Search results for "Optical"
showing 10 items of 7671 documents
Reproducibility and Daytime-Dependent Changes of Corneal Epithelial Thickness and Whole Corneal Thickness Measured With Fourier Domain Optical Cohere…
2016
To evaluate the reproducibility of Fourier domain anterior segment optical coherence tomography (RTVue) based on repeated measurements of corneal thickness (CT) and epithelial thickness (ET) and to test daytime-dependent changes of these parameters.Twenty-three eyes from 23 healthy volunteers were included in this prospective study. Three clinical observers performed 3 consecutive measurements each of CT and ET in 3 sessions using RTVue, resulting in 9 measurements per session. Session 1 was performed at 9 AM ± 1 hour, session 2 at 4 PM ± 1 hour on the same day, and session 3 at 9 AM ± 1 hour 2 days later. CT and ET were assessed in 9 areas: corneal vertex, 4 paracentral zones, and 4 periph…
The effect of aberrations on objectively assessed image quality and depth of focus
2017
The effects of aberrations on image quality and the objectively assessed depth of focus (DoF) were studied. Aberrometry data from 80 young subjects with a range of refractive errors was used for computing the visual Strehl ratio based on the optical transfer function (VSOTF), and then, through-focus simulations were performed in order to calculate the objective DoF (using two different relative thresholds of 50% and 80%; and two different pupil diameters) and the image quality (the peak VSOTF). Both lower order astigmatism and higher order aberration (HOA) terms up to the fifth radial order were considered. The results revealed that, of the HOAs, the comatic terms (third and fifth order) ex…
CORRELATION OF OPTICAL COHERENCE TOMOGRAPHY PATTERN AND VISUAL RECOVERY AFTER VITRECTOMY WITH SILICONE OIL FOR RETINAL DETACHMENT
2006
PURPOSE: To assess prospectively the features of the macular surface in silicone oil-filled eyes after surgery by analyzing whether silicone oil affects optical coherence tomography (OCT) measurements and their reproducibility and whether a statistical correlation exists between postoperative best-corrected visual acuity (BCVA) and foveal thickness measured by OCT. METHODS: Twenty eyes of 20 patients underwent vitrectomy with silicone oil tamponade for retinal detachment. After vitrectomy, complete ophthalmic examination including determination of BCVA and OCT was performed to quantify the visual recovery and the foveal thickness. RESULTS: Ophthalmoscopy revealed that the retina appeared to…
Association of Birth Weight With Foveolar Thickness in Adulthood: Results From a Population-Based Study
2021
Purpose Low birth weight (BW) is associated with alterations of foveal shape development in childhood—leading to an increased retinal thickness of the fovea. The aim of the present study was to assess whether BW has a long-term effect on foveal retinal thickness (RT) and is still present in adulthood. Methods In the German population-based Gutenberg Health Study (GHS), participants were examined with spectral-domain optical coherence tomography. The association between self-reported BW and RT in the foveolar and perifoveal locations was assessed. Multivariable linear regression analyses with adjustment for potential confounders and grading of foveal hypoplasia were performed. Results Overal…
Evaluation of the anterior chamber angle in keratoconus and normal subjects.
2015
To evaluate the anterior chamber angle in keratoconus eyes by use of the Visante™ OCT and Orbscan™ II.Anterior chamber angle was measured with the Visante™ OCT and Orbscan™ II in 52 subjects, 26 KC subjects and 26 age and control subjects.When comparing the nasal and temporal angles obtained with the two techniques no correlation was found (R(2) always below 0.01) in either the control subjects or in the KC subjects. Despite this, there was an overall statistically significant difference in mean anterior chamber angles (p0.001) between Visante™ OCT and Orbscan™ II. There was no statistical difference (p0.05) between nasal and temporal anterior chamber angles when comparing controls and KC s…
Comparison of Macular Thickness in Patients with Keratoconus and Control Subjects Using the Cirrus HD-OCT
2014
Purpose.The aim of the present study was to compare macular thickness in patients with keratoconus (KC) with macular thickness in healthy subjects.Subjects and Methods.Twenty-six patients with KC and 52 control subjects were included. The macular structure was evaluated using a Zeiss Cirrus HD-OCT. The scan pattern used was 512 × 128, which covers an area of approximately 6 × 6 mm of the retina. The cube volume was assessed as well as macular thickness in each of the 9 sectors defined by the software.Results.The mean signal strength was significantly lower in the KC group (mean 8.4, range 6–10) compared with the control group (mean 9.7, range 7–10),P<0.0001(unpairedt-test). There were no…
Visual illusions and the control of children arm movements.
2001
The aim of the present study was to determine whether children like adults (Gentilucci M, Chieffi S, Daprati E, Saetti MC, Toni I. Visual illusion and action. Neuropsychologia 1996;34:369-76; Gentilucci M, Daprati E, Gangitano M, Toni I. Eye position tunes the contribution of allocentric and egocentric information to target localisation in human goal directed arm movements. Neurosci Lett 1997;222:123-6) are influenced by visual illusions when they transform visual information in motor command. Children and adults pointed to a shaft extremity of the Müller-Lyer configurations, as well as to an extremity of a control configuration. Movements were executed in two experimental conditions. In th…
Effect of luminance on photopic visual acuity in the presence of laser speckle
1988
Visual acuity in coherent and incoherent light has been determined by using square-wave gratings of 100% contrast. Luminance was varied from 3 to 400 cd/m2. Coherent illumination resulted in a 40% loss of visual acuity. This is probably due to the masking effect of coherent spatial noise (speckle). However, the most interesting finding is the change in shape of the photopic visual-acuity-luminance function. With coherent illumination, the function is vertically displaced and of a different gradient. An increase in luminance produces a decrease in visual acuity. This indicates that the masking effect of the speckle is dependent on luminance. Two observers were used, and similar results were …
Optical coherence tomography of macular thickness after biaxial vs coaxial microincision clear corneal cataract surgery
2009
PURPOSE To evaluate macular thickness changes after biaxial microincision versus coaxial small incision cataract surgery using optical coherence tomography (OCT). METHODS This prospective, randomized, marked study comprised 70 patients (70 eyes) undergoing biaxial microincision surgery or conventional coaxial phacoemulsification. Patients were evaluated by Stratus OCT preoperatively and 1 day, 4 weeks, and 8 weeks postoperatively. Best-corrected visual acuity (BCVA), phacoemulsification power, and effective phacoemulsification time (EPT) were evaluated. RESULTS In the biaxial group, median foveal thickness changed from 160 microm preoperatively to 168 microm 8 weeks postoperatively (p=0.018…
Five-year functional outcomes and vault of -20 diopter myopic phakic intraocular lens implantation.
2015
Purpose To evaluate refractive and visual outcomes and complications associated with phakic intraocular lens (pIOL) implantation to correct high myopia. Settings Fernandez-Vega Ophthalmological Institute, Oviedo, Spain. Design Retrospective observational case series. Methods Uncorrected distance visual acuity (UDVA) and corrected distance visual acuity (CDVA), refraction, vault, and adverse effects were evaluated after 5 years with Visian ICMV4 pIOL. Results Mean spherical equivalent (SE) dropped from −18.32 ± 2.37 diopters (D) preoperatively to −0.88 ± 0.52D 5 years postoperatively; 61% of eyes were within ±0.75 D of the target. The mean Snellen decimal CDVA and UDVA were 0.73 ± 0.23 and 0…