| 1. |
- Frisén, Lars, 1939, et al.
(författare)
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A simple relationship between the probability distribution of visual acuity and the density of retinal output channels.
- 1976
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Ingår i: Acta ophthalmologica. - 0001-639X. ; 54:4, s. 437-44
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Tidskriftsartikel (refereegranskat)abstract
- Throughout the retina, the parameters of the probability distribution of visual acuity for monochromatic interference fringes are closely proportional to the number of retinal ganglion cells per degree of visual angle. There are no simple relationships to receptor spatial frequencies. These findings suggest that neuro-retinal acuity is determined principally by the spatial frequency of neural output channels.
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| 2. |
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| 3. |
- Frisén, Lars, 1939, et al.
(författare)
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How good is normal visual acuity?. A study of letter acuity thresholds as a function of age.
- 1981
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Ingår i: Albrecht von Graefes Archiv fur klinische und experimentelle Ophthalmologie. Albrecht von Graefe's archive for clinical and experimental ophthalmology. - 0065-6100. ; 215:3, s. 149-57
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Tidskriftsartikel (refereegranskat)abstract
- Visual acuity levels were studied in 100 normal subjects of different ages, using a finely graduated letter chart under carefully optimized test conditions. Each line on the chart contained 10 letters of similar difficulty, arranged in random order. A statistical analysis of different response criteria showed a clear superiority of fractional criteria (e.g. 50% correct responses) over the traditional 100% correct requirement. The average difference between right and left eyes was 0.04 +/- 0.15 (decimal notation). Regression analysis of the dependence of visual acuity on age showed a monotonic rise towards the age of 25 years, and a gradual decline thereafter. The most marked decline occurred after the age of 60. Age-dependent confidence intervals were tabulated. The results indicate that minor modifications of the conventional test procedure can enhance the diagnostic potential considerably.
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| 4. |
- Frisén, Lars, 1939, et al.
(författare)
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Micropsia and visual acuity in macular edema. A study of the neuro-retinal basis of visual acuity.
- 1979
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Ingår i: Albrecht von Graefes Archiv fur klinische und experimentelle Ophthalmologie. Albrecht von Graefe's archive for clinical and experimental ophthalmology. - 0065-6100. ; 210:2, s. 69-77
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Tidskriftsartikel (refereegranskat)abstract
- Relative micropsia was measured by a matching technique in patients with unilateral, benign, macular edema. Quantitative assessment of foveolar micropsia to be a sensitive indicator of receptor displacement in this disorder, and may be a useful tool both for diagnosing and for monitoring macular edema. Parallel measurements of grating acuity showed a close proportionality between acuity and micropsia parameters. This result validates a new quantitative theory for the neuro-retinal basis of visual acuity. The theory allows prediction of the proportion of working visual neurons in patients with impaired acuity due to diseases that produce a diffuse loss, or disconnection, of macular cones. Our results indicate that so-called normal visual acuity (1.0 or 20/20) requires no more than 44% of the normal quantity of fovelar, neuro-retinal channels.
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| 5. |
- Frisén, Lars, 1939, et al.
(författare)
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Objective recognition of abnormal isopters.
- 1975
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Ingår i: Acta ophthalmologica. - 0001-639X. ; 53:3, s. 378-92
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Tidskriftsartikel (refereegranskat)abstract
- We have examined the hypothesis that normal and only normal isopters of the central visual field are elliptical, except for random deviations. Statistical methods capable of recognizing small deviations from elliptical shape have been developed. Theses methods have been devised to meet the special demands of clinical testing of visual fields and require only simple calculations. The qualities of these methods were examined by theoretical analysis, by large-scale simulations, and by experimental comparison with subjective evaluations. The new methods proved very useful in these examinations. A clinical study using a servo-equipped Goldman perimeter demonstrated that normal central isopters are elliptical enough for the proposed test characteristic to be of practical value in clinical work. The method allows an objective recognition of abnormal isopters with a high degree of sensitivity.
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| 6. |
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| 7. |
- Blomsterwall, Elisabeth, et al.
(författare)
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Postural function and subjective eye level in patients with idiopathic normal pressure hydrocephalus.
- 2011
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Ingår i: Journal of neurology. - : Springer Science and Business Media LLC. - 1432-1459 .- 0340-5354. ; 258:7, s. 1341-6
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Tidskriftsartikel (refereegranskat)abstract
- Disturbance of posture is a frequent indication of idiopathic normal pressure hydrocephalus (iNPH) and is characterised by an increased sway in the frontal and sagittal planes. Further, iNPH patients with increased backward sway are known to have a defective perception of the subjective visual vertical (SVV), with the upper portion of an articulated rod tilted towards themselves. The objective of the present study was to compare subjective eye level (SEL) with actual eye level (EL) and compare this data with SVV and postural function. Twenty iNPH patients and ten normal controls estimated SEL by placing an adjustable horizontal line at EL. Sway pattern and SVV were also examined as previously described. The patients presented larger errors on downward as compared to upward line adjustments; all patients also presented a SVV tilted towards them. The patients swayed more in the sagittal than in the frontal plane at a higher speed than the normal controls, and they were relatively less helped by their vision. This is in accordance with the tendency to fall backwards seen in many iNPH patients. iNPH patients have a tendency to place SEL higher than EL and this, together with examination of SVV and sway pattern, suggests defective internal processing of gravicentric information.
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| 8. |
- Frisén, Lars, 1939, et al.
(författare)
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A primer of ophthalmic computer graphics.
- 1990
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Ingår i: Documenta ophthalmologica. Advances in ophthalmology. - 0012-4486. ; 74:4, s. 337-50
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Tidskriftsartikel (refereegranskat)abstract
- Computer graphics offers an unprecedented opportunity to probe new and old ideas in vision testing, without going to the expense of building dedicated equipment. However, the large variety of computer hardware is bewildering and only occasionally can commercial software tools be used. This mini review of the basic principles of computer graphics on personal computers is intended to help the newcomer to the field.
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| 9. |
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| 10. |
- Frisén, Lars, 1939
(författare)
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Acuity perimetry: estimation of neural channels.
- 1988
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Ingår i: International ophthalmology. - 0165-5701. ; 12:3, s. 169-74
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Tidskriftsartikel (refereegranskat)abstract
- Measurements of peripheral visual acuity allow quantitative estimations of retino-cortical neural channels. Analysis of results from high-pass resolution perimetry revealed that about 2/3 of all channels are contained within 30 degrees of visual field eccentricity and that loss of 1/3 raises the average threshold level about 1 decibel. The analytical procedure can be applied to any type of visual field defect.
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