[Results of corneal crosslinking for pellucid marginal corneal degeneration]. / Rezul'taty lecheniia pelliutsidnoi marginal'noi degeneratsii rogovitsy metodom rogovichnogo krosslinkinga.

AIM: to evaluate the clinical effectiveness of crosslinking in patients with progressive pellucid marginal corneal degeneration (PMCD). MATERIAL AND METHODS: A total of 9 patients (16 eyes) with progressive PMCD were treated by standard crosslinking. The cornea was saturated with Dextralink solution and UV-A irradiated at 3 mW/cm2 for 30 minutes. The follow-up period was 12 months. RESULTS: One month after treatment, there was a slight decrease in uncorrected and best corrected visual acuity (UCVA and BCVA) - from 0.08±0.03 and 0.4±0.15 preoperatively down to 0.06±0.02 and 0.3±0.07, respectively, caused by pseudohaze of the cornea. Keratometric parameters (the average refractive power of the cornea, corneal astigmatism, and corneal thickness) did not change significantly. The demarcation line was identified in 56% of cases. By the 3-month follow-up, UCVA and BCVA improved up to 0.1±0.07 and 0.52±0.1, respectively. The refractive power of the cornea decreased by 2.0 diopters and corneal astigmatism - by 0.7 diopters reaching 46.8±2.7 and 5.1±1.3 diopters, respectively (p≤0.04). Central corneal thickness decreased by an average of 29 microns. The demarcation line remained visible in 25% of cases. At 6 months, BCVA averaged 0.58±0.13, at that, 56% of eyes gained 1 line and 31% - 2 lines. The refractive power of the cornea decreased down to 45.7±1.6 diopters, corneal astigmatism - down to 4.8±1.5 diopters. The demarcation line was not detected. At 1 year, there were no significant changes in the average values of optometric indices as compared to the 6-month period. Сonclusion. Pellucid marginal corneal degeneration should be regarded as a kind of primary ectasia, often bilateral and notable for its characteristic clinical picture and late onset. In progressive disease, photochemical crosslinking of the cornea contributes to the improvement of optometric parameters and stabilization of the process.

[Dynamics of riboflavin level in aqueous humour of anterior chamber of experimental animals under standard stroma saturation by ultraviolet corneal cross-linking solutions]. / Dinamika urovnya riboflavina vo vlage perednei kamery glaza eksperimental'nykh zhivotnykh pri standartnom nasyshchenii stromy rastvorami dlya ul'trafioletovogo krosslinkinga rogovitsy.

AIM: To evaluate the dynamics of riboflavin changes in the aqueous humour of the anterior chamber (AHAC) of rabbits' eyes during standard ultraviolet (UV) cross-linking with account to the area of corneal debridement. MATERIAL AND METHODS: Forty two rabbits were studied sequentially. The following solutions of riboflavin were used for cornea saturation: IR - 0.1% isosmotic riboflavin, D - Dextralink (0.1% riboflavin with 20% dextran), R - 0.1% riboflavin with 1.0% hydroxypropylmethylcellulose (HPMC). Each solution was evaluated in 3 groups that differed in the diameter of corneal debridement: group 1 - Epi-Off 3 mm (IR-3, D-3, P-3), group 2 - Epi-Off 6 mm (IR-6, D-6, R-6), and group 3 - Epi-Off 9 mm (IR-9, D-9, R-9). Aqueous humour sampling (252 samples in total) was performed in 10-minute intervals within a 60 minute period. Riboflavin levels were measured by enzyme-linked immunoassay (ID-Vit microbiological test system; Immundiagnostik, Germany). RESULTS: Stable growth rates of riboflavin level in the AHAC (with maximum values reached at 30-40 min) were observed for solutions D and R, regardless of the variant of corneal debridement. Moreover, throughout the whole follow-up period and regardless of the area of corneal debridement, the solution D provided a relatively lower concentration of riboflavin in the AHAC as compared to the two other solutions. At 30 minutes, when the cornea was considered ready for UV irradiation, the riboflavin level in the AHAC ranged from 385±26.1 µg/l (D-9) to 665±28 µg/l (R-9). In groups IR-9, IR-6, P-6, IR-3, and P-3 riboflavin levels were found to be in the same range starting at 20 minutes. However, even a sufficient concentration of riboflavin in the cornea or AHAC cannot guarantee safe and effective UV cross-linking, since the removed epithelium limits the area of the stroma that can be saturated with riboflavin, while the area of UV exposure is 8-10 mm. CONCLUSION: Safe and efficient standard UV cross-linking may be performed only under sufficient saturation of the stroma with riboflavin, which in turn depends greatly on the area of corneal debridement (should be at least 8-9 mm). A solution of 0.1% riboflavin and 1.0% HPMC enables quick and pronounced saturation of the stroma and, thus, can be used in the UV cross-linking procedure, including cases of insufficient corneal thickness.

[Ultraviolet Corneal Crosslinking].

This review presents basic information on UV corneal crosslinking. The method is widely used in ophthalmology to treat various types of ectasia, which are characterized by progressive degenerative changes in the cornea, associated with its thinning , hazing and scarring, which leads to a significant reduction in visual acuity. Crosslinking is based on ultraviolet (UV) irradiation of the cornea wavelength 370 nm in the presence of riboflavin, leading to photochemical intracorneal interactions. As a result of crosslinking of collagen treatments, an increase of strength and mechanical properties of the cornea, stops the progression of the disease. The article displays the steps of the method development and the ways of its implementation are described especially occurring biomechanical, biochemical, morphological and ultrastructural changes, as well as the main areas of clinical application of riboflavin-UV-A-induced crosslinking of cornea.