PubMed Health⌕ Search

Biomedical subjects

W Cadera

Publications and source records attributed to W Cadera.

At least 19 recordsLinked to original sources
PubMed1997

A magnetic resonance imaging study of double elevator palsy.

OBJECTIVE: The pathophysiology of double elevator palsy is poorly understood. We assessed two patients with this condition using magnetic resonance imaging (MRI) to evaluate the appearance of the extraocular muscles. DESIGN: Cross-sectional study. SETTING: Radiology department of a university-affiliated hospital in London, Ont. PATIENTS: Two patients from a private ophthalmology practice who had undergone complete transpositions of the horizontal rectus muscles to treat hypotropia associated with double elevator palsy. INTERVENTION: MRI. A volume scanning technique was used to obtain maximum information about the muscles. OUTCOME MEASURE: Appearance of the extraocular muscles. RESULTS: In both patients MRI showed decreased volume of the superior rectus muscle on the affected side. The other rectus muscles were normal. This suggested either congenital hypoplasia or paresis of the involved superior rectus muscle. In addition, the full tendon transpositions of the medial and lateral recti did not appreciably change the middle and deep orbital pathways of the transposed horizontal rectus muscles. CONCLUSIONS: MRI may be a useful adjunct to saccadic velocity assessments in differentiating between primary inferior rectus restriction, primary superior rectus paresis and congenital supranuclear elevator deficiency.

Adolescent↗
PubMed1995

The 20-prism-dioptre base-out test: an indicator of peripheral binocularity.

OBJECTIVE: To assess the ability of the 20-prism-dioptre base-out test to detect the presence of peripheral fusion in children too young to undergo formal sensory testing. DESIGN: Case series. SETTING: Pediatric ophthalmology service at the Children's Hospital of Western Ontario, London. PATIENTS: Eighty orthophoric patients (mean age at presentation 19 months [range 4 to 50 months]) with a family history of strabismus or with a diagnosis of pseudostrabismus, blocked tear duct or chalazion, followed for an average of 36 (range 6 to 129) months, and 41 patients with surgically corrected infantile esotropia (mean age at testing with the 20-PD base-out test 21 months [range 9 to 50 months]), followed for an average of 53 (range 14 to 117) months. INTERVENTIONS: Twenty-PD base-out test and red-green Worth four-dot test at near (0.3 m). OUTCOME MEASURE: Presence of peripheral fusion. RESULTS: The 20-PD base-out test had a positive predictive value of 100% in detecting peripheral fusion in the orthophoric patients and 93% (95% confidence interval [CI] 82% to 100%) in the patients with surgically corrected infantile esotropia. CONCLUSIONS: Although the 20-PD base-out test had a negative predictive value of 21% (95% CI 0% to 43%), a positive response remains a useful indicator of peripheral binocular single vision in children too young to undergo more formal sensory testing.

Child, Preschool↗
PubMed1994

An animal model studying reconstruction techniques and histopathological changes in repair of canalicular lacerations.

We designed an animal model using sheep to evaluate three methods of canalicular reconstruction after laceration: direct sutured reapposition of the canaliculus without silicone intubation (4 eyelids), silicone intubation of the canalicular system without mucosal anastomosis (14 lids) and silicone intubation with mucosal anastomosis (10 lids). We also wished to determine the appropriate time of silicone tube removal. In the canaliculi repaired using silicone intubation the tubes were removed at 4, 8 or 12 weeks. Patency of the canalicular system was assessed at 16 weeks by probing. Sections of eyelid tissue were examined histopathologically to confirm patency and to compare the tissue alteration caused by the various methods of repair. We found that silicone intubation was necessary to reestablish patency of the canaliculus and that silicone intubation with and intubation without mucosal anastomosis were equally efficacious in restoring canalicular patency. The optimum time for removal of the tube was 12 weeks. Histopathologically, all canaliculi found to be patent by probing demonstrated mucosal continuity along the canalicular lumen.

Anastomosis, Surgical↗
PubMed1993

Natural history of presumed congenital Brown syndrome.

OBJECTIVE: To evaluate the stability of the ocular alignment in patients with presumed congenital Brown syndrome. DESIGN: A retrospective review of patients with Brown syndrome with an emphasis on nonsurgical cases. Follow-up of at least 1 year was required for inclusion in the study. SETTING: Patients were selected for this study from the pediatric ophthalmology services at the Ivey Institute of Ophthalmology, London, Ontario, and the Children's Hospital of Eastern Ontario, Ottawa. PATIENTS: A cohort of 71 patients with presumed congenital Brown syndrome. Two cases were bilateral. Eleven cases were excluded because of insufficient length of follow-up, leaving 60 patients with an average follow-up of 46 months. All patients were assessed and followed up by a pediatric ophthalmologist. RESULTS: Of 38 patients who had no hypotropia in primary position at presentation, only two (5%) patients experienced a worsening with the development of a small vertical strabismus during the follow-up period. Six (10%) of the entire group of 60 patients experienced a complete spontaneous resolution of the deficiency in elevation at 4, 6, 8, 10, 12, and 15 years of age. CONCLUSION: Among patients with congenital Brown syndrome, those who are orthotropic in the primary position tend to remain stable or improve over time without surgical intervention.

Child↗
PubMed1993

Successful treatment of hereditary trembling chin with botulinum toxin.

Hereditary trembling chin is an autosomal dominant condition characterized by recurrent bouts of tremor involving the chin. These episodes are precipitated by emotional upset. There has been considerable debate about the gravity of this condition. This may be a benign movement disorder; however, the rhythmic trembling of mentalis at rest or during times of stress in these patients is often misinterpreted as betraying an incipient emotional upset. For this reason, some patients with this condition may find it socially disabling. We have recently successfully treated one such family with regular botulinum toxin injections to the mentalis muscle.

Adult↗
PubMed1992

Rotation of Listing's plane during vergence.

When visually fixating targets on an isovergence surface, the position of each eye was constrained to a plane. Thus, Listing's law holds during vergence. The planes were, however, rotated temporally with respect to those when viewing distant targets. The effect of this rotation was to produce a torsion which depended on eye elevation; extorsion of the two eyes for downward gaze and intorsion for upward gaze. The saccadic velocity command was relatively unaffected during vergence. Computer simulations suggest that the saccadic tonic command and the vergence command interact multiplicatively in three dimensions.

Convergence, Ocular↗
PubMed1992

The conjugacy of human saccadic eye movements.

Binocular measurements of instantaneous velocity vectors in normal human subjects during saccades showed: (1) considerable trial to trial variation in peak velocity, saccade duration, and saccade curvature despite saccade accuracy; (2) variations in one eye were mirrored by similar variations in the other eye, with a high positive correlation. The high correlation between the peak velocities suggest that saccades in the two eyes are driven by a common saccade generator. Assuming that a local feedback loop guides saccades, the high correlation between saccade durations and between saccade curvatures suggests that both eyes are guided by common feedback. If so, monocular adaptation must occur downstream from the saccade generator.

Humans↗
PubMed1991

Generation of torsional and vertical eye position signals by the interstitial nucleus of Cajal.

The neural integrator, which converts eye velocity signals into position signals, is central to oculomotor theory. Similar integrators are probably necessary in any neural system that changes and maintains muscular tension. The integrator for horizontal eye position is in the pons, but the locations of the vertical and torsional integrators have not been clearly defined. Recording three-dimensional eye movements in alert monkeys during microstimulation and pharmacological inactivation of midbrain sites showed that the interstitial nucleus of Cajal generates both the torsional and vertical eye position signals. Up and down signals are linked with clockwise signals in the right brain and counterclockwise signals in the left brain. This three-dimensional coordinate system achieves orthogonality and bilateral symmetry without redundancy and optimizes energy efficiency for horizontal visual scanning.

Animals↗
PubMed1991

Cryotherapy for treatment of active retinopathy of prematurity: experience in London, Ontario.

Between January 1985 and May 1990, 49 infants (97 eyes) with stage 3 "plus" retinopathy of prematurity (ROP) were treated with cryopexy. The mean gestational age at birth was 29.6 weeks and the mean birth weight 753 g. At the time of treatment the mean chronologic age was 8.7 weeks and the mean weight 1629 g. Noncutting cryopexy was applied to the entire avascular peripheral retina, anterior to the mesenchymal ridge. Confluent treatment was done anteriorly to the posterior border of the pars plana. Favourable results, defined as a normal-appearing fundus (apart from the cryopexy scars) with no retinal folds or traction, were observed in 70% of the eyes an average of 13.8 (range 2 to 60) months after treatment. Our results emphasize the importance of early detection of ROP and diligent monitoring and treatment of affected infants.

Body Weight↗
PubMed1991

Factors associated with binocular single vision in microtropia/monofixation syndrome.

We reviewed the charts of 398 patients with microtropia/monofixation syndrome to determine what factors influence the level of binocularity attained. Most patients (82%) exhibited some degree of stereoacuity. Patients with a later age at presentation of the initial deviation were more likely to exhibit stereoacuity (p less than 0.001). Patients with smaller initial deviations were also more likely to exhibit stereoacuity (p = 0.016), as were those with smaller manifest deviations on final testing (p less than 0.001). Patients with amblyopia on final testing were less likely to demonstrate stereoacuity (p = 0.0001). Generally, the more intervention required in the form of optical or surgical correction, the poorer the level of binocularity.

Adolescent↗
PubMed1991

Treatment of blepharospasm and hemifacial spasm with botulinum A toxin: a Canadian multicentre study.

Botulinum A exotoxin was recently approved for use in Canada. We describe the efficacy of botulinum toxin in the management of 235 patients with blepharospasm (mean age 64.3 years) and 130 patients with hemifacial spasm (mean age 60.4 years) treated at three Canadian ophthalmologic centres between 1984 and 1989. A total of 98% of the patients with blepharospasm and 100% of the patients with hemifacial spasm had significant relief of their symptoms; however, 11% of the former and 2% of the latter did not respond to the usual starting concentrations of the drug and needed stronger dosages for relief. The duration of relief varied widely in both groups. Up to 7% of patients had ineffective treatments but responded to subsequent injections. Analysis of variance and linear trend statistics showed that there were no changes in the mean duration of relief over the first several treatments for individual patients in either group. Side effects were transient and included ptosis, exposure keratitis, epiphora and strabismus.

Adult↗
PubMed1990

Auditory function in Duane's retraction syndrome.

We obtained audiograms and auditory brainstem responses from 44 patients with Duane's retraction syndrome to assess the incidence and nature of hearing deficit. Of 44 patients, seven (15.9%) had evidence of hearing impairment. Three (6.8%) subjects had a temporary conductive hearing loss because of middle ear fluid, and another patient had hearing loss from Crouzon's disease. The remaining three (6.8%) patients demonstrated sensorineural hearing deficit. This hearing impairment was attributed to a cochlear lesion and not to a pontine lesion. We believe that the frequency of sensorineural hearing loss in these patients warrants hearing screening programs similar to those used for infants in neonatal intensive care units.

Adolescent↗
PubMed1990

Computing three-dimensional eye position quaternions and eye velocity from search coil signals.

The four-component rotational operators called quaternions, which represent eye rotations in terms of their axes and angles, have several advantages over other representations of eye position (such as Fick coordinates): they provide easy computations, symmetry, a simple form for Listing's law, and useful three-dimensional plots of eye movements. In this paper we present algorithms for computing eye position quaternions and eye angular velocity (not the derivative of position in three dimensions) from two search coils (not necessarily orthogonal) on one eye in two or three magnetic fields, and for locating primary position using quaternions. We show how differentiation of eye position signals yields poor estimates of all three components of eye velocity.

Adult↗
PubMed1990

Topical 2.5% and 5% phenylephrine: comparison of effects on heart rate and blood pressure.

We compared the effects of 2.5% and 5% concentrations of topical ocular phenylephrine hydrochloride on blood pressure and heart rate in 200 adult patients undergoing extracapsular cataract surgery under either general or neuroleptic anesthesia. Although there was little initial change in mean systolic or diastolic blood pressure in either group, once anesthesia was induced there was a rise of 1 to 5 mm Hg in the lower-dose group, compared with 17 to 26 mm Hg in the higher-dose group. A slight decrease in mean heart rate of 5 to 6 beats/min was noted immediately after the instillation of either the 2.5% or 5% solution. The results suggest that lower doses of topical phenylephrine are safer than higher doses when used preoperatively. This may be particularly significant in hypertensive patients, who have higher baseline blood pressure.

Administration, Topical↗
PubMed1989

Vertical congenital ocular motor apraxia.

The authors describe a case of vertical congenital ocular motor apraxia (COMA). The pathways of vertical saccades and pursuits are briefly outlined, and a possible cause of vertical COMA is suggested. A neuropathological correlate is needed to confirm the cause of both vertical and horizontal ocular motor apraxia.

Apraxias↗
PubMed1989

Duane's retraction syndrome: southwestern Ontario experience.

We describe the clinical ocular and medical manifestations in 71 patients with Duane's retraction syndrome. We compare our results to those of recent studies, with special focus on the prevalence of anisometropia and amblyopia, found in 14% and 17% respectively.

Adolescent↗
PubMed1988

Comparison of 0.5% cyclopentolate plus 0.5% tropicamide and 1% cyclopentolate alone for mydriasis of dark irides.

We studied the mydriatic and cycloplegic effect of a single dose of a combination of 0.5% cyclopentolate hydrochloride and 0.5% tropicamide in 20 healthy subjects with dark brown irides. The mean change in dilatation with the combination drop was 3.5 mm, compared with 0.6 mm with 1% cyclopentolate alone (p less than 0.001). In 92% of 26 eyes studied the difference in refraction between the combination drop and 1% atropine was +1.00 dioptre or less. The combination drop safely provided satisfactory mydriasis and cycloplegia in 20 minutes, allowing for rapid and accurate examination of these patients.

Atropine↗