עובי הקרנית בחולי קרטוקונוס

Introduction

Central corneal thickness (CCT) measurement is an important procedure to evaluate and diagnose patients with KC. This study will compare CCT measurements using the Sirius (rotating Scheimpflug camera) with the VX120 (stationary Scheimpflug camera) on keratoconus (KC) patients.

Methods

Patients who were diagnosed with KC according to the standard criteria, participated in this study. Three measurements were taken with each instruments, by different examiners, in a random order. Visual acuity (Snellen) was measured, retinoscopy and slit lamp biomicroscopy were performed to detect clinical signs of the disease. T-test, Pearson correlation and Bland and Altman (1986) analyses were performed.

Result

13 KC patients participated in the study (22 eyes, range of 21-56, average age 34.07±10.86 years, K ave: 7.15±0.61mm). The average CCT using the Sirius was 477.62 ±51.82 µm and 521.54±47.68 µm with the VX120 The instruments showed good correlation, r=0.90 but yielded significantly different results, p<0.001).The average difference was 42.99±23.05µm. Bland & Altman analysis showed that all the data fall within two standard deviations of the average difference.

Conclusions

Despite the high correlation between the instruments, the average difference is clinically significant and has a high standard deviation. Therefore, the instruments cannot be used interchangeably for KC patients.