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Yvonne Wang, Daniel L Kornberg, Ryan M St Clair, Irma Muhic, Michelle Lee, Kimberly C Sippel, Priyanka Sood, Jessica B Ciralsky, Ana G Alzaga Fernandez, Mark I Rosenblatt; A Fluid-Filled Scleral Lens Alters Corneal Nerve Structure and Function. Invest. Ophthalmol. Vis. Sci. 2014;55(13):4709.
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To determine if long-term wear of a fluid-filled scleral lens alters basal tear production, corneal sensation, corneal nerve density and corneal nerve morphology in varying disease states.
Patients were recruited from the PROSE program at Weill Cornell Medical College. They were categorized under one of two disease states: 1) ectasia and irregular astigmatism or 2) ocular surface disease (OSD). Measurements were taken before and after long-term PROSE wear, defined as at least 60 days of wear (range: 61-190 days) for a minimum of 8 hours a day. Tear production was measured by Schirmer’s type I with anesthesia (9 patients, 17 eyes). Central corneal sensation was measured using a Cochet-Bonnet aesthesiometer (14 patients, 20 eyes). Corneal nerve images were obtained using a ConfoScan 4 (Nidek) confocal scanning microscope. A single best image showing nerves in the sub-basal nerve plexus (12 patients, 21 eyes) and stromal nerves (12 patients, 19 eyes) was chosen from each exam and images were analyzed for stromal nerve trunk thickness and sub-basal corneal nerve length and tortuosity (NeuroLucida).
Tear production decreased in patients with ectasia/irregular astigmatism (21 mm to 10 mm, p<0.001), but did not change in patients with OSD (7.5 mm to 8.7 mm, p>0.5). Corneal sensation increased in the ectasia/irregular astigmatism group (45 mm to 52 mm, p = 0.01), but did not change in patients with OSD (45 mm to 49 mm, p>0.05). Sub-basal nerve density significantly decreased in the ectasia/irregular astigmatism group (6133 um/mm2 to 498 5 um/mm2, p<0.05), but was again unchanged in the OSD group (7002 um/mm2 to 6166 um/mm2, p>0.05). Neither stromal nerve thickness nor sub-basal nerve tortuosity significantly changed for both the ectasia/irregular astigmatism group and the OSD group.
Patients with ectasia or irregular astigmatism had significantly decreased basal tear production, increased corneal sensation and decreased sub-basal nerve density after long-term PROSE wear. Interestingly, patients with OSD did not show any changes in our measured parameters. One explanation is that patients with ectasia and irregular astigmatism have an intact lacrimal functional unit which responds to the chronic saline exposure provided by the fluid reservoir. However, patients with OSD have an inflammatory process disrupting the functional lacrimal unit which prevents it from adapting to environmental changes.
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