Search PubMed⌕ Search

Biomedical subjects

A B Scott

Publications and source records attributed to A B Scott.

At least 37 records · Page 2Linked to original sources
PubMed1985

Botulinum A toxin injection as a treatment for blepharospasm.

Thirty-nine patients with blepharospasm were treated with injections of botulinum A toxin into the lid and brow. The maximum number of injections in one patient was 16 over a period of 24 months. A reduction of abnormal movement occurred in all patients, lasting up to 170 days. Both the amount and the duration of effect were dose dependent. Reinjection for recurrence had effects similar to the original injection. Tearing, dry-eye symptoms, or transient ptosis occurred in 20% of injections, especially in patients who had had previous eyelid surgery.

Blepharospasm↗
PubMed1985

Botulinum toxin injection in the management of lateral rectus paresis.

Seventeen patients with lateral rectus paresis (3 bilateral) were treated by injection of botulinum toxin to the antagonist medial rectus to eliminate its unopposed action or to eliminate its contracture. This allowed maintenance of single binocular vision in most patients while waiting for the palsy to heal, especially important in two children. It allowed avoidance of surgery in some cases, and a reduction or elimination of medial rectus surgery when later intervention was needed for persistent paralysis. The release of medial rectus shortening and stiffness (contracture) after just a few days of denervation was unexpected. This implies an internal muscular mechanism of contracture, perhaps sarcomere overlap, different from the fibrotic changes found in muscles after inflammation or trauma. These results also provide a rationale for experimental denervation treatment of contracture in limb muscle disorders.

Adolescent↗
PubMed1984

Injection treatment of endocrine orbital myopathy.

Eight patients with endocrine orbital myopathy received botulinum toxin injection of extraocular muscles for strabismus or injections of the levator for lid retraction. Strabismus of 25 prism diopters or less, especially during early stages of eye muscle involvement, responded well to injection with realignment and, probably, with avoidance of fixed muscle shortening. Long-standing strabismus, large angles, and lid retraction responded less well.

Adult↗
PubMed1983

Clinical and subclinical oculomotor findings in the Eaton-Lambert syndrome.

Five patients with the Eaton-Lambert syndrome were examined neuro-ophthalmologically. Three were studied using electro-oculographic saccadic velocity recordings. Four complained of blurred vision and all complained of ptosis during the course of their disease. Clinical examination revealed mild ptosis in three of the five patients. Saccadic velocities before exercise were normal. After saccadic exercise, an increase in velocity of up to 40% was noted in two of the three patients studied.

Aged↗
PubMed1982

Diagnostic injection of Xylocaine into extraocular muscles.

In situations where it is unclear which extraocular muscle is causing anomalous eye movement or to what extent one of two muscles is responsible, temporary paralysis of the muscle with Xylocaine may provide the answer. The procedure is to inject 0.2 to 0.5 cc 2% Xylocaine directly into the muscle using electromyography (EMG) for precise localization, a technique similar to that of therapeutic injections of botulinum toxin (Oculinum). The procedure is especially useful for Duane's syndrome, superior oblique palsy, and other situations where abnormal muscle insertions or innervations make diagnosis of the muscle responsible for an eye movement anomaly difficult and surgery unpredictable.

Adolescent↗
PubMed1981

Botulinum toxin injection of eye muscles to correct strabismus.

One hundred thirty-two doses of botulinum A toxin were injected into 42 humans. The effect on horizontal strabismus was uniformly beneficial, and effect lasting up to 411 days since the last injection was documented. The effect in vertical strabismus and lid retraction was beneficial, but less strongly so. No systemic effect or local complications were encountered except for effect on adjacent muscles. The drug appears to be a safe and useful therapy for strabismus.

Absorption↗
PubMed1981

Extraocular muscle forces in normal human subjects.

Actively developed horizontal muscle forces and tissue stiffnesses were measured in 29 normal orthophoric volunteer subjects (18 to 33 years old) by means of noninvasive length-tension forceps. Mean active fixation force developed at 50 deg extreme gaze was 26% greater for the medial rectus (74.8 gm) than for the lateral rectus (59.1 gm). The variation of maximum active force among individuals was 2:1 (48 to 103 gm). These muscles developed up to 25% of their maximum active force out of their field of action. Active (counter) hysteresis force differences of over 10 gm were measured between nasal and temporal gaze directions. This study suggests that a muscle which develops a maximum active force of less than 45 gm would be suspect as paretic. Variations from the normal pattern of reciprocal innervation, reflected in the graded active force of individual muscle contraction, may help in understanding some types of oculomotor pathology. The mean tissue stiffness-restraining movement of the globe in the nasal direction (1.05 gm/deg) is 11% greater than in the temporal direction (0.94 gm/deg). This is consistent with a stronger medial rectus balanced by a greater load. Variation of stiffness of 2:1 was observed among individuals; 0.8 to 1.7 gm/deg pulling nasally and 0.77 to 1.2 gm/deg temporally. Passive hysteresis and viscous force differences of over 10 gm were observed between the passive forced pull and normal spring-return of the eye. Large stiffnesses may be normal if balanced by large active forces. Abrupt changes of the length-tension curve indicate the magnitude and location of restrictions.

Adolescent↗
PubMed1980

Botulinum toxin injection into extraocular muscles as an alternative to strabismus surgery.

Sixty-seven injections of botulinum. A toxin were given to patients for correction of strabismus. No systemic complications of any kind have occurred. The maximum time of paralysis occurs four to five days following the injection, and then gradually diminishes, depending on the dose. The maximum correction of strabismus has been 40 prism diopters. The maximum follow-up following injection is six months. Injection of botulinum A toxin into extraocular muscle to weaken the muscle appears to be a practical adjunct or alternative to surgical correction.

Acetylcholine↗
PubMed1975

Disinserted extraocular muscles.

In two patients, a muscle that slipped from the globe posteriorly created the clinical pattern of reduced rotation amplitude, reduced saccadic velocity, reduced active force, and increasing exophthalmos with gaze into the field of action of the muscle. The muscle was surgically identified by an electronic stimulator that caused the muscle to contract, thus allowing the surgeon to fell it pull on the forceps or see its traction on adjacent tissues.

Child↗
PubMed1975

Horizontal saccadic velocities in Duane's syndrome.

Horizontal ocular saccadic velocities were measured by electro-oculography in 33 patients with Duane's syndrome. In 28 patients with limited abduction associated with retraction on adduction (Type 1), abduction saccadic velocity was markedly reduced while adduct-on saccades were moderately slow. In three patients with exotropia and good abduction but associated limited adduction and retraction on adduction (Type 2), abduction velocity was good, while adduction saccadic speed was slow. In two patients with limited abduction and adduction with retraction on adduction (Type 3), abduction and adduction saccadic velocity was appreciably slow. Ocular electromyographic testing selected patients indicated that slow abduction saccades could be explained by absence of lateral rectus muscle recruitment, while slow adduction saccadic speed could be explained by paradoxical innervation of the lateral rectus muscle.

Duane Retraction Syndrome↗
PubMed1975

Muscle tension during unrestrained human eye movements.

1. Tensions in the horizontal rectus muscles have simultaneously and continuously been recorded during unrestricted eye movements in four strabismus patients, using force transducers small enough to be implanted in series between the tendons and their points of insertion on the globe. 2. Levels of tension required to maintain fixation at each position of gaze vary from a minimum of 8-12 g approximately 15 degrees outside of muscle's field of action to a maximum of around 40 g at extreme gaze within the muscle's field of action. When tension is plotted as a function of eye position, the static locus of fixation tension levels exhibits a parabolic relationship. 3. Tensions recorded during smooth following movements parallel or slightly exceed those of fixation. 4. At the onset of a saccade, tension in the agonist rises isometrically, then, as the eye moves, tension levels parallel those of fixation but with an isotonic increment of 15-25 g. At the end of the saccadic movement, tension falls essentially isometrically to the new fixation level. 5. Tension in the antagonist reveals an unexpected peak at the onset of a saccade. 6. For saccadic movements tension increments of 15-25 g above the fixation levels suffice to move the eye rapidly to a new position of gaze, regardless of the duration of the saccade and the location of the new fixation point. 7. Maximum and minimum levels of tension during normal fixation, following and saccadic movements, plotted as a function of eye position, form an operational envelope which defines the limits of muscle forces during normal eye movements. The lowest level of this envelope is the parabolic static locus of fixation tensions.

Adult↗
PubMed1975

Quantitative guidelines for exotropia surgery.

The effect of numerous preoperative variables on the amount of surgical correction attained was assessed in a population of intermittent exotropic patients; 54 had bilateral recession surgery, 48 had recess resect surgery. By appropriate multivariate statistical analyses, about 95 per cent of the variance in results of surgery (expressed as change in deviation from preoperative to the postoperative time in prism diopters per millimeter of surgical correction) could be accounted for. A workable scheme for utilizing this data base to guide future surgery is presented in the form of quantitative formulae. In addition to this empirical derivation, insights are provided into the mechanics of ocular muscle operations and the maturation of the eye as it affects strabismus sergery. Expansion of this approach to a wider ranger of cases and to additional types of cases should result in a greater descriptive and surgical accuracy from strabismus surgery.

Adolescent↗