Morphometric changes of optic nerve and retina in keratoconus patients similar to changes in glaucoma

The article contains optical coherence tomography (OCT) assessment of patients with different stages of keratoconus. OCT method has previously been successfully used for diagnostics and monitoring of the optic nerve head (ONH) and retina condition in glaucoma. The morphometric changes of the eye fundus in primary open-angle glaucoma have been studied and described in detail. However, the potential of OCT assessment of ONH and peripapillary retina in keratoconus patients has not been previously realized, which defines the scientific novelty and relevance of the present study.
PURPOSE: To study morphometric changes of ONH, peripapillary retina and ganglion cells complex (GCC) in keratoconus patients by means of optical coherence tomography.
METHODS: All keratoconus patients underwent standard ophthalmological examination. Morphometric parameters of the ONH and peripapillary thickness of the retinal nerve fiber layer (RNFL) were studied by means of OCT. The complex examination also included computer assisted corneal topography, corneal OCT, ultrasound biomicroscopy, endothelial microscopy and other research methods.
RESULTS: The average age of the surveyed keratoconus patients was 28.43±0.89 years. Non-corrected visual acuity (NCVA) amounted to 0.39±0.04 (ϭ=0.33), best corrected visual acuity (BCVA) — 0.58±0.04. The average value of the corneal thickness was 459.19±4.55 µm, which is 1.1-1.2 times less than normal values. The true intraocular pressure equaled 11.35±0.07 mm Hg. RNFL thickness in keratoconus patients was more than 3 times lower than in healthy individuals of similar age. Keratoconus patients of all stages manifested with optic nerve cup enlargement up to 0.73 which allowed suggesting that keratoconus occurs in people suffering from undifferentiated connective tissue dysplasia. Echocardiography revealed heart indices changes in 70.9% (22 of 31) of surveyed keratoconus patients. Triplex scanning of the extracranial parts of the brachiocephalic arteries (ACUSON S2000 ultrasound scanner) found vascular changes in 41.9% (13 out of 31) of keratoconus patients. Fundus changes similar to those found in glaucoma patients were regarded as manifestations of pseudoglaucomatous optic neuropathy development due to a systemic connective tissue deficiency. These findings led to a new understanding of keratoconus pathogenesis and changes in diagnostic and treatment tactics.
CONCLUSION: OCT helped reveal morphometric changes of the ONH and peripapillary retinal nerve fiber layer in patients with different keratoconus stages, which define the scientific novelty of this research and change the idea of keratoconus as a pathology constrained to the anterior eye segment. We believe that corneoscleral changes in keratoconus eyes are only “the tip of the iceberg”, while the pathological process actually involves deeper structures — retina and the optic nerve.

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