Luminita Tarita-Nistor

Fixation characteristics of patients with macular degeneration recorded with the mp-1 microperimeter.

Purpose: The authors examined the fixation stability patterns of people with age-related macular degeneration (AMD) using the MP-1 microperimeter and describe a method to bypass some calibration artifacts that can influence the fixation results. Method: The preferred retinal locus (PRL) and fixation patterns of 37 eyes with AMD and the foveas location relative to the middle of the optic disc of 10 experienced controls were measured. For the patients, fixation characteristics such as the former foveas location, PRL distance, and fixation stability were analyzed. Results: For the controls, the mean foveal distance temporal to the middle of the optic disc was 15.5 deg ± 0.86 deg horizontally and –1.33 deg ± 0.71 deg vertically. Thirty-one out of 37 PRLs occurred in the upper and right quadrants of the retina. There were significant positive correlations between fixation stability and PRL distance from the former fovea. Time since diagnosis and acuity also showed positive correlations with fixation stability and PRL distance from the fovea. Conclusions: The authors recommend that fixation stability recorded with the MP-1 be analyzed based on the raw data. Most of the fixation parameters obtained agree with those reported in the literature, if proper calibration is used.

Eye Position Stability in Amblyopia and in Normal Binocular Vision

PURPOSE We investigated whether the sensory impairments of amblyopia are associated with a decrease in eye position stability (PS). METHODS The positions of both eyes were recorded simultaneously in three viewing conditions: binocular, monocular fellow eye viewing (right eye for controls), and monocular amblyopic eye viewing (left eye for controls). For monocular conditions, movements of the covered eye were also recorded (open-loop testing). Bivariate contour ellipses (BCEAs), representing the region over which eye positions were found 68.2% of the time, were calculated and normalized by log transformation. RESULTS For controls, there were no differences between eyes. Binocular PS (log(10)BCEA = -0.88) was better than monocular PS (log(10)BCEA = -0.59) indicating binocular summation, and the PS of the viewing eye was better than that of the covered eye (log(10)BCEA = -0.33). For patients, the amblyopic eye exhibited a significant decrease in PS during amblyopic eye (log(10)BCEA = -0.20), fellow eye (log(10)BCEA = 0.0004), and binocular (log(10)BCEA = -0.44) viewing. The PS of the fellow eye depended on viewing condition: it was comparable to controls during binocular (log(10)BCEA = -0.77) and fellow eye viewing (log(10)BCEA = -0.52), but it decreased during amblyopic eye viewing (log(10)BCEA = 0.08). Patients exhibited binocular summation during fellow eye viewing, but not during amblyopic eye viewing. Decrease in PS in patients was mainly due to slow eye drifts. CONCLUSIONS Deficits in spatiotemporal vision in amblyopia are associated with poor PS. PS of amblyopic and fellow eyes is differentially affected depending on viewing condition.

Fixation stability during binocular viewing in patients with age-related macular degeneration.

PURPOSE The authors examined the fixation stability of patients with age-related macular degeneration (AMD) and large interocular acuity differences, testing them in monocular and binocular viewing conditions. The relationship between fixation stability and visual performance during monocular and binocular viewing was also studied. METHODS Twenty patients with AMD participated. Their monocular and binocular distance acuities were measured with the ETDRS charts. Fixation stability of the better and worse eye were recorded monocularly with the MP-1 microperimeter (Nidek Technologies Srl., Vigonza, PD, Italy) and binocularly with an EyeLink eye tracker (SR Research Ltd., Mississauga, Ontario, Canada). Additional recordings of monocular fixations were obtained with the EyeLink in viewing conditions when one eye viewed the target while the fellow eye was covered by an infrared filter so it could not see the target. RESULTS Fixation stability of the better eye did not change across viewing conditions. Fixation stability of the worse eye was 84% to 100% better in the binocular condition than in monocular conditions. Fixation stability of the worse eye was significantly larger (P < 0.05) than that of the better eye when recorded monocularly with the MP-1 microperimeter. This difference was dramatically reduced in the binocular condition but remained marginally significant (95% confidence interval, -0.351 to -0.006). For the better eye, there was a moderate relationship between fixation stability and visual acuity, both monocular and binocular, in all conditions in which this eye viewed the target. CONCLUSIONS Fixational ocular motor control and visual acuity are driven by the better-seeing eye when patients with AMD and large interocular acuity differences perform the tasks binocularly.

Fixation Stability, Fixation Location, and Visual Acuity after Successful Macular Hole Surgery

PURPOSE This study examined whether changes in fixation stability and fixation location are good predictors of visual acuity after successful macular hole surgery. METHODS Ten patients with macular hole were tested before surgery and at 1 and 3 months after surgery. Visual acuity was measured with the ETDRS; fixation stability and fixation location were assessed with the MP-1 Microperimeter (Nidek Technologies Srl., Vigonza, PD, Italy). The quantitative measure of fixation stability was calculated with a bivariate contour ellipse area (BCEA). Fixation location shift was evaluated using the differential map analysis feature of the MP-1 Microperimeter. RESULTS There was a significant improvement in visual acuity after macular hole closure. Fixation location shifted an average of 0.55 deg and 0.87 deg at 1 month and 3 months after surgery, respectively. The fixation shift was not a good predictor of visual outcome. Fixation stability improved from an average of 0.35 deg(2) before surgery to 0.29 deg(2) at 3 months after surgery. The change in fixation stability (DeltaBCEA = BCEA before - BCEA after surgery) correlated highly with visual outcome. The regression model showed that DeltaBCEA accounted for a significant proportion of the variance in visual acuity both 1 and 3 months after surgery. CONCLUSIONS Some changes in ocular motor function explain the visual outcome after the anatomic success of macular hole surgery. Fixation location shift has no influence on visual acuity post-operatively; however, change in fixation stability is a strong predictor of visual outcome after successful closure of the macular hole.

Fixation Control before and after Treatment for Neovascular Age-Related Macular Degeneration

PURPOSE We studied changes in visual acuity (VA), fixation stability, and location of the preferred retinal locus (PRL) after treatment for unilateral neovascular age-related macular degeneration (AMD) for previously untreated eyes. Concomitant changes in fixation stability, PRL, and VA in the untreated fellow eye were also analyzed. METHODS Pre- and posttreatment tests of visual acuity, fixation stability, and PRL location in both the treated and the untreated eyes were performed on 13 patients undergoing three monthly intravitreal injections of ranibizumab in one eye. RESULTS For the treated eyes there were improvements in VA and fixation stability but no changes in the location of the PRL. No significant changes in any of the three variables were found in the untreated eye. CONCLUSIONS For previously untreated eyes, the improvement in visual acuity after intravitreal ranibizumab injections was accompanied by improvement in fixation stability.

Binocular interactions in patients with age-related macular degeneration: acuity summation and rivalry.

This study examined two aspects of binocular function in patients with age-related macular degeneration (AMD): summation/inhibition of visual acuity and rivalry. The performance of 17 patients with AMD was compared with that of 17 elderly controls and 21 young people. Monocular and binocular acuities were measured using a multiple-E optotype test. Binocular ratios, defined as the better-eye acuity divided by the binocular acuity, were calculated. We also measured eye dominance during rivalry (proportion of time the participants reported perceiving the input to each eye) and rivalry rates (number of alternations per minute). The results showed that while overall binocular ratios were similar for the three groups, the frequency distributions of people who experienced inhibition, equality or summation were different for the young and AMD groups. In the rivalry test, patients experienced more piecemeal perception than the elderly and young controls, but time dominance from the better-seeing eye was comparable for the three groups. Rivalry rates decreased with age and further with pathology. Moreover, rivalry time dominance of the worse-seeing eye was negatively correlated with interocular acuity differences for the AMD group.

Reading training with threshold stimuli in people with central vision loss: a feasibility study.

Purpose To evaluate the effectiveness of a perceptual learning technique for improving reading performance of patients with central vision loss and to explore whether this learning generalizes to other visual functions. Methods Ten patients with central vision loss were trained binocularly, in four consecutive sessions, with serially presented words printed at each patient’s reading acuity limit. Patients read 10 blocks of 100 words in each session. They were encouraged to read the whole word and were discouraged to read letter by letter. Assessment sessions before and after training measured fixation stability, monocular and binocular visual acuity, as well as reading acuity, critical print size, and maximum reading speed with continuous text. Another six patients with central vision loss were included in a test-retest control group and were tested twice, 1 week apart, with no intervention. Results The average time required to read a block of trials decreased significantly with each training session. After training, continuous text reading improved in terms of reading acuity (p = 0.017) and maximum reading speed (p = 0.01), but critical print size did not change. Binocular acuity improved significantly from an average of 0.54 logMAR before training to 0.44 logMAR after training. Binocular ratio (better eye acuity/binocular acuity) increased from an average of 1.0 before training to 1.17 after training. There was a 62% improvement in fixation stability in the better eye and 58% in the worse eye. There were no changes in the outcome measures for the test-retest control group. Conclusions The technique described in this article can be used for vision rehabilitation of patients with central vision loss. When training is done with size threshold stimuli, learning generalizes to visual acuity, continuous text reading, and fixation stability.

Courier: a better font for reading with age-related macular degeneration

OBJECTIVE This study examines the reading performance of patients with age-related macular degeneration (AMD) using 4 readily available fonts. DESIGN Experimental study. PARTICIPANTS Twenty-four patients with bilateral AMD participated. METHODS Reading performance (reading acuity, critical print size, and maximum reading speed) was measured for all patients, using 4 versions of the MNRead charts. These charts were printed in the following fonts: Times New Roman (serif, proportionally spaced), Arial (sans serif, proportionally spaced), Courier (serif, mono spaced), and Andale Mono (sans serif, mono spaced). RESULTS Reading acuity was significantly better on the Courier chart (0.58±0.21 logMAR) and significantly worse on the Arial chart (0.69±0.20 logMAR) than on any of the other charts (P<0.05). A larger proportion of patients were able to read≥1 sentences on the Courier chart than on any of the other charts. Reading speed dropped below the limit for fluent reading first with the Arial chart. There was no difference in maximum reading speed with the 4 fonts, and differences in critical print size failed to reach significance (P = 0.052). CONCLUSIONS Font has an effect on the reading performance of patients with AMD at print sizes close to their reading acuity. Courier was the most advantageous and Arial the worst font for reading smaller print. This is contrary to the advice given by agencies for the blind.

Fixation Patterns in Maculopathy: From Binocular to Monocular Viewing

Purpose. The goal of this study was to explore binocular coordination during fixation in patients with age-related macular degeneration (AMD) and to investigate whether there is a shift in eye position when the viewing condition changes from binocular to monocular. Methods. Sixteen people with normal vision and 12 patients with AMD were asked to look at a 3 deg fixation target with both eyes and with each eye individually while the fellow eye was covered by an infrared filter. Fixational eye movements were recorded for both eyes with an EyeLink eye-tracker in all conditions. The shift in eye position at the end of every fixation period was calculated for each eye. Results. All people with normal vision as well as the majority of patients had good binocular coordination during fixation in the binocular viewing condition. When the viewing condition changed from binocular to monocular, three patients (25%) had atypical shifts in their eye position. The shift was related to (1) loss of fixational control when the better eye was covered and the worse eye viewed the target or (2) a slow drift of the viewing eye that was associated with a large phoria in the covered eye. Conclusions. Patients with AMD have good binocular ocular motor coordination during fixation. A change in viewing condition from binocular to monocular can lead to disturbances in ocular motor control for some patients, especially in the worse eye.

Binocular function in patients with age-related macular degeneration: a review

Normally sighted observers typically benefit from binocular viewing when monocular sensitivities are equivalent. Age-related macular degeneration (AMD) not only destroys the foveal vision, however, but it also affects the 2 eyes unequally, providing grounds for impairment of binocular function. The aim of the present article is to provide a review of the current research on the effect of AMD on binocular vision. The main findings to date reveal that a high proportion of patients show characteristics of binocular contrast inhibition at low and medium spatial frequencies. Yet binocular acuity gain is not different from that of age-matched control participants without AMD. Additional findings show that rivalry processes are severely disrupted in patients with AMD. The effects of the disease on other binocular functions have yet to be explored. Knowledge of binocular function in AMD may one day help clinicians decide on the most appropriate management and rehabilitation techniques.