Correction of corneal astigmatism is a key element of cataract surgery, since post-surgical residual astigmatism can compromise the patient's uncorrected visual acuity. Toric intraocular lenses (IOLs) compensate for corneal astigmatism at the time of surgery, correcting ocular astigmatism. They are a predictable treatment. However, accurate measurement of corneal astigmatism is mandatory for ch...

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...

PURPOSE To analyze the effect of birth weight on ocular morphology, refraction and visual function in early adolescents aged 12-15 years. MATERIAL AND METHODS We conducted a secondary data analysis using the public use files from the National Health and Nutrition Examination Survey of the period from 1999 to 2008. Study participants aged 12 to 15 years were included with data on birth weight ...

PURPOSE To determine whether Hartmann-Shack wavefront sensing detects differences in optical performance in vivo between poly(methyl methacrylate) (PMMA) and foldable acrylic intraocular lenses (IOLs) and between clear corneal and scleral tunnel incisions and whether optical differences are manifested as differences in visual performance. SETTING Department of Optometry, University of Bradfor...

Purpose To analyze the errors associated to corneal power calculation using the keratometric approach in keratoconus eyes after accelerated corneal collagen crosslinking (CXL) surgery and to obtain a model for the estimation of an adjusted corneal refractive index (nkadj ) minimizing such errors. Methods Potential differences (ΔPc) among keratometric (Pk ) and Gaussian corneal power (PcGauss)...

in this paper first we try to analysis the behavior ofthe soas in the optical networks and then have proposed anumerical simple model to simulate the behavior of thesemiconductor optical amplifiers. after that by employing thismodel as inline amplifier for a dwdm optical system, we havesimulated the transmission of 10 channels with bit rate 10 gb/sup to distance 3970 km with rz-dpsk modulation ...

The aim of this study was to examine whether mesenchymal stem cells (MSCs) and/or corneal limbal epithelial stem cells (LSCs) influence restoration of an antioxidant protective mechanism in the corneal epithelium and renewal of corneal optical properties changed after alkali burns. The injured rabbit corneas (with 0.25 N NaOH) were untreated or treated with nanofiber scaffolds free of stem cell...

PURPOSE To determine the theoretical relationships between the changes in corneal paraxial power, asphericity, and the corresponding Zernike polynomial expansion after conventional and customized excimer laser correction of hyperopia. METHODS The initial corneal profile was modeled as a conic section of apical radius of curvature R1 and asphericity Q1. The theoretical value of the postoperati...

Description of Procedure or Service Optical coherence tomography (OCT) is a high resolution method of imaging the ocular structures. OCT for the anterior eye segment is being evaluated as a non-invasive diagnostic and screening tool for the detection of angle closure glaucoma, to assess corneal thickness and opacity, evaluate pre-surgical and postsurgical anterior chamber anatomy, calculate int...

spatial distribution of electric field amplitude has an essential role in laser-induced damagemulti-layer coating. a new method introduced in this paper to reduce the electric field intensityeffectively within the high index layers in multi-layer reflectors that are irradiated by high power lasers.the design is based on specific non-quarter wave pairs, assuming the number of layers is held cons...