Kamil Bilgihan

Photorefractive keratectomy for post-penetrating keratoplasty myopia and astigmatism

Purpose: To determine the safety, effectiveness, and predictability of photorefractive keratectomy (PRK) for the correction of myopia and astigmatism after penetrating keratoplasty. Setting: Gazi University, Medical School, Department of Ophthalmology, Ankara, Turkey. Methods: Photorefractive keratectomy was performed in 16 eyes of 16 patients with postkeratoplasty myopia and astigmatism who were unable to wear glasses due to anisometropia and were contact lens intolerant. They were examined for uncorrected visual acuity (UCVA), best spectacle‐corrected visual acuity (BSCVA), and corneal transplant integrity before and after surgery. Results: The mean follow‐up after PRK was 26.0 months ± 15.7 (SD) (range 12 to 63 months). The mean preoperative spherical equivalent refraction of −4.47 ± 1.39 diopters (D) was −3.39 ± 1.84 D (P > .05) at the last postoperative visit and the mean preoperative cylinder of −5.62 ± 2.88 D was −3.23 ± 1.70 D (P < .05); refractive regression correlated with the amount of ablation performed. The BSCVA decreased in 3 eyes (18.8%), and the UCVA decreased in 2 (12.5%). Six eyes (37.5%) had grade 2 to 3 haze, which resolved spontaneously in 4 eyes within a relatively long time but caused a decrease in BSCVA in 2 (12.5%). Two of the eyes (12.5%) had a rejection episode after PRK and were successfully treated with topical steroids. Conclusions: Photorefractive keratectomy to correct postkeratoplasty myopia and astigmatism appears to be less effective and less predictable than PRK for naturally occurring myopia and astigmatism. Corneal haze and refractive regression are more prevalent, and patient satisfaction is not good.

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 (Students 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.

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.

Keratocyte apoptosis and corneal antioxidant enzyme activities after refractive corneal surgery.

Purpose Refractive corneal surgery induces keratocyte apoptosis and generates reactive oxygen radicals (ROS) in the cornea. The purpose of the present study is to evaluate the correlation between keratocyte apoptosis and corneal antioxidant enzyme activities after different refractive surgical procedures in rabbits.Methods Rabbits were divided into six groups. All groups were compared with the control group (Group 1), after epithelial scraping (Group 2), epithelial scrape and photorefractive keratectomy (PRK) (traditional PRK: Group 3), transepithelial PRK (Group 4), creation of a corneal flap with microkeratome (Group 5) and laser-assisted in situ keratomileusis (LASIK, Group 6). Terminal deoxyribonucleotidyl transferase-mediated dUTP-digoxigenin nick-end labelling assay (to detect DNA fragmentation in situ) and light microscopy were used to detect apoptosis in rabbit eyes. Glutathione peroxidase (Gpx) and superoxide dismutase (SOD) activities of the corneal tissues were measured with spectrophotometric methods.Results Corneal Gpx and SOD activities decreased significantly in all groups when compared with the control group (P<0.05) and groups 2, 3 and 6 showed a significantly higher amount of keratocyte apoptosis (P<0.05). Not only a negative correlation was observed between corneal SOD activity and keratocyte apoptosis (cc: −0.3648) but Gpx activity also showed negative correlation with keratocyte apoptosis (cc: −0.3587).Conclusion The present study illustrates the negative correlation between keratocyte apoptosis and corneal antioxidant enzyme activities. This finding suggests that ROS may be partly responsible for keratocyte apoptosis after refractive surgery.

Topical vitamin E and hydrocortisone acetate treatment after photorefractive keratectomy.

Purpose To investigate the effects of topical vitamin E and hydrocortisone acetate treatments on corneal healing response after -10.0 D photorefractive keratectomy (PRK) in rabbits.Methods Thirty-three New Zealand white rabbits were divided into four groups and -10 D PRK was performed under in vivo conditions. Following PRK, group 1 (n = 9) received no topical treatment and served as control. Group 2 (n = 8) received 0.1% hydrocortisone acetate ointment twice a day, group 3 (n = 8) received 1% vitamin E ointment and group 4 (n = 8) received both 0.1% hydrocortisone acetate and 1% vitamin E twice a day for a month. At the end of the third month, corneal haze was graded and the corneal hydroxyproline levels were measured, as a crude indicator of new collagen synthesis. Finally corneal samples were examined by transmission electron microscopy.Results Non-homogeneously distributed strong haze was identified in group 1 which was greater than in the other groups; haze was least in groups 2 and 4. Corneal hydroxyproline levels were found to be significantly lower in groups 2, 3 and 4 compared with the control (Students t-test, p < 0.05). Histopathologically, the most aggressive wound healing response was detected in group 1. The corneal wound healing response of group 2 was less than that of group 1 and equal to or more than that of group 4.Conclusions Deep corneal photoablation induces an aggressive healing response, and topical hydrocortisone acetate reduces this corneal wound healing effectively. The inhibitory effect of topical vitamin E on corneal wound healing seems to be less than that of hydrocortisone acetate, but combined treatment with these two drugs may have an additive effect in controlling corneal wound healing after PRK.

Ascorbic acid levels in human tears after photorefractive keratectomy, transepithelial photorefractive keratectomy, and laser in situ keratomileusis

Purpose: To investigate the level of ascorbic acid in human tear fluid after photorefractive keratectomy (PRK), transepithelial PRK, and laser in situ keratomileusis (LASIK). Setting: Departments of Ophthalmology and Biochemistry, School of Medicine, Gazi University, Ankara, Turkey. Methods: Twenty patients (7 women and 13 men) were included in this study. Traditional PRK with epithelial scraping by a blunt spatula followed by surface ablation (7 eyes), transepithelial PRK (7 eyes), or LASIK (6 eyes) was performed. Tears were collected preoperatively and 1 and 5 days postoperatively. Ascorbic acid levels were measured using 2‐4 dinitrophenylhydrazine. Results: Ascorbic acid levels in the tear fluid were decreased significantly 1 day after PRK, transepithelial PRK, and LASIK (P < .05). On the fifth day, the ascorbic acid levels were significantly lower than preoperatively in all groups. Conclusion: After PRK, transepithelial PRK, and LASIK, the ascorbic acid levels of the tear fluid decreased significantly. Because ascorbic acid is the major scavenger of superoxide radicals in tears, topical ascorbic acid therapy may help eliminate the harmful effect of free radicals from excimer laser surgery.

Pregnancy-induced progression of keratoconus.

Purpose: To report eyes with keratoconus that progressed during pregnancy. Methods: Seven eyes of 4 patients with progression of keratoconus during pregnancy were included in this study. The mean age of patients and the mean follow-up duration were 29.3 years and 39 months, respectively. Progressive keratoconus was documented with changes in refraction, corneal topography, and rigid gas-permeable lens fitting pattern. Patients with accompanying systemic and ocular diseases associated with keratoconus, uncontrolled atopic disease, and eye rubbing were excluded. Results: Mean increase in spherical equivalent refraction and simulated keratometry values were 1.4 ± 1.1 and 1.1 ± 0.8 diopters, respectively. In eyes wearing rigid gas-permeable lenses, increase in corneal apical touch and decrease in the base curve radius of the best-fitting contact lens were observed. Conclusions: Hormonal changes during pregnancy may affect corneal biomechanics negatively, and pregnancy may be a previously unrecognized risk factor for progression of keratoconus. To our knowledge, this is the first study showing pregnancy-induced keratoconus progression in patients with no accompanying disease.

Microbiologic study of soft contact lenses after laser subepithelial keratectomy for myopia.

Purpose. To evaluate the extent and agents of bacterial contamination of bandage disposable soft contact lenses after laser subepithelial keratectomy (LASEK) and to correlate the findings with clinical data. Methods. Disposable soft contact lenses were collected from 52 eyes of 26 consecutive patients treated with LASEK for myopia. The patients were treated with a fixed combination of tobramycin and diclofenac until epithelial closure. The lenses were removed on the fourth or fifth postoperative day with sterile forceps and immediately placed in sterile tubes containing culture media brain–heart infusion broth. The lenses were evaluated for microbial colonization. Results. Of the 52 contact lenses analyzed, six (11.5%) had positive cultures. However, no clinical finding of infection was noted. Isolated microorganisms were coagulase-negative staphylococci (two lenses), Stenotrophomonas maltophilia (two lenses), Acinetobacter species (one lens), and Aeromonas hydrophila (one lens). Except for one case, the microorganisms were sensitive to the administered antibiotic. Conclusions. The risk of infectious keratitis after LASEK seems to be low. Except for staphylococci, the isolated microorganisms have not been previously reported to colonize the ocular surface or cause keratitis after refractive surgery. These findings may suggest a changing trend of potentially infectious agents after surface ablation.

Microkeratome-assisted lamellar keratoplasty for keratoconus: stromal sandwich

Purpose: To evaluate microkeratome‐assisted lamellar keratoplasty for the treatment of keratoconus when it is not possible to correct the astigmatic ametropia with contact lenses. Setting: Ophthalmology Department, School of Medicine, Gazi University, Ankara, Turkey. Methods: This prospective study comprised 9 eyes of 7 keratoconus patients with contact lens intolerance. The donor cornea was prepared with a microkeratome and punched with a 7.25 mm or 7.50 mm trephine. Following the creation of a standard 9.0 mm corneal flap in the host cornea, the donor stromal button was implanted under this corneal flap like a sandwich. Transepithelial photorefractive keratectomy or laser in situ keratomileusis was performed when the corneal topography and refraction stabilized by the end of the sixth postoperative month. Follow‐up ranged from 7 to 22 months. Results: All patients gained 5 or more lines (mean 7.2 lines ± 1.6 [SD]), and no patient lost a line of vision. The mean corneal thickness was 432.7 ± 36.1 &mgr;m preoperatively and 578.1 ± 45.1 &mgr;m after refractive surgery. Conclusion: The early visual results of this surgical technique are promising and seem to be comparable to those with penetrating keratoplasty.

Excimer laser-assisted anterior lamellar keratoplasty for keratoconus, corneal problems after laser in situ keratomileusis, and corneal stromal opacities

PURPOSE: To evaluate excimer laser‐assisted anterior lamellar keratoplasty to augment thin corneas as in keratoconus (<350 μm) and corneal ectasia after laser in situ keratomileusis (LASIK) and to treat anterior stromal opacities. SETTING: Ophthalmology Department, School of Medicine, Gazi University, Ankara, Turkey. METHODS: Thirteen eyes (5 keratoconus, 3 macular dystrophies, 1 post‐LASIK ectasia, 1 post‐LASIK interstitial keratitis, 3 post‐herpetic keratitis sequelae) of 13 patients were included in this prospective study. The treatment group was divided into corneal ectasia and stromal opacity groups. A donor stromal button approximately 350 μm thick received a 100 μm excimer laser ablation on the endothelium. The remaining cornea (epithelium, Bowmans membrane, and stroma) was punched with a 7.5 or 7.7 mm trephine. After transepithelial ablation of the host cornea to 200 μm thickness, the corneal button was sutured with interrupted 10‐0 monofilament nylon. Sutures were removed between 3 months and 6 months postoperatively. Preoperative and postoperative simulated keratometric cylinders and corneal thickness values were compared using the Wilcoxon signed rank test. The postoperative spherical equivalent refraction and best spectacle‐corrected visual acuity (BSCVA) between the groups were compared using the Mann‐Whitney U test. RESULTS: The mean follow‐up was 27.6 months ± 8.3 (SD). All patients gained 2 lines or more of BSCVA, and no patient lost a line. The mean corneal thickness was 381.2 ± 88.2 μm preoperatively, which significantly increased to 534.9 ± 96.6 μm postoperatively (P<.05). The mean preoperative simulated keratometric cylinder was 7.44 ± 7.18 diopters (D); postoperatively, it decreased to 2.61 ± 1.73 D (P<.05). There was no significant difference in postoperative spherical equivalent refraction or BSCVA between the groups (P>.05). CONCLUSIONS: This technique presents a different modality for the treatment of keratoconus, post‐LASIK corneal problems, and other corneal stromal opacities with anterior lamellar keratoplasty. Additional studies with more patients and longer follow‐up will help determine the role of this technique as a substitute for penetrating keratoplasty in these patients.