Singlet oxygen formation during accelerated and hyperaccelerated corneal cross-linking: in vitro study

BACKGROUND: To evaluate the singlet oxygen (1 O2) production of oxygen assisted %0.1 riboflavin and ultraviolet-A (UVA) crosslinking therapy (with and without oxygen assistance), in combination with standard, accelerated and hyper-accelerated procedures via an important quantitive marker of 1 O2 which is the photo-oxidation of 1,3 diphenylisobenzofuran (DPBF). METHODS: %0.1 riboflavin-containing wells were irradiated with UVA light (365-nm wavelength) with or without 2-4-6-8 L/min oxygen flow assistance. Measurements of decrease in absorbance of DPBF were made in 30 mW (hyper-accelerated), 9 mW (accelerated), and 3 mW UV-A (standard) applications, and with additional 2-4-6-8 L/min oxygen flow in 30 mW and 2 L/min oxygen flow in 9 mW. A total of 8 different UV-A irradiance with and without oxygen supplementation groups were formed. RESULTS: 2 L/min oxygen assisted accelerated UV-A irradiance group has shown a greater decrease in DPBF absorbance compared to Dresden protocol. (p = 0.014) Also, Dresden protocol has shown a greater decrease in DPBF compared to all groups except accelerated crosslinking with 2 L/min oxygen. (p < 0.001) Oxygen assisted hyper-accelerated crosslinking groups were showed greater reduction in DPBF absorbance compared to standard crosslinking without oxygen groups. (p < 0.001). CONCLUSION: Oxygen supplementation may increase the singlet oxygen generation to the similar levels of Dresden Protocol’s in accelerated group. Also, more singlet oxygen generation with oxygen supplementation compared to standard UV-A application might be considered to be promising in terms of shortening the crosslinking therap

Effect of corneal cross-linking on contact lens tolerance in keratoconus

Background: The aim was to investigate changes in corneal sensation and rigid gas-permeable (RGP) contact lens tolerance after corneal cross-linking (CXL) on patients with keratoconus

Effect of corneal cross-linking on contact lens tolerance in keratoconus

Background: The aim was to investigate changes in corneal sensation and rigid gas-permeable (RGP) contact lens tolerance after corneal cross-linking (CXL) on patients with keratoconus. Methods: Thirty eyes of 30 patients, who were RGP lens intolerant, were treated with CXL. The main outcome measures were corneal sensation evaluation by Cochet-Bonnet esthesiometry, sub-basal nerve fibre assessment by corneal in vivo confocal microscopy and RGP contact lens tolerance evaluation with the Likert scale and wearing time. All eyes were evaluated preoperatively and post-operatively at one, three and six months after CXL procedure. Results: The mean age was 25.3 +/- 6.2 years. Preoperatively, the maximum keratometry (Kmax) in study eyes was 56.89 +/- 4.60 D. Six months after CXL, it reduced to 56.03 +/- 4.85 D (p = 0.01). Preoperative mean corneal sensation was 0.44 +/- 0.05 g/mm(2), (range: 0.40 to 0.55); it was significantly decreased at the first month and increased to preoperative values after six months. The sub-basal nerve plexus could not be visualised in 90 per cent of the patients by confocal microscopy at one month post-operatively. Gradual restoration of corneal innervation with almost similar preoperative levels at postoperative month six was noted. There were significant differences in Likert scores between preoperative and third and sixth months after CXL. Likert scale scores correlated significantly with corneal sensitivity. Conclusion: It can be concluded that increased RGP contact lens tolerance after CXL may be associated with the potential role of decreased corneal sensitivity and corneal flattening after CXL

A Clinical and Confocal Microscopic Comparison of Transepithelial PRK and LASEK for Myopia

Purpose. To compare the clinical and confocal microscopic results of transepithelial PRK versus LASEK for correction of myopia. Materials and Methods. Twelve patients with myopia received transepithelial PRK in one eye and LASEK in the other. In transepithelial PRK-treated eyes, the corneal epithelium was removed with 40 microns of excimer laser ablation and in LASEK-treated eyes with 25-second application of 18% ethanol. Time to epithelial healing, ocular discomfort, uncorrected and best corrected visual acuities, manifest refraction, haze, greyscale value, and keratocyte apoptosis in confocal microscopy were recorded. Results. The mean time to epithelial healing was significantly longer after LASEK (4.00 ± 0.43 versus 3.17 ± 0.6 days). On day 1, ocular discomfort was significantly higher after transepithelial PRK. The grade of haze, keratocyte apoptosis, and greyscale value in confocal microscopy were significantly higher in transepithelial PRK-treated eyes at 1 month. All transepithelial PRK- and LASEK-treated eyes achieved 20/25 or better UCVA and were within ±1.00 D of emmetropia at final visits. Conclusions. Both transepithelial PRK and LASEK offer effective correction of myopia at 1 year. However, LASEK appeared to induce less discomfort and less intense wound healing in the early postoperative period

Tear secretion and tear stability after laser subepithelial keratomileusis (LASEK)

Amaç: LASEK’in gözyaşı fonksiyonlarında neden olduğu değişikliklerin gözyaşı sekresyonu ve stabilitesi ölçümleri ile değerlendirilmesi. Gereç ve Yöntem: Düşük ve orta dereceli miyopinin düzeltilmesi amacıyla LASEK uygulanan 20 hastanın 36 gözünde Schirmer 1 testi, bazal gözyaşı sekresyonu ve gözyaşı kırılma zamanı ölçümleri preoperarif, postoperatif 1. hafta, 1. ay, 3. ay ve 6. ayda gerçekleştirilerek sonuçları değerlendirildi. Bulgular: Schirmer test değerinde postoperatif tüm ölçümlerde preoperatif 25 9.3 mm olan ortalama değere göre anlamlı bir değişiklik gözlenmedi (p0.05). Bazal gözyaşı sekresyonu ve gözyaşı kırılma zamanında postoperatif 1. haftada (p0.01) ve 1. ayda (p0.05) istatistiksel olarak anlamlı düzeyde düşüş izlenirken 3. ayda preoperatif değerlere ulaşarak 6. ayda stabil seyrettiği saptandı. Sonuç: LASEK sonrası gözyaşı fonksiyonlarında geçici ve kısa süreli bozulma meydana gelmektedir. LASIK ve PRK ile daha önce yapılan çalışmalar ile karşılaştırıldığında gözyaşı fonksiyonlarının belirgin olarak hızlı düzelmesi LASEK’i refraktif cerrahide avantajlı konuma getirebilirAim: To evaluate the effects of LASEK on tear functions with the measurements of tear secretion and tear stability Material and Methods: Schirmer 1, basal tear secretion and tear break-up time tests were performed preoperatively, postoperative 1st week, 1st month, 3rd month and 6th month in 36 eyes of 20 patients who had LASEK surgery for the correction of low to moderate myopia and the results were evaluated. Results: No significiant change was observed in Schirmer test value postoperatively from the preoperative mean value of 25 ± 9.3 mm (p>0.05). There were statistically significant decreases in basal tear secretion and tear break-up time at postoperative 1st week (p<0.01) and 1st month (p<0.05) which reached preoperative values at 3rd month and stayed stabilized at 6th month. Conclusion: LASEK induced a reversible and short-term distruption of tear functions postoperatively. An obviously faster recovery of tear functions compared to previous studies done with LASIK and PRK, could be an advantage for LASEK in refractive surgery

Excimer laser phototherapeutic keratectomy in conjunction with mitomycin C in corneal macular and granular dystrophies.

To evaluate the visual outcomes, recurrence patterns, safety, and efficacy of excimer laser phototherapeutic keratectomy (PTK) in conjunction with mitomycin C (MMC) for corneal macular and granular diystrophies