Akif Ozdamar

Reproducibility of corneal flap thickness in laser in situ keratomileusis using the Hansatome microkeratome

Purpose: To evaluate the reproducibility of flap thickness during laser in situ keratomileusis (LASIK) and to analyze the effect of preoperative central corneal thickness and corneal keratometric power on flap thickness. Setting: Department of Ophthalmology, Cerrahpasa Medical School, Istanbul, Turkey. Methods: One hundred forty eyes with a mean preoperative pachymetry of 554.4 &mgr;m ± 36.3 (SD) and a mean keratometry of 43.5 ± 1.9 diopters had LASIK using the Hansatome automated microkeratome (Bausch & Lomb Surgical) and a 193 nm argon–fluoride excimer laser (Summit SVS Apex Plus). The 180 &mgr;m microkeratome plate was used in all procedures. Corneal thickness was measured with an ultrasonic pachymeter (Advent, Mentor O&O Inc.) before and during the flap procedure, and the difference was taken as flap thickness. The data were analyzed using a 1‐tailed t test and Pearson correlation coefficient. Results: The mean flap thickness was 120.8 ± 26.3 &mgr;m. There was a low correlation between baseline central corneal thickness and corneal flap thickness (P = .6, r = 0.046). There was no correlation between preoperative keratometry and flap thickness (P = .01, r = 0.203). Conclusions: The Hansatome microkeratome does not always produce a corneal flap of the intended thickness. Factors other than keratometry and pachymetry must affect flap thickness.

Optical coherence tomography for evaluation of anatomical changes in the cornea after laser in situ keratomileusis

Purpose: To examine the use of optical coherence tomography (OCT) in evaluating anatomical changes after laser in situ keratomileusis (LASIK) and complications related to the interface and corneal flap. Setting: Istanbul University Eye Research Center and Department of Ophthalmology, Cerrahpasa Medical School, Istanbul, Turkey. Methods: Eleven eyes of 11 patients who had myopic LASIK were included in the study. Mean age of the 7 men and 4 women was 29.4 years ± 6.9 (SD). Cases analyzed included uneventful LASIK (4 eyes), epithelial ingrowth (5 eyes), and flap striae (2 eyes). Corneas were examined by OCT (Humphrey Systems). Results: Optical coherence tomography resolved corneal flap and residual stromal layers in all cases. The mean thickness of the corneal flap and residual stroma was 138.2 ± 16.5 &mgr;m and 321.7 ± 32.1 &mgr;m, respectively. Interface between the corneal flap and residual stroma was shown by OCT. Optical coherence tomography revealed that the eye with flap striae had flap displacement undetected by biomicroscopy. Epithelial ingrowth was shown as a highly reflective area. Conclusion: Optical coherence tomography appears to be a promising method for evaluating anatomical changes in the cornea after LASIK.

In vitro antimicrobial activity of silicone oil against endophthalmitis-causing agents.

PURPOSE To investigate the antimicrobial activity of silicone oil against endophthalmitis-causing agents in vitro. METHODS The antimicrobial activity of silicone oil was tested on Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, Candida albicans, and Aspergillus spp. The bacteria and fungi were separately inoculated into 1,300 centistokes silicone oil. Control inoculations were done in two different media: physiologic saline and brain-heart infusion (BHI) for bacteria and Sabouraud broth and physiologic saline for fungi. From each medium, 0.001-mL samples were taken and plated in Petri dishes. After overnight incubation, colony-forming units (CFUs) were enumerated. Culturing from the initially prepared specimens, incubating overnight, and counting CFUs was repeated until no growth of microorganisms was seen in the silicone oil-containing media. Macroscopic photography of the colonies and light microscopic photography of microorganisms were performed. RESULTS All the microorganisms showed an apparent decrease in CFUs, with elimination between 7 and 21 days in silicone oil. Colony-forming units of microorganisms remained stable in physiologic saline during the study, with the exception of gradual decrease in CFUs of S. aureus and S. epidermidis from the beginning of the third day. In BHI and Sabouraud broth, both bacteria and fungi showed a growth pattern that was compatible with the growth curve of microorganisms. CONCLUSION Silicone oil has an antimicrobial activity against S. aureus, S. epidermidis, P. aeruginosa, C. albicans, and Aspergillus spp., which are common endophthalmitis-causing agents.

Suprachoroidal Seton Implantation in Refractory Glaucoma: A Novel Surgical Technique

PURPOSE To describe a new surgical technique in which aqueous humor is diverted from the anterior chamber to the suprachoroidal space for the augmentation of uveoscleral outflow in the management of refractory glaucoma. METHODS Four painful-blind eyes of four consecutive patients were included in the study. Mean age of patients was 54.7+/- 9.2 years. Preoperative diagnosis was neovascular glaucoma complicating diabetic retinopathy in three cases and chronic angle-closure glaucoma in one case. Mean preoperative intraocular pressure of the patients receiving two medications was 58.5 +/- 9.2 mm Hg. A modified Krupin eye valve with disk was implanted into the suprachoroidal space. The anterior tube part of the Seton device was placed into the anterior chamber through the long scleral tunnel for draining the aqueous humor from the anterior chamber to the suprachoroidal space. RESULTS The placement of modified Krupin eye valve with disk to the suprachoroidal space was achieved in all cases. While mean preoperative intraocular pressure was 58.5 +/- 9.2 mm Hg, it was 14.2 +/- 4.7 mm Hg at postoperative one week. It was 13.5 +/- 4.6 mm Hg and 15 +/- 4.9 mm Hg at one and three months respectively. At the last follow-up visit, mean intraocular pressure was 17.25 +/- 5.37 mm Hg ranging from 12 to 24 mm Hg. Choroidal detachment was developed in one case and regressed in six weeks. Rubeosis irides regressed at third month in three cases. None of the eyes developed suprachoroidal hemorrhage, retinal detachment, or phthisis bulbi. CONCLUSION The drainage of aqueous humor from the anterior chamber to the suprachoroidal space with the implantation of the glaucoma Seton device is effective in lowering intraocular pressure in refractory glaucoma.

Retinal detachment following laser in situ keratomileusis

OBJECTIVE To report the clinical characteristics, surgical management and outcome of retinal detachment following laser in situ keratomileusis (LASIK) in myopic patients. PATIENTS AND METHODS Retrospective review of 10 eyes of 10 myopic patients with retinal detachment who had previously undergone LASIK surgery were analyzed. Included in the study were 7 males and 3 females, aged 22 to 68 years (35.2+/-2.8). RESULTS Mean spherical equivalent refraction was -10.51+/-3.90 D (ranging from -6.37 D to -17.00 D) before surgery. The time interval between the LASIK procedure and the development of retinal detachment varied from two months to nine months (5.2 +/- 2.78 months). The number of retinal breaks was one in 7 patients, two in 2 patients and three in 1 patient. The type of retinal breaks included 7 patients with horse shoe tears, 1 patient with a retinal hole, 1 patient with a giant retinal tear, and 1 patient with retinal dialysis. Retinal breaks were located anterior to the equator in 9 patients and posterior to the equator in 1 patient. Retinal reattachment was achieved with one operation in 8 eyes (80%) and the remaining 2 eyes required a second surgery for the reattachment of the retina. CONCLUSION This study suggests the possible association between retinal detachment and LASIK procedure in patients with myopia. Clinicians should be aware of retinal pathology predisposing to retinal detachment in patients undergoing LASIK.

Decreased tear secretion after laser in situ keratomileusis for high myopia.

PURPOSE To investigate the changes in tear secretion and tear film stability after excimer laser in situ keratomileusis (LASIK) for high myopia. METHODS One eye of 28 patients underwent unilateral LASIK for the correction of myopia with spherical equivalent refractions ranging from -6.37 to -18.25 D (mean, -11.98 +/- 3.45 D). Schirmer tear test values without anesthesia at 5 minutes and tear break-up time values were measured 4 weeks after LASIK. Unoperated contralateral eyes were used as a control for each patient. The Schirmer tear test and tear break-up time values were analyzed statistically using the independent t-test. RESULTS The mean Schirmer tear test value was 16.17 +/- 2.50 mm in the operated eyes and 21.07 +/- 7.03 mm in the unoperated (control) eyes of the same patients (P = .001). The mean tear break-up time value was 21.0 +/- 3.55 seconds in the operated eyes and 21.27 +/- 6.79 seconds in the control eyes (P = .85). CONCLUSION Tear secretion decreased following LASIK probably due to decrease in corneal sensitivity, but tear film stability appeared unaltered.

CHANGES IN TEAR FLOW AND TEAR FILM STABILITY AFTER PHOTOREFRACTIVE KERATECTOMY

PURPOSE To investigate the changes in tear flow and tear film stability after photorefractive keratectomy (PRK) for myopia. MATERIAL AND METHOD One eye of 32 patients underwent unilateral PRK procedure for the correction of myopia ranging from -1.50 to -6.00 diopters (D) (mean -3.65 +/- 1.55 D). Schirmer test values and break-up time (BUT) scores were measured 6 weeks after the PRK procedure. Unoperated, contralateral eyes were used as control eyes for each patient. The Schirmer test scores and BUT values were statistically analyzed using independent t test. RESULTS The mean Schirmer test value was 14.45 +/- 7.79 mm in the operated eyes. It was 28.83 +/- 5.89 in the control eyes. The decrease in Schirmer test value was statistically significant (t = 8.28, p = 0.0001). The mean BUT scores were 13.19 +/- 5.09 s in the operated eyes and 27.83 +/- 9.31 s in the control eyes. The decrease was statistically significant (t = 7.86, p = 0.0001). CONCLUSION PRK causes a decrease in tear flow and tear film stability that is probably caused by decreased corneal sensation after PRK.

Bioadhesive sulfacetamide sodium microspheres: Evaluation of their effectiveness in the treatment of bacterial keratitis caused by Staphylococcus aureus and Pseudomonas aeruginosa in a rabbit model

The aim of this study was to prepare bioadhesive sulfacetamide sodium (SA) microspheres to increase their residence time on the ocular surface and to enhance their treatment efficacy on ocular keratitis. Microspheres were fabricated by spray drying method using mixture of polymers such as pectin, polycarbophil and hydroxypropylmethyl cellulose (HPMC) at different ratios. The particle size and distribution, morphological characteristics, thermal behavior, encapsulation efficiency, mucoadhesion and in vitro drug release studies on formulations have been investigated. After optimisation studies, SA-loaded polycarbophil microsphere formulation with polymer:drug ratio of 2:1 was found to be the most suitable for ocular application and used in in vivo studies. In vivo studies were carried out on New Zealand male rabbit eyes with keratitis caused by Pseudomonas aeruginosa and Staphylococcus aureus. Sterile microsphere suspension in light mineral oil was applied to infected eyes twice a day. Plain SA suspension was used as a positive control. On 3rd and 6th days of the antimicrobial therapy, the eyes were examined in respect to clinical signs of infection (blepharitis, conjunctivitis, iritis, corneal oedema and corneal infiltrates) which are the main symptoms of bacterial keratitis and then cornea samples were counted microbiologically. The rabbit eyes treated with microspheres demonstrated significantly lower clinical scores than those treated with SA alone. A significant decrease in the number of viable bacteria in eyes treated with microspheres was observed in both infection models when compared to those treated with SA alone. In conclusion, in vitro and in vivo studies showed that SA-loaded microspheres were proven to be highly effective in the treatment of ocular keratitis.

Corneal iron ring associated with iatrogenic keratectasia after myopic laser in situ keratomileusis

A 23-year-old woman had bilateral myopic laser in situ keratomileusis (LASIK). Two months postoperatively, she reported decreased visual acuity. Biomicroscopic examination revealed a corneal epithelial iron ring around the central keratectasia on both corneas. The appearance of the ring pattern was similar to the iron deposits of the Fleischer ring of keratoconus.

Silicone oil in the surgical treatment of endophthalmitis associated with retinal detachment

Purpose: To investigate the useof silicone oil in thepatients who had undergone vitrectomy for the treatment of endophthalmitis associated with retinal detachment.Methods: Six consecutive cases of endophthalmitis associated with retinal detachment were included in the study. The mean age of the 4 males and 2 females was 47.25 ± 23.76 years. Endophthalmitis associated with retinal detachment occurred following perforating injuries in 4 eyes, pneumatic retinopexy in 1 eye and cataract surgery complicated with vitreous loss in 1 eye. Preoperative visual acuity was light perception-only in all eyes. Red reflex was absent in all eyes. All the patients underwent vitreous tapping,encirclement, vitrectomy ,liquid-gasexchange, endolaser photocoagulation and silicone oil injection. Results: Mean follow-up time was 14.3 ± 7.20 months. The microorganisms that were isolated from the vitreous aspiration were Staphylococcus epidermidis in 3 cases, Staphylococcus aureus in 1 case. Remaining cases were culture negative. Retinal breaks could be found in 4 eyes. Inflammation subsided significantly at 5 days in all cases. Final retinal reattachment and treatment of endophthalmitis was achieved in 5 eyes at the end of follow-up . Final visual acuity was 20/40 in 1 case, counting finger in 4 cases and no light perception in 1 case. The postoperative complications were optic atrophy in 1 eye, epiretinal membrane in 2 eyes and phitisis bulbi in 1 eye.Conclusion: Silicone oil, a retinal tamponading agent that has antimicrobial activity, may have benefical effect in the surgical treatment of endophthalmitis associated with retinal detachment.