OBJECTIVES To evaluate the characteristics of the cornea in myopic patients. MATERIAL AND METHOD A retrospective study of 420 eyes in 210 patients who visited the Excimer Laser Surgery Clinic at Siriraj Hospital, Mahidol University from January 1999 to June 2002 was conducted. All cases that were eligible for myopic refractive surgery were included in the present study. A preoperative ocular ...

Determining the pupil center is fundamental for calculating eye orientation in video-based systems. Existing techniques are error prone and not robust because eyelids, eyelashes, corneal reflections or shadows in many instances occlude the pupil. We have developed a new algorithm which utilizes curvature characteristics of the pupil boundary to eliminate these artifacts. Pupil center is compute...

BACKGROUND The aim of this study was to determine the correlation between corneal hysteresis (CH) and the corneal resistance factor (CRF), which are both novel methods of analyzing ocular rigidity/elasticity, and various corneal characteristics, mainly corneal volume in normal subjects. METHODS This cross-sectional study included 500 normal eyes of volunteers. An ocular response analyzer (ORA...

BACKGROUND To examine the corneal epithelial phenotype in an altered basement membrane. METHODOLOGY/PRINCIPAL FINDINGS Corneas from 9 patients with symptoms of continuous unstable corneal curvature (CUCC) were harvested by penetrating keratoplasty and subjected to histology examination and immunohistochemical staining with transactivating and N-terminally truncated pP63 transcript (ΔNp63), cy...

In the article “Topographic Analysis of the Centration of the Treatment Zone After SMILE for Myopia and Comparison to FS-LASIK: Subjective Versus Objective Alignment” by Lazaridis et al.,1 a corneal thickness difference map was used to determine centration. The authors concluded that “the corneal thickness differential map in Scheimpflug-based systems is a useful tool to display the treatment z...

Most techniques measuring corneal biomechanics in vivo are biased by side factors. We demonstrate the ability of optical coherence tomographic (OCT) vibrography to determine corneal material parameters, while reducing current prevalent restrictions of other techniques (such as intraocular pressure (IOP) and thickness dependency). Modal analysis was performed in a finite-element (FE) model to st...

PURPOSE Refraction in the peripheral visual field is believed to play an important role in the development of myopia. The purpose of this study was to investigate the differences in peripheral refraction among anisomyopia, isomyopia, and isoemmetropia for schoolchildren. METHODS Thirty-eight anisomyopic children were recruited and divided into two groups: (1) both eyes were myopic (anisomyopi...

1.1 Definition Astigmatism (from the Greek “a” meaning absence and “stigma” meaning point) is a refractive error (ametropia) that occurs when parallel rays of light entering the nonaccommoding eye are not focused on the retina [American Academy of Ophthalmology (AAO), 2007]. Astigmatism occurs when incident light rays do not converge at a single focal point. The cornea of the normal eye has a u...

PURPOSE To examine the differences in the biomechanical response of the peripheral regions of the cornea after photorefractive keratectomy (PRK). SETTING Department of Ophthalmology, Catholic University of Rome, Rome, Italy. METHODS Preoperative and 1-, 3-, 6-, and 12-month postoperative corneal topographies of 70 eyes that had PRK with the Technolas 217C excimer laser (Bausch & Lomb) were ...

BACKGROUND To investigate the association between pretreatment corneal parameters and orthokeratology lens decentration. METHODS This retrospective study included a total of 108 eyes in 60 myopia patients, who were divided into a lens-decentration and a control group. Various pretreatment corneal parameters were analyzed by receiver operating characteristic curves (ROC curves), including corn...