Cone- and rod-mediated dark adaptation impairment in age-related maculopathy.
OBJECTIVE
To examine impairment in cone- versus rod-mediated dark adaptation in the parafovea of persons with age-related maculopathy (ARM).


METHODS
Cross-sectional.


METHODS
Older adults with ARM at various severity levels from early to advanced (n = 83) and in good retinal health (n = 43), as determined by stereo fundus photographs evaluated with the Age-Related Eye Disease Study severity scale.


METHODS
Dark adaptation, both cone- and rod-mediated components, was measured with a modified Humphrey Field Analyzer using a target located 12 degrees in the inferior visual field on the vertical meridian, after exposure to a 98% bleach. Information was collected on self-reported problems for activities at night or under dim illumination (Low Luminance Questionnaire [LLQ]) and for activities during daytime conditions (modified National Eye Institute Visual Function Questionnaire [NEI VFQ]).


METHODS
Cone- and rod-mediated parameters of dark adaptation.


RESULTS
Compared with older adults in normal retinal health, ARM patients had significant impairments in rod-mediated parameters of dark adaptation (rod-cone break, rod slope, rod sensitivity) (P<0.0001), which were increasingly abnormal as disease severity increased. Cone-mediated parameters (cone time constant and cone sensitivity) were not impaired. Low Luminance Questionnaire scores and NEI VFQ scores decreased with increased ARM severity (P = 0.0004 and P = 0.0005, respectively); the percent decrease in LLQ scores as a function of disease severity was larger in magnitude than the percent decrease in NEI VFQ scores.


CONCLUSIONS
Disturbances in rod-mediated but not cone-mediated dark adaptation in the parafovea at 12 degrees in the inferior field on the vertical meridian are characteristic of ARM even in its early phases.
Owsley
Cynthia
C
Department of Ophthalmology, School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama 35294-0009, USA. owsley@uab.edu
McGwin
Gerald
G
Jackson
Gregory R
GR
Kallies
Katherine
K
Clark
Mark
M
D000368:Aged; D003430:Cross-Sectional Studies; D003623:Dark Adaptation / Q000502:physiology*; D005260:Female; D006801:Humans; D008268:Macular Degeneration / Q000503:physiopathology*; D008297:Male; D010775:Photic Stimulation; D017949:Retinal Cone Photoreceptor Cells / Q000503:physiopathology*; D017948:Retinal Rod Photoreceptor Cells / Q000503:physiopathology*; D011795:Surveys and Questionnaires; D014785:Vision, Ocular; D014792:Visual Acuity; D058609:Visual Field Tests / Q000379:methods; D014794:Visual Fields