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Jay W McLaren, Katrin Wacker, Katrina Kane, Sanjay V Patel; Corneal Optical Properties after Swelling by Contact Lens Wear in Fuchs Endothelial Dystrophy. Invest. Ophthalmol. Vis. Sci. 2016;57(12):1940.
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© 2017 Association for Research in Vision and Ophthalmology.
Patients with Fuchs endothelial corneal dystrophy (FECD) often have poor vision in the morning that improves throughout the day. This study examined corneal high-order aberrations and scatter as possible sources of poor vision during corneal swelling.
Twenty-one phakic eyes (21 patients) with FECD (grades 1 – 6, modified Krachmer scale) and 7 normal eyes (7 participants) were examined by Scheimpflug photography (Pentacam HR, Oculus). Central corneal thickness, high-order aberrations from anterior and posterior corneal surfaces, and backscatter in standardized scatter units (SU) from the anterior, mid, and posterior cornea were determined from the Scheimpflug images. A low-oxygen permeable contact lens was placed on the eye and after 2 hours of lid closure over the lens, the lens was removed and eye was reexamined. Scheimpflug photography was repeated at 0.5, 1, 2, and 3 hours. After lens removal, variables were compared to those before lens placement by using paired t-tests with Bonferroni adjustment.
Immediately after removing the contact lens, corneas were swollen by 54±13 µm (mean ± standard deviation) in FECD patients (p<0.001) and by 48 ± 11 µm in control subjects (p<0.001). In both groups, thickness recovered by 3 hours. Anterior corneal high-order aberrations (root-mean-square, 6 mm-diameter optical zone) in FECD patients (0.60±0.16 µm) decreased slightly after lens wear (0.52±0.14 µm, p<0.001) but did not change in control subjects (0.43±0.13 µm before to 0.42 ±0.08 µm after lens wear, p>0.9). Aberrations from the posterior corneal surface did not change in either group (p>0.19). Backscatter from the anterior cornea increased from 1520±185 SU before lens wear to 1914±238 SU after lens removal in FECD (p<0.001) and from 1345±80 SU to 1819±167 SU in control subjects (p=0.001), and recovered by 2 hours in both groups. Backscatter also increased in both groups in the mid-cornea (p≤0.02) but increased only in the FECD group in the posterior cornea (p=0.028 FECD, p>0.9 control).
Inducing corneal edema to simulate swelling after overnight lid closure increases corneal backscatter but not high-order aberrations. Subjective poor vision in the morning in FECD is more likely caused by scattered light rather than by aberrations, suggesting that these patients experience more disability glare than decreased acuity in the morning.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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