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PubMed1996

Retinal slip neurons in the nucleus of the optic tract and dorsal terminal nucleus in cats with congenital strabismus.

1. Visual response properties of neurons in the nucleus of the optic tract (NOT) and dorsal terminal nucleus of the accessory optic tract (DTN) were electrophysiologically investigated in five congenitally strabismic cats and compared with normal adult cats and 3- to 4-wk-old kittens. 2. As in normal cats, NOT-DTN cells of strabismic cats preferred horizontal ipsiversive stimulus movement. However, NOT-DTN neurons in strabismic cats altered their activity to a lesser amount per degree change of stimulus direction than do normal adult cats. In addition, NOT-DTN cells in strabismic cats exhibited a broader directional tuning, i.e., they increase their activity to a broader range of directions than control NOT-DTN cells. 3. Spontaneous activity and activity difference between preferred and nonpreferred direction were significantly lower in NOT-DTN neurons of strabismic cats than in normal adult cats and resembled that found in 3-wk-old kittens. Maximal stimulus-related activity was lower than in normal adult cats but higher than in kittens. 4. Visual latencies to onset of movement in the preferred direction were indistinguishable in strabismic and in normal adult cats. Visual latencies to onset of movement in the nonpreferred direction, however, were shorter in strabismic cats than in normal adult cats. 5. The average velocity tuning curve of NOT-DTN cells in strabismic cats was very flat without a well-defined optimal stimulus velocity. Thus it closely resembled data from 3-wk-old kittens. 6. Binocular convergence was significantly altered to a stronger dominance of the contralateral eye in NOT-DTN of strabismic cats. This reduction of binocular neurons was less pronounced than in cats with artificially induced strabismus or in 3-wk-old kittens. 7. In conclusion, the data presented here for retinal slip neurons in the NOT-DTN of strabismic cats closely resemble those from 3-wk-old kittens where no functional cortical input to the NOT-DTN is present. However, the elevated stimulus-driven activity and the still relatively high degree of binocularity give a clear indication of a functional, albeit weak and abnormal, cortical input to the NOT-DTN in these naturally strabismic cats.

Animals↗
PubMed1993

Intraoperative suspension-recession technique for treatment of vertical strabismus in thyroid myopathy.

Ten patients underwent extraocular muscle surgery with an intraoperative suspension-recession technique for diplopia induced by vertical strabismus in thyroid myopathy. The average ratio of the reduction of vertical deviation to the amount of surgery was 1.8 degrees/mm (range, 1.0 degrees/mm-2.8 degrees/mm). Eight (80%) patients had single binocular vision restored in the primary position without prism or compensatory torticollis after surgery. One patient who showed evidence of abnormal thyroid function at surgery developed an overcorrection postoperatively.

Adult↗
PubMed1994

Effect of posterior fixation sutures on the accommodative element of partially accommodative strabismus.

In a prospective study, we investigated the effect of posterior fixation sutures on the accommodative element of partially accommodative strabismus. Twenty patients were included in the study. Recession of one or both medial rectus muscles combined with bilateral posterior fixation sutures was performed on each patient. The results showed that this combined operation had a greater effect on the angle without glasses at both distance and near fixation, but not enough to eliminate the angle without glasses in all the cases. The results in patients with convergence excess are not satisfactory, as far as the reduction of the angle without glasses is concerned. In patients without convergence excess, this operation is effective in satisfactorily reducing the squint without glasses when the difference of the angle with and without glasses does not exceed 15 delta.

Accommodation, Ocular↗
PubMed1996

Strabismus surgery in ocular myasthenia gravis.

We evaluated the efficacy of eye muscle surgery in 4 patients with ocular myasthenia gravis with troublesome diplopia. All patients were in remission and had shown a consistently stable angle of deviation for at least 6 months preoperatively. The extent of eye muscle surgery was based on the degree of deviation in the primary position, and conventional recession and resection procedures were performed in 3 patients and hang-loose recession with an adjustable recession in 1. Single binocular vision was obtained in 3 patients in the primary position without prism correction or compensatory head posture. Electron-microscopic studies on the eye muscle specimens obtained at strabismus surgery revealed non-specific degenerative findings for the muscle fibers and sarcomeric disorganization compared to that in a control extraocular muscle.

Adolescent↗
PubMed2003

Identification of infants with significant refractive error and strabismus in a population screening program using noncycloplegic videorefraction and orthoptic examination.

PURPOSE: The second Cambridge Infant Vision Screening Program examined whether screening for accommodative errors by using videorefraction without cycloplegia could effectively serve as a first stage of screening for refractive errors, measured by standard cycloplegic retinoscopy. The screening also included an orthoptic examination for detection of strabismus. METHODS: All infants born in the Cambridge (UK) Health District, over a 2-year period, were invited for screening. Of those 5142 (76%) with mean age 8.1 +/- 0.8 months (SD) attended and received noncycloplegic videorefraction and an orthoptic examination. All those with a focusing error or orthoptic problem, as well as a randomly selected sample of visually normal control subjects, were invited to follow-up a month later for cycloplegic retinoscopy, repeat noncycloplegic videorefraction and orthoptic examination. RESULTS: Of the 5142 screened, 514 had a focusing error or orthoptic problem (positives). Four hundred thirty-nine of these and 284 visually normal control subjects (negatives) attended follow-up. A refractive or orthoptic condition was confirmed in 59.0% of the positive cases, whereas infants in 96.8% of the negative cases were confirmed normal. Adjusting for the proportions of the population represented by those infants seen at follow-up, sensitivity for the screening procedure was calculated at 0.67 and specificity at 0.96. Detailed results are presented in terms of the different conditions detected at screening (far, near, and anisometropic focus and orthoptic error), distribution of greatest axes at screening, and a comparison of initial videorefraction with repeat videorefraction and cycloplegic retinoscopy. CONCLUSIONS: A noncycloplegic screening procedure, simpler to perform than cycloplegic screening, succeeded in detecting a large proportion of infants with significant ametropia, particularly those with significant hyperopia, which is considered to be a strabismogenic and amblyogenic risk factor.

Accommodation, Ocular↗
PubMed2006

Polytetrafluoroethylene/polylactide-co-glycolide laminate containing dexamethasone allows delayed adjustable strabismus surgery in a rabbit model.

PURPOSE: To determine the usefulness of polytetrafluoroethylene/polylactide-co-glycolide (PTFE/PLGA) laminate containing dexamethasone in delayed adjustable strabismus surgery. METHODS: A prospective, masked-observer, controlled study was performed in rabbits. Fifty-two rabbit eyes were divided into three groups. After a recession of the superior rectus muscle (SRM), a PTFE/PLGA containing or not containing dexamethasone or balanced saline solution was applied beneath and over the SRM in the three treatment groups: the PTFE/PLGA-dexamethasone group (the P-D group), the PTFE group (the P group), and the control group (group C). Delayed adjustment was performed once on each SRM at 3 or 5 weeks after surgery by a masked observer. Adjustment lengths, the forces required, and degrees of adhesions were evaluated. RESULTS: In the control group, adjustment was possible in no eyes at 3 or 5 weeks after surgery. In group P, adjustment was possible in 6 of 10 eyes at 3 weeks after surgery and in 4 of 9 eyes at 5 weeks after surgery. In group P-D, adjustment was possible in 7 of 9 eyes at 3 and 5 weeks after surgery. CONCLUSIONS: PTFE/PLGA containing dexamethasone was found to allow delayed adjustment in most eyes for up to 5 weeks after surgery without instillation of anti-inflammatory agent.

Animals↗
PubMed1995

A double-blind randomized prospective study comparing ondansetron with droperidol in the prevention of emesis following strabismus surgery.

A prospective double-blind study was conducted to compare the anti-emetic efficacy of ondansetron and droperidol in preventing postoperative emesis following strabismus surgery. A sample size of 213 patients was divided into three equal groups to receive ondansetron 150 micrograms/kg (Group A), ondansetron 75 micrograms/kg (Group B), or droperidol 75 micrograms/kg (Group C). All patients received a standardized anaesthetic technique. All episodes of emesis, recovery time, and time to tolerating oral fluids were recorded. The incidence of emesis during 24 hours was Groups A and B 19.7%, and Group C 28.2%. The lower incidence of emesis recorded by the ondansetron groups compared with the droperidol group was not statistically significant. Ondansetron at 75 micrograms/kg was as effective as 150 micrograms/kg in reducing emesis when compared with droperidol. Mean time to discharge from the recovery room was 75.3 minutes (Group A), 44.4 minutes (Group B), and 41.0 minutes (Group C). The mean time to tolerating oral fluids was 356.5 minutes (Group A), 402.8 minutes (Group B), and 378.1 minutes (Group C). There was no statistical difference in discharge times from recovery or time to tolerating oral fluids in any of the three groups.

Adult↗
PubMed1993

Abnormal motoric laterality in strabismus and a hypothesis concerning its neurological origins.

A survey of the literature concerning motoric laterality in strabismus was undertaken. The assessment of manual and ocular dominance was based on a total of eleven studies conducted between 1934 and 1986. The average percentage of right-handedness in strabismics was 73.8%, whereas the average percentage of right-eyedness was 46.9%. Both figures are significantly lower than those obtained for the normal population. It is hypothesized that reduced right dominance in strabismics results from dysfunction of the otoliths and/or their higher brainstem pathways.

Brain Diseases↗
PubMed1999

Prediction of oculocardiac reflex in strabismus surgery using neural networks.

Successfully predicting an oculocardiac reflex (OCR) is difficult to achieve despite various proposed maneuvers. The aim of this study was to test the models built up by neural networks to predict the occurrence of OCR during strabismus surgery in children. Premedication was not given. Atropine 0.01 mg/kg was medicated just before induction. Induction was performed with fentanyl or ketorolac, followed by propofol. Atracurium or vecuronium was given for intubation. Anesthesia was maintained with O2-N2O with continuous propofol infusion. Chi-square test was performed for induction agents, gender, weight, muscle blockade, repaired muscle, number of repaired muscles, duration of operation to detect any association between the occurrence of OCR and to develop the model of neural networks. The multi-layer perceptron, radial basis function and Bayesian backpropagation network were tested. The occurrence of OCR was significantly associated with gender and repaired muscle (p < 0.05). Gender, repaired muscle and age were considered as input for the multi-layer perceptron, radial basis function and Bayesian backpropagation network. Three neural networks had predicted the same correction rate in the occurrence of OCR as being 87.5% overall among 16 patients' records tested. These models are conceptually different in predicting compared to conventional maneuvers, and have the advantage of testing individually and foretelling the propensity. By comparison neural networks use grouped experiential data and predict OCR by the learning rule. Neural networks require a relatively abundant number of experienced and homogenous patients' records to establish an accurate model. The multi-layer perceptron, radial basis function and Bayesian backpropagation modeling network may be an alternative way, and preferable to vagal tone maneuvers if the associated relationships to the occurrence of OCR are more clearly defined.

Adolescent↗
PubMedDate not supplied

Restrictions in the diagnoses and management of strabismus problems.

Restrictions have been found to be a common cause of incomitant strabismus and limitation of ocular rotations. Different types of restrictions have been described and the technique of forced duction testing reviewed. Causes of restriction include endocrine eye disease, orbital floor and medical wall fracture, Brown's syndrome, tight lateral rectus syndrome, congenital tight muscles, scarring, muscle contracture, and orbital celluitis or tumors. The importance of recognizing restrictions in the management of these problems has been emphasized.

Adolescent↗
PubMedDate not supplied

Prisms in strabismus management past, present, and future.

Given the optical properties of prisms, using them in strabismus treatment seems logical. However, theory and practice are two different things and the published literature in the field abounds in fruitless attempts at prismotherapy. This is because one is not only dealing with optical factors but also with sensory, motor, and accomodative factors. One must also remember that the act of binocular vision is a perceptual phenomenon.

Humans↗
PubMedDate not supplied

Antiemetic effectiveness of intraoperatively administered droperidol in pediatric strabismus outpatient surgery--preliminary report of a controlled study.

Low doses (0.05 mg/kg) of intravenously administered droperidol were given intraoperatively to randomly assigned pediatric strabismus patients in a controlled double-masked paradigm. No difference between control and treatment groups in the severity of vomiting was noted in the postanesthesia recovery room, but such a difference was probably present in the hospital rooms during the interval between room arrival and the meeting of hospital discharge criteria. Administration of the drug did not appear to produce somnolence sufficient to delay postoperative recovery.

Adolescent↗
PubMedDate not supplied

Studies of strabismus and amblyopia in infant monkeys.

Longitudinal studies of grating acuity have been conducted with strabismic infant monkeys. Representative data from several different monkey models of strabismus are presented. Acuity in the fixating eyes of these monkeys developed to adult levels similarly to acuity development in normal infant monkeys. Acuity in the non-fixating eyes often lagged behind, and in some cases never reached normal levels, resulting in a permanent amblyopia.

Age Factors↗
PubMedDate not supplied

Stuttering as a complication of strabismus surgery.

Children may experience extremely high levels of psychological stress in the operating suite because of anxiety associated with the separation from their parents, the unfamiliar and intimidating environment, the presence of strangers in unusual attire (masks, caps, gowns), the act of being forcibly restrained, and the forceful pressing over the mouth and nose of an anesthetic mask which emits a foul-smelling gas and which seems to restrict breathing in a manner reminiscent of suffocation. High levels of anxiety can lead to regression in a child's mental development, including stuttering, which is a regression to an earlier speech pattern and failure to develop fluent speech. Two cases are reported in which children developed stuttering following inappropriate or abusive treatment by the anesthesia departments of the hospitals in which they had surgery for strabismus. Both patients were four-year-old boys.

Anxiety, Separation↗
PubMedDate not supplied

Intraocular pressure variation during strabismus surgery.

The changes in IOP during strabismus surgery were studied in 40 patients. In most, 37 eyes, there was a marked decrease of IOP during surgery and rapid return to initial levels of IOP. In 13 out of 14 eyes that underwent bilateral surgery, the IOP in the first operated eye returned to about baseline levels by the end of surgery on the second eye. No correlation was found between the changes in IOP and: the type of surgery, the operated muscles, the duration of surgery and anesthesia, or the patients' age. We surmise that the decrease of IOP is probably associated with the intensity of the massage of the globe during the surgery.

Adolescent↗
PubMedDate not supplied

Computer-assisted diagnosis of strabismus.

A program for use on a microcomputer was developed to assist in the diagnosis of strabismus. The matrix consists of 41 separate disorders and 59 facts (history and examination findings). The facts are answered in a yes/no format. The relationship between the fact and the disorder is weighted as to whether the fact is always present, usually present, sometimes present, not related, unlikely to be present, not usually present, or never present. The computer makes the diagnosis (or diagnoses) indicating the most likely disorder when several are possible from the information given. Over 300 patient files were tested with the program. Of the last 50 records reviewed (70 disorders), the computer diagnosis agreed with the clinical diagnosis in 91% of the cases. Continued refinement of the program should be able to improve this accuracy.

Diagnosis, Computer-Assisted↗