be detected in these groups. On the other hand the incidence of interocular acuity differences reached 30% in 37 cases showing monolateral convergent squint. This is much higher than has been reported in current literature and may indicate that grating and Snellen acuity correlate better than expected in infants' squint amblyopia. As to the problem of monitoring early amblyopia therapy by PL, four longitudinal cases are presented.     

Late reoperations for squint.

Ten patients in the age range 2 to 22 years are described who had operations initially for squint in childhood. Nine had had concomitant convergent strabismus and one divergent. All presented again in adult life with a cosmetic complaint, but two also had diplopia. Reoperations were done, age range 14 to 43. These ten were all the "late reoperations" for squint which were done during the four year period 1972 to 1976 by one consultant (C.I.P.). Technically these late reoperations were not difficult, through the amount of change predictable in position of the eyeball could be only approximate. Recession +/- advancement +/- resection of horizontal recti were done in all cases. In one case no medial rectus was identified attached to the eyeball; a mass of tissue behind the caruncle was mobilised and sutured to the globe with resultant good movement. To avoid tethering of the eye by scarred conjunctiva, vertical conjunctival incisions were often converted at suturing to (see article) shaped wounds. The absence of any new cases of diplopia (the two who had it preoperatively retained it without aggravation) is attributed to the fact that all cases were under-corrected, i.e., no convergent or divergent squint was converted into a divergent or convergent squint respectively, so that the non-corresponding image remained within the area of suppression, which probably extends only to the vertical meridian in a squinting eye.     

The ocular dominance of cortical neurons in cats developed with divergent and convergent squint

In five normal cats, 70.7% of the neurons recorded from the visual cortex responded to binocular stimulation; only 27.2% of the neurons in 12 cats raised with convergent squint and 63.6% of neurons in four cats with divergent squint displayed binocularity. In cats with convergent squint, 15% of the neurons showed normal receptive fields through one eye and nonconnected scattered receptive fields through the nondominant eye; however, movement detection, velocity discrimination and unidirectionality were retained. Furthermore, 65.2% of the monocular neurons were found to react through the normal eye and the rest through the squinting eye.While 1.7% of cortical neurons did not respond to any visual stimulus in normal cats, it was 3.9% in cats with convergent squint.     

Concomitant strabismus: of strabismus in strabismus syndromes]

PURPOSE: To show how to progress from the deviation of the visual axis (provided the diagnosis of concomitant strabismus is certain) to the classification of the squint in one out of the different squint syndromes and consequently to adopt the appropriate therapeutic strategy. METHOD: Every sign correlated with the deviation contributes to progress step by step to the diagnosis of a given squint syndrome. The age on onset of strabismus, either convergent or divergent, and its characteristic, intermittent or constant, allow in a first step to evaluate the potential binocularity, as well in early as late (acquired) strabismus. The first group of early strabismus includes manifest infantile strabismus and microstrabismus. Both have abnormal binocularity. The possibility of functional amblyopia, angle variability and additional incomitances have to be investigated. Early intermittent strabismus keeping a potential normal binocularity are seldom. In the second group of late onset strabismus, retinal correspondence has to be investigated by correspondence tests and prism or bifocus compensation to distinguish between the two possible types (including the accommodative forms of strabismus), i.e. decompensated microstrabismus with abnormal binocularity or normosensorial strabismus with potential normal binocularity. In some cases potential binocularity may be initially uncertain and/or remain later on subnormal. RESULTS: As the result of this systematic approach, every cases of squint can be classified in one out of the different squint syndromes. Based on the precise diagnosis, the appropriate treatment can be carried out. The goals of treatment which can be reached in every syndrome are indicated. DISCUSSION: For an overall view of the squint syndromes a classification with two entrances are necessary, on the one hand early or late onset, on the other hand normal or abnormal binocular conditions. CONCLUSION: This approach of concomitant strabismus should serve as guide lines for clinical practice.     

Role of attention and eye preference in the binocular coordination of saccades in strabismus

This study examines squint change and the binocular coordination of horizontal and vertical saccades in an adult subject with incomitant strabismus (20 or 40 prism diopters) strongly depending on the eye used for fixating. The patient had no binocular vision and was diagnosed ‘horror fusionis’ since her childhood. We found the angle of horizontal squint to be smaller when the patient was fixating with the preferred eye than with the nonpreferred eye. The squint was smaller when both eyes viewed and one eye fixated attentionally than when the nonfixating eye was closed. This suggests the importance of binocular visual stimulation. We found no significant changes in the amplitude of the disconjugacy of the saccades. However, when the preferred, left eye fixated attentionally (under binocular viewing) or monocularly, the pattern of the disconjugacy changed: the majority of the saccades showed divergent disconjugacy. This pattern is qualitatively similar to that seen in normal subjects. In this patient, divergent disconjugacy helped to decrease the convergent squint at the end of the saccades. Interestingly, vertical squint was small and did not depend on viewing conditions. The binocular coordination of vertical saccades was almost normal, at least in the binocular viewing condition. We conclude that the visual input from both eyes allows a rudimentary binocular cooperation that helps to keep the squint small and renders disconjugacy of horizontal saccades strategically divergent to reduce temporally the squint.     

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Pattern-reversal electroretinograms(P-ERG)and visual evoked potential(P-VEP) were simultaneously recorded in 20 kittens reared with unilateral convergent strabismus,induced surgically at around 3 weeks after birth.P-VEP responses evoked through the normal and squint eyes consisted of two components at the initial stages,however changed systematically with age,and the second component of the squint eye disappesred earlier than that of the normal eye.P-ERG response for the variance in retinal function of squint eyes was more sensitive than the F-ERG.P-VEP responses from the squint eyes reduced significantly in amplitude as compared with those evoked through the normal eyes,even one week after surgery,while P-ERG responses unchanged and persisted through 30 weeks.Reduction of P-ERG amplitude of squint eyes developed about 6 weeks postnatal and the spatial resolution returned gradually at later stages.The results suggest that the strabismus may affect not only striate cortex,but also retina in developing kittens.In comparison with retinal deficits,cortical deficits may arise earlier and manifest more severe.     

Distance ESO Deviation—A Basic Deviation or Paralysis of Divergence

A Group of one hundred patients is described with the condition of distance eso deviation or convergent squint which is present for distance viewing together with an exo deviation for near viewing and in-between distance and near there is a neutral point or crossing distance where there is no deviation. The crossing distance determines the distance at which an exo deviation will be present. Accommodation increases the degree of eso deviation and shortens the crossing distance, especially in younger patients, but does not have much effect in presbyopic patients. Distance eso deviation occurs at all ages and varies in degree from a small phoria to an obvious tropia. It is a cause of diplopia in elderly patients, and may be the underlying cause of convergent squint in young patients. It is distinct from the rare condition of divergence paresis.     

Postoperativ binocular function after full prismatic correction in patients with concomitant convergent strabismus and exuberance of convergence (author's transl)]

We investigated the cases of 50 non amblyopic children with concomitant convergent strabismus and exuberance of convergence, in which a prolonged prismatic correction was performed. 31 children had a 5 degree higher angle of squint in near vision before the application of prism. In 13 out of 31 the angle of squint, which was measured at the gaze for distance, increased more than 6 degrees. The ratio of normal retinal correspondence (NRC) to abnormal retinal correspondence (ARC) is 14:17. 19 patients developed only after prismatic correction of the angle of squint an exuberance of convergence. This phenomenon we call secundary exuberance of convergence. In this group the angle of squint for distance vision increased in only three children more than 6 degrees, while 6 children had a decrease by up to 11 degrees. The ratio NRC: ARC is 7:12. Postoperativ follow-up of binocular function over 4-5 years showed, that the prognosis in case of primary exuberance of convergence is worse than in secondary.     

Blind spot syndrome in convergent strabismus of the horror-fusionis type

With reference to a case of convergent squint with early onset it is shown that a blind spot syndrome may develop if - in spite of sensory adaptation to the angle of squint - the patient lacks sufficiently deep suppression and the suppression scotoma is very small.     

Cyclic vertical deviation after ocular myositis and treatment by recession of the inferior rectus muscle

Background Cyclic strabismus is a rare disorder in which strabismus and orthotropia regularly alternate over a period of mostly 48 h. It may occur spontaneously, upon squint surgery, or in association with lesions of the central nervous system. In most cases the deviations are convergent. Methods Clinical case report. Results A 34-year-old woman with bilateral recurrent ocular myositis for 2 years had developed cyclic vertical deviation 6 months after clinical remission. A hypotropia of the left eye alternated with an orthotropia, following a 48-h rhythm. Three months after recession of the inferior rectus muscle the alternating squint had disappeared. Discussion The aetiology of cyclic eye deviations, most of them occurring in a constant rhythm, is not known. The association with lesions of the central nervous system indicates a primary central dysregulation of a “biological clock”. Their well-known occurrence, however, after squint surgery and, as in the present case, after orbital myositis, suggests that alteration of peripheral structures may contribute to a central dysregulation. Squint surgery seems to be the treatment of choice, even in rare cases with vertical deviations. Presented at the DOG, Berlin, 2003     

Strabismus and meningomyelocele

About a half of a group of patients with meningomyelocele have some form of squint. The occurrence of squint appears to be related to the occurrence of hydrocephalus. The incidence of squint increases with the existence of epileptic symptoms and with a low level of intelligence. Amblyopia is seldom seen in the patients with convergent squint.     

Unusual perceptions with the Pola Test in a case of esotropia with anomalous correspondence

That the Pola test figures of heterophoric subjects with fixation disparities are described as deformed at times, was published by H. J. Haase two decades ago. The main subject in this publication is a 13-year-old boy with early childhood convergent strabismus, in which the "squint therapy" which was used at that time, did not change the angle of squint and the anomalous correspondence to any extent. The corrected visual acuity was the same bilaterally, 1.0 to 1.1. If the esotropic eye position was corrected as well as possible with prisms to the objective angle, a change between diplopia and binocular fusion occurred; occasionally even to "normal corresponding" fusion with correct stereopsis. In the transition phases the test level appeared to be more or less drawn out in width, and the half figures underwent all kinds of "somersaults". Binocular macropsia and monocular micropsia and macropsia, and also polyopia and unusual depth effects were described. Confusion did not occur; all pictures had form. These rare phenomena were interpreted as a competition between established anomalous and latent normal correspondence. This communication should stimulate further observations of this type and, should the occasion arise, lead to experimental research.     

The clinical characteristics and treatment tactics of vertical strabismus

Examination of 328 patients with vertical squint has revealed peculiarities of its clinical forms. Their characteristics are: I. Concomitant vertical squint; II. A mixed form--concomitant convergent or divergent squint with a vertical component; III. Paretic or paralytic vertical squint; IV. Atypical kinds of vertical squint. Special attention is drawn to the presence of torticollis, difference in lid slit width, pseudoptosis, diplopia. Basic principles of treatment of vertical squint corresponding the clinical form are suggested. Results of treatment in patients with different forms of vertical squint are analysed.     

The problem of screening children for visual defects.

All the cases of squint and amblyopia referred to both hospital and school clinics in one district during one calendar year have been reviewed in order to clarify when, where, and how these cases first present to the ophthalmologist. The types of case at present seen in "hospital" and "school" clinics are quite different, and effective screening methods are unlikely to be developed if these two services continue to be regarded as separate entities. Exotropia is much less frequent than esotropia (only 15% of all cases of squint). The concept of a single peak number of first attendances of children with esotropia at age 3 to 4 years is not substantiated. There is a second peak at age 5 years, when children first go to school. In fact 49% first attended after their fifth birthday. The majority (69%) of cases of amblyopia presented after the age of 5 years. Three-quarters of these (46% of the total) have no clinically detectable squint. Neither they, nor those children who have a strabismic amblyopia, but not a cosmetically noticable squint, will at present be detected until they have a sight test at school. This is a measure of the need to re-examine our long-established methods of screening children for amblyopia. One screening test designed to identify both the "squinter" and the "straight-eyed amblyope" is required.     

Clinical picture and treatment of diplopia

A total of 203 patients with stable binocular diplopia were observed. Examinations included coordimetry, analysis of double images, and investigation of the doubling field in the gaze field. All examinations were performed using an original method with a serial computer. The treatment included therapy of the underlying disease, choice of correcting prisms, exercises aimed at extension of separate vision field, and operation on the oculomotor muscles. Three main forms of diplopia were distinguished: 1) muscular; 2) sensory; and 3) mixed. The first form includes diplopias in paresis of n.III and n.IV, n.VI, late development of convergent squint, orbital injuries, endocrine ophthalmopathy, and myasthenia. The second form includes diplopias developing after delayed operations for convergent squint, and the third form are diplopias after operations for detachment of the retina and implantation of intraocular lenses. The treatment led to complete neutralization of doubling in 18.7% cases, neutralization in the main part of the gaze field in 53.7%, the same with prism correction in 12.8% cases; in 14.8% patients adaptation to diplopia was attained after suppression of the second image. Diplopia in late squint is prognostically the most favorable, and the following conditions are listed in the order of more or less good prognosis: paresis of n.VI, n.IV, orbital injuries, endocrine ophthalmopathy, and artiphakia. The least favorable prognoses are for patients after delayed operation for squint and detachment of the retina. A new operation, plastic repair of the external m. rectus, was used in 96 patients with pareses of n.VI; no compensation was attained in only 2 patients.     

The results of surgery on squint with pathological muscle attachment

The aim of our study was to evaluate the results of the operation on squint with pathological attachment of lateral rectus revealed during surgery. MATERIAL AND METHODS: The study involved 22 children (12 girls and 10 boys) out of 320 children operated on for squint in the years 1993-1996, who had pathological attachment of lateral rectus. Alternating convergent squint was found in 12 children, unilateral in 10. Muscle exposure showed dislocation of lateral rectus attachment--upwards by c. 1.5 mm in 11 children, downwards and obliquely by c. 2 mm in 10 children, in 1 child the upper part of the attachment was shifted forward by 1 mm. During the surgery, in addition to the reduction of squint angle, physiological attachment of the rectus was reconstructed. RESULTS: The operation restored parallel position of the eyes in 22 children, very good vision was obtained in 12 (54%) with alternating convergent squint, significant improvement in 5 (22%) with unilateral convergent squint, and only slight improvement in the remaining 5 (22.7%) with high initial amblyopia and squint angle from +15 degrees to +30 degrees.     

The use of an optical polarization method for the evaluation of oculomotor muscle function in vertical deviation

The state of oculomotor muscles in vertical deviation has been studied by means of polarioptic method. A control group included 62 healthy persons, of them 24 (48 eyes) with orthophoria, 19 (38 eyes) with esophoria and 19 (38 eyes) with exophoria. A group of patients with vertical deviation included 39 (78 eyes) with concomitant convergent squint with a vertical component and 9 children (18 eyes) with concomitant vertical squint without a horizontal component. In patients with vertical squint, the polarioptic method revealed high frequency of functional muscular imbalance and anatomic asymmetry of muscles of both horizontal and vertical action. It is shown that in case of convergent squint with a vertical action, not only the frequency is higher, but to a much greater degree increases the value of anatomic asymmetry in the position of horizontal muscles.     

The Early vs Late Infantile Strabismus Surgery Study: do sources for bias exist in this non-randomised trial?

BACKGROUND—The Early vs Late Infantile Strabismus Surgery Study Group investigates whether early or late surgery is preferable in infantile convergent strabismus, in a non-randomised, prospective, multicentre clinical trial. The current state of the study after end of recruitment is reported here, focusing on the question of possible sources for bias in this non-randomised trial.
METHOD—The prognostic factors were analysed at baseline in order to check for imbalances between the two treatment groups. Reasons for possible differences are discussed.
RESULTS—There is no evidence for clinically relevant inhomogeneities between the two groups concerning the distribution of the three prognostic factors spherical equivalent, degree of amblyopia, and limitation of abduction. The fourth prognostic factor, horizontal angle of squint, differs significantly between the two groups.
CONCLUSION—In the analysis of the final results we may have to account for differences in angle of squint at baseline by its inclusion as a covariate or by stratification.

Keywords: convergent squint; strabismus surgery     

Converging squint in severe hypermetropia (author's transl)]

The valuation of 541 cases of convergent squint occuring together with a hypermetropia of more than +5 dpt showed that, the stronger the hypermetropia was, the higher was the proportion of primary microstrabismus to full-accommodative strabismus convergens. In patients who had hypermetropia of more than +8 D, the proportion of primary microstrabismus was 46%. Here the squint was always one-sided, so a high proportion of amblyopia could be expected. In 10% of the cases there was a spontaneous change from convergent to divergent squint - the angle reduction was up to 23 degrees, and could occur at any age. Factors, which seem to favour the appearence of a consecutive divergence, are: high hypermetropia of more than +8 D, increased ACA-ratio, onesided exclusion and vertical divergence. The measuring of the ACA ratio should be done at all orthoptic examinations.     

Strabogenesis in case of low hypermetropia, in addition a simple comparison test to detect aniseikonia (author's transl)]

Author attempts to explain the rise of infantile convergent squint, when the hypermetropia is less than 3,5 diopter. In such cases the low hypermetropia is relative in the sense of Donders, because a sometimes isometropic aniseikonia prevents the fusion. To examine the aniseikonia he recommands a very simple procedure, the comparison test, carried out joined to the cover test.