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Background: We have the impression that congenital aberrant innervations are more common than previously reported. Many varieties exist and typically involve the sixth nerve. The most common ocular miswjrings are Duane's syndrome and Marcus Gunn jaw-winking ptosis. The second most common miswiring involves lateral rectus activation in upgaze causing a "Y" pattern exotropia (pseudo inferior oblique overaction). This commonly is confused with inferior oblique overaction but surgery on the obliques does not cure the condition. Lateral rectus recession and elevation are required. Methods: We selected demonstrative cases from our practices to illustrate a variety of congenital aberrant innervations. A literature search for previous reported cases of aberrant innervations was performed. This report is an eclectic collection of observations of individual selected cases. Results: We found aberrant innervations of unusual varieties. These miswirings involve simultaneous firing of the lateral rectus with other muscles, including: the ipsilateral superior rectus, causing "pseudo inferior oblique overaction"; the contralateral lateral rectus, causing synergistic divergence; the ipsilateral superior rectus, in upward saccades only; and the masticatory muscles, causing exotropia with sucking. The third nerve by itself rarely is involved in congenital miswirings, but commonly shows aberrant regeneration after traumatic injuries. We know of no cases of aberrant innervation involving the fourth nerve. Summary: We present cases describing these congenital aberrant innervations and discuss a unifying hypothesis as to their typical involvement of the sixth nerve.

To determine the prevalence of ocular motility defects following placement of a Krupin valve with disk and adjunctive mitomycin-C in glaucoma patients, a retrospective case series of all patients receiving a Krupin valve with disk and intraoperative mitomycin-C in a university-based referral practice was conducted. Each of the seven consecutive patients undergoing placement of a Krupin valve with disk in one eye because of uncontrolled glaucoma, developed significant primary position heterotropia or limitation of ocular rotations. One patient had significant postoperative diplopia. We conclude that the Krupin valve with disk used with intraoperative mitomycin-C can be associated with the development of ocular motility defects. The limitation of rotations appears to relate to the combined mechanisms of implant and cyst bulk and the displacement of the oculorotary muscles by the encapsulating cyst.

Previous studies have suggested that the location of the equator should be important in determining the site of a "safe maximum recession" of a rectus muscle, and that the location of the equator should be a function of axial length. Exactly where in relationship to the equator a muscle can be safely recessed has never been scientifically determined. Over a 4-year period, we measured axial length on all patients we operated on for strabismus. Using a previously derived formula, we were able to calculate the limbus-to-equator distance, given axial length. Based on our analysis of 28 patients in whom we recessed one or both medial recti posterior to the equator, we believe that recessions of the medial recti up to 1.5 mm posterior to the equator should not produce postoperative medial rectus underaction associated with an overcorrection, but recessions that are further than 1.5 mm posterior to the equator may do so. Recessions to a point greater than 11 mm from the limbus do not appear to be associated with late progressive overcorrection provided that the site of recession is not greater than 1 .5 mm posterior to the equator. Using our previously determined formula for estimating the location of the equator, given axial length, we have generated easy-to-use reference tables for determining the location of the equator in terms of millimeters posterior to the limbus. Also, based on axial length data from 180 strabismus patients, we have generated an algorithm for predicting axial length, given age, and refractive error, which may be useful to the strabismus surgeon in predicting the location of the equator when A-scan ultrasonography is not available.

A technique is described by which subjects, using a Maddox rod, can subjectively appreciate the dynamic torsional movements that occur at the end of forced head tilt. The subjective responses of a large series of subjects with normal ocular motility confirm my previous observations that at the end of ipsilateral head tilt the eye is undergoing an extorsional movement and at the end of contralateral head tilt, an intorsional movement. Observations made in patients with oblique dysfunction confirm that the extorsional movements are largely produced by the inferior oblique and the intorsional movements by the superior oblique. This is consistent with the classic observation that a partial compensatory intorsion occurs after ipsilateral tilt, and extorsion after contralateral tilt, however, it suggests that this compensatory torsion occurs by a different mechanism than is classically taught. Patients with dissociated vertical divergence appear to have an abnormal response of the oblique muscles to change in head tilt.

The main effect of recession or resection of a rectus muscle is thought to be due to an alteration of its length-tension curve (Starlings Law). Because the subsequent straightening of the eye produces a movement of the new insertions of the rectus muscles either anteriorly or posteriorly in the orbit, the actual amount of tightening or shortening of the muscle is not equal to the amount of recession or resection. How much this phenonmenon alters the true amount of tightening or shortening of a muscle has important implications in the determination of safe amounts of surgery, which may differ if one is operating on the fixing or non-fixing eye. In addition, the size of the globe should have an important role in determing the response per millimeter of surgery.

SUMMARY Using a corneal marker and cinematography, we analyzed ocular torsionalmovementsduringforced head tilt in three patients with superior oblique palsy before and after i pallate r al inferior oblique recession and compared them to those of normal subjects. As the head is tilted in normal subjects, the eye lags behind the head in a slow rolling movement. Periodic rapid wheel-like movements occur in the direction of head tilt which do not completely allow the eye to catch up with the head. This results in a partial compensatory intorsion on ipsilateral head tilt and extorsion on contraiateral head tilt. In patients with superior oblique palsy, the rapid extorsional movement on ipsilateral head tilt is greater and faster than in the normal, but becomes slowerafter inferior oblique recession, indicating it comes from the o ver act ing inferió r oblique. The rapid into raion al move ment seen during contralateral head tilt is absent in patients with superior oblique palsy, but appears in a diminished form after inferior oblique recession.

I performed a posterior fixation of the medial rectus in seven patients with convergence excess esotropia and successfully reduced their esotropia at near. Postoperative saccadic velocity testing did not reveal the expected decrease in saccadic velocity as the eye moved increasingly into the field of action of the operated muscle. Posterior fixation of a rectus muscle may enhance the effect of the standard recession operation by increasing the amount of slack created in the functional part of the muscle after recession. Also, it may make a large percentage of the muscle fibers ineffective.

SUMMARY The use of a suture for large measurements during strabismus surgery is described. A piece of suture material cut to a length equal to the desired measurement is placed on the globe and used as a ruler.