The Surgical Correction of Vertical Deviation after Superior Rectus Muscle Recession in Patients with Hypertropia

PURPOSE: In general, the amount of vertical rectus surgery is based on achieving 3 prism diopters (PD) of realignment for each millimeter of muscle recession. The study aimed to determine the surgical correction of vertical deviation in patients with hypertropia after superior rectus muscle recession. METHODS: A total of 32 patients with hypertropia underwent 2-8 mm recession of the superior rectus muscle. The average surgical correction for each millimeter of recession was calculated by deducting the post-surgical deviation from the pre-surgical vertical deviation and dividing the remnant by the amount of recession (mm). RESULTS: The average surgical correction was 2.2 +/- 0.7 PD for each millimeter of superior rectus recession. There was no statistical significance in the change in surgical correction in terms of follow-up period, which was categorized as one day, one, two, and six months, and one year (P>0.05). The relationship between surgical correction and age (below and above 11 years old), gender or the amount of recession (below or above 5 mm) was not statistically significant (P>0.05). There was no statistically significant difference in vertical correction between esodeviation and exodeviation (P>0.05). CONCLUSIONS: The study showed an average surgical correction of vertical deviation of 2.2 PD for each millimeter of superior rectus muscle recession. The results suggest that increased recession, within the maximum limit of 8 mm, is an effective approach to prevent undercorrection for children who have hypertropia but cannot undergo adjustable strabismus surgery.

A Case of Convergent Strabismus Fixus with Invisible Cornea

PURPOSE: We report an example of successful operation of rare convergent strabismus fixus, which had previously been mistaken for orbital tumor in private clinics because of severe adduction with unseen cornea. METHODS: A 57-year-old woman had convergent strabismus fixus with inward deviation of the left eye that had gradually progressed since she was around 40. Her cornea was buried in the intraorbital rim. An eye movement examination revealed that the eyeball was fixed to the internal part and that eyeball movement was impossible in all directions. When the forced duction test was performed, strong resistance was shown in all directions when abducted. During surgery, the medial rectus muscle was disinserted after resection of 3.0 mm for the left eye, and lateral rectus muscle tucking of 11.0 mm for the left eye was conducted. Since there was resistance in the inferior oblique muscle by the forced duction test during the operation, inferior oblique muscle myectomy of 4.0 mm was simultaneously performed. RESULTS: In the forced duction test implemented immediately after the operation, resistance subsided considerably and eye movement was shown in all directions, with cosmetically satisfactory results. Optic atrophy was found in the fundus examination after the operation. CONCLUSIONS: Convergent strabismus fixus, which recurs frequently and causes severe limitation of eye movement, was changed from the primary position to orthophoria by medial rectus muscle resection with disinsertion and lateral rectus muscle tucking. The eye movement disorder was improved and a satisfactory result was obtained.

Paralytic Exotropia from Pit Viper Snakebite

PURPOSE: The authors report their experience with four cases of paralytic exotropia from a pit viper snakebite, accompanied with a literature review. METHODS: Four patients (two males and two females) visited the emergency room in the hospital with symptoms including diplopia, limitation of eye movement, exotropia, and blepharoptosis, after being bitten by a presumed pit viper, and were treated by antivenom. RESULTS: No visual disturbance was observed in the first examination, while limitation of adduction was found in four cases in the ocular movement test. As to the type of tropia, three patients showed intermittent exotropia and the other showed exotropia. The angle of strabismus in the distance was 20~30 prism diopters (PD) while that in the near was 18~35 PD. Two cases were accompanied with blepharoptosis. Except one case which was unavailable for follow-up observation, three cases became normal in diplopia, blepharoptosis, and limitation of ocular movement between the 4th and 11th day after the snakebite. CONCLUSIONS: Neurotoxicity induced by a pit viper snakebite is rare. However, neurotoxicity including strabismus and blepharoptosis can occur because extraocular muscles have a higher ratio of nerve fibers to the extraocular muscle fibers compared with skeletal muscles.