scholarly journals Short-Term Changes in Light Distortion in Orthokeratology Subjects

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
Elena Santolaria Sanz ◽  
Alejandro Cerviño ◽  
Antonio Queiros ◽  
Cesar Villa-Collar ◽  
Daniela Lopes-Ferreira ◽  
...  
Keyword(s):  
Contrast Sensitivity ◽  
Optical Quality ◽  
Sensitivity Function ◽  
Spherical Equivalent ◽  
Short Term ◽  
High Frequencies ◽  
Corneal Aberrations ◽  
Quality Degradation ◽  
Spatial Frequencies ◽  
Distortion Parameters

Purpose. Quantifying adaptation to light distortion of subjects undergoing orthokeratology (OK) for myopia during the first month of treatment.Methods. Twenty-nine healthy volunteers (age: 22.34 ± 8.08 years) with mean spherical equivalent refractive error −2.10 ± 0.93D were evaluated at baseline and days 1, 7, 15, and 30 of OK treatment. Light distortion was determined using an experimental prototype. Corneal aberrations were derived from corneal topography for different pupil sizes. Contrast sensitivity function (CSF) was analyzed for frequencies of 1.50, 2.12, 3.00, 4.24, 6.00, 8.49, 12.00, 16.97, and 24.00 cpd under photopic conditions.Results. Average monocular values of all light distortion parameters measured increased significantly on day 1, returning to baseline after 1 week (P<0.05in all cases). Spherical-like aberration stabilized on day 7 for all pupil diameters, while coma-like for smaller pupils only. CSF was significantly reduced on day 1 for all spatial frequencies except for 1.5 cpd, returning to baseline afterwards. Significant correlation was found between light distortion and contrast sensitivity for middle and high frequencies (P<0.05) after 15 days.Conclusion. Despite consistently increased levels of corneal aberrations, light distortion tends to return to baseline after one week of treatment, suggesting that neural adaptation is capable of overcoming optical quality degradation.

scholarly journals Influence of Lenslet Configuration on Short-Term Visual Performance in Myopia Control Spectacle Lenses

2021 ◽  
Vol 15 ◽  
Author(s):  
Xue Li ◽  
Chenglu Ding ◽  
Yuhao Li ◽  
Ee Woon Lim ◽  
Yi Gao ◽  
...  
Keyword(s):  
Contrast Sensitivity ◽  
Random Order ◽  
Optical Quality ◽  
Visual Performance ◽  
Modulation Transfer ◽  
Short Term ◽  
Spatial Frequencies ◽  
Full Correction ◽  
The Right ◽  
Myopia Control

Purpose: This study aimed to evaluate short-term visual performance and optical quality of three different lenslet configurations on myopia control spectacle lenses.Materials and Methods: This study utilized a cross-over design. Distance visual acuity (VA) was measured in 50 myopic children; contrast sensitivity (CS) was measured in 36 myopic children. For each test, four spectacle lenses were evaluated in a random order: single-vision lens (SVL), lens with concentric rings of highly aspherical lenslets (HAL), lens with concentric rings of slightly aspherical lenslets (SAL), and lens with honeycomb configuration of spherical lenslets (HC). The modulation transfer function (MTF) and MTF area (MTFa) were used to determine optical quality. All tests were performed monocularly on the right eye with full correction.Results: HAL and SAL had larger MTFa than HC. VA in lenses with lenslets was significantly reduced compared to SVL (all p &lt; 0.01). The reduction in VA was worse with HC than with SAL (p = 0.02) and HAL (p = 0.03); no effect of lenslet asphericity was found (p &gt; 0.05). VA changes induced by lenslets showed no correlation with spherical equivalent refraction (all p &gt; 0.05) and were weakly positively associated with age for SAL (r = 0.36, p = 0.01) and HC (r = 0.31, p = 0.03), but not for HAL (p = 0.30). The area under the log contrast sensitivity function (AULCSF) decreased with HAL and HC (all p &lt; 0.001) in all illumination levels, and AULCSF with HAL was higher than that with HC in a photopic condition (1.17 ± 0.10 vs. 1.10 ± 0.13, p = 0.0004). The presence of lenslets did not affect CS at 3 cycles per degree (cpd) (p = 0.80). At 6 to 18 cpd, CS was significantly reduced by HAL and HC (all p &lt; 0.05), but not SAL (p &gt; 0.05) compared to SVL. At high spatial frequencies (&gt;12 cpd) both SAL and HAL reduced CS significantly less than HC (all p &lt; 0.01).Conclusion: Short-term visual performance was minimally impaired by looking through the lenslet structure of myopia control spectacle lenses. Concentric rings with aspherical lenslets had a significantly lower impact on both VA and CS than honeycomb configuration with spherical lenslets.

scholarly journals Corneal Aberrations, Contrast Sensitivity, and Light Distortion in Orthokeratology Patients: 1-Year Results

2016 ◽  
Vol 2016 ◽  
pp. 1-8 ◽  
Author(s):  
Elena Santolaria-Sanz ◽  
Alejandro Cerviño ◽  
José. M. González-Méijome
Keyword(s):  
Spatial Frequency ◽  
Contrast Sensitivity ◽  
Pupil Size ◽  
Healthy Subjects ◽  
Sensitivity Function ◽  
Spherical Equivalent ◽  
Optical Aberrations ◽  
Corneal Aberrations

Purpose.To evaluate the corneal higher-order aberrations (HOA), contrast sensitivity function (CSF), and light distortion (LD) in patients undergoing orthokeratology (OK).Methods.Twenty healthy subjects (mean age:21.40±8years) with mean spherical equivalent refractive errorM=-2.19±0.97 D were evaluated at 1 day, 1 month, and 1 year after starting OK treatment. Monocular LD, photopic monocular CSF, and corneal HOA for 6 mm pupil size were measured.Results.LD showed an increase after the first night (p<0.05) and recovery to baseline after 1 month, remaining stable after 1 year (p>0.05). Spherical-like, coma-like, and secondary astigmatism HOA RMS increased significantly (p≤0.022) from baseline to 1-month visit, remaining unchanged over the follow-up. Contrast sensitivity for medium frequencies (3.0, 4.24, and 6.00 cpd) was significantly correlated with LD parameters at baseline (r≤-0.529,p<0.001). However, after 1 year of treatment, this correlation was only statistically significant for 12 cpd spatial frequency (r≤-0.565,p<0.001). Spherical-like RMS for 6 mm pupil size correlated with irregularity of the LD (r=-0.420,p<0.05) at the 1-year visit.Conclusion.LD experienced by OK patients recovers after one month of treatment and remains stable in the long term while optical aberrations remain significantly higher than baseline.

scholarly journals Photopic and Mesopic Contrast Sensitivity Function in the Presence of Glare and the Effect of Filters in Young Healthy Adults

2021 ◽  
Vol 12 ◽  
Author(s):  
Alberto Domínguez-Vicent ◽  
Emma Helghe ◽  
Marika Wahlberg Ramsay ◽  
Abinaya Priya Venkataraman
Keyword(s):  
Contrast Sensitivity ◽  
Light Transmission ◽  
Luminance Contrast ◽  
Sensitivity Function ◽  
Contrast Sensitivity Function ◽  
Selective Absorption ◽  
Light Reduction ◽  
Spatial Frequencies ◽  
Significant Difference ◽  
Young Subjects

Purpose: The aim of this study was to evaluate the effect of four different filters on contrast sensitivity under photopic and mesopic conditions with and without glare.Methods: A forced choice algorithm in a Bayesian psychophysical procedure was utilized to evaluate the spatial luminance contrast sensitivity. Five different spatial frequencies were evaluated: 1.5, 3, 6, 12, and 18 cycles per degree (cpd). The measurements were performed under 4 settings: photopic and mesopic luminance with glare and no glare. Two long pass filters (LED light reduction and 511nm filter) and two selective absorption filters (ML41 and emerald filter) and a no filter condition were evaluated. The measurements were performed in 9 young subjects with healthy eyes.Results: For the no filter condition, there was no difference between glare and no glare settings for the photopic contrast sensitivity measurements whereas in the mesopic setting, glare reduced the contrast sensitivity significantly at all spatial frequencies. There was no statistically significant difference between contrast sensitivity measurements obtained with different filters under both photopic conditions and the mesopic glare condition. In the mesopic no glare condition, the contrast sensitivity at 6 cpd with 511, ML41 and emerald filters was significantly reduced compared to no filter condition (p = 0.045, 0.045, and 0.071, respectively). Similarly, with these filters the area under the contrast sensitivity function in the mesopic no glare condition was also reduced. A significant positive correlation was seen between the filter light transmission and the average AULCSF in the mesopic non-glare condition.Conclusion: The contrast sensitivity measured with the filters was not significantly different than the no filter condition in photopic glare and no glare setting as well as in mesopic glare setting. In mesopic setting with no glare, filters reduced contrast sensitivity.

Masking Effects Induced by Perceptual Colour Components

Perception ◽  
1997 ◽  
Vol 26 (1_suppl) ◽  
pp. 85-85
Author(s):  
L Bedat ◽  
A Saadane ◽  
D Barba
Keyword(s):  
Contrast Sensitivity ◽  
Image Coding ◽  
Sine Wave ◽  
Sensitivity Function ◽  
Contrast Sensitivity Function ◽  
Masking Effect ◽  
Perception Threshold ◽  
Colour Image ◽  
Spatial Frequencies ◽  
Achromatic Contrast

Signals from the three types of cone photoreceptors are generally thought to be combined into two opponent-colour components and an achromatic component. Here we have chosen the cardinal directions Ach (achromatic axis), Cr1 (reddish - greenish axis) and Cr2 (bluish - yellowish axis) defined by Krauskopf to build a colour image coding scheme based on features of the human visual system. In order to design the optimal perceptual quantisers, we studied the perception of colour at different spatial frequencies, measuring the effect of a colour masking signal on the perception threshold for achromatic or chromatic sine-wave gratings. Three cases were considered to describe these interactions. First, we measured the masking effect of each colour component by itself. For the two chromatic components, we observed a pedestal effect for low masking contrasts and threshold rises for higher masking contrasts. Second, we studied interactions between the two colour axes. With colour masking signals composed of Cr1 and Cr2 components, thresholds for Cr1 stimuli dropped at low contrasts of the Cr2 component of the masking signal. This effect disappeared for high Cr2 masking contrasts. This was true at all contrasts of the Cr1 component of the masking signal. Thresholds for Cr2 stimuli were not modified by Cr1 masking. Finally, interactions between the chromatic and achromatic components were more complex. We observed a strong modification of the achromatic contrast-sensitivity function when a Cr1 masking sine-wave grating was added. When the achromatic frequency was lower than the colour masking frequency, the threshold rose. However, when the achromatic frequency was higher than the colour masking frequency, there was a significant pedestal effect. The global effect is a shift of the achromatic contrast sensitivity function. With a Cr2 masking signal, no significant modification of the achromatic contrast-sensitivity function was observed.

scholarly journals Contrast Sensitivity Function of the Albino Rat Determined Electrophysiologically

1998 ◽  
Vol 1 ◽  
pp. 11-17 ◽  
Author(s):  
Pilar Herreros de Tejada ◽  
Carmen Muñoz Tedó
Keyword(s):  
Visual Acuity ◽  
Contrast Sensitivity ◽  
Sensitivity Function ◽  
Contrast Sensitivity Function ◽  
Albino Rats ◽  
Lower Sensitivity ◽  
Experimental Conditions ◽  
Albino Rat ◽  
Spatial Frequencies ◽  
Luminance Threshold

Albinism alters the neural projections of the visual system. The authors wondered how this would affect visual function in rodents. They had previously shown that it doesn't alter the luminance threshold. They now explore visual acuity in the albino rat. In this work, they describe its contrast sensitivity function (CSF), as determined electro-physiologically. They recorded cortical visual evoked potentials (VEP) on six albino rats, stimulated by sinusoidal contrast reversal gratings. The curve showed the same characteristics that this function has in other mammals. Compared with the pigmented rat, the albino reached lower sensitivity values and showed a loss of sensitivity at high spatial frequencies. The estimated cut-off was 0.48 c/°, that is, 0.72 log units below the estimated cut-off for the pigmented rat under similar experimental conditions. VEP and behavioral cut-off were very close, the VEP estimation being slightly higher than the behavioral one.

scholarly journals Improvement in Contrast Sensitivity Function after Lacrimal Passage Intubation in Eyes with Epiphora

2020 ◽  
Vol 9 (9) ◽  
pp. 2761
Author(s):  
Sujin Hoshi ◽  
Kuniharu Tasaki ◽  
Takahiro Hiraoka ◽  
Tetsuro Oshika
Keyword(s):  
Contrast Sensitivity ◽  
Anterior Segment ◽  
Case Series ◽  
Sensitivity Function ◽  
Contrast Sensitivity Function ◽  
Corrected Visual Acuity ◽  
Spatial Frequencies ◽  
Before And After ◽  
Tear Meniscus ◽  
Prospective Case Series

This prospective case series aimed to investigate the contrast sensitivity function before and after lacrimal passage intubation (LPI) in eyes with epiphora due to lacrimal passage obstruction. We included 58 eyes of 51 patients who underwent LPI for lacrimal passage obstruction. The best-corrected visual acuity (BCVA), contrast sensitivity function, and lower tear meniscus were compared before LPI and one month after lacrimal duct stent removal. The area under the log contrast sensitivity function (AULCSF) was calculated for the analyses. Lower tear meniscus was assessed using anterior segment optical coherence tomography. The BCVA was comparable (p = 0.61) before and after LPI, while AULCSF increased significantly after treatment (before LPI: 1.29 ± 0.17, after LPI: 1.37 ± 0.14, p < 0.0001). Treatment resulted in a significant increase in contrast sensitivity at all spatial frequencies, 3–18 cycles/degree (p < 0.01 for 3, p < 0.01 for 6, p < 0.0005 for 12, p < 0.05 for 18 cycles/degree). The lower tear meniscus parameters improved significantly after treatment (p < 0.005); however, no correlation between the changes in the tear meniscus and those of the AULCSF was found. The contrast sensitivity significantly improved after LPI in eyes with epiphora due to lacrimal passage obstruction.

scholarly journals Effect of Photorefractive Keratectomy and Laser in situ Keratomileusis in High Myopia on logMAR Visual Acuity and Contrast Sensitivity

2003 ◽  
Vol 46 (1) ◽  
pp. 15-18 ◽  
Author(s):  
Hana Langrová ◽  
Matthias Derse ◽  
Dagmar Hejcmanová ◽  
Alena Feuermannová ◽  
Pavel Rozsíval ◽  
...  
Keyword(s):  
Visual Acuity ◽  
Contrast Sensitivity ◽  
High Myopia ◽  
Laser In Situ Keratomileusis ◽  
Photorefractive Keratectomy ◽  
Spherical Equivalent ◽  
Spatial Frequencies ◽  
Quality Of Vision

Purpose: To compare effect of photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) on contrast sensitivity (CS) and best corrected visual acuity (BCVA) in high myopia. Methods: 38 myopes (PRK) and 31 patients (LASIK) were examined before and 1, 3, 6, and 12 months postoperatively. Mean preoperative spherical equivalent was -8.0 ± 1.7D (PRK) and -9.2 ± 2.1D (LASIK). CS was tested on a computerized system of the Contrast Sensitivity 8010 Type at 6 spatial frequencies (0.74 and 29.55 c/deg), BCVA was measured on logMAR charts. Results: At 12 months postoperatively, mean spherical equivalent was -0.6 ± 1.0D (PRK) and -1.0 ± 0.8D (LASIK). Postoperative values of CS were significantly higher in the PRK group, except for spatial frequencies of 3.69 and 7.39 c/deg up to 3 months postoperatively. The initial significant decrease of BCVA lasted up to 6 months after PRK. In the LASIK group BCVA was not significantly different from its preoperative level at the 3-months follow-up. Conclusions: The significant improvement of CS after PRK suggest that PRK can improve quality of vision in eyes with high myopia. Although recovery of BCVA after LASIK was faster than after PRK, there may be a persistent decrease in CS.

scholarly journals Contrast sensitivity before and after small incision lenticule extraction and femtosecond laser in situ keratomileusis

2019 ◽  
Vol 16 (4) ◽  
pp. 284-292
Author(s):  
Asik Pradhan ◽  
Kishore Raj Pradhan ◽  
Gauri Shankar Shrestha ◽  
Purushottam Dhunganga ◽  
Raju Kaiti
Keyword(s):  
Spatial Frequency ◽  
Contrast Sensitivity ◽  
Refractive Surgery ◽  
Sensitivity Function ◽  
Contrast Sensitivity Function ◽  
Laser In Situ Keratomileusis ◽  
Small Incision Lenticule Extraction ◽  
Spatial Frequencies ◽  
Lenticule Extraction

Introduction: Contrast sensitivity function after laser ablation of the cornea in refractive surgery is an important tool for measuring quality of visual function. The effect of small incision lenticule extraction (SMILE) and femtosecond laser in situ keratomileusis (FS-LASIK) on visual function can be compared by measuring spatial contrast sensitivity. Purpose: This study was to compare contrast sensitivity function in patients undergoing refractive surgery for myopia at Tilganga Institute of Ophthalmology. Methods: In a retrospective study, 15 subjects who underwent refractive surgeries comprising 9 cases of SMILE and 6 cases of FS-LASIK at Tilganga Eye Hospital were enrolled in the study. A major assessment included best corrected monocular contrast sensitivity with functional vision analyzer at spatial frequencies of 1.5, 3, 6, 12, and 18 cycles/deg in photopic condition (85 cd/m2) before, 3 months, and 1 year after the surgery. The average functional acuity contrast test scores for each spatial frequency were recorded. Differences between preoperative and postoperative contrast sensitivity at each spatial frequency were analyzed through parametric paired Student’s t-test. Results: Contrast sensitivity of postoperative FS-LASIK and SMILE did not differ from preoperative values at a photopic level. However, at high spatial frequency (12 and 18 cycles/deg), contrast sensitivity function improved significantly (p < 0.05) in eyes after FS-LASIK. Eyes after SMILE surgery did not show any reduction in contrast sensitivity at all the spatial frequencies. Conclusion: Under photopic conditions, the contrast sensitivity function is unaffected by SMILE or FS-LASIK.

scholarly journals Visual Outcomes and Higher Order Aberrations Following LASIK on Eyes with Low Myopia and Astigmatism

2018 ◽  
Vol 12 (1) ◽  
pp. 84-93 ◽  
Author(s):  
Smita Agarwal ◽  
Erin Thornell ◽  
Chris Hodge ◽  
Gerard Sutton ◽  
Paul Hughes
Keyword(s):  
Visual Acuity ◽  
Contrast Sensitivity ◽  
Spherical Aberration ◽  
Higher Order ◽  
Higher Order Aberrations ◽  
Corneal Aberrations ◽  
Spatial Frequencies ◽  
Quality Of Vision ◽  
Recent Developments

Background: Laser-Assisted in situ Keratomileusis (LASIK) can induce corneal aberrations that can impact vision and patient satisfaction. Recent developments in laser technologies have helped minimise these aberrations. Objective: To assess the quality of vision and change in Higher-Order Aberrations (HOAs) following wavefront-optimized LASIK in low-myopic astigmatic patients. Methods: LASIK was performed on a total of 76 eyes in patients with myopia <4.0 D and cylinder <2.0 D using the WaveLight® EX500 excimer and FS200 femtosecond laser platform. Visual acuity, contrast sensitivity and HOAs were measured at 1 and 3 months postoperatively and compared to preoperative values. Subjective quality of vision was assessed pre- and postoperatively using a VF14 questionnaire. Results: Mean postoperative Spherical Equivalent (SE) was -0.09 ± 0.26 µm with 95% of patients within ± 0.5 D of attempted SE. Postoperative uncorrected distance visual acuity was 20/20 or better for 96% of patients. Contrast sensitivity increased against horizontal and vertical gratings at all spatial frequencies except for vertical gratings at 18 cycles/degree. Spherical aberration and total HOA increased by 0.085 µm and 0.13 µm respectively. The mean VF14 score increased from 89.2 ± 16.7% to 99 ± 1.4% postoperatively. Conclusion: LASIK performed using the WaveLight® EX500 excimer and WaveLight® FS200 laser platform provided improved contrast sensitivity and visual acuity with minimal introduction of HOAs, making it a suitable platform for low myopic astigmatic patients.

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