Biomedical subjects

U L Nilsson

Publications and source records attributed to U L Nilsson.

8 recordsLinked to original sources

PubMed2001

Development of a microporous membrane liquid-liquid extractor for organophosphate esters in human blood plasma: identification of triphenyl phosphate and octyl diphenyl phosphate in donor plasma.

An extractor has been developed for microporous membrane liquid-liquid extraction (MMLLE) of lipophilic xenobiotics at trace levels in biological fluids. This new construction allows the sample phase to be stirred, while the organic phase is pumped. The extractor was evaluated using human blood plasma with added organophosphate esters. The size exclusion properties of the membrane reduced lipid co-extraction by approximately 94% compared to ordinary liquid-liquid extraction. In combination with a solid-phase extraction (SPE) step, the method was shown to remove plasma lipids efficiently and thus allow gas chromatographic separation of the compounds. The clean-up method described, including the SPE step, showed a high level of reproducibility, and recoveries of between 72 and 83% were obtained for five of the organophosphate esters after a 200-min extraction period. Using this technique, triphenyl phosphate and an isomer of octyl diphenyl phosphate were detected in human plasma obtained from blood donors. The concentration of triphenyl phosphate ranged between 0.13 and 0.15 microg/g plasma.

Blood Donors↗

PubMed1998

Location and stability of a newly established eccentric retinal locus suitable for reading, achieved through training of patients with a dense central scotoma.

Six patients, median age 71 years, with a dense central scotoma in one eye and a median visual acuity of 0.06 (20/330) in the same eye, were all (100%) shown by means of fundus photography including a fixation target to preferably use an unfavorable retinal locus for fixation, i.e., within the lesion (scotoma). None of the patients was able to read novel text with the affected eye. A computer and video display system were used to determine the most suitable area above or below the visual field scotoma (below or above the retinal lesion) for reading and the magnification needed at this eccentricity. The same setup was also used for an introductory training in reading single words as well as scrolled text with the aim of establishing a preferred retinal locus (PRL) at a favorable, eccentric position, the trained retinal locus (TRL). Thereafter, the patients were provided with strong positive lenses (median power, 40 D) for reading printed text at a very short reading distance (median, 2.5 cm), first single words, above and below which help lines were printed to facilitate eccentric fixation, and finally, novel text. The total training time was 4 to 5 h. Thereafter, fundus photography showed that five of the patients (83%) used their TRL as their PRL. Reading speed was 71 words per minute (median). Our results seem to indicate that an eccentric PRL favorable for effective reading can be established through training and that a fairly low number of training sessions is required.

Aged↗

PubMed1995

A computer and video display based system for training eccentric viewing in macular degeneration with an absolute central scotoma.

A new approach designed to establish the most suitable area for eccentric viewing and to teach and train patients with severe age-related macular degeneration (AMD) to use the eccentric viewing technique is described. Using a computer and video display based system, as well as software written specifically for this purpose, we investigated and trained ten consecutive patients with AMD. The patients were 80.1 + or - 5.6 years old, on average. All of them had an absolute central scotoma. Mean visual acuity was 0.035 + or - 0.016. After 30 min of testing, instruction and reading on the screen, followed by 2.6 + or - 0.69 one-hour training sessions, on average, with the low vision therapist, reading newspaper and book texts with the aid of hyperoculars or aplanatic systems and a very short reading distance, the patients achieved a reading speed of 58.9 + or - 19.7 words/min, significantly (p<0.001) higher than the initial speed when reading on the screen, 11.5 + or - 4.5 words/min.

Aged↗

PubMed1995

Colour contrast sensitivity in patients with soft drusen, an early stage of ARM.

The present institutional study was undertaken in order to determine whether testing of colour contrast sensitivity is valuable in detecting early functional changes in patients at initial stages of age-related maculopathy (ARM). The study included 27 patients with soft drusen as an early sign of ARM and 29 age-matched normals. The area occupied by drusen was determined using a computer program. Colour contrast sensitivity was measured with a computer graphics system. Visual acuity, central visual field (Humphrey Field Analyser) and colour vision (D-15 panel) were normal in both groups. Mean colour contrast sensitivity was significantly lower in patients with early ARM (for the protan axis: p = 0.00019, for the deutan axis: p = 0.000078 and for the tritan axis: p = 0.000096) than in the controls. Interindividual variations were large. There was a tendency towards a bimodal distribution for all three colour axes, most evident for the tritan axis. We found a correlation of the drusen area with the protan and deutan thresholds for the fundus colour photographs r = 0.5 (p < 0.01) and r = 0.4 (p < 0.05), respectively, and with the tritan threshold for the angiograms r = 0.5 (p < 0.05). The findings suggest that colour contrast sensitivity may offer an additional possibility of predicting exudative ARM. Whether the patients with the highest thresholds are those who will be the first to show progression with indications of exudative ARM is not yet known. The patient group will be followed up in order to elucidate this question.

Aged↗

PubMed1993

Contrast sensitivity peripheral to an absolute central scotoma in age-related macular degeneration and the influence of a yellow or an orange filter.

Contrast sensitivity for static and dynamic gratings was determined in 17 patients with age-related macular degeneration (AMD) and an absolute central scotoma. Using electronic and computerized equipment, we established contrast sensitivity peripheral to the scotoma at spatial frequencies of 0.5, 1.0 and 2.0 cycles/degree. We found that mean contrast sensitivity was significantly (p < 0.001) lower than that of a control group at a comparable eccentricity, and that interindividual variations were large. Furthermore, we investigated the influence of a yellow and an orange filter on contrast sensitivity peripheral to such an absolute central scotoma in AMD. The results showed significant (p < 0.01-0.05) improvements in contrast sensitivity at certain spatial frequencies only, i.e., for the yellow filter at 2.0 c/deg and for the orange filter at 0.5 and 1.0 c/deg, and only with dynamic presentation. No objective improvement in visual acuity could be demonstrated when using filters. Thus, our findings do not unequivocally support the regular prescription of such filters in order to improve contrast vision in AMD with an absolute central scotoma.

Aged↗

PubMed1988

Visual rehabilitation of patients with advanced stages of glaucoma, optic atrophy, myopia or retinitis pigmentosa.

Ninety-six patients with advanced stages of glaucoma, optic atrophy, myopia or retinitis pigmentosa (RP) who could not manage with ordinary spectacles or simple magnifying aids were taken care of at the Low Vision Clinic for rehabilitation and followed for an average of 3.6 years (the glaucoma group) up to an average of 6.0 years (the optic atrophy group). They were given high power optical aids and subjected to educational training in the proper use of these aids for best utilization of residual vision. Many of them (for optic atrophy as high a percentage as 40.7) were taught to use extra macular retina by means of eccentric viewing technique. The mean age of the oldest group, the glaucoma patients, was 69.3 years. The three other groups were about 20 to 25 years younger, on an average. (Another 35 patients were seen for the first series of visits but could not be followed up, the main reasons being death (13 patients) and moving out of the area (9 patients). The mean power of the aids (mainly telescopes) used for distance vision was 2.1 x (RP)-5.3 x (optic atrophy). Increased near addition and hyperocular lenses were the main aids for reading and near vision, the mean power being 17.0 dioptres (glaucoma)-23.5 dioptres (RP)(4.3 x -5.9 x). Aids were also provided for intermediate distance and for "spot use". The mean number of series of visits was 3.1 (myopia)-3.5 (glaucoma) and the average number of 1 h training sessions 2.2 (glaucoma)-2.5 (optic atrophy, RP) per series of visits. With aids and educational training, the mean visual acuity improved on the first series of visits from 0.31 to 0.60 for the glaucoma group, from 0.19 to 0.70 for the optic atrophy group, from 0.12 to 0.68 for the myopes and from 0.35 to 0.52 for the RP group. After the last series of visits acuity was still as good as 0.51, 0.61, 0.73 and 0.45, respectively. The number of individuals able to read newspaper text increased from 16.1% to 100.0% for the glaucoma patients, from 14.8% to 100.0% for the optic atrophy patients, from 75.0% to 100.0% for the myopes, and from 50.0% to 95.5% for the RP patients. The results show clearly that the methods used for rehabilitation of patients with glaucoma, optic atrophy, myopia or RP through optical aids and sessions of educational training are very successful, with substantial improvement of life quality.

Adolescent↗

PubMed1986

Rehabilitation of the visually handicapped with advanced macular degeneration. A follow-up study at the Low Vision Clinic, Department of Ophthalmology, University of Linköping.

Hundred-and-twenty patients with advanced macular degeneration (senile, disciform, and hereditary forms), which could not be helped in a satisfactory way by simple magnifying aids, were studied for an average of 5 years (a minimum of 3 years), during which they had access to a full range of low vision rehabilitation measures including advanced optical aids and educational methods for training in the use of these aids and in the utilization of residual vision. The mean age of the patients was 72 years. They were all in a mental condition enabling them to understand and follow instructions. Just over half the patients were obliged to learn from the outset how to utilize peripheral retina, i.e. through eccentric viewing, high magnification low vision aids and very short reading distances, a mean of 4.4 cm, which demand specially qualified educational methods for low vision training. (A second group of 198 patients with macular degeneration was handled by the optician alone because either macular degeneration was moderate and the patients could manage with simple optical aids, or the patients were in such a bad mental condition, obvious already from the referral documents, that they were unable to use sophisticated aids in spite of the fact that they would have needed them with regard to their poor vision.) Telescopes were the most frequent aid used for distance, having a mean magnification of 4.6 X. Among the aids for reading, the most common were increased near additions and hyperocular lenses, having a mean power of 22.6 dioptres (magnification 5.7 X). Aids were also furnished for intermediate distance and for 'spot use'. The mean number of series of visits was 2.5 and the number of training sessions (1 h) per series of visits was 3.0. Mean visual acuity improved from 0.18 to 0.64 with aids and training on the first series of visits, and reached 0.53 by the last series. The number of patients able to read TV titles increased from 6.7% to 57.5% and was 49.2% after the last series of visits. The number of individuals able to read newspaper text increased from 0.8% to 92.5%. After the last series of visits, the number was still as high as 80.0%. The results show that the presented methods for rehabilitation of patients with macular degeneration through optical aids and educational methods for training in the utilization of these aids and of residual vision are outstandingly successful. The use of the individual's vision and his situation in life often improve dramatically.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗

PubMed1986

Visual rehabilitation of patients with advanced diabetic retinopathy. A follow-up study at the Low Vision Clinic, Department of Ophthalmology, University of Linköping.

Seventy-nine patients with advanced diabetic retinopathy were subjected to a full range of low vision rehabilitation measures and followed for an average of 3.6 years at the Low Vision Clinic. They were provided with high power optical aids, followed by educational training in the use of such aids and of residual vision, including the utilization of peripheral retina by means of eccentric viewing technique in many cases (23%). Mean age was 52.7 years. Type I diabetes was diagnosed in 69 subjects and type II in 10 subjects. Proliferative retinopathy was present in 73 cases and background retinopathy in 6 cases. All subjects showed macular changes in varying degrees. (Another 36 patients participated in the first series of visits but could not be followed up, the main reason being that 31 of them died before follow-up. There were no major differences between the two groups regarding rehabilitation results.) The average power of the telescopes used for distance vision was 4.8 X, and the mean power of the aids used for reading and near vision, mainly increased near addition and hyperocular lenses, was 22.2 dioptres (5.6 X). The patients were also provided with aids for intermediate distance and for 'spot use'. The average number of series of visits was 2.7 and the number of 1 h training sessions 2.5 per series of visits. With aids and training, mean visual acuity improved from 0.17 to 0.73 on the first series of visits. After the last series of visits acuity was still as good as 0.64. Ability to read TV titles increased from 15.2% to 79.7% in the group and reached 64.6% after the last series of visits. The number of individuals able to read newspaper text increased from 1.3% to 97.5%. After the last series of visits the number was still as large as 86.1%. Of the individuals who had to stop working because of poor vision, 89% would have been able to return to work after rehabilitation. However, because of unemployment problems in the area, only 72% managed to return. It is quite obvious from the results that the presented methods, including high power aids and training sessions, are extremely successful in rehabilitation of patients with advanced diabetic retinopathy, provided that they have at least some residual vision. Dramatic improvements in visual performance were seen, allowing a life of much better quality than before.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗