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Naoko Kato, Kazuno Negishi, Megumi Saiki, Kazuo Tsubota; Analysis of Predictors of Keratoconus Progression. Invest. Ophthalmol. Vis. Sci. 2014;55(13):4208.
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© ARVO (1962-2015); The Authors (2016-present)
Keratoconus is a congenital, progressive, ecstatic disease of the cornea. However, the mechanism of exacerbation is unclear. We retrospectively analyzed the characteristics of keratoconus patients to identify predictors of disease progression.
This study retrospectively analyzed 55 eyes of 35 patients (10 females and 25 males; age, 25.3±8.0 years) with keratoconus, who were followed for at least 6 months at our institute. In addition to standard ophthalmic examinations, we investigated the change in manifest refraction (spherical equivalents [SE] and cylinder power [Cyl]), steepest keratometric value (Ks), and thinnest corneal thickness (TCT). We also asked the age at which the patients were diagnosed with keratoconus. We defined progression as a decrease of more than 0.5 diopters per year (D/Y) for SE and increases of 0.5 D/Y for Cyl and Ks. We assigned progression scores from 0 to 3 as follows: 0, no progression observed for SE, Cyl, and Ks; 1, one of the factors progressed; 2, two factors progressed; and 3, all three factors progressed.
The age at diagnosis ranged from 14 to 41 years. At the first visit, SE, Cyl, Ks, and TCT were -4.41±4.24 D, -3.05±2.01 D, 50.42±7.25 D, and 451.7 ± 62.1 µm, respectively. SE progressed - 0.95 ± 5.93 D/Y, Cyl increased 0.44 ± 3.07 D/Y, the steepest K-value increased 0.44 ± 3.07 D/Y, and the TCT decreased 4.45 ± 18.08 µm per year. Spearman’s rank correlation test showed that the rates of change of SE, Cyl, and the progression score were correlated with the change in TCT (ρ = 0.3375, 0.3816, and -0.331; p = 0.0165, -0.0063, and 0.0189, respectively). Ks was correlated with the rate of change of Cyl (ρ = 0.3012, p = 0.0269). The rate of change of Ks was correlated with patient age at the first visit (ρ = -0.2845, p = 0.039).
A thin, steep cornea may help to predict the progression of keratoconus. Particularly, the decrease in corneal thickness is an important indicator of progression; however, patient age could be a secondary factor.
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