Comprehensive assessment of structural changes in the cornea and tear film in keratoconus associated with dry eye syndrome, against the background of optical correction and tear replacement therapy

Relevance According to the literature, there is an association between keratoconus (KC) and signs of dry eye syndrome (DES) [1, 2]. Widely used in optical correction of keratoconus, rigid gas-permeable scleral contact lenses (RGPCL) have increasingly been used in the treatment of DES to protect the cornea and tear film [3–5]. Objective To evaluate changes in the condition of the cornea and tear film in keratoconus associated with DES, while wearing rigid gas-permeable scleral contact lenses in combination with tear replacement therapy and in its absence. Material and methods A total of 30 patients (60 eyes) with bilateral stabilized non-operated KC of various stages associated with DES were examined. The patients were divided into groups: Group 1 - 15 patients (30 eyes), who used 0.9% sodium chloride (saline) as a wetting solution filling the lens cup before installing it on the eye, Group 2 - 15 patients (30 eyes) used a preservative-free tear substitute based on 0.18% hyaluronic acid (HA) as a wetting solution. All patients underwent the following examinations: biomicroscopy of the anterior segment of the eye using a vital dye (sodium fluorescein 0.1%) and assessment of the degree of conjunctival and corneal epitheliopathy according to the Oxford system, determination of the breakup time of the precorneal tear film, as well as the state of total and main tear production. Morphological assessment of the state of all corneal layers was performed using the corneal confocal microscopy (CCM) method. Results When wearing SGCL, regardless of the type of solution filled into the lens cup before installing it on the eye, there is a significant improvement in the condition of the ocular surface and an increase in the indices of functional tests. However, greater positive dynamics were observed in the group using the drug with HA. This was confirmed by the CMR data in the form of a significant improvement in the epithelial layer of the cornea. Conclusion The tendency we noted towards a higher ability to reparate corneal tissues when using a drug with 0.18% HA in the sublens space is confirmed by the CMR data and indicates greater effectiveness of using a combination with a tear substitute. Key words: keratoconus; scleral rigid gas-permeable lenses; confocal microscopy of the cornea