Corneal and Epithelial Thickness Changes After 4 Weeks of Overnight Corneal Refractive Therapy Lens Wear, Measured With Optical Coherence Tomography

Centre for Contact Lens Research, School of Optometry, University of Waterloo, Waterloo, Ontario, N2L 3G1 Canada.
Eye & Contact Lens Science & Clinical Practice (Impact Factor: 1.47). 11/2004; 30(4):189-93; discussion 205-6. DOI: 10.1097/01.ICL.0000140223.60892.16
Source: PubMed


To investigate thickness changes of the total cornea and epithelium across the horizontal corneal meridian after 4 weeks of overnight corneal refractive therapy (CRT) rigid contact lens (Paragon Vision Sciences, Mesa, AZ) wear.
Thirty subjects were fitted with CRT contact lenses (Dk/t = 67), which were worn overnight for 4 weeks. Corneal thickness was measured at nine locations along the horizontal meridian by using optical coherence tomography (OCT) before lens insertion in the evening. Corneal thickness was measured the next morning immediately after lens removal and 1, 3, 7, and 14 hours later. This was repeated on days 4, 10, and 28 of the study and then 3 days after discontinuing lens wear.
Twenty-three subjects completed the study. At lens removal on day 1, the central and paracentral cornea swelled by 4.9% and 6.2%, respectively (both P = 0.000). The central epithelium thinned by 7.3%, and the mid peripheral epithelium thickened by 13% (both P = 0.000). Corneal swelling recovered throughout the day, with most of the deswelling taking place within the first 3 hours after lens removal. Maximal central epithelial thinning reached 13.5% by day 4. Three days after the study completion, corneal and epithelial thickness had recovered to baseline values.
This study shows that CRT lenses induce differential overnight swelling across the cornea, with rapid deswelling during the day. Central epithelial thinning and paracentral thickening occurs, with recovery 3 days after discontinuation of lens wear.

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    • "The tear film hydraulic force underneath the lens has been described by Mountford (2004), and the effect of lid tension (Lieberman and Grierson, 2000; Ehrmann et al., 2001) through the contact lens has been hypothesized to induce squeeze pressure (Mountford, 2004) on central epithelial cells. The general effect of these forces and pressures to induce structural changes has been supported by histological (Matsubara et al., 2004; Choo et al., 2004) and morphological studies (Swarbrick et al., 1998; Alharbi and Swarbrick, 2003; Wang et al., 2003, 2004; Ladage et al., 2004; Haque et al., 2004). Morphological studies (Swarbrick et al., 1998; Wang et al., 2003; Alharbi and Swarbrick, 2003) have also indicated stromal involvement in corneal reshaping. "
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