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Biomedical subjects

L J van Rijn

Publications and source records attributed to L J van Rijn.

7 recordsLinked to original sources
PubMed1998

Asymmetrical vertical phorias indicating dissociated vertical deviation in subjects with normal binocular vision.

We measured the symmetry of phoria angles in six normal subjects. Subjects were selected on the basis of good visual acuity and stereopsis, normal binocular eye alignment and, apart from mild refraction errors, absence of ocular abnormalities. They were instructed to look at a word on a reading chart at 2 m distance. Each measurement consisted of five subsequent intervals of 5 s duration. During these five intervals viewing was binocular, with the right eye only, binocular, with the left eye only, and binocular, respectively. Each experiment consisted of twelve measurements. Eye movements were measured with scleral coils suited for measuring in horizontal, vertical and torsional directions. Five out of six subjects displayed an asymmetrical vertical phoria; one subject showed an alternating hyperphoria; four displayed a left over right vertical phoria that was largest for left eye occlusion. Only one subject showed a symmetrical vertical phoria. Both the size of the vertical phorias and the size of the asymmetries in these vertical phorias were very small: on average 0.16 +/- 0.01 and 0.17 +/- 0.01 degree, respectively. The direction of the vertical phoria asymmetries (the largest left over right was found with left eye occlusion) and the fact that asymmetries were found more often in vertical than horizontal and torsional phorias suggest that these asymmetries are related to dissociated vertical deviation. These results suggest that dissociated vertical deviation, often observed in subjects with a disruption of binocular vision early in life, reflects the enhancement of a phenomenon that is present in normal subjects as well.

Adult↗
PubMed1995

Excess cyclovergence in patients with intermittent exotropia.

Recently, we developed a model of binocular fixation. This model predicts the amount of cyclovergence as a function of target elevation and horizontal target vergence. The prediction derives from the assumption that version and vergence add linearly and that the eye positions are constrained in three respects: (1) the foveae of the two eyes are directed towards the target, (2) the version component follows Listing's law, i.e. cycloversion, and horizontal and vertical version are not independent, (3) the vergence component is restricted to a plane approximately perpendicular to Listing's plane, i.e. horizontal, vertical and torsional vergence are not independent. The version and the vergence components are characterized by a common primary direction for the two eyes. We applied this model to data of patients with intermittent exotropia. In two patients with an amblyopic eye we found that the common primary direction rotates towards the amblyopic eye. In the third patient, not suffering from amblyopia, the common primary direction was practically straight ahead. In all three patients, cyclovergence angles were larger than those found in normal subjects. We found that the increased cyclovergence was compatible with our model for normal subjects if an offset on the horizontal vergence was given. This offset represents the additional convergence effort required in these patients to overcome the exodeviation of the eyes. According to our model the increased horizontal vergence effort results in excess cyclovergence. The relation between horizontal vergence and cyclovergence offers a new method for measuring the angle of exotropia.

Adult↗
PubMed1992

Visually induced cycloversion and cyclovergence.

Binocular cyclorotatory (torsional) eye movements in response to visual patterns, which oscillated sinusoidally in the frontal plane, were recorded with scleral induction coils in human subjects. Conjugate cycloversion and disjunctive cyclovergence were directly compared by in-phase and out-of-phase oscillation of the same pattern. Stimulus motion had a frequency of 0.2 Hz and amplitudes of 2-8 deg. Both response types had a similar and low gain (about 0.2 averaged over all subjects). Cycloversion showed no time lag, while cyclovergence lagged by about 600 msec. Non-fusible patterns were effective in eliciting cycloversion, but not cyclovergence. Apart from this, the nature of the pattern (randomly distributed dots, regular rows of dots, horizontal or vertical grating, Julesz stereogram or images with a pictorial significance) had only the slightest effect on the magnitude of the responses.

Adult↗
PubMed1987

Suprofen versus paracetamol after oral surgery.

A randomized double-blind trial was performed to evaluate efficacy and tolerability of suprofen 200 mg (Suprocil) in comparison to paracetamol 500 mg after surgical extraction of a wisdom tooth. The study lasted 4 days per patient at the longest. Pain intensity and pain relief were evaluated by the patients using a visual analog scale. A total of 59 patients took part in the study; of these, 30 were on suprofen and 29 on paracetamol. The 30-min pain relief with paracetamol was superior to that obtained with suprofen. Roughly, the 90-min pain relief scores were somewhat higher for suprofen than for paracetamol. However, none of the differences were statistically significant. No significant difference was seen between the 2 treatment groups with respect to the frequency of the number of capsules taken per day. Broadly, the efficacy was good or excellent in 18 patients in each group. With suprofen, there were 8 moderate results and 4 insufficient ones. With paracetamol, 6 results were moderate and 5 insufficient or worse. No significant differences between the 2 treatments was seen. Tolerability was rated good by all but 1 patient in each treatment group; with suprofen, 1 result was moderate, while with paracetamol, 1 result was poor. Adverse reactions occurred in 3 patients on suprofen and in 2 patients on paracetamol, though these reactions could not be related to the use of the drug itself.

Acetaminophen↗
PubMed1986

Experimental gingivitis and frequency of tooth brushing in the beagle dog model. Clinical findings.

The aim of this experiment was to study clinical parameters when 3 different frequencies of tooth brushing were applied to sites of experimental gingivitis in beagle dogs. 12 beagle dogs, at the start of the experiment 2 years of age, were used. After a thorough cleaning, the maxillary left and right first, second and third premolars were brushed daily for a period of 8 weeks. Subsequently, for 4 weeks, all brushing was omitted in order to establish an experimental gingivitis. After this pre-experimental period, the dogs were distributed into 3 groups of 4 dogs each: one group was brushed 7 times a week, a second was brushed 3 times a week and the third group was brushed only once a week. Brushing was carried out for 24 weeks, only on the right sides of the upper jaws, the left upper jaws serving as controls. At regular intervals, plaque index, gingival index and probing depths were assessed. A brushing effect was calculated for each dog, to include information on all within-dog and between-dog variations. The present study demonstrated that only by brushing every day can clinically healthy gingivae be obtained in the beagle dog model with experimental gingivitis at baseline. The state of gingival health at baseline may be used to determined the frequency of brushing necessary to create or maintain healthy gingivae.

Animals↗