Volume 13 Number 1 / February 2009 e7

025 Diffusion weighted imaging in the analysis of pediatric orbitaltumors. Lea Ann Lope, Kelly A. Hutcheson, Zarir Khademian

Purpose: To identify common radiographic features of pediatric or-bital tumors using magnetic resonance imaging (MRI) techniques,particularly diffusion weighted imaging (DWI), fat saturated FSE T2and pre- and post-gadolinium T1. DWI is hypothesized to help identifyand predict the malignancy of specific brain tumors. To our knowl-edge similar analysis has not been performed with pediatric orbitaltumors.

Methods: We performed a retrospective chart review at our insti-tution of all patients diagnosed with an orbital mass lesion, imaged byMRI using the aforementioned techniques. Twenty seven patientsmet inclusion criteria. We reviewed the MRI of these patients from2005 to 2008, when DWI was most likely to be routinely used. Masslesions included rhabdomyosarcoma (n 5 7), myofibroma (n 5 2),hemangioma (n 5 3), lymphangioma (n 5 1), eosinophilic histiocyto-sis (n 5 2), giant cell tumor (n 5 1), meningioma (n 5 1) lymphoid hy-perplasia of the lacrimal gland (n 5 2), neurofibroma (n 5 4), opticnerve glioma (n 5 1), lipodermoid (n 5 1), dermoid (n 5 1), and Lang-erhans histiocytosis (n 5 1).

Results: The fibrous orbital tumors, specifically orbital rhabdo-myosarcoma and myofibroma, demonstrate homogenous diffusionrestriction on DWI. In contrast, nonfibrous orbital lesions, suchas hemangiomas demonstrate no restriction on DWI, and eosino-philic histiocytosis show a predominance of diffusion restrictionwith interspersed areas of increased diffusion. On T1 after gadoli-nium administration, myofibromas show a unique thickened periph-eral enhancement with central hypointensity. The eosinophilichistiocytotic lesions show enhancement of the adjacent muscula-ture on T1 after gadolinium. Both findings are not seen in other tu-mors.

Conclusions: Our results give promise to diffusion weighted imag-ing and conventional MRI techniques, to provide identifying informa-tion on pediatric orbital tumors. Our study introduces a newapplication for this existing imaging technique, in hope of refiningthe differential diagnosis of such orbital tumors.

026 Exotropia after hemispherectomy. Iason S. Mantagos,Deborah K. VanderVeen

Introduction: Children with homonymous hemianopia often de-velop exotropia, which may be an adaptive mechanism to expandthe visual field. We evaluated the incidence of strabismus in patientswho have had hemispherectomy for intractable seizures at ourtertiary care institution.

Methods: A retrospective chart review of patients who had hemi-spherectomy from 1995 until 2008 and also were evaluated at theDepartment of Ophthalmology was performed. Age at hemispherec-tomy, and details of ophthalmologic evaluations including visual fieldassessment were collected.

Results: A total of 74 patients (17 female, 57 males) ages 6 monthsto 16 years at the time of hemispherectomy were identified; 34 ofthem also were evaluated by Ophthalmology. A total of 7 of 34patients had associated ocular comorbidities such as optic nerve co-lobomas, glaucoma, congenital cataracts. Of the patients without co-existing ocular abnormalities, 65% developed strabismus, whereas35% remained orthotropic, with a follow-up range of 6 to 60 months.Of the patients that developed strabismus 75% had exotropia, 8% hy-pertropia, and 17% esotropia. Patients with other ocular diagnosesdemonstrated various types of strabismus, and only 28% remainedorthotropic. No clear association between laterality of the surgicalsite, age at the time of surgery, or underlying diagnosis and maintai-nance of orthotropia was found.

Journal of AAPOS

Discussion: Hemispherectomy is an end-stage procedure for con-trol of intractable seizures and induces a homonymous hemianopia.We found a high rate of exotropia developing at various time intervalsafter hemispherectomy, and visual field testing confirmed expansionof the binocular visual field with the exotropic deviation.

Conclusions: Because exotropia after hemispherectomy is com-mon and adaptive, conservative management of their strabismusshould probably be considered.

027 Optokinetic nystagmus and sensorial tests in different typesof strabismus. Fatih Mehmet Mutlu, Alpay Demirel, Halil IbrahimAltinsoy

Purpose: To determine the relationship between the sensory fea-tures and monocular horizontal optokinetic nystagmus (OKN) asym-metry in different types of strabismus.

Methods: Forty-two esotropic, 37 exotropic, 10 Duane's syndrome(type 1), 11 congenital superior oblique palsy (SOP) cases with infan-tile-onset strabismus, and 15 healthy controls were included. Binocular-ity was tested with the Bagolini glasses, synoptophor, and the stereo-flyplate of theTitmus and Randot tests. OKN asymmetry was evaluated inthe dominant and nondominant eyes by using Barany drum (gradedfrom zero to +3) and videonystagmography (at velocities 20 and 30deg/s), and the correlation between these tests was assessed.

Results: Subjects with no binocularity showed a significant OKNasymmetry in both eyes (p 5 0.001; for both). OKN asymmetry wasfrequent in esotropics with poor or no binocularity. Although goodbinocularity was detected in exotropics, OKN asymmetry was signif-icant in exotropics with no binocularity. Good binocularity and sym-metric OKN along with low OKN gain in the affected eye weredetected in patients with Duane's syndrome. Excellent binocularityand symmetric OKN were found in SOP cases. OKN asymmetrywas frequent in amblyopic and strabismic subjects with DVD (p 5

0.001; for both). There were significant (p\0.001, for all) correlationsbetween asymmetry levels of Barany drum and asymmetry index ofvideonystagmography tests for each velocity in both eyes.

Conclusions: There is a relationship between binocularity andOKN asymmetry. OKN evaluation may be helpful to identify binocular-ity, and binocular potential in patients with strabismus. Barany drumcan be substituted for videonystagmography in clinical practice toevaluate OKN.

028 Strabismus surgery on the elderly and the effects ondisability. Kevin D. Merrill, Mary O'Hara, Denise Satterfield

Introduction: In 2005 this journal published an article by Beau-champ et al showing the effects that strabismus had on disabilityof adults. The age range of that study was from 19 to 87 years,with the average age being 54.9 years. Can these data be extrapo-lated to adults with an older age range, specifically the Medicarepopulation? The purpose of our study was to examine the effect ofstrabismus surgery on disability of adults in the Medicare age range.

Methods: A total of 56 consecutive patients older than 65 years ofage who had undergone strabismus surgery were asked to completea telephone questionnaire rating their before-surgery and after-sur-gery severity of various problems ranging from specific health, dailyfunctioning, social interaction problems, concerns about the future,and self-image to job-related problems. The questionnaire was thesame one given in the 2005 article so results could be compared.

Results: The problem ratings on all 6 items declined after surgery,with ''specific health'' and ''daily tasks'' yielding the highest percent-age of improvement. For all items, the number of patients indicatingan improvement was greater than the number of patients indicating