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S. Haque, L. Jones, T. Simpson; Mapping Corneal & Epithelial Thickness Using OCT: Comparing Neophytes, RGP Lens Wearers & Keratoconics . Invest. Ophthalmol. Vis. Sci. 2006;47(13):1311.
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© ARVO (1962-2015); The Authors (2016-present)
To compare corneal and epithelial thickness along a 10mm diameter section in 8 meridians, using Optical Coherence Tomography (OCT) and to compare these measurements between non–lens wearers (NLW), RGP lens wearers (RGP) and RGP–wearing keratoconics (KC).
Both eyes of 60 subjects were measured (20 NLW – 9F:11M; 27.6 ± 5.9yrs, 20 RGP – 20F; 23.9 ± 7.6yrs, and 20 KC – 7F:13M; 32.4 ± 8.1yrs). Average duration of RGP lens wear was 9.1 ± 4.1yrs and average duration since KC diagnosis was 8.4 ± 7.6yrs. A customized fixation target employing LEDs in 8 meridians was attached to the OCT and corneal images obtained. Raw OCT scans were analysed to yield values for corneal and epithelial thickness and colour–coded maps were compiled.
Central corneal thickness (CCT) was thinnest in KC (447 ± 68um) and similar between RGP (518 ± 32um; pKC<0.05) and NLW (517 ± 21um) [pKC<0.05 NLW pRGP>0.05]. Peripheral corneal thickness (PCT) in NLW was thickest in the superior temporal (ST) and thinnest in the inferior (I) regions (STthickest vs Ithinnest p<0.05). Overall PCT was thinner in KC compared to NLW and RGP groups (both p<0.05). Central epithelial thickness (CET) was thinnest in KC (44 ± 6um), followed by RGP (50 ± 4um), then NLW (54 ± 2um) (pKC<0.05 NLW pRGP>0.05). CET in the KC group was significantly thinner than in the RGP group (p<0.05). In the NLW group, peripheral epithelial thickness (PET) was thicker (63 ± 5um) than central (p<0.05) and was thickest in the superior (S) region and thinnest in the inferior (I) region (Sthickest vs Ithinnest p<0.05). PET was also thicker than central in RGP (64 ± 6um; p<0.05) and KC groups (60 ± 6um; p<0.05). KC epithelium was thinnest in the inferior temporal meridian (42 ± 5um).
Thickness of the normal cornea and epithelium was greatest in the superior region. In all groups, the inferior cornea and epithelium was thinnest, to a greater extent in the keratoconic group, as expected. The central epithelium in RGP wearers was an insignificant 4um thinner than normal, suggesting that the epithelial thinning seen in keratoconus is unrelated to RGP lens–wear.
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