Bruce Wick

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.

A prospective study of treatment of accommodative insufficiency.

Prepresbyopic patients with reduced accommodative amplitude (accommodative insufficiency) are commonly seen in optometric practice. Treatments include accommodative therapy and plus reading lenses. We did a prospective study of the effects of vision therapy and plus reading lenses on 15 patients (mean age 21.87 ± 9.66 years) with accommodative insufficiency; presumed etiologies included head trauma (6 patients), thyroid disease (3 patients), seizures (1 patient), toxoplasmosis (1 patient), and idiopathic causes (4 patients). A 7-question scaled response pre- and posttreatment questionnaire assessed symptoms of two groups, vision therapy (idiopathic only) and progressive addition lenses (all patients). No idiopathic patient improved after 3 weeks of accommodative therapy. Progressive lenses with a near addition of +1.00 or +1.25 were then prescribed. Questionnaire results, which indicate that near additions provided more relief of symptoms than vision therapy for treatment of accommodation insufficiency, underscore the need for careful examination of prepresbyopic patients to determine those who would benefit from a near addition.

The influence of refractive correction upon disorders of vergence and accommodation

Clinical care routinely includes prescription of lenses that compensate for the distance refractive error. Indeed, refractive correction is so commonly prescribed that we often neglect its potential effects on disorders of binocular vision. We report improvement of binocular function that resulted 1 or more months after prescription of an initial spectacle correction for 143 nonstrabismic patients who had a refractive error and either a vergence anomaly (28%), an accommodative anomaly (8%), or both (64%). Refractive correction was estimated objectively with an autorefractor and subjectively refined without cycloplegia. Most corrections were low to moderate in power, essentially following Orinda Study guidelines. Recovery of normal vergence and accommodative function varied according to refractive error type (79% of hyperopic astigmats recovered; 20% of myopes recovered), direction of astigmatic axes (67% recovered who had against-the-rule; 45% with with-the-rule recovered), age (63% below age 12 years recovered; 41% older than age 13 years recovered), and vergence anomaly (67% of patients with fusional vergence dysfunction recovered; 38% of those with basic exophoria recovered). These results suggest that improvement in acuity is not the only reason for prescription of a refractive correction—prescription of even small corrections should be considered as these can dramatically improve vergence and accommodative function for many patients.

Relation among accommodative facility, lag, and amplitude in elementary school children

ABSTRACT Normative data for accommodative lag, facility, and amplitude of children have been presented in the literature for each of the parameters separately. This paper delineates the relation among accommodative amplitude, lag, and flexibility for grade school children. Approximately 200 children were screened. Those who wore corrective lenses, had uncorrected acuity worse than 6/9 (20/30) in either eye, had strabismus, had a refractive error outside the range from 0.00 to +0.75 D; or astigmatism greater than 0.50 D were excluded from the study. Of the 123 who remained, 53% had a deficit in accommodative facility, 26% had a deficit in lag, and 25% had a deficit in amplitude from that which would be expected from their age. Sixteen percent had deficits in both facility and lag. Eighteen percent had deficits in both amplitude and lag. Twenty‐four percent had deficits in both facility and amplitude. Only 4% had deficits in all three of the accommodative functions considered—amplitude, lag, and facility. Clinically, these results indicate that when a patients accommodative dysfunction is examined all facets of accommodation—lag, facility, and amplitude—need to be evaluated.

Vergence facility : Establishing clinical utility

Purpose. Vergence facility testing attempts to assess the ability of the fusional vergence system to respond rapidly and accurately to changing vergence demands over time [defined as the number of cycles per minute (cpm) that a stimulus can be fused through, alternating base-in (Bl) and base-out (BO) prisms]. Decisions to use vergence facility as a clinical test are hampered by a lack of systematically gathered normative data. Methods. Twenty symptomatic and 20 control subjects with ages between 18 to 35 years of either sex and any race were pooled, based on vision-symptom level determined by a self-report questionnaire. Inclusion/exclusion criteria included vision correctable to 6/6 (20/20) Snellen acuity or better in each eye and normal phorias. Vergence facility response was tested over a 1-min period, using 16 combinations of BI/BO flip prisms at 4.0 and 0.4 m, based on Morgans norms and pilot data. Results. Horizontal vergence facility responses were not the same among those with and without symptoms, and not all magnitudes of BI/BO flip prisms produced the same response difference. A single flip prism, 3 Δ BI/12 Δ BO, was found to differentiate optimally between groups at distance and near. Repeatability of test results (with the 3 Δ BI/12 Δ BO prism) was poor at distance and good at near. Conclusions. In addition to providing valuable normative data, this study indicates that the vergence system nearly resets its “zero point” at any distance and sheds further light on the results of dynamic convergence and divergence stimulation on the accommodative-vergence system. From a clinical standpoint, the results improve the diagnosis of binocular vision abnormalities. The recommended near vergence facility test is easily implemented, using a commonly available flip prism (3 Δ BI/12 Δ BO) and having a clinical failure criterion that is easily recalled (15 cpm, sum of the Bl and BO magnitudes).

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.

Clinical factors in proximal vergence

ABSTRACT Using forced vergence fixation disparity curves, proximal vergence was analyzed in two asymptomatic patient samples; 20 young adults (average age 25.2 ± 4.71 years) and 20 presbyopes (average age 61.6 ± 7.8 years). Total proximal vergence was significantly larger when measured under binocular (closed loop) conditions than monocular (open loop) conditions for pre‐presbyopes (binocular 10.51&Dgr; ± 4.7 vs. 6.4&Dgr; ± 3.84 monocular) and presbyopes (binocular 11.59&Dgr; ± 3.13 vs. 4.71&Dgr; ± 2.15 monocular). Associated proximal vergence was shown to predict associated phoria magnitude in presbyopes and in pre‐presbyopes when vergence adaptation and convergence accommodation (CA/C) interactions with accommodative convergence (AC/A) are included. A vergence/accommodation model is presented which includes influences of proximal vergence. Clinical implications of the findings relating to diagnosis and therapy are discussed.

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 authors stated criteria for success, the following pooled success rates were revealed: overminus 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.

Vision training for presbyopic nonstrabismic patients.

Home vision training was prescribed for 161 presbyopic patients (ages 45 to 89) who had vision-related symptoms and convergence insufficiency or visual skills deficiencies. Most patients required 10 weeks or less of treatment, the longest treatment period being 15 weeks. Elimination of the symptoms and improved responses on certain optometric tests was achieved by 92% of the patients. Evaluation 3 months after therapy indicated that 77 patients required additional training, the older patients requiring it more often, to retain the initial improvement.

A case-comparison of intermittent exotropia and quality of life measurements

A Vision Quality of Life Questionnaire that combines the SF-20 and a Vision Quality Scale developed by the authors was pilot tested in a case-comparison of extreme groups, patients with intermittent exotropia (IXT) and those with no vision problems (Non-IXT), at the University of Houston (UH) Optometry Clinic. The purposes of the study were to measure the internal consistency reliability and examine the validity-related evidence of vision function associated with the instrument. The pilot study involved mailing the instrument to 52 patients in each group (IXT and Non-IXT patients). IXT patients were then frequency-matched by age and separately by sex, to control for confounding variables, to Non-IXT group patients. The Cronbachs Alpha internal consistency reliability of both scales was acceptable at >0.70 for both the IXT and Non-IXT groups. The Wilcoxon signed ranks test was used to determine validity-related evidence. The differences between groups on the SF-20 (p=0.0276) and Vision Function Scale (VFS) (p=0.0385) confirm that the scales discriminate between IXT and Non-IXT populations. Two conclusions can be drawn from the pretesting and pilot testing of the SF-20 and the VFS: (1) both have acceptable internal consistency reliability scores, and (2) both show validity-related evidence that they can discriminate vision function between IXT and Non-IXT patient populations.