Georgios Labiris

Corneal collagen cross-linking using riboflavin and ultraviolet-A irradiation: a review of clinical and experimental studies

Corneal collagen cross-linking (CXL) using riboflavin and ultraviolet-A irradiation is a common method of tissue stabilization and has been developed primarily to address the need of treating keratoconus. CXL’s promising results on keratoconus indicated that it might be effective in other corneal diseases as well. This new treatment promises a slowing effect on the progression of these diseases and its initial results show that it is safe and reasonably curative. The purpose of this review is to critically evaluate this treatment, to explore its benefits, to highlight its limitations in terms of efficacy and long-term safety and finally to identify areas for future research in this topic with a significant potential to change the way we treat our patients. In addition, in this unbiased review we try to bring together all the scientific information from both laboratory and clinical trials that have been conducted during recent years and to review the most recent publications regarding the therapeutic indications of CXL.

Anterior chamber volume measurements with Visante optical coherence tomography and Pentacam: repeatability and level of agreement

Background:  The purpose of this study is to examine the repeatability of Pentacam‐derived anterior chamber volume measurements, and assess the level of agreement of anterior chamber volume measurements obtained with the Visante and the Pentacam imaging devices.

Repeatability, reliability and reproducibility of posterior curvature and wavefront aberrations in keratoconic and cross-linked corneas.

The aim was to assess the intra‐session, inter‐session and inter‐observer repeatability of curvature and aberrometric measurements of Pentacam‐derived posterior corneal surface in normal control (CG), keratoconic (KCG) and after corneal collagen cross‐linked (CXLG) groups.

Ocular decompression retinopathy after deep sclerectomy with mitomycin C in an eye with exfoliation glaucoma.

Purpose TO present a case of ocular decompression retinopathy occurring after an uncomplicated nonpenetrating glaucoma procedure (deep sclerectomy with mitomycin C). Methods A 52-year-old man with medically uncontrolled exfoliation glaucoma in the left eye underwent uneventful deep sclerectomy with mitomycin C. The patient had no history or laboratory evidence of any bleeding disorder. Results On the first postoperative day, visual acuity fell from the preoperative level of Snellen 0.2 to hand movement and the intraocular pressure was 5 mmHg. Funduscopy revealed a small intravitreal hemorrhage and multiple, extended retinal hemorrhages in all quadrants of the fundus. After standard postoperative medication with antibiotic/steroid eyedrops, the patients visual acuity returned to preoperative levels and the retinal hemorrhages were absorbed. Three and a half months postoperatively, the fundus was free of bleedings. Conclusions Although decompression retinopathy has previously been described after penetrating glaucoma surgery, the condition can also occur after uncomplicated deep sclerectomy. Despite the dramatic presentation, the prognosis remains favorable.

Physical activity and its correlation to diabetic retinopathy.

PURPOSE The lack of physical activity, along with obesity, smoking, hypertension and hyperglycaemia are considered as risk factors for the occurrence of diseases such as diabetes. Primary objective of the study was to investigate potential correlation between physical activity and diabetic retinopathy. PATIENTS AND METHODS Three hundred and twenty patients were included in the study: 240 patients with diabetes type 2 (80 patients with mild to moderate non-proliferative diabetic retinopathy, 80 patients with severe to very severe non-proliferative diabetic retinopathy and 80 ones with proliferative diabetic retinopathy) were compared with 80 non-diabetic patients (control group). Physical activity of patients was assessed by the international physical activity questionnaire (IPAQ, 2002). HbA1c and BMI were also measured in diabetic patients. Group comparisons were attempted for levels of physical activity and sedentary behavior. RESULTS Total physical activity was decreased in patients with severe to very severe non-proliferative diabetic retinopathy and proliferative diabetic retinopathy as compared to patients with mild to moderate non-proliferative diabetic retinopathy and to the control group (p<0.05). Significant negative correlation was detected between HbA1c levels, BMI and physical activity (both p<0.05). Moreover, significant negative correlation between the severity of diabetic retinopathy and physical activity has been demonstrated (p<0.05). CONCLUSIONS Increased physical activity is associated with less severe levels of diabetic retinopathy, independent of the effects of HbA1c and BMI.

Tonometry in keratoconic eyes before and after riboflavin/UVA corneal collagen crosslinking using three different tonometers.

Purpose To evaluate the Goldmann applanation tonometer (GAT), the Pascal dynamic contour tonometer (PDCT), and the ocular response analyzer (ORA) tonometer in measuring intraocular pressure (IOP) in keratoconic eyes before and after riboflavin/ultraviolet A corneal collagen crosslinking (CXL), to assess agreement among devices and to analyze the impact of some ocular parameters on their measurements. Methods Fifty keratoconic eyes were included. Intraocular pressure was measured with GAT, PDCT, and ORA before and after CXL. Fifty nonkeratoconic eyes served as controls. Device agreements were calculated by Bland-Altman analysis. The effect of some ocular characteristics on IOP measurement differences between tonometers was determined. Results Between the 2 groups, there were statistically significant differences in all examined parameters. Preoperatively, in both groups a statistically significant difference was found in IOP measurements among devices (p<0.05). Bland-Altman analysis showed a bias among devices. On average, PDCT overread GAT and ORA. The IOP measurement differences were better predicted by corneal resistance factor. Postoperatively, in keratoconus eyes, there was no statistically significant difference in IOP measurements among the 3 tonometers (p>0.05). The IOP readings with all tonometers after treatment were higher than those obtained preoperatively; however, not to a statistically significant level, with the exception of PDCT and ORA readings at the first month postoperatively. Corneal resistance factor measurements have no significant change after CXL. Conclusions Pascal dynamic contour tonometer could provide more consistent and closer to the true IOP readings than GAT and ORA in healthy eyes with corneal thickness outside the 520-550 μm range, in keratoconus patients and after CXL. Corneal resistance factor was associated significantly with agreement among devices.

Laser in situ keratomileusis flap-thickness predictability with a pendular microkeratome

PURPOSE: To assess flap‐thickness predictability with a pendular microkeratome (130 μm head). SETTING: Eye Institute of Thrace, Democritus University of Thrace, Alexandroupolis, Greece. DESIGN: Clinical trials. METHODS: The study comprised 263 eyes (132 patients). Laser in situ keratomileusis was performed using the 130 μm head of the Carriazo pendular microkeratome; right eyes were treated first. Ultrasound pachymetry and topography were used for central corneal thickness (CCT) and keratometry (K) measurements. Evaluation included flap thickness, flap diameter, and flap shape. RESULTS: The mean flap thickness was 125 μm ± 22 (SD) (range 74 to 187 μm) in right eyes and 112 ± 21 μm (range 61 to 190 μm) in left eyes. Flap thickness was significantly correlated with preoperative CCT (r = 0.271; P<.001) but not with K values or the manifest refraction spherical equivalent (P>.15). Right eyes had thicker flaps than left eyes (P<.001); both were significantly below the 130 μm head thickness (mean flap thickness 119.2 ± 22.8 μm; P<.001). The mean achieved flap diameter was 9.2 mm using the 9.0 ring and 9.8 mm using the 10.0 mm ring. Flap‐thickness stabilization and convergence between right eyes and left eyes occurred after 100 consecutive flap cuts. CONCLUSIONS: Flap‐thickness predictability was influenced by preoperative CCT only. All cuts were significantly thinner than the head thickness regardless of the suction ring size. Second surgical eyes had thinner flaps, possibly from blade deterioration from the first cut. Approximately 100 flaps were required as a learning curve. Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned.

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.

The Effect of Corneal Refractive Surgery on Glaucoma

Laser-assisted refractive procedures have become very popular in the last two decades. As a result, a “generation” of patients with altered corneal properties is emerging. These patients will require both cataract extraction and glaucoma follow-up in the future. Since the glaucoma examination largely depends on the corneal properties, the reshaped postrefractive surgery cornea poses a challenge in the diagnosis, follow-up, and management of the glaucomatous patient. In order to overcome this problem, every patient who is planned to undergo corneal refractive surgery must have a thorough glaucoma examination in order for the ophthalmologist to be able to monitor their patients for possible glaucoma development and/or progression. Some examinations such as tonometry are largely affected by the corneal properties, while others such as the evaluation of the structures of the posterior pole remain unaffected. However, the new imaging modalities of the anterior segment in combination with the most recent advances in tonometry can accurately assess the risk for glaucoma and the need for treatment.

Thyroidopathy and Age-Related Macular Degeneration: Is There Any Correlation

Purpose: The purpose of this study was to evaluate whether inherent sociodemographic parameters, lifestyle features, as well as medical data may be potential risk factors for the presence of age-related macular degeneration (AMD). Methods: Participants in our study were 114 patients with AMD, 63 males and 51 females, and 100 control subjects without any ocular disease. Demographic data, lifestyle data, medical history, and comorbidities were recorded and analyzed as potential risk factors for the presence of AMD. Results: There was no statistically significant difference between patients and controls regarding age, gender, smoking, alcohol consumption, walking, exercise, presence of hypertension, diabetes mellitus, myoskeletal problems, migraine, and cancer. Marital status, higher educational level, cardiovascular disorders, and thyroidopathy were found to be significantly associated with AMD. Conclusions: Apart from already reported risk factors for AMD, thyroidopathy was associated with AMD.