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PubMed1998

[Interocular inhibition in strabismus].

Many patients with acquired strabismus do not suffer from diplopia and confusion after an individually and age-dependent interval. They inhibit the image of the deviated eye by binocular rilvary and particularly by the physiological ability to disregard visually disturbing stimuli. In strabismus with early onset, binocular rivalry is also demonstrable, even for stimuli that do not normally lead to suppression. On the basis of anomalous retinal correspondence, this rivalry occurs between retinal points onto which the same object projects. The retinal area with the lesser eccentricity receives the dominance. The fovea of the deviated eye is therefore not suppressed. In small-angle strabismus with smaller functional differences between anomalous corresponding retinal points anomalous fusion and even stereopsis can be possible as long as strong suprathreshold stimuli are presented. Strabismic amblyopia as a consequence of interfoveal suppression can only develop before anomalous retinal correspondence dominates in the strabismic child.

Humans↗

PubMedDate not supplied

Multifocal VEP difference between early- and late-onset strabismus amblyopia.

PURPOSE: To measure and compare the multifocal visual evoked potentials (mfVEP) difference between early- and late-onset strabismus amblyopia. METHODS: Eleven patients with early- and 11 with late-onset strabismus amblyopia with similar range of visual acuity and 11 normal control subjects were recorded with mfVEP. RESULTS: There was no significant difference in latency or amplitude between amblyopic and fellow eyes for the early-onset amblyopic group, whereas in the late-onset amblyopic group, latencies were significantly prolonged and amplitudes were attenuated in the central region of visual field in the amblyopic eye. The responses in the central region of visual field in both amblyopic and fellow eyes of the early-onset amblyopic group were of longer latency and smaller amplitude than normal. In the late-onset group, the responses from amblyopic eye were of increased latency and decreased amplitude in the central visual field compared with normal, but either latency or amplitude from fellow eye did not differ from normal significantly. CONCLUSIONS: There is significant difference in the mfVEP characteristics of patients with early- and late-onset strabismus amblyopia.

Adolescent↗

PubMed1984

Long-term changes of orienting behavior in cats with artificial divergent strabismus.

Orienting behavior was measured in two monocular spatial localization tasks in normal cats and in cats with artificially induced monocular divergent strabismus. Immediately, and for several weeks after the operation, cats made large "past-pointing errors" with the deviated eye in a direction opposite to the misalignment. These errors were replaced later by "over compensation errors" in the same direction as the strabismus deviation, which persisted for many months after the operation. Over-compensation did not occur when the non-deviated eye was sutured in early life. Electrophysiological measures like grating VEP and A17 single unit responses demonstrated the dominance of the non-deviated eye in the strabismic cats. It is suggested that long-term binocular exposure may lead to a reorganization of visual direction for the deviated eye in divergent strabismus.

Amblyopia↗

PubMed1994

Human strabismus: evaluation of the interhemispheric transmission time and hemiretinal differences using a reaction time task.

Experimentally induced strabismus in visually immature cats leads to abnormal development of the posterior corpus callosum. This, in turn, should lead to abnormal interhemispheric integration of unilaterally presented visual information. To test whether strabismus produces deficits in the human commissural visual system, the interhemispheric transmission time (ITT) was compared in strabismic and normal subjects. Simple unimanual reaction times (RT) were tested in 30 subjects in response to a lateralized target presented monocularly at 4 degrees and 35 degrees nasally and temporally from the fovea along the horizontal meridian. This method was also used to examine the effect of strabismus on the central and peripheral portions of each hemiretina. The results showed that in strabismic subjects with or without amblyopia, the ITT did not differ significantly from normals at both eccentricities. In non-amblyopic strabismic patients, RTs in the central and peripheral portions of hemiretina were comparable to normals. However, a reduced speed of response was found in the central visual field (4 degrees) in the amblyopic eye. Our results suggest that the ITT is normal in strabismic subjects and that the longer RTs in the central portion of the nasal and temporal hemiretina of the amblyopic eye may be associated with the severe amblyopic condition.

Adolescent↗

PubMed1992

Exogenous supply of nerve growth factor prevents the effects of strabismus in the rat.

It has recently been reported that exogenous supply of nerve growth factor prevents the effects of monocular deprivation both in rats and in cats. Here we have extended these experiments to the case of strabismus. Repeated intraventricular injections of nerve growth factor were performed in rats made surgically strabismic early in the critical period. At the end of the critical period the ocular dominance distribution of visual cortical neurons was assessed in strabismic untreated, strabismic nerve growth factor-treated and strabismic Cytochrome C-treated (control) rats by means of extracellular recordings. We found that in rats surgical strabismus causes a consistent loss of binocular neurons. By contrast the treatment with nerve growth factor maintains the normal ocular dominance distribution of neurons in the primary visual cortex. We conclude that nerve growth factor exogenously supplied prevents the effects induced by surgical strabismus in rats and suggest that nerve growth factor has a role in visual cortical plasticity.

Animals↗

PubMedDate not supplied

Low-dose droperidol versus standard-dose droperidol for prevention of postoperative vomiting after pediatric strabismus surgery.

STUDY OBJECTIVE: To determine whether a low dose of droperidol is as effective as a high dose in preventing vomiting after pediatric strabismus surgery. DESIGN: Randomized, double-blind study. SETTING: Operating room and recovery room at a university medical center. PATIENTS: One hundred children undergoing strabismus procedures. INTERVENTIONS: Patients were divided randomly into three groups and received either droperidol 75 microgram/kg, droperidol 20 microgram/kg, or saline. MEASUREMENTS AND MAIN RESULTS: Vomiting was assessed in all groups, as was time to discharge and ability to perform a satisfactory postoperative eye examination. Children who received droperidol vomited less frequently than those who did not (p = 0.0521). There was no difference in the frequency of vomiting between the two groups that received droperidol. CONCLUSION: Droperidol 20 microgram/kg is as effective as droperidol 75 microgram/kg in preventing vomiting after pediatric strabismus surgery. Because higher doses of droperidol may sedate some patients, the lowest effective dose should be used. In this study, however, there was no statistically significant difference with regard to length of recovery room stay.

Adolescent↗

PubMedDate not supplied

Propofol-nitrous oxide versus thiopental sodium-isoflurane-nitrous oxide for strabismus surgery in children.

STUDY OBJECTIVES: To assess the quality of anesthesia and recovery and the frequency of postanesthetic retching and vomiting with propofol anesthesia for pediatric strabismus surgery. DESIGN: Randomized, open, prospective study. SETTING: University hospital. PATIENTS: Forty children scheduled for strabismus surgery. INTERVENTIONS: The 40 patients were all premedicated with oral midazolam and received intraoperative opioids. They were divided into two groups: Twenty children received propofol at induction, followed by maintenance of anesthesia with propofol infusion and an oxygen-nitrous oxide (O2-N2O) mixture. The other 20 children received thiopental sodium at induction, followed by isoflurane in an O2-N2O mixture. MEASUREMENTS AND MAIN RESULTS: At induction, pain and spontaneous movements were seen significantly more with propofol (11 of 20 vs. 0 of 20 for pain and 13 of 20 vs. 0 of 20 for spontaneous movements; p < 0.001), whereas thoracic rigidity was observed only with thiopental sodium (4 of 20). During maintenance of anesthesia, significantly more oculocardiac reflexes were seen with propofol (10 of 20 vs. 3 of 20; p < 0.02). The interval between termination of anesthesia and extubation was significantly shorter with propofol (13 minutes vs. 16 minutes; p < 0.02). For the first 24 hours after surgery, significantly less retching and vomiting were observed in the propofol group (4 of 20 vs. 11 of 20; p = 0.02). CONCLUSIONS: Propofol induction and maintenance of anesthesia for strabismus surgery in children significantly lowers the frequency of postanesthetic retching and vomiting, but propofol is associated with pain and spontaneous movements at induction and a high frequency of oculocardiac reflexes during maintenance infusion.

Anesthesia Recovery Period↗

PubMed1995

Prevention of emesis after strabismus repair in children: a prospective, double-blinded, randomized comparison of droperidol versus ondansetron.

STUDY OBJECTIVE: To compare the effectiveness of ondansetron with droperidol in preventing postoperative emesis in children after strabismus repair. DESIGN: Randomized, double-blind study. PATIENTS AND SETTING: 57 ASA physical status I and II children aged 3 to 14 years, undergoing outpatient strabismus repair in two separate study centers. INTERVENTIONS: Patients were randomized to receive either 0.15 mg/kg intravenous (i.v.) ondansetron or 0.075 mg/kg i.v. droperidol shortly after induction of anesthesia. MEASUREMENTS AND MAIN RESULTS: Number of episodes of emesis and times to discharge from the recovery room and ambulatory center were assessed. Twenty-nine (94%) of 31 children who received ondansetron and 21 (81%) of 26 children who received droperidol were emesis-free (p = NS). There were no significant differences in the number of episodes of emesis on the day after surgery or times to discharge. CONCLUSIONS: Ondansetron is at least as effective as droperidol in reducing the frequency of emesis in children after strabismus repair, and it did not shorten times to discharge home. The low number of patients in our study may have masked a difference in effect between the two groups. The clinician should decide whether the increased cost of ondansetron justifies its use over other antiemetics.

Adolescent↗

PubMed2005

Amniotic membrane transplantation for the repair of severe conjunctival dehiscence after strabismus surgery with adjustable sutures.

PURPOSE: To evaluate the outcome of amniotic membrane transplantation (AMT) for the repair of severe conjunctival dehiscence that occurred during or after fornix-incision strabismus surgery with adjustable sutures. DESIGN: Retrospective, interventional case series. METHODS: Four patients in whom severe conjunctival dehiscence developed during or after strabismus surgery were treated with amniotic membrane grafts. The extent of conjunctival reepithelization over sclera, range of ocular motility, and patient comfort were evaluated immediately after the surgery and at 1, 2, and 4 weeks. RESULTS: The mean follow-up period was 16 weeks (range 4 to 28 weeks). Conjunctival dehiscence was detected 0 to 14 days after surgery. AMT was performed 0 to 14 days later. The conjunctival defect was reepithelized in all patients by the fourth postoperative week without evidence of scarring or restriction of motility. CONCLUSIONS: In the treatment of large conjunctival defects that may follow strabismus surgery, AMT may be an alternative to conservative management or primary conjunctival closure.

Adult↗

PubMed2006

The Amblyopia and Strabismus Questionnaire: English translation, validation, and subscales.

PURPOSE: To establish the English-language version of the Amblyopia and Strabismus Questionnaire (ASQE). DESIGN: Prospective cohort study. METHODS: A structured translation process was followed to generate the ASQE, a 26-item instrument (originally in Dutch) containing five subscales for fear of losing the better eye, distance estimation, visual disorientation, double vision, and social contact and appearance. The ASQE was administered to 150 adults in a private practice setting. All had strabismus with or without amblyopia and visual acuity of 20/50 or better in at least one eye. Subjects also completed a brief disability questionnaire, and they were further characterized by levels of unilateral vision loss, diplopia, and asthenopia. RESULTS: ASQE scores were highly correlated with the disability questionnaire outcomes (r = -.76, P < .0001). Internal consistency reliability (Cronbach alpha) of the subscales ranged from 0.80 to 0.92. Strong correlations were found between clinical characteristics and the ASQE (total score and subscale scores). CONCLUSIONS: The ASQE showed good psychometric properties that are in line with those of the original instrument. This, combined with strong correlations between ASQE scores and clinical characterization of the participants, establishes the ASQE as a useful tool for use in populations with strabismus and/or amblyopia.

Adolescent↗

PubMed2004

Maximum angle of horizontal strabismus consistent with true stereopsis.

BACKGROUND: We prospectively evaluated the performance of three stereoacuity tests in patients with a wide range of strabismus angles to determine the maximum angle of horizontal strabismus consistent with true stereopsis as well as the extent of false-positive results. METHODS: Subjects age > or = 5 years old (n = 186) with constant horizontal strabismus were prospectively studied. Stereoacuity was measured using the Titmus Fly, Animals, and Circles tests; the original Preschool Randot test; and the Frisby test. We defined a false-positive result as any positive response to a stereoacuity test when a patient had > 20 prism diopters (PD) of deviation. Based on the results from our previous study of monocularly patched adults, we then defined a true-positive result as Titmus circles five to nine, at least 400" on the original Preschool Randot test, or a pass on the Frisby test. Data were then analyzed to determine a maximum deviation consistent with true stereopsis. RESULTS: False-positive results occurred with Titmus Fly (6%), Titmus Animals (10%), Titmus Circles (35%), and the 800 seconds of arc (") level of the original Preschool Randot test (10%). No false-positive results were seen with the Frisby test. Applying the criteria for a true-positive result, we found that no patient with > 10 PD of deviation had true stereopsis. The two patients with 10 PD and 6 PD deviations could not subsequently pass the Frisby test and were therefore deemed not to have true stereopsis. We concluded that the threshold for true stereopsis may be as low as 4 PD of horizontal deviation. CONCLUSION: In summary, the Titmus Fly, Titmus Animals, and Titmus Circles (the first four circles) tests possess monocular clues that limit their usefulness for clinical testing. The Frisby test is particularly useful for rapid assessment of whether stereopsis is present or absent. The new Preschool Randot test is valuable for quantifying stereopsis in both children and adults. True stereopsis may be rare when a patient has a horizontal deviation > 4 PD.

Adolescent↗

PubMed2004

Subtenons lidocaine injection for postoperative pain relief after strabismus surgery in children: A prospective randomized controlled trial.

BACKGROUND: We previously reported a pilot study of the use of subtenons lidocaine after primary, unilateral strabismus surgery in children. This study suggested an association between subtenons lidocaine administration at the conclusion of surgery and a reduction of pain in the immediate postoperative period. As a result of this pilot study we performed a full-scale prospective, randomized controlled trial to fully evaluate the efficacy of this intervention. METHODS: Children undergoing primary surgery or reoperations for strabismus were recruited. If randomized to the treatment group, 1 ml of 2% lidocaine was injected into the subtenons space of each operated eye, just prior to conjunctival closure. The child's parents, who were masked to the intervention, assessed pain over 4 h postoperatively using an objective pain-scoring tool. Pain scores were recorded on return to the ward (0 h, approximately 20 to 30 min after the completion of surgery) and at 1, 2, and 4 h later. RESULTS: One hundred eleven children were recruited, of whom 91 (82.0%) underwent unilateral and 20 (18.0%) underwent bilateral surgery. Ninety operations (81.1%) were primary procedures and 21 (18.9%) were reoperations. Fifty-four children (48.6%) were randomized to the treatment group and 57 (51.4%) were randomized to the control group. A subtenons lidocaine injection was associated with a significant reduction in pain at the 0 h observation (P = 0.0056), and the total pain score over the 4-h postoperative period was significantly lower in the treatment group compared to controls (P = 0.0381). There was no difference between the groups with respect to the need for additional systemic analgesia (P = 0.307). CONCLUSION: This study showed that an intraoperative injection of subtenons lidocaine is associated with a significant reduction in postoperative pain during the first postoperative hour for all types of childhood strabismus surgery. There was no difference between the groups in the need for systemic analgesia.

Analgesia↗

PubMed2004

Predictive factors underlying the restoration of macular binocular vision in adults with acquired strabismus.

PURPOSE: To investigate whether macular binocular vision can be permanently lost following acquired strabismus and to identify predictive factors underlying its restoration. SUBJECTS AND METHODS: Twenty-three patients with strabismus acquired after binocular vision maturation were enrolled. Factors studied included duration of eye misalignment, age at treatment, pre-surgical strabismus type, pre-surgical diplopia, and pre-surgical capacity for binocularity. The restoration of macular binocular vision was evaluated between 1 and 3 years following successful eye re-alignment and was defined as 60 seconds of arc stereopsis or better on the Titmus circles and/or the Preschool Randot Stereoacuity test. RESULTS: Sixteen of 23 (70%) or 7/23 (30%) of patients achieved macular binocular vision following successful surgical eye realignment using the Titmus circles versus the Preschool Randot Stereoacuity test. Patients with < or =12 months constant eye misalignment were more likely to achieve macular binocular vision following treatment than patients with >12 months constant eye misalignment. CONCLUSIONS: Macular binocular vision continues to be susceptible to permanent loss in adult patients. Factors that are predictive of the restoration of macular binocular vision include duration of constant eye misalignment and the pre-surgical capacity for binocularity.

Adolescent↗

PubMed2004

Staphylococcus epidermidis endophthalmitis following strabismus surgery.

Inadvertent perforation of the sclera is a well-known complication of strabismus surgery. Scleral perforation may lead to retinal detachment, intraocular hemorrhage, cataract, hyphema, glaucoma, endophthalmitis, and phthisis bulbi. However, endophthalmitis following strabismus surgery is extremely rare, with an estimated incidence of 1:3500 to 1:185,000. We describe a case of Staphylococcus epidermidis endophthalmitis in an adult following strabismus surgery treated successfully with intravitreal antibiotics and corticosteroids.

Aged↗

PubMed2005

Localized, extreme scleral thinning causing globe rupture during strabismus surgery.

Eye muscle surgery in strabismus patients usually is without serious, vision-threatening complications. The risk of scleral perforation during strabismus surgery has been reported to approximately 1% but usually without serious sequelae. Inadvertent perforation may occur during muscle disinsertion or during muscle reattachment. The risk of perforation is increased in myopic eyes, and the risk is higher in recessions than in other strabismus procedures. We report a case of sudden rupture of the globe during a recession procedure on the superior rectus muscle caused by a localized area of extreme scleral thinning adjacent to the muscle insertion. To our knowledge, this serious complication has not previously been reported.

Aged↗

PubMed2006

High-resolution magnetic resonance imaging demonstrates abnormalities of motor nerves and extraocular muscles in patients with neuropathic strabismus.

INTRODUCTION: Although the ocular motility examination has been used traditionally in the diagnosis of strabismus that is a result of cranial nerve (CN) abnormalities, magnetic resonance imaging (MRI) now permits the direct imaging of lesions in CN palsies. METHODS: Prospectively, nerves to extraocular muscles (EOMs) were imaged with T1 weighting in orbits of 83 orthotropic volunteers and 96 strabismic patients in quasicoronal planes using surface coils. Intraorbital resolution was 234-312 microns within 1.5- to 2.0-mm thick planes. CNs were imaged at the brainstem using head coils and T2 weighting, yielding 195 micron resolution in planes 1.0-mm thick in 6 normal volunteers and 22 patients who had oculomotor (CN3), trochlear (CN4), or abducens (CN6) palsies and Duane syndrome. RESULTS: Oculomotor (CN3) and abducens (CN6) but not trochlear (CN4) nerves were demonstrable in the orbit and skull base in all normal subjects. Patients with congenital CN3 palsies had hypoplastic CN3s both in orbit and skull base, with hypoplasia of involved EOMs. Patients with chronic CN6 and CN4 palsies exhibited atrophy of involved EOMs. Patients with Duane syndrome exhibited absence or hypoplasia of CN6 in both orbit and brainstem regions, often with mild hypoplasia and apparent misdirection of CN3 to the lateral rectus muscle. Unlike CN6 palsy, patients with Duane syndrome exhibited no EOM hypoplasia. Patients with congenital fibrosis exhibited severe hypoplasia of CN3, moderate hypoplasia of CN6, and EOM hypoplasia, particularly severe for the superior rectus and levator muscles. CONCLUSION: High-resolution MRI can directly demonstrate pathology of CN3 and CN6 and affected EOM atrophy in strabismus caused by CN palsies. Direct imaging of CNs and EOMs by MRI is feasible and useful in differential diagnosis of complex strabismus.

Abducens Nerve Diseases↗

PubMed2006

The cost utility of strabismus surgery in adults.

PURPOSE: Cost-utility analysis evaluates the cost of medical care in relation to the gain in quality-adjusted life years (QALYs). Our purpose was to develop a cost model for surgical care for adult strabismus, to estimate the mean cost per case, to determine the associated gain in QALYs, and to perform cost-utility analysis. METHODS: A cost model incorporated surgery, pre- and postoperative care, and a mean of 1.5 procedures per patient. The gain in QALYs was based on the improvement of utility on a scale from 0 (death) to 1 (perfect health). Utility was measured through physician-conducted interviews employing a time tradeoff question (seeking to estimate the portion of life expectancy a patient would be willing to trade for being rid of disease and associated effects). The interviews were conducted before and 5 to 8 weeks after surgery in 35 strabismic patients (age 19-75 years). RESULTS: The cost model resulted in an estimated total cost of 4,254 dollars per case. A significant improvement of utility was found: 0.96 +/- 0.11 postoperatively versus 0.85 +/- 0.20 preoperatively (p = 0.00008). Based on the mean life expectancy (36.0 years) of these patients, and discounting outcomes and costs by 3% annually, this resulted in a mean value gain of 2.61 QALYs after surgery and a cost-utility for strabismus surgery of 1,632 dollas/QALY. CONCLUSIONS: In the United States, treatments <50,000 dollars/QALY are generally considered "very cost-effective." Strabismus surgery in adults falls well within this range.

Adult↗

PubMed2005

Optical imaging in cat area 18: strabismus does not enhance the segregation of ocular dominance domains.

While early-onset strabismus leads to clearly segregated domains of the left and the right eye in cat primary visual cortex (area 17), far less is known about experience-dependent plasticity of ocular dominance in area 18. We therefore used optical imaging of intrinsic signals to analyze the influence of strabismus on cortical maps in cat area 18. Monocular visual stimulation of the left and right eye with moving square wave gratings of four different orientations induced patchy activity maps. Unlike our previous observations in cat area 17, the monocular activity maps in area 18 of strabismic cats were rather similar so that functional ocular dominance domains were not clearly segregated. Imaging of the 17/18 border region confirmed this observation and revealed a sudden change in the segregation of the left and right eye domains across the border. Our results demonstrate that modified visual input can have different consequences for different visual areas: while the decorrelation of activity between the two eyes (as induced by strabismus) clearly enhances the segregation of ocular dominance domains in cat area 17, area 18 does not show this effect although electrophysiological studies have confirmed that the percentage of binocularly driven neurons is as reduced as in area 17.

Animals↗