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Qienyuan Zhou, Jack L. Weiss, Robert Brass, Alison N. Gordon, Kelly A. Soules; Comparison Of Corneal Power And Thickness Measured With RTvue OCT In Normal Eyes, Post-refractive Surgery Eyes, And Keratoconus Eyes. Invest. Ophthalmol. Vis. Sci. 2011;52(14):4180.
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© ARVO (1962-2015); The Authors (2016-present)
To compare central corneal power (CCP), central corneal curvatures (CCC_A & CCC_P), central corneal thickness (CCT) and thinnest thickness (ThinestCT) measured with RTVue OCT in normal eyes, normal post-refractive surgery eyes (Post-LASIK/PRK), and keratoconus (KCN) eyes, including Forme frusta keratoconus (FFK) and Pellucid Marginal Degeneration (PMD).
Study subjects were recruited following an IRB approved protocol with informed consent and enrolled into 3 groups: normal group (no corneal pathology and no prior surgery), Post-laser LASIK/PRK group (prior LASIK or PRK at least one month earlier and no corneal pathology), and a KCN group (clinical diagnosis of keratoconus). For each eye, 3 repeated CCP scans were obtained using RTVue OCT (Optovue Inc., Fremont, CA). Corneal parameters were calculated with RTVue software; mean value calculated per parameter per eye. The measurements were compared between KCN and other two groups using t test.
There are 169 normal eyes, 82 normal Post-LASIK/PRK eyes, and 72 KCN (including 19 FFK and 4 PMD) eyes in the study, with age distribution (mean±SD) of 54.9±18.2, 41.8±12.6, and 46.0±13.0 respectively. Between the KCN group and the normal group, there is significant difference in CCP (Δ=2.67D, p<0.001), CCC_A (Δ=-0.385 mm, p<0.001), CCC_P (Δ=-0.260 mm, p=0.04), CCT (Δ=-51.2µm, p<0.001), ThinestCT (Δ=-95.0µm, p<0.001), and ThinestCT_Y (Δ=-0.76mm, p<0.001), and non-significant difference in ThinestCT_X (Δ=0.13mm, p=0.16). Between the KCN group and the Post_LASIK/PRK group, there is significant difference in CCP (Δ=5.10D, p<0.001), CCC_A (Δ=-0.788 mm, p<0.001), CCC_P (Δ=-0.260 mm, p=0.04), ThinestCT (Δ=-45.7µm, p<0.001), and ThinestCT_Y (Δ=-0.83mm, p<0.001), and non-significant difference in CCT (Δ=-1.9, p>0.5) and ThinestCT_X (Δ=0.16mm, p=0.16).
Central corneal power and curvatures are significantly higher in the KCN group than the two normal groups. Corneal thickness is significantly thinner in the KCN group compared to the normal group without prior refractive surgery. The thinnest corneal location is lower vertically in KCN eyes than normal eyes. Corneal power, curvatures, and thickness measurements as provided by OCT may be used together to assist KCN detection.
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