Binocular vision & strabismus quarterly最新文献

Introduction: Changes in refractive error after strabismus surgery occur secondary to changes in corneal curvature. The change in refractive error is usually transient but may lead to a temporary decrease in vision. We compared the change in corneal curvature following strabismus surgery in eyes utilizing a suspension (so-called "hang-back") recession technique to eyes undergoing conventional recession surgery.

Methods: Sixteen patients undergoing bilateral medial or lateral rectus recessions were prospectively entered into the study. One eye was randomly selected to undergo conventional strabismus surgery and the other eye underwent strabismus surgery using the suspension technique. Keratometry measurements were taken in the operating room immediately prior to and immediately after surgery. The change in corneal curvature was calculated and analyzed for each technique.

Results: The mean change in corneal curvature was -0.06 diopters (D) for the suspension group and +0.18 D for the conventional group, confirming prior reports. However, all eyes undergoing suspension surgery had a change within 1 D whereas only 75% of those eyes undergoing conventional surgery fell within the same range. Overall there was twice the variation in the degree of astigmatism in the conventional group when compared with the suspension group.

Conclusions: No eye undergoing suspension surgery experienced a change in corneal curvature greater than 1 D while 25% of those undergoing conventional surgery did. Therefore, possible benefits to the suspension recession technique might include less overall variability of astigmatism change and decreased amounts of induced astigmatism. Patients undergoing strabismus surgery using a suspension technique may be less likely to notice a change in their vision in the immediate postoperative period.

Patients with long-standing unilateral strabismus, such as "sensory" exotropia in the absence of fusion, or esotropia with unilateral amblyopia, typically show bilateral deviations under anesthesia, often symmetric. Forced ductions usually show symmetric muscle tightness. Changes in extraocular muscle lengths thus appear to occur primarily bilaterally, whether fusion is present or not. With skeletal muscles responding to changes in stimulation by the gain or loss of sarcomeres, it is likely that abnormal or unguided vergence tonus, which changes the lengths of the extraocular muscles bilaterally, is largely responsible for changes in the angle of strabismus over time. This mechanism helps explain the development of [1] increasing "basic" deviations in accommodative esotropia; [2] torsional deviations with apparent oblique muscle "overaction/underaction" and A and V patterns; [3] recurrent esotropia with early presbyopia; [4] occasional divergence insufficiency in presbyopes; and [5] basic cyclovertical deviations that mimic superior oblique muscle paresis.

Background and purpose: Recession of a single medial rectus muscle may be appropriate for certain cases of esotropia. However, the procedure has not been widely accepted nor widely studied, and most reports have dealt with conventional recessions (3.5-6 mm) for small angle esotropia. We reviewed our patients who underwent unilateral supramaximal (6-8 mm) medial rectus recession for both small and medium angle esotropia.

Design: Observational case series.

Methods: The records of 56 consecutive patients, undergoing single eye muscle surgery for esotropia, ranging in age from 1 to 11 years were selected and analyzed. All patients had a constant esotropia, despite full cycloplegic refractive correction, measuring 15-40 prism diopters (mean=25.82) at distance and 18-45 prism diopters (mean=30.71) at near. Each patient underwent a graded unilateral medial rectus recession of 6-8 mm.

Results: 48/56 (86%) patients achieved "successful" binocular motor alignment (defined as 0-8 prism diopters residual esotropia at the most recent postoperative visit with a minimum of 5 months and an average of 32 months postoperative followup). The average unilateral medial rectus recession performed was 7.4 mm. Five patients (9%) were overcorrected, (defined as any amount of consecutive exodeviation).

Conclusion: Unilateral supramaximal medial rectus recession appears to be a safe and effective treatment for medium angle non-accommodative esotropia, and has advantages for both patient and surgeon.

Background and purpose: Diplopia is an infrequent complication described for retrobulbar local anesthesia. The objective of this study is to report the clinical characteristics and treatments for this surgical complication.

Methods: Retrospective study of medical records.

Period: 5.3 years ending February 2005. During this period, 20453 cataract surgeries were performed. The anesthesia used was retrobulbar block with ropivacaine diluted with hyaluronidase. Nineteen patients reported diplopia due to strabismus after the cataract surgical procedure and were referred for evaluation at the Extrinsic Ocular Motility Department.

Results: Persistent diplopia after cataract surgery occurred in 19 (0.093%) of the 20453 cases. The types of deviations found were: exotropia (n=3), esotropia (n=5), hypertropia (n=1), exotropia + hypertropia (n=5) and esotropia + hypertropia (n=5). Small deviations and dysfunction of the lateral rectus muscles were most commonly seen. Prism was applied to 4 patients, eye muscle surgery was the option in 8 patients, orthoptic treatment was performed in 3 patients and for 2 patients the decision was to only observe progress. Overall, binocular vision was restored in eleven of the nineteen patients.

Conclusions: Persistent diplopia due to strabismus is an infrequent complication after cataract surgery with retrobulbar block. Etiology of this disorder of extrinsic ocular motility is variable, including mixed components. We stress the importance of adequate preoperative history of strabismus and evaluation of extrinsic ocular motility. Considering the reported incidence of this problem is as high as one in 25 cataract surgeries, one should advise the patient of the possibility of persistent postoperative diplopia and the possible need for surgical intervention and/or prism to treat the symptoms.

Introduction: Statistical Process Control (SPC) techniques were originally used for evaluating quality in manufacturing. The SPC chart consists of data plotted in a time sequence with the mean and upper and lower control limits (approximates +/- 3 standard deviations), graphically showing trends in the data. We employed SPC charts to analyze one and two muscle surgery for simple horizontal strabismus of 25 prism diopters (PD) or less.

Methods: We reviewed the records of 47 patients, 18 years and younger with consistent preoperative strabismus measurements of 25 PD or less, who underwent pure horizontal rectus muscle recession, resection, or both. SPC charts were used to compare the differences in preoperative and postoperative measurements of one muscle versus two muscle esotropia and exotropia using the QI analyst software package.

Results: The average preoperative measurements for esotropia were 19.6 PD of one muscle cases, and 23.8 PD for two muscle cases. For exotropia, these values were 16.7 PD for one muscle cases and 20.6 PD for two muscle cases. The average postoperative measurements for esotropia were 5.4 PD for one muscle cases, and 10.0 PD for two muscles cases. For exotropia, the values were 2.2 PD for one muscle cases, and 11.0 PD for two muscle cases. SPC charts displaying pre- and postoperative measurements for one and two muscle surgery for both esotropia and exotropia showed normal statistical fluctuation. Interestingly, two muscle postoperative measurements for both esotropia and exotropia had higher upper control limits (UCL) than one muscle measurements. Those patients requiring additional surgery, or whose postoperative measurements were greater than 15 PD were considered failed cases. The differences in failure rates between one muscle and two muscle cases were not "statistically significant" [p less than 0.05].

Conclusion: One muscle horizontal rectus surgery should be considered as an option when planning surgical treatment for medium angle strabismus. Statistical process control may be a valuable method to analyze variability in many ophthalmologic procedures, with the goal of minimizing variability to achieve better outcome.

Purpose: While excimer laser refractive surgery is recommended and highly successful for correcting refractive errors in adults, its use in children has not been extensively exercised or studied. We report our experience treating children with amblyopia due to high anisometropia, high astigmatism, high myopia and with associated developmental delay.

Setting: Review of patient records of our refractive clinic.

Methods: A retrospective review was made of all 11 children with stable refractive errors who were unsuccessfully treated non-surgically and then underwent corneal refractive surgery and in one case, lenticular surgery. Seven had high myopic anisometropia, 2 had high astigmatism, and two had high myopia--one with Down's Syndrome and one with agenesis of the corpus callosum.

Results: The surgical refractive treatment eliminated or reduced the anisometropia, reduced the astigmatic error, improved vision and improved the daily function of the children with developmental delay. There were no complications or untoward results.

Conclusions: Refractive surgery is safe and effective in treating children with high myopic anisometropia, high astigmatism, high myopia and developmental delay due to the resulting poor vision. Surgery can improve visual acuity in amblyopia not responding to routine treatment by correcting the refractive error and refractive aberrations.