ABSTRACT

PURPOSE: To analyze the surface roughness of porcine corneas after excimer laser ablation with and without the smoothing procedure by means of atomic force microscopy. METHODS: Excimer laser photorefractive keratectomy (PRK) was performed on eight porcine corneas. Immediately following the procedure, smoothing was performed on four corneas using a viscous solution of 0.25% sodium hyaluronate. The corneas were examined in balanced salt solution after fixation in 2.5% glutaraldehyde solution using atomic force microscopy. Quantitative analysis of the ablated stromal surface topography was performed using the section analysis module of the atomic force microscopy software. Repeated measurements were made over small areas (^50 ?im2) near the center of each ablation, with a vertical resolution of <1 nm. RESULTS: Images of the ablated stromal surface showed undulations and granule-like features on the ablated surface of the specimens. The specimens on which the smoothing procedure was performed (rootmean-square [RMS] rough: 0.152 ?0.014 ???) were more regular (P<.001) than those on which PRK alone was performed (RMS rough: 0.229?0.018?im). CONCLUSIONS: Atomic force microscopy analysis requires a simpler preparation of the specimens with respect to that necessary for scanning electron microscopy; for this reason, atomic force microscopy techniques are more reliable for the study of biological surfaces and prove to be a feasible method to establish the differences when comparing different laser techniques. Our investigations highlight that although the laser cut of scanning-spot excimer laser systems is precise in removing even the smallest amounts of tissue, the smoothing technique may still be useful to reduce post-ablation roughness. [J Refract Surg. 2005;21:469-475.]

Refractive errors are some o f the most common ophthalmic abnormalities. The introduction o f excimer laser technology in refractive corneal surgery aims to eliminate a l l o r the major p a r t of the first corneal surface optical aberrations through the modelling o f the corneal surface. Among the main causes o f post-operative aberrations are the new corneal profile created by laser and the roughness o f the treated surface. I t is mandatory for a n optimal surgical outcome that the treated surface be as similar as possible to the natural architecture o f the cornea. The a i m of this study is to evaluate the corneal topography before and after the laser treatment by means o f A t o m i c Force Microscopy.Index Terms -Atomic force microscopy, biomedical materials, excimer lasers, laser biomedical applications, Surgery.

In this work, WO3 and TiO2 thin films have been obtained by the sol-gel spin coating method. The as-deposited samples were annealed at different annealing temperatures in the range between 100°C and 500°C. Micro-Raman spectroscopy confirmed that WO3 thin films annealed at 100°C and 300°C are amorphous while the crystallization process occurred at 500°C as established by the typical Raman modes of γ-WO3. Amorphous thin films of TiO2 have been obtained using annealing at 100°C and 300°C. The crystalline phase of the anatase-TiO2 has been obtained after the thermal treatment conducted at 500°C. The electrochromic devices were characterized by cyclic voltammetry and UV–Vis–NIR spectroscopy and it has been shown that the best configurations of the electrochromic devices studied in this work can be obtained by using the WO3 thin films amorphous, which means annealed at 100°C and 300°C, and TiO2 thin films crystalline, that is annealed at 500°C. The higher coloration efficiency values in the visible region (λ = 550 nm) and in the near-infrared region (λ = 1020 nm) support the idea that such devices could be used in order to control the light flux but also heat flux. It means that such electrochromic devices can be usefully employed as smart windows promoting energy and economic savings.

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