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Measuring rod and cone dynamics in age-related maculopathy

Dimitrov, Peter D., Guymer, Robyn H., Zele, Andrew J., Anderson, Andrew J., & Vingrys, Algis J. (2008) Measuring rod and cone dynamics in age-related maculopathy. Investigative Ophthalmology and Visual Science, 49, pp. 55-65.

Abstract

Purpose. We describe a cathode-ray-tube (CRT) monitor based technique that isolates clinically important components of dark adaptation. We also demonstrate the utility of the technique in identifying adaptation abnormalities in eyes with Age-Related Maculopathy (ARM). Methods. A CRT dark adaptometer was developed to assess cone and rod recovery following photopigment bleach. We considered the following measures: cone recovery rate (Rc; decades.min-1) and absolute threshold (Tfc; log cd.m-2), rod recovery rate (Rr; decades.min-1) and the rod-cone transition (rod-cone break; RCB; min). These components were isolated by appropriately selecting stimulus size, stimulus location, pigment bleach, and test duration, and by coupling the CRT with judiciously selected neutral density (ND) filters. The protocol was developed using 5 young observers and tested on 27 subjects with ARM in the study eye and 22 age-matched controls. Results. The parameters required to allow effective isolation of cone and early phase rod dark adaptation were: 2.6 ND filter (for a standard CRT monitor, 0.08-80 cd.m-2 luminance output); 4° foveated, 200 msec, achromatic spot; ~30% pigment bleach and 30 minutes test duration. These settings returned obvious rod and cone recovery curves in controls and ARM eyes that were compatible with conventional test methods and identified 93% of ARM participants as having delayed dynamics in at least one of the parameters. Cone recovery dynamics were significantly slower in the ARM group when compared with age-matched controls (Rc, 0.99±0.35 vs 2.63±0.61 decades.min-1, p<0.0001). Three of the 27 eyes with ARM did not achieve RCB during the allowed duration (30 mins). The remaining eyes with ARM (n=24) exhibited a significant delay in rod recovery (Rr , ARM, 0.16±0.03 vs controls, 0.22±0.02 decades.min-1, p<0.0001) and the average time to RCB (±SD) in the ARM group was significantly longer than in controls (19.12 ±5.17 min vs 10.40±2.49 min, p<0.0001). Conclusions. The CRT dark adaptation technique described in this paper is shown to be an effective test for identifying abnormalities in cone and rod recovery. Slowed cone and rod recovery and a delayed rod-cone break were evident in the eyes with ARM. Our test method is potentially useful for clinical intervention trials that need to monitor ARM progression.

Impact and interest:

30 citations in Scopus
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27 citations in Web of Science®

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ID Code: 10465
Item Type: Journal Article
Additional Information: For more information, please refer to the journal's website (see link) or contact the author.
Additional URLs:
ISSN: 0146-0404
Divisions: Current > QUT Faculties and Divisions > Faculty of Health
Current > Institutes > Institute of Health and Biomedical Innovation
Copyright Owner: Copyright 2008 Association for Research in Vision and Ophthalmology
Deposited On: 29 Oct 2007
Last Modified: 13 Nov 2012 08:47

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