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Yuquan Wen, Gina M. Mitzel, Jane Gilmore, Karl G. Csaky, Donald C. Hood, Yi-Zhong Wang, David G. Birch; Rod-mediated Sensitivity Loss Precedes SD-OCT Thickness Changes in the Outer Retina of Senior Patients with Intermediate Size Drusen. Invest. Ophthalmol. Vis. Sci. 2012;53(14):2906.
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© ARVO (1962-2015); The Authors (2016-present)
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.
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).
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.
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.
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