DEGENERATIVE CHANGES OF THE CORNEAL NERVES IN PATIENTS WITH PRIMARY OPEN-ANGLE GLAUCOMA

PURPOSE: To evaluate the corneal nerves structure in patients with primary open-angle glaucoma (POAG).

METHODS: The study included 111 patients. The main group comprised 76 patients (148 eyes) aged 36 to 83 years (62.9Ѓ}2.3 years) with I-IV stages of POAG, control group consisted of 35 healthy volunteers (70 eyes) aged 38-76 years (65.3Ѓ}1.4 years) with normal IOP level and no POAG signs. Patient examination included visometry, biomicroscopy, ophthalmoscopy, gonioscopy, contour tonometry (Pascal), OCT (Zeiss Stratus 3000) and corneal confocal microscopy (HRT III, with Rostock Cornea Modul).

RESULTS: The following structural changes in the corneal nerves were revealed in POAG patients: a decreasing number of nerves, nerve fibers thinning and discontinuity. A quantitative assessment of the corneal nerves tortuosity degree was made by calculating the anisotropy coefficient of the corneal nerves directivity (KΔL). Mean KΔL in the control group was 2.78 (2.47; 3.57) (Me (Q1; Q3)), which significantly differed from the glaucoma group (p=0.0014), where mean KΔL was 2.51 (2.07; 3.16) (Me (Q1; Q3)). Significant differences in KΔL were obtained for different stages of glaucoma (p=0.0004), a moderate negative KΔL bond was detected with POAG stage (r=-0.41, p<0.001). Positive, though weak, correlation was established between KΔL and the following OCT parameters: Rim Cross Sectional Area (r=0.27, p=0.001), Rim Area (r=0.25, p=0.0032) (p<0.005), Rim Volume (r=0.23, p=0.01) and Avg. Thickness (r=0.29, p=0.00063) (p<0.001). The interocular asymmetry of the corneal nerves structure in patients with different glaucoma stages in pair eyes has been studied. The KΔL index asymmetry was calculated. It turned out that this index in the glaucoma group was higher than in the control group, with values in both groups showing a significant difference (p=0.00026). KΔL asymmetry index directly correlated with the divergence in POAG stages between the pair eyes.

CONCLUSION: The presence of structural changes in the corneal nerves layer and the increase in the severity of these changes depending on glaucoma stage, indicate that the dystrophic process in the cornea is a local manifestation of glaucomatous neurodegenerative process. This is best seen in the study of interocular asymmetry in patients with different glaucoma stages in pair eyes. This gives us a notion of universality of the neurodegenerative process in patients with POAG, and consequently, suggests that the study of corneal structures may have diagnostic value.

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