Purpose: To evaluate anterior surface topographic technologies and display algorithms in mapping keratoconus. Materials and methods: A total of 27 eyes of 17 subjects clinically diagnosed with keratoconus were imaged on six topographers: EyeSys, Alcon EyeMap, Keratron, TMS-1, Orbscan and PAR corneal topography system. Axial distance (AD) and instantaneous radius of curvature (IROC) algorithms w...

AIMS This study examined the occurrence, magnitude, and the consequences of a possible tilt between the corneal surface and optical axis of the EyeSys videokeratoscope. METHODS Initially, a theoretical model was developed to calculate the angle of tilt. The predictions of the model were verified empirically using a convex conicoid surface and were found to predict the tilt to within 0.5 degre...

PURPOSE The main goal of this study was to develop and compare two different techniques for classification of specific types of corneal shapes when Zernike coefficients are used as inputs. A feed-forward artificial Neural Network (NN) and discriminant analysis (DA) techniques were used. METHODS The inputs both for the NN and DA were the first 15 standard Zernike coefficients for 80 previously...

OBJECTIVE Corneal topography and thickness has clinical importance in contact lens fitting and refractive surgery, however repeated measurement of corneal thickness and curvature is complicated by the natural phenomenon of diurnal variation. Our aim was determine diurnal variations of central and paracentral corneal thickness and curvature over a period of ten hours. MATERIALS AND METHODS Cor...

AIM To determine the induced corneal astigmatism by measuring the changes in manual keratometry and computerised corneal videokeratoscopy up to 1 year following small flap trabeculectomy (microtrabeculectomy). METHOD A prospective study of a case series of small flap trabeculectomy procedures performed at the 90 degree meridian on 16 eyes of 16 patients, all followed to 1 year postoperatively...

AIM To assess the safety and predictability of photorefractive keratotomy (PRK) and laser in situ keratomileusis (LASIK) based on preoperative corneal topography. METHODS A non-randomised comparative study was carried out on 84 eyes that presented with topographic abnormalities before undergoing PRK (n = 44) or LASIK (n = 40) procedures. 84 spherical equivalent paired normal eyes served as th...

BACKGROUND A new commercially available device (IOLMaster, Zeiss Instruments) provides high resolution non-contact measurements of axial length (using partial coherent interferometry), anterior chamber depth, and corneal radius (using image analysis). The study evaluates the validity and repeatability of these measurements and compares the findings with those obtained from instrumentation curre...

PURPOSE To evaluate and compare corneal topographic changes following pars plana vitrectomy with the 23-gauge (G) and 25-G transconjuntival sutureless vitrectomy system as well as the standard 20-G vitrectomy system. METHODS We prospectively evaluated corneal topographic changes in 45 eyes of 45 patients divided into three groups according to vitrectomy system used (20-, 23-, and 25-G). All p...

Background: A new commercially available device (IOLMaster, Zeiss Instruments) provides high resolution non-contact measurements of axial length (using partial coherent interferometry), anterior chamber depth, and corneal radius (using image analysis). The study evaluates the validity and repeatability of these measurements and compares the findings with those obtained from instrumentation curr...