Horizontal and vertical angle kappa.

BACKGROUND: The aim of this study is to report the geometric range of angle kappa formation in patients with and without strabismus. PATIENTS AND METHODS: This is a retrospective study of three patients with angle kappa in different planes. Routine eye examinations, including visual acuity, slit-lamp examination, and ophthalmoscopy, were performed. A thorough orthoptic examination revealed a notable difference between the prism and alternate-cover test and the Hirschberg measurements. RESULTS: The first patient exhibited a bilateral vertical angle kappa into opposite directions due to retinochoroidal scars. Two other patients presented with horizontal angle kappa deviations. In one patient a true accommodative esotropia was exaggerated by a right negative angle kappa. The other patient had a pseudoexotropia due to bilateral positive angle kappa. Macular ectopia was noted in all cases. CONCLUSIONS: The patients herein reported demonstrate a marked variability of angle kappa occurrence in the horizontal and vertical plane. The angle kappa can exaggerate or conceal the size of the true heterotropia.

Intraoperative intorsional traction test of the inferior oblique.

PurposeWe present a novel variation of the traction test of the inferior oblique (IO) muscle. We demonstrate the correlation between the traction test and clinically graded IO overaction and describe the utility of this test to confirm IO weakening.MethodsWe performed a retrospective chart review on all patients who underwent IO surgery and intraoperative intorsion traction tests by a single surgeon over a 10-year period. We compared the traction test results, in 'clock hours' of freedom, before and after IO surgery. We correlated the torsion test at start of surgery with clinical observed IO overaction (scale 0 to +4) in 67 IO operations (56 myectomies, 6 anterior transpositions, 4 myotomies, and 1 recession) and compared to a control group of 23 eyes with minimal or no IO overaction.ResultsThe mean intorsion freedom in the eyes undergoing IO surgery was less than in control eyes (1.63 vs 1.89 clock hour; P<0.00005). There was a significant inverse relationship between grading of clinical IO action and the intorsion test result (Pearson rank coefficient, (r=-0.45; P<0.00001)). Myectomy produced the greatest change in torsion freedom (mean 1.32 clock hour), with all myectomies showing at least 1 clock hour extra freedom after the surgery.ConclusionsThe intorsion traction test confirmed that the IO stiffness correlated with pre-operative IO overaction grade. While it can be helpful in confirming that the entire IO muscle was weakened, it does not substitute for the careful inspection at the end of surgery to ensure there are no remaining IO fibers.

The rat electroretinogram in combined zinc and vitamin A deficiency.

To assess the relative importance and interdependence of zinc and vitamin A in retinal function, a group of 36 male Wistar rats were raised in dim illumination and deprived of both zinc and vitamin A (Z-A-) for 90 days (Phase I) until they lost weight and showed signs of both vitamin A and zinc deficiency. Scotopic electroretinograms (ERGs) showed an average 1.5 log unit elevation in light intensity needed to elicit a 200 microV b-wave (criterion intensity) as compared to a control-pair-fed group of rats. Tissue samples from the Z-A- rats showed undetectable liver vitamin A (less than 10 micrograms/g) and a significantly decreased level of femur zinc compared to the control group (P = 0.02). There was photoreceptor outer segment degeneration and loss of cells in the outer nuclear layer of the retina. For Phase II the 24 surviving rats were randomized into three treatment groups--one group remained vitamin A-deficient (A-) but received zinc and retinoic acid, the second remained zinc-deficient (Z-) but received vitamin A and retinoic acid, and the third group was repleted with both zinc and vitamin A (Z+A+) and also received retinoic acid. ERGs were performed 30 and 60 days after randomization. The criterion intensity of the Z+A+ and Z- groups approached normal by 60 days, while that of the A- rats deteriorated a further 1.0 log unit. Histologic studies of the A- rats showed abnormalities in cornea, photoreceptor outer segments, and gut mucosa. All animals had testicular atrophy. Vitamin A repletion significantly reverses retinal degeneration from the Z-A- state even in the presence of moderate zinc deficiency. Zinc supplementation alone does not prevent ongoing retinal degeneration from severe vitamin A deficiency.

Defective processing of motion-defined form in the fellow eye of patients with unilateral amblyopia.

The following three measurements were made on a group of 20 pediatric and 5 adult patients with unilateral amblyopia: (1) speed threshold for recognizing motion-defined dotted letters; (2) recognition acuity for isolated solid letters of 4% contrast; and (3) Snellen line acuity for high-contrast letters. Normal limits were established with a group of 30 pediatric and 10 adult control subjects. The main finding was that, in amblyopic children, a high percentage (83%, 15 of 18) of fellow eyes showed a degraded ability to recognize motion-defined letters, even though Snellen acuity and 4% letter acuity were normal for age. The fellow eyes of all nine patients with strabismic amblyopia showed this pattern of loss, as did four of six fellow eyes of patients with anisometropic amblyopia and two of three fellow eyes of patients with anisometropic plus strabismic amblyopia. Only two clinically unaffected eyes were normal for motion-defined letters. These eyes belonged to patients with anisometropic amblyopia. Eighteen of the 19 previously amblyopic eyes tested were abnormal for motion-defined letters even though Snellen acuity was within normal limits for 6 of these eyes. In adults, only one of five fellow eyes failed the motion-defined letter test. It was concluded that the degradation of form perception associated with amblyopia can be different for luminance-defined and motion-defined form and that defective processing of motion-defined form is common in the fellow eyes of children with unilateral amblyopia.

Cortical binocularity and monocular optokinetic asymmetry in early-onset esotropia.

PURPOSE: To investigate the correlation between directional asymmetry in ocular responses to monocularly viewed optokinetic stimuli (monocular optokinetic nystagmus, MOKN) and sensory fusion in infants and toddlers with early-onset esotropia. METHODS: Subjects were 14 infants and toddlers with early-onset esotropia (7-26 months old; median, 10 months), and 16 with no esotropia (6-22 months; median, 11 months) who provided control data. Monocular optokinetic nystagmus in response to a 30 degrees/sec square-wave grating (0.25 cycles/degree) was measured by electro-oculogram. Sensory fusion was assessed with visual evoked potentials (VEPs) to random-dot correlograms after correction of the strabismus angle with Fresnel prisms. RESULTS: All subjects with early-onset esotropia had MOKN with a faster slow-phase component for temporal-to-nasalward (TN) than nasal-to-temporalward (NT) motion. Ninety-three percent of subjects had MOKN asymmetry higher than the 95th percentile of the control group. Of subjects who cooperated with VEP fusion testing, 5 subjects with early-onset esotropia (45%) and 11 control subjects (92%) showed evidence of sensory fusion. CONCLUSIONS: Symmetrical MOKN did not develop in infants and toddlers with early-onset esotropia. This deficit existed in most infants who showed sensory- cortical fusion. These results are consistent with the belief that optokinetic nystagmus asymmetry may not be associated with a deficit in the cortical fusion facility, but rather with deficits in binocular pathways projecting to MOKN control centers. These deficits may be associated with abnormal processing subsequent to sensory fusion or with abnormal processing in motion pathways, which run parallel to sensory fusion pathways.

Egocenter location in children with strabismus: in the median plane and unchanged by surgery.

PURPOSE: Previous studies have shown that there are spatial localization shifts after horizontal strabismus surgery when a patient performs an open-loop pointing task. After monocular enucleation, an adult will also show a shift in the pointing response. Other studies have shown that in children who underwent enucleation, the egocenter location shifts toward the remaining eye. Is the pointing shift after surgery in children with strabismus the result of a shift in egocenter location? METHODS: Using a modified Roelofs' method for measuring the egocenter, eight children were tested before and after horizontal strabismus surgery to see if there were any shifts in egocenter location. One control group consisted of six children undergoing surgery for correction of vertical strabismus in which the horizontal muscles would be unaltered. RESULTS: Presurgery measurements of egocenter location in the people with strabismus were the same as those found in the other control group of 12 normal children. Postsurgical measurements of eye position showed horizontal rotations of 14.5 degrees for the horizontal group and 2.4 degrees for the vertical group. Egocenter measurements showed no postoperative shift for either strabismus group. CONCLUSIONS: Thus, the pointing shift seen in the previous studies is not from a shifting egocenter location but from a change in the registered position of the eye in the orbit.

Electrophysiological evidence of cortical fusion in children with early-onset esotropia.

PURPOSE: To investigate sensory fusion responses in infants and children with early-onset esotropia to gain insights into the sequence of events that leads to strabismus. METHODS: Sensory fusion was tested by measuring visual evoked potential (VEP) responses to dynamic random dot correlograms (DRDCs) in a group of children (n = 23) with early-onset esotropia. Thirteen children were tested before surgical alignment, and 13 children were tested after surgical alignment (three children were tested before and after surgery). If the angle of strabismus was larger than 5 prism diopters, it was corrected with Fresnel prisms (Fresnel Prism and Lens, Scottsdale, AZ). RESULTS: Five (38%) of the 13 children who were tested before surgery showed detectable VEP responses to correlogram stimuli compared with 11 (85%) of the 13 children who were tested after surgical alignment. There were no significant statistical differences between VEP responses to DRDCs from the postsurgery group and VEP responses from an age-matched control group with normal binocular vision. CONCLUSIONS: The presence of cortical sensory fusion in children with early-onset esotropia suggests that a congenital defect of sensory fusion cannot be the root cause of esotropia in most children. The data suggest that sensory fusion, when measured by VEP responses to DRDCs, is more robust than stereopsis to abnormal binocular experience and support the notion that pathways processing correlated/anticorrelated stimuli may not completely overlap with pathways processing disparity information.

Orbital hypotelorism. An isolated autosomal dominant trait.

Four patients from three consecutive generations of a family with ocular hypotelorism are described. Radiographs document a subnormal distance between the medial orbital walls. To our knowledge, this is the first report of heritable isolated orbital hypotelorism. The pedigree is consistent with an autosomal dominant disorder.

Monocular horizontal OKN in observers with early- and late-onset strabismus.

Several reports on monocular optokinetic nystagmus (OKN) in observers with strabismus have found that asymmetry of OKN tends to occur in both eyes of observers with an early onset of strabismus but only in the deviating eye of those with a later onset of strabismus. Our objective was to quantify and compare the magnitude of the OKN asymmetry in each eye as a function of observer's age at onset of strabismus. We studied monocular OKN in ten observers with early-onset (up to 24 months of age), seven observers with late-onset (after 24 months of age) unilateral strabismus, and 12 normally sighted control observers. In the deviating eye, observers with early-onset strabismus showed large OKN asymmetries in favour of nasalward motion while observers with late-onset strabismus showed smaller OKN asymmetries in that eye. The majority of early- and late-onset observers showed near normal OKN in the non-deviating eye although the early-onset observers showed bilateral asymmetries more often. These findings may be due to both age at onset of strabismus and chronological age and are discussed in terms of the issue of plasticity or recovery of function.

Silicone tube intubation in disorders of the lacrimal system in children.

We analyzed the results of 81 silicone intubations of the lacrimal system in 56 patients aged 6 months to 16 years after posttreatment follow-up of at least two months. Standard probing just before intubation allowed us to group cases by obstruction sites: proximal, distal, or combined. Overall, the outcome was successful in 65 (80.3%) cases. In cases of trauma, success was achieved in two of five patients with proximal, five of nine patients with distal, and two of two patients with combined obstructions. In nontraumatic blockages, we achieved success in 13 of 16 proximal, 30 of 35 distal, and 13 of 14 combined obstructions.

Anatomic variations of the inferior oblique muscle: a potential cause of failed inferior oblique weakening surgery.

PURPOSE: To document the variations in normal anatomy that occur at the insertion of the inferior oblique muscle and in the vicinity of its surgical capture site (10 to 12 mm from the insertion). METHODS: One hundred intact cadaver orbits with no history of eye muscle or orbital disorders during life were carefully dissected to expose the entire length of the inferior oblique muscle. The number of divisions of muscle at the insertion, total width of the muscle belly, and variations in anatomy 10 and 12 mm from the insertion were recorded. RESULTS: Seventeen (17%) of the 100 inferior oblique muscles had multiple divisions at the insertion. Eight muscles (8%) had two bellies at 10 or 12 mm from the insertion. Among these eight, four had two distinct (bifid) bellies extending to the insertion, and four had dehiscences in the muscle. The mean muscle width among these eight specimens was 0.5 and 0.7 mm larger than the mean width of the other 92 specimens at the 10 mm and 12 mm positions, respectively. Neither difference was significant at the .05 level. CONCLUSIONS: Multiple insertions were found in 17% of inferior oblique muscles examined; duplications of the inferior oblique muscle at the surgical capture site were found in 8%. These duplications may account for some cases of recurrence or persistence of inferior oblique overaction after weakening surgery, owing to inadvertent incomplete capture of the muscle during surgery.

Botulinum toxin injections in the treatment of blepharospasm, hemifacial spasm, and eyelid fasciculations.

Seventy-six patients with blepharospasm (mean age 56.9 years) received 248 injection treatments with botulinum A exotoxin (mean 3.1 treatments per patient): 87.0% of treatments led to total relief of spasms for a mean interval of 14.1 weeks. The average duration of response remained fairly constant over the first six injection series, although patients with the most severe spasms had shorter intervals than patients with less severe symptoms. Twenty patients with hemifacial spasm (mean age 56.9 years) received 44 treatments (mean 1.9 treatments per patient): In 93.1% of cases there was total relief of periocular and perioral spasms, with a mean interval of 17.4 weeks. The average duration of response for the third series of treatments was much shorter than the mean durations for the first two treatments. Side effects were always transient and included ptosis (23.3%), dry eyes (18.1%), tearing (5.5%), and strabismus (1.4%). No patient had a systemic reaction to the drug. Chronic benign eyelid fasciculations were also successfully treated in 3 patients with single treatments.

The double-bellied inferior oblique muscle: clinical correlates.

PURPOSE: We previously reported an 8% incidence of double-bellied inferior oblique (IO) muscles at the surgical capture site (10-12 mm from insertion) in cadaveric specimens. This companion study sought to determine how often this anomaly is encountered at surgery for clinically overacting IO muscles and whether clinical findings or surgical outcomes in cases with double-bellied muscles differ from those with single-bellied muscles. METHODS: For 7 years we collected preoperative, intraoperative, and postoperative data on all patients for whom one surgeon performed primary IO weakening operations for overactions. We compared eyes with double-bellied IO muscles to those with single-bellied muscles on 4 variables--gradings of preoperative IO and superior oblique (SO) actions, presence of fundus excyclotropia, differences between horizontal deviations in upgaze and downgaze, and presence and sizes of primary position hypertropias--to determine whether one or more of them could predict the presence of a double-bellied muscle. Finally, we assessed postoperative IO actions to determine whether the presence of a double-bellied muscle influenced the effectiveness of IO weakening surgery in reducing overaction. RESULTS: Among 162 patients (247 eyes) who underwent this surgery, 77 (77 eyes) had unilateral surgery and 85 (170 eyes) bilateral. Twenty-seven (10.9%) of the 247 muscles had double bellies. Among all variables compared, only the incidence of fundus excyclotropia differed significantly between groups, occurring more often in eyes with double-bellied IO muscles (48% vs 27%; P =.041). The efficacy of weakening surgery in reducing overactions was similar in both groups. CONCLUSION: The finding that eyes with double-bellied IO muscles showed a higher incidence of fundus excyclotropia suggests that the presence of a second belly may alter the physiologic action of the IO muscle.

Unilateral recession and resection in Duane syndrome.

PURPOSE: To assess the efficacy of lateral rectus resection with medial rectus recession in the affected eye of patients with Duane retraction syndrome (DRS) with esotropia and limited abduction, compared with bilateral medial rectus recessions. METHODS: The charts of 9 patients with DRS who underwent a recession-resection procedure and 10 patients with DRS who underwent bilateral medial rectus recessions were reviewed. Ocular ductions (graded from 0 = full duction to -4 = total deficit), severity of retraction, alignment, head position, and binocular single vision field (for study group only) were recorded before and after surgery. RESULTS: Before surgery, the study and control groups did not differ in mean primary position esotropia (16.9 and 18.8 PD, respectively), face turn (16.5 degrees and 15.0 degrees, respectively), average limitation of abduction (-3.9 and -3.7, respectively), or adduction (-0.1 and -0.3, respectively). After surgery, both groups had similar mean face turns (3.9 degrees and 1.0 degrees ), esotropia (3.3 PD and 1.0 PD), and abduction limitation in the affected eye (-2.4 and -2.6). However, mean adduction was significantly worse in the control group than in the study group (-1.5 vs -0.6, P = .02). Globe retraction improved in all control subjects. It worsened in 5 study subjects and did not improve in the other 4. In the study group, 1 patient required reoperation for undercorrection and another was overcorrected. CONCLUSION: Seven of 9 patients with DRS, selected on the basis of esotropia, limited abduction, and mild retraction, benefited from a recession-resection procedure. Abduction improved to the same degree as seen after bilateral medial rectus recessions, with less tendency to limit adduction.

A prospective evaluation of anterior transposition of the inferior oblique muscle, with and without resection, in the treatment of dissociated vertical deviation.

BACKGROUND: Anterior transposition of the inferior oblique muscle (ATIO) has become a popular surgical treatment for dissociated vertical deviation (DVD), particularly in patients with coexisting inferior oblique muscle overaction (IOOA). We wanted to assess whether adding a resection improves the outcome compared with standard anteriorization. METHODS: We undertook a prospective, randomized evaluation of ATIO, with and without a 7-mm resection, in patients with DVD of at least 5 PD in one eye. We included 51 eyes of 30 patients, 26 eyes treated with the standard ATIO and 25 treated with a 7-mm resection added. We recorded the size of the preoperative and final DVD, grade of the preoperative and final IOOA, rates of reoperation, and complications. Mean follow-up was 15.4 months in the standard group and 25.0 months in the resection group, with a minimum of 4 months for all cases. RESULTS: The median preoperative and postoperative DVD was 12 PD and 4 PD in the standard group, respectively. This compared with 14 PD and 4 PD, respectively, in the resection group, representing no statistically significant difference in outcome. The presence or absence of IOOA did not influence the result of ATIO for either group. No significant complications of surgery occurred in either group. CONCLUSIONS: ATIO is an effective treatment for DVD and can be used to treat DVD in patients with or without IOOA, with few adverse effects. Our study revealed no advantage to adding a 7-mm resection to the standard procedure.

Vertical latent nystagmus component and vertical saccadic asymmetries in subjects with dissociated vertical deviation.

PURPOSE: This study was conducted to quantify the vertical component of a latent nystagmus observed in subjects with dissociated vertical deviation (DVD), as well as to provide further evidence for vertical saccadic asymmetries in these individuals. METHODS: Binocular eye movements of subjects with DVD were recorded in two dimensions using a noninvasive video-based eye tracker while cover/uncover tests, alternate cover tests, and vertical saccades were performed. RESULTS: A small amplitude (1.5 degrees or less) vertical component of latent nystagmus can be observed in some subjects with DVD and is larger in the deviating eye than in the viewing eye. The frequency of the vertical nystagmus component is the same in each eye for any given fixation condition but may change depending on which eye is fixating. DVD in the presence of a vertical component of latent nystagmus can be adequately modeled by the algebraic sum of an exponentially decreasing velocity DVD and a nystagmus with an exponentially decreasing slow phase velocity. In general, the occluded eyes of DVD subjects make smaller downward saccades than the viewing eyes. CONCLUSIONS: It is possible but not obligatory that DVD subjects will have a vertical component of latent nystagmus. Algebraic summation of an exponentially decreasing velocity DVD and a vertical component of latent nystagmus provides a more parsimonious explanation of the observed saccadic eye movements than modeling the DVD itself as a combination of vergence and saccadic movements. Subjects with DVD show a range of saccadic yoking from nearly complete saccadic conjugacy to nearly complete dissociation.

Bilateral idiopathic Brown's syndrome with delayed onset in the second eye.

PURPOSE: We describe 6 cases of a previously unreported variation of bilateral Brown's syndrome that presented in congenital form in one eye and developed later in the fellow eye with no underlying cause. METHODS: We reviewed the clinical records of 6 patients from 6 separate practices to determine whether there were any common clinical features on presentation or in their clinical courses. RESULTS: All 6 patients were diagnosed with unilateral congenital Brown's syndrome at the first ophthalmologic assessment but showed no evidence of the syndrome in the fellow eye. In 5 cases the contralateral syndrome developed in the second eye after surgery was performed on the first eye, and in 1 case it developed before any surgery was done. The ages at onset of the syndrome in the second eye ranged from 2 to 8 years. None of the children had any evidence of systemic illness or local orbital disease to explain an acquired Brown's syndrome. CONCLUSION: To our knowledge, this is the first reported series of cases of bilateral Brown's syndrome that manifested sequentially in the eyes with no known causes for an acquired syndrome in the second eye. This finding supports the premise that congenital and acquired Brown's syndrome are on a continuum with a common pathophysiology of restriction of free movement of the superior oblique tendon in the trochlea.

Outcome criteria in strabismus surgery.

Criteria for success in strabismus surgery should include more than just the alignment result in primary position. It is important to consider as well the extent of the field of BSV gained: restoring a useful range of BSV will maximize the patient's ability to carry on daily activities. Psychometric tests can also be used to provide objective measures of improvement following strabismus surgery. Irrespective of the patient's age, the realigning of an eye is reconstructive, not cosmetic, surgery. Surgery in children and adults can restore fusion and normalize the field of BSV in most cases. These gains are possible even in the presence of amblyopia. It could be argued that realigning a blind eye yields no functional improvement and should not necessarily be covered by insurance plans. These cases are not common. In all other cases the functional benefits of adult strabismus surgery justify maintaining insurance coverage for this surgery in jurisdictions throughout North America.

Four-muscle surgery for infantile esotropia with V-pattern.

Inferior oblique overaction is frequently seen with infantile esotropia. In patients with infantile esotropia and V-pattern with moderate to large inferior oblique overactions, the oblique weakening can be combined with horizontal muscle surgery. Eighteen patients with infantile esotropia and V-pattern underwent bilateral inferior oblique recessions with bilateral 5.0-mm medial rectus recessions. Sixty-one patients with infantile esotropia underwent bilateral 5.0-mm medial rectus recessions alone. At 2 years' follow-up, the patients who had undergone medial rectus recessions alone showed, on average, 12.9 dioptres more reduction in esodeviation at distance and 13.4 dioptres more reduction at near in primary position than did those who had undergone 4-muscle surgery (P = 0.03). Only 2 of the 18 patients (11%) who had undergone 4-muscle surgery developed an A-pattern postoperatively.

Postoperative drifts after adjustable-suture strabismus surgery.

OBJECTIVE: To determine the drift patterns and success rates of adjustable-suture horizontal strabismus surgery when patients are aligned to predetermined target angles. DESIGN: Case series. SETTING: University-affiliated tertiary care hospital in Toronto; clinic and office care. PATIENTS: A total of 109 patients aged 15 to 72 years who underwent adjustablesuture strabismus surgery (primary procedure or reoperation) for esotropia or exotropia performed by one surgeon between 1990 and 1994 who were followed for at least 6 months. Their final postoperative angles were in the target ranges of under 4 prism dioptres (PD) for esotropia surgery and 3 PD to 7 PD of esotropia for exotropia surgery. OUTCOME MEASURES: Primary-position alignment before surgery, immediately after surgery or after adjustment of sutures, if needed (final alignment), and at 1 to 2 weeks, 6 to 8 weeks and 6 to 8 months after surgery; size and direction of drift from final alignment after surgery at 6 to 8 months; and rate at 6 to 8 months of reduction of strabismus angle to less than 10 PD. RESULTS: Of the 109 patients 44 had esotropia (17 primary repair [group 1] and 27 reoperation [group 2]) and 65 had exotropia (29 primary repair [group 3] and 36 reoperation [group 4]). Overall, 48 patients (44.0%) required postoperative suture adjustment. The mean drifts from the final postoperative alignments were 1 PD for groups 1 and 2, 7 PD for group 3 and 3 PD for group 4, all in the exotropic direction. The corresponding surgical success rates were 82.4%, 92.6%, 93.1% and 94.4%. Over 6 to 8 months both esotropia groups had approximately equal tendencies to drift in either direction. Both exotropia groups showed almost equal tendencies to drift in either direction away from the mean exotropic shift for the group. CONCLUSIONS: Because of our target alignments, our success rates at 6 to 8 months were high, for both primary surgery and reoperation. In all four patient groups the drift tendencies were symmetric about the mean.