Evaluation of Vertical Rectus Muscle Insertions Using Ultrasound Biomicroscopy

Journal of AAPOS Volume 10 Number 1 February 2006 A New Removable Sliding Noose for Adjustable-Suture Strabismus Surgery Munish Sharma MD, MBBS, Kristina Tarczy-Hornoch MD, Dphil, David F. Klink DO, David L. Guyton MD; The Krieger Children’s Eye Center at the Wilmer Institute, Johns Hopkins University, Baltimore, MD Purpose: To describe a reliable sliding VicrylTM noose for use in postoperative suture adjustment of extraocular muscles that can be easily removed once adjustment has been completed. Methods: We have developed a removable noose based on a lark’s head knot (cow hitch) and have used it with a cul-de-sac conjunctival incision approach in over 500 patients in the last 3 years. Fashioning, applying, and removing the noose is best shown in a video presentation. Removing the noose leaves no excess suture material. The result is minimal inflammation, less discomfort, earlier healing, and less conjunctival scarring than with the conventional sliding noose, which cannot be removed. Results: The surgical alignment success rate with the new removable noose appears the same as with the conventional sliding VicrylTM noose. The noose was easily removed in all but five cases (⬃1%), the reasons for which will be enumerated. Conclusions: The removable sliding noose is a useful aide to small-incision, minimal-trauma, adjustable strabismus surgery. Evaluation of Vertical Rectus Muscle Insertions Using Ultrasound Biomicroscopy Carlos E. Solarte MD, Stephen Kraft MD, David Smith MD, Joseph R. Buncic MD, Nasrim Tehrani MD, Agnes Wong MD; Hospital for Sick Children, Toronto, Ontario, Canada Introduction: The ultrasound biomicroscope (UBM) has proven accurate in determining the position of horizontal extraocular muscles prior to strabismus surgery, for both primary surgeries and reoperations. Two previous studies compared horizontal rectus muscle measurements done with the UBM to the caliper at time of surgery (“gold standard”). In the current study we evaluated the accuracy of UBM in measuring the distance (mm) from limbus to the insertion of vertical rectus muscles (superior and inferior rectus). Methods: This prospective, masked, observational study of 40 vertical rectus muscle insertions compared the measurements from the limbus as measured by 50 MHz UBM, either preoperatively or at the time of anesthesia, with that measured by surgical caliper intraoperatively. Measurements (UBM and surgical) were evaluated by two different observers and analyzed using the Bland and Altman method. The Intraclass Correlation Coefficient (ICC) and the associated 95% confidence interval were used to quantify the degree of agreement between the two methods. Results: The UBM and surgical measurements have shown “good” correlation when allowing for a margin of error of ⫾1.0 mm between the two modalities. This indicates that the UBM is a good predictor of the position of the vertical rectus muscles. Conclusion: UBM can yield an accurate measurement of the position of the vertical rectus muscles, which is helpful in surgical planning. References: 1. Watts P, Smith D, MacKeen L, et al. Evaluation of the ultrasound biomicroscope in strabismus surgery. J AAPOS 2002;6(3):187-90. 2. Dai S, Kraft S, Smith D, et al. Ultrasound biomicroscopy in strabismus reoperations. Presented at AAPOS Meeting, Orlando, FL, March 2005.

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Unfavorable Outcomes after Strabismus Surgery Lisa S. Thompson MD, Fernanda Moreira MD, Kenneth W. Wright MD; Wright Foundation for Pediatric Ophthalmology, Los Angeles, CA Purpose: To determine the cause of unfavorable outcomes after strabismus surgery related to muscle dehiscence. Methods: Retrospective chart review of 143 consecutive patients who underwent reoperation strabismus surgery. History of onset, motility exam, and intraoperative findings was used to determine the cause of strabismus. These were classified as appropriate muscle attachment or muscle dehiscence (ie, slipped muscle, lost muscle, and stretched scar). Results: Thirty-four percent (48/143) of patients had muscle dehiscence, of which 27% were acute onset slipped or lost muscle, and 73% (35/48) were due to later-onset stretched scar. In each case, the type of muscle dehiscence helped to explain the pattern of the secondary strabismus. In those without muscle dehiscence the recurrent strabismus was attributable to periocular scarring (37%), fibrotic muscle (13%), and unknown etiology (50%). Conclusions: Muscle dehiscence and periocular scarring comprise a large and potentially preventable cause of unfavorable outcomes after strabismus surgery. This underscores the importance of surgical technique. Ocular Findings in Gillespie Syndrome: New Association with PAX-6 Mutation Benjamin H. Ticho MD, Clair Hilchie DO, Elias Traboulsi MD, David Robinson PhD; University of Illinois Eye and Ear Infirmary, Chicago, IL Background: Gillespie syndrome is a rare variant form of aniridia, characterized by mental retardation, nonprogressive cerebellar ataxia, and iris hypoplasia. Unlike the more common dominant and sporadic forms of aniridia, there have been no associated PAX6 mutations or Wilm’s tumor reported in Gillespie syndrome patients. Ocular findings in 21 cases published since Gillespie’s initial description in 1965 include iris and foveal hypoplasia, nystagmus, and small optic discs with pigmentary retinopathy. Case Presentation: We herein report a case of Gillespie syndrome associated with bilateral ptosis, exotropia, corectopia, iris hypoplasia, anterior capsular lens opacities, foveal hypoplasia, retinal vascular tortuosity, and retinal hypopigmentation. Sequencing studies revealed a substitution in intron 2 of the PAX6 gene. To our knowledge, this is the first mutation of PAX6 gene reported in association with Gillespie syndrome. We will review the phenotypic and genotypic variations between Gillespie syndrome and other forms of aniridia. Reference: Glaser T, et al. Absence of PAX6 gene mutations in Gillespie syndrome (partial aniridia, cerebellar ataxia, and mental retardation). Genomics 1994;19:145.