In this paper we generalize the class of explicit partitioned Runge-Kutta (PRK) methods for separable Hamiltonian systems to systems with holonomic constraints. For a convenient analysis of such schemes, we rst generalize the backward error analysis for systems in I R m to systems on manifolds embedded in I R m. By applying this analysis to constrained PRK methods, we prove that such methods wi...

BACKGROUND To study the effect of prophylactic application of mitomycin-C on haze formation in photorefractive keratectomy (PRK) for high myopia. METHODS Fifty-four eyes of 28 myopic patients were enrolled in this prospective study. All eyes were operated by PRK followed by 0.02% mitomycin-C application for two minutes and washed with 20 ml normal saline afterwards. All eyes were examined tho...

PURPOSE To compare the efficacy, predictability, safety, and induced higher-order aberrations (HOAs) between wavefront-guided and non-wavefront-guided photorefractive keratectomy (PRK). METHODS The Cochrane Central Register of Controlled Trials, PubMED, and EMBASE were searched for randomized controlled trials. Trials meeting the selection criteria were quality appraised, and data was extract...

Purpose: This study was planned to evaluate the efficacy, safety and complication of photorefractive keratectomy (PRK) as a retreatment of residual myopia after previous laser in situ keratomileusis (LASIK). Methods: In this descriptive study in ophthalmology ward, Feiz Hospital, Isfahan University of Medical Sciences, Iran, with the consideration of inclusion and exclusion criteria, 170 eyes o...

BACKGROUND Patients presenting for photorefractive keratectomy (PRK) may have unusual psychological profiles. Certain psychological variables may impact treatment outcome, making early identification crucial. We report a controlled questionnaire study of psychiatric "anxiety/distress" and self-esteem in myopic patients who presented for excimer laser treatment. METHODS Ninety consecutive myop...

THE EXCENTRIC ASTIGMATISM PRK, A PHOTOREFRACTIVE METHOD TO CORRECT CORNEAL ASTIGMATISM USING TEE 193-NM EXCIMERLASER HUETZ,W.W., EOFFMANN,P.C., ECKHARDTJ3.B. Pumore: The Excentric Astigmatism PRK is a method to correct comeal astigmatism with two peripheral ablations which are performed outside an untreated central zone. Method% Two peripheral ablations of 3.4 mm diameter are performed outside ...

PURPOSE The safety and efficacy of corneal collagen cross-linking (CXL) and topography-guided photorefractive keratectomy (PRK) using a different sequence and timing were evaluated in consecutive keratoconus cases. METHODS This study included a total of 325 eyes with keratoconus. Eyes were divided into two groups. The first group (n=127 eyes) underwent CXL with subsequent topography-guided PR...

THE EXCENTRIC ASTIGMATISM PRK, A PHOTOREFRACTIVE METHOD TO CORRECT CORNEAL ASTIGMATISM USING TEE 193-NM EXCIMERLASER HUETZ,W.W., EOFFMANN,P.C., ECKHARDTJ3.B. Pumore: The Excentric Astigmatism PRK is a method to correct comeal astigmatism with two peripheral ablations which are performed outside an untreated central zone. Method% Two peripheral ablations of 3.4 mm diameter are performed outside ...

AIM To determine the relation between epithelial hyperplasia and regression of effect after photorefractive keratectomy (PRK). METHODS Seventy unilaterally treated patients with PRK were examined. All eyes had been treated with the Summit excimer laser 27 (SD 7) months previously with zone diameters of 4.1 to 5.0 mm. The untreated fellow eyes served as controls. Epithelial thickness was measu...

To report the possibility of post myopic photorefractive keratectomy (PRK) haze treatment in a patient with expressed reluctance for any additional laser therapy. Seven months after bilateral PRK with subsequent development of corneal haze and refractive regression in both eyes, a 37-old-year male patient presented a best-spectacle corrected visual acuity (BSCVA) of 20/30 in the right eye and o...