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Biomedical subjects

O Pärssinen

Publications and source records attributed to O Pärssinen.

At least 19 recordsLinked to original sources
PubMed1998

Compression forces of haptics of freely rotating posterior chamber intraocular lenses.

PURPOSE: To measure the compressive forces of the haptics of 28 intraocular lens (IOL) models for different modes of compression and compare the results of two types of measurements. SETTING: Department of Ophthalmology, Central Hospital of Central Finland, Jyväskylä, Finland. METHODS: The haptics of 28 types of IOLs were compressed to a diameter of 9.0 mm between curved anvils. The compression forces in the plane of compression (i.e., in the plane of the optics) were measured at 0.5 mm intervals. During compression, the optics and the haptics were free to rotate with respect to the anvils. The results were compared with those of earlier measurements in which the optics were held fixed during compression. Perpendicular forces were measured at 0.4 mm intervals. RESULTS: The measured forces in the plane of the optics varied between 114 and 659 mg at a diameter of 10.0 mm and 192 and 1047 mg at a diameter of 9.0 mm. When compressed to 10.0 mm in diameter, the forces were 1 to 75% lower than when lens rotation was not possible. The forces perpendicular to the optic varied between 0 and 96 mg at a 10.0 mm diameter and correlated with the forces in the plane of the optic. CONCLUSION: The compression forces of the lens haptics were generally lower when the lenses were allowed to rotate during compression. The orders of stiffness of the haptics in these two measurements were similar. The perpendicular forces were generally small and correlated significantly with the forces measured in the plane of the optic.

Compressive Strength↗
PubMed1997

Compression forces of haptics of selected posterior chamber lenses.

PURPOSE: To compare the compressive forces of the haptics of different intraocular lens (IOL) models and analyze the observed differences. SETTING: Central Hospital of Central Finland and University of Jyväskylä, Jyväskylä, Finland. METHODS: The haptics of 28 IOL models were compressed to a diameter of 9.0 mm. The compression forces were measured at 0.5 mm intervals. The conclusions were verified by numerical simulations of mechanical models of the lenses. RESULTS: The measured forces varied between 100 and 601 mg at a diameter of 11.0 mm, 206 and 1057 mg at a diameter of 10.0 mm, and 315 and 2094 mg at a diameter of 9.0 mm. The slopes of the force curves of the three-piece lenses were fairly linear. In general, the three-piece models were less rigid than one-piece models and underwent plastic deformations after repeated compressions. For most one-piece models, compression force increased progressively with increasing compression. The overall IOL diameter and differences in haptic thickness and length and the angle between optic at the point of haptic insertion were the main causes of the observed differences in the compression forces. The variation in forces between individual specimens of the same model, which occurred with almost all models, were mainly the result of variations in haptic thickness. CONCLUSION: Great variations in the compression forces of the IOL haptics were found. Compression behaviors should be taken into account when selecting a lens to implant.

Compressive Strength↗
PubMed1997

Acute glaucoma and acute corneal oedema in association with tularemia.

PURPOSE: To describe the clinical course of oculoglandular tularemia with acute glaucoma and corneal oedema. METHODS: Clinical course, results of laboratory assays and treatment of oculoglandular tularemia in a 58-year-old woman. RESULTS: The patient had acute glaucoma and corneal oedema in connection with acute tularemia. At the onset of the disease she had a fever (39 degrees C), pains in her muscles and in her right eye. The intraocular pressure, which was 68 mmHg at the beginning was lowered with intravenous and per oral acetatcolamide together with timolol and pilocarpine eyedrops, and because of a narrow anterior chamber, with subsequent laser iridotomies. The tularemia was treated with ciprofloxacin 500 mg twice daily for ten days. Vision was finger counting at the beginning of the disease. The corneal oedema gradually subsided and vision normalized during the two-month follow-up. CONCLUSION: Oculoglandular tularemia was connected with acute glaucoma and corneal oedema.

Acute Disease↗
PubMed1994

Sensitivity of the central visual field in 70- to 81-year-old male athletes and in a population sample.

The sensitivity of the central visual field (0 degree-30 degrees) was studied using an automatic Octopus 500E perimeter in elderly male athletes and in a population sample of men of corresponding age. The athletes (N = 96) were endurance and power athletes, who were still active in competitive sports with training histories spanning tens of years. The athletes' results were compared with those of a sample of men of the same age (70-81 years, N = 41) randomly selected from the local population register. The sensitivity values of the athletes, and the endurance athletes in particular, were significantly better than those of the controls, with differences varying from 1 to 2.5 dB in the different areas of the central visual field. Multivariate analyses of the background factors of visual field sensitivity showed that the most important were age, amount of annual training, number of chronic diseases, HDL-cholesterol level, and vital capacity. The results suggest that a long training history, especially of the aerobic type, may be beneficial with respect to the sensitivity of the visual system.

Aged↗
PubMed1994

Retinal light sensitivity of the central visual field among 70- to 81-year-old men and women.

Retinal light sensitivity of the central visual field (0-30 degrees), visual acuity, intraocular pressure and pupillary size were screened in 42 men and 42 women aged 70 to 81 years. The subjects were randomly selected from the population register. After excluding the diagnosed glaucoma cases, the men had better visual field light sensitivity values than the women. They also had lower intraocular pressure and a wider pupillary diameter than the women, whereas there were no differences in visual acuity between the sexes. When the effect of pupillary size was controlled the differences in visual field light sensitivity values between men and women became non-significant. Among these elderly people there was a negative correlation between retinal light sensitivity and age among the men but not among the women.

Aged↗
PubMed1994

Intraocular pressure in samples of elderly Finnish and Swedish men and women.

Intraocular pressure was measured in 231 systematically sampled 75-year-old men and women in Göteborg, Sweden and in 284 75-year-old and 201 80-year-old residents in Jyväskylä, Finland as part of a comparative study on functional capacity and health, NORA 75 (Nordic Research on Ageing). After excluding the cases reporting glaucoma in their medical history or using drugs for glaucoma treatment there were no significant differences in the distributions of intraocular pressure between the men (mean intraocular pressure in the right eye 15.1 mmHg, left eye 15.0 mmHg) and women (mean intraocular pressure in the right eye 15.5 mmHg, left eye 15.8 mmHg) in Göteborg. In Jyväskylä the 75-year-old men had significantly lower intraocular pressure (right eye 13.4 mmHg, left eye 14.2 mmHg) than either the Jyväskylä women (right eye 15.1 mmHg, left eye 15.4 mmHg) or the men and women in Göteborg. Among the 80-year-olds in Jyväskylä there were no significant differences between the sexes (means for the right eye 14.0 mmHg and 13.7 mmHg and for the left eye 13.9 mmHg and 13.7 mmHg for the men and the women, respectively). The 80-year-old women had lower intraocular pressure than the 75-year-old women of either location. Ouclar hypertension (intraocular pressure 22 mmHg or higher) was more common among the Swedish 75-year-olds than among either the Finnish 75- or 80-year-olds.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1993

Ophthalmic manifestations of epidemic nephropathy.

An ophthalmic examination was performed on 29 epidemic nephropathy patients consequently treated in the Central Hospital of Central Finland during the acute phase of the disease. Twenty-six of those patients were reexamined after an interval of one month. In the acute phase of the disease pathological ophthalmic changes were found in 15 cases (52%). The symptoms observed were conjunctival injection, oedema, flare and cell reaction in anterior chamber, anisochoria, retinal oedema, acute glaucoma and myopic shift of refraction. The main effect of disease on intraocular pressure was pressure-lowering. The myopic shifts were not dependent on initial refraction. In one case of acute glaucoma this shift could be explained by swelling and forward movement of the lens.

Acute Disease↗
PubMed1993

Effect of bicycle ergometer test on intraocular pressure in elderly athletes and controls.

To evaluate the effect of intensive physical exercise on intraocular pressure (IOP) in 66- to 85-year-old subjects IOP was measured before and after a maximal bicycle ergometer test. The non-glaucomatous subjects comprised 85 males and 36 female athletes and 16 male and 22 female controls of corresponding age drawn from a population register. IOP was measured using a non-contact tonometer. The results indicated a decrease (> or = 2 mmHg) in 34% of the subjects, no change in 57% and an increase in 9%. The decrease was more pronounced in subjects with higher pre-test values. In all four subjects with a pre-test value above 22 mmHg a reduction from 4 to 11 mmHg was observed. The change in IOP during physical loading was not significantly associated with the intensity and duration of exercise test. Three of the 5 male subjects with diagnosed glaucoma and undergoing hypotensive medication, who were analyzed separately, also showed a reduction in IOP during loading. In the pre- or post-test values there were no differences between the athletes and controls, while women tended to have higher IOP values than men. It is concluded that physical loading has predominantly a moderating effect, if any, on IOP in elderly men and women.

Aged↗
PubMed1993

Myopia and myopic progression among schoolchildren: a three-year follow-up study.

PURPOSE: To discuss the factors that might explain the rate of myopic progression and the degree of myopia after a 3-year follow-up among schoolchildren with myopia. METHODS: Myopic progression among 238 schoolchildren was followed up in a randomized clinical trial of myopia treatment. The associations between the explanatory factors and myopic progression and the final value of the spherical equivalent after the follow-up were studied by analysis of variance and regression analysis. RESULTS: Myopia progressed faster among girls than boys. According to the regression models for the boys, 25% of the variation of myopic progression and 57% of the final spherical equivalent could be explained by initial spherical equivalent, age at receiving first spectacles, time spent on sports and outdoor activities, and on reading and close work. Among the girls, 30% of myopic progression could be explained by age at receiving first spectacles, time spent on reading and close work, and reading distance. Similarly, 49% of the final spherical equivalent could be explained by age at receiving first spectacles, initial spherical equivalent, time spent on reading and close work, and reading distance. The rest of the variations could not be explained by the variables measured in this study. CONCLUSIONS: The factors with the most significant relationships to myopic progression were sex, age of onset, and degree of myopia at the beginning of the follow-up. Myopic progression and final myopia were related to time spent on reading and close work and to reading distance but not, however, to accommodation stimulus.

Accommodation, Ocular↗
PubMed1991

Astigmatism and school myopia.

Changes in astigmatism were followed for a 3-year period among 238 myopic children as part of a clinical trial of myopia treatment. Children with mild myopia and no previous myopic spectacle correction and astigmatism less than or equal to 2 D were included in the study. The prevalence of astigmatism of at least 0.25 D was 55% at the beginning of the follow-up at a mean age of 10.9 years, increasing to 76% during the 3-year period. At the same time the mean astigmatism increased from -0.26 D to -0.45 D. Most of the astigmatism was against the rule; with the rule astigmatism represented 18% of the astigmatism at the beginning and 24% at the end of the study. There was a weak correlation between the spherical equivalent and astigmatism at the beginning of the follow-up (r = 0.122, n = 240, P = 0.029) but not at the end of the follow-up. Myopic progression controlled for the spherical equivalent, was not related to degree of astigmatism at the beginning of the study.

Astigmatism↗
PubMed1990

Anisometropia and changes in anisometropia in school myopia.

Human anisometropia and changes in it were followed over a 3-year period in 238 schoolchildren who had uncomplicated school myopia in both eyes. Anisometropia of the spherical equivalent (ASFE) type increased in 27%, decreased in 6%, and remained unchanged in 67% of these children. When mean myopia increased from -1.43 to -3.06 D, mean ASFE increased from 0.30 to 0.51 D and the anisometropia of astigmatism (AAST) from 0.15 to 0.23 D. The faster the increase in myopia the greater was the increase in ASFE (r = 0.133, N = 238, p = 0.020). The higher the spherical equivalent at the end of the study the higher was the ASFE (r = 0.135, N = 238, p = 0.019). The initial refractive error or the amount or the axis of astigmatism did not have any prognostic value for the changes in ASFE. The higher the ASFE at the end of the study the higher also was the AAST (r = 0.136, N = 238, p = 0.018). The change in ASFE was independent of the wearing of spectacles. The distribution of the anisometropia of the spherical equivalent and its change followed a nearly normal distribution with the peak of eyes at about +/- 0 refraction.

Anisometropia↗
PubMed1990

Intraocular pressure in school myopia.

The relationship between intraocular pressure and ocular refraction and axial length were studied in a follow-up of myopic children and in a cross-section sample of school children. In the follow-up group intraocular pressure significantly decreased with age. Mean intraocular pressure at the mean age of 10.9 years was 17.4 mmHg, and three years later 16.1 mmHg. Intraocular pressure above 20 mmHg was recorded in 7.6% of total measurements in the follow-up group and in 8.7% of cases in the cross-section sample. There was a significant correlation between mean intraocular pressure and the spherical equivalent both at the beginning and at the end of the study in the follow-up group and in the cross-section sample among the boys only. There was also a significant positive correlation between intraocular pressure and axial length at the end of the follow-up among the boys but not among the girls.

Adolescent↗
PubMed1989

Effect of spectacle use and accommodation on myopic progression: final results of a three-year randomised clinical trial among schoolchildren.

Two hundred and forty mildly myopic schoolchildren aged 9-11 years were randomly allocated to three treatment groups and the progression of myopia was followed-up for three years. The treatment groups were: (1) minus lenses with full correction for continuous use (the reference group), (2) minus lenses with full correction to be used for distant vision only, and (3) bifocal lenses with +1.75 D addition. Three-year refraction values were received from 237 children. The differences in the increases of the spherical equivalents were not statistically significant in the right eye, but in the left eye the change in the distant use group was significantly higher (-1.87 D) than in the continuous use group (-1.46 D) (p = 0.02, Student's t test). There were no differences between the groups in regard to school achievement, accidents, or satisfaction with glasses. In all three groups the more the daily close work done by the children the faster was the rate of myopic progression (right eye: r = 0.253, p = 0.0001, left eye: r = 0.267, p = 0.0001). Myopic progression did not correlate positively with accommodation, but the shorter the average reading distance of the follow-up time the faster was the myopic progression (right eye: r = 0.222, p = 0.0001, left eye: r = 0.255, p = 0.001). It seems that myopic progression is connected with much use of the eyes in reading and close work and with short reading distance but that progression cannot be reduced by diminishing accommodation with bifocals or by reading without spectacles.

Accommodation, Ocular↗
PubMed1988

Spectacle-use, bifocals and prevention of myopic progression. The two-years results of a randomized trial among schoolchildren.

This paper gives the two-year follow-up results of a randomized trial of three different types of corrective lenses: 1) minus lenses with full correction for continuous use (the Reference group); 2) minus lenses with full correction to be used for distant vision only; and 3) bifocal lenses. A total of 240 9-11-years old mildly myopic schoolchildren were randomly allocated to the three different treatment groups to be followed up for 3 years. After 2-years follow-up the change in the spherical equivalent was greatest in the distant use group. There were no significant positive correlations between changes in refraction and accommodation or refraction and convergence.

Accommodation, Ocular↗
PubMed1987

Prevention of myopic progress by glasses. Study design and the first-year results of a randomized trial among schoolchildren.

We report the design and first-year follow-up results of a randomized trial of three different types of corrective lenses: (1) minus lenses with full correction for continuous use (the reference group); (2) minus lenses with full correction for distant vision only; and (3) bifocal lenses. Two hundred and forty 9- to 11-year-old mildly myopic schoolchildren were randomly allocated to the three treatment groups to be followed up to 3 years. During the first year, 73% of the children were compliant with their treatment. Refraction values after the first year were obtained from all but one child. In the second group (spectacles for distant vision only) myopia had progressed somewhat more than in the reference group. In respect of other values (school achievement, reading habits, and accidents) there were no statistically significant differences between the groups.

Accommodation, Ocular↗
PubMed1987

Need for near vision in daily work in different occupational groups.

To evaluate the need, characteristics and proportion of occupational accurate close work in different socio-economic groups we sent a questionnaire to all 26- and 46-year-old people in the Jyväskylä district. 1,503 (75%) of the 26-year-old subjects and 1,035 (78%) of the 46-year-old subjects returned the questionnaire. 71% of the 26-year-old subjects and 68% of the 46-year-old subjects reported that they need accurate near vision in their daily work. Accurate near vision was needed for reading and writing in 61% in the younger and 55% in the older age group, industrial quality control in 14% in the younger and in 26% in the older age group, Visual Display Unit work in 7% in both age groups, and other accurate close work in 19% in the younger and in 12% in the older age group. The results show that there is a need for accurate near vision in most occupations and indicate that the visual acuity and refraction of the employee requiring occupational accurate near vision should be examined when newly employed and when having problems with near work.

Adult↗