Elsevier

Ophthalmology

Volume 114, Issue 9, September 2007, Pages 1728-1735
Ophthalmology

Original Article
Cone- and Rod-Mediated Dark Adaptation Impairment in Age-Related Maculopathy

https://doi.org/10.1016/j.ophtha.2006.12.023Get rights and content

Objective

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

Design

Cross-sectional.

Participants

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° 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]).

Main Outcome Measures

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° in the inferior field on the vertical meridian are characteristic of ARM even in its early phases.

Section snippets

Materials and Methods

This study was approved by the institutional review board of the University of Alabama at Birmingham. Informed consent was obtained from all participants after the nature and possible consequences of the study were explained. Participants were recruited from the comprehensive ophthalmology and retina services of the Department of Ophthalmology, University of Alabama at Birmingham, based on clinic patients seen over a 14-month period in 2003 to 2004. Eligibility criteria were at least 50 years

Results

Table 1 provides demographic and VA information for participants. There were small differences in age among the 4 groups that were statistically significant (P = 0.0048), so comparisons of variables among groups were adjusted for age. There were slightly more females than males in most groups, and groups were predominantly white, of non-Hispanic origin. As expected, the old normal participants had the best VA, with increasingly worse VA with increased severity of ARM.

Table 2 displays dark

Discussion

When cone- and rod-mediated dark adaptation is measured in the parafovea in persons with early ARM, rod-mediated parameters, but not cone-mediated parameters, exhibit abnormalities. Increasingly severe ARM from early to advanced disease as defined by a standardized fundus grading scale was associated with greater impairment in rod-mediated dark adaptation. Specifically, with increased disease severity the time point at which rod photoreceptors emerged as more sensitive than cones (rod–cone

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    Manuscript no. 2006-956.

    Research supported by the National Institutes of Health, Bethesda, Maryland (grant nos. R01-AG04212, R21-EY14071); Research to Prevent Blindness, Inc., New York, New York; and EyeSight Foundation of Alabama, Birmingham, Alabama. Dr Owsley is a Research to Prevent Blindness Senior Scientific Investigator.

    Drs Owsley and Jackson are patent designees on a dark adaptation testing technology based on this and other work.

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