Blood flow in vessels supplying the eye in persons with degenerative myopia. Part I. Blood flow in the ophthalmic artery

Introduction
Mechanism of hemodynamic disturbances of blood circulation within the afferent vessels supplying the retina and the choroid, considered as one of main underlying causes of degenerative changes in myopic patients, is exceptionally likely, although not entirely proven. Purpose: To estimate the blood flow parameters in the ophthalmic artery of myopic subjects, depending on the extent and severity of progression of degenerative lesions observed in ocularfundi.

Material and methods
A prospective study included 70 myopic persons, aged from 18 to 79 years (44.9 ± 18.3) with the mean axial ocular length of 27.9 ± 5.37 mm. According to the extent and severity of degenerative lesion progression, patients were divided into 4 groups: I – no degenerative changes on the fundus (n = 32; K – 23, M – 9), II – myopic crescent (n = 20; K – 14, M – 6), III – retinal thinning accompanying the myopic crescent (n = 8; K – 6, M – 2), IV – extensive chorioretinal atrophy in the fundus (n = 10; K – 7, M – 3). Using colour Doppler ultrasonography (Aplio SSA Toshiba, frequency of the head of 12 MHz) the following parameters of the blood flow in the opthalmic artery were determined: the maximum (Vmax), minimal (Vmin) and mean (Vm) velocity, resistive index (RI) as well as pulsation index (PI). Differences were analysed statistically (the variance analysis and the Spearman’s rank correlation coefficient). P < 0.05 was assumed as statistically significant.

Results
In groups I and II blood flow parameters were comparable. In group III Vmax, Vmin and Vm were lower than in groups I and II. However, an increase in these parameters was shown in group IV. The PI remained on the comparable level, and the RI across all the study groups. The observed differences were not statistically significant.

Conclusions
The severity of degenerative retinal change progression at different stages of myopia is related to the blood flow in the ophthalmic artery, although these associations are not statistically significant. Blood flow discrepancies between the right and left artery, resulting from anatomical asymmetries, does not seem to be significant for the development of degenerative changes.