Visual acuity and fixation characteristics in age-related macular degeneration. 2007

Isabel Cacho, and Christine M Dickinson, and Barnaby C Reeves, and Robert A Harper
Faculty of Life Sciences, Moffat Building, The University of Manchester, Manchester, UK. i.cacho@manchester.ac.uk

OBJECTIVE To compare "single letter" (SL) acuity, "crowded letter" (CL) acuity, and "repeated letter" (RL) acuity for patients with age-related macular degeneration (AMD) and investigate if differences between these visual acuities are associated with fixation characteristics. METHODS A total of 243 patients with AMD had their best-corrected visual acuity measured on an ETDRS chart. SL, CL, and RL acuities were measured using Landolt C targets on a monitor. Fifty-degree-field red-free fundus photographs were taken and a static target was used to calculate the Preferred Retinal Locus (PRL) distance and direction from the fovea. Quality of fixation (consistency and oculomotor response) was also assessed using a fundus camera and a dynamic target. RESULTS RL acuity was almost always better than CL acuity and SL acuity was almost always better than CL acuity. The mean (+/-SD) RL-CL and SL-CL acuity differences were -0.13 (+/-0.15) logMAR and -0.11 (+/-0.13) logMAR respectively. The median PRL distance was 3.73 degrees and the preferred retinal areas for the location of the PRL were the left (left quadrant of visual field; 39.5% of cases) and superior (inferior quadrant of visual field; 25.4%). Visual acuity was significantly associated with PRL distance but PRL distance only explained 10% of the variation in visual acuity. PRL distance was found to be a significant but weak predictor of the SL-CL acuity difference but fixation quality was not a good predictor of the RL-CL acuity difference. CONCLUSIONS Although the acuity measured under different stimulus conditions varies, the absolute differences are small. This suggests that these techniques would not be helpful in determining fixation characteristics, or predicting the outcome of rehabilitation in individual patients with AMD.

UI MeSH Term Description Entries
D008268 Macular Degeneration Degenerative changes in the RETINA usually of older adults which results in a loss of vision in the center of the visual field (the MACULA LUTEA) because of damage to the retina. It occurs in dry and wet forms. Maculopathy,Maculopathy, Age-Related,Age-Related Macular Degeneration,Age-Related Maculopathies,Age-Related Maculopathy,Macular Degeneration, Age-Related,Macular Dystrophy,Maculopathies, Age-Related,Age Related Macular Degeneration,Age Related Maculopathies,Age Related Maculopathy,Age-Related Macular Degenerations,Degeneration, Macular,Dystrophy, Macular,Macular Degeneration, Age Related,Macular Degenerations,Macular Dystrophies,Maculopathies,Maculopathy, Age Related
D008297 Male Males
D008875 Middle Aged An adult aged 45 - 64 years. Middle Age
D011379 Prognosis A prediction of the probable outcome of a disease based on a individual's condition and the usual course of the disease as seen in similar situations. Prognostic Factor,Prognostic Factors,Factor, Prognostic,Factors, Prognostic,Prognoses
D005260 Female Females
D005403 Fixation, Ocular Positioning and accommodation of eyes that allows the image to be brought into place on the FOVEA CENTRALIS of each eye. Focusing, Ocular,Ocular Fixation,Eye Gaze,Eye Gazes,Gaze, Eye,Gazes, Eye,Ocular Focusing
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000368 Aged A person 65 years of age or older. For a person older than 79 years, AGED, 80 AND OVER is available. Elderly
D000369 Aged, 80 and over Persons 80 years of age and older. Oldest Old
D012720 Severity of Illness Index Levels within a diagnostic group which are established by various measurement criteria applied to the seriousness of a patient's disorder. Illness Index Severities,Illness Index Severity

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