Binocularity in comitant strabismus: II. Objective evaluation with visual evoked responses

Campos (1982a) reported on his psychophysical studies on the binocularity of patients with comitant strabismus. With binocular visual field techniques, it was possible to show that patients with small-angle eso- and exotropia exhibit a binocular vision, without suppression of the deviated eye. In the present paper visual electrophysiology is used to evaluate objectively these findings and to provide more insight in the problem. First, the studies on binocularity in normals and strabismics, done by using visual evoked responses (VER) are reviewed. This type of investigation is relatively new and the results of the literature are still conflicting. Then personal results of the authors are reported. It is shown that with VER it is possible to objectively assess the presence of anomalous binocular vision (ABV) sustained by anomalous retinal correspondence (ARC) in small-angle strabismus. In patients with large angle deviations this type of binocularity is absent. A correlation between psychophysical and electrophysiological data is provided. Lastly a simple method is described for differentiating the binocularity of normals from that of Strabismics with ARC. This method is based on the recording of binocular VER with the anteposition in front of the fixing eye of neutral filters of increasing density.     

Binocular visual perception in strabismics studied by means of visual evoked responses

Ten normal subjects and 14 patients with comitant esotropia were examined by means of pattern visual evoked responses (VER) under monocular and binocular viewing conditions. When both eyes were stimulated together a VER summation was noted both in normals and in strabismics with small-angle deviation and anomalous retinal correspondence (ARC). This is considered as an objective proof of binocularity. Patients with large-angle strabismus and/or suppression of the image of the deviated eye did not show summation. The significance of summation and its relationship with binocular vision was analyzed by recording binocular VER in normals in which diplopia was artificially induced and in strabismics who spontaneously exhibited double vision. A simple way for differentiating normals from strabismics by means of VERs is presented, considering that the presence or absence of summation per se does not achieve this result. This method is based on the anteposition in front of the fixing eye of neutral filters of increasing density. Summation disappears in strabismics with much weaker filters than in normals (0.5 versus 1.6 log. unit).     

Untersuchungen über das binokulare Gesichtsfeld Schielender

Sensory adaption, i.e. suppression and the status of retinal correspondence were examined with different methods using a special modification of the phase difference haploscope in 25 cases of eso- and 24 cases of exotropia. Three campimetric techniques were carried out:

1. Haploscopic perimetry with moving and stationary targets (isopter and profile perimetry),
2. suprathreshold haploscopic perimetry with a monocularly presented grid of 60 degrees in diameter (raster scotometry),
3. contemporaneous stimulation with different quality of images for both eyes as far as color, direction of contours and luminance are concerned (‘Anteil’ perimetry).

Size and reproducibility of the suppression scotomas were different with each method. The light sense of the squinting eye for stationary targets (profile perimetry) was not inhibited. However, form perception and localization of the stimulus were uncertain in those areas, were suppression was present with other methods. A slowly moving target revealed a fixation point scotoma in most cases; however, its intensity and size were not reproducible. Stable scotomas ot reproducible size were found with raster scotometry, i.e. presenting a not changing large grid pattern of 60 degrees. Almost in all cases there was inhibition of those retinal areas of the deviated eye, which beared the same visual direction of the fovea of the fixing eye; i.e. around the fixation point no grid pattern was perceived. It was also possible to demonstrate a scotoma in the fixing eye of alternators. Its position in the binocular visual field was based on the visual direction of the fovea of the deviated eye. With raster scotometry the unpatterned luminous field, to which the not examined eye was exposed, was once presented with equal intensity as the bright squares (100 asb), and once with the intensity of the dark lines of the grid presented to the tested eye. No difference was found in the size of the scotomas in both experimental conditions. In most cases of esotropia with anomalous retinal correspondence (ARC) there was a circumscribed fixation point scotoma. On the other hand suppression affected much larger areas and showed a hemianopia-like character in exotropia and ARC. The scotomas were on the side of the not examined eye and extended up to the periphery. No stable inhibition could be determined in squinters with normal retinal correspondence. With the ‘Anteil’ perimetry all patients with ARC split their binocular visual field in two parts of dominance in favour of those retinal areas, which provided the higher functions also under monocular conditions. Therefore using binocular perimetry with the test target visible to both eyes, two peaks of light sensitivity were found in cases with ARC. Therefore, the following order can be set up concerning the likelihood of finding a steady suppression scotoma of one eye: The shift of the visual direction of the deviated eye in cases of ARC, i.e. the angle of anomaly, has not been found to be the same in all retinal points. The scotomatous areas showed mainly smaller angles of anomaly as compared to the not suppressed areas in the binocular visual field. This comparative study proves, that the usual clinical methods (isopter and profile p.erimetry) are not suitable for evaluation of suppression scotomas. On the other hand, with the raster scotometry used in this study it was possible to find and reproduce the areas of suppression very easily. Also the extinction phenomenon (Aulhorn, 1967) can be very impressively demonstrated with this method. Finally, the art of seeing with both eyes in a squinting subject is summarized and the possible neuronal mechanism of the sensory adaption phenomena in strabismus are discussed.     

Accommodative Esotropia Long Range Follow-up

Thirty-nine adult patients treated for typical (refractive) accommodative esotropia in childhood continue to have problems because they have not outgrown their hypermetropia, and the majority have not developed stable binocular vision. Their hypermetropia became maximal (median 5.7 diopters) by age 6, decreased in adolescence, and then stabilized (median 4 diopters). Thirty-eight of the 39 adults wear correcting lenses full-time. Nearly all depend on relaxed accommodation to maintain alignment when they remove their glasses. Ten patients, all of whom received treatment before a constant esotropia developed are essentially orthophoric with glasses and have normal binocular vision. The remainder have small-angle deviations with glasses, 14 with varying degrees of amblyopia and peripheral fusion and 15 with anomalous correspondence and suppression. As adults, only one patient with normal binocular function has required surgery whereas 13 of the patients lacking normal fusion have had surgery for increasing esotropia, postoperative exotropia, or consecutive exotropia.     

Binocular interactions and steady-state VEPs. A study in normal and defective binocular vision (Part II)

Background: Recent evidence indicates that an index of binocular activity may be found in some properties of steady-state visual evoked potentials (VEPs), such as amplitude facilitation and phase shortening. We evaluated binocular interactions with steady-state VEPs in normal subjects as well as in patients with concomitant strabismus and defective binocular vision. Methods: Steady-state (8-Hz) VEPs to counterphased sinusoidal gratings (1.2 c/deg spatial frequency) of low contrast (3.2%) were recorded in 19 esotropic patients and in 18 age-matched controls. Patients had either anomalous retinal correspondence (ARC, n =10) or suppression (n=9) in casual seeing conditions (striated glasses). In all subjects, both binocular and monocular VEPs displayed a major component at twice the stimulation frequency (second harmonic), whose amplitude and phase were measured. A binocular interaction index was obtained by comparing binocular VEPs (BVEPs) with the sum (vectorial) of the two monocular VEPs (SMVEPs). Results: In normal subjects, BVEPs were larger in amplitude than SMVEPs (facilitation), and shortened in latency (phase). On average, both ARC and suppression patients displayed loss in amplitude facilitation and absence of phase shortening. However, 50% of ARC patients showed clear VEP facilitation. In both ARC and suppression patients, the amplitude ratio BVEP/SMVEP was negatively correlated with the amount of the angle of deviation. Conclusion: These results suggest that losses in amplitude facilitation and phase shortening of binocular steady-state VEPs reflect abnormal binocular interactions associated with different forms of sensorial adaptation in concomitant strabismus.     

Part I. Sensorial anomalies in strabimus

Some concepts regarding suppression, anomalous correspondence and amblyopia are revised according to the sensorial findings obtainable from esotropic patients directly in casual seeing (with the aid of the striated glasses test) and by grading a sensorial dissociating effect (with the aid of a bar of optical filters). The following points are emphasized: 1. Suppression appears to be minimal in small angle strabismus where diplopia seems mainly to be avoided by an anomalous correspondence mechanism. On the contrary, suppression is the prevalent mechanism in large angle strabismus. 2. The anomalous correspondence mechanism may lead to a weak type of anomalous binocular vision which is easily interrupted by light optical filters or by dissociating tests. 3. The subjective space of patients with anomalous binocular vision resembles that of normal binocular vision in some aspects. 4. The development of amblyopia is interpreted in the light of these new concepts on suppression and anomalous binocular vision. 5. Postoperatively, anomalous correspondence rapidly re-adapts to the smaller angle deviation and may normalize if the deviation is completely eliminated. This is evident only in casual seeing; for a certain time, dissociating tests reveal the preoperative correspondence status. This behaviour of correspondence in casual seeing has led to attempts at normalizing anomalous correspondence by prism therapy. Newly observed sensotio-motorial obstacles, however, have been found to frequently hamper treatment in casual seeing.     

Predictors of postoperative binocularity in adult strabismus

We evaluated postoperative binocularity in a retrospective study of 111 adult strabismus patients in order to identify the factors which influence the success of surgery for horizontal concomitant strabismus in adults. Selection criteria included minimum age of 15 years at time of surgery, and preoperative fusion impairment with both the Bagolini lens test and synoptophore. Logistic regression analysis was used to correlate patient factors and postoperative binocularity. We found that 52 (65%) of 80 patients with exotropia and 23 (74.2%) of 31 patients with esotropia achieved post operative fusion. Significant predictive factors in exotropia were absence of previous surgery; visual acuity of the deviating eye >0.5; an increase in the spherical equivalent of the deviating eye, and normal retinal correspondence. Significant predictive factors in esotropia were fusion during prism adaptation, absence of infantile esotropia, and an increase in vertical deviation. The majority of adults with exotropia or esotropia can achieve binocularity after surgery for horizontal concomitant strabismus.     

Causes,background, and characteristics of binocular diplopia in the elderly

Purpose

We evaluated the background and characteristics of elderly patients with binocular diplopia including diseases caused by abnormalities in orbital pulleys.

Study design

Retrospective.

Methods

The participants were 236 patients aged 60 years or older who visited Kitasato University Hospital complaining of binocular diplopia. We classified strabismus by types and investigated the causes for each group. We diagnosed orbital pulley disorders using magnetic resonance imaging (MRI). Patients with orbital pulley disorders exhibited esotropia and/or vertical strabismus and did not present with cranial nerve palsy, systemic illness, or ocular injury.

Results

Classification of strabismus types was: exotropia (24.2%); esotropia (25.0%); vertical strabismus (30.1%), combined strabismus (20.8%). There were 50.9% cases of strabismus associated with vertical deviation. The causes of disease in each group were as follows: in the exotropia group, 50.9% convergence insufficiency exotropia, 21.1% basic exotropia; in the esotropia group: 35.6% orbital pulley disorder 33.9% sixth cranial nerve palsy; in the vertical strabismus group: 32.4% forth cranial nerve palsy, 31.0% orbital pulley disorder; in the combined strabismus group: 28.6% orbital pulley disorder, 28.6% forth cranial nerve palsy.

Conclusions

About half of the elderly patients with binocular diplopia exhibited vertical deviation. In addition, binocular diplopia was often caused by orbital pulley disorders. It is the first epidemiological study focusing on orbital pulley disorders diagnosed on the basis of MRI.

     

Management of strabismus with hemianopic visual field defects

Background

Hemianopia and strabismus leads to severe disturbance of visual orientation and diplopia under binocular conditions if the deviated eye has a normal retinal localization.

Subjects and methods

Four cases with homonymous (two) and bitemporal (two) hemianopia and strabismus will be described with respect to binocular visual field and diplopia/confusion. All of them were recommended for strabismus surgery. Preoperatively, prism adaptation test was carried out to analyze functional results and fusional competence. In three of the four cases, strabismus surgery was successfully performed to avoid diplopia/confusion. All three patients revealed normal retinal correspondence. Furthermore, in two cases surgery led to an extension of binocular visual field; in one case with a bitemporal hemianopia and hemifield-slide phenomenon, blurred central vision and reading problems reduced significantly postoperatively. In one patient with anomalous retinal correspondence due to early childhood trauma exotropia led to an extension of the binocular visual field. In this case, strabismus surgery would have been unfavourable.

Results

Case 1 showed a homonymous hemianopia to the left and acquired exotropia of the right eye, leading to binocular diplopia. Case 2 with homonymous hemianopia to the right and exotropia of right eye revealed anomalous retinal correspondence after history of perinatal brain injury, resulting in absence of diplopia and enlargement of visual field to the right. Cases 3 and 4 with bitemporal hemianopia suffered from sensory disturbances caused by additional acquired strabismus. The exodeviation of the right eye in case 3 led to a restriction of binocular visual field with overlap of the nasal parts causing diplopia, whereas the esodeviation of case 4 resulted in a “gap” between the nasal parts (blind area).

Conclusion

Depending on the extent of visual field defects and on retinal correspondence, functional consequences for binocular vision and binocular visual field should be considered prior to surgery. In normal retinal correspondence, strabismus surgery will be indicated in most cases because of diplopia. However, surgery might result in a reduction of binocular visual field. Preoperatively, it is important to map monocular and binocular visual fields, to examine retinal correspondence, and to undertake prism adaptation test to imitate the postoperative functional result and risk of double vision.     

斜视矫正术对共同性斜视患者双眼视觉功能的影响

目的 探讨共同性斜视患者接受斜视矫正手术前后双眼视觉功能的改变及其影响因素。设计 回顾性病例系列。研究对象 北京同仁医院2013年12月至2014年8月进行斜视矫正术的共同性斜视患者191例。方法 将患者按斜视类型分为共同性内斜视组、恒定性外斜视组和间歇性外斜视组;按手术时年龄分为≤9岁组和＞9岁组。观察术前、术后1、3个月双眼视觉功能。主要指标 同视机双眼视觉三级功能及近立体视功能。结果 191例患者中,术前分别有26.7%、19.4%、11.0%及41.9%的患者具备同视机Ⅰ、Ⅱ、Ⅲ级及近立体视功能,术后1个月分别提高至90.1%、64.4%、33.0%及57.1%,术后3个月分别提高至94.8%、79.1%、37.7%及63.9%,与术前相比均有统计学差异（P均＜0.001）。术前,间歇性外斜视组38.1%、29.5%及72.4%的患者具备同视机Ⅰ、Ⅱ级及近立体视功能,高于另两组（P＜0.01）。术后3个月,间歇性外斜视组93.3%、48.6%及87.6%的患者具备同视机Ⅱ、Ⅲ级及近立体视功能,高于另两组（P均＜0.05）;恒定性外斜视组55.8%的患者具备近立体视功能,共同性内斜视组为14.0%（P＜0.001）。＞9岁组,术前28.1%、21.9%、14.6%及31.3%的患者具备同视机Ⅰ、Ⅱ、Ⅲ级及近立体视功能,术后3个月分别提高至93.8%、75.0%、37.5%及58.3%,与术前相比均有统计学差异（P＜0.01）。结论 斜视矫正术有助于共同性斜视患者双眼视觉功能的改善;间歇性外斜视患者术前术后双眼视觉功能优于其他类型斜视;大龄斜视患者术后也可能获得双眼视觉功能的改善。     

斜视手术前后双眼视觉的临床研究

目的探讨斜视对双眼视觉的影响及不同双眼视检查方法的评价。方法89例共同性斜视分为间歇性外斜、恒定性外斜及恒定性内斜3组。定量测量斜视度；检查双眼视觉状态及视网膜对应情况；测定远近立体视锐度。并观察斜视手术前及手术后1周、1月的斜视度、双眼视觉状态及远、近立体视锐度变化。结果3组术后双眼视功能较术前均有明显改善（P〈0．05），术后1周与1月双眼视功能的差异无统计学意义（P〉0．05）；恒定性斜视术后立体视恢复好于间歇性外斜视，且近立体视恢复好于表视；立体视检查非随机点画片（Titmus与Optec3500）与随机点画片（TNO）检查结果的差异有统计学意义（P〈0．05）；线状镜较Worth四点检测阳性率高；大于9岁患者术后双眼视觉较术前增加32％。结论斜视手术是恢复、重建双眼视觉的有效方法，不同检测方法结果不一致，需综合考虑。     

低龄儿童不同类型斜视手术远期疗效

目的 分析早期手术治疗儿童斜视的远期疗效,探讨低龄儿童不同类型斜视的手术时机和设计.方法 手术治疗397例3岁以下斜视患儿,手术后随访6～144个月,观察术后眼位、双眼单视功能及二次手术情况.结果 (1)外斜视组、垂直分离性斜视(DVD)组远期正位率分别为78.1%、68.4%,低于术后正位率,P＜0.05;内斜视组、上斜肌麻痹(SOP)、A-V综合征及特殊类型斜视远期正位率与术后正位率无差异,P＞0.05.(2)各组远期立体视＜800"的比率均高于术前,P＜0.05.(3)发病年龄早、伴有垂直斜视及术后一周欠矫或过矫是影响内、外斜视术后远期效果的主要因素,P＜0.05;手术年龄在24个月内与25～36个月远期眼位无差别,P＞0.05.结论 (1)内斜视,SOP及A-V综合征,3岁前手术远期眼位较满意并有利于立体视功能.(2)内、外斜视近期应适度欠矫和过矫,以+10△之内为宜.垂直斜视诊断明确者尽量一次手术,特殊类型斜视宜选分次手术.

Abstract：

Objective To analyze the long-term outcome of early surgical treatment,to review the operation design and timing of different types of strabismus in young children.Methods A total of 397 strabismus cases received operation under 3 years old,postoperative follow-up 6 to144 months,position of eye,binocular vision and second operation were reviewed.Results (1)The long term orthophoria rate ofexotropia and DVD was 78.1%,68.4%,lower than postoperative,P ＜0.05; The orthophoria rate of esotropia,SOP,A-V syndrome and special strabismus had no significant difference at long-term follow-up,P ＞0.05.(2)The ratio of ＜800 " of binocular vision of different group were higher than the preoperative at long-term follow-up,P ＜0.05.(3)The occurrence age early,accompanied by vertical strabismus and postoperative position of eye more or less proper was primary factor for position of eye at long-term follow-up,P ＜0.05.Conclusions (1)For esotropia,SOP and A-V syndrome,operation under 3 years old contribute to orthophoria and binocular vision at long-term follow-up.(2)The operation design of esotropia and exotropia should be moderate more or less proper +10 △.The vertical strabismus should design for once as possible,specific strabismus choose divide into two period operations.     

Distance judgement in comitant strabismus with anomalous retinal correspondence

Judgement of distances was evaluated in 19 patients with comitant esotropia and without appreciable stereopsis. In nine patients anomalous retinal correspondence (ARC) was present at Bagolini's striated glasses. In the remaining patients there was suppression with the same test. Distance judgement of strabismics with ARC does not differ statistically from that one of normals. Significantly different results were found in strabismics with suppression. It is concluded that ARC is not only an anti-diplopic mechanism, but provides the patients with useful clues in their daily life.     

Use of botulinum toxin in small-angle heterotropia and decompensating heterophoria: a review of the literature

Botulinum toxin has been used extensively in strabismus management. However, less is published regarding its use in small-angled manifest deviations or decompensating heterophorias, where an alternative to surgery is required. The aim of this review is to look at the use and effectiveness of botulinum toxin in managing small-angled manifest deviations, both constant and intermittent, and decompensating heterophorias. These types of strabismus can prove difficult to manage, as the angle present is often too small for surgery to be advised, but it may still cause a cosmetic or symptom-producing problem. A search of the English speaking literature was undertaken using Medline facilities as well as a limited manual search of non-Medline journals and transactions. A brief overview is provided for mechanisms of action, complications and dose effects, and diagnostic and therapeutic uses of botulinum toxin. The main reported complications are those of ptosis, induced vertical deviation and subconjunctival haemorrhage. The higher the dose, the greater the risk of complications. In small-angle strabismus, botulinum toxin is reported as particularly useful in cases of acquired and acute-onset esotropia in aiding maintenance of binocular vision. It is useful for additional management of surgically under- or over-corrected esotropia, particularly for those with potential for binocular vision. Less effect is reported in primary exotropia versus primary esotropia. It is the management of choice for consecutive exotropia, particularly when patients have had previous multiple surgery and where there is a risk for postoperative diplopia. Botulinum toxin has a specific role in decompensated heterophoria, allowing the visual axes a chance to 'lock on' and subsequently maintain binocular vision. Successful outcomes are reported after 1-2 injections only but the results are best in cases of heterophoria with little near-distance angle disparity.     

Preliminary report: Fixation behavior and reading strategies in dyslexic and normally reading children as assessed by the scanning laser ophthalmoscope

Abstract

Introduction: One goal of pre-operative sensorimotor testing is to determine fusion potential. Potential for recovery of binocularity following surgical repair of strabismus is inversely correlated to duration of misalignment. The purpose of this study was to determine binocular vision outcomes in long-standing, large-angle, constant exotropia, when the pre-operative sensorimotor exam predicts poor sensory outcome.

Methods: Patients with constant exotropia >35Δ, present for ≥20 years, and scheduled to undergo strabismus surgery were recruited. Subjects were sorted into 3 groups based on pre-operative sensorimotor results. Group A had evidence of fusion pre-operatively, Group B demonstrated suppression on all tests, and Group C demonstrated paradoxical diplopia on at least one test.

Results: Twenty patients were included: 11 in Group A, 5 in Group B, and 4 in Group C. Binocular vision was regained following surgery by 100% in Group A, 80% in Group B, and 50% in group C.

Conclusion: Surgical realignment leads to improvements in binocular vision in most patients, even in the case of very long-standing, large, constant deviations. The presence of paradoxical diplopia or dense suppression pre-operatively does not preclude a good sensory outcome.     

Long-term results after strabismus surgery

The results of surgery after 4 years' or more postoperative follow-up have been evaluated in a total of 1031 cases (575 esotropia, 456 exotropia). There is a difference in the angle of strabismus 1 month after surgery and 4 years after surgery. Based on these findings, the results of strabismus surgery must be evaluated after a sufficient amount of time has passed. The angle of strabismus to be aimed at, to provide best binocular vision and patient satisfaction, should be in the range of –2 +7 degree for esotropia and +2 –10 degree for exotropia, regardless of the patient's age at surgery.Dedicated to Dr. G.K. von Noorden on the occasion of his 60th birthday     

间歇性外斜视术后远期疗效及其影响因素分析

目的 探讨间歇性外斜视手术治疗的疗效和术后部分患者斜视回退的可能原因.方法 对120例患者的术后一天眼位、术前有无双眼同时视功能、发病年龄、手术年龄、斜视类型与远期眼位的关系进行分析,寻找影响斜视回退的可能因素.结果 120例随访平均25.34个月(12～50个月).眼位:正位90例(75%),外斜29例(24.17%),内斜1例(0.83%);术后远期眼位只与术后一天眼位和术前有无双眼同时视功能有关,而与发病年龄、手术年龄、斜视类型均无关.结论 间歇性外斜视术后远期眼位与术后一天眼位和术前有无双眼同时视功能有明显相关性,术后一天过矫和术前有双眼同时视功能者可以获得较好的远期眼位.     

共同性斜视再手术原因分析

目的探讨共同性斜视再次手术原因及手术方式。方法对近5年来在我院住院手术的1329例共同性斜视患者进行回顾性分析,其中42例因各种原因再次手术。结果 22例患者因手术欠矫或术后眼位回退再次手术,其中内斜视4例,外斜视18例2;0例因过矫再次手术,其中内斜视12例,外斜视8例。结论共同性斜视患者双眼视功能是否正常、是否伴有弱视、术前斜视度测定是否准确、斜视类型、手术者临床经验等都是斜视再次手术影响因素。     

Some principles in surgical treatment of strabismus

Taking into consideration the age of the patient, the strabismus surgery targets different things. Thus, for infants, the goal of the surgical intervention for congenital esotropia, is to prevent the occurrence of amblyopia and binocular vision dysfunctions (ARC, suppression). In preschool children, we operate aiming the recovery of the binocular vision, while in children over ten years old, the surgery is done only for esthetic reasons. On the other hand, in adults, the strabismus surgery has two aspects: for esthetic reasons in monocular strabismus with amblyopia, or for diplopia treatment in strabismus of traumatic or neurological cause. To get the best results, the surgical intervention has to respect several rules, which differ with patient's age. This presentation will discuss several surgical procedures: for congenital esotropia (including its advantages and drawbacks), for preschool children strabismus and also for strabismus in adults. We will also review the surgical treatment for Duane syndrome, Ciancia syndrome and superior oblique muscle palsy.