Sehirbay Ozkan

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.

Determining the lowest trypan blue concentration that satisfactorily stains the anterior capsule

Purpose: To determine the lowest concentration of trypan blue that will stain the anterior capsule satisfactorily to perform a safe continuous curvilinear capsulorhexis and to describe a staining technique using a dispersive viscoelastic material. Setting: Cerrahpasa School of Medicine, University of Istanbul, Istanbul, Turkey. Methods: Trypan blue 0.1% (Vision Blue®) was diluted by half by adding an equal volume of balanced salt solution (BSS®) in a stepwise pattern continuously until the concentration failed to stain the anterior capsule satisfactorily. After the dilution, 4 concentrations of the dye were obtained: 0.050%, 0.025%, 0.0125%, and 0.00625%. The volume of dye used for staining was 0.1 cc at all concentrations. Each concentration of the dye was applied using a classic air‐bubble technique or a technique in which the dye was injected under sodium hyaluronate 3.0%‐chondroitin sulfate 4.0% (Viscoat®) onto the anterior lens surface without using an air bubble to reform the anterior chamber. Each diluted concentration was used in 10 eyes by the same surgeon, with 5 eyes having the air‐bubble technique and 5 having the viscoelastic technique. The 0.1% concentration was used in 5 eyes, all having the viscoelastic technique. Results: Trypan blue in concentrations as low as 0.0125% stained the anterior capsule satisfactorily. In addition, staining was possible under the Viscoat. The viscoelastic technique was faster, safer, and easier to perform than the air‐bubble technique. Conclusions: As trypan blue is a potentially carcinogenic vital dye and its possible long‐term side effects are unknown, the lowest effective concentration should be used. A concentration lower than 0.1% was effective in staining the anterior capsule even under dispersive viscoelastic material.

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.

Interleukin-8, Nitric Oxide and Glutathione Status in Proliferative Vitreoretinopathy and Proliferative Diabetic Retinopathy

Purpose: To evaluate interleukin-8 (IL-8), nitric oxide (NO) and glutathione (GSH) profiles in vitreous humor and blood samples in patients with proliferative diabetic retinopathy (PDR) and in patients with proliferative vitreoretinopathy (PVR) and to compare the levels with those of controls. Patients and Methods: NO concentrations were determined by using the Greiss reaction in plasma and vitreous humor samples. GSH levels were determined in both blood and vitreous humor samples, using DTNB, a disulfide chromogen. Vitreous IL-8 were assayed by ELISA. Twenty-three patients with PDR, 18 patients with PVR and 21 cadavers as the control group were included in the study. Results: Plasma and vitreous NO levels were found to be25.6 ± 2.1 and 36.9 ± 3.0 µmol/l in patients with PDR, 27.0 ± 4.7 and 34.3 ± 2.9 µmol/l in patients with PVR and 17.4 ± 2.7 and 15.9 ± 1.4 µmol/l in controls, respectively. Vitreous humor and plasma NO levels did not show any statistically significant difference between PDR and PVR groups. However, the values for vitreous in both groups were significantly higher than those of controls (p < 0.0001). Although IL-8 levels in vitreous samples of patients with PDR were not significantly different (79.6 ± 9.7 pg/ml) from those of patients with PVR (42.2 ± 7.3 pg/ml) (p = 0.06), the levels in both groups were significantly higher than those of controls (19.0 ± 3.9 pg/ml) (p < 0.0001 and p < 0.05, respectively). Blood and vitreousGSH levels were found to be5.3 ± 0.4 µmol/g·Hb and 0.58 ± 0.16 µmol/l in patients with PDR and 8.4 ± 0.5 µmol/g·Hb and 15.7 ± 2.2 µmol/l in patients with PVR and 12.0 ± 1.1 µmol/g·Hb and 0.26 ± 0.03 mmol/l in controls, respectively. Vitreous and blood GSH levels were significantly lower in patients with PDR compared to those with PVR (p < 0.0001 for both). Conclusion: Elevated levels of vitreous and plasma NO and vitreous IL-8 in PDR and PVR implicate a role for these parameters in the proliferation in these ocular disorders. GSH concentrations both in vitreous and blood samples of the PVR and PDR patients were much less than those observed in the control group. Lower GSH concentrations detected in PDR in comparison with those in PVR in vitreous humor and to a lesser degree in blood may play an important role in pathogenesis of new retinal vessel formation in patients with PDR. This also suggests that oxidative stress may be involved in the pathogenesis of PVR and particularly that of PDR.

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.

Treatment of Xanthelasma Palpebrarum with Argon Laser Photocoagulation

Purpose: We report the results of argon laser coagulation of xanthelasma lesions. Methods: Forty eyelids of 24 patients with xanthelasma were treated in 1 to 4 sessions at 2–3 week intervals, using an argon green laser. The laser parameters were as follows: wavelength 514 nm; spot size 500 microns; energy 900 mW; the duration of the laser pulse 0.1–0.2 seconds. The procedure was done on outpatient basis. A gauze pad soaked in topical anaesthetic eye drops was applied to the surface of the lesion. Results: The therapy was well tolerated, and all lesions responded to the therapy. There were no complications and no functionally relevant scar developed. The cosmetic outcome was considered to be good in 85% of the cases. Conclusion: Argon laser photocoagulation represents an alternative treatment in selected cases. It is easy to perform and well tolerated by the patients.

Structural features of attached retina in rhegmatogenous retinal detachments.

Purpose To examine the thickness and structural features of the ophthalmoscopically normal-appearing, attached retina in rhegmatogenous retinal detachments by optical coherence tomography (OCT) and compare them with those of the fellow eye. Methods Seventy eyes of 35 patients with rhegmatogenous retinal detachments were included in this study. The retinal detachments were not total. None of the patients had pathologic myopia or a history of ocular surgery. The fellow eyes were ophthalmoscopically normal and used as controls. Attached retinal sites of the eyes with a retinal detachment and the corresponding retinal sites of the fellow eyes were examined by OCT. Three OCT sections were taken from each eye, and thicknesses of three reflective zones corresponding to the inner part of the neurosensory retina (partial neurosensory retina), photoreceptor–photoreceptor outer segment, and total retinal thickness on each OCT section were measured and compared with those of the fellow eye. These three measurements were taken as the main outcome measures and performed on five different sites of each OCT section taken from each eye. Results The mean partial neurosensory retinal thickness of the attached retina in the eyes with a retinal detachment and the corresponding retinal sites in the fellow eyes was 172.74 ± 14.23 &mgr;m and 170.60 ± 16.51 &mgr;m, respectively. There was no statistically significant difference between these two values. The mean photoreceptor outer segment thickness of the attached retina in the eyes with a retinal detachment and the corresponding retinal sites in the fellow eyes was 62.74 ± 12.02 &mgr;m and 58.23 ± 15.14 &mgr;m, respectively. There was a statistically significant difference between these two values. The mean total retinal thickness of the still-attached retina in the eyes with a retinal detachment and the corresponding retinal sites in the fellow eyes were 293.23 ± 27.87 &mgr;m and 277.06 ± 19.12 &mgr;m, respectively. There was a statistically significant difference between these two values. Conclusions The main difference between the two groups of eyes was at the level of the thickness of the black hyporeflective zone, corresponding anatomically to the photoreceptor and photoreceptor outer segment that enlarges in the retinal detachments. Therefore, there may be a subclinical retinal detachment or a global retinal relaxation even in the ophthalmoscopically normal-appearing, still-attached retina. This may be the underlying cause of preoperative and postoperative signs and symptoms. Additional studies are required to confirm these findings.

The effect of artificial tears on corneal surface regularity in patients with Sjögren syndrome

Purpose: To evaluate the effect of artificial tears on the topographic parameters associated with corneal surface regularity in patients with Sjögren syndrome. Methods: A total of 38 eyes of 20 patients with Sjögren syndrome were evaluated prospectively. The mean age of the patients was 50.5 ± 15.3 years (range, 28–76). Corneal topography with the Topographic Modeling System (TMS-2, Tomey) was performed before and after the instillation of artificial tears. The surface regularity index (SRI), surface asymmetry index (SAI), potential visual acuity (PVA) and mean astigmatism were compared in dry eyes before and after the instillation of artificial tears. Results: Before the instillation of artificial tears SAI, SRI, PVA and mean antigmatism values were found to be 1.37 ± 1.47, 0.74 ± 0.42, 20/30.92 ± 20/8.12 and 1.53 ± 1.47 D, respectively. In corneal topography performed after the instillation of artificial tears SAI, SRI, PVA and mean astigmatism values were 0.71 ± 0.82, 0.43 ± 0.36, 20/25.92 ± 20/5.55 and 1.08 ± 1.18, respectively. When compared statistically, the SRI, SAI, and mean astigmatism all decreased significantly and the PVA improved (p = 0.0001). Conclusion: Irregular corneal surface in dry eye patients affects optical quality. The statistically significant improvement observed in SRI and SAI values after the instillation of artificial tears also improves the PVA that is especially related to SRI.