PURPOSE To assess the regression rate of conductive keratoplasty (CK) in patients with or without previous laser-assisted in situ keratomileusis (LASIK) or photorefractive keratectomy (PRK). SETTING University of Utah, Medical School, John A. Moran Eye Center, Salt Lake City, Utah. MATERIALS AND METHODS A retrospective, age-matched chart review identified records of 6 patients who underwent...

We show that manipulation and selection of optical patterns is possible by detuning the frequency of one of the two waves in counterpropagating photorefractive two-wave mixing with a feedback mirror. An analytical expression for the onset of modulational instability is derived for the general case of an arbitrary complex coupling constant, including a possible frequency shift of the generated s...

Holographic experiments are performed on a series of dual-use chromophore molecules wherein both irreversible photochromic and erasable photorefractive holographic gratings can be written in the same storage volume. At 675 nm, the chromophore undergoes a photochemical reaction leading to the creation of irreversible holographic gratings. Alternatively, at longer wavelengths, application of an e...

Photorefractive polymers have been extensively studied for over two decades and have found applications in holographic displays and optical image processing. The complexity of these materials arises from multiple charge contributions, for example, leading to the formation of competing photorefractive gratings. It has been recently shown that in a photorefractive polymer at relatively moderate a...

Commercial 1.55-microm extended-cavity semiconductor lasers provide single-mode operation that can be continuously tuned over a range larger than 100 nm without mode hopping. But such performance requires delicate factory adjustment and high mechanical stability of the external cavity. Furthermore, at high emission power the tuning range is limited to small values because of the annoying multim...

the past decade has witnessed the revival of amniotic membrane transplantation (amt) in ophthalmology. the importance of amt is due to its ability to reduce scarring and inflammation and to enhance wound healing and epithelialization, and also its anti-microbial properties. amniotic membrane has recently been used as a substrate for culturing limbal stem cells for transplantation. it has been u...

purpose : to evaluate the effect of topical diclofenac sodium 0.1% on the corneal epithelial healing after photorefractive keratectomy (prk) methods : in this prospective randomized double blind clinical trial, prk was performed on 82 patients. thirty-three cases of them receiving topical diclofenac four times per day after surgical procedure and 45 patients did not receive this medication as a...

We consider the convergence characteristics of a perceptron learning algorithm, taking into account the decay of photorefractive holograms during the process of interconnection weight changes. As a result of the hologram erasure, the convergence of the learning process is dependent on the exposure time during the weight changes. A mathematical proof of the conditional convergence, perceptrons, ...

We generate higher-order azimuthally modulated Bessel optical lattices in photorefractive crystals by employing a phase-imprinting technique. We report on the experimental observation of self-trapping and nonlinear localization of light in such segmented lattices in the form of ring-shaped and single-site states. The experimental results agree well with numerical simulations accounting for an a...