Biomedical subjects

J Weerheim

Publications and source records attributed to J Weerheim.

7 recordsLinked to original sources

PubMed2003

Follow-up after surgical closure of congenital ventricular septal defect.

OBJECTIVES: The purpose of this retrospective study was to assess long-term outcome of children after surgical closure of a ventricular septal defect (VSD). MATERIAL AND METHODS: Between January 1992 and December 2001 a consecutive series of 188 patients (100 females) were operated for closure of a VSD. Temporary tricuspid valve detachment (TVD) was applied in 46 patients (24%) to enhance exposure of the defect using transatrial approach. Pre-operative baseline characteristics showed that the detached group was younger (0.79+/-1.8 vs 2.1+/-3.5 years, p=0.002) and had a lower weight (6.5+/-6.4 vs 10.0+/-11.0 kg, p=0.009). RESULTS: There was no difference in cross-clamp time (temporary TVD 36.2+/-11.3 vs non-temporary TVD 33.6+/-13.1 min, p=0.228). Postoperative echocardiography showed that 67 patients (36%) had trivial/minimal regurgitation, 10 patients (22%) from the temporary TVD group vs 57 patients (40%) from the non-detached group (p=0.02). There was no tricuspid stenosis. Hospital mortality comprised two patients (1%). One patient died due to a pulmonary hypertensive crisis and one in relation to an acute patch dehiscence for which an emergency reoperation was necessary. At first postoperative echocardiography no shunting was detected in 113 patients, trivial shunting in 73 and significant shunting in none. Multivariate logistic regression analysis revealed that weight at operation was a predictive factor for the occurrence of residual shunting (OR 0.95, C.I. 0.91-0.99). One patient with conduction disturbances needed a permanent DDD-pacemaker. Three patients were lost to follow-up. Mean follow-up time was 2.6 years (range 0.1-9.4). During follow-up no reoperations were necessary for closing a residual VSD. One patient died 7 months postoperative due to a bronchopneumonia. During follow-up in 37 (51%) of the 73 patients the trivial shunting disappeared spontaneously at a median time of 3.9 years. According to actuarial analysis all trivial shunting had disappeared at 8.4 years. CONCLUSION: Trivial residual shunting disappeared spontaneously at a median follow-up time of 3.9 years. During follow-up no patient needed to be reoperated for residual VSD. TVD proved to be a safe method to enhance the exposure of a VSD.

Adolescent↗

PubMed1990

Effect of hydrogen peroxide, DL-propranolol, and prednisone on bovine lens optical function in culture.

Lens refractive function was monitored during long-term bovine lens culture experiments in which low concentrations of potentially damaging agents were added to the culture media. The agents tested were the drugs DL-propranolol and prednisone, and hydrogen peroxide. A computer-driven scanning laser system was used to monitor lens focal length during culture. The system consists of a scanning helium-neon laser beam, a television video camera, and a video frame digitizer. The system first locates the optical center of the lens, defined as the position of little or no refractive deviation of the beam. The laser scans the lens in small steps (0.05 mm), while the digitizer measures focal length for each beam position. A graphic profile of lens focal variation is plotted. A concentration of 0.1 mM hydrogen peroxide produces no significant change in lens focus after 315 hr of incubation. When the concentration is increased 10-fold (1.0 mM), lens focal ability is radically disturbed after 60 hr of incubation. Lenses incubated with prednisone (0.03 mM) for up to 525 hr show no difference in focal characteristics in comparison to control lenses. Propranolol in a concentration of 0.1 mM disrupts lens focal ability after 250 hr of incubation, whereas a higher concentration (1.0 mM) produces a similar effect after only 150 hr. These results indicate that lens refractive function is a sensitive measure of lens function during culture.

Animals↗

PubMed1989

The eye of the hooded seal, Cystophora cristata, in air and water.

Multiple refractive state measurements were made on a male and female hooded seal (Cystophora cristata) when the eyes were exposed to air and to water. The measures, made by conventional retinoscopy and by photorefraction, show that the seals are moderately hyperopic (2-3 diopters) in water and moderately myopic (2-4 diopters) in air. No significant astigmatism was noted in either medium. The absence of refractive state variation over time suggests that an accommodative mechanism is insignificant or absent, although histological study indicates that the ciliary muscle is well developed. Photokeratoscopy, carried out on two animals with two keratoscopic instruments, show that the cornea is relatively flat (30 mm, or about one-half the diameter of the eye). Furthermore the cornea is only slightly astigmatic (less than 1 diopter). The refractive power of the external corneal surface (in air), calculated from a measurement of corneal refractive index of 1.378, amounts to only 10 or 11 diopters. As in the typical fish eye, hooded seal lenses are spherical or nearly spherical in shape (24-23 mm), and have short focal lengths (30-32 mm). Focal measures for rays at varying distances from the lens center indicate that spherical aberration is well corrected. There is no indication in this seal species, of a previously reported adaptation involving a highly astigmatic cornea which together with a slit pupil can minimize the optical effect of movement from water to air.

Air↗

PubMed1989

Modelling cortical cataractogenesis. X. Evaluation of lens optical function by computer based image analysis using in vitro rat lens elevated glucose model.

As a model system rat lenses (Wistar) were isolated and cultured intact in medium M199 or M199 with 55 mM glucose. Glucose-stressed lenses developed opacities within 20 hours while control lenses remained clear. The comparative functionality of lenses was examined by two different video/computer-based imaging systems: one based on image analyses of laser light after transmission through the lens (Scanning Lens Monitor), and the other based on image analyses of the projection of white light transmitted through the lens (Kevex Image Analysis System). The combination of both methods detect changes in focal length and light scattering. On the basis of these results, these techniques can be used in animal studies for grading lenses by functional properties to complement morphologically based grading (slit-lamp) of cataracts provided by a veterinary pathologist.

Animals↗

PubMed1989

Optical constancy of the chick lens during pre- and post-hatching ocular development.

Embryonic and post-embryonic development of the ocular lens is associated with the continual production of new secondary lens fibers by the mitotic activity of equatorial epithelial cells. This continual development affects lens size and shape and refractive index distribution. Study of embryonic lens optical function has been largely ignored. The optical characteristics of the developing chick lens, including paraxial and eccentric focal lengths, were measured during the embryonic period of development and up to 15 days after hatching. Measurements were made with an automated scanning laser system in which the video image of a helium-neon laser beam refracted by an excised lens in solution is digitized. Focal length is measured for beams moving in small steps on either side of that center. Measurements were made on excised lenses as well as with the lens in situ within the anterior segment of the eye. The results, collected from a study of a total of 80 lenses, indicates that embryo lenses at 6-7 days of incubation have long and very variable focal lengths. At the tenth embryo day, focal length drops by more than one-half and focal variations, between lenses and for different beam positions within a single lens, is reduced. Further measures for 14- and 17-day embryo lenses, as well as for lenses from hatchling and 5-, 10- and 15-day-old chicks, indicate that there is little change in focal length, either paraxially or for eccentric beam positions.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1987

Experimentally induced myopia does not affect post-hatching development of the chick lens.

Myopia, as characterized by a large refractive error (e.g. -10.7 +/- 0.4 D), was induced in post-hatch chicks by a 14 day application of a goggle that was designed to blur the retinal image. In comparison to untreated eyes, the treated eye showed significant changes in wet eye weight and both axial and equatorial lengths. However, the lenses of myopic and non-myopic eyes were not significantly different in focal characteristics, light transmittance or total soluble protein content. Thus the lens neither contributes to, nor compensates for the large refractive error observed in experimentally induced myopia.

Animals↗

PubMed1986

Computer assisted scanning laser monitor of optical quality of the excised crystalline lens.

We describe a technique, involving the projection of low power laser beams through excised lenses in solution, that makes it possible to measure photographically lens optical aberrations. Preliminary work indicates that the laser method can be used in combination with lens culture experiments as a means of monitoring changes in studies of lens biology. The goal of this research is the development of an effective in vitro optical monitor of ocular lenses in order to assist the study of the biochemistry of lens aging and cataractogenesis and be used as a sensitive toxicity measuring device.

Aging↗