Search results for "error"
showing 10 items of 1643 documents
An alternative clinical routine for subjective refraction based on power vectors with trial frames.
2016
PURPOSE Subjective refraction determines the final point of refractive error assessment in most clinical environments and its foundations have remained unchanged for decades. The purpose of this paper is to compare the results obtained when monocular subjective refraction is assessed in trial frames by a new clinical procedure based on a pure power vector interpretation with conventional clinical refraction procedures. METHODS An alternative clinical routine is described that uses power vector interpretation with implementation in trial frames. Refractive error is determined in terms of: (i) the spherical equivalent (M component), and (ii) a pair of Jackson Crossed Cylinder lenses oriented …
Peripapillary Choroidal Thickness and Choroidal Area in Glaucoma, Ocular Hypertension and Healthy Subjects by SD-OCT.
2015
Background: The exact pathogenesis of open angle glaucoma and ocular hypertension remains unclear. Hemodynamic influences are discussed as potential risk factors and the choroid may play an important role in the pathogenesis of open angle glaucoma or ocular hypertension. The current study investigates peripapillary choroidal thickness and choroidal area in patients with open angle glaucoma, subjects with ocular hypertension and healthy subjects using spectral-domain OCT. It furthermore assesses the association between peripapillary choroidal thickness and age, central corneal thickness, refractive error and intraocular pressure. Patients and Methods: Prospectively recorded data of 213 eyes …
Postoperative astigmatism and rotational stability after Artisan toric phakic intraocular lens implantation
2003
Abstract Purpose To evaluate deviations in the axis (intended versus achieved) and postoperative astigmatism after implantation of an Artisan toric phakic intraocular lens (IOL). Setting University Eye Hospital, Mainz, Germany. Methods This prospective study comprised 29 eyes with high ametropia and astigmatism. All eyes had uneventful implantation of a toric phakic IOL through a superior scleral tunnel incision at 12 o’clock. After a minimum of 6 months, the uncorrected visual acuity (UCVA), best correct visual acuity, refraction, and astigmatism were analyzed in all eyes. A multivariate analysis of postoperative astigmatism was performed. Results After a follow-up of at least 6 months, 95…
Influence of Refraction on Tonometric Readings After Photorefractive Keratectomy and Laser Assisted In Situ Keratomileusis
2000
PURPOSE To determine the decrease of Goldmann tonometry after photorefractive keratectomy (PRK) and laser assisted in situ keratomileusis (LASIK) according to refraction prior to surgery. METHODS Prospective simultaneous comparative case series of 53 myopic eyes (53 patients) that underwent PRK and 50 (50 patients) that underwent LASIK using the Summit Excimed SVS plus (Summit Technology, Inc., Walthan, MA, U.S.A.). PRK and LASIK were subdivided by refractive error into two subgroups of more than or less than -5 diopters (D). Central tonometric readings were taken prior to surgery and 12 months after surgery. RESULTS In LASIK and PRK subgroups of more than -5 D, 85.7% (24) and 69.6% (24), r…
Rate of Cataract Formation in 343 Highly Myopic Eyes After Implantation of Three Types of Phakic Intraocular Lenses
2004
ABSTRACT PURPOSE: To assess the feasibility of using phakic intraocular lenses (PIOL) to treat high myopia, and evaluate the incidence of cataract, comparing three different lens types. METHODS: From 1989 to 2002, we implanted three different phakic intraocular lenses (PIOL) in 343 eyes of 232 patients; 231 eyes recieved an Ophtec (Worst-Fechner model, iris-claw), 89 an Adatomed (silicone posterior chamber), and 23 a Staar (posterior chamber, models V2, V3, V4). Average follow-up was 96.2 months for the Ophtec group, 31.5 months for the Adatomed group, and 19.3 months for Staar group. Eyes that subsequently developed cataract were studied for clinical evolution and had PIOL explantation and…
Photodynamic therapy with verteporfin for subfoveal choroidal neovascularization secondary to pathologic myopia: long-term study.
2006
Purpose: To assess the safety and effectiveness of photodynamic therapy (PDT) with verteporfin for subfoveal choroidal neovascularization (CNV) secondary to pathologic myopia (PM). Methods: Sixty-two patients (62 eyes) with PM underwent PDT according to the guidelines of the Verteporfin in Photodynamic Therapy Study. Clinical evaluations performed at all study visits included measurement of best-corrected Snellen visual acuity, slit-lamp biomicroscopy, and fundus fluorescein angiography. Patients were followed up at 1 month and 3 months after treatment and thereafter at 3-month intervals. Results: The final visual acuity of the study patients, after a median follow-up of 31 months, improved…
Reproducibility of digital image analysis for measuring corneal haze after myopic photorefractive keratectomy.
1997
Purpose To evaluate the usefulness of digital image analysis for quantifying corneal haze by determining the reproducibility of its measurements at the corneal plane. Methods In a prospective study, 20 randomly selected eyes that had undergone myopic photorefractive keratectomy were photographed focusing the slit beam on their anterior corneal surface. Each photograph was examined using computer image analysis techniques that detect the edge of the reticular pattern of the image. Quantification of the difference between two areas, treated and adjacent untreated cornea, each containing 3,750 pixels with a resolution of 256 gray levels, was performed. Intra-analyzer variation was determined b…
Direct Objective Quantification of Corneal Haze after Excimer Laser Photorefractive Keratectomy for High Myopia
1996
Purpose: The purpose of the study is to measure regional distribution differences in corneal haze after excimer laser photorefractive keratectomy for high myopia. Methods: The authors developed computerized gradient edge detectors with which were analyzed digitized anterior slit-lamp photographs of 40 eyes, an average of 21.0 plus or minus 14.5 weeks after photorefractive keratectomy for high myopia (−6 to −22 diopters). A treated area and an adjacent untreated area on the anterior corneal surface, each containing six regions, were quantified, and the difference was correlated with various parameters. Results: Mean differences between scarred and clear areas for haze grade 0.5, 1.0, 2.0, 3.…
Phakic intraocular lenses to correct high myopia
2003
Abstract Purpose: To evaluate the feasibility and safety of using phakic intraocular lenses (IOLs) to correct high myopia by comparing 3 IOL models: Adatomed, Staar, and Artisan. Setting: La Fe University Hospital, Department of Ophthalmology, and the Fundacion Oftalmologica del Mediterraneo, Valencia, Spain. Methods: In this prospective comparative study, a phakic IOL was implanted in 217 highly myopic eyes (118 patients). Fifty-nine eyes received an Adatomed IOL, 21 eyes a Staar IOL, and 137 eyes an Artisan IOL. The mean preoperative spherical equivalent was −15.39 diopters (D) ± 2.83 (SD), −16.00 ± 5.05 D, and −16.17 ± 2.75 D in the Adatomed, Staar, and Artisan groups, respectively. The …
Mesopic contrast sensitivity function after excimer laser photorefractive keratectomy.
2002
ABSTRACT PURPOSE: To evaluate contrast sensitivity under mesopic conditions in patients who had undergone uncomplicated excimer laser photorefractive keratectomy (PRK) for myopia. METHODS: Monocular contrast sensitivity function was measured with the Stereo Optical ?A.C.T. chart in 26 patients who had received PRK using the Nidek EC-5000 excimer laser system. Mean preoperative refractive error was -6.23 ? 1.69 D (range, -4.00 to -8.25 D); postoperatively, mean refractive error was -0.36 ? 0.58 D (range, -0.75 to +0.50 D). Contrast sensitivity function was measured 6 months after surgery using four different chart luminances: 85, 5.0, 2.5, and 0.1 cd/m2, the first being a photopic level and …