Axial Length and White to White Corneal Diameter in Eyes with Keratoconus

Abstract Objective To study the axial length (AL) and white to white (WTW) corneal diameter in keratoconus (KC) eyes and compare them to normal eyes. Methods Sixty-three eyes of 53 patients were included in this cross-sectional observational study divided into KC group comprised of 28 eyes of 18 patients and control group comprised of 35 eyes of 35 patients based on clinical and tomographic findings. All subjects were examined using rotating Scheimpflug corneal tomography (Pentacam HR; Oculyzer II) for central corneal thickness (CCT), thinnest corneal thickness (TCT), keratometric values, anterior chamber depth (ACD) and lens thickness, and by optical biometry (IOLMaster 500) for axial length (AL) measurements. Vitreous cavity length (VCL) was calculated by subtracting the values of CCT, ACD (internal), and lens thickness from the AL. White to white (WTW) corneal diameter was measured using Placido-based tomography (Topolyzer VARIO). Results The mean age was 31.27±8.65 years(30.39 ± 9.31) in the KC group and .(31.74 ± 8.38) in the non KC group. The KC group included 28 eyes their mean spherical equivalent (SE) was -3.16 ± 2.42 and the control group 35 healthy eyes including 23 ametropic eyes with mean spherical equivalent (SE) (-3.95±4.50 D) and 12 emmetropic eyes with mean SE (-0.19±0.40 D). The mean VCL was significantly greater in normal eyes (17.45 ±1.34 mm) compared with KC (16.77±1.18 mm) (P = 0.037), while the mean ACD (internal) was significantly greater in KC eyes compared to normal (P = 0.020) and the lens thickness showed no statistically significant difference. The greater VCL in the normal group was compensated by the greater ACD in the KC group causing the total AL to have no statistically significant difference (normal eyes =24.44 ±1.38 mm and KC eyes= 24.21 ±1.31 mm) (P = 0.513). There was no statistically significant difference in the WTW corneal diameter between KC and normal eyes (11.81 ±0.35 mm in the normal group compared to 11.79 ±0.35 mm in the KC group) (P = 0.835). Conclusion VCL was significantly greater in normal eyes compared with those eyes with KC. AL and WTW showed no difference between the two groups.