Effect of bilateral macular scotomas from age-related macular degeneration on reach-to-grasp hand movement.

PURPOSE: Vision plays a critical role in reaching and grasping objects. Consequently, bilateral macular scotomas from age-related macular degeneration (AMD) may affect reach-to-grasp movements. The purpose of this work was to investigate changes in reach-to-grasp movement dynamics and to relate those changes to the characteristics of subjects' preferred retinal loci (PRL), scotomas, and visual acuities. METHODS: Three-dimensional positions of the index finger and thumb were recorded while subjects with bilateral scotomas and subjects with normal vision reached for and grasped blocks of three widths at two distances under binocular and monocular viewing conditions. Reach-dynamic parameters and the grip aperture (thumb-index finger distance) were calculated. Retinal locations and sizes of subjects' scotomas and PRLs were mapped with a scanning laser ophthalmoscope. RESULTS: Scotoma subjects' hand trajectories had longer movement durations, lower maximum velocities, and longer visual reaction times than those of control subjects. With monocular viewing, maximum grip aperture (MGA) increased as a function of block width at a significantly higher rate for scotoma subjects than for control subjects. MGA decreased with increasing PRL bivariate normal ellipse area, and visual reaction time increased with decreasing acuity of the eye tested. CONCLUSIONS: Compared with normally sighted subjects, subjects with bilateral macular scotomas from AMD have reach-to-grasp movements with longer trajectories, longer visual reaction times, lower velocities, and altered MGA-block width scaling. Visual reaction time and MGA are directly related to PRL characteristics. Deficits in reach-to-grasp movement caused by macular scotomas are greater in degree than those reported by others for real or artificial peripheral scotomas.

Retinal image location of hand, fingers, and objects during manual tasks.

PURPOSE: A new method was developed using the scanning laser ophthalmoscope (SLO) to investigate the effects of central visual loss on eye-hand coordination in manual tasks. Using the SLO, the retinal positions of the hand, fingers, and objects are imaged and recorded while a subject performs a manual task. METHOD: A video camera images the subject's hand and objects to be manipulated in the SLO laser-beam raster, producing a video image of a subject's hand, fingers, and objects on the subject's retina while the objects are manipulated. A subject with bilateral central scotomas and an age-matched control subject with normal vision traced an ellipse with the index finger, tapped four disks in sequence, and carried out a pattern duplication task with pegs. Retinal positions of the fovea or preferred retinal locus (PRL), fingers, and objects were measured from digitized SLO images. RESULTS: In all tasks, the fovea or PRL was directed to an object or position before the fingers arrived. This lead time was much greater for the scotoma subject than the control subject ( approximately 1400 vs. approximately 400 ms, respectively). The scotoma subject was much less accurate in placing the PRL and fingers on objects and required substantially more time for task completion than the control subject. CONCLUSIONS: The coordination of foveal fixation and finger placement found with the SLO method was similar to that found by others using eyetracking techniques with visually normal subjects. The presence of a central scotoma and use of a PRL caused marked deterioration in the quality of this coordination. Unlike eyetracking methods, the SLO technique does not require calibration because the positions of the fingers and objects are directly observable on the retina. This method could be useful in studying eye-hand coordination of individuals with scotomas that affect foveal vision.

Retinal locus for scanning text.

A method of mapping the retinal location of text during reading is described in which text position is plotted cumulatively on scanning laser ophthalmoscope retinal images. Retinal locations that contain text most often are the brightest in the cumulative plot, and locations that contain text least often are the darkest. In this way, the retinal area that most often contains text is determined. Text maps were plotted for eight control subjects without vision loss and eight subjects with central scotomas from macular degeneration. Control subjects' text maps showed that the fovea contained text most often. Text maps of five of the subjects with scotomas showed that they used the same peripheral retinal area to scan text and fixate. Text maps of the other three subjects with scotomas showed that they used separate areas to scan text and fixate. Retinal text maps may help evaluate rehabilitative strategies for training individuals with central scotomas to use a particular retinal area to scan text.

Retinal location of the preferred retinal locus relative to the fovea in scanning laser ophthalmoscope images.

PURPOSE: It is difficult to determine the position of a preferred retinal locus (PRL) relative to the fovea in scanning laser ophthalmoscope (SLO) images as a result of disease-related retinal morphologic changes that obscure the fovea. To overcome this problem, we developed a method for determining retinal foveal position based on normal fixation position relative to the optic disk. The normal foveal position measurements can then be used to estimate the distance between a PRL and the fovea. METHODS: Using the SLO, foveal position was determined for 50 normal subjects by measuring the retinal locus of fixation relative to the optic disk in undistorted SLO images. The resulting normal foveal fixation area is described by a bivariate normal ellipse that can be plotted on any undistorted SLO image. Measurement reliability was assessed by repeated measurements. The PRL relative to the normal foveal fixation area was determined for 24 subjects with macular degeneration and bilateral central scotomas. RESULTS: The normal foveal fixation area based on all 50 subjects is described by a p = 0.9 bivariate ellipse whose centroid is located 12.6 degrees temporal to the temporal optic disk edge and 1.4 degrees inferior to a horizontal line bisecting the disk. PRL area is shown to increase with distance from the foveal fixation ellipse centroid. The shape of the PRL, characterized by the ratio of PRL ellipse major to minor axis, was found to depend on whether the PRL was vertically or horizontally aligned with the foveal fixation centroid. CONCLUSIONS: PRL position relative to the fovea can be reliably estimated by plotting the normal foveal fixation bivariate ellipse on undistorted SLO images of retinas in which the fovea is obscured as a result of the disease process.

Distortion and size calibration of the scanning laser ophthalmoscope (SLO) laser-beam raster.

PURPOSE: The Rodenstock scanning laser ophthalmoscope (SLO) is useful for mapping retinal function and for developing and evaluating visual rehabilitation methods. It is essential to know the visual angle subtended by stimuli in the SLO laser-beam raster and to accurately measure angular distances between objects in the final SLO image. To accomplish this, the angular extent of the SLO laser-beam raster must be calibrated. METHODS: We developed a simple method and apparatus for calibrating the raster and used it for repeated calibrations during a 3-month period. RESULTS: The laser-beam raster is quite stable in shape and size, but it is trapezoidally distorted in the vertical direction. Consequently, SLO images are distorted. CONCLUSIONS: Trapezoidal distortion of the SLO laser-beam raster can cause stimulus size to change as much as 10% from the top to the bottom of the raster. Measurements of fixed horizontal retinal landmark distances in SLO images can also vary as much as 10%. We developed a straightforward mathematical method for correcting distortion in SLO image measurements.

Kansas City VAMC Optometry Residency Program: a survey of residents since 1975.

BACKGROUND: The nation's first one-year, Council on Optometric Education accredited hospital-based optometry residency program began at the Kansas City Veterans Affairs Medical Center in 1975. As part of the 25th anniversary review, past residents were surveyed to determine whether the residency had met their goals and influenced their postresidency activities. This is the first in-depth study of a single residency program. METHODS: A 34-question survey was developed based on one previously used in a 1987 national study of Veterans Affairs residents. The survey was designed to provide data comparable to that found in other residency surveys. RESULTS: Forty-eight of 50 former residents responded, and at least one survey was returned for every year from 1975 through 2000. One hundred percent of residents noted that the program met or exceeded expectations in patient diversity, workload, and level of responsibility. Additionally, almost 30% of residents currently or previously held Veterans Affairs staff positions, and they have collectively published 316 papers, 33 textbook chapters, and five textbooks. CONCLUSIONS Judged by these responses, the Kansas City Veterans Affairs Medical Center Optometry Residency Program offers an exceptional clinical training program that surpasses resident expectations. Finally, former graduates of the program have made a significant contribution to patient care and to the optometric profession as demonstrated by their clinical, academic, and research accomplishments.