Mechanisms of Vertical Fusional Vergence in Patients With "Congenital Superior Oblique Paresis" Investigated With an Eye-Tracking Haploscope.

PURPOSE: To determine the mechanisms of vertical fusional vergence in patients with "congenital unilateral superior oblique paresis" (SOP) and to discuss the implications of these mechanisms. METHODS: Eleven patients were examined with our eye-tracking haploscope. RESULTS: Three different fusion mechanisms were found, producing significantly different cyclovergence to vertical vergence ratios (P < 0.05): primary use of the vertical rectus muscles in seven patients (ratio: 0.36 ± 1.6), primary use of the oblique muscles in one patient (0.04), and use of the superior oblique muscle in the higher eye and the superior rectus muscle in the lower eye in three patients (1.15 ± 0.32). Lancaster red-green testing showed alignment differences among these groups, primarily differences in amount of subjective extorsion between the two eyes in straight-ahead gaze: The patient with oblique-muscle-mediated fusion showed essentially no subjective extorsion (0.5°), the patients with vertical-rectus-muscle-mediated vertical fusion showed a mean ± SD subjective extorsion of 3.6° ± 1.4°, and the patients with the mixed (oblique/rectus) fusion mechanism showed 7.0° ± 1.7° (P < 0.05). CONCLUSIONS: The choice of fusion mechanism may be a function of how much intorting effect is needed. Use of the oblique muscles bilaterally causes the least intorting effect, use of the vertical rectus muscles bilaterally adds more intorting effect, and activation of the "paretic" superior oblique muscle in the higher eye and the superior rectus muscle in the lower eye provides the greatest intorting effect. Subclassifying "congenital SOP" in this way (in which the "paretic" muscle may remain functional in many cases) may help guide its optimal surgical correction.

Shewanella putrefaciens keratitis in the lamellar bed 6 years after LASIK.

PURPOSE: To present a case of infectious keratitis occurring 6 years after LASIK due to the rare human pathogen Shewanella putrefaciens. METHODS: A 58-year-old man presented with redness and pain in the right eye 6 years following LASIK retreatment. Examination revealed a corneal infiltrate at the flap interface. Corneal scraping of stroma beneath the flap was submitted for histopathologic and microbiologic evaluation. RESULTS: An infiltrate located at the LASIK flap interface originated from an epithelial defect at the flap-corneal junction. Corneal stroma cultures demonstrated Shewanella putrefaciens. The infection resolved with antibiotic treatment. CONCLUSIONS: LASIK-related complications, such as infections, can occur many years following the procedure. The potential space created under the LASIK flap may predispose patients to infection by opportunistic organisms.