Purchase this article with an account.
Peter N. Dimitrov, Robyn H. Guymer, Andrew J. Zele, Andrew J. Anderson, Algis J. Vingrys; Measuring Rod and Cone Dynamics in Age-Related Maculopathy. Invest. Ophthalmol. Vis. Sci. 2008;49(1):55-65. doi: https://doi.org/10.1167/iovs.06-1048.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
purpose. A cathode-ray-tube (CRT) monitor–based technique was used to isolate clinically significant components of dark adaptation. The utility of the technique in identifying adaptation abnormalities in eyes with age-related maculopathy (ARM) is described.
methods. A CRT dark adaptometer was developed to assess cone and rod recovery after photopigment bleach. The following measures were obtained: cone recovery rate (R c; in decades per minute) and absolute threshold (Tf c; log candelas per square meter), rod recovery rate (R r; decades per minute), and rod–cone transition (rod–cone break [RCB], in minutes). 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 by using 5 young observers and was tested on 27 subjects with ARM in the study eye and 22 age-matched control subjects.
results. The parameters necessary for effective isolation of cone and early phase rod dark adaptation were a 2.6 ND filter (for a standard CRT monitor, 0.08–80 cd · m−2 luminance output); a 4° foveated, 200-ms, achromatic spot; ∼30% pigment bleaching; and a 30-minute test duration. These settings returned obvious rod and cone recovery curves in control and ARM eyes that were compatible with conventional test methods and identified 93% of participants with ARM 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 control subjects (R c, 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 minutes). The remaining eyes with ARM (n = 24) exhibited a significant delay in rod recovery (R r , 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 the control subjects (19.12 ± 5.17 minutes vs. 10.40 ± 2.49 minutes, P < 0.0001).
conclusions. The CRT dark-adaptation technique described in this article is an effective test for identifying abnormalities in cone and rod recovery. Slowed cone and rod recovery and a delayed RCB were evident in the eyes with ARM. The test method is potentially useful for clinical intervention trials in which ARM progression is monitored.
This PDF is available to Subscribers Only