LONG-TERM RESULTS OF DIFFERENT UV-CROSSLINKING TECHNIQUES IN PATIENTS WITH PROGRESSIVE KERATOCONUS

Purpose. To compare a clinical effectiveness of different UV-crosslinking techniques in patients with progressive keratoconus.Material and methods. Randomized prospective clinical trial included 130 eyes of 117 keratoconic patients. There were created 2 equal groups of 65 eyes. In the group I patients underwent a classical UV-crosslinking technique with a complete central corneal deepithelialization, in the group II a UV-crosslinking with dosed corneal epithelium scarification was performed using a new device. The postoperative follow-up period was 24 months. Preoperatively in the group I the uncorrected visual acuity (UCVA) was 0.21±0.11, the best corrected visual acuity (BCVA) was 0.49±0.14, the central corneal pachymetry (CCP) – 469.1±23/4μm, the mean keratometry (Kave) – 46.1±1.7D, in the group II: UCVA was 0.22±0.09, BCVA – 0.48±0.12, CCP – 475.2±28.5μm, Кave – 46.7±1.4D.Results. The mean postoperative pain score was 6.9±1.3, relief on the 3-rd ±1.2 day post-op. in the group I, and 2.8±1.1 relief on the 1-st±0.4 day post-op. in the group II. All patients had a 0.1 to 0.12 visual acuity loss 7 days after the surgery that was due to a mild corneal opacification. At 3 months after operation in both groups the UCVA and the BCVA were back to their preoperative values. In the group I the UCVA increased by 0.07±0.03 (р<0.05) 2 years after the treatment, the BCVA increased by 0.11±0.04 (р<0.05). At that time in the group II the similar values were obtained: 0.08±0.02 (р<0.05), 0.1±0.04 (р<0.05) respectively. The Kave index in both groups gradually decreased during first 12 months after operation and then stabilized. At the end of the follow up it was lower by 2.6±0.5D (р<0.05) in the group I and by 2.4±0.3D (р<0.05) in the group II. According to the anterior OCT, the depth of demarcation line was 327±11μm in the group I and 318±13μm in the group II. The demarcation line was absent in all cases 12 months after surgery. In the early postoperative period 3 months after operation the CCP gradually decreased. It reduced by 3.77±0.83% (р<0.05) in the group I and by 3.17±0.88% (р<0.05) in the group II. After that the CCP slowly increased during the entire follow-up, but 24 months later it was still lower by 2.36±0.57% (р<0.05) in the group I and by 1.68%±0.75 (р<0.05) in the group II. Confocal microscopy 1 month after surgery revealed typical changes of corneal structure at the depth up to 310±9μm (290 to 335) in the group I and 300±8μm (280 to 330) in the group II. A full reinnervation and the repopulation of the cornea with keratocytes was seen 6 months after operation. The only complication (delayed corneal epithelization) was in the group with classical UV-crosslinking technique.Conclusions. The trial revealed similar clinical outcomes after classical UV-crosslinking technique and UV-crosslinking with dosed corneal epithelium scarification, however in the latter case during the postoperative period the severity and duration of pain were significantly reduced

EXPERIMENTAL RATIONALES OF THE EFFICACY OF DIFFERENT METHODS OF RIBOFLAVIN DELIVERY INTO THE CORNEAL STROMA AS THE INITIAL STEP OF CORNEAL UV CROSS-LINKING

Purpose. To study experimentally the penetration of a 0.1% riboflavin solution in the balanced salt solution (BSS) into the corneal stroma during the simulation of various UV cross-linking techniques and to assess an alteration of anterior corneal surface using a new device for dosed corneal epithelium scarification.Material and methods. We used the infra-red Fourierspectroscopy with the registration of reflectance spectra to assess the Riboflavin penetration into the corneal stroma. The study was performed in 9 human donor eyes (3 groups of 3 eyes in each) which were not acceptable for transplantation. A classic UV cross-linking technique with the complete removal of the epithelium was simulated in the first group, a transepithelial technique – in the second group, a technique of a dosed corneal epithelium disruption using a new model of scarifier device – in the third group. Donor eyes were fixed in a holder, the 0.1% riboflavin solution was instilled during 30 minutes in a rate of 1 drop per minute. In the second group the 0.1% riboflavin solution and the 0.5% proximetacaine solution (containing benzalkonium chloride) were instilled simultaneously to break the tight junctions between the epithelial cells. The alteration of anterior corneal surface was assessed in 3 cadaver eyes using the light microscopy after application of a new scarifier.Results. The analysis of infra-red spectra, registered from the endothelial side of the corneas in the first and the second groups showed a significant increase in intensity of the band at 1542 cm-1, which is typical for riboflavin. This fact demonstrates its full penetration to the corneal stroma and it complete impregnation. The increase of this index in the 1st and the 2nd groups was 7.3±0.5% and 7.8±0.6%, respectively (p>0.05). In the third group a relative intensity of the spectra did not differ significantly from those of control measurements (before instillation of riboflavin solution). The morphologic study of the corneas after use of a new scarifier showed the alteration of all epithelial layers up to the Bowman’s membrane without damaging of its integrity.Conclusions. We have proved a full impregnation of the corneal stroma with the 0.1% riboflavin solution using the method of dosed corneal epithelium scarification, comparable to that after a full corneal deepithelialization. The efficacy and safety of the new scarifier device were also substantiated

TREATMENT TACTICS AND OUTCOMES OF COMPLICATIONS IN IMPLANTATION OF CORNEAL SEGMENTS FOR KERATECTASIA OF VARIOUS GENESIS

Purpose. To evaluate the nature and frequency of intraand postoperative complications in intracorneal ring segments (ICRS) implantation for keratectasia of various etiology and to develop methods for their prevention and treatment.Material and methods. The investigation enrolled 189 patients (274 eyes) with keratoconus of the stage II (142 eyes) and stage III (102 eyes), PMD (12 eyes) and secondary keratectasia after laser refractive surgery (18 eyes). In 113 cases the surgery was performed with classical manual technique, in 161 cases we used an improved technique with vacuum fixation of the eyeball.Results. There were revealed 16 cases of complications (5.8%) including: 4 intra-operative corneal micro-perforations, 1 excessively deep segment implantation (directly at the Descemet’s membrane); in postoperative period – 2 cases of adenoviral keratitis (14 and 19 days post-op.) and 9 segment extrusions (3-8 months post-op.). In one case of too deep implantation the DALK was performed, in cases of microperforations we implanted the segment through the incision located in the meridian opposite to perforation. In 2 keratitis cases the ICRS were removed and the pharmacological therapy was performed. Segments were again implanted 6 months later. In case of extrusions, the ICRS were removed and re-implanted 3 to 6 months later. The refractive outcomes in patients having complications were comparable with the control group.Conclusion. The moderate number of complications (5.8%), the majority of which were stopped due to subsequent conservative and/or surgical interventions, testifies to a relative safety of intrastromal keratoplasty. Vacuum fixation of the eyeball secures a lesser complication rate (1/4 from initial). In consequence the possibility of secondary ICRS implantation was proved that provides high refractive results