The use of dissimilar progressives in the management of presbyopia.

The management of anisophoria with bifocal spectacle correction has always presented a challenging refractive problem. Historically, practitioners have used dissimilar bifocal segments or bicentric grinding to neutralize induced vertical imbalance. We present a method of reducing anisophoria at near point with dissimilar progressive multifocals. By incorporating different progressive designs, anisophoria can be minimized to a tolerable level, based on the dioptric power of lens and progressive lens design.

The effect of relative spectacle magnification on aniseikonia.

PURPOSE: The purpose of this article is to study the effects of modifying relative spectacle magnification to determine what effect this has on aniseikonia, binocularity, and visual comfort. METHODS: A prospective analysis of 34 aniseikonic patients was undertaken. The etiology of aniseikonia varied from physiologically occurring to induced. Aniseikonic screening included manifest refraction, keratometry, axial length, Randot stereoacuity, associated phoria, and Keystone space eikonometry. A modified pair of spectacles was fabricated on the basis of magnification principles for iseikonic lenses. Each patient was also given a control pair of conventional spectacles. A 4-week trial period was allowed for each pair of spectacles, pertinent examination measurements were repeated, and a patient survey was administered. Data were analyzed by t-test and chi-square. RESULTS: Modifying relative spectacle magnification reduced mean aniseikonic error by 1.06% (P < 0.0001). A difference was found between the control and modified spectacles for subjective reports of visual comfort, performance, and eye-strain (P < 0.05). There was no difference between the two groups for stereoacuity or cosmetic appearance of lenses. At the conclusion of the study, 93% of patients preferred the modified lenses in direct comparison. CONCLUSIONS: Our results confirm that modification of lens designs to equalize relative spectacle magnification reduces aniseikonia and improves subjective comfort and performance of anisometropic spectacles.

The illuminated high contrast macular grid: a pilot study.

BACKGROUND: Analysis of visual disturbances in the central 10 degrees provides valuable data for the low vision clinician. Amsler grid testing in the visually impaired can be poorly visible and it can be difficult to transcribe results. Automated perimeters will accurately map retinal defects, but the equipment is expensive and this technique is time consuming. An Amsler grid was modified using principles of luminance and contrast to improve its accuracy, and its efficacy was compared to an automated perimeter. METHODS: Eighteen visually impaired patients (28 eyes) were prospectively evaluated at the Emory Low Vision Laboratory. Each patient had three central threshold visual field tests: automated perimetry (Humphrey model 690), conventional Amsler Grid, and Illuminated High Contrast Macular Grid (IHCMG). The Humphrey central 10-2 threshold automated visual field examination was performed to map the patient's retinal function. RESULTS: The Humphrey analysis identified (mean +/- one standard deviation) 2.4 +/- 1.4 defects per patient with an average percent defect area of 33.4 +/- 14.8 degrees. The IHCMG technique was not significantly different from the Humphrey technique for identifying the number of defects (2.25 +/- 1.5) (p > 0.05) or the percent defect area (26 degrees +/- 20 degrees) (p > 0.05). The conventional Amsler grid technique significantly under-evaluated the retinal defects compared to the Humphrey analysis of the number of defects (p < 0.01) and percent area of defects (p > 0.001). CONCLUSIONS: The IHCMG technique can be used as a simple, rapid and accurate analysis of the central 10 degrees visual field in the low vision patient.