| 1. |
- 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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| 2. |
- Frisén, Lars, 1939
(författare)
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High-pass resolution perimetry. A clinical review.
- 1993
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Ingår i: Documenta ophthalmologica. Advances in ophthalmology. - 0012-4486. ; 83:1, s. 1-25
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Forskningsöversikt (refereegranskat)abstract
- Review of all available reports comparing high-pass resolution perimetry (HRP) and conventional perimetry in normals and in subjects with different visual disorders reveals closely comparable aspects of sensitivity, specificity, and reliability. HRP shows important advantages concerning variability, test duration, and subject preferences. Drawbacks seem largely limited to somewhat loose renditions of visual field defects of small area and large depth. Otherwise HRP's novel format of graphic result presentation may be better suited to visual evaluation than conventional gray-scale maps with their lumping of thresholds and extensive interpolations. Several examples are provided of visual field defects due to various lesions throughout the visual system.
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| 3. |
- Frisén, Lars, 1939
(författare)
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High-pass resolution perimetry and age-related loss of visual pathway neurons.
- 1991
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Ingår i: Acta ophthalmologica. - 0001-639X. ; 69:4, s. 511-5
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Tidskriftsartikel (refereegranskat)abstract
- The normal, age-related decline of results of high-pass resolution perimetry (HRP) predicts a loss of approximately 9,000 retino-cortical neural channels per year of age, or about 1 channel each hour. Previously published counts of numbers of neurons in the optic nerve indicate a loss of approximately 5,000 neurons per year. The HRP results can be accounted for by postulating that neurons are lost at the same rate also in the geniculo-striate visual pathway.
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| 4. |
- Frisén, Lars, 1939
(författare)
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High-pass resolution perimetry: central-field neuroretinal correlates.
- 1995
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Ingår i: Vision research. - 0042-6989. ; 35:2, s. 293-301
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Tidskriftsartikel (refereegranskat)abstract
- Minimum angles of resolution (MAR) were measured at 0-10 deg horizontal eccentricity in three normal subjects, using high-pass spatial frequency filtered targets, at four different contrast levels. Results were correlated with recent data on human cone and ganglion cell separations in corresponding retinal locations. MARs and cone separations showed a close proportionality through the origin for all contrast levels. Ganglion cell correlates were more difficult to elucidate as the cell bodies are displaced from their input cones. Taking a functional estimate of the displacement into account, the number of ganglion cells appeared to be large enough to uphold an "effective" distribution that obeys the same proportional relationship to MAR that previously has been demonstrated outside 10 deg. Analysis of the nature of age effects provided support for this model.
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| 5. |
- Frisén, Lars, 1939, et al.
(författare)
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Properties of high-pass resolution perimetry targets.
- 1993
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Ingår i: Acta ophthalmologica. - 0001-639X. ; 71:3, s. 320-6
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Tidskriftsartikel (refereegranskat)abstract
- Relationships between high-pass resolution perimetry ring targets and conventional perimetry and acuity targets were explored by optical analytical techniques and by comparative measurements in normal humans. High-pass resolution and acuity targets produced closely proportional resolution measurements, showing that the critical ring detail is the width of the bright core. High-pass resolution and conventional perimetry thresholds were not equally well correlated. From a purely optical point of view, high-pass resolution targets appeared to lose somewhat more contrast on defocusing. On the other hand, high-pass resolution appears to show less variability in practical, clinical use.
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| 6. |
- Frisén, Lars, 1939, et al.
(författare)
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Relative dispersion analysis enhances perimetric sensitivity.
- 1996
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Ingår i: Vision research. - 0042-6989. ; 36:3, s. 491-7
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Tidskriftsartikel (refereegranskat)abstract
- Objective identification of minor visual field defects is problematic. A possible solution is to examine spatial correlations by means of relative dispersion analysis, a tool of fractal analysis. We studied patients with glaucoma, previous optic neuritis, chiasmal compression and lesions of the brain hemispheres, using high-pass resolution perimetry. One-hundred visual field records were drawn consecutively for each category and ranked according to severity of defects. Records with scores ranking below the 35th percentile, i.e. those with the smallest field defects, were analysed. Relative dispersion analysis recognized 1.3-2.4 times more abnormal subjects than did pattern standard deviation. A previously described form index was intermediate in sensitivity. Specificity was 96%. Relative dispersion analysis appears to capture a novel aspect of visual field abnormality, with good sensitivity and specificity. The analysis is easily performed.
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| 7. |
- Frisén, Lars, 1939, et al.
(författare)
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Surgically created fourth-third cranial nerve communication: temporary success in a child with bilateral third nerve hamartomas. Case report.
- 1999
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Ingår i: Journal of neurosurgery. - : Journal of Neurosurgery Publishing Group (JNSPG). - 0022-3085. ; 90:3, s. 542-5
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Tidskriftsartikel (refereegranskat)abstract
- Shortly after birth, an otherwise healthy infant developed eye deviation and ptosis due to a hamartomatous lesion of the interpeduncular segment of the right oculomotor nerve. The left nerve became similarly involved when the child was 1.5 years of age. Direct nerve repair was not possible. Instead, the trochlear nerve was divided and its proximal end was attached to the distal end of the third nerve. Elevation of the upper eyelid and partial adduction of the eye developed gradually over the ensuing 3 to 5 months. Both functions were lost after an additional 2 months, presumably as a result of tumor recurrence or neuroma formation. This case report shows that surgically created fourth-third cranial nerve communication is feasible and may merit consideration under similar circumstances.
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| 8. |
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| 9. |
- Lycke, Jan, 1956, et al.
(författare)
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Acyclovir treatment of relapsing-remitting multiple sclerosis. A randomized, placebo-controlled, double-blind study.
- 1996
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Ingår i: Journal of neurology. - 0340-5354. ; 243:3, s. 214-24
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Tidskriftsartikel (refereegranskat)abstract
- Acyclovir treatment was used in a randomized, double-blind, placebo-controlled clinical trial with parallel groups to test the hypothesis that herpes virus infections are involved in the pathogenesis of multiple sclerosis (MS). Sixty patients with the relapsing-remitting form of MS were randomized to either oral treatment with 800 mg acyclovir or placebo tablets three times daily for 2 years. The clinical effect was investigated by an extensive test battery consisting of neurological examinations, neuro-ophthalmological and neuropsychological tests, and evoked potentials. Results were based on "intent-to-treat" data and the primary outcome measure was the exacerbation rate. In the acyclovir group (n = 30), 62 exacerbations were recorded during the treatment period, yielding an annual exacerbation rate of 1.03. The placebo group (n = 30) had 94 exacerbations and an annual exacerbation rate of 1.57. Thus, 34% fewer exacerbations were encountered during acyclovir treatment. This difference in exacerbation rate between the treatment groups was not significant (P = 0.083). However, this trend to a lower disease activity in acyclovir-treated patients was supported in subsequent data analysis. If the patients were grouped according to exacerbation frequencies, i.e. into low (0-2), medium (3-5) and high (6-8) rate groups, the difference between acyclovir and placebo treatment was significant (P = 0.017). Moreover, in a subgroup of the population with a duration of the disease of at least 2 years providing an exacerbation rate base-line before entry, individual differences in exacerbation rates were compared between the 2-year pre-study period and the study period in acyclovir-treated (n = 19) and placebo (n = 20) patients and acyclovir-treated patients showed a significant reduction of exacerbations (P = 0.024). Otherwise, neurological parameters were essentially unaffected by acyclovir treatment and there were no convincing signs of reduced neurological deterioration in the acyclovir group. This study indicates that acyclovir treatment might inhibit the triggering of MS exacerbations and thus suggests that acyclovir-susceptible viruses might be involved in the pathogenesis of MS. This possibility warrants further investigation.
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| 10. |
- Petruson, B, et al.
(författare)
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Decompression of the orbit using a lateral rhinotomy approach in patients with malignant endocrine exophthalmos.
- 1990
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Ingår i: Clinical otolaryngology and allied sciences. - 0307-7772. ; 15:2, s. 181-4
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Tidskriftsartikel (refereegranskat)abstract
- Malignant endocrine exophthalmos is a complication seen in 1-2% of patients treated for thyrotoxicosis. A variety of surgical techniques have been used to prevent loss of vision due to compression of the optic nerve. In this study, nine patients with rapidly diminishing vision were operated upon using a lateral rhinotomy technique creating the largest possible space for expansion into the nose and decompressing the optic nerve far back in the orbit. In all patients the vision was improved 1 year after surgery and the proptosis was decreased.
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| 11. |
- Rossitti, S, et al.
(författare)
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Remodelling of the retinal arterioles in descending optic atrophy follows the principle of minimum work.
- 1994
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Ingår i: Acta physiologica Scandinavica. - : Wiley. - 0001-6772 .- 1365-201X. ; 152:3, s. 333-40
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Tidskriftsartikel (refereegranskat)abstract
- Mathematical modelling indicates that the minimum energy cost for blood flow is achieved when the arteries are arranged in a branching hierarchy such that the radii of the vessels are adjusted to the cube root of the volumetric flow (principle of minimum work). This is known to apply over several magnitudes of vessel calibres, and in many different organs, including the brain, in humans and in animals. This paper addresses the issue of remodelling of one and the same arterial network to long-term changes in blood flow. This has not been studied previously in humans. We measured the radius of parent (r0) and branch segments (r1 and r2) of the retinal arteriolar network in fundus photographs of six patients with blinding, non-vascular retrobulbar optic nerve lesions, mostly traumatic in origin, before and after the development of descending optic atrophy. Attenuation of retinal arterioles is a well-known phenomenon in descending optic atrophy, and is attributable to decreased metabolic demand secondary to loss of the retinal ganglion cells and their axons. On average, arteriolar diameters decreased by 15.2 +/- 17.7% (SD), with 95% confidence intervals of 18.7% and 11.7%; the radii decreased significantly (P = 0.0001) (n = 99). The area ratio of the bifurcations, defined as (r2(1) + r2(2))r-2(0), was 1.23 +/- 0.2 before, and 1.18 +/- 0.2 after optic atrophy (n = 36); the change of area ratio was not significant. The branching geometry of the retinal arteriolar network obeyed strictly the optimum branching rule of the principle of minimum work, or r3(0) = r3(1) + r3(2).(ABSTRACT TRUNCATED AT 250 WORDS)
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| 12. |
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