Gary L. Rogers

Management of Strabismus with Botulinum A Toxin

Three hundred eight patients with strabismus were treated with botulinum A toxin (Oculinum) chemodenervation; 153 were followed by the authors for at least 6 months. In this study group, 97 received botulinum A toxin injections as the primary method of treatment of their ocular deviation. Fifty-six received injections after traditional extraocular muscle surgery. Botulinum A toxin was useful for management of patients with recent surgical overcorrections and for management of some patients with sixth cranial nerve palsy. Chemodenervation of an extraocular muscle was not as successful as traditional strabismus surgery for treatment of infantile esotropia and other comitant deviations. Botulinum A toxin injection was ineffective in patients who had restrictive strabismus. This drug has limited application in the management of patients with strabismus.

Treatment of Corneal Opacification in Mucolipidosis iv with Conjunctival Transplantation

Mucolipidosis IV is a rare, inherited metabolic storage disease producing progressive psychomotor retardation and congenital corneal clouding. Histopathologic studies have shown that the corneal epithelium is strikingly involved with intracytoplasmic vacuolated storage material with relative noninvolvement of the corneal stroma and endothelium. Additionally, it has been noted that epithelial removal results in corneal clarity. We treated a 28-month-old patient with mucolipidosis IV with conjunctival transplantation with donor conjunctiva from an unaffected sibling. Improved corneal clarity resulted and has persisted with a follow-up of one year.

Instruction Dependent Activation during Optokinetic Nystagmus (OKN) Stimulation: An FMRI Study at 3 T

Modifying experimental conditions of optokinetic nystagmus (OKN) result in different outcomes and may not optimally translate into clinical testing. The purpose of this study was to assess the influence of subject instruction on the anatomical correlates of OKN. The instructions were to voluntarily look or stare at the same moving grating with fixed contrast and spatial and temporal frequencies. Look and stare OKN were generated under identical stimulus ON conditions (vertical sine wave grating of 1.14c/deg drifting right to left at 11.4c/s with binocular viewing). FMRI was undertaken utilizing a 3.0T GE system and the BOLD technique. Subjects included 6 normal adults ranging in age from 18 to 54 years with normal visual acuity (20/20 or better) and normal stereoacuity (40s of arc or better). The results reveal that look OKN generated significantly more cortical FMRI activation than stare OKN. Look OKN areas included the culmen, parahippocampal, lingual, middle temporal gyri, inferior and superior parietal lobules and precuneus, all of which were unilaterally activated in the left hemisphere. The middle occipital gyrus was unilaterally activated in the right hemisphere while the cuneus was bilaterally activated. These results show that the activation sites for OKN studies are dependent on subject instruction which influence the type of OKN generated. Specifically, voluntary look OKN involved more brain sites than stare OKN. In so doing, we illustrate the importance of subject instruction and recommend that FMRI investigators of OKN be cognizant of these effects. The anatomical correlates of the look versus stare are discussed.

A comparison of cryotherapy versus diode laser retinopexy in 100 consecutive infants treated for threshold retinopathy of prematurity.

PURPOSEnThe purpose of this paper is to present a series of patients who were treated for threshold retinopathy of prematurity with either cryotherapy or diode laser. Complications and unfavorable outcomes during the first year after treatment will be compared for the two procedures.nnnMETHODSnThe clinical courses of a consecutive series of 100 infants (192 eyes) were reviewed. All infants had their threshold status confirmed by a second examiner. Infants were treated with cryotherapy through 1993 and with diode laser thereafter. One hundred two eyes of 54 patients were treated with cryotherapy. Ninety eyes of 46 patients were treated with laser retinopexy. Two of the patients who were treated with laser (4 eyes) did not survive to the 3-month follow-up visit, and their results are not included here. The two groups of infants were comparable in their birth weight, adjusted gestational age at treatment, and severity of disease as determined by zone and sectors of stage 3 retinopathy of prematurity.nnnRESULTSnUnfavorable outcome (total retinal detachment) was seen in 25.4% of eyes treated with cryotherapy (26 of 102), as compared with 15% of eyes treated with laser (13 of 86). Two cataracts were seen in our patients: one patient 22 weeks after cryotherapy, and the other 7 months after diode laser.nnnCONCLUSIONSnNo statistically significant difference was found in the rate of retinal detachments in the two groups (X2 = 3.05; P = .08).

Relationship among fMRI, contrast sensitivity and visual acuity

The purpose of this study was to ascertain whether visual acuity or contrast sensitivity function (CSF) is proportional to visual cortical function based on fMRI volume and level of activation or Z-score. Forced choice procedures were utilized to measure the monocular log minimal angle of resolution (logMAR) visual acuity and CSF. The CSF data were collapsed into a single index by the use of weighted mean contrast sensitivity (WMCS), being defined as the mean of the products of each spatial frequency multiplied by its corresponding contrast sensitivity. fMRI data had been obtained with a 1.5 T GE Signa scanner with visual stimuli including 1.0 and 2.0 c/deg vertical sinusoidal gratings. Subjects consisted of eight normal adults and five amblyopic patients, with the amblyopic subjects added to gauge whether the outcome was due to a restricted range of scores or the small number of study participants. In normal subjects, the fMRI volume and level of activation exhibited no statistically significant correlation with visual acuity at P<0.05. Statistically significant correlations were obtained between WMCS and fMRI volume (R=0.765, P=0.027) and fMRI level of activation (R=0.645, P=0.007), with right eye stimulation using the 1.0 c/deg grating. On the whole, statistically significant correlations between WMCS and fMRI parameters were maintained when subject age was held constant and when data from the five amblyopic subjects were included to expand the range of values and increase the number of data sets for analysis. fMRI volume and Z-score were more closely associated with the CSF, as defined by WMCS, than visual acuity. The results suggest that the CSF reflects the underlying visual cortical cells responsible for fMRI volume and the level of activation.

The effect of surgical preparation technique on the bacterial load of surgical needles and suture material used during strabismus surgery

PURPOSEnTo investigate the effectiveness of 3 surgical preparation techniques in decreasing bacterial contamination of needles and suture material during strabismus surgery.nnnMETHODSnConsecutive patients requiring 2-muscle strabismus surgery were randomized into 1 of 3 groups. In Group A, patients periocular skin and bulbar conjunctivae underwent preparation with 5% povidone-iodine; the drape was placed without regard to eyebrows; and an open wire-loop lid speculum was used. Group B patients underwent the same preparation as Group A patients; however, the eyelashes and eyebrows were scrubbed with 5% povidone-iodine on cotton tip applicators, and the drape was placed to exclude the eyebrows from the surgical field. Group C patients underwent the same preparation as Group B patients; however, a bladed lid speculum was used during surgery to exclude some of the eyelashes from the surgical field. After the procedure, all needles and suture materials were sent separately for aerobic culture. The data were analyzed for differences in contamination rates between the groups.nnnRESULTSnOf 77 patients, 24 (31.4%) had either a needle and/or suture contaminant. Groups A, B, and C had mean contamination rates of 29.6%, 34.6%, and 29.2%, respectively. There was no significant statistical variation in contamination among the 3 groups. The most common organism identified was a coagulase-negative staphylococcus strain.nnnCONCLUSIONSnMore meticulous sterile preparation of the surgical field did not result in a meaningful reduction in suture or needle contamination rates during strabismus surgery.

Corneal power measurements in fixating versus anesthetized nonfixating children using a handheld keratometer

PURPOSEnTo compare keratometry measurements on a fixating patient with readings from the same nonfixating patient intraoperatively using the Nidek KM-500 handheld keratometer.nnnMETHODSnConsecutive patients who were scheduled for strabismus or nasolacrimal surgery between 5 and 11 years of age were included in the study. Handheld keratometry was performed preoperatively on both eyes with the child fixating and intraoperatively with the child anesthetized. Three readings were taken on each eye. The steepest and flattest corneal meridians were recorded. Intraclass correlation coefficients were calculated to assess reliability, and interchangeability was assessed by the use of the Bland-Altman method.nnnRESULTSnIncluded in the study were 55 eyes of 28 patients. The average fixating keratometry reading was 44.10 +/- 1.45 D for right eyes and 44.12 +/- 1.42 D for left eyes. The average nonfixating keratometry reading was 44.06 +/- 1.62 D for right eyes and 44.02 +/- 1.54 D for left eyes. The intraclass correlation coefficient for the average keratometry obtained fixating versus nonfixating was 0.96 for right eyes and 0.95 for left eyes. The Bland-Altman analysis showed fairly large limits of agreement between readings, but most readings fall within the limits of variability. The mean time to obtain the intraoperative measurements was 4.26 minutes.nnnCONCLUSIONSnIn our study the Nidek KM-500 handheld keratometer provided reliable readings when used intraoperatively on anesthetized nonfixating children and required minimal time to perform.

Levodopa-carbidopa and childhood retinal disease

PURPOSEnOur purpose was to determine the influence of levodopa-carbidopa on visual function in children with retinal disease.nnnMETHODnTwo studies were undertaken, a single-dose study and a longitudinal dosing study. A double-masked, placebo controlled single-dose study was undertaken of levodopa-carbidopa (2.08 mg/kg of body weight levodopa with 25% carbidopa) on monocular visual acuity in 14 children with retinal disease. Subjects received two capsules approximately 2.5 hours apart, and monocular visual acuity was measured 2 hours after each capsule ingestion. The second study was a double-masked, placebo-controlled 12-week longitudinal dosing (0.62 mg/kg of body weight) crossover study in which subjects received levodopa-carbidopa for 6 weeks and placebo for 6 weeks.nnnRESULTSnThe single-dose study revealed a small but statistically significant improvement in monocular visual acuity after levodopa-carbidopa ingestion. The longitudinal study revealed a small but statistically significant improvement in binocular visual acuity after levodopa ingestion. In both studies placebo had no significant effect on visual acuity. Six subjects participated in both studies and demonstrated a significant correlation (r = 0.76, p < 0.05) between change in visual acuity in the single-dose study and the longitudinal dosing study.nnnCONCLUSIONnThe results are consistent with the hypothesis that dopamine influences the receptive field characteristics of retinal cells. The results also suggest that there may be low retinal dopamine levels in some types of retinal disease, which may be amenable to treatment.