Irini Naoumidi

Epi-LASIK: Comparative histological evaluation of mechanical and alcohol-assisted epithelial separation

Purpose: To compare the effect of mechanical and alcohol‐assisted excision on the histological ultrastructure of epithelial disks from human corneas. Setting: Vardinoyiannion Eye Institute of Crete, University of Crete, Medical School, Crete, Greece. Methods: Ten eyes of 10 patients were deepithelialized by 1 of 2 two techniques. In 6 eyes, a customized instrument was used to mechanically separate the epithelial layer. In 4 eyes, the epithelial disks were obtained using the conventional laser‐assisted subepithelial keratectomy (LASEK) technique; that is, with alcohol concentrations of 15% and 20%. All specimens were assessed by light and electron microscopy, and the histological findings of the 2 methods were compared. Results: Transmission electron microscopy showed that when the epithelial disks were excised by mechanical separation, the lamina densa and lamina lucida were preserved and the hemidesmosomes had normal morphology along almost the entire length of the basement membrane. The basal epithelial cells of the separated epithelial disks showed minimal trauma and edema. Specimens obtained using 15% and 20% alcohol concentrations showed formation of cytoplasmic fragments of the basal epithelial cells, enlargement of the intercellular spaces, and extensive discontinuities in the basement membrane, which was excised at the level of the lamina lucida. Conclusions: Mechanical separation did not affect the normal cell morphology of the excised epithelial disks. Transmission electron microscopy of the specimens proved the manual technique is less invasive to epithelial integrity than LASEK using either alcohol concentration.

Comparative study of stromal bed of LASIK flaps created with femtosecond lasers (IntraLase FS150, WaveLight FS200) and mechanical microkeratome

Background/aim To compare stromal bed smoothness in LASIK flaps created with two different femtosecond lasers (IntraLase FS150 and WaveLight FS200) and a mechanical microkeratome (MMK) (Carriazo-Pendular microkeratome). Methods Sixty freshly enucleated porcine eyes were used for the study. Twenty flaps were created and constitute each of the following three groups: IntraLase FS150 (IFS group), WaveLight FS200 (WFS group) and MMK (MMK group). In each of the three groups, 10 flaps were created with intended thickness of 110 μm and another 10 flaps with 130 μm. Images were assessed with light microscopy and scanning electron microscopy. Qualitative surface roughness grading of the images was performed by five masked observers and statistical comparisons of scores were made between groups. Results The results of qualitative surface roughness grading demonstrated that there was no significant difference between the two femtosecond (FS) lasers when comparing the subgroups with the same flap thickness (p>0.05 in both comparisons, Mann–Whitney U test). In addition, there was no statistically significant difference (p>0.05) in each flap maker group between different thickness subgroups. However, the scores of the FS laser subgroups were significantly better than the scores of the MMK subgroups with corresponding flap thicknesses (p<0.05, Mann–Whitney U test). Conclusions Our study demonstrates that the IntraLase FS150 and the WaveLight FS200 had a similar performance and provided flaps with smooth surfaces. In comparison to the MMK, the studied femtosecond laser systems had a superior performance in terms of smoothness.

Photorefractive Keratectomy Using Solid State Laser 213 nm and Excimer Laser 193 nm: A Randomized, Contralateral, Comparative, Experimental Study

PURPOSE To compare histopathologic changes after photorefractive keratectomy (PRK) for myopia using either a solid state laser (SSL) at 213 nm or an excimer laser (EL) at 193 nm in an experimental model. METHODS Forty pigmented rabbits (80 eyes) underwent myopic PRK for the correction of 6 D. Photoablation was randomly assigned, with a solid state laser used in one eye and an EL in the fellow eye. Rabbits were killed immediately after ablation (n = 10) or at 7 days (n = 10), 1 month (n = 8), 3 months (n = 6), or 12 months (n = 6) after surgery. Corneal tissue was preserved for light microscopy and transmission electron microscopy at all postoperative intervals. RESULTS All eyes reepithelialized in 1 week with no early or late postoperative complication. Immediately after ablation, light, scanning, and transmission electron microscopy revealed relatively smooth ablation surfaces in both groups. Seven days after surgery, epithelium in the SSL specimens appeared thinner than in the EL specimens. Activated keratocytes were observed adjacent to the epithelium in both groups, whereas endothelial cells demonstrated normal morphology. At 1, 3, and 12 months after surgery, tissue appearance of all corneal layers was similar in both groups. CONCLUSIONS PRK in rabbits using ultraviolet SSL and EL revealed similar histopathologic findings up to 1 year after surgery.

Automated Donor Tissue Preparation for Descemet Membrane Automated Endothelial Keratoplasty (DMAEK): An Experimental Study

BACKGROUND AND OBJECTIVE Graft harvesting for Descemet membrane endothelial keratoplasty (DMEK) occurs manually and demonstrates surgical difficulties. In the current study, a mechanical automated technique for preparing a donor Descemet membrane (DM) carrying autologous endothelium for DMEK was evaluated. MATERIALS AND METHODS Ten rabbit corneas were placed on an artificial anterior chamber and mechanical separation of the DM was conducted using an Epi-keratome (Senturium; Norwood Abbey EyeCare, Victoria, Australia). All DM specimens were properly fixated and optical microscopy was performed. RESULTS DM separation was achieved in a controlled fashion in 7 of 10 eyes. As demonstrated by optical microscopy of the specimens, no corneal stroma was attached on the DM, whereas the endothelial layer was preserved in several areas. CONCLUSION Automated separation of the DM can be achieved using an Epi-keratome. Additional studies and improvements of the current technique are needed to draw final conclusions.

Narrow angle light scatter in rabbit corneas after excimer laser surface ablation.

Corneal haze following excimer laser ablation is an adverse after‐effect of photorefractive keratectomy (PRK) and is associated with the development of subepithelial opacities. The present work pertains to the measurement of light scattering in rabbit corneas following excimer laser treatment; to the microscopic analysis of the light‐scattering corneal structures; and to the development of a mathematical model of light propagation through the post‐laser treatment cornea. Photorefractive keratectomy (PRK‐6D, 6 mm optical zone) followed by standard postoperative pharmaceutical treatment was performed on rabbit eyes. Animals were examined clinically on a weekly basis and sacrificed after the tenth postoperative week. Confocal microscope image sequences were acquired immediately before animal sacrifice. After the scatter measurement, the corneas were prepared for histopathological evaluation. The subepithelial structures observed using the confocal microscope correspond to refractive index (and therefore optical path difference (OPD) variation. This OPD distribution can be approximated with a fractal surface, band‐pass filtered in the Fourier domain. The angular distribution of scattered light is characterised by a narrow forward peak of the order of 0.5° full‐width at half maximum (FWHM) in accordance with the sizes of the subepithelial structures (5–150 μm).The intensity of scattered light is correlated with the thickness of the subepithelial scar‐tissue layer.

Transscleral Ciliary Body Photodynamic Therapy Using Phthalocyanine and a Diode Laser: Functional and Morphologic Implications in Albino Rabbits

BACKGROUND AND OBJECTIVES To evaluate the morphologic and functional effects of ciliary body photodynamic therapy (PDT) using phthalocyanine and a diode laser. MATERIALS AND METHODS The upper half of the left eye ciliary body of 16 albino rabbits was irradiated transsclerally using a 670-nm diode laser (400 mW/cm2) after intravenous injection of phthalocyanine (6 mg/kg). The animals were observed for a maximum of 2 months by means of tonometry, biomicroscopy, and fundus examination. At the end of the follow-up period, they were killed and their eyes were prepared for light and electron microscopy. RESULTS Transscleral PDT resulted in intraocular pressure (IOP) reduction in the treated eye, which lasted about 2 weeks. During this time, the treated eye had IOP values that were significantly lower than its baseline IOP values and the IOP values of the untreated eye (P < .05). One month after the procedure, the IOP had returned to baseline values. Histologic examination revealed vascular endothelial cell damage causing vascular thrombosis in the treated areas. The architecture of the two ciliary epithelium layers showed a significant abnormality. Disappearance of epithelial apical junction complexes and loss of the normal b-cytomembrane enfolding were observed in the course of electron microscopic examination. Large intercellular spaces between epithelial cells were noticed. All of these changes had subsided by the end of the second postoperative month. CONCLUSION Transscleral phthalocyanine-mediated PDT with the parameters used in this experiment results in significant but temporary functional and morphologic alterations in the ciliary bodies of albino rabbits.

Evaluation of Vitreous Clearance and Potential Retinal Toxicity of Intravitreal Lornoxicam (Xefo)

PURPOSE To evaluate the vitreous clearance and toxicological profile of commercially available lornoxicam (Xefo), after a single intravitreal injection in rabbits. METHODS Twenty-five male albino rabbits (10 rabbits were used for retinal toxicity evaluation, while 15 rabbits were used to evaluate vitreous clearance) were used in this study. Two concentrations of lornoxicam were tested for retinal toxicity: 250 μg/0.1 mL and 1,500 μg/0.1 mL. Each concentration was intravitreally injected randomly in 1 eye of each rabbit (group I received 250 μg/0.1 mL, n=5 and group II received 1,500 μg/0.1 mL, n=5), while in the other eye 0.1 mL of sterile balanced saline solution was injected. Slit-lamp and funduscopic examinations along with intraocular pressure measurements (IOP) were performed prior to injection and at days 1, 15, and 30 after the injection for signs of infection, inflammation, toxicity, and IOP changes. A baseline electroretinogram (ERG) was performed before the experiment and at days 1, 15, and 30 after the intravitreal injection. At the last follow-up day, the animals were sacrificed and the enucleated eyes were prepared for histological evaluation of the retina. Lornoxicam (concentration of intravitreal injection: 250 μg/0.1 mL) clearance from the vitreous was estimated using high-performance liquid chromatography in 30 rabbit eyes. RESULTS There were no statistical differences between the control and experimental eyes, concerning ERG amplitudes and IOP measurements for both groups (I and II), at all examinations. On the contrary, histological examination of the samples revealed extended retinal damage of group II experimental eyes (morphological alterations at the level of the inner nuclear and outer plexiform layers was evident along with disappearance of normal stratification of outer retina with vacuolization and thinning), whereas the morphology of group I experimental eyes did not differ from that of the control eyes. Lornoxicam is eliminated from the vitreous by a first-order kinetic process with a half-life of 1.7 h. CONCLUSIONS Intravitreal lornoxicam causes dose-related toxic effect to the retina at a concentration of 1,500 μg. A dose of 250 μg does not seem to cause histological toxic effects at the level of the retina. Lornoxicam could be considered with interest for further research for the development of alternative treatments for ocular inflammatory conditions.

The PALM Technique: histological findings of masked phototherapeutic keratectomy on rabbit corneas

BackgroundTo compare the corneal healing response between conventional and phototherapeutic keratectomy through a masking agent, in rabbit corneas.Methods24 adult rabbits underwent phototherapeutic keratectomy. Animals were divided in two groups: 12 received photoablation through a masking agent (PALM gel) and the remaining 12 received conventional phototherapeutic keratectomy of equal depth and served as control. Light and transmission electron microscopy was performed in specimens of both groups obtained: immediately after, four hours, one week, one, three and six months after treatment.ResultsReepitheliazation was complete within five days in all eyes. Light and transmission electron microscopy did not reveal any differences of the healing process in the experimental eyes compared to the controls.ConclusionPhotoablation through the PALM technique did not result any evident alterations of the reepithelisation and stromal healing process.

Effect of Riboflavin/UVA Collagen Cross-linking on Central Cornea, Limbus and Intraocular Pressure. Experimental Study in Rabbit Eyes.

The Purpose of present study was to investigate the effect of riboflavin/ultraviolet-A-induced collagen cross-linking (CXL) on central cornea, limbus and intraocular pressure (IOP). This was an animal experimental study. The right corneas of 10 rabbits were ultraviolet-A irradiated (3 mW/cm2 for 30 minutes) after de-epithelialization and instillation of 0.1% riboflavin / 20% Dextran drops. Left corneas served as controls. Samples were examined histologically one month postoperatively. Before and after treatment, IOP measurements were recorded bilaterally. At central cornea of eyes underwent CXL keratocyte repopulation, normal arrangement of collagen fibres and a statistically significant change in fibres diameter were detected, compared to controls. At limbus area, there were not any significant histological differences after CXL. There was no statistically significant difference between pre- and postoperative IOP in all eyes.

Mini descemet membrane stripping (m-DMES) in patients with Fuchs’ endothelial dystrophy: A new method

We present two cases with focal corneal edema due to Fuchs’ endothelial dystrophy that were successfully treated with mini Descemet membrane stripping (m-DMES) (diameter of 3–4 mm; at the area of preexisting focal corneal edema) without endothelial replacement during cataract surgery. Specular microscopy demonstrated Fuchs’ endothelial dystrophy and histopathologic evaluation confirmed the diagnosis. Anterior segment optical coherence tomography and confocal microscopy were used for the evaluation of the corneal tissue recovery course after the surgical procedure. In both patients, we observed an initial aggravation of corneal edema in the area of DM removal for two months followed by gradual improvement. At four months postoperatively, corneal edema had completely regressed resulting in corneal clearance and visual acuity improvement in both cases. M-DMES without graft insertion represents a promising alternative surgical technique that could be applied in specific cases of Fuchs’ endothelial dystrophy with focal corneal edema.