Alternating ptosis after bilateral frontalis muscle suspension for congenital ptosis.

PURPOSE: To report an unusual response to bilateral frontalis suspension surgery for congenital ptosis. METHODS: Case report. RESULTS: A 6-year-old child with infantile esotropia and bilateral congenital ptosis received a homologous fascia lata frontalis suspension. After surgery, the patient exhibited an alternating ptosis, caused by alternating unilateral frontalis muscle contraction, which has persisted throughout 3 years of postoperative observation. CONCLUSION: Symmetric frontalis muscle activation may not always occur after bilateral frontalis muscle suspension surgery for congenital ptosis. Amblyopia, strabismus, or fixation preference may predispose patients to use unilateral brow elevation, despite bilateral frontalis muscle suspension surgery.

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.

Axial length estimation in strabismic patients.

BACKGROUND: Previous studies have indicated that axial length determination is important in strabismic patients for defining the limit for a safe maximum recession of the medial rectus. Also, the response to strabismus surgery may be, in part, a function of axial length. We previously published a formula for predicting axial length based on age and refractive error; however, its accuracy has not been tested in a patient population that is different from the one used to generate the formula. The purpose of this study is to test a formula for estimating axial length, given age and refractive error, in a population that is different from that from which it was generated. METHOD: We measured axial length using A-scan ultrasonography in 163 consecutive patients undergoing strabismus surgery. Twenty-nine patients were younger than 18 months of age; 134 patients were between 18 months and 10 years of age. We compared the measured axial length determination with the axial length value estimated by a formula generated from our previous published series. RESULTS: For patients younger than 18 months of age, the equation estimated axial length within 0.5 mm in 41.4% of patients, within 1.0 mm in 79.3% of patients, and within 1.5 mm in 93.1% of patients. For patients between 18 months and 18 years of age, the formula estimated axial length within 0.5 mm in 37.3% of patients, within 1.0 mm in 73.1% of patients, and within 1.5 mm in 87.3% of patients. CONCLUSIONS: The formula may be useful for the strabismus surgeon in estimating axial length when A-scan ultrasonography is not available in an operating room setting, particularly in congenital esotropes who require larger recessions in small eyes. If, however, A-scan ultrasonography is available, it is preferable to using the formula. The formula is not sufficiently accurate for use for calculating intraocular lens power.

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.

Autosomal recessive ocular albinism associated with a functionally significant tyrosinase gene polymorphism.

Autosomal recessive ocular albinism (AROA) is a disorder characterized by reduced pigmentation of the retina and iris, hypoplastic fovea, variably reduced visual acuity and nystagmus. Pigmentation of the skin and hair is normal, but is usually slightly lighter than in unaffected sibs. We analysed 12 unrelated patients with AROA, and found that two had abnormalities of the tyrosinase (TYR) gene. These two patients were each a compound heterozygote for a different pathologic mutant allele and an allele containing a 'normal' polymorphism, Arg402Gln, which results in a tyrosinase polypeptide with reduced thermal stability. In these patients, AROA thus appears to represent a clinically mild form of OCA1, with a fixed visual deficit resulting from low tyrosinase activity during fetal development but with normal pigmentation of the skin and hair postnatally.

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.

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.

Autosomal dominant peripheral preretinal deposits.

Abnormal yellow-white peripheral preretinal deposits are described as an autosomal dominant disorder in ten members of a large pedigree spanning three generations. The absence of any other major vitreoretinal abnormalities or retinal function disorders suggests that this is a benign disease; the nature and origin of the preretinal deposits is obscure.