Stephen P. Kraft

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.

Intraorbital Wood: Detection by Magnetic Resonance Imaging

The authors present two cases in which intraorbital wooden foreign bodies remained undetected after initial ophthalmologic examination and radiologic investigation which included plain orbital x-rays, orbital computed tomography (CT) scans, and, in one case, orbital ultrasound. In each case, subsequent magnetic resonance imaging (MRI) showed a well-delineated low-intensity lesion suggestive of a retained foreign body. Investigation of a case of suspected wooden foreign body in the orbit should include an MRI scan if there is no contraindication, and no foreign body has been defined on CT scan, ultrasound, or plain orbital films.

Stability of the Postoperative Alignment in Adjustable-Suture Strabismus Surgery

We reviewed the postoperative alignment drift in 201 patients between the ages of 14 and 75 years who underwent rectus muscle surgery with adjustable sutures from 1984 to 1989. We analyzed results for 42 primary esotropia (ET) surgeries and 37 reoperations (groups IA and IB, respectively), 34 exotropia (XT) primary surgeries and 66 reoperations (groups IIA and IIB, respectively), and 22 hypertropia (HT) surgeries (group III). Forty percent of patients required postoperative muscle adjustment. All patients underwent a minimum of 8-weeks follow up; 66% underwent 6-months follow up or longer. The postoperative drifts in alignment for primary surgeries versus reoperations were not significantly different for either ET or XT patients. The mean postoperative drift in prism diopters from the alignment immediately after the adjustment, or after the surgery if no adjustment was needed, for each group as measured during the most recent follow up was 1.3 eso-shift for group IA, 1.2 exo-shift for group IB, 4.8 exo-shift for group IIA, 4.1 exo-shift for group IIB, and 1.5 hyper-shift for group III. Only for groups IIA and IIB were these drifts found to differ significantly from zero. Based on these drift patterns, we align ET patients to orthotropia, XT patients to 5 to 7 delta esotropic, and HT patients to 1 to 2 delta hypotropic positions.

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.

A Surgical Approach for Duane Syndrome

Duane retraction syndrome (DRS) represents a spectrum of motility disorders in which the common feature is retraction of the affected eye on attempted adduction. Electrophysiologic and neuropathologic studies have shown that the underlying cause is anomalous innervation of the lateral rectus with the medial rectus and, at times, with vertical muscles in the affected eye. Clinical abnormalities observed in DRS can include any or all of the following: a deviation in the primary position; abnormal head position; severe retraction causing a pseudoptosis; and upshoots and/or downshoots associated with A, V, or X patterns. A surgical approach based on the analysis of these four features is presented, allowing the surgeon to devise an appropriate, individualized plan for a given case which can yield optimal results in one operation.

Long-term Changes in Duration of Relief with Botulinum Toxin Treatment of Essential Blepharospasm and Hemifacial Spasm*

PURPOSE To determine long-term changes in duration of relief with serial treatments of botulinum A toxin (BAT) used to treat benign essential blepharospasm and hemifacial spasm, in view of conflicting reports as to whether BAT has an increasing, decreasing, or an unchanging duration of effect over a long period of treatment. METHODS Thirty-two patients with facial dyskinesia (20 with essential blepharospasm, 12 with hemifacial spasm) were followed between 5 and 9 years through a mean of 18 (range, 12-32) BAT treatments with prospective documentation of intervals of relief from symptoms. Repeated measures and linear regression analyses were used to determine trends in each group. RESULTS Marked inter- and intrapatient variability was found in the length of effect of BAT. Statistical analysis showed no significant changes in mean duration of relief within each group (P = 0.65 for essential blepharospasm, 0.36 for hemifacial spasm). There was a trend to slow decline in the interval of relief, especially in patients with an initial duration of effect greater than 150 days. No relation was found between duration of relief and age or sex of patient or grade and duration of disease before initial treatment. CONCLUSION In the long term, the mean duration of relief from symptoms with BAT changes little over a period of serial treatments. Short-term fluctuations in the length of therapeutic effect did not indicate the development of a resistance to treatment.

The development of optokinetic nystagmus in strabismic and monocularly enucleated subjects

Assymmetries of monocular optokinetic nystagmus (OKN) following anomalous visual experience are thought to be due to disruption at the cortical level. Visual disruption usually results from eye suture (in animals), unilateral dense and central cataracts or strabismus (in humans). Many form-deprived animals and humans frequently show a residual strabismus after lid opening (animals) or cataract extraction and optical correction (humans). We wanted to determine whether strabismus was unique in causing monocular asymmetries of OKN. Two independent observers rated eye movement videotapes of 20 normal subjects, the non-deviating eye of 25 unilateral strabismic subjects and 29 unilaterally eye-enucleated subjects, who were watching either a nasally directed square wave grating, a temporally directed square wave grating, or a blank field. Observers rated the proportion of trials where OKN occurred, the duration of OKN in each trial and the number of beats of OKN within each trial. Monocular OKN was symmetrical in normal subjects for the proportion and duration measures, but half the normal group showed small but significant asymmetries for the beats measure. Subjects in both enucleate and strabismic groups showed asymmetries of OKN favouring nasally directed stimulation, but only the early onset strabismics (as a group) showed asymmetries that were significantly greater (P less than 0.05) than the normal group. Asymmetry scores correlated significantly with age of diagnosis of strabismus for the strabismic group but not with age of enucleation for the enucleate group. The results are discussed in terms of binocular competition.

Crowding and Contrast in Amblyopia

The crowding effect, defined as the ratio of visual acuities for letters presented in Snellen (i.e., line) format and isolated-letter format, was measured in the amblyopic eyes of 15 children and 15 adults with unilateral amblyopia. Normal limits were based on data from 20 children and 20 adults with no history of amblyopia. The crowding effect was compared for letters of high (96%) contrast and for letters of low (11%) contrast. We report that amblyopia can differentially affect line and isolated-letter acuity for both high- and low-contrast letters. For the patients that show an abnormal crowding effect, this effect can be: (1) significantly stronger, (2) significantly weaker, or (3) not significantly different for high- than for low-contrast letters. These findings are consistent with the hypothesis that the crowding effect is contrast-dependent in some amblyopic eyes of both child and adult unilateral amblyopes

Improvement of Compensatory Head Postures after Strabismus Surgery

PURPOSE To determine the incidence and relative frequencies of orientations of compensatory head postures (CHP) and success in surgically treating the CHP seen in patients with pure lateral rectus paresis (group I), superior oblique paresis (group II), Duane syndrome (group III), Brown syndrome (group IV), and congenital motor nystagmus (group V). METHODS The authors retrospectively reviewed all patients assessed and treated between 1985 and 1991 with these five conditions. Frequencies and orientations of the CHP were determined in all patients in each group. The success of surgery in eliminating the CHP in the subgroups of patients who underwent surgery to treat the CHP also was determined. RESULTS The frequencies of CHP were 29.0% of 93 group I cases, 71.2% of 139 group II cases, 68.1% of 91 group III cases, 17.4% of 35 group IV cases, and all 23 group V cases, for an overall incidence of 56.7% of 381 patients. For patients who underwent surgery to eliminate a CHP, success rates were 85.7% of 21 group I cases, 75.6% of 41 group II cases, 87.2% of 47 group III cases, 100% of 5 group IV cases, and 78.3% of 23 group V patients, for an overall success rate of 82.5% of 137 surgical cases. CONCLUSION Because CHP is seen frequently in strabismus and nystagmus disorders, ocular causes must be ruled out in any case of an anomalous head posture. Appropriately planned surgery for CHP caused by incomitant strabismus or eccentric nystagmus null zones has a high rate of success in eliminating CHP.

Method for identifying amblyopes whose reduced line acuity is caused by defective selection and/or control of gaze

Three visual tests were administered to a group of 15 amblyopic children. 15 adult amblyopes and two age‐matched control groups, each of 20 subjects. Test results comprised visual acuity for recognizing high contrast letters presented in line (i.e. Snellen) Formal, isolated‐letter format and repeal‐letter format. The classical Snellen format confounds the effects of gaze control defects with the effects of adjacent contours on a patients ability to recognize a foveated letter. We designed a repeat‐letter format intended to unconfound these effects. The repeal letter formal is much less sensitive to gaze control defects, and somewhat more sensitive to adjacent contour interactions than is the Snellen format. We report that amblyopic eyes can he subdivided empirically into three repeat‐letter categories: repeat‐letter acuity significantly better than Snellen acuity; repeat letter acuity not significantly, different from Snellen acuity: and repeal letter acuity significantly worse than Snellen acuity. We report that this subdivision cuts across the clinical subclassification of amblyopic and also across the crowding no crowding subclassification. We suggest that, rather than abnormal lateral interactions, defective selection and or control of gaze is an important factor in depressed visual acuity in amblyopic eyes of the first repeal‐letter category but not for the third type, in which abnormal lateral interactions may be important. To test the hypothesis that the response to patching and refractive therapy may be less satisfactory in our first category of amblyopic eyes, we are carrying out a prospective study. If the hypothesis is confirmed, it might then he worthwhile to identify these patients at an early stage and investigate whether therapies designed to improve the control of gaze might be more effective in this group than is patching or refractive therapy.