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...

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...

PURPOSE The aim of this study was to determine the agreement between Pentacam HR (Scheimpflug imaging, Oculus) and Orbscan II (scanning slit topography, Bausch and Lomb) in measuring corneal parameters after photorefractive keratectomy (PRK) for hyperopia. METHODS In this prospective cross-sectional study, 38 hyperopic eyes undergoing PRK were examined before refractive surgery and 8 to 10 mo...

AIM To assess superficial lamellar keratectomy augmented by excimer laser smoothening with sodium hyaluronate 0.25%, for the management of superficial corneal opacities. METHODS Consecutive procedure performed in 14 eyes (13 patients) with an automated microkeratome and excimer laser phototherapeutic keratectomy (PTK) smoothening using sodium hyaluronate 0.25%. MAIN OUTCOME MEASURES UCVA, B...

PURPOSE To evaluate the anatomic and functional results of optical pachymetry-guided custom excimer laser-assisted lamellar keratoplasty in keratoconus patients. SETTING Eye Clinic, University of L'Aquila, L'Aquila, Italy. DESIGN Prospective noncomparative case series. METHODS Patients with keratoconus having unilateral surgery using custom excimer laser-assisted lamellar keratoplasty wer...

AIM We conducted this study to evaluate and compare corneal endothelial cell loss between phacoemulsification with continuous anterior chamber infusion using anterior chamber maintainer (ACM) and phacoemulsification using ophthalmic viscosurgical device (OVD). MATERIALS AND METHODS This was a prospective, randomized controlled trial. Fifty eyes of 47 patients of senile cataract undergoing pha...

PURPOSE To compare central corneal thickness measurements made using two different methods, optical coherence tomography (OCT) and ultrasound pachymetry, applied both in normal eyes and in eyes on which photorefractive keratectomy (PRK) had been performed. A second objective was to assess the intrasession variability of OCT measurements. METHODS In this prospective study, central corneal thic...

Background: This study aimed to investigate the diagnostic value of pachymetry parameters measured by RTVueOCT for keratoconus. Methods: 74 patients with 118 eyes diagnosed with keratoconus were enrolled in keratoconus group and 60 patients with normal 120 eyes as health controls. Pachymetry parameters were measured. The major indicators were tested: 1) S-I value: difference between the mean su...