This study aimed to characterize corneal accommodation in alert chicks with and without experimentally-induced astigmatism. Refraction and corneal biometry were measured in 16 chicks with experimentally-induced astigmatism (>1.00 D) and 6 age-matched control chicks (astigmatism ⩽ 1.00 D). Corneal accommodation was detected using a Placido-ring based videokeratography system, by measuring change...

This mini review focuses on the current knowledge on posterior corneal astigmatism based on the latest research. In the first part the definition, the magnitude as well as methods and devices for its evaluation are presented. Posterior corneal astigmatism measurement is improving as new technologies are evolving. It is now shown that the posterior corneal surface acts as a negative lens and as ...

The aim of this work was comparison of preoperative and postoperative astigmatism after superotemporal or superonasal clear corneal incision. Twenty eight eyes of 28 patients treated with phacoemulsification through superotemporal or superonasal 3 mm clear corneal incision were examined by kerato-refractometer preoperatively and six months postoperatively. Adequate score was assigned to each pr...

PURPOSE To demonstrate how higher-order corneal aberrations can cancel out, modify, or induce lower-order corneal astigmatism. PATIENTS AND METHODS Six representative eyes are presented that show different scenarios in which higher-order aberrations interacting with corneal astigmatism can affect the manifest refraction. WaveLight® Contoura ablation maps showing the higher-order aberrations a...

Purpose. To evaluate surgically induced astigmatism (SIA) and the average corneal power change in symmetric intrastromal corneal ring segment (ICRS) implantation. Methods. The study included 34 eyes of 34 keratoconus patients who underwent symmetric Intacs SK ICRS implantation. The corneal pocket incision meridian was the preoperative steep meridian. Corneal power data were obtained before and ...

PURPOSE To evaluate the factors that affect postoperative astigmatism and post-suture removal astigmatism, and to evaluate the risk factors associated with astigmatism axis shift. METHODS We performed a retrospective chart review of 130 eyes that had undergone uneventful phacoemulsification cataract surgery. Preoperative astigmatism was divided into four groups (Groups I, II, III, and IV) acc...

A successful corneal graft requires both clarity and an acceptable refraction. A clear corneal graft may be an optical failure if high astigmatism limits visual acuity. Intraoperative measures to reduce postkeratoplasty astigmatism include round and central trephination of cornea with an adequate size, appropriate sutures with evenly distributed tension, and perfect graft-host apposition. Sutur...

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 identify an optimal customized ablation strategy in the treatment of eyes with secondary irregular astigmatism. METHODS Corneal anterior surface elevation maps of 50 eyes with secondary irregular astigmatism after decentered laser in situ keratomileusis (LASIK) or photorefractive keratectomy (PRK) and 50 virgin eyes were used for customized ablation simulations. Two ablation simula...

OBJECTIVE To compare the corneal astigmatism before and after the excision of pterygium and also to determine the correlation of pterygium size with the postoperative corneal astigmatism. STUDY DESIGN Cross-sectional interventional study. PLACE AND DURATION OF STUDY Eye Department, Combined Military Hospital, Abbottabad, from May 2011 to March 2012. METHODOLOGY Thirty patients underwent p...