Despite the interest in developing improved formulas for intraocular lens power calculation, there are several sources of uncertainty that may well give rise to a significant residual refractive error. Those concerning the estimation of the corneal power are reviewed. In addition, we explore the possibility of introducing changes in some unconventional parameters of the eye to compensate for de...

BACKGROUND Microkeratomes are currently used for keratomiluesis in situ (automated lamellar keratoplasty) for myopia and hyperopia and for laser in situ keratomileusis (LASIK). Visual and refractive complications have been reported with these refractive surgical procedures. We compared two microkeratomes in their ability to resect corneal lamellae to gain insight into possible mechanism(s) of r...

PURPOSE To describe a new formula, BESSt, to estimate true corneal power after keratorefractive surgery in eyes requiring cataract surgery. SETTING Moorfields Eye Hospital, London, United Kingdom. METHODS The BESSt formula, based on the Gaussian optics formula, was developed using data from 143 eyes that had keratorefractive surgery. The formula takes into account anterior and posterior cor...

PURPOSE To investigate normal anterior segment parameters and analyze the possible influencing factors using a dual Scheimpflug system. SETTING Department of Ophthalmology, Affiliated Sixth People's Hospital Shanghai Jiao Tong University, Shanghai, China. DESIGN A prospective observational case series. METHODS A total of 153 normal subjects (153 eyes) were studied. The anterior segment pa...

PURPOSE To investigate the topography of the central and peripheral cornea in a group of young adult subjects with a range of normal refractive errors. METHODS Corneal topography data were acquired for 100 young adult subjects by a method that allows central and peripheral maps to be combined to produce one large, extended corneal topography map. This computer-based method involves matching t...

PURPOSE To evaluate the changes in corneal transparency and thickness measured objectively using Pentacam Scheimpflug (Oculus Optikgeräte GmbH) corneal tomography (densitometry) after corneal cross-linking (CXL). METHODS Twenty-two eyes from 15 patients with keratoconus underwent CXL. Corneal thickness and curvature as well as lens and corneal densitometry were measured at baseline and 1, 3, ...

To perform safe and successful corneal refractive surgery on myopic patients, corneal thickness (CT) and corneal epithelial thickness (CET) must be accurately measured. Numerous individuals with myopia wear soft contact lenses (SCLs) for the correction of visual acuity but may subsequently undergo corneal refractive surgery. The aim of the present study was therefore to investigate the effects ...

Our purpose is to correct digital CCD-recorded Scheimpflug photographs, imaging both the anterior and posterior corneal surface, the anterior chamber, and the anterior eye lens surface for optical distortions. In a ray-tracing algorithm the imaging of the posterior corneal surface in a given Scheimpflug photograph is corrected by applying Snell's law on parallel incident rays entering through t...

Photorefractive keratectomy (PRK) remodels corneal stroma to compensate refractive errors. The removal of epithelium and the ablation of stroma provoke the disruption of corneal nerves and a release of several peptides from tears, epithelium, stroma and nerves. A myriad of cytokines, growth factors, and matrix metalloproteases participate in the process of corneal wound healing. Their balance w...