Abstract
Purpose: :
Previous studies suggest that the rod photoreceptors are more affected than the cones in age-related maculopathy (ARM).[1-3] However, it is unclear whether rod- or cone-mediated functional change in these patients precedes identifiable changes shown by in vivo imaging techniques, such as SD-OCT. In this study, we explore the relationship between local rod- and cone- mediated perimetric sensitivity and local thickness in the outer retina in senior patients with intermediate size drusen.
Methods: :
Rod- and cone-mediated sensitivities were measured from 37 loci in the central 12° using a modified fundus perimeter (MP-1S, Nidek Technologies). The dynamic range of test stimulus intensities was 0-40 dB for rods and 0-30 dB for cones. Test locations were registered with SD-OCT scans by importing infrared images (Spectralis HRA+OCT) into the MP-1S. Averaged thickness of the outer segment plus (OS+) layer (measured from distal border of retinal pigment epithelium/Bruch’s membrane and choroid to the boundary between photoreceptor inner and outer segments) was calculated for corresponding areas of each test spot (0.86° in diameter). A computer program aided manual segmentation and calculated OS+ thickness. Results from 3 senior patients with intermediate size drusen (78 ± 8 years, mean ± SD) were compared to those from 7 individuals with normal vision (64 ± 9 years, mean ± SD). All patients had best-corrected visual acuity of 20/32 or better (0.1 ± 0.1 logMAR, mean ± SD).
Results: :
All 3 patients showed greater loss of rod- than cone-mediated sensitivity. For patient A (age 74 yrs), OS+ thickness across 37 loci averaged 3.5% less than mean normal (p less than 0.05). Average cone-mediated fundus perimetric sensitivity was reduced 1.6 dB, and rod-mediated fundus perimetric sensitivity was reduced 4.8 dB. In patient B, (74 yrs) and patient C (87 yrs), average OS+ thickness was comparable to normal (p larger than 0.15). Cone-mediated fundus perimetric sensitivities were reduced 2.9 dB and 6.3 dB, respectively. However, rod-mediated fundus perimetric sensitivities were reduced 10.8 dB and 11.9 dB, respectively.
Conclusions: :
Preliminary results in patients with intermediate size drusen suggest that the change in outer segment thickness is less than expected based upon the loss in cone- or rod-mediated perimetric sensitivity. 1. Curcio Eye 2001, 376-383. 2, Curcio et al IOVS, 1236-1249; 3. Owsley et al Ophthal. 2001. 1196-1202.
Keywords: age-related macular degeneration • visual fields • imaging/image analysis: clinical