To evaluate the changes in correlations of higher order aberrations first corneal surface with halo phenomena, a form image degradation, under night vision conditions measured objectively after successful LASIK (laser situ keratomileusis) surgery.A prospective, observational, analytical study 110 eyes that had undergone surgery for myopia and astigmatism. Preoperative sphere was (mean (SD)) -3.48 (1.70) D (0 to -8.00 D) preoperative cylinder -0.86 (0.87) -4.00 D). Visual disturbance caused...

Purpose: To analyze the origin of changes in corneal asphericity (p-factor) after laser situ keratomileusis (LASIK) and effect postsurgery on contrast-sensitivity function (CSF) under photopic conditions. Setting: Department Optics, University Granada, Spain. Methods: The p-factor CSF (best corrected before surgery 1, 3, 6 months surgery) were measured 24 eyes. Results: An increase LASIK was noted; there an 87.2% change using paraxial formula Munnerlyn coauthors. Other factors such as...

In this paper, we provide an analytic expression for adjustment factor in ablation algorithms photorefractive laser surgery which take into account reflection losses and the nonnormal incidence on cornea. We evaluate influence of certain ocular parameters, calculating alterations radius anterior cornea corneal asphericity when use algorithm given by Munnerlyn’s paraxial formula. Our data indicate that should be considered are currently being proposed customized need great accuracy correction...

ABSTRACT PURPOSE: To analyze binocular visual function after LASIK. METHODS: Eye aberrometry and corneal topography was obtained for both eyes in 68 patients (136 eyes). evaluate performance, monocular contrast sensitivity disturbance index quantifying halos were measured. Tests performed under mesopic conditions. RESULTS: Binocular summation diminished significantly (P<.0001) LASIK with increasing interocular differences eye aberrations. deterioration greater than index. CONCLUSIONS:...

Purpose. To analyze the influence of higher-order aberrations on binocular visual performance under mesopic conditions. Methods. We measured in both eyes 35 emmetropic observers with a Wasca aberrometer. Binocular was checked summation for contrast sensitivity function and parameter that characterizes stereopsis (maximum disparity). Results. maximum disparity significantly decrease increasing interocular differences (total, coma, spherical aberration). Conclusions. At least some aspects are...

We develop a new visual test, designed as software for quantifying discrimination capacity under low-illumination conditions. This is an important task in the presence of disturbances, such those perceived by subjects with some ocular pathologies. For this purpose, we propose visual-disturbance index, checking test two groups observers having different pathologies: group unilateral keratitis and another affected age-related macular degeneration (ARMD). To compare results to objective data,...

To determine whether the eye's optical quality is correlated to visual discrimination capacity of patients treated with LASIK using two different ablation algorithms.Visual was evaluated by disturbance index under low illumination (Halo v1.0 software, Laboratory Vision Sciences and Applications) in groups who underwent algorithms Allegretto Wave Eye-Q 400 Hz laser (WaveLight AG). In first group (standard group; 30 eyes), corneal ablations were performed standard algorithm (preoperative...

Abstract To calibrate a CRT color monitor, several assumptions are often made about its performance, one of the most accepted being constanel channel chromaticity. However, when measurements taken in extended field screen, where it is assumed that only primary phosphor excited, relative spectral radiance other phosphors contained also contributes, if background luminance not zero. This contribution greater at low levels RGB stimulation and would invalidate results obtained with calibration...

ABSTRACT PURPOSE: To determine the exact theoretical asphericity after refractive surgery when parabolic approximation of Munnerlyn formula is utilized. METHOD: From a least-square analysis and considering conicoid model for anterior cornea, we calculated final (p '-factor) from preoperative radii before surgery. RESULTS: The p-factor given by p'=p(R'3/R3); R radius curvature; radius; p p'-factor. CONCLUSIONS: This equation postoperative may be useful in studying influence on different...

To evaluate the optical image quality, using 2 devices (an aberrometer and a double-pass device), visual performance [contrast sensitivity function (CSF)] in patients with keratitis after resolution of disease.Twenty subjects (18 unilateral bilateral keratitis) were included this study. We also took measurements healthy fellow eyes for comparison. Ten studied before keratitis. Objective data gathered by aberrometry (ocular higher order, spherical, coma aberrations) Strehl ratio, parameter...

Purpose: Corneal and total higher order eye aberrations their effects on visual function were compared in two groups subjected to different emmetropization techniques—refractive surgery (LASIK) corneal refractive therapy (CRT). Methods: Twenty eyes of 11 patients 22 13 examined the CRT LASIK groups, respectively. Mesopic contrast sensitivity (CSF) was studied monocularly binocularly undergoing who had approximately same mean error. asphericity calculated, differences analyzed between groups....

To analyze the theoretical effect that pupil size, optical zone, and initial myopic level have on final retinal image after corneal refractive surgery.A schematic eye model corrected by Munnerlyn formula was used to quality of image. Root-mean-square radius spot modulation transfer function were cal- culated ray tracing evaluate quality.Pupil size had a negative only when it greater than diameter zone. In addition, level, more affected quality. Thus, clear dependence exists between can laser...

Cannabis is the most widely used illegal drug in world. Limited information about effects of cannabis on visual function available, and more detail possible impact car driving required. This study investigated smoking vision performance, whether these are correlated. Twenty drivers occasional users were included (mean (SE) age, 23.3 (1.0) years; five women). Vision simulated performance evaluated a baseline session after cannabis. Under influence cannabis, certain functions such as acuity (p...

Cannabis is one of the most used drugs abuse in world. The objective this study was to analyze effects smoking cannabis on vision and relate these those perceived by user. Thirty-one users participated study. Visual function assessment carried out a baseline session as well after cannabis. We evaluated static visual acuity, contrast sensitivity, stereoacuity, accommodative response, straylight, night-vision disturbances (halos) pupil size. participants were also divided into two groups...

We tested the effects on laser ablation of reflection losses and nonnormal incidence anterior cornea. measured presurgical postsurgical corneal asphericity in 94 myopic eyes, comparing it with predicted by Munnerlyn formula, modified or not, an adjustment factor that takes into account two mentioned above. The predictive power experimental results was stronger when we considered factor. propose to modify algorithms taking this account, especially customized ablation, which needs high...

The <i>Journal of Biomedical Optics</i> (JBO) is a Gold Open Access journal that publishes peer-reviewed papers on the use novel optical systems and techniques for improved health care biomedical research.

To study the effect on binocular contrast sensitivity and summation of aniseikonia induced by size (afocal) lenses.In 18 young emmetropic observers, monocular function was measured under normal conditions after inducing different degrees (2%, 3%, 5% for 6 8%) in right eye. The spatial frequencies tested were 2.4, 3.7, 6.0, 9.2, 12, 15, 20, 24 cpd.The results reveal a significant decline aniseikonia, this being more pronounced intermediate high frequencies.These results, together with others...

We deduce a mathematical equation for corneal asphericity after refractive surgery when the Munnerlyn formula is used. For this, an analytical least-squares procedure The explains discrepancies found by different authors or its paraxial approximation Equations deduced here may be of clinical relevance, example, in studying quantitatively role factors (decentration, type laser, optical flap, wound healing, biomechanical effects, technical procedures) during ablation.

Abstract The aim of this work is to determine the influence interocular differences in retinal image quality on binocular visual performance. We measured contrast sensitivity function (both monocular and binocular) we computed summation. Data were taken from a double‐pass device ( oqas™, Optical Quality Analysis System; Visiometrics SL. Tarrasa, Spain), providing Strehl ratio as parameter quantify quality. A total 28 observers took part experiments. Binocular summation for was found be...

In this work, we evaluate the impact of induced aniseikonia on stereopsis. For this, determined disparity range (maximum disparity), a parameter related to size physical region that can be perceived stereoscopically. A significant decline in was detected with by lenses 3% for five seven observers tested; 5% necessary other two observers. The data indicate influence stereopsis and need minimize such impact. These results may useful surgical processes as correction pseudophakic patients...

We calculate whether deviations of Lambert-Beer's law, which regulates depth ablation during corneal ablation, significantly influence refractive parameters after surgery and they visual performance.For this, we compute a point-to-point correction on the cornea while assuming non-linear (including quadratic term) fit for ablation.Post-surgical equations using show significant differences with respect to obtained from linear (Lambert-Beer's law).Differences were also aberrations.These results...

We evaluate the effect of emmetropization technique LASIK (laser-assisted in situ keratomileusis) on stereoscopic vision. For this, we used a mirror stereoscope to measure upper disparity limit D(max) before (with best correction) and after for 30 patients. The results show that declines from 41.1 min arc average 31.3 LASIK, being significant 83% This deterioration is significantly correlated with an increase postsurgical interocular differences higher-order aberrations, corneal asphericity,...

Purpose The aim of this work is to evaluate the epidemiological aspects refractive errors in school-aged children Malabo (Island Bioko), Equatorial Guinea (western-central Africa). Methods A total 425 schoolchildren (209 male subjects and 216 female subjects, aged between 6 16 years) were examined their refraction Malabo, examination included autorefraction with cycloplegia, measurement visual acuity (VA) for far vision, curvature radii main meridians anterior surface cornea. Results low...