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Optometric therapy of divergence excess strabismus.

A review and analysis of the vision-training procedures were carried out over a period of 2 years at State University of New York (SUNY), University Optometric Center by 20 staff optometrists on 28 patients exhibiting divergence excess strabismus using models proposed by Flax and Greene. Training included motility, accommodative rock, fusion, antisuppression, and stereoscopic skills by a variety of techniques and devices. Patients who exhibited smaller pretraining angles of deviation, increased maturity, and greater motivation responded most successfully to treatment. The results achieved in this study compare favorably with those obtained by traditional orthoptic procedures.

Adaptation, Ocular↗

Paralytic strabismus.

This review of the year's literature on paralytic strabismus contains some especially interesting contributions on epidemiology of ischemic ocular motor palsies, new imaging diagnostic techniques in sixth and fourth nerve palsy and in Graves' ophthalmopathy, and bilateral histological findings in one case of clinically monolateral Duane's retraction syndrome. Some reports concern the reliability of diagnostic tests routinely used for measuring cyclotorsion in superior oblique palsies.

Brain↗

Paralytic and incomitant strabismus.

In the year under review, published work has concentrated on two main topics. The first is the etiology, pathophysiology, and natural history of paralytic and incomitant strabismus. No major studies were published but some interesting findings are discussed. The second is surgical results, largely assessed by uncontrolled retrospective data analysis. Also, a number of useful tips for patient management have emerged.

Cranial Nerve Diseases↗

Retinal complications of strabismus surgery.

The frequency of inadvertent retinal perforation during routine strabismus surgery has been debated, as patients with such complications are usually asymptomatic. Recent prospective clinical studies indicate a retinal perforation rate of 0.4 to 2.8 per 100 cases using modern surgical techniques and materials. Laboratory studies support close follow-up without treatment as an acceptable mode of management in the majority of these cases.

Animals↗

Comitant strabismus.

Proprioceptive receptors have long been known anatomically to be present in extraocular muscles, specifically at the myotendinous junction. Their function in regulating smooth pursuits is experimentally demonstrated. The clinical significance of this for strabismus is still unknown. Esotropia surgery before resolution of moderate amblyopia is not detrimental. Botulinum toxin injections will correct infantile esotropia but require more anesthesia sessions overall than does conventional surgery, increasing cost. Late-onset comitant esotropia is usually refractive in nature and rarely neurologic. Comitant esodeviation is also prevalent in children with known neurologic insults. In both situations, it is the associated neurologic signs that point to the underlying neurologic cause. Posterior fixation suture will correct a high accommodative convergence/accommodation ratio esotropia. Exotropia negatively affects patients' quality of life. Surgical outcomes differ in patients whose angle of deviation increases with 1 hour of occlusion testing at extreme distances ("outdoor sensitivity"). Recession resection influences the distance and near angles of deviation equally whereas bilateral lateral rectus resection influences the distance deviation more than the near. Spray administration of cycloplegic agents to closed eyelids has been shown to be as effective as administration of eye drops. The spray is much better tolerated by patients and easier to administer. Photorefraction, although not yet effective as a screening tool, is useful to document alignment and refractive errors.

Administration, Topical↗

Development of refraction and strabismus.

In the past year, as in recent years, most of the research on the development of refraction has focused on the following: 1) mechanisms whereby the eye can maintain coordinated growth to achieve emmetropia and 2) disruptions of emmetropization resulting in myopia or hyperopia. Preterm children and those with Down syndrome have higher refractive errors than other children, suggesting a failure of emmetropization. One of the most intriguing studies of the past year and one certain to lead to follow-up studies reported that ambient room illumination at night in a child's first two years is associated with a higher prevalence of myopia than sleeping in darkness. Reports on the development of hyperopia showed that it is axial in nature, similar to myopia. The effects of spectacle interventions to correct refractive errors are still being debated, with recent evidence from children suggesting that lenses do not exacerbate myopia. Analyses of risk factors and numerous new screening procedures detect patients with strabismus for referral at a variety of sensitivity and specificity levels. Hyperopia and high AC/A ratios are most clearly associated as causal agents for esotropia and intermittent exotropia. However, the action of even these simple mechanisms is confounded by abnormal binocular fusion mechanisms and the inability of optical correction to align the eyes of many patients. Asymmetric optokinetic nystagmus, latent nystagmus, and dissociated vertical deviation appear to be linked to infantile esotropia from before its onset. But the way the mechanisms underlying these oculomotor anomalies are causally related to the onset of infantile esotropia remains a mystery.

Humans↗

Blinding orbital cellulitis: a complication of strabismus surgery.

A 56-year-old healthy man underwent left medial rectus recession and lateral rectus resection for esotropia. The next day he developed severe left periocular pain with decreased vision, an afferent pupillary defect, periorbital edema, limited ocular motility, and proptosis. Computed tomography showed fat stranding and less than 90 degrees of posterior globe tenting. Despite intravenous antibiotics to treat orbital cellulitis, and a lateral canthotomy and cantholysis to decompress the orbit, visual acuity worsened to no light perception. The patient underwent emergent orbital decompression including release of the superior and inferior septum and outfracturing of the orbital floor and medial wall; however, there was no recovery of vision. Blinding orbital cellulitis is a rare complication after strabismus surgery. Despite poor prognosis, prompt diagnosis and aggressive treatment may maximize visual potential.

Blindness↗

Ketamine and the oculocardiac reflex. Dysrhythmia in pediatric strabismus surgery: the role of intravenous atropine.

Fifty children in the age-group 1.75-10 years, admitted for cure of strabismus, were anaesthetised with intramuscular ketamine. Half the patients, at random, were given intravenous atropine, while anaesthetised, 5 minutes before operative interference. ECG recording of Lead 2 showed an oculacardiac dysthythmic response to muscle pull in 19 of the 25 unatropinised patients. The atropinised patients failed to show evidence of muscle induced dysrhythmia in any of the subjects (0%) The 25 control traces in the atropinised subjects showed no dysrhythmia after 5 minutes, but the possible immediate transitory dysrhythmic effects of atropine in the presence of ketamine anaesthesia is the subject of further study.

Anesthesia, General↗

Topical amethocaine in strabismus surgery.

A randomized study was performed to assess the effect of topical 1% amethocaine hydrochloride on postoperative analgesia requirements after strabismus surgery. Forty children scheduled for elective operation were allocated randomly to receive either topical amethocaine or normal saline. Postoperative analgesia was evaluated with the use of a four-point assessment score and analgesic requirements. The topical amethocaine provided significantly better postoperative analgesia (p less than 0.001) as measured by both the assessment score and the postoperative analgesia requirement.

Anesthesia, Local↗

Postoperative emesis after pediatric strabismus surgery: the effect of dixyrazine compared to droperidol.

Sixty-one children, ASA physical status I, aged 2-14 years, admitted for strabismus surgery were studied. All were premedicated with diazepam and atropin rectally. Anesthesia was induced with thiopental or with halothane on a facemask, and succinylcholine was given to facilitate tracheal intubation. Anesthesia was maintained with halothane and nitrous oxide. Each child was randomly assigned to receive either no antiemetic prophylaxis (control), droperidol 0.075 mg/kg, or dixyrazine 0.25 mg/kg. The drugs were injected intravenously at the end of surgery. The incidence of vomiting during the following 24 h was 65% in the control group, 48% in the droperidol group, and 25% in the dixyrazine group (P less than 0.05 as compared to the control group). Four hours after the operation, six children in the droperidol group and none in the dixyrazine group (P less than 0.05) were difficult to arouse. It is concluded that dixyrazine reduces the incidence of postoperative vomiting without causing heavy sedation.

Adolescent↗

Is there a cholinergic and an adrenergic phase of the oculocardiac reflex during strabismus surgery?

We investigated the counterregulatory effect of the oculocardiac reflex (OCR) in 25 infants and children during strabismus surgery under three experimental conditions. In group 1, a series of measurements were recorded when the OCR was elicited by traction. The beat-to-beat heart rate reduction ranged from -26 to -64 beats/min (median: -46 beats/min). Constant traction increased heart rate in all patients from +23 to +50 beats/min (median: +30.5; P < 0.001). After a sudden release of the stimulation, heart rate rose further from +6 to +40 beats/min (median: +15; P < 0.001). In group 2, atropine (0.01 mg/kg) was administered 3-4 min prior to the same manipulations as in group 1. Constant traction changed heart rate from -1 to +20 beats/min (median: +4.5; P < 0.01). In group 3, a retrobulbar blockade suppressed the OCR and the counterregulation completely. These findings indicate that there is an active counterregulatory process which maintains heart rate during traction at the extraocular muscles after the bradycardic reflex has been initiated. The bradycardia and the counterregulation may be referred to as cholinergic and adrenergic phrases of the OCR. Atropine eliminates the cholinergic phase. Our study indicates that there may be receptors and afferent fibres for both phases, which can be blocked by local anaesthetics.

Adolescent↗

Measurement of strabismus eyes with a scan ultrasonography.

A series of 25 patients with strabismus, of whom 16 had eso and 9 exo deviation were examined by A scan to determine the antero-posterior diameter of the eye. This seemed smaller than the accepted normal being 22.13 mm and with a greater range than normal --17.95 mm to 25.27 mm. In particular there were more small eyes. The fallacy of planning squint operation on the basis of the measurements of a standard eye is stressed --a 5 mm recession may be excessive in a small eye but inadequate in a large one. Two major variables in deciding on squint surgery are the diameter of the globe and the length of the muscles.

Adult↗

The use of ultrasonography in determining the amount of extraocular muscle surgery in strabismus.

In twenty strabismus patients using ultrasonography a measurement was taken from the apex of the orbit through the centre of rotation of the eye to the front of the eye along the oculomotor axis which is at an angle of approximately 10 degrees to the anteroposterior axis of the eye. From this and from the diameter of the eye average values were derived for the distance from the equator of the medial rectus insertion of 6.27 mm (range 3.96-8. 92 mm) the lateral rectus insertion 8.77 mm, the length of the medial rectus 35.32 mm (range 32. 40-40. 25 mm) and the lateral rectus 37.82 mm (range 34. 79-42. 75 mm). There are sources of error in these measurements but they are probably not great, though corneal diameter and muscle position should be checked at operation. In addition a recession/muscle length ratio may be calculated and it is probably wise not to exceed a ratio of of 0.20 for the medial rectus and 0.25 for the lateral rectus with similar resection muscle length ratios suggested. The variability of the distance of the muscle insertions from the equator is greater than the muscle lengths and it seems important not to recess beyond the equator while alteration of muscle length may be less important. This suggests maximal recession of the medial rectus may vary from 4 up to almost 9 mm and from 6.5 to almost 11.5 mm for the lateral rectus. The value of making these measurements pre-operatively seems obvious and the considerable variation is the amount of squint surgery is stressed, particularly for muscle recessions.

Humans↗

Refractive surgery and strabismus.

This review discusses the potential for strabismic complications after refractive surgery for hyperopia, myopia, anisomyopia, astigmatism and monovision, and how to avoid these complications. Guidelines are given for assessing patients with strabismus seeking refractive surgery. Screening tests are suggested that lead to stratification of refractive surgery patients into different risk groups each warranting a different intensity of evaluation.

Adult↗

Temporal integration in visual cortex of cats with surgically induced strabismus.

Single unit response latencies in striate cortex after visual stimulation with stationary flashed bars were measured and interocularly compared in anaesthetized cats with surgically induced strabismus, in order to elucidate the neural basis of strabismic amblyopia. Four unilateral esotropic and two exotropic cats were studied. The visual onset latencies of cortical neurons ranged from 30 to 170 ms after stimulation of the non-deviating eye at a contrast of 82%. Responses after visual stimulation of the deviating eye were consistently delayed by approximately 10 ms. The latency increase was independent of the direction and absolute angle of squint in the different animals. Peak latencies of cortical neurons ranged from 43 to 245 ms. Median peak latency was 85 ms for the non-deviating and 95 ms for the deviating eye. The rise time of cortical flash responses, as determined from onset-peak differences, ranged between 2 and 170 ms. Direct interocular comparison of response latencies in the remaining binocular neurons revealed an invariable advantage for the non-deviating eye. Supragranular neurons showed a greater interocular latency difference than neurons in layer IV. Visual latencies were contrast-dependent. However, the latency reduction with increasing contrast was less pronounced for the deviating eye. We discuss the possibility that central integration times, especially within cortex, are prolonged in strabismic cats, affecting temporal coincidence of signal processing in the visual cortex. The resulting disturbance of spatio-temporal integration, as caused by a scrambling of geniculo-striate and intracortical connections, may be the substrate of binocular suppression and strabismic amblyopia.

Animals↗

A prospective randomized blinded study of the effect of intravenous fluid therapy on postoperative nausea and vomiting in children undergoing strabismus surgery.

BACKGROUND: Nausea and vomiting is a common postoperative complication that often necessitates the use of antiemetic agents. METHODS: In a prospective, randomized, double blind trial, the effect of perioperative fluid administration on postoperative adverse outcomes following anesthesia was studied. One hundred children undergoing strabismus repair were randomly assigned to receive 10 ml x kg(-1) x h(-1) (control group) or 30 ml x kg(-1) x h(-1) (superhydration group) of lactated Ringer's solution during the operation. During the first 24 h postoperatively, nausea and vomiting, thirst, pain, and fever were evaluated. RESULTS: Groups were similar with respect to demographic data, surgical procedures and baseline hemodynamic variables. In the first 24 h postoperatively, nausea and vomiting occurred in 27 patients (54%) of the control group and 11 (22%) of patients in the superhydration group (P = 0.001). Comparison of the superhydration group with the control group also showed a statistically significant benefit of superhydration on postoperative thirst (P = 0.0002) and fever (P = 0.02). The differences in nausea and vomiting, thirst, and fever remained significant after adjustment for age, gender, weight, and duration of surgery. There was no significant difference between the two groups in postoperative pain. CONCLUSIONS: Intravenous superhydration administration is an inexpensive and safe therapy for reducing postoperative nausea and vomiting and discomfort.

Child, Preschool↗

Postural sway and gait of children with convergent strabismus.

Postural sway and gait of 35 children with convergent strabismus were tested and compared with those of a control group. They were found to have a short stride-length and single-limb support time in walking, particularly at slow speeds. The girls had a large postural sway, but not the boys. The results suggest a common visuomotor disturbance of eye and limb motor-control.

Child↗

Update on strabismus and amblyopia.

This review analyzes progress in the field of infantile strabismus and amblyopia. Only works which are of clinical interest have been reviewed. A brief survey is provided also of subjects matter of international debate, as surgery for accommodative esotropia, the prism adaptation test and the use of sectors for amblyopia treatment. Mention is made of new developments in the field which are not yet applicable to clinical practice. Finally, progress in the approach towards ocular nystagmus is considered as well.

Amblyopia↗