An in vivo confocal microscopy study of corneal changes in pseudoexfoliation syndrome.

PURPOSE: To evaluate, through the in vivo confocal microscopy, the pathological changes of each corneal layer in eyes affected by pseudoexfoliation syndrome. METHODS: We studied 40 eyes of 40 patients with diagnosis of unilateral senile cataract associated with pseudoexfoliation syndrome and 40 eyes of 40 control subjects with senile cataract without pseudoexfoliation syndrome. All patients underwent a complete ophthalmic examination including best corrected visual acuity, slit-lamp examination, corneal sensitivity measurement using a Cochet-Bonnet nylon thread esthesiometer, and anterior segment optical coherence tomography (Visante OCT, Carl Zeiss Meditec AG, Germany); in vivo confocal microscopy of corneal sections (endothelium, stroma, sub-basal nerve plexus, and superficial and basal epithelium) was performed with the ConfoScan 4.0 (Nidek, Japan). RESULTS: In pseudoexfoliation syndrome group, the mean corneal sensitivity was 44.1 ± 1.3 mm and in the control group was 55.6 ± 4.7 mm. The corneas of the eyes with pseudoexfoliation syndrome were significantly less sensitive than those of control group eyes (p < 0.001). Pseudoexfoliation syndrome eyes had a lower nerve density and less nerve beadings and a higher degree of tortuosity in sub-basal plexus compared to the control group. The cell density of epithelial and endothelial layers was significantly lower in pseudoexfoliation syndrome eyes than controls. In 80% of pseudoexfoliation syndrome eyes, we found activated keratocytes and inflammatory cells in the anterior stroma. CONCLUSION: Our study demonstrates the morpho-structural corneal alterations in eyes affected by pseudoexfoliation syndrome, using corneal in vivo confocal microscopy as a non-invasive and high-reproducible technique to evaluate pathophysiology of each corneal layer; the sub-basal nerve plexus alterations are correlated with the lower corneal sensitivity.

Investigating the ocular temperature rise during femtosecond laser lens fragmentation: an in vitro study.

PURPOSE: To investigate the trend of temperature variation during lens fragmentation simulated by a femtosecond laser on an in vitro eye model. METHODS: In our experimental study, a convex cylinder of gelatinous material, usually employed in femtosecond laser calibration, was used to simulate both an anterior segment and a crystalline lens during fragmentation performed with the Victus femtosecond laser (Technolas Perfect Vision GmbH, Germany; Bausch + Lomb Incorporated, USA). Two radiated energies (7000 nJ and 9000 nJ) and three cutting patterns (crosses, circles and cross + circle) were applied. Trends of temperature variation as a function of time were obtained using a T-type thermocouple. RESULTS: The maximum value of temperature rise during lens fragmentation ranged from 3.53 to 5.13 °C; the rise was directly proportional to the intensity of the radiated energy (7000 nJ or 9000 nJ) and the cutting pattern performed. This behavior was experimentally represented by an asymmetric function with a characteristic bell curve shape, whereas it was mathematically described by a transport diffusive model. CONCLUSIONS: Since the temperature rise at the fragmentation volume base resulted to be around 5 °C in our in vitro study, lens fragmentation performed using the Victus femtosecond laser might be considered safe form a thermal point of view.

In vivo thermographic analysis of the corneal surface in keratoconic patients undergoing riboflavin-UV-A accelerated cross-linking.

PURPOSE: To assess corneal thermal profile during combined riboflavin and accelerated UV corneal collagen cross-linking (A-CXL) using in vivo surface thermographic analysis. METHODS: In this open-label, nonrandomized, prospective pilot study, 28 eyes of 28 patients were included. The study was conduced at the Department of Surgery and Translational Medicine, University of Florence, Italy, in collaboration with the Ophthalmic Operative Unit of Siena University, Italy. All patients underwent high-fluence A-CXL in pulsed light and continuous light UV-A exposure at 30 and 18 mW/cm. Patients were divided into 4 groups: 7 for continuous light A-CXL, 7 for pulsed light A-CXL at 30 mW/cm with 7.2 J energy, 7 for continuous light A-CXL, and 7 for pulsed light A-CXL at 18 mW/cm with 5.4 J energy. Corneal surface temperature measurements were recorded using an infrared FLIR thermocamera (FLIR 320A; FLIR Systems). Corneal temperature values were detected in the surface area exposed to UV-A light irradiation, selecting it in the acquired thermographic image. The maximum temperature value detected in the area studied was recorded and considered for comparative analysis. RESULTS: Infrared thermocamera measurements of the corneal surface during A-CXL treatments showed an average temperature of 31.5°C during the entire procedure in all groups and UV-A powers (30 mW/cm at 7.2 J/cm and 18 mW/cm at 5.4 J/cm) and light exposure modality remained under the threshold of collagen thermal injury. CONCLUSIONS: Accelerated corneal collagen cross-linking did not cause thermal rise over the threshold of thermal injury to the corneal surface, demonstrating a safe thermal profile both at 30 mW/cm with 7.2 J and 18 mW/cm with 5.4 J energy dose.