Riboflavin and ultraviolet A collagen crosslinking: in vivo thermographic analysis of the corneal surface.

PURPOSE: To assess the possible thermal damage to the cornea during combined riboflavin and ultraviolet-A crosslinking using in vivo surface thermographic analysis. SETTING: Department of Oto-Neuro-Ophthalmological Surgical Sciences, Eye Clinic, University of Florence, Florence, Italy. METHODS: Collagen crosslinking was performed on a day-surgery basis under aseptic conditions with traditional techniques. During the procedure, temperature measurements on the corneal surface were taken using an infrared thermocamera. The temperature values were detected in the area directly exposed to light irradiation, selecting it in the acquired thermographic image. Because the aim of the study was to consider the thermal damage that may be induced during the procedure, the maximum temperature value detected in the area studied was recorded and considered for successive analysis. RESULTS: Infrared thermocamera measurements of the corneal surface during crosslinking treatment showed that the temperature was constant during the entire procedure and remains under the threshold of thermal injury to corneal collagen. CONCLUSION: Corneal collagen crosslinking was a safe procedure that did not cause thermal injury to the corneal surface.

Corneal endothelial damage after cataract surgery: Microincision versus standard technique.

PURPOSE: To compare corneal endothelial changes after phacoemulsification performed with a standard technique versus a bimanual microincision cataract surgery (MICS) technique. SETTING: University ophthalmology department. METHODS: Eighty patients scheduled for routine cataract surgery were randomized into 2 groups; 40 eyes had standard stop-and-chop phacoemulsification (standard group) and 40 eyes had stop-and-chop phacoemulsification with microincision surgery (MICS group). Central corneal endothelial cell counts, coefficient of variation in cell size, hexagonality, and pachymetry were assessed preoperatively and 1 and 3 months postoperatively. RESULTS: The mean preoperative cell count in the entire sample was 2245 cells/mm2 +/- 37 (SE). The mean decreased by 102 cells at 1 month (95% confidence interval [CI], -133 to -71; P < .001) and by 144 cells at 3 months (95% CI, -187 to -102; P < .001). The difference between the standard group and the MICS group was 25 cells at baseline (95% CI, -169 to 120 cells; P = .739), 19 cells at 1 month (95% CI, -163 to 126; P = .799), and 19 cells at 3 months (95% CI, -164 to 125; P = .793). There were no changes in the coefficient of variation or morphology in the overall sample, and the pattern of change did not differ between the 2 groups. Corneal thickness increased by 10.2 microm in the overall sample (95% CI, +4.5 to +16.0; P < .001) and approached baseline values by 3 months with an increase of 3.4 microm (95% CI, -4.1 to 10.8; P = .372). There was no difference in corneal thickness between the groups. CONCLUSION: No significant differences in corneal endothelial cell loss or endothelial morphology were found between MICS and standard incision techniques.

Scanning electron microscopic analysis of acrylic intraocular lenses for microincision cataract surgery.

PURPOSE: To analyze the surface quality before and after folding of 2 intraocular lens (IOL) models designed for microincision cataract surgery. SETTING: Eye Clinic and Department of Human Pathology and Oncology, University of Florence, Florence, Italy. METHODS: Two IOL models now available for sub-2.0 mm microincision were studied: UltraChoice 1.0 Rollable ThinLens (ultrathin lens by ThinOptX) and AcriSmart (foldable lens by AcriTec). Eight IOLs of each model were examined. Scanning electron microscopy (SEM) was performed before and after IOL folding with a dedicated injector. Special attention was given to the optic surface and edges, the optic-haptic junction, and the haptic itself. RESULTS: Initially, the surface quality of IOLs was evaluated before folding. On SEM, smooth and homogeneous optic and haptic surfaces were revealed in both IOL models with no surplus material or molding flashes; edge finish of all optics showed no evidence of ridges. The IOL surfaces were evaluated after insertion into their injectors and after ejection at room temperature. After folding, the microincision IOLs showed no sign of surface alteration, probably because of their high water content, which makes these IOLs soft and flexible. CONCLUSIONS: Visual results and long-term biocompatibility of the IOLs are influenced by surface properties. In recent years, there has been a trend toward microincision cataract surgery. Our study shows that the 2 IOL models now available for sub-2.0 mm microincision have acceptable surface properties.

Ultrasound thermal damage to rabbit corneas after simulated phacoemulsification.

PURPOSE: To determine rabbit cornea thermal tolerance and evaluate the effects of ultrasound (US) on this tissue after applying defined US heat doses. SETTING: Eye Clinic; Anatomy Histology and Forensic Medicine, University of Florence, Florence, Italy. METHODS: Hyperthermia was induced in rabbit corneas using US, simulating a phacoemulsification procedure. The US power was set at 100% in continuous mode, and temperature values were reached within 10 seconds of the onset of US treatment. Corneal surface temperatures were continuously monitored and recorded by thermographic registration. The eyes of 16 rabbits were examined: 4 controls, 8 treated at 40 degrees C for 10 seconds, 8 treated at 50 degrees C for 10 seconds, and 12 treated at 60 degrees C for 10 seconds. All 32 corneal buttons were removed and prepared for light microscopic evaluation with hematoxylin and eosin staining, trichromic staining, and zinc iodide-osmium tetroxide solution. The 12 corneas treated at 60 degrees C for 10 seconds were also processed for immunohistochemical analysis. RESULTS: Corneas at 40 degrees C for 10 seconds were grossly and histologically normal and were not different from control corneas. Corneas at 50 degrees C for 10 seconds showed initial stromal damage with collagen disorganization, mild stromal edema, and initial signs of keratocyte damage. Half of the corneas at 60 degrees C for 10 seconds were examined at time 0 and the other half after 1 week. At time 0, massive corneal damage with epithelial cell edema, collagen disorganization, severe stromal edema, intrastromal vacuole formation, plump keratocyte nuclei, and endothelial cell detachment were found, as was a severely impaired nerve plexus. At 1-week follow-up, corneas showed persistent stromal and endothelial cell edema with an increase activated keratocytes and mitotic features in the stroma and the epithelial layer. CONCLUSIONS: Rabbit corneas showed a considerable tolerance to US damage up to 50 degrees C. Higher thermal doses produced severe histological damage, even though corneas showed a considerable plasticity due to their regenerative capacity.