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Purpose: To assess the activity of xanthine oxidase (XO) enzyme in keratoconic corneal epithelium and to evaluate its relationship with the keratoconus (KC) severity. Methods: This prospective and randomized study included 66 eyes of 54 KC patients who received corneal collagen cross-linking treatment and 43 eyes of 32 patients who underwent photorefractive keratectomy due to their refractive error. During surgical procedures, the corneal epithelium was mechanically scraped and gathered to analyze the XO enzyme activity spectrophotometrically. The KC group was subdivided into three groups (stages 1, 2, and 3) according to the Amsler–Krumeich classification. The results were compared between the KC and the control group and in between KC subgroups. Results: No significant differences in age and gender were found between the KC and control groups (p = 0.064 and p = 0.296, respectively). The mean XO activity levels of the KC and control groups were 173.57 ± 87.61 and 223.70 ± 99.52 mIU/mg, respectively (p < 0.001). In KC group, 33 eyes were at stage 1, 19 were at stage 2, and 14 were at stage 3. No significant difference was observed between KC subgroups regarding XO activity levels (p = 0.681). Conclusion: In this study, our findings revealed that ultraviolet-related pro-oxidant XO enzyme may have a role in the etiopathogenesis of KC. Further studies are needed to support our result. Clinical Trials Registration: When we started this study in 2018, we did not have a "Clinical Trials Registration." However, we have ethics committee approval (date: 21. 02. 2018/No: 22) [ABSTRACT FROM AUTHOR]

Purpose: To analyze the relationship between the seasonal allergic conjunctivitis (SAC), eotaxin-2, matrix metalloproteinase-9 (MMP-9), and the topographical findings in the keratoconus patients. Methods: Thirty-four eyes of patients without SAC (Group 1), 34 eyes of patients with SAC (Group 2), and 20 eyes of control subjects (control group) were enrolled. Tear samples of the subjects were collected by Schirmer method. Corneal topography parameters, tear MMP-9, and tear eotaxin-2 levels were analyzed. Results: The mean tear MMP-9 levels in Groups 1 and 2 were significantly higher than in the control group (p = 0.004). MMP-9 level exhibited a positive correlation with the keratoconus stage and a negative correlation with the thinnest corneal thickness (r = 0.294, p = 0.018, and r = − 0.302, p = 0.006, respectively). The tear eotaxin-2 level was higher in Group 2 than in Group 1 and control group which is not statistically significant (p = 0.17). Conclusion: The tear eotaxin-2 did not exhibit any difference in the presence of keratoconus. The tear MMP-9 level was higher in the keratoconic eyes, and it showed a correlation with the stage of the disease and the corneal thickness. [ABSTRACT FROM AUTHOR]

Purpose: To report on a keratoconus (KC) patient with Axenfeld-Rieger syndrome (ARS) who developed sterile keratitis after accelerated corneal collagen cross-linking (CXL). Methods: An 18-year-old patient with ARS and KC who had previously undergone intrastromal ring segment implantation underwent accelerated CXL (9 mW/cm2 UVA intensity for 10 min). Results: After uneventful surgery, the patient presented with severe photophobia, redness of the eye, and decreased vision 72 h following the procedure. Slit-lamp examination showed anterior multiple superficial stromal infiltrates in the central cornea with an overlying epithelium defect. Due to the lack of pain and absence of any pathogen from corneal samples, a diagnosis of sterile keratitis was considered. A combination of topical antibiotic and corticosteroid regimen was administered. Three months after CXL slit-lamp examination showed a mild stromal scar overlying the central cornea, which did not decrease visual acuity. Conclusions: The mechanism by which the sterile keratitis occurs following CXL remains unclear. For our case, the reason of post-CXL sterile keratitis could be considered as an immune response due to the staphylococcal antigens. Furthermore, the possible developmental disturbance of corneal stroma in ARS might have contributed to the development of post-CXL sterile keratitis. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study was to evaluate the corneal biomechanical parameters in patients with ankylosing spondylitis (AS) and to compare them with the healthy subjects. Methods: Sixty patients with AS (study group) and 60 healthy subjects (control group) were enrolled in this prospective study. The study group was further classified as active (n:30) and inactive (n:30). After detailed ophthalmological examination including intraocular pressure (IOP) measurement with Goldmann applanation tonometer (IOPGAT), corneal hysteresis (CH), corneal resistance factor (CRF), corneal-compensated IOP (IOPcc), and Goldmann-correlated IOP (IOPg) were measured with the Reichert Ocular Response Analyzer (ORA). Central corneal thickness (CCT) was measured with the Spectral-Domain Optical Coherence Tomography (SD-OCT). Results: The study group's mean CH, CCT, IOPg, and IOPGAT values were lower than the control group ( p < 0.05 for all variables). The mean CH, CRF, CCT, IOPg, and IOPGAT values were higher in active patients when compared to the inactive ones ( p < 0.001, p < 0.001, p = 0.013, p = 0.021, and p = 0.002, respectively). Conclusions: AS patients have lower CCT, CH, IOPg, and IOPGAT when compared with healthy subjects. In the active stage of AS, patients present with higher levels of corneal biomechanical parameters with thicker corneas. IOPcc is a more accurate measurement than IOPGAT or IOPg in AS patients. [ABSTRACT FROM AUTHOR]

The purpose of the study was to evaluate the outcomes and possible complications of CXL performed with customized epithelial debridement technique to keratoconic corneas with the thinnest pachymetry values less than 400 µm. Nineteen eyes of 19 patients were included. The uncorrected (UCVA) and best corrected visual acuity (BCVA), flattest and steepest keratometric (K) readings, central corneal thickness at the thinnest point (t-CCT), endothelial cell density (ECD) were assessed before and 12 months after CXL. The mean UCVA was increased ( p = 0.001), while the mean BCVA did not show any difference ( p > 0.05). The mean flattest and steepest K readings were decreased ( p = 0.001). No change was observed in the mean t-CCT ( p > 0.05). The mean ECD was decreased ( p = 0.001). The mean pre-CXL and post-CXL percentages of polymegathism and pleomorphism did not show any significant difference ( p > 0.05). CXL performed with customized epithelial debridement technique is successful in halting the progression of keratoconus in corneas thinner than 400 µm after 12 months of treatment. However, significant endothelial cell loss can occur after this procedure. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate tear osmolarity and ocular comfort with two different types of hydrogel daily disposable lenses. The right eyes of 15 first-time contact lens users were included in this prospective study. All eyes wore hilafilcon B silicone hydrogel contact lenses for 8 h (group 1). After 1 week without contact lenses, all eyes wore narafilcon A silicone hydrogel contact lenses for 8 h (group 2). Tear osmolarity measurement was performed before and after 4 and 8 h of each contact lens wear. Ocular comfort was assessed after 4 and 8 h of each contact lens wear. In group 1, the mean baseline, 4- and 8-h tear osmolarity values were 293 ± 10.57, 303.00 ± 10.5 mOsm/L ( p = 0.023), and 295.0 ± 1.4 mOsm/L ( p > 0.05), respectively. In group 2, the mean baseline, 4- and 8-h tear osmolarity values were 294 ± 13.65, 300.9 ± 11.3 mOsm/L ( p = 0.007), and 298.80 ± 7.2 mOsm/L ( p > 0.05), respectively. In group 1, the mean comfort score was 7.20 ± 0.45 and 8.60 ± 0.45 at 4 and 8 h, respectively ( p = 0.038). In group 2, the mean comfort score significantly decreased from 9.80 ± 0.45 to 7.80 ± 0.84 at 4 h ( p = 0.039). Both hydrogel and silicone hydrogel daily disposable contact lenses elevated tear osmolarity during 8 h of contact lens wear. The increase in tear osmolarity with both contact lenses was below the cut-off value for dry eye and was not associated with ocular comfort. [ABSTRACT FROM AUTHOR]