Abstract
Introduction: :
Abstract:Reproducible measurement of the corneal geometry is crucial for exact modeling of the imaging properties of the human eye. Common corneal topographers provide only information about the anterior corneal surface, whereas data about the posterior surface are mostly unrecorded. Other devices, such as the Oculus PentaCam (PC) based on Scheimpflug principle are capable of measuring the corneal architecture by measuring front and back surface and corneal thickness. The purpose of this study was to determine the repeatability of results recorded with the PC.
Methods: :
We enrolled 14 eyes of 14 patients in an age between 13 and 74 years (46.68 ± 21.66 years) without notable pathologies or surgery in the past. A sequence of 5 measurements per eye was acquired using the PC with realigning the patient’s head before each measurement. In addition measurements with an autorefractor (Nidek AR-660A) and a Zeiss IOLMaster were performed. The anterior and posterior corneal radii and eccentricities were extracted from the PC for each measurement and the mean and standard deviation (SD) were calculated along with the SD for each measurements sequence.
Results: :
The dataset included 14 eyes with an average refraction of 0.60 ± 1.09 D/-1.60 ± 1.56 D. Corneal radii in mm were: Ra1 = 7.9996 ± 0.2745 (7.55 to 8.48); Ra2 = 7.77604 ± 0.2820 (7.17 to 8.15) for the anterior and RP1 = 6.6214 ± 0.3104 (6.09 to 7.15); RP2 = 6.2371 ± 0.3377 (5.67 to 6.86) for the posterior surface. Eccentricity was Ea = 0.2413 ± 0.3475 (-0.53 to 0.64) for the anterior and EP = 0.2803 ± 0.4797 (-0.68 to 0.92) for the posterior surface. Mean standard deviations for the 5 measurements were SDRA1 = 0.0395; SDRA2 = 0.0269; SDEA = 0.0976; SDRP1 = 0.0515; SDRP2 = 0.0433; SDEP = 0.0909. The anterior radii measured with the PC correlated significantly with the radii measured with the IOLMaster (R > 0.8; p < 0.001). There was no significant correlation between anterior and posterior radii (R < 0.3; p > 0.3).
Conclusions: :
The PentaCam provided accurate measurement results within a non-pathologic range of corneal radii. The repeatability for the anterior radii was better than ±0.040 mm/±0.23 D (±0.5 %) which is close to the manufacturer specification of ±0.2 D; repeatability for the posterior radii was better than ±0.052 mm/±0.047 D (±0.8 %). The repeatabilities for anterior and posterior eccentricity were ±0.0976 for the anterior and ±0.0909 for the posterior surface.
Keywords: topography • anterior segment