Biomedical subjects

K Bilgihan

Publications and source records attributed to K Bilgihan.

27 records · Page 2Linked to original sources

PubMed1996

Excimer laser corneal surgery and free oxygen radicals.

Corneal photoablation with 193 nm argon fluoride excimer laser is a new technique for the treatment of refractive errors and for removing corneal opacities and irregularities. Ultraviolet radiation and thermal injury induce free radical formation in the tissues. The aim of this study was to confirm the production of free radicals by excimer laser photoablation in rabbits. The thermal changes of the posterior corneal surface were recorded during excimer laser photoablation. The lipid peroxide (LPO) levels and superoxide dismutase (SOD) activities of aqueous humour were measured after excimer laser keratectomy. The aqueous LPO levels were not changed after excimer laser ablation, but both the thermal increase in the cornea during the photoablation and the decreased aqueous SOD activities suggest that free radicals are formed in the cornea during excimer laser keratectomy, and that they may be responsible for some of the complications of excimer laser corneal surgery.

Animals↗

PubMed1994

The effect of EGb 761 on retinal lipid peroxidation and glutathione peroxidase level in experimental lens induced uveitis.

An acute lens-induced necrotizing intraocular inflammation was produced in pigmented guinea pigs. Treatment of these animals by 100 mg/kg/day EGb 761 a free oxygen radical scavenger for 10 days, reduced retinal lipid peroxidation (p > 0.05) and increased the retinal glutathione peroxidase level (p > 0.05). Although not significantly, these findings suggest that EGb 761 could be combined with other antiinflammatory drugs and may be beneficial in the treatment of uveitis.

Administration, Oral↗

PubMed1993

Ketoconazole induced papilledema.

Ketoconazole was administered in a case of hirsutismus over a period of 4 months with high doses of 800 mg/day, and bilateral papilledema developed. After cessation of the drug the condition disappeared. As far as we know this is the first reported papilledema complication due to Ketoconazole.

Adult↗

PubMedDate not supplied

Scanning laser polarimetry in corneal topographic changes after photorefractive keratectomy.

PURPOSE: To examine whether, or not, corneal topographic changes after excimer laser photorefractive keratectomy (PRK) for myopia and myopic astigmatism have any influence on measurements of the retinal nerve fiber layer (NFL) with scanning laser polarimetry. METHODS: Retinal NFL thicknesses were determined by scanning laser polarimetry in 17 eyes of 13 patients with myopia and myopic astigmatism before and after PRK. Total ablation depth ranged from 26 to 71 microm. We used the relative ratios for superior and inferior NFL thicknesses which were calculated by dividing the NFL values of respective regions by the nasal value. RESULTS: The mean superior NFL ratio measured was 3.02 +/- 0.92 preoperatively, and 3.00 +/- 0.76 postoperatively. The mean inferior NFL ratio was 2.95 +/- 0.75 preoperatively, and 2.99 +/- 0.66 postoperatively. There was no statistically significant difference between preoperative and postoperative NFL measurements (Wilcoxon signed rank test, p > 0.05). CONCLUSIONS: Corneal topographic changes after PRK have no significant influence on NFL measurements by scanning laser polarimetry. Our results suggest that scanning laser polarimetry can be used as a reliable method for retinal NFL thickness measurements even after excimer laser PRK.

Adult↗

PubMedDate not supplied

Effects of topical vitamin E on keratocyte apoptosis after traditional photorefractive keratectomy.

PURPOSE: To evaluate the keratocyte apoptosis and effects of topical vitamin E on keratocyte apoptosis after photorefractive surgery. METHODS: Rabbits were divided into 7 groups, and all groups were compared with controls after epithelial scraping, epithelial scrape and photorefractive keratectomy (PRK) (traditional PRK), transepithelial PRK, production of a corneal flap with microkeratome and laser-assisted in situ keratomileusis (LASIK). The effects of topical Vitamin E treatment were investigated in the traditional PRK group. The terminal deoxyribonucleotidyl transferase-mediated dUTP-digoxigenin nick-end labelling assay (to detect DNA fragmentation in situ) and light microscopy have been used to detect apoptosis in rabbit cornea. RESULTS: Transepithelial PRK induced minimal keratocyte apoptosis, less than in all other refractive surgical procedures. The greatest amount of keratocyte apoptosis was observed after traditional PRK (p = 0.001), therefore we tested the effects of topical vitamin E in this group. The number of apoptotic keratocytes significantly reduced after vitamin E therapy (p < 0.005). CONCLUSION: Keratocytes undergo apoptosis after refractive surgery in response to mechanical epithelial removal, preparing of corneal flap and excimer laser stromal photoablation. The topical application of vitamin E immediately after surgery can prevent keratocyte apoptosis, and this result suggests that free radicals may be partly responsible for keratocyte apoptosis after excimer laser keratectomy.

Administration, Topical↗

PubMedDate not supplied

Nitric oxide levels of aqueous humor after photorefractive keratectomy.

PURPOSE: To measure the nitric oxide (NO) levels of aqueous humor in rabbits after photorefractive keratectomy (PRK) and to evaluate the alterations of NO levels according to the PRK surgery steps, ablation depth, and time. METHODS: Fifty eyes of 25 New Zealand white rabbits were included in the study. One eye was later randomly excluded from the study in order to equalize the number of eyes in groups. Eyes were divided into seven groups, each comprising seven eyes: unwounded control (Group 1), epithelial scrape (Group 2; aqueous humor samples taken at the 4th hour), superficial PRK (Group 3; samples taken at the 4th hour), deep PRK (Group 4; samples taken at the 4th hour), epithelial scrape (Group 5; samples taken at the 24th hour), superficial PRK (Group 6; samples taken at the 24th hour), and deep PRK (Group 7; samples taken at the 24th hour). The corneal epithelium was mechanically removed in surgical groups. The authors performed superficial corneal ablation (59 microm) in Groups 3 and 6 and deep corneal ablation (99 microm) in Groups 4 and 7. Aqueous humor samples were taken at the 4th hour (Groups 2-4) or 24th hour (Groups 5-7) after corneal surgeries. NO measurements were performed indirectly by using the Griess reaction with a spectrophotometer. RESULTS: Aqueous humor NO levels 4 hours after corneal surgery were statistically significantly lower than the control group (p<0.05). However, there was no difference among the surgical groups at the 4th hour (p>0.05). At the 24th hour, the deep PRK group had significantly lower NO levels than both the control group and Groups 5 and 6 (p<0.05). NO levels were normalized at the 24th hour in epithelial scrape and superficial PRK groups (p>0.05) but remained stable at lower levels in deep PRK groups (p<0.05). CONCLUSIONS: Corneal surgery caused low NO levels in aqueous humor 4 hours after surgery. However, 24 hours after surgery, NO levels normalized following epithelial scrape and superficial PRK and were stable at lower levels in the deep PRK group. Complications of deep PRK application are possibly induced by low NO existence in the aqueous humor.

Analysis of Variance↗

PubMedDate not supplied

Photorefractive keratectomy for visual rehabilitation of anisometropia induced by retinal detachment surgery.

PURPOSE: To evaluate the efficacy of unilateral photorefractive keratectomy to correct anisometropia induced by retinal detachment surgery. METHODS: Photorefractive keratectomy was performed in 10 eyes of 10 patients with anisometropia induced by previous retinal detachment surgery. The Aesculap Meditec MEL 60 excimer laser was used. RESULTS: Preoperative mean spherical equivalent refraction was -5.20 D. Mean postoperative spherical equivalent refraction was -0.25 D after a mean follow-up of 12.9 months. Mean preoperative spherical equivalent refraction difference between two eyes of 4.87 D was decreased to a mean 0.60 D postoperatively (t-test, P < .0001). All patients were free of anisometropic symptoms after laser surgery. CONCLUSION: Unilateral photorefractive keratectomy seems to be an effective method to correct anisometropia induced by conventional retinal detachment surgery, especially for patients with spectacle and contact lens intolerance.

Adolescent↗

PubMedDate not supplied

Results of photorefractive keratectomy in keratoconus suspects at 4 years.

PURPOSE: We studied the long-term results of photorefractive keratectomy (PRK) in keratoconus suspects detected by videokeratography (TMS). METHODS: Bilateral inferior corneal steepening was detected in 6 candidates for PRK presenting with moderate myopia or astigmatism. Mean follow-up was 44.5 +/- 4.4 months (range, 38 to 54 mo). Mean spherical equivalent refraction was -5.18 +/- 1.60 D (mean sphere, -4.73 D; mean cyclinder, -0.92 D) which was stable for at least the preceding year. The quantitative measurement of inferior corneal steepening (I-S value) was greater than +1.60 (mean, 1.83 +/- 0.11) in all eyes. An Aesculap Meditec Mel 60 excimer laser was used for the PRK procedures and mean follow-up was 44.5 months. Postoperative pachymetric measurements were also performed in 6 eyes. RESULTS: Postoperative uncorrected visual acuity was 20/20 in 8 eyes (66.6%) and 20/32 or better in all eyes with a mean postoperative spherical equivalent refraction of -0.70 +/- 0.74 D (mean sphere, -0.63 D; mean cyclinder, -0.39 D). Five eyes (41.6%) were within +/- 0.50 D spherical equivalent refraction. Inferior steepening was associated with thinning of the inferior cornea which was statistically significantly thinner than the superior thickness (Student's t-test, P < .05). There were no wound healing problems or any sign that the excimer laser adversely affected the cornea during follow-up. CONCLUSIONS: Photorefractive keratectomy seems to be a safe procedure for reducing or eliminating myopia or astigmatism in keratoconus suspect eyes-most probably forme fruste keratoconus-with a stable refraction, but this may be different in eyes with early keratoconus, known to be a progressive disease.

Adult↗

PubMedDate not supplied

The effects of artificial tear solutions on wound healing in full thickness corneal incisions.

Carbopols (carbomer, polyacrylic acid) are appropriate for ophthalmic use as an artificial tear in the form of viscous aqueous solutions. Carbopol 940 preparations were developed as long-lasting artificial tears for the relief of dry eye syndrome and traumatic injury. We identified the 15 days local treatment effects of two artificial tear solutions by wound strength and histologic examination of the incision wounds of rabbit corneas by comparing these results with the controls. Three layers of control corneas were regular. The untreated but wounded corneas epithelium and stroma were completely irregular. Both treated eyes had thinner epithelization in the incision site compared to control unwounded eye. Wounds treated with A preparation (viscotiers) had vocuoles and numerous inflammatory cells and remarkable oedematous regions but B preparation (Thilo-Tears) treated wounds had inflammatory cells and oedematous regions less than the other group. The wound strengths of gel treated wounds were bigger than those of controls. A considerable result in wound strength and better wound healing was also obtained in B preparation treated group because of the arrangement of the pH and tonicity at the Thilo-tears gel preparation.

Acrylic Resins↗