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Eye
Muscle Surgery Qtrly°
Effectiveness of Surgery:
A comprehensive historical literature review of surgical correction for DEXT was conducted and reported in an optometric journal in 1985 by two optometrists Flax & Selenow (201).
They reviewed all XT surgical papers published from 1953 to December 1982. They eliminated from their review all papers which did not provide what they felt were clear or adequate presurgical and postsurgical results, adequate criteria for success. They also eliminated all papers where orthoptics were used in combination with surgery.
They located 22 papers which met their criteria cited above. This included reports on 1,490 patients.
Five studies reported analysis of binocular functional data and are reported in the top section of Tables V & VT, next page.
Of the 571 patients included in these five studies, 34% were functionally successful (“cured”), 27% were motorically aligned, and 16% were cosmetically acceptable. The aggregate cosmetic success (within 15 pd) was 78%, with less than half having good binocular vision postsurgically.
The 17 other studies provided in- complete postoperative fusional and/or sensory measurements which were insufficient to determine functional success according to the authors. These 17 studies contained the remaining 919 patients; in 42% surgery eliminated their strabismus and an additional 16% were cosmetically acceptable. According to Flax & Selenow’s calculations, 18% were worse or no better after exotropia surgery.
One difficulty interpreting this work by Flax and Selenow results from their attempt to compare a variety of surgical result grading systems, and the lack of a specific criteria for cure. For example, a residual postoperative exodeviation of 10 pd might be interpreted as a failure by these authors. Such a result, however, is often a satisfactory goal of surgery since a subsequent cure may occur without further specific therapy.
A second and larger problem occurs when one uses this information to compare surgical and non-surgical results:
Surgery is usually performed on larger exodeviations and especially those that occur at an earlier age. These patients may not be as amenable to intensive orthoptic therapy. Those Xl’s who receive surgery for their XT most likely are a different population from those XTs who receive orthoptic non-surgical therapy.
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Basic
and Divergence Excess
Type
Comparison of treatment effectivity cannot be made if the disease treated , is not the same in two patient groups but is instead yet another independent variable.
• Furthermore, much of the surgery reviewed was carried out between 10 and 40 years ago and techniques, training and knowledge have improved considerably over those years. Nor does the exclusion of cases who received orthoptics at some point help to illuminate an examination of treatment; some of the best results in surgical exotropia treatment may well have occurred in this subgroup excluded by Flax and Selenow. This group needs to be examined if only for purposes of comparison.
Hardesty et al (208) (1978) had the lowest treatment failure rate (14%) of contemporary reports published in a major refereed ophthalmic journal and for this distinction their work warrants further examination.
They performed a retrospective study on 100 consecutive X(Y)s treated with bilateral lateral rectus recessions. The average followup period was 6 years. Overcorrections for more than
two
weeks were handled with miotics and correction of hyperopia when present. If this failed, alternate patching was employed. If patching was ineffective after 3-4 weeks, base out prisms equal to or greater than the angle of deviation were prescribed. The goal was to gradually reduce the prisms until they could be eliminated. Most patients with less than
15 pd
of consecutive El’ were “cured” with prism therapy. Patients not corrected with these procedures had surgery six months or more after the initial procedure.
Patients
initially
undercorrected were given base in prism equal to the deviation to provide constant binocular stimulation. Additionally, orthoptic exercises which improved fusional amplitudes and eliminated suppression were prescribed. Further surgery (bilateral medial rectus resection) was delayed for at least 6 months.
With these aggressive techniques, 78% of their patients achieved a functional cure (which meant no tropia at any distance, no verbal report of strabismus, and stereopsis of at least 400 sec of arc); 91% showed improvement or cure; and
9%
were either not improved or worse.
Approximately one half of their X(T)s were successfully treated with one surgical procedure; the other half had a persistent over- or undercorrection which often required a second procedure.
They believed that their high surgical
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Summer
of
1993
success rate was a result of immediately correcting any over- or undercorrection with prisms in order to maintain constant binocularity. Children old enough to cooperate were given orthoptics. Their therapeutic regimen differed from many other surgical studies in the aggressive use of prisms, orthoptics, and a second corrective surgical procedure as necessary to achieve a cure.
Minis & Wood (215) performed a retrospective study to determine the effective of preoperative alternate day patching on surgical results. Their patients were divided into three groups: 5-12 weeks of alternate all day occlusion, unilateral patching, and no patching.
Postoperative success was greater with both alternate day patching and unilateral patching (87% success) versus no patching (53% success). Their results indicate that alternate day patching significantly improved their surgical results. They point out the need for a controlled prospective study.
Since the publication of the Flax and Selenow review, Zibrandtsen et al (216) in 1986 reported a long term followup retrospective study on 25 X(T)s who had had surgery 10 or more years earlier. Of these patients 13/25 (52%) were phoric with good sensory function; 8,25 (32%) were classified as “fair”; and 4/25 (16%) were classified as “poor”.
Differences between the Hardesty and the Zibrandtsen groups may be accounted for by the use of prisms, patching, supplementary orthoptics, and/or different population characteristics.
Table V and VI
209
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