PURPOSE To test and demonstrate measurement precision, imaging resolution, 3D thickness mapping, and clinical utility of a new prototype 3D very high-frequency (VHF) (50 MHz) digital ultrasound scanning system for corneal epithelium, flap, and residual stromal thickness after laser in situ keratomileusis (LASIK). METHODS VHF ultrasonic 3D data was acquired by arc-motion, meridional scanning w...

OBJECTIVE To compare the reproducibility of measurements obtained with a new pachymetry instrument, the Topcon specular microscope (Topcon SP-2000P; Topcon America Corp, Paramus, NJ), with those obtained by ultrasound pachymetry. METHODS Corneal thickness was measured in 40 eyes of 40 patients 3 times each with the Topcon SP-2000P and an ultrasound pachymeter (DGH 500, DGH Technology Inc, Ext...

BACKGROUND The purpose of this study was to evaluate the safety and efficacy of ultraviolet A irradiation cross-linking on completion for cases of high myopic laser-assisted in situ keratomileusis (LASIK). METHODS Forty-three consecutive LASIK cases treated with femtosecond laser flap and the WaveLight excimer platform were evaluated perioperatively for uncorrected visual acuity, best correct...

PURPOSE To record visual and refractive data in eyes with previous radial keratotomy (RK) and corneal instability undergoing corneal cross-linking (CXL). METHODS Case series of eyes with RK and refractive instability undergoing CXL with riboflavin and UV-A radiation. The following variables were recorded before 3 and 6 months after CXL: sphere, spherical equivalent (SE), uncorrected visual ac...

the porcine eye is often used as an ex vivo animal model in ophthalmological research. it is well-suited for investigations concerning refractive surgery; however, corneal topography data are scarce. this study investigated the corneal topography and pachymetry of the porcine eye to provide further reproducible data. we evaluated freshly enucleated porcine eyes (n = 16) by performing computeriz...

Measurement invariance (MI) is a pre-requisite for comparing latent variable scores across groups. The current paper introduces the concept of approximate MI building on the work of Muthén and Asparouhov and their application of Bayesian Structural Equation Modeling (BSEM) in the software Mplus. They showed that with BSEM exact zeros constraints can be replaced with approximate zeros to allow f...