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T Olsen

Publications and source records attributed to T Olsen.

At least 55 records · Page 3Linked to original sources
PubMed1993

Refractive results after phacoemulsification and ECCE. A comparative study.

The refractive results were evaluated in 79 patients undergoing cataract extraction by phacoemulsification using a 6-7 mm tunnel incision, and compared with a group of 77 patients undergoing planned extracapsular cataract extraction (ECCE) by the same surgeon. A mean increase in the keratometric cylinder of 0.05D and 0.52D was found in the phacoemulsification and the extracapsular cataract extraction group, respectively. This was significantly different from zero for the extracapsular cataract extraction group (p < 0.05) but not for the phacoemulsification group (p > 0.05). By vector analysis, the mean surgically induced astigmatism was 0.91D and 1.36D in the phacoemulsification and the extracapsular cataract extraction group, respectively (p < 0.01). The IOL power prediction error (spectacle plane) was found to be 0.17D (+/- 0.69 SD) in the phacoemulsification group and 0.02 D (+/- 0.79 SD) in the extracapsular cataract extraction group, respectively. We conclude that phacoemulsification improves the surgical control of the refractive outcome of cataract surgery.

Aged↗
PubMed1993

Surveillance of serious recreational injuries: a capture-recapture approach.

Serious injury from sport and recreation is a leading cause of morbidity and mortality in the United States. Historically, occurrences of diseases with substantial public health impact have been monitored via surveillance systems in order to obtain information concerning the frequency with which the diseases occur. Surveillance leads to efforts that identify risk factors, and eventually, control measures to reduce the incidence of disease. Currently, the surveillance of sports injury represents only limited coverage in the U.S. It is important to begin discussions regarding approaches toward the development of surveillance of these injuries. Methods based upon the communicable disease surveillance model could potentially be used to monitor serious sports injuries. One method of surveillance, using the statistical approach of capture-mark-recapture, is presented as an example by which a national system of surveillance of serious sports injury could be established.

Athletic Injuries↗
PubMed1992

[Affective disorders. Drug treatment and electroconvulsive therapy].

Optimal treatment of mood disorders and prevention of suicide requires biological and psychosocial methods, therapeutic alliance and psycho-education. In moderate unipolar depression an antidepressant may be sufficient, if necessary potentiated by another antidepressant or triiodothyronine. In moderate bipolar depression lithium or carbamazepine are preferred. In severe unipolar and bipolar depression the combination of an antidepressant and lithium (or carbamazepine) or electroconvulsive therapy (ECT) is indicated, in psychotic depression neuroleptics, too. Non-selective monoamine oxidase inhibitors (MAOIs) are the most potent antidepressants. Moderate acute mania and mixed state may respond to lithium, carbamazepine or valproate only. In severe cases a neuroleptic and lithium are combined, or these drugs may be combined with carbamazepine or valproate. Electroconvulsive therapy is preferable in acute mixed states with marked confusion or depression. In chronic mixed state and rapid cycling, withdrawal of antidepressants and neuroleptics should be tried. Most patients will need a combination of lithium and carbamazepine or valproate. Added to these drugs, antidepressants are less risky. Adding thyroxin may stabilize rapid cycling. The combination of lithium and an antidepressant is the most potent prophylaxis in unipolar disorder and bipolar disorder dominated by depression.

Adult↗
PubMed1992

Prediction of pseudophakic anterior chamber depth with the newer IOL calculation formulas.

Five methods for predicting pseudophakic anterior chamber depth (ACD) by five previously described intraocular lens power calculation formulas (Binkhorst II, Lepper and Trier, Holladay et al., Sanders-Retzlaff-Kraff (SRK/T), Olsen et al.) were evaluated in a series of 640 patients with a posterior chamber lens implant. Significant differences in formula performance were found in unusually short and long eyes. High errors were found in long eyes with the Lepper and Trier formula, the Holladay formula, and the SRK/T method. The highest accuracy was found with the Binkhorst formula and our previously described linear regression formula which expresses the pseudophakic ACD as a function of the average pseudophakic ACD for a given lens style, the preoperative ACD, and the axial length. The use of the preoperative ACD in combination with the axial length for the prediction of the pseudophakic ACD can therefore be expected to improve the accuracy of IOL power calculation.

Adolescent↗
PubMed1992

Sources of error in intraocular lens power calculation.

The hypothesis that the minimum error in predicted refraction after implantation of an intraocular lens (IOL) of calculated power is the sum of the random error in (1) the measurement of the axial length, (2) the measurement of the corneal power, and (3) the estimation of the pseudophakic anterior chamber depth (ACD) is proposed. Based on preoperative and postoperative biometry of 584 IOL implantations, 54% of the error was attributed to axial length errors, 8% to corneal power errors, and 38% to errors in the estimation of the postoperative ACD, when a fixed ACD was used in the IOL calculations. However, if the ACD was predicted according to a previously described regression method, the contribution of error from the ACD source was reduced to 22%, thereby reducing the total refractive prediction error from +/- 1.03 diopters (D) (+/- SD) to +/- 0.92 D (+/- SD). These predictions accord with clinical results.

Adult↗
PubMed1992

Fluorescein and fluorescein glucuronide in plasma.

The evaluation of the blood-ocular barrier for fluorescein requires the measurement of free and unconjugated fluorescein in plasma. This study introduces a new and simple method for the determination of free fluorescein in plasma on the basis of determined total free plasma fluorescence and the free fraction of fluorescence. An excellent good correlation between differential spectrofluorophotometry and this new method is demonstrated. After intravenous administration of sodium fluorescein, the contribution of fluorescein glucuronide to total free plasma fluorescence was evaluated on basis of the areas under the plasma concentration/time curves for fluorescein and fluorescein glucuronide, respectively. After 1 h 8.2% of total free fluorescence in plasma was found to originate from fluorescein glucuronide and after 24 h 18.3% originated from this metabolite. It was concluded that although plasma fluorescein glucuronide measurements are important in the exact evaluation of the blood-ocular barrier, the contribution of fluorescein glucuronide to vitreous fluorescence after intravenous fluorescein administration seems to be of minor magnitude.

Adult↗
PubMed1992

Long-term kinetic vitreous fluorophotometry.

Fluorophotometric measurements of vitreous and plasma fluorescence were performed in 14 normal subjects up to 24 h after injection of a single intravenous dose of sodium fluorescein. The data were subjected to a kinetic two-compartmental analysis, including the determination of the transfer rate constants between the central and the peripheral compartment (K12 and K21) as well as between the central and vitreous compartment (K(in) and K(out)). In the central compartment (plasma) a mean terminal disposition rate constant (beta) of free fluorescein of 0.23 h-1 was found, corresponding to a half-life of 3.01 h. The vitreous fluorescence reached a maximum 2-5 h after the injection and then declined monoexponentially and very slowly (t1/2 = 9.6 h). The rate constant of permeation into the eye (K(in)) was found to be 0.66 h-1, while the rate constant of elimination of fluorescein from the vitreous was 0.072 h-1 (K(out)). Kin was found to be significantly higher than K12, presumably indicating an active transport mechanism for fluorescein located at the blood-ocular barrier. K(out) was significantly lower than K21, reflecting a slow vitreous elimination of fluorescein. A permeability index defined as the percentage ratio between the areas under the vitreous and the plasma concentration curves was found to be 3.5%, illustrating the poor penetration of fluorescein into the vitreous. Kinetic long-term fluorophotometry appears to be a promising new tool in the study of the blood-ocular barrier.

Administration, Oral↗
PubMed1992

Long-term kinetic vitreous fluorophotometry in normal and diabetic subjects.

Nine normal and 24 diabetic subjects were examined by long-term vitreous and plasma fluorescein fluorophotometry and the observed concentration profiles were described by biexponential time courses. The rate constant of elimination of fluorescein from the body (K10) was significantly decreased in diabetics with background and proliferative retinopathy, presumably caused by affection of the liver and possibly representing alterations in membranes of liver cells. Increased kidney albumin excretion was observed with increasing degree of retinopathy. The apparent rate constant of fluorescein penetration into the eye (Kin) was found significantly decreased in background as well as in proliferative retinopathy; while the permeability index, calculated as areas under vitreous and plasma fluorescein curves, was significantly increased. In the normal subjects Kin was significantly higher than the rate constant of fluorescein transfer (K12) from the apparent central to the peripheral tissue compartment, whereas in the diabetics this difference was only found in the group with background retinopathy. The findings seem compatible with the concept that the breakdown of the blood-ocular barrier could be caused at least partly by affection of an active transport system for fluorescein, but thickening and compositional changes of the basement membranes in the eye might also be of importance.

Adult↗
PubMed1991

Accuracy of the newer generation intraocular lens power calculation formulas in long and short eyes.

The accuracy of two newer generation theoretical intraocular lens (IOL) power calculation formulas and of the empirical SRK I and II formulas was evaluated in a series of 500 IOL implantations including a series of unusually long and short eyes. The prediction error of the theoretical formulas was found to be largely unaffected by the variation in axial length and corneal power, while the prediction of the SRK I formula was less accurate in the short and long eyes. The prediction of the SRK II formula was more accurate than the SRK I in that no systematic offset error with axial length could be demonstrated. However, because of a relatively larger scatter in the long eyes and a significant bias with the corneal power, the absolute error of the SRK II formula was higher than that of the theoretical formulas in the long eyes. The higher accuracy of the newer generation theoretical formulas was attributed to their improved prediction of the pseudophakic anterior chamber depth.

Adult↗
PubMed1991

Secondary IOL power calculation. A comparison of an optical and a biometric method.

In 40 aphakic eyes undergoing secondary IOL implantation, the axial length was calculated optically as well as measured by ultrasound, and the two methods of axial length determination were compared to evaluate the accuracy in the calculation of secondary IOL power. The mean refractive prediction error (+/- SD) was 0.18 diopters (+/- 0.96) and -0.37 diopters (+/- 0.83) using the optical and the biometric method, respectively. The difference in mean value was significant, whereas the variation around the mean value was not found to be significantly different between the two methods. A calculated axial length may offer a valuable alternative to biometry in the aphakic eye, increasing the accuracy of secondary IOL power calculation.

Adolescent↗
PubMed1990

[HIV infection, syphilis and genital diseases in Maun, Botswana].

The prevalence of HIV-infection was studied in a district hospital in Botswana, in southern Africa. Sera from 466 patients were analysed. The sexually transmitted diseases (STD) group consisted of 175 women and 178 men, who consulted the STD-clinic for complaints which could be attributed to STD or infertility and the antenatal clinic (ANC) group consisted of 113 pregnant women, who attended routine ANC. Sera were analysed with HIV-ELISA, and 3% were positive. All sera were negative in Western blot and were considered false-positive in HIV-ELISA. In the STD group, 42% of the women and 39% of the men, were seropositive for syphilis, while 41% were positive in the ANC group. The figures for clinically demonstrated genital lesions were 33%, 60% and 13%, respectively. It is concluded that HIV-infection is a new disease in Botswana, and that the prevalence is still low in the rural population examined in the present survey.

Botswana↗
PubMed1990

Theoretical versus SRK I and SRK II calculation of intraocular lens power.

The predictability of a theoretical, computerized (PC-assisted) intraocular lens (IOL) power calculation method and of the Sanders-Retzlaff-Kraff [SRK] I and II methods was evaluated from preoperative and postoperative biometry in 202 cataractous patients who had extracapsular cataract extraction (ECCE). The theoretical method resulted in the lowest range and standard deviation of the error, and the highest correlation coefficient between the observed and the predicted refraction (P less than .05). The superiority of the theoretical approach was most clearly demonstrated when the postoperative measurements were used in the predictions (P less than .001). This demonstrated the potential accuracy of the formula used and the importance of incorporating methods to predict the IOL position after surgery. If the prediction of the IOL chamber depth was properly corrected for the axial length dependence, a high prediction accuracy could be obtained in short as well as in long eyes.

Adult↗
PubMed1990

Prediction of postoperative intraocular lens chamber depth.

The postoperative intraocular lens (IOL) chamber depth was predicted using a multiple linear regression analysis of the postoperative chamber depth as a function of the corneal height, the preoperative chamber depth, and the axial length in 279 patients with a posterior chamber lens implant. Based on a linear regression formula incorporating these preoperatively defined parameters, the postoperative IOL chamber depth could be predicted with a correlation coefficient of 0.71 and an error of +/- 0.30 mm (SD). It is concluded that an individual prediction of the IOL chamber depth will improve the accuracy in IOL calculation.

Aged↗
PubMed1990

Contrast sensitivity in patients with a new type of multifocal intraocular lens.

Contrast sensitivity was measured in 13 pseudophakic eyes of ten patients who had a new type of diffractive multifocal intraocular lens (IOL) and compared with an age-matched control group with a conventional monofocal IOL. All selected cases had a postoperative follow-up of four to six months and a corrected visual acuity of 20/20 or better. For distance vision, no significant difference in contrast sensitivity could be found between the two groups, indicating an uncompromised distance focus of the multifocal IOL. For near vision, an overall decrease in the contrast sensitivity of 0.19 log units (mean value across the tested frequency from 1.5 to 18 cycles/deg) was found in the multifocal group when these patients were tested without near addition and compared with the controls with near addition (P less than .05). This indicated the near focus of the multifocal IOL to be somewhat less efficient than the far focus. We find these results promising for the new diffractive multifocal IOL.

Accommodation, Ocular↗
PubMed1990

Contrast sensitivity as a function of focus in patients with the diffractive multifocal intraocular lens.

Contrast sensitivity as a function of focus and visual acuity as a function of contrast were investigated in 19 patients with a diffractive multifocal intraocular lens and compared with 19 control patients with a conventional monofocal implant. The contrast sensitivity of the multifocal patients followed a bimodal curve with a maximum sensitivity at the far focus and a second peak at the near focus, corresponding to about +3 diopters in the spectacle plane. The maximum sensitivity of the multifocal group was 0.14 log units lower than the control group (P less than .05). In the near region, the contrast sensitivity of the multifocal patients exceeded that of the control group from +2 diopters and inward. No difference in distance visual acuity was found with high contrast letters. With intermediate contrast letters, the visual acuity of the multifocal patients was lower than that of the control group (P less than .05).

Aged↗