Report of the section on binocular vision and perception at the American Academy of Optometry.
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Humans↗
Biomedical subjects
B Wick
Publications and source records attributed to B Wick.
Arnold-Chiari malformation.
Arnold-Chiari malformation is a congenital malformation of the skull near the foramen magnum in which the cerebellum and the medulla are caudally displaced. This herniation of the brainstem causes down-beat nystagmus and oscillopsia, the most commonly presenting sign and symptom, respectively. Differential diagnoses for the Arnold-Chiari malformation include, but are not limited to, demyelinating disease, tumor, and vascular disorders. Symptoms will generally worsen with time and may even be brought on during exercise or valsalva maneuvers. A correct diagnosis can lead to timely surgical intervention which can improve the quality of eye movements. Treatment generally involves the surgical decompression of the surrounding spinal tissue.
Adolescent↗
Treatment options in intermittent exotropia: a critical appraisal.
Clinical opinions regarding treatment of intermittent exotropia (IXT) vary widely and there is controversy as to which treatment modality is most successful. This paper reviews the clinical literature related to five different treatment modalities used for IXT: overminus lens therapy, prism therapy, occlusion therapy, extraocular muscle surgery, and orthoptic vision therapy. Based upon review of 59 studies of treatment of IXT, and using each author's stated criteria for success, the following pooled success rates were revealed: over-minus lens therapy (N = 215), 28%; prism therapy (N = 201), 28%; occlusion therapy (N = 170), 37%; extraocular muscle surgery (N = 2530), 46%; and orthoptic vision therapy (N = 740), 59%. Success rates for IXT surgery differed depending upon whether a functional (43%) or cosmetic (61%) criterion was used to evaluate treatment success. These pooled success rates must be viewed carefully because nearly all the studies suffer from serious scientific flaws such as small sample sizes, selection bias, inadequately defined treatments and success criteria, absence of statistical analysis, and results reported in a manner that makes interpretation difficult. These problems indicate the need for a careful, circumscribed, and well controlled clinical trial to study the efficacy of different treatment modalities in remediating IXT.
Contact Lenses↗
Binocular vision section.
The participants at the 1991 Meetings of the Section on Binocular Vision and Perception presented a substantial amount of valuable theoretical and clinical information. There was considerable and valuable interaction between the audience and panel, especially after the symposium concerned with new techniques and how to use them. The exchange of specialized knowledge through discussions at symposiums such as these represents one of the best features of Academy meetings. These symposiums reemphasize and remind us of the expertise of our Academy members in management of binocular vision anomalies.
Dyslexia↗
Re-evaluation of the four prism diopter base-out test.
The four prism diopter base-out (4 delta BO) test is often recommended for use as an objective assessment of binocular visual function in patients with suspected microstrabismus or central suppression; however, many aspects of the test are unknown. In this series of investigations we evaluated: (1) inter-observer agreement between 2 examiners, using 15 subjects; (2) types of eye movements made and prevalence of the various response types demonstrated in 212 children and 116 adults with normal binocular vision, and 10 children and 4 adults with abnormal binocular vision; and (3) repeatability of test results for 22 subjects evaluated on two separate occasions. In addition, using an SRI Eye-tracker, we documented the eye movements made while testing 2 subjects with small angle strabismus and 4 subjects with normal binocular vision. We found the following results: (1) inter-observer agreement is high; (2) both children and adults exhibit many atypical responses, whether or not they have normal binocular vision; (3) diplopia awareness does not differentiate between subjects with normal and abnormal binocular vision; and (4) 4 delta BO test results are not repeatable. Due to frequent atypical and variable responses in subjects with or without normal binocular vision, we suggest the examiner use caution when making a diagnosis based solely on the 4 delta BO test.
Adult↗
Anisometropic amblyopia: is the patient ever too old to treat?
Amblyopia is an example of abnormal visual development that is clinically defined as a reduction of best corrected Snellen acuity to less than 6/9 (20/30) in one eye or a two-line difference between the two eyes, with no visible signs of eye disease. We describe a sequential management program for anisometropic amblyopia that consists of four steps: (1) the full refractive correction, (2) added lenses or prism when needed to improve alignment of the visual axes, (3) 2 to 5 h/day of direct occlusion, and (4) active vision therapy to develop monocular acuity and improve binocular visual function. We examined records of 19 patients over 6 years of age who had been treated using this sequential management philosophy. After 15.2 (+/- 7.7) weeks of treatment the Amblyopia Success Index (ASI) documented an average improvement in visual acuity of 92.1% +/- 8.1 with a range from a low of 75% by a 49-year-old patient to a maximum of 100% achieved by 42.1% of the patients (8 of 19). Patients who had completed therapy 1 or more years ago (N = 4) maintained their acuity improvement. From these results we conclude that following a sequential management plan for treatment of anisometropic amblyopia can yield substantial long-lasting improvement in visual acuity and binocular function for patients of any age.
Adolescent↗
Rapid- and slow-velocity vergence eye movements.
Previously we have measured rapid-velocity vergence responses to targets at different distances that provided no disparity or accommodative stimulation. To evaluate the possibility that this rapid-velocity vergence occurs during saccades, the latencies of eye movement between two long dim luminous rods were compared under two conditions. Rapid-velocity vergence with an average latency of approximately 300 ms was elicited when subjects alternately viewed horizontal rods at distances of 38 and 78 cm, and with a vertical separation of 5.2 degrees. Horizontal saccades with a comparable latency were measured when the rods were equidistant and oriented vertically. The correlation between the mean latencies of vergence and saccadic movements was 0.97, suggesting that the two movements occurred together. In a second experiment vergence responses were measured when the subject looked between a bright vertical line on a screen at 76 cm and a second pair of lines (vertically displaced between 0.15 degrees and 3 degrees) with crossed disparity to simulate a target at 38 cm. Slow-velocity vergence often occurred alone when the vertical separation between targets was small; rapid-velocity vergence intruded when the separation between the targets was larger. The results can be accounted for if proximity and disparity stimulation act through a single vergence controller, the output of which produces slow- or rapid-velocity vergence depending upon whether the saccadic system is concurrently active.
Adult↗
Stability of retinal correspondence in normal binocular vision.
Although many studies have suggested absolute stability of retinal correspondence, perhaps more have concluded that the correspondence of adult subjects with normal binocular vision is capable of small variation, particularly with strong sustained demands upon vergence, in order for binocular vision to be maintained. In this comprehensive review of the literature, the reasons for these differences are critically discussed and areas still to be resolved are pointed out.
Depth Perception↗
Dynamic demonstration of proximal vergence and proximal accommodation.
The complex interactions between accommodation and vergence have been described by dual interactive models which include influences of convergence accommodation and accommodative vergence. Using an SRI Eyetracker, we investigated changes in vergence and accommodation stimulated while looking through prisms or lenses, and while looking at real targets located at different distances. Our results suggest that both proximal accommodation and proximal vergence are stimulated when looking from a distant to a near real target. We suggest that models of convergence and accommodation interactions include proximal accommodation and proximal vergence before the crosslinks.
Accommodation, Ocular↗
Diagnostic occlusion and clinical management of latent hyperphoria.
Occasionally in patients who have symptoms suggestive of a vertical heterophoria no deviation is found, even on careful examination. Six days of occlusion have been recommended for uncovering such "latent" vertical deviations. We investigated prolonged monocular occlusion (Part I) and found that vertical deviations of varying amounts manifested on symptomatic and asymptomatic subjects. Thus, results of prolonged occlusion can be difficult to interpret. Nonadaptive vertical vergence systems have been implicated in development of symptoms. Therefore, it may be that diagnostic monocular occlusion is not appropriate unless patients have symptoms of vertical imbalance. We used (24 h) occlusion and associated phoria measurements (Part II) to determine vertical prism prescriptions which eliminated symptoms of seven symptomatic patients who did not show significant vertical heterophoria on routine clinical testing. We present data and case reports which elucidate the efficacy of this procedure.
Adolescent↗
Convergence accommodation: laboratory and clinical evaluation.
The accommodation stimulated by convergence, CA/C, was measured under laboratory and clinical conditions. There was a small nonlinearity to the CA/C ratios measured under laboratory conditions for three of six subjects. We found that convergence accommodation decreases with decreasing accommodative amplitude but not as rapidly as has been reported in the literature. Our results suggest that convergence accommodation can contribute substantially to the near accommodative response for many patients.
Accommodation, Ocular↗
Stability of retinal correspondence during divergence: evaluation with afterimages and Haidinger brushes.
Retinal correspondence has been described as invariant during normal binocular vision. However, there is substantial evidence that casts doubt on this interpretation and implies that retinal correspondence varies under certain conditions. This article reports the results of two experiments that appraise the stability of correspondence during fusional vergence in persons with normal binocular vision. In the first experiment, afterimages stimulated vertically corresponding retinal meridians prior to divergence. Three of six subjects gave data that indicated a change in the afterimage alignment significantly different from chance. The second experiment determined corresponding retinal areas with Haidinger's brushes. When divergence was maximally maintained, all six subjects who could appreciate the low-contrast Haidinger's brushes on the randomdot background saw two brushes while stereopsis and fusion remained present. Increases in plus lens power increased estimated brush separation.
Afterimage↗
Magnitude and velocity of proximal vergence.
Until recently proximal vergence was considered to play only a minor role in the eye alignment changes that occur when looking between distant and near targets. We measured the magnitude and velocity of proximal vergence using infrared limbal sensing to record vergence responses between two untextured luminous horizontal rods which lacked disparity and accommodative cues. The magnitude of proximal vergence responses averaged 3.9 degrees for convergence and 3.8 degrees for divergence, about 70% of the total vergence "demand." Peak velocities for proximal convergence and divergence averaged 69 and 53 deg/sec, substantially faster than the velocities of comparably sized disparity or accommodative vergence responses. Its rapid velocity makes proximal vergence well suited to initiate the eye alignment changes between distant and near targets.
Accommodation, Ocular↗
Binocular vision complications after radial keratotomy.
Radial keratotomy (RK), a popular procedure for reducing myopia, does not always have a successful outcome. Of the adverse effects reported in the literature, there have been few reports of undesirable disturbances of binocular vision. Four representative cases are reviewed which presented clinically with varying binocular problems induced by RK. The treatment considerations and final solutions for each are discussed. In the presence of RK-induced anisometropia, aniseikonia can be a particularly debilitating binocular vision problem for some patients.
Adult↗
Lens-induced fixation disparity curves.
Change in fixation disparity was measured as lens sphere power was changed at distance and near on a young adult population. The results were graphed to yield a lens-induced fixation disparity curve. The lens curves found were grouped into four basic types (A through D). Two types (A and B) had increasing eso fixation disparity with increasing minus lens power. Type C had little change in fixation disparity with any change in lens power, whereas type D had an initial increase and then no further change with increasing minus power. In addition, approximately 74% of the 38-subject sample had different curve types at distance and near. Possible clinical uses of the lens-induced fixation disparity curve include the prescribing of near additions for pre-presbyopes based on measures of the binocular vergence response to various lens sphere combinations.
Accommodation, Ocular↗
The Hirschberg test: a double-masked clinical evaluation.
Though the Hirschberg test has been used for over a 100 years, several different formulas are still being recommended and used clinically to determine the amount of a given ocular deviation. The purpose of this study was to obtain a double-masked clinical evaluation of the Hirschberg test. Several strabismic patients were evaluated by one investigator using the alternate cover test and by another investigator using a photographic Hirschberg procedure in a double-masked procedure. It was determined that the Hirschberg test can be used for strabismic patients of all ages and that the most appropriate formula to use is 1 mm = 22 delta.
Clinical Trials as Topic↗
Analysis of binocular visual function using tests made under binocular conditions.
Accommodation and vergence have a complex relation which occasionally breaks down, resulting in a loss of visual efficiency along with symptoms of discomfort associated with use of the eyes. Studies of accommodation/vergence interactions and tonic vergence disorders indicate that, using classical analysis techniques, separate methods are frequently necessary to determine whether existing binocular deficiencies are causing reported symptoms. The problem with current systems of binocular visual function analysis is that the vergence error which exists under binocular conditions is often not the same as that which is measured under monocular conditions. A rationale for, and technique of, analyzing binocular function using results of tests made under binocular conditions is described. This analysis incorporates the concepts of CA/C, proximal vergence (PV), and fixation disparity along with several accommodative measures (facility, lag, sustaining ability, and accuracy). By identifying relevant binocular components and the interrelations, the clinician should be better able to assess the contribution of each and examine which may be modified most easily by vision therapy, lenses, and/or prism intervention.
Accommodation, Ocular↗
Management of anomalous correspondence: efficacy of therapy.
The last paper to review thoroughly the success of treatment for esotropia with anomalous correspondence was published by Flom in 1963. In reviewing the literature of that era, which included surgical intervention, Flom found documented cures in only 11 of 262 esotropic patients with anomalous correspondence--a cure rate of less than 5%. We evaluated recent reported success rates for treatment and present an estimate of the prognosis for successful binocular re-education of patients with esotropia and anomalous correspondence. Based on current therapy techniques reported in the literature, with careful aggressive therapy, 50% of esotropic patients with anomalous correspondence should be expected to achieve binocular vision provided sufficient time (up to 12 months) can be devoted to binocular re-education.
Biofeedback, Psychology↗