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Biomedical subjects

B Tengroth

Publications and source records attributed to B Tengroth.

At least 37 records · Page 2Linked to original sources
PubMed1994

Wound healing and myopic regression following photorefractive keratectomy.

Scrapings from the treated area of 17 patients who had undergone photorefractive keratectomy were analyzed. All patients had regressed to myopia and were scraped at the time of retreatment. Three scrapings from the epithelium of patients undergoing primary photorefractive keratectomy served as control. Formalin fixed and paraffin embedded, the specimens were sectioned and stained specifically for hyaluronic acid. Hematoxylin was used for counterstaining in all specimens. Scrapings revealed either epithelial hyperplasia (11 cases) or an increased amount of extracellular material (15 cases) or both (9 cases). Five of the specimens stained positive for hyaluronic acid. Four of these cases showed the highest degree of corneal haze. The latter suggests a role for hyaluronic acid formation in excessive wound healing, causing myopic regression. All patients had received prolonged topical steroid treatment, a measure that may suppress a normal occurrence of hyaluronic acid.

Cornea↗
PubMed1994

Treatment of corneal dystrophies with excimer laser.

Thirty-three eyes with different corneal dystrophies underwent phototherapeutic keratectomy to ablate corneal opacities, surface irregularities and corneal wounds. For most patients the treatment goal was to improve vision but also corneal woundhealing, glare problems and unstable refraction were indications for treatment. In 27 eyes with the treatment goal to improve vision, 23 improved 2 lines or more on the visual chart used. In none of the patients has the treatment led to a worsening of the condition. The mean follow-up time was 9 months. Excimer laser ablation of corneal dystrophies seems to be a good treatment, which can improve visual functions considerably, heal corneal wounds and in this way postpone corneal grafting in many cases.

Adolescent↗
PubMed1993

Excimer laser photorefractive keratectomy for myopia. Clinical results in sighted eyes.

PURPOSE: To evaluate the refractive results of excimer laser photorefractive keratectomy (PRK) performed on normal, sighted myopic eyes; to assess the role of postoperative topical steroid treatment in patients with PRK; and to study the regression of effect. METHODS: An argon fluoride 193-nm excimer laser was used. Photorefractive keratectomy was performed on 420 eyes with preoperative refraction ranging from -1.25 to -7.50 diopters (D). Minimum follow-up time was 12 months, and 194 of the eyes were followed for 15 months. Postoperative treatment generally consisted of topical dexamethasone for 3 months, but in a sub-study, some eyes were treated for only 5 weeks. RESULTS: Mean refraction (spherical equivalent +/- standard deviation) at 12 months was -0.04 +/- 0.84 D and at 15 months -0.22 +/- 0.78 D. At 12 months postoperatively, 86% of the eyes were within 1.00 D of emmetropia, at 15 months 87%. At 12 months, 91% of the eyes had an uncorrected visual acuity of at least 20/40, at 15 months 87%. Eyes treated with dexamethasone for 3 months regressed significantly less than those treated for only 5 weeks (P < 0.01). Dexamethasone also was effective in reversing regression later in the postoperative course. Eyes with preoperative myopia up to 4.90 D had significantly better refractive results at 12 months than eyes with myopia ranging from 5.00 to 7.50 D (P < 0.01). CONCLUSION: These data show that excimer laser PRK can correct myopia with good predictability. Results at 12 and 15 months tend to suggest stability of postoperative refraction. Regression of effect was more common in higher myopes. Topical steroids postoperatively seem to play a crucial role for the refractive result.

Adult↗
PubMed1993

[Stability of refraction 18 months after photorefractive keratectomy with excimer laser].

One-hundred-fourty-eight normal, sighted eyes, treated for myopia with argon fluoride 193-mm excimer laser, were analyzed 18 months postoperatively with respect to stability of refraction. Mean refraction 18 months after surgery was -0.32 D (+/- SD 0.89), a figure which was not significantly different from mean refractions at 12 and 15 months postoperatively. Also at 18 months, 86% of the eyes had an uncorrected visual acuity > or = 20/40, and 82% of the eyes were within 1.00 D of intended refraction (i.e. emmetropia). These percentages, which are directly related to postoperative refraction, are similar to those noted at 12 months after surgery. Although it may be too early to conclude that the 18-month refractions represent a definitive predictor of future refraction, the numerous similarities between the 12- and 18-months data presented in this study tend to suggest stability of refraction 18 months after excimer laser photorefractive keratectomy for myopia.

Adult↗
PubMed1993

Steroid treatment of myopic regression: acute refractive and topographic changes in excimer photorefractive keratectomy patients.

We documented acute changes in corneal topography and refraction after readministration of topical steroids in five patients with myopic regression after photorefractive keratectomy (PRK). One was a high myope (-10.00 sphere); the others were moderate myopes (preoperative spherical equivalents -4.25 to -6). All patients had been off steroids for 3 to 8 months before reinstitution. The changes in refractive spherical equivalents ranged from +0.75 to +3.00 diopters, and were observed from 6 days to 4 weeks later. Refractive hyperopic shifts were accompanied by pronounced corneal flattening as measured by computer-assisted corneal topographic analysis. Two to seven months later, three patients have become even less myopic, and two patients have again become slightly more myopic. Topical steroid use can modulate refractive changes after excimer laser treatments in some patients.

Adult↗
PubMed1993

Influence of target direction, luminance and velocity on monocular horizontal optokinetic nystagmus.

The present investigation demonstrates that the slow phase of human monocular horizontal optokinetic nystagmus (OKN) stimulated during scotopic vision does not depend on target direction but does depend on target luminance and velocity. OKN was elicited by a horizontally moving vertical grating projected inside a modified Goldman's perimeter hemisphere. Each of six target velocities (20, 40, 60, 80, 100 and 120 deg/s) were tested on each subject with step-wise increased target luminance. Eye movement was recorded by DC EOG. Both right and left target directions were tested. It was found that there is no directional preference in OKN gain (slow phase velocity/stimulus velocity). For the target velocities 20-80 deg/s, OKN gain increases with increasing target luminance with an exponential decline. The exponential luminance constant increases as target velocity increases. The maximum OKN gain decreases as target velocity increases. The threshold luminance needed to initiate OKN increases with increasing target velocity. A linear relationship was found between OKN gain and target luminance for the target velocities 100 deg/s and 120 deg/s.

Adult↗
PubMed1993

Measurement of visual readaptation time after flash exposure using optokinetic nystagmus.

It is concluded that measurement of visual readaptation time (RAT) using optokinetic nystagmus (OKN) is a repeatable measure of visual recovery after flash exposure. The semi-automatic method for measurement of RAT used here requires further development, but it is anticipated that the improved method will provide an efficient tool for increased understanding of the physiology of flash blindness. In this study on humans, it was found that if RAT is recorded twice on the same occasion, the second RAT is shorter. However, there was no systematic difference between RAT recordings on consecutive occasions. The newly developed semi-automatic method was found to provide RATs comparable to those obtained by manual measurement on a paper print out of EOG recordings. In RAT estimation, the variability between subjects shadows other sources of random variability. The least number of subjects needed in each group to detect a 20% alteration of RAT due to an experimental factor (alpha = 0.05, beta = 0.05) was estimated to 13 with independent groups design. For paired design < 10 are needed. OKN was elicited with a horizontally moving vertical grating. The eye movement was recorded by DC EOG. A sudden flash of green light temporarily abolished the OKN. The internal between the flash and the reappearance of OKN was measured as the RAT.

Adaptation, Ocular↗
PubMed1992

[Para-trochlear chondroma of the orbit].

We report on a 19-year-old male patient who was operated on for an orbital tumor close to the trochlea. The microscopical examination showed a cartilaginous tumor classified as differentiation grade II. Because of the close topographic location to the trochlea the tumor is characterized as a chondroma. Its rare location does not give us any further information concerning the final dignity. Benign cartilaginous tumors of the orbital trochlea region are extremely uncommon.

Adult↗
PubMed1990

Effect of spectral flash on readaptation time.

The effects of an adapting flash of different colors on human vision were investigated with various flashes and target luminances. The readaptation time (RAT) was measured using optokinetic nystagmus elicited by a projected moving striped pattern in a hemisphere. The RATs were recorded from 26 subjects with a multichannel pen recorder. Two target luminances (1.1 X 10(-5) cd/m2 and 2.6 X 10(-5) cd/m2) and 12 flash wavelengths (449 nm, 456 nm, 468 nm, 477 nm, 498 nm, 502 nm, 520 nm, 565 nm, 580 nm, 591 nm, 622 nm, and 703 nm) were used. A spectral RAT curve was obtained, which showed that the chromatic response of RAT follows this order: green greater than blue greater than yellow greater than red. A larger influence of the variation of the target luminance on the RAT was demonstrated at shorter wavelengths. The results also showed that the energy density of the flash has a larger variation with the RAT in blue and green than in red.

Adaptation, Ocular↗
PubMed1989

Preliminary notes on vulnerability of the retina to injury from peripheral laser exposure conditions.

If laser exposures to the periphery of the retina from low-energy lasers cause a hemorrhage obscuring the optical pathway to the fovea, resulting in loss of visual function, the risks for soldiers on the battlefield may be greater than previously expected. Two off-axis experiments were undertaken to obtain an indication of the hazards involved in exposing the peripheral retina to visible laser irradiation. Both off-axis exposures caused immediate vitreal hemorrhages in the periphery. After 80 min, the hemorrhage in the first eye had diminished, and in the other it was significantly smaller than immediately after exposure; even the central hemorrhage was smaller. Another observation after 120 min revealed the same result. These results indicate that an obvious risk exists on the battlefield for peripheral hemorrhages due to lasers operating within the retinal hazard spectrum. However, it is necessary to make more observations to establish the findings firmly.

Animals↗
PubMed1989

Vulnerability of the retina to injury from a military ruby rangefinder at battlefield distances.

This study investigates the possibility of causing a vitreal hemorrhage with a standard ruby rangefinder at battlefield engagement distances when the laser is observed with the naked eye or through magnifying optics or filters. The experiments were undertaken on the eyes of anesthetized pigs. The pigs were anesthetized with Mebumal and given 0.5% thropicamid in the eyes. They were then exposed to the radiation from a standard military ruby rangefinder (pulsewidth 25 ns, pulse energy 180 mJ). The rangefinder was aligned with a He-Ne laser and a beamsplitter. Eight experiments were performed, each with several exposures. The range was varied from 0.5-850 m. Some of the experiments were made using the naked eye, some with a filter, some with binoculars (7 x 50) and some with a combination of filter and binoculars. The pulse energy was varied from 91-6500 muJ. Vitreal hemorrhages were caused at distances of 410 and 850 m when a pair of binoculars (7 x 50) was placed in front of the eyes. The intraocular energy varied between 1500 and 4400 microJ. Results indicate that there is a possibility of causing a vitreal hemorrhage in a soldier who is using standard field binoculars and looking in the direction of an ordinary military rangefinder at distances at least up to 850 m.

Animals↗
PubMed1987

Collagen distribution in the lamina cribrosa and the trabecular meshwork of the human eye.

Tengroth and Ammitzböll found the collagen content of the optic disc in glaucoma to differ from that of normal eyes. A theory was advanced that a primary collagen disturbance might be involved in the pathogenesis of glaucoma. The connective tissue in the body has a supportive function in almost all the organs. The tensile strength and elasticity of connective tissue is mainly due to the presence of collagen fibres and elastic fibres, which also maintain the shape of the tissues. There are many different types of collagen, three of which are discussed in this paper. Type I collagen is found in tendons, skin, and numerous other organs, for example the eye. Type III is found mainly in the blood vessels but is also present in other tissues with a mesodermal origin, and type IV is found in the basement membranes. To elucidate the precise distribution of collagen types in the ocular structures an immunhistochemical study was undertaken in normal human eyes. The amino acids proline, hydroxyproline, and hydroxylysine, which are characteristic of collagen, were also analysed. Collagen types I, III, and IV were found in the lamina cribrosa, the trabecular meshwork, and the retrolaminary optic nerve. In contrast, only type I was found in the sclera.

Collagen↗