The +10 diopter lens occluder.

BACKGROUND: It would be useful to be able to visualize the eye under cover during the cover test. Used as an occluder, a +10 diopter (D) lens will permit such visualization. It is important to know if a +10D lens creates dissociation that is qualitatively similar to an opaque occluder. METHODS: The angle of strabismus was measured in 33 patients with esotropia. Seventeen had intermittent exotropia, and 15 had dissociated vertical divergence with both an opaque occluder and a +10D lens used as an occluder. The findings were then compared. RESULTS: In 64 of the 65 patients participating in this study, the measurements obtained with the 2 occluders agreed within 3 prism diopters on repeated testing. In the remaining patient, the measurements differed by 5 prism diopters. In all patients, the dissociated eye could be clearly visualized through the +10D lens. CONCLUSION: A +10D lens permits excellent visualization of the dissociated eye and provides measurements that are qualitatively similar to those obtained with a standard occluder. Arch Ophthalmol. 2000;118:1071-1073

Ocular torticollis and facial asymmetry.

OBJECTIVE: Ocular torticollis secondary to congenital superior oblique palsy can be associated with facial asymmetry. The purpose of this study was to determine if other ocular causes of head tilting also carry the same association. DESIGN: The study design was clinical evaluation of patients. PARTICIPANTS: Fifteen patients with marked, moderate, or mild head tilts associated with dissociated vertical deviation (DVD), and 3 patients with nystagmus and a torsional null point. A control group was comprised of 3 patients with congenital superior oblique palsy, 3 with traumatic superior oblique palsy, and two normal patients. INTERVENTION: A masked observer analyzed full-face photographs of the subjects. MAIN OUTCOME MEASURE: The presence of facial asymmetry. RESULTS: Facial asymmetry due to bending in/of the sagittal plane of at least two degrees was found in 3 of 4 patients with a marked head tilt from DVD, in 2 of 5 five patients with a moderate head tilt from DVD, in one of 3 patients with a head tilt due to nystagmus, and in one of 3 patients with a head tilt due to congenital superior oblique palsy. None of the patients with a mild head tilt from DVD, traumatic superior oblique palsy, or the normal controls had clinically noticeable facial asymmetry. CONCLUSION: Facial asymmetry can be associated with abnormal head postures, specifically, large head tilts from DVD or nystagmus.

Distance/near differences in intermittent exotropia.

BACKGROUND: Burian's classification of exotropia based on the difference between the distance deviation and near deviation (distance/near differences) leaves some questions unanswered. Controversy exists concerning whether the divergence excess pattern is caused by an excess of divergence or by excessive accommodative convergence. Much of the literature on this subject has been confusing because investigators did not eliminate tenacious proximal fusion as an artifact in calculating the ratio of accommodative convergence to accommodation (AC/A ratio). Previously, one of us (B.J.K.) proposed a classification system that respected this artifact and subdivided the classification system proposed by Burian. METHODS: A total of 202 consecutive patients with an exotropia underwent a series of measurements to determine the respective role of accommodative convergence and tenacious proximal fusion as a cause for their distance/near differences. In addition, the value obtained by a rapid prism adaptation test as a possible substitute for 1 hour of monocular occlusion was studied. RESULTS: In 98 patients, the initial distance deviation exceeded the near deviation. In 10 patients, the distance/near differences were caused by a high AC/A ratio, which would have been mislabeled by Burian's classification system. Brown's recommendation of using +3.00-diopter lenses at near to diagnose simulated divergence excess would have led to the misdiagnosis of a high AC/A ratio in 61 of these patients. In 26 patients, the near deviation exceeded the distance deviation. Burian's classification would have incorrectly labeled 2 patients as having convergence insufficiency when, in fact, they had pseudoconvergence insufficiency. The new proposed classification system proved 100% sensitive and 100% specific (6 of 6 patients for both parameters) for identifying preoperatively exotropic patients who postoperatively developed an esotropia at near with a high AC/A ratio. Rapid prism adaptation tests at near proved useful for identifying the presence of tenacious proximal fusion, but were not accurate in its quantification. CONCLUSIONS: The validity and utility of the new classification system was confirmed. Identification of exotropic patients with a high AC/A ratio and consideration of nonsurgical treatment is important. The rapid prism adaptation test is qualitatively, but not quantitatively, the same as 1 hour of monocular occlusion.

The efficacy of SimulVue and Unilens RGP aspheric bifocal contact lenses in the treatment of esotropia associated with a high accommodative convergence/accommodation ratio.

PURPOSE: This was a prospective study assessing the efficacy of the SimulVue bifocal contact lens and the Unilens RGP aspheric multifocal contact lens (Unilens, Largo, Fla.) in the treatment of high accommodative convergence/accommodation (AC/A) esotropia in an adolescent and postadolescent population. METHODS: Those patients meeting the inclusion criteria were fit with contact lenses with use of full cycloplegic refraction and later retested by an examiner masked to the previous binocular status. Particular attention was given to the sensory status and the motor fusion of each patient in their bifocal spectacles and then in their bifocal contact lenses. All patients were followed up for at least 6 months after the contact lenses were fitted. RESULTS: Five of the six patients demonstrated larger angles of esophoria or tropia at near with the contact lenses than with bifocal spectacles. The only patient who maintained excellent stereopsis in bifocal contact lenses was the one who normalized her AC/A ratio during this study and no longer required a bifocal in her spectacle correction for fusion. The two patients who initially had no stereopsis but good alignment in spectacle correction had a large esotropia at near fixation with bifocal contact lenses. CONCLUSIONS: The SimulVue and Unilens RGP aspheric bifocal contact lenses did not adequately treat adolescent patients who had esotropia associated with a high AC/A ratio.

The relationship between dissociated vertical divergence (DVD) and head tilts.

INTRODUCTION: Dissociated vertical divergence (DVD) has been associated with manifest head tilts. Also, DVD has been described as demonstrating a characteristic response to forced head tilt by increasing the size of the DVD on contralateral tilt. METHODS: A series of 116 consecutive patients with DVD associated with infantile esotropia were examined according to a predetermined protocol between 1989 and 1994. Each patient was examined for a manifest head tilt. Also, the response of the DVD to forced ipsilateral and contralateral head tilt was analyzed. In addition, 100 consecutive patients with manifest head tilts were examined and the etiology of the tilt determined. RESULTS: A manifest head tilt was present in 35% (26/74) of patients with an ocular fixation preference and no prior vertical muscle surgery. None of the patients with alternating fixation and a history of no vertical muscle surgery manifested a head tilt. Most patients responded in the classically described manner by increasing the size of the DVD on forced contralateral tilt and decreasing the size of the DVD on ipsilateral tilt. Atypical responses were not related to the presence of oblique overaction. DVD was the etiology in 9 of 100 consecutive patients with a manifest head tilt. CONCLUSIONS: Patients with DVD often manifest a head tilt. Most respond by increasing the size of the DVD on forced contralateral head tilt and decreasing on ipsilateral tilt. Atypical responses did not appear to be influenced by oblique overaction. DVD is a relatively frequent cause of manifest head tilts.

Grating visual acuity with Teller cards compared with Snellen visual acuity in literate patients.

OBJECTIVE: To determine the usefulness of Teller Acuity Cards for detecting three levels of vision deficit, the cutoff for amblyopia (20/40 or poorer), vision impairment (20/70), or legal blindness (20/200). DESIGN: We compared grating visual acuity with the Teller cards with Snellen visual acuity (our gold standard) in 69 literate patients with amblyopia or other cause of vision loss in a prospective masked study. RESULTS: Teller card visual acuity and distance Snellen visual acuity correlated significantly (r = .508, P < .001); however, Teller card visual acuity explained only 26% of the variation in distance Snellen visual acuity. Teller card visual acuity had a low sensitivity for detecting vision deficit of 20/40 or poorer (58%), vision deficit of 20/70 or poorer (39%), or legal blindness (24%), but somewhat more accurately reflected near Snellen visual acuity than distance visual Snellen acuity. Teller cards had a higher positive predictive value--80% for 20/70 visual acuity and 43% for legal blindness, as determined by near Snellen visual acuity. Specificity of Teller cards was 88% for detecting visual acuity loss of 20/70 and 98% for legal blindness. Negative predictive value of Teller cards for detecting visual acuity loss of 20/70 was 50% and for legal blindness was 71%. CONCLUSIONS: Teller Acuity Cards may underestimate the presence of amblyopia of all types, legal blindness, and a specified level of vision impairment (20/70). Even in the presence of normal visual acuity measurements with Teller cards, significant visual loss as assessed by standard Snellen optotypes may be anticipated in many patients.

How far can a medial rectus safely be recessed?

Previous studies have suggested that the location of the equator should be important in determining the site of a "safe maximum recession" of a rectus muscle, and that the location of the equator should be a function of axial length. Exactly where in relationship to the equator a muscle can be safely recessed has never been scientifically determined. Over a 4-year period, we measured axial length on all patients we operated on for strabismus. Using a previously derived formula, we were able to calculate the limbus-to-equator distance, given axial length. Based on our analysis of 28 patients in whom we recessed one or both medial recti posterior to the equator, we believe that recessions of the medial recti up to 1.5 mm posterior to the equator should not produce postoperative medial rectus underaction associated with an overcorrection, but recessions that are further than 1.5 mm posterior to the equator may do so. Recessions to a point greater than 11 mm from the limbus do not appear to be associated with late progressive overcorrection provided that the site of recession is not greater than 1.5 mm posterior to the equator. Using our previously determined formula for estimating the location of the equator, given axial length, we have generated easy-to-use reference tables for determining the location of the equator in terms of millimeters posterior to the limbus. Also, based on axial length data from 180 strabismus patients, we have generated an algorithm for predicting axial length, given age, and refractive error, which may be useful to the strabismus surgeon in predicting the location of the equator when A-scan ultrasonography is not available.

Factors influencing response to strabismus surgery.

Based on analyses in a series of 116 patients, we found that the response to strabismus surgery (degrees of change of ocular alignment per millimeter of rectus recession) correlated significantly with the preoperative deviation for esotropic and exotropic patients. The prediction of response to strabismus surgery was not improved significantly with the inclusion of axial length, age, and/or preoperative refractive error beyond the prediction provided with use of only the preoperative deviation, even though we have previously suggested that the response to strabismus surgery should be related to axial length. We believed that larger eyes should have a smaller response for the same number of millimeters of surgery than smaller eyes. We now believe that although the response to strabismus surgery does correlate significantly and inversely with axial length, this correlation may not be clinically important given the much stronger influence of preoperative deviation.

Postoperative binocularity in adults with longstanding strabismus.

The authors tested preoperatively and postoperatively for binocularity with the Bagolini lenses in a series of 359 adults who underwent surgery for long-standing constant strabismus. Eighty-six percent of patients showed a binocular response with the Bagolini lens test almost immediately after surgery. Regardless of the type of deviation present preoperatively, the duration of strabismus, or the depth of amblyopia in the deviating eye (if present), the vast majority of patients developed binocularity. The development of binocularity with the Bagolini lenses after surgery appears to be related to the stability of the postoperative ocular alignment.

Variation in axial length and anatomical landmarks in strabismic patients.

The authors calculated axial length measurements in 185 consecutive patients undergoing strabismus surgery and found a mean measurement of 21.98 +/- 1.59 mm (range, 18.75-25.37 mm). Although significant correlation between axial length, refractive error, and age was found, wide variation was present, which indicates that age and refractive error could not accurately predict axial length. Based on a formula derived from a geometric model to determine the equator-limbus distance, given the axial length, the authors found that the equator had a mean distance from the limbus of 11.56 +/- 1.75 mm (range, 9.10-13.76 mm). Based on the variability found at surgery for the insertion-limbus distance, the number of millimeters of recession of the medial rectus from the insertion that would have been necessary to place it at the equator ranged between 3.5 and 8.5 mm in this series, and for the lateral rectus, 3.5 mm to 7.0 mm. The number of millimeters necessary to recess the lateral rectus to its point of tangency with the globe ranged between 9.5 and 14.4 mm.

Should recessions of the medial recti be graded from the limbus or the insertion?

In a series of 27 patients who were operated on for esotropia, we compared patient response to surgery and the distance the medial recti were recessed from the insertion and corneoscleral limbus. We found a much more significant correlation between the response and the amount the muscles were recessed from the insertion than from the corneoscleral limbus. Using partial correlation coefficients, we found that when we corrected for the amount of recession from the insertion, there was not a significant correlation between the response to surgery and the amount the muscles were recessed from the corneoscleral limbus. This suggests that the apparent correlation between the response to surgery and the amount of recession from the corneoscleral limbus simply reflects that the greater the recession from the corneoscleral limbus, the farther the muscle is likely to end up posterior to the insertion.

The influence of axial length on the response to strabismus surgery.

We performed axial length determinations preoperatively on a series of patients undergoing strabismus surgery. A statistically significant inverse correlation was found between axial length and the response (prism diopters per millimeter of medial rectus recession) for esotropic patients. The data suggest that a surgical formula designed to take axial length into account would decrease the variability in response to strabismus surgery in esotropic patients. Poor correlation was found between axial length and response to surgery in exotropic patients. We feel this poor correlation was due, in part, to the postoperative drift rate in exotropic patients as well as inaccuracies with the standard techniques used to determine the basic deviation on which surgery in exotropic patients is based.

Treatment of partly accommodative esotropia with a high accommodative convergence-accommodation ratio.

We conducted a prospective, randomized, masked comparison of two treatments for the nonaccommodative element in esotropic patients with a high accommodative convergence-accommodation ratio. One group received symmetric medial rectus recessions with posterior fixation sutures; the other received symmetric medial rectus recessions without posterior fixation sutures but augmented according to formula taking into account the near deviation. Previous experience had suggested that our surgical formula based solely on the distance deviation would lead to excessive undercorrections. A higher percentage of the augmented recession group achieved satisfactory alignment and were able to discontinue wearing bifocals postoperatively than the posterior fixation group. The data also showed a trend (though not statistically significant) suggesting that more members of the augmented recession group were able to discontinue wearing spectacles entirely. We concluded that the posterior fixation suture technique is not as effective as the augmented recession technique for the treatment of partly accommodative esotropia with a high accommodative convergence-accommodation ratio.

A randomized comparison of surgical procedures for infantile esotropia.

In a prospective, randomized, masked study we compared the treatment of infantile esotropia using bilateral medial rectus muscle recessions of a graded amount from the insertion to standard 10.5-mm recession from the corneoscleral limbus. Of the patients undergoing recession of the medial recti muscles 10.5 mm from the corneoscleral limbus, 33 of 39 (84%) achieved a final ocular alignment within 10 prism diopters of straight with one operation, compared to 26 of 41 (63%) of the patients undergoing a graded recession from the insertion. The difference was significant (.01 less than P less than .05 by the chi-square test).

The role of funduscopy and fundus photography in strabismus diagnosis.

Fundus photographs taken in 66 patients with vertical strabismus were analyzed in a blind study with respect to ocular torsion. The objective presence or absence of ocular torsion was then correlated with the patient's clinical diagnosis. The presence or absence of objective ocular torsion as seen in fundus photographs had a sensitivity of 0.86 and a specificity of 0.96 for diagnosing the presence of oblique dysfunction, and a sensitivity of 0.96 and specificity of 0.83 for diagnosing the presence of normal oblique function.