scholarly journals The impact of irregular corneal shape parameters on visual acuity and contrast sensitivity

2020 ◽  
Vol 20 (1) ◽  
Author(s):  
Sanita Liduma ◽  
Artis Luguzis ◽  
Gunta Krumina
Keyword(s):  
Visual Acuity ◽  
Contrast Sensitivity ◽  
Cross Sectional Study ◽  
Shape Parameters ◽  
Corneal Surface ◽  
Cross Sectional ◽  
Corneal Shape ◽  
Different Diameters ◽  
The Impact ◽  
Corneal Apex

Abstract Background To understand which irregular corneal parameters determine the visual quality in keratoconus subjects. Methods The cross-sectional study examined the eyes of 44 subjects, graded from the first to third keratoconus stages by Amsler-Krumeich classification. We obtained measurements in two ways: (a) by projecting two perpendicular axes onto a cornea (first, through the central point of the cornea and keratoconus apex; second, as the perpendicular axis) to read the elevation values at points on these axes as parameters characterising the corneal surface; (b) by projecting circles with different diameters around the central part of the cornea (1, 2, and 3 mm) and reading elevation values at points equally displaced on these circles as parameters characterising an anterior surface slope. Irregular corneal shape parameters’ correlations with visual acuity and contrast sensitivity were determined in order to understand which corneal slope parameter has the strongest correlation with visual acuity and contrast sensitivity. Results Parameters characterising the corneal surface’s correlations with contrast sensitivity were from r = 0.25 (p = 0.03) at 3 cpd to r = 0.47 (p < 0.01) at 9 cpd for the highest elevation and from r = 0.33 (p = 0.09) at 5 cpd to r = 0.40 (p < 0.01) at 11 cpd for the lowest elevation in all subjects together, while for visual acuity the parameters were r = 0.30 (p < 0.01) for the highest elevation and r = 0.21 (p = 0.06) for the lowest elevation in all subjects together. The correlation between contrast sensitivity and the highest and lowest corneal point in all measured cornea was stronger for subjects with a peripheral corneal apex than for those with a central apex. In keratoconus subjects, contrast sensitivity displayed a strong correlation with slope in the central part of the cornea (with a radius of 1 mm) ranging from 0.48 (p < 0.01) at 3 cpd to 0.61 (p < 0.01) at 9 cpd. Conclusion Contrast sensitivity has a higher correlation with corneal shape parameters than with visual acuity. Subjects with a peripheral corneal apex had stronger correlations with visual acuity and contrast sensitivity than did subjects with a central apex. In keratoconus subjects, the strongest correlation was for contrast sensitivity and elevation (slope) in the region within a 1 mm radius of the corneal centre in the opposite direction of the keratoconus apex (direction (ax) CB).

scholarly journals The Impact of Irregular Corneal Shape Parameters on Visual Acuity and Contrast Sensitivity

2020 ◽  
Author(s):  
Sanita Liduma ◽  
Artis Luguzis ◽  
Gunta Krumina
Keyword(s):  
Visual Acuity ◽  
Contrast Sensitivity ◽  
Cross Sectional Study ◽  
Shape Parameters ◽  
Corneal Surface ◽  
Cross Sectional ◽  
Corneal Shape ◽  
Different Diameters ◽  
The Impact ◽  
Corneal Apex

Abstract Background: To understand which irregular corneal parameters determine the visual quality in keratoconus subjects.Methods: The cross-sectional study examined the eyes of 44 subjects, graded from the first to third keratoconus stages by Amsler-Krumeich classification. We obtained measurements in two ways: (a) by projecting two perpendicular axes onto a cornea (first, through the central point of the cornea and keratoconus apex; second, as the perpendicular axis) to read the elevation values at points on these axes as parameters characterising the corneal surface; (b) by projecting circles with different diameters around the central part of the cornea (1, 2, and 3 mm) and reading elevation values at points equally displaced on these circles as parameters characterising an anterior surface slope. Irregular corneal shape parameters’ correlations with visual acuity and contrast sensitivity were determined in order to understand which corneal slope parameter has the strongest correlation with visual acuity and contrast sensitivity.Results: Parameters characterising the corneal surface’s correlations with contrast sensitivity were from r=0.25 (p=0.03) at 3 cpd to r=0.47 (p<0.01) at 9 cpd for the highest elevation and from r=0.33 (p=0.09) at 5 cpd to r=0.40 (p<0.01) at 11 cpd for the lowest elevation in all subjects together, while for visual acuity the parameters were r=0.30 (p<0.01) for the highest elevation and r=0.21 (p=0.06) for the lowest elevation in all subjects together. The correlation between contrast sensitivity and the highest and lowest corneal point in all measured cornea was stronger for subjects with a peripheral corneal apex than for those with a central apex. In keratoconus subjects, contrast sensitivity displayed a strong correlation with slope in the central part of the cornea (with a radius of 1 mm) ranging from 0.48 (p<0.01) at 3 cpd to 0.61 (p<0.01) at 9 cpd.Conclusion: Contrast sensitivity has a higher correlation with corneal shape parameters than with visual acuity. Subjects with a peripheral corneal apex had stronger correlations with visual acuity and contrast sensitivity than did subjects with a central apex. In keratoconus subjects, the strongest correlation was for contrast sensitivity and elevation (slope) in the region within a 1 mm radius of the corneal centre in the opposite direction of the keratoconus apex (direction (ax) CB).

scholarly journals The Impact of Irregular Corneal Shape Parameters on Visual Acuity and Contrast Sensitivity

2020 ◽  
Author(s):  
Sanita Liduma ◽  
Artis Luguzis ◽  
Gunta Krumina
Keyword(s):  
Visual Acuity ◽  
Contrast Sensitivity ◽  
Cross Sectional Study ◽  
Shape Parameters ◽  
Corneal Surface ◽  
Cross Sectional ◽  
Corneal Shape ◽  
Different Diameters ◽  
The Impact ◽  
Corneal Apex

Abstract Background: To understand which irregular corneal parameters determine the visual quality in keratoconus subjects. Methods: The cross-sectional study examined the eyes of 44 subjects, graded from the first to third keratoconus stages by Amsler-Krumeich classification. We obtained measurements in two ways: (a) by projecting two perpendicular axes onto a cornea (first, through the central point of the cornea and keratoconus apex; second, as the perpendicular axis) to read the elevation values at points on these axes as parameters characterising the corneal surface; (b) by projecting circles with different diameters around the central part of the cornea (1, 2, and 3 mm) and reading elevation values at points equally displaced on these circles as parameters characterising an anterior surface slope. Irregular corneal shape parameters’ correlations with visual acuity and contrast sensitivity were determined in order to understand which corneal slope parameter has the strongest correlation with visual acuity and contrast sensitivity.Results: .Parameters characterising the corneal surface’s correlations with contrast sensitivity were from r=0.25 (p=0.03) at 3 cpd to r=0.47 (p<0.01) at 9 cpd for the highest elevation and from r=0.33 (p=0.09) at 5 cpd to r=0.40 (p<0.01) at 11 cpd for the lowest elevation in all subjects together, while for visual acuity the parameters were r=0.30 (p<0.01) for the highest elevation and r=0.21 (p=0.06) for the lowest elevation in all subjects together. The correlation between contrast sensitivity and the highest and lowest corneal point in all measured cornea was stronger for subjects with a peripheral corneal apex than for those with a central apex. In keratoconus subjects, contrast sensitivity displayed a strong correlation with slope in the central part of the cornea (with a radius of 1 mm) ranging from 0.48 (p<0.01) at 3 cpd to 0.61 (p<0.01) at 9 cpd.Conclusion: Contrast sensitivity has a higher correlation with corneal shape parameters than with visual acuity. Subjects with a peripheral corneal apex had stronger correlations with visual acuity and contrast sensitivity than did subjects with a central apex. In keratoconus subjects, the strongest correlation was for contrast sensitivity and elevation (slope) in the region within a 1 mm radius of the corneal centre in the opposite direction of the keratoconus apex (direction (ax) CB).

scholarly journals The Impact of Irregular Corneal Shape Parameters on Visual Acuity and Contrast Sensitivity

2020 ◽  
Author(s):  
Sanita Liduma ◽  
Artis Luguzis ◽  
Gunta Krumina
Keyword(s):  
Visual Acuity ◽  
Contrast Sensitivity ◽  
Strong Correlation ◽  
Visual Quality ◽  
Main Axis ◽  
Shape Parameters ◽  
Visual Axis ◽  
Corneal Shape ◽  
The Impact ◽  
Corneal Apex

Abstract Background: To understand which irregular corneal parameters determine the visual quality in keratoconus subjects. Methods: The cross-sectional study examined thecovered eyes of 44 subjects, graded from the first to third keratoconus stages by Amsler-Krumeich classification. To characterize the shape of cornea, wWe obtained measurements in two ways: (a) by projectinged two perpendicular axes onto a cornea (– the main axis passed first, through the central point of the cornea (visual axis projection) and keratoconus apex; second, as , while the second axis was perpendicular to the main axis) to – and read the elevation values at points on theses axeis as parameters characterising the corneal surface; (b) by projectinged circles with different diameters around the central part of the cornea (1, 2, and 3 mm) and reading elevation values at points equally displaced on these circles as parameters characterising an anterior surface slope. Irregular corneal shape parameters’ correlations with visual acuity and contrast sensitivity were determined The measurements were used to calculate various elevation change (slope) parameters, in order to understand which corneal slope parameter has the strongest correlation with visual acuityquality and contrast sensitivity.Results: According to the acquired data, the visual acuity of a corrected eye does not have a strong correlation with the measured keratoconus apex slope. Parameters characterising the corneal surface’s correlations with contrast sensitivity were from r=0.25 (p=0.03) at 3 cpd to r=0.47 (p<0.01) at 9 cpd for the highest elevation and from r=0.33 (p=0.09) at 5 cpd to r=0.40 (p<0.01) at 11 cpd for the lowest elevation in all subjects together, while for visual acuity the parameters were r=0.30 (p<0.01) for the highest elevation and r=0.21 (p=0.06) for the lowest elevation in all subjects together. The correlation between contrast sensitivity and the highest and lowest corneal point in all measured cornea was stronger for subjects with a peripheral corneal apex than for those with a central apex. In keratoconus subjects, Ccontrast sensitivity displayed a strong correlation with keratoconus slope in the central part of the cornea (with a radius of 1 mm). Correlations in different spatial frequencies ranging from 0.48 (p<0.01) at 3 cpd to 0.61 (p<0.01) at 9 cpd.Conclusion: Contrast sensitivity has a higher correlation with corneal shape parameters than with is more important parameter which describes the visual quality of keratoconus subjects than visual acuity. Subjects with a peripheral corneal apex had stronger correlations with visual acuity and contrast sensitivity than did subjects with a central apex. In keratoconus subjects, Tthe strongest correlation was for contrast sensitivity and elevation (slope) in the region most important region which determines the visual quality in keratoconus subjects is the region within a 1 mm radius of the corneal centre in the opposite direction of the keratoconus apex (direction (ax) CB).

scholarly journals Percentage of Foveal versus Total Macular Geographic Atrophy as a Predictor of Visual Acuity in Age-related Macular Degeneration

2019 ◽  
Author(s):  
Saghar Bagheri ◽  
Ines Lains ◽  
Rebecca Silverman ◽  
Ivana Kim ◽  
Dean Eliott ◽  
...  
Keyword(s):  
Visual Acuity ◽  
Macular Degeneration ◽  
Fundus Autofluorescence ◽  
Cross Sectional Study ◽  
Geographic Atrophy ◽  
Age Related Macular Degeneration ◽  
Cross Sectional ◽  
Age Related ◽  
The Impact ◽  
Foveal Sparing

AbstractObjectivesTo investigate the relationship between visual acuity (VA), total area of geographic atrophy (GA) and percentage of foveal GA.MethodsMulticenter, retrospective cross-sectional study of patients with GA due to age-related macular degeneration. Demographics, VA, fundus autofluorescence (FAF) and optical coherence tomography (OCT) images were collected. Using FAF images aided by OCT, foveal sparing status, GA pattern, total GA size, and percentage of GA covering the foveal area - area within a 1.5 mm diameter circle centered on the fovea centralis - were assessed. Univariable and multiple linear regression analyses were performed.Results54 eyes (mean age 78.7 ±7.7 (SD), 60.0% female) were studied. Mean VA was 0.8 ± 0.6 logMAR, mean total GA 8.8 ± 6.7 mm2 and mean percentage of foveal GA was 71.5 ± 30.9%. Of all assessed eyes, 48.2% (n = 26) presented with multifocal GA, and 18.5% (n = 10) had foveal sparing. Multiple regression analysis revealed that, controlling for age and GA pattern, the percentage of foveal GA presented a statistically significant association with VA (ß = 0.41, P = 0.004). No significant associations were observed with mean total GA size, while controlling for the same variables (ß = 0.010, P = 0.440).ConclusionPercentage of foveal GA was significantly associated with VA impairment, while the same was not verified for total GA area. These findings suggest that percentage of foveal GA may represent a more useful tool for assessing the impact of GA on VA. Further validation is needed in larger cohorts.

Multifocal Corneal Ablation (Supracor) in Hyperopic Presbyopia: 1-Year Results in a Cross-Sectional Study

2016 ◽  
Vol 27 (4) ◽  
pp. 438-442 ◽  
Author(s):  
Torsten Schlote ◽  
Alexander Heuberger
Keyword(s):  
Visual Acuity ◽  
Patient Satisfaction ◽  
Side Effects ◽  
Contrast Sensitivity ◽  
Cross Sectional Study ◽  
Sectional Study ◽  
Cross Sectional ◽  
Distance Visual Acuity ◽  
One Year ◽  
Distance Vision

Purpose To evaluate the efficacy and safety of the multifocal excimer laser corneal ablation profile (the Supracor procedure) in hyperopic presbyopia 1 year after laser treatment. Methods This prospective, consecutive, one-center, cross-sectional study included 20 patients with hyperopic presbyopia 1 year after treatment with the Supracor procedure. The main outcome measures were monocular uncorrected distance visual acuity (UDVA) and uncorrected near visual acuity (UNVA), photopic contrast sensitivity (Pelli-Robson charts), patient satisfaction, and functioning at 12 months. Results Thirty-nine eyes of 20 patients (mean age 59 ± 7.2 years) were treated. Mean UDVA improved from 0.56 ± 0.31 (mean 0.34 logMAR) preoperatively to 0.9 ± 0.15 (mean 0.06 logMAR) 12 months after surgery. Mean UNVA increased from 0.15 ± 0.07 (mean 0.84 logMAR) before surgery to 0.62 ± 0.24 (mean 0.23 logMAR) 12 months after treatment. Four eyes lost 2 lines of corrected distance visual acuity (10.3%). Monocular photopic contrast sensitivity was within age-correlated normal range (Pelli-Robson chart, mean contrast sensitivity 1.83 ± 0.18). A total of 75% of the patients would undergo Supracor again (1 not, 4 perhaps). The most frequently reported side effects were increased glare, reduced distance vision, and fluctuations in vision. Most patients used artificial tears. Conclusions One year after Supracor, UDVA and UNVA improved markedly, photopic contrast sensitivity was in normal age-correlated range, and the majority of patients (75%) was satisfied with the results. Side effects like loss of distance vision, fluctuations of vision, and increased glare have a greater influence on patient satisfaction than the improvement of spectacle-free near vision.

scholarly journals Study on visual function comparison between ametropes and emmetropes after visual correction

2021 ◽  
Vol 7 (2) ◽  
pp. 428-432
Author(s):  
L K Lali ◽  
R Abirama Sundari ◽  
R Shankar
Keyword(s):  
Visual Acuity ◽  
Contrast Sensitivity ◽  
Refractive Error ◽  
Axial Length ◽  
Reading Speed ◽  
Cross Sectional Study ◽  
Cross Sectional ◽  
Visual Functions ◽  
Significant Difference

Studies had also shown that 86% of children with refractive error living in rural area are without correction as many are unaware of their problem. Refractive error by itself plays a significant role on one’s quality of life and literature had also proven it. To study the visual functions in ametropes with 6/6 BCVA and compare it with emmetropes.: A cross-sectional study was conducted for a period of one year. All the 200 subjects were tested for refractive error using auto refractor, distance and near visual acuity was assessed with the ETDRS chart, contrast sensitivity was assessed using LEA symbol chart, color vision was assessed using FM 15 online test and field vision was tested using Bjerrum tangent screen, stereopsis was examined using TNO cards, morphometric measurements was done by measuring the axial length using A scan and the K reading was obtained using auto keratometer and finally the functional assessment was analysed using the reading and writing speed. A total of 200 subjects with 100 ametropes and 100 emmetropes were included in our study. Colour vision, near point accommodation, near point convergence, axial length were significantly altered in ametropes. Contrast sensitivity, steropsis and reading speed were significantly reduced in ametropes compared to emmetropes. There was no significant difference in visual functions between different types refractive error subjects like myopia, hypermetropia and astigmatism. The present study proves that visual acuity alone is not an indicator for assessing the quality of vision instead the complete visual functions has to be screened on all patients reporting with refractive error.

scholarly journals Percentage of Foveal vs Total Macular Geographic Atrophy as a Predictor of Visual Acuity in Age-Related Macular Degeneration

2019 ◽  
Vol 3 (5) ◽  
pp. 278-282 ◽  
Author(s):  
Saghar Bagheri ◽  
Ines Lains ◽  
Rebecca F. Silverman ◽  
Ivana Kim ◽  
Dean Eliott ◽  
...  
Keyword(s):  
Visual Acuity ◽  
Macular Degeneration ◽  
Fundus Autofluorescence ◽  
Cross Sectional Study ◽  
Geographic Atrophy ◽  
Age Related Macular Degeneration ◽  
Cross Sectional ◽  
Age Related ◽  
The Impact ◽  
Sd Oct

Purpose: This article investigates the relationship between visual acuity (VA), total area of geographic atrophy (GA), and percentage of foveal GA. Methods: A multicenter, retrospective, cross-sectional study was conducted of patients with GA due to age-related macular degeneration. Demographics, VA, fundus autofluorescence (FAF), and spectral-domain optical coherence tomography (SD-OCT) images were collected. Using FAF images aided by SD-OCT, fovea-sparing status, GA pattern, total GA size, and percentage of GA covering the foveal area—within a 1.5-mm-diameter circle centered on the fovea centralis—were assessed. Univariable and multiple linear regression analyses were performed. Results: Fifty-four eyes (mean age, 78.7 ±7.7 years [SD], 60.0% female) were studied. Mean VA was 0.8 ± 0.6 logarithm of the minimum angle of resolution (Snellen equivalent 20/126 ± 20/80), mean total GA 8.8 ± 6.7 mm2, and mean percentage of foveal GA was 71.5 ± 30.9%. Of all assessed eyes, 48.2% (n = 26) presented with multifocal GA, and 18.5% (n = 10) had foveal sparing. Multiple regression analysis revealed that, controlling for age and GA pattern, the percentage of foveal GA presented a statistically significant association with VA (ß = 0.41, P = .004). No significant associations were observed with mean total GA size, while controlling for the same variables (ß = 0.010, P = .440). Conclusions: Percentage of foveal GA was significantly associated with VA impairment, although the same was not verified for total GA area. These findings suggest that percentage of foveal GA may represent a more useful tool for assessing the impact of GA on VA. Further validation is needed in larger cohorts.

scholarly journals Comparison of contrast sensitivity in myopic patients using spectacle and contact lens correction

2021 ◽  
Vol 15 (5) ◽  
pp. 951-953
Author(s):  
Sadaf Qayyum ◽  
Zubair Wahab ◽  
Rabia Saeed ◽  
Anbar Zulfiqar ◽  
Ayisha Shakeel ◽  
...  
Keyword(s):  
Visual Acuity ◽  
Contrast Sensitivity ◽  
Contact Lens ◽  
Contact Lenses ◽  
Cross Sectional Study ◽  
Cross Sectional ◽  
Spectacle Lens ◽  
Optical Correction ◽  
Eye Examination ◽  
Optical Defocus

Aim: To compare the contrast sensitivity in different categories of myopia using two different optical correction spectacles and contact lens correction. Methods: This cross-sectional study in design was conducted from August 2018 to May 2019 at the Ophthalmology Department of Madinah Teaching Hospital Faisalabad.45 subjects corrected with spectacles lenses and contact lenses all had corrected visual acuity of 6/9 or better were studied.The extent of myopia determined the three groups. All individuals were subjected to spectacles and Contact lens correction using slitlamp for anterior eye examination and for the fundus examination. The assessment of visual acuity was carried out by the Snellen vision Chart at 6m distance and contrastssensitivity was tested by Pelli- Robson chart. Results: Results showed a significant relationship between contrast sensitivity and type of optical correction. There were significant results of the independent t-test for spectacle and contact lenses 0.00 (p<0.005). However, the mean contrast sensitivity was better for all the three groupswith contact lens correction as compared to spectacle lens correction.Contact lenses provide better contrast sensitivity than spectacle lenses. Conclusion: Comparison between contact lens and spectacle correction was done and better quality contact lenses reduce optical defocus and give better results of contrast sensitivity. Results also concluded that loss of contrast sensitivity will be interpreted as early loss of retinal functions in severe myopes. Keywords: Myopia, Contrast sensitivity, Spectacle lens, Contact lens

scholarly journals Cross-sectional study assessing the addition of contrast sensitivity to visual acuity when testing for fitness to drive

BMJ Open ◽  
2018 ◽  
Vol 8 (1) ◽  
pp. e018546 ◽  
Author(s):  
Lucie Spreng ◽  
Bernard Favrat ◽  
François-Xavier Borruat ◽  
Paul Vaucher
Keyword(s):  
Visual Acuity ◽  
Contrast Sensitivity ◽  
Cross Sectional Study ◽  
Sectional Study ◽  
Fitness To Drive ◽  
Cross Sectional

scholarly journals The Impact of Irregular Corneal Shape Parameters on Visual Acuity and Contrast Sensitivity

2020 ◽  
Author(s):  
Sanita Liduma ◽  
Artis Luguzis ◽  
Gunta Krumina
Keyword(s):  
Visual Acuity ◽  
Contrast Sensitivity ◽  
Strong Correlation ◽  
Visual Quality ◽  
Optical Quality ◽  
Main Axis ◽  
Visual Axis ◽  
Spatial Frequencies ◽  
Corneal Shape ◽  
The Impact

Abstract Background: The image optical quality is affected by changes in corneal shape of patients with keratoconus. The goal of this study was to explore which corneal parameters determine the visual quality in keratoconus subjects, which corneal slope parameter has the strongest correlation with visual quality and contrast sensitivity. Methods: The study covered eyes of 77 subjects, graded from the first to third keratoconus stages. To characterize the shape of cornea, we obtained measurements in two ways: (a) projected two perpendicular axes onto a cornea – the main axis passed through the central point of the cornea (visual axis projection) and keratoconus apex, while the second axis was perpendicular to the main axis – and read elevation values at points on theses axis; (b) projected circles with different diameters around the central part of the cornea (1, 2 and 3 mm) and read elevation values at points equally displaced on these circles. The measurements were used to calculate various elevation change (slope) parameters. Results: According to the acquired data, the visual acuity of a corrected eye does not have a strong correlation with the measured keratoconus apex slope. Contrast sensitivity displayed a strong correlation with keratoconus slope in the central part of the cornea (with a radius of 1 mm). Correlations in different spatial frequencies ranging from 0.47 to 0.6. Conclusion: Contrast sensitivity is more important parameter which describes the visual quality of keratoconus subjects than visual acuity. The most important region which determines the visual quality in keratoconus subjects is the region with a 1 mm radius of the corneal centre in the opposite direction of keratoconus apex.

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