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Four patients with dissociated horizontal deviation (DHD) are described and an explanation of their horizontal comitant deviations is offered. The patients had asymmetric comitant horizontal deviations dependent on the fixing eye. All of them had unequal visual acuity (VA) and asymmetric manifest latent nystagmus (MLN) documented with eye movement recordings. The subjects appear to use convergence to reduce their nystagmus when viewing with the eye having more severe nystagmus and hence poorer vision. When patients viewed with the eye having less nystagmus, little or no convergence was exhibited. We suggest that DHD may be the manifestation of an asymmetric nystagmus blockage syndrome (NBS). The dampening effect of convergence on nystagmus has been well documented in the past and seems to apply here. The patients demonstrate that a true, but asymmetric NBS, can be found with MLN.

Forty-nine patients, ranging in age from 12 to 77 years, underwent strabismus surgery under local anesthesia. With standard preoperative medication and a retrobulbar injection of 2% mepivacaine hydrochloride (hyaluronidase added in 12 patients), effective anesthesia was obtained. Twenty-four patients were observed during the immediate postoperative period, and return of extraocular muscle function and visual acuity was found to be complete an average of 3.8 hours after the injection. The addition of hyaluronidase significantly altered the duration of the anesthetic. Local anesthesia may be a preferable technique in terms of decreased morbidity, especially in the older patient. The short duration of anesthesia and lack of side effects also enable the surgeon to use adjustable sutures and make the final adjustment relatively early in the postoperative period.

Fifty patients with 8 prism diopters or less of esotropia after the last surgery were studied. Forty-nine percent of those straightened before 12 months of age and 41% of those straightened between 13-24 months developed the M.S. Only one of the 22 patients straightened after the age of two developed the M.S. Although D.V.D. and overaction of the inferior oblique muscles were associated findings, neither precluded the development of the M.S. Those patients without M.S. had a higher incidence of subsequent exotropia and manifest D.V.D.

The success rate of large (6 and 7 mm) bimedial rectus recessions in 45 congenital esotropes with deviations of 50 prism dioptres or greater was found to be 91%. Judgment of final alignment was made six weeks postoperatively, with an average follow-up of 13 months. Large bimedial rectus recessions are an effective surgical treatment for congenital esotropia. This procedure does not significantly alter adduction, and leaves other muscles available should further surgery be necessary. These findings show that initial surgery on three or more muscles is unnecessary in congenital esotropia.

Maternal drug abuse during pregnancy exposes the fetus to the possibility of toxic or addicting effects. At a methadone hydrochloride maintenance program providing medical care to drug-dependent women and their infants, ophthalmologic examinations of all infants born during a 36-month period were performed. Twenty-nine infants prenatally exposed to psychoactive drugs were seen at birth and on follow-up. The 24% prevalence of strabismus found in the drug-exposed infants was significantly greater than that of 2.8% to 5.3% reported in the general population. These data suggest that maternal drug abuse and increased methadone dosage during pregnancy may predispose infants to the development of strabismus.

Forty-two patients underwent strabismus surgery with a retrobulbar injection of 3% chloroprocaine hydrochloride. In the 18 patients who were followed up in the immediate postoperative period, the average duration of action of 3% chloroprocaine was found to be 2.13 hours. In addition to the advantages of local anesthesia, this short-acting anesthetic permits earlier modifications of adjustable sutures and the earlier discharge of patients on the same day as surgery.

It is not only possible but safe to exceed the traditional 5 mm maximum recession of each medial rectus muscle to correct large angle esotropia. It is possible to grade the amount of recession to the preoperative deviation, similar to that which is done for esotropia less than 35 prism diopters. The results of this series indicate that alignment to within 10 prism diopters with one procedure is more likely by large recessions of the medial rectus than by other approaches. If a reoperation is necessary, there still remain two other untouched horizontal muscles on which to operate.

Ninety-seven patients with congenital esotropia with deviations of 50 prism dioptres or greater underwent large (6 and 7 mm) bimedial rectus recessions. The overall success rate with one operation was 83.5%. Judgment of final alignment was made at the last follow-up examination, six to 61 months (average 23.4 months) postoperatively. Large bimedial rectus recessions for congenital esotropia are an effective surgical treatment which does not significantly alter adduction.

A study was conducted using a group of congenital esotropes who had an adequate surgical alignment prior to 18 months of age, to determine how many of them would redevelop esotropia. In the group that redeveloped the condition, a high percentage of the esotropia was accommodative in nature and was therefore able to be corrected with spectacles. Both the initial refractive error and changes in refractive error were noted to be significant. This study emphasizes the importance of monitoring the refractive state continuously, especially in children with subnormal fusion.

In summary, 22 patients have been presented who have undergone lateral rectus recessions ranging from 8 to 14 millimeters. The overall cosmetic success rate (plus or minus 15 diopters of orthophoria) was 77%. Eight of these patients had unilateral recession-resection procedures. Surgically created incomitance ranged from 3 millimeters to 6 millimeters and correlated only poorly with the amount of surgery performed. None of the patients complained of cosmetic or symptomatic effects of the lateral incomitancy induced. We have restricted surgery of the large angle exotrope to a single, two-muscle procedure, thereby decreasing patient morbidity. It is therefore our recommendation that surgery for large angle exotropia be restricted to two horizontal muscles.

Fifty patients with 8 prism diopters or less of esotropia after the last surgery were studied. Forty-nine percent of those straightened before 12 months of age and 41% of those straightened between 13-24 months developed the M.S. Only one of 22 patients straightened after the age of two developed the M.S. Although D.V.D and overaction of the inferior oblique muscles were associated findings, neither precluded the development of the M.S. Those patients without M.S. had a higher incidence of subsequent exotropia and manifest D.V.D.

To determine causative factors of persistent strabismus presenting after cataract surgery, the surgical techniques and subsequent motility findings of eight patients who had persistent postoperative strabismus were studied. In two of the eight patients, complications related to the placement of the bridle suture were believed causative based on subsequent surgical findings. A similar etiology could be speculated in an additional three patients. An isolated vascular accident coincident to the cataract operation could account for a sixth case. The final two patients were believed to have a decompensated congenital fourth nerve palsy. In no patients could the myotoxic effect of a local anesthetic or the hypoxic effect of an ocular pressure-reduction device plausibly account for the deviation.

The results of bilateral medial rectus rerecession and bilateral lateral rectus resection for patients with undercorrected or recurrent esotropia after medial rectus recession are compared. Medial rectus rerecession resulted in a high rate of consecutive exotropia. Lateral rectus resection was more accurate but was often accompanied by undercorrection. Minimal millimeter amounts of rerecession yielded large diopter results. Except in cases where medial restrictive factors or obvious errors in magnitude of the original surgery are noted, we feel that bilateral lateral rectus resection is the surgery of choice in patients with recurrent or undercorrected esotropia following medial rectus recession.