| 1. |
- Frisén, Lars, 1939
(author)
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Acuity perimetry: estimation of neural channels.
- 1988
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In: International ophthalmology. - 0165-5701. ; 12:3, s. 169-74
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Journal article (peer-reviewed)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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| 2. |
- Frisén, Lars, 1939, et al.
(author)
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Binocular summation in humans: evidence for a hierarchic model.
- 1988
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In: The Journal of physiology. - 0022-3751. ; 402, s. 773-82
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Journal article (peer-reviewed)abstract
- 1. Binocular summation was studied in human subjects using a batter of vision tests. Two tests assessed detection, another three acuity, one hyperacuity and one pattern recognition. 2. The magnitude of summation was consistent with, or exceeded, the level predicted from quadratic summation for both detection tests. 3. The summation factor was significantly smaller in the resolution tests than in the detection tests. Hyperacuity showed a large individual variation. 4. Spatial filtering of acuity targets did not influence summation. 5. No summation was found in the pattern recognition test. 6. It is argued that the degree of summation is related to the complexity of the visual task. A simple task yields a larger binocular summation than a more complex one. This may be related to the level of processing in the primary visual cortex.
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| 3. |
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| 4. |
- Frisén, Lars, 1939
(author)
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Computerized perimetry: possibilities for individual adaptation and feedback.
- 1988
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In: Documenta ophthalmologica. Advances in ophthalmology. - 0012-4486. ; 69:1, s. 3-9
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Journal article (peer-reviewed)abstract
- Computerized perimetry is often poorly accepted by the tested subjects, presumably because of sparse feedback and lack of adaptation to individual capacity. Several remedies are suggested, including visual response feedback, active correction of erroneous responses, various fixation prompts, and continuous adaptation to current reaction time. Intuitively intelligible result displays are also desirable. A novel format representing threshold level by symbol size may meet this need.
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| 5. |
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| 6. |
- Frisén, Lars, 1939, et al.
(author)
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Episodic astigmatism heralding generalized myopathy: report of a case managed with a new type of soft contact lens.
- 1984
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In: Ophthalmology. - 0161-6420. ; 91:2, s. 179-82
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Journal article (peer-reviewed)abstract
- A 29-year-old woman presented with marked variations in refraction. A few minutes of physical exertion or reading at a close distance induced up to 2D of myopia and 2D of myopic astigmatism, which regressed upon resting with closed eyes. Cycloplegic agents did not affect the refractive changes, which were shown to be due to variations in corneal curvatures. The eyes were otherwise clinically normal. A few months later the patient developed signs of a progressive, generalized myopathy of unknown origin. The muscular disease was resistant to treatment. The refractive changes were effectively controlled by means of a new type of soft contact lens, with a semi-rigid center.
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| 7. |
- Frisén, Lars, 1939
(author)
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Fundus changes in acute malnutritional optic neuropathy.
- 1983
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In: Archives of ophthalmology (Chicago, Ill. : 1960). - 0003-9950. ; 101:4, s. 577-9
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Journal article (peer-reviewed)abstract
- A peculiar dilation and tortuosity of small retinal vessels within the arcuate areas of the retinal nerve fiber layer occurred in a series of patients with acute malnutritional optic neuropathy ("tobacco-alcohol amblyopia"). These evanescent vascular abnormalities may be caused by arteriovenous shunting. They seem to be specific indicators of the early phase of this disease.
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| 8. |
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| 9. |
- Frisén, Lars, 1939
(author)
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High-pass resolution targets in peripheral vision.
- 1987
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In: Ophthalmology. - 0161-6420. ; 94:9, s. 1104-8
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Journal article (peer-reviewed)abstract
- Visual acuity was measured at 10 degree intervals on the horizontal meridian in two normal subjects, using high-pass spatial frequency filtered test targets in a computer graphics display. The close similarity between detection and recognition thresholds resulted in quick and reliable measurements. Peripheral acuity was proportional to local retinal ganglion cell separation. High-pass targets appear to be nearly ideal for clinical perimetry because of the easy test task and the possibility of interpreting results in terms of numbers of functional neuroretinal channels. The major limitation appears to be a somewhat fuzzy definition of small, circumscribed defects.
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| 10. |
- Frisén, Lars, 1939, et al.
(author)
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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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In: 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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Journal article (peer-reviewed)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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