Characteristics of visual loss by scanning laser ophthalmoscope microperimetry in eyes with subfoveal choroidal neovascularization secondary to age-related macular degeneration.

Purpose: To evaluate the effects of subfoveal choroidal neovascularization secondary to age-related macular degeneration on functional parameters obtained by scanning laser ophthalmoscope microperimetry.
Design: Retrospective observational case series and cross-sectional study.
Methods: At the Doheny Retina Institute and Wilmer Eye Institute a consecutive series of 179 eyes of 175 patients with subfoveal choroidal neovascularization secondary to age-related macular degeneration was studied. The onset of visual symptoms, best-corrected visual acuity, fluorescein angiography, evaluation of fundus microperimetry and fixation pattern using the Rodenstock scanning laser ophthalmoscope were obtained for each patient. The main outcome measures were central retinal sensitivity and fixation pattern (fixation location and fixation stability) in eyes with subfoveal choroidal neovascularization and their relationship to the length of disease, type and characteristics of choroidal neovascularization, and visual acuity.
Results: Of 179 eyes, 135 (75%) had central fixation, 27 (15%) had poor central fixation, and 17 (9%) had predominantly eccentric fixation. Seventy-six eyes (42%) had stable fixation, 70 eyes (39%) had relatively unstable fixation, and 33 eyes (18%) had unstable fixation. In 50 eyes (28%) a dense central scotoma was noted. Eighty-nine of 100 eyes (89%) with length of symptoms of less than 3 months had predominantly central fixation and 58 (58%) had stable fixation; 14 of 34 eyes (41%) with length of symptoms of more than 6 months had predominantly central fixation, and 5 eyes (15%) had stable fixation. In 15 eyes of patients who elected not to receive treatment, successive scanning laser ophthalmoscope microperimetry were obtained over time (follow-up of 18 months after onset of symptoms). Three months or less after the onset of symptoms, 13 eyes (87.7%) had predominantly central fixation and 9 eyes (60%) had stable fixation. More than 3 months and 6 months or less after the onset of symptoms, 10 eyes (66.7%) had predominantly central fixation and 7 eyes (46.7%) had stable fixation. This trend was further demonstrated in eyes more than 6 months after the onset of symptoms.
Conclusions: We conclude that the sequence of events leading to visual function deterioration appears to involve an initial mild decrease in central retinal sensitivity and visual acuity followed by progressive fixation instability and, ultimately, development of an absolute central scotoma with totally eccentric fixation. Increased length of disease is associated with worse fixation pattern and retinal sensitivity deterioration as assessed by scanning laser ophthalmoscope microperimetry. A better understanding of the characteristics of visual loss assessed by fixation pattern evaluation and microperimetry in age-related macular degeneration may help optimize timing, patient selection, and treatment options in eyes with this condition.