Persistent diplopia associated with strabismus surgery.

The primary therapeutic goal for patients with binocular vision problems is comfortable, single, clear, normal binocular vision at all distances and directions of gaze. Strabismus surgery is frequently used to assist in achieving this therapeutic goal. Strabismus surgery is also used for those patients who cannot achieve single normal binocular vision but who have a cosmetically noticeable ocular deviation. However, one of the complications of cosmetic strabismus surgery is persistent diplopia. This possibility must be considered seriously before any cosmetic strabismus surgery is performed. The purpose of this paper is to present a case report of a patient who had diplopia after cosmetic strabismus surgery to emphasize the need for careful consideration of the possibility of persistent diplopia after cosmetic strabismus surgery and how to avoid it.

Extraocularmotor dysfunction associated with tumors.

Intracranial and extracranial tumors can be the cause of extraocularmotor dysfunction. In approximately 19% of reported cases, paralysis of the third, fourth, or sixth cranial nerves is due to neoplastic growth; the sixth nerve is the most commonly affected. Tumors can produce extraocular muscle dysfunction by directly affecting the extraocular muscle; directly affecting the third, fourth, or sixth cranial nerves; directly affecting the supranuclear extraocular movement areas; indirectly affecting any of the above by metastasis from a tumor in another part of the body; and indirectly affecting the third, fourth, or sixth cranial nerves or their nuclei or the supranuclear extraocular movement areas through an increase in intracranial pressure. The ocular signs and symptoms of disease vary based on the mechanism involved.

Changes in retinal correspondence after changes in ocular alignment.

We studied the changes in retinal correspondence for 32 constant strabismic patients whose ocular alignment was altered either surgically or spontaneously over a period of time. Patients having normal retinal correspondence (N = 10) generally maintained normal correspondence after the change in ocular alignment. Patients with anomalous retinal correspondence (N = 20) behaved differently. Thirteen of these patients maintained anomalous correspondence and seven patients developed normal correspondence after the change in ocular alignment. For the patients who developed normal correspondence, the direction of the strabismus also changed. We conclude that normalization of retinal correspondence is more likely to occur in strabismic deviations that are overcorrected.

The Hirschberg test: correlation with corneal radius and axial length.

The results of this study indicate that the axial length is not strongly associated with the Hirschberg formula, and therefore the axial length does not have to be considered when measuring an ocular deviation with the Hirschberg test. This study does demonstrate an association between the radius of curvature of the cornea and the Hirschberg formula. For patients with keratometer readings below 46 D, the use of the standard Hirschberg formula, 1 mm = 22 delta, is appropriate. For patients with keratometer readings greater than 46 D, and with deviations greater than about 30 delta, the use of the Hirschberg formula, 1 mm = 27 delta, is more appropriate. When performing the Hirschberg test on infants up to about 2 months of age, the use of the higher Hirschberg formula would probably be more appropriate because this age group often has higher keratometer readings.

Effect of cyclodeviations on the axis of astigmatism (for patients with superior oblique paresis).

Cyclodeviations may interfere with fusional ability and may also affect the refractive status. If a cyclodeviation is present, the axis of astigmatism determined under monocular viewing conditions will be different from that determined under binocular viewing conditions. The change in the axis should correlate with the amount and direction of the cyclodeviation. We measured the refractive status under monocular and binocular viewing conditions of patients with cyclodeviation of 3 degrees or more and astigmatism of 1.00 D or more. All patients had superior oblique paresis. We then compared the change in the axis of astigmatism to the cyclodeviation measured with the double Maddox rod test. The average change in the axis of astigmatism was 5.0 degrees and the average cyclodeviation was 5.2 degrees. We recommend that all patients with 3 degrees or more of cyclodeviation, 1.00 D or more of astigmatism, and capable of fusion should have their refractive status determined under binocular viewing conditions.

Clinical characteristics of anomalous correspondence.

The correspondence status of 68 constant, early-age onset strabismics was evaluated with three common clinical tests to determine the prevalence of anomalous retinal correspondence (ARC) and which clinical features of the strabismus were most highly associated with the ARC. Ninety-six per cent, 71%, and 51% of the patients manifested ARC with the striated lens test, the synoptophore, and the afterimage test, respectively. The clinical features of the strabismus that were correlated, although weakly, with the diagnosis of ARC were: (1) the magnitude of the deviation at near for the striated lens test; (2) the age of the patient at the time of testing and the laterality of the deviation on the synoptophore; and (3) the age of the patient at the time of testing, the change in the deviation from distance to near, and the spherical equivalent refractive error for the afterimage test. A low correlation also existed between the age of the patient and the depth of ARC (superficial or deep-rooted). We conclude that the clinical features of strabismus cannot be utilized effectively to predict the status of retinal correspondence.

Evaluation and diagnosis of incomitant ocular deviations.

Incomitant ocular deviations can indicate the presence of a significant health care problem and can produce distressful patient symptoms. Appropriate diagnosis and management of such problems are needed. This clinical review discusses the etiology, classification, and extraocular muscle changes associated with incomitant ocular deviations. The various testing procedures needed to determine the specific extraocular muscle involved are discussed in detail. The basic management of such deviations is reviewed.

Clinical objective assessment of the accommodative response.

Objective assessments are often needed in a visual examination, and are often more reliable, and therefore helpful, in the decision-making process of patient care. One visual function that is generally evaluated subjectively is accommodation. In those patients that cannot respond properly, an objective assessment is needed. This paper discusses a procedure for the objective assessment of the amplitude of accommodation, the status of the accommodative response of each eye, and the facility of accommodation.

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.

Adaptation to vertical prism.

Patients with vertical heterophoria and a reduced ability to adapt to an induced vertical prism are appropriate patients for a vertical prismatic correction. A clinical method is presented for identifying those patients with a reduced ability to adapt to an induced vertical prism.

Horizontal and vertical vergence training and its effect on vergences and fixation disparity curves: I. Horizontal data.

The purpose of this study was to assess the effects of horizontal and vertical vergence training on fusional vergences and the fixation disparity (FD) curve. Thirty-four subjects were divided into three groups. One-third served as controls and the other two-thirds underwent 5 h of supervised horizontal and vertical vergence training, respectively. Before and after the 4 week training period, vergences and FD curves were measured by a single individual who was intentionally uninformed of each subject's group. We hypothesized that the subjects in the horizontal training group would have increased vergence amplitudes and flatter FD slopes. Our analysis revealed that the positive vergences increased significantly for those in the horizontal group. No evidence was found to suggest changes in any variables related to the FD curve. Because type II errors were likely to be unacceptably large, further work is necessary to determine the relation between fusional vergence training and variables derived from the FD curve.

Horizontal and vertical vergence training and its effect on vergences, fixation disparity curves, and prism adaptation: II. Vertical data.

The purpose of this study was to assess the effects of horizontal and vertical vergence training on vertical fusional amplitudes, the vertical fixation disparity (VFD) curve, and prism adaptation. Thirty-four subjects were divided into three groups. One-third served as controls and the other two-thirds underwent 5 h of supervised horizontal and vertical vergence training, respectively. We hypothesized that subjects in the vertical group would manifest increased vertical vergence amplitude and coefficients of adaptation in concert with flatter VFD slopes. Before and after the 4-week training period, vertical vergences, fixation disparity (FD) curves, and coefficients of vertical prism adaptation were measured by a single individual who was intentionally uninformed of each subject's group. Analysis of the data suggests that changes in the vertical fusional amplitudes increased slightly. Although changes in the VFD slope and coefficient of prism adaptation were not statistically significant, the changes were much greater in the vertical group and in the hypothesized direction. We suggest that the results offer preliminary support for our hypothesis.

Ocular hypertension or early undetected glaucoma?

This paper reviews the diagnostic process and the utilization of specific testing procedures - including patient history, anterior chamber evaluation, intraocular pressure measurement, optic disc evaluation, nerve fiber layer evaluation, visual field evaluation, and psychophysical and electrophysiological testing - for the clinical differentiation of ocular hypertension and primary open-angle glaucoma.

Efficacy of computerized vergence therapy.

The purpose of this study was to determine the efficacy of computerized fusional vergence therapy and the effect of two different vergence training velocities. Six subjects received positive vergence training using a slow vergence training rate (0.75 delta/s) and six subjects received positive vergence training using a fast vergence training rate (5.00 delta/s). Six subjects served as controls and did not receive therapy. The duration of therapy was 80 min over a period of 4 weeks. All training activities were monitored. All vergence evaluations were double masked. Subjects using a slow training rate showed significant increases in positive vergence ranges as measured with the major amblyoscope, whereas subjects training with fast rates did not. We conclude that vergence therapy using a computerized video display is an effective technique for increasing the amplitudes of positive fusional vergence and that slower rates are more productive than faster rates.

Studies in vertical fixation disparity.

We studied vertical fixation disparity (VFD) with the purpose of assisting the clinician in the evaluation of patients having vertical heterophoria and/or vertical anisometropia and in the prescription of an appropriate vertical prismatic correction. Our research shows that VFD represents a relatively stable and reliable measurement of the vertical deviation; provides the clinician with a mechanism to study a patient's ability to adapt to an induced vertical fusional demand; and provides a process to determine the amount of the vertical prismatic correction.

Clinical evaluation of vertical fixation disparity. Part IV. Slope and adaptation to vertical prism of vertical heterophoria patients.

The purpose of this study was to determine the characteristics of the clinically measured vertical fixation disparity (VFD) curve and the ability to adapt to vertical prism for patients who have a vertical heterophoria and are comfortably wearing vertical prism, and to relate these data to similar findings for nonvertical heterophoria patients. The correlation between the amount of vertical prism that was being worn comfortably and the amount of vertical prism that reduced the VFD to zero was also evaluated. The results indicate that patients with vertical heterophoria who are wearing vertical prismatic corrections comfortably have VFD curves with shapes and slopes similar to nonvertical heterophoria patients; have lower coefficients of adaptability to vertical prism than nonvertical heterophoria patients; and the amount of the vertical prismatic correction to produce visual comfort can be determined by the vertical prism that reduces the VFD to zero.

Clinical comparison of congenital or early onset paretic vertical strabismus vs. acquired paretic vertical strabismus.

Thirty-five patients having paretic vertical strabismus were evaluated to determine which clinical parameters could best be used to differentiate congenital or early onset vertical strabismus from late onset vertical strabismus. Those patients with late onset deviations had a higher incidence of diplopia, a higher incidence of cyclodeviation, a higher incidence of compensatory head posture, and manifested larger vertical deviations in the primary position. However, the degree of incomitance, the prevalence of amblyopia, and the level of stereoacuity, did not distinguish the two patient groups. Prism therapy was equally successful for both groups.

Clinical evaluation of vertical fixation disparity. Part II. Reliability, stability, and association with refractive status, stereoacuity, and vertical heterophoria.

The use of vertical fixation disparity data in the management of patients with vertical heterophoria will be more appropriate and effective when the clinical characteristics of vertical fixation disparity measurements are better understood. In this study the reliability and stability of the vertical fixation disparity curve and the relation of the vertical fixation disparity data to refractive status, stereoacuity, and vertical heterophoria were investigated. The results indicate that although the shape of the vertical fixation disparity curve is stable and can be statistically represented by a straight line, the slope changes with time, more so over weeks and months than during the day, and has no significant relation with the refractive status, with the level of stereoacuity, or with the presence or absence of vertical heterophoria.

Clinical evaluation of vertical fixation disparity. Part III. Adaptation to vertical prism.

The purpose of this study was to determine if any relation exists between the ability to adapt to vertical prism and the slope of the fixation disparity curve, and if ocular discomfort, while wearing the inappropriate vertical prism, is correlated with the adaptation ability. Patients who showed the greatest adaptation ability generally had flatter slopes than patients who showed the least adaptation ability. The presence or absence of symptoms did not indicate how the patient would adapt to vertical prism. We conclude that greater care and concern should be used in the consideration of an induced vertical prism if the slope of the fixation disparity curve is steep.