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First Author: F.Esteves PORTUGAL
Co Author(s): F. Rodrigues C. Ferreira B. Fontes R. Ambrósio Jr J. Borges
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The aim of this study was to evaluate the sensitivity, specificity and accuracy of some tomographic parameters and corneal biomechanics in differentiating healthy and keratoconus eyes.
Ophthalmology department of CHEDV, Feira
Patients with keratoconus and healthy subjects underwent complete ophthalmic examination,tomographic evaluation of the anterior segment (OCULUS Pentacam ® Oculus Inc) and evaluation of corneal biomechanics (Ocular Response Analyzer ® (ORA) - Reichert Ophthalmic Instruments). The following data were compared between the two populations: average central keratometry (Km), corneal astigmatism (ASTC), central corneal thickness (CCT), anterior chamber depth (ACD), corneal hysteresis (CH) and corneal resistance factor (CRF). For each parameter, we evaluated the differences between groups. We constructed a ROC (receiver operating characteristic) curve to determine for each parameter the cutoff with high sensitivity and specificity in differentiating healthy eyes and keratoconus.
We evaluated 233 eyes of 122 patients with keratoconus (71 males and 51 females) and 270 eyes of 119 healthy subjects (48 males and 71 females). The average values of all parameters were statistically significant between the two groups. The keratoconus group had a higher mean value of Km, ASTC and ACD, while the remaining parameters had a lower mean value than the control group. In ROC curve analysis, the parameters with higher sensitivity were the ACD(sensitivity 78%, cut-off 3.03 mm) and ASTC (sensitivity 74.2%, cutoff 1.95 D). The parameters with the highest specificity were Km (specificity 94.4%, cutoff 45.95 D) and ASTC (specificity 93.7%,cutoff 1.95 D). The ASTC was the parameter with the highest accuracy (84.5%).
The parameters we studied showed a low sensitivity in differentiating healthy eyes and keratoconus. The Km and ASTC, with cutoffs of 45.95 D and 1.95 D, respectively, showed a high specificity in that distinction.