George W. Fulk

A randomized trial of the effect of single-vision vs. bifocal lenses on myopia progression in children with esophoria.

Background Bifocals have long been thought to reduce progression of childhood myopia. However, this hypothesis has not been definitively evaluated. Methods We conducted a randomized clinical trial to test the hypothesis that bifocals slow myopia progression in children with near-point esophoria. Eighty-two myopic children were randomized to single-vision glasses (n = 40) or to bifocals with a +1.50 D add (n = 42) and were followed for 30 months. Refraction was measured by an automated refractor after cycloplegia. The primary outcome was myopia progression defined as the difference between the spherical equivalent at baseline and at the 30-month examination, averaged over both eyes. Results Follow-up was incomplete for six children in the bifocal group and one child in the single-vision group. Among the children completing the 30 months of follow up, myopia progression (mean spherical equivalent of the two eyes) averaged 0.99 D for bifocals and 1.24 D for single vision (unadjusted, p = 0.106; adjusted for age, p = 0.046). Treatment groups differed in their cumulative distributions (Kolmogorov-Smirnov procedure, p = 0.031). Evidence for a treatment effect on growth in vitreous chamber depth was similar (p = 0.046 by K.S.). Conclusion Use of bifocals, instead of single-vision glasses, by children with near-point esophoria seemed to slow myopia progression to a slight degree.

Seasonal Variation in Myopia Progression and Ocular Elongation

Purpose. To evaluate possible seasonal variations in myopia progression and ocular elongation in school children. Methods. Seventy-one children who were enrolled in a clinical trial of bifocals were examined every 6 months for 30 months. Three 6-month intervals (“winters”) included none of the summer vacation from school, and two intervals (“summers”) included all of the summer vacation. Myopia was evaluated, after cycloplegia with 2 drops of 1% tropicamide, by automated refractor, and changes in axial length and in vitreous chamber depth were measured by A-scan ultrasonography. Data from left and right eyes were averaged because there was no evidence of a significant eye-visit interaction. Analysis of variance with a planned contrast was used to evaluate differences between the observed rates of change over the two summers compared with expected rates assuming no seasonal effect. Results. For 37 children in single-vision lenses, myopia progression rates over the two summers averaged 0.15 D compared with 0.32 D over the three winters. For 34 children in bifocal glasses, summer rates averaged 0.07 D compared with 0.30 D for winters. Analysis of variance showed that seasonal effects on myopia progression were significant (p < 0.025) for both groups for the first summer and approached significance for the second summer. Increases in vitreous chamber depth were also slower during the summer, significantly so (p < 0.01) for both summers in the single-vision group and for the second summer only in the bifocal group. Changes in axial length were somewhat slower in the summer, but the effect of season reached statistical significance in that variable only for the second summer in the bifocal group (p = 0.031). Conclusion. Myopia progression rates were slower during the 6-month periods that included all of the summer vacation than would be expected assuming no seasonal effect. Ocular growth was also slower in the summer; but that trend, in most cases, was statistically significant only for changes in vitreous chamber depth and not for axial length.

The effect of changing from glasses to soft contact lenses on myopia progression in adolescents

At the end of a clinical trial of bifocals as myopia treatment, subjects were allowed to select any type of optical correction they wished and were asked to return in 1 year. This report gives results of that last examination with emphasis on how progression rates differed between those remaining in their original type of glasses compared with those who switched to soft contact lenses. We found that myopia progressed at an age‐adjusted average rate of 0.74 D in 19 children who switched to soft contact lens wear compared with 0.25 D for 24 children remaining in glasses (p < 0.0001). Increased growth of the vitreous chamber appeared to account for much of this excess myopia progression, although the difference in that variable did not reach statistical significance (p = 0.101). We also noted a 0.203 D steepening in the corneal curvature in contact lens wearers compared with spectacle wearers whose corneas steepened very little (0.014 D, p = 0.007). Soft contact lens wear was also accompanied by a greater change in the near‐point phoria which moved 4.5 prism dioptres in the exo direction compared with spectacle wearers who experienced only a 1.4 prism dioptre divergent shift (p = 0.048).

Pilocarpine gel for the treatment of demodicosis--a case series.

Background. Excessive numbers of the mite, Demodex folliculorum, in the eyelash follicles cause itching and is referred to as demodicosis. We evaluated 4% pilocarpine gel as a treatment for this condition. Methods. An advertisement was placed in a retirement home newsletter, requesting persons with ocular discomfort. Respondents were examined for Demodex and persons with abundant mites were invited to participate. One eye was treated with pilocarpine gel; the other eye was untreated. The relative abundance of mites was evaluated at baseline, after 1 and 2 weeks of treatment. Subjects kept a daily log of symptoms. Results. Eleven of 22 persons with ocular itching had abundant Demodex. Mites were reduced significantly by the treatment (p=0.017). The amount of mite reduction was closely correlated with the extent to which itching was alleviated (r=0.811, p=0.008). Conclusion. Abundant Demodex is an important cause of ocular itching in older persons. Mites can be reduced with pilocarpine gel and itching alleviated.

Baseline characteristics in the Myopia Progression Study, a clinical trial of bifocals to slow myopia progression.

Background. Retrospective studies have indicated that myopic children with nearpoint esophoria experienced slower myopia progression if they wore bifocal glasses rather than single-vision glasses. A small, 18-month clinical trial also supported that finding, but the results were not statistically significant. The Myopia Progression Study was funded by the National Eye Institute to test more rigorously the efficacy of bifocals, compared with single-vision glasses, in slowing myopia progression in children with nearpoint esophoria. A secondary objective of the study was to identify other variables that might influence the rate of myopia progression. This report describes the design and methods of the Myopia Progression Study and the baseline characteristics of the subjects. Methods. A 3-year, randomized clinical trial was initiated. Subjects were children between 6 and 12 years of age who were myopic (at least -0.50 D in each eye) and who demonstrated nearpoint esophoria by the von Graefe technique. Results. Eighty-two children were enrolled. After blocking by gender and clinical site (two sites), subjects were randomly assigned to one of the two treatments: correction with single-vision spectacle lenses or correction with bifocal lenses having a +1.50 D add in a flattop segment. The average degree of myopia at baseline was –2.31 D (SD = 1.31 D). Conclusion. This clinical trial can be expected to determine the effectiveness of bifocal glasses in slowing the progression of myopia in children with nearpoint esophoria.

Sympathetic Denervation of the Iris Dilator in Noninsulin- Dependent Diabetes

Twenty-three subjects with noninsulin-dependent diabetes mellitus (NIDDM) and 23 age- and sex-matched controls were tested for sympathetic denervation of the iris dilator by comparing the mydriatic effect of the combination of 1% phenylephrine and 1% tropicamide with that of 1% tropicamide alone. Most of the diabetic subjects had no clinical signs of severe diabetic complications. Nine diabetics and two controls showed sympathetic denervation, defined as a 1 mm or greater dilation due the addition of 1% phenylephrine. One of those two controls had a recent history of vascular headache. The diabetics with pupillary neuropathy had higher glycosylated hemoglobin percentages and a history of higher fasting blood sugars (FBSs) than the diabetics with normal pupils. Our results show that pupillary neuropathy can develop in persons with diabetes, often before the other complications of diabetes become manifest.

Is Esophoria a Factor in Slowing of Myopia by Progressive Lenses?: Author’s Response

Purpose. Our previous findings suggest that myopia can be slowed by wearing progressive lenses, and one possible mechanism for this is through the oculomotor system. We reanalyzed our findings to investigate the relationship between baseline oculomotor parameters and change in refraction, and between the change in these values and change in refraction. Methods. Children who wore progressive lenses (N = 38; 26 with +1.50 D addition, and 16 with +2.00 D addition) or single-vision lenses (N = 32) had refraction, distance heterophoria, near heterophoria, and stimulus AC/A ratio measured prospectively over a 2-year period. Results. There were no statistically significant correlations between baseline heterophoria or AC/A values and change in refractive error. Distance and near heterophoria did not change significantly over the 2 years of the experiment; AC/A ratio decreased significantly, but in an equivalent manner for both groups. In the combined progressive lens group, change toward more exophoria at near was associated with less myopia progression. However three-way analysis of variance (visit × lens type × esophoria/nonesophoria) showed significant main effects in refraction over all five visits. There was a significant interaction between lens type and visits; there was no significant interaction between lens type and esophoria/nonesophoria grouping. Three-way analysis of variance showed a statistically significant decrease of AC/A ratio over all five visits; there was no interaction of visit by lens or visit by phoria grouping. Conclusions. Although there were no statistically significant differences between esophoric and nonesophoric subjects, there was only 46% as much myopia progression in the progressive lenses-esophoric group as in the progressive lenses-nonesophoric group. In addition, there were no differences in AC/A ratio between esophoric and nonesophoric subjects. However these findings are not definitive. This experiment was not designed to discriminate between refraction and oculomotor changes in esophoric and nonesophoric subjects and lacked the necessary statistical power to do so.

Optic nerve crescents and refractive error

In this paper we discuss whether the presence of an optic nerve crescent might affect the way in which axial length and corneal curvature interact to determine refractive error. Subjective refraction, keratometry, measurement of body height, axial length of the eye, and stereophotography of the optic nerves were performed on 224 subjects, 8- to 25-years-old. Photographs were examined under magnification; optic nerve crescents, if present, were measured in the horizontal dimension. Those measurements were then corrected for magnification due to the eye and the camera. Logistic regression analysis suggested that male gender and myopic refractive error were most directly associated with the presence of a large crescent, whereas axial length, age, and horizontal keratometry reading were less directly associated with the presence of a crescent. The relation between axial length and refractive error differed among those with large crescents compared to those with small or no crescents. Simple regression showed that, for those with a crescent at least 0.2-mm wide, a 1-mm greater axial length was associated with, on the average, 1.26 D of myopia. For those with smaller or no crescents, a 1-mm greater axial length was associated with only 0.66 D of myopia. This difference was statistically significant at the 0.02 level of confidence.

The Effect of Simulated Altitude on the Visual Fields of Glaucoma Patients and the Elderly

We investigated whether mild hypoxia, such as may be encountered in civilian aircraft, causes temporary visual field defects in elderly persons or temporarily increases pre-existing defects in persons with glaucoma. The central 24-2 program on the Humphrey automated perimeter was used to test visual fields in 3 groups of subjects: 6 with glaucoma; 12 age-matched controls, all of whom were over 44 years of age; and 6 normal subjects under 36 years of age. Visual fields were tested at ground level and at simulated 3000 m (10,000 ft) in an alternating sequence. A repeated measures design of multiple analysis of variance was used to analyze the data. Altitude was found to have no effect on the visual fields of subjects with glaucoma, agematched normals, or younger subjects. We found no evidence to suggest a change in the present Federal Aviation Administration (FAA) standards, which allow a special certificate to be issued to persons with glaucoma who wish to obtain medical clearance to operate civilian aircraft, nor have we found any evidence that should discourage glaucoma patients from flying as passengers.