Офтальмохирургия (Dec 2017)
OPTICAL COHERENCE TOMOGRAPHY IN PATIENTS WITH REFRACTIVE ERRORS. Part 1: The thickness of the peripapillary retinal nerve fiber layer
Abstract
Purpose. To develop an available method to correct the influence of the optical system of long or short eyes on the thickness of peripapillary retinal nerve fiber layer (pRNFL), measured using the optical coherence tomography (OCT).Material and methods. The study involved 46 patients (46 eyes) aged 18 to 40 years, with moderate and high myopia and the best corrected visual acuity (BCVA) not lower than 0.8, as well as 53 healthy persons with emmetropia of the same sex and age (comparative group) and 117 healthy emmetropic individuals aged 41-84 years (group «over 40 years old»). The OCT was performed using a Cirrus HD-OCT device (Carl Zeiss Meditec). An analysis of the literature was conducted for the selection of the optimal method to correct the influence of the eye optical system on the pRNFL parameters.Results. Taking into account the literature data, Littmann’s method (1982), modified by Bennett et al. (1994), was chosen for a correction of the influence of the ocular optical system on the pRNFL. The method was modified and adopted to the emmetropic eye with a 23.5 mm axial length. The pRNFL normative data were defined for such eyes. Despite the high visual acuity, the patients with myopia showed a significant decrease in the thickness of pRNFL (83.9±5.4 µm) compared to the healthy individuals (96.1±8.2 µm, P<0.000) and the correlation of the pRNFL thickness with the axial length of the eye (r=-0.394; P=0.007).After the correction by the suggested modified method, the average RNFL thickness (96.0±5.8 µm) did not differ from the healthy individuals, and there was no correlation with the axial length of the eye. A table was developed that allows to correct the pRNFL thickness taking into account the axial length of the eye.Conclusion. The OCT devices of most manufacturers do not consider the effect of refractive errors, especially in case of high degree, on quantitative measurements of structures of the eye fundus. For a correct interpretation of pRNFL measurements in these patients, the existing methods of calculation were improved and an original table was proposed, which provides a quick assessment of the obtained results.
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