Buwcular Vision &

Eye Muscle Surgery Qtrly

results were less encouraging with basic X(T)s. Therapy for basic X(T) took approximately 20 hours while only 33% were classified as “fair”. One of the constant XTs achieved a cosmetic success while the other one failed. Afandor (164) reported a similar result using biofeedback

Effectiveness of Orthoptics:

The orthoptic treatment success rates are impressive, especially when one considers that therapy was often carried out by clinic patients who were required to perform home-based therapy. (Our own experience is that home-based therapy is rarely performed, and if performed it is often done incorrectly).

The only study we found which failed to report any improvement with orthoptics was reported by Moore, an orthoptist (165) (1963). She performed diplopia awareness training for one month with concurrent fusional vergence training. Each patient attended only four in-office sessions which stressed antisuppression techniques. (There was no mention of methods to encourage or monitor compliance with techniques outside the office.) The duration of orthoptic therapy used in this study was briefer than any other study described.

According to France, an orthoptist (166) (1992), “orthoptic management is usually unsuccessful if undertaken as a substitute for surgery. However, it (orthoptics) has been shown to enhance surgical success in 60-67% of the cures”. She cites various references (130, 135, 138, 212) to support this contention. However, the authors of only 4 of the 11 references which she cites do not consider orthoptics a primary treatment for X(T).

France also surveyed 150 orthoptists to determine their perceived role in the diagnosis and treatment of Xl’. All stated that they would treat a symptomatic exophoria, 95% would treat X(T)s and 48% said they would treat constant XTs.

Orthoptist orthoptic therapy is primarily given to the patient to do at home while optometric orthoptic therapy utilizes both office and home therapy.

Therapy by orthoptists consists of “push-up” (near point of convergence) techniques with suppression controls, red filter techniques and occlusion for antisuppression, physiological diplopia, fusional vergence amplitude therapy, and passive orthoptics, (i.e., patching, overcorrecting minus lenses, and prisms).

France suggested that X(T) of less than 15 pd may be treated with orthoptics alone

Major Review: Intermittent Exotropia;

Basic and Divergence Excess Type

including occlusion, and in deviations over 25A orthoptics can be used as an adjunct to surgery.

Von Noorden (16) and Parks (35), both surgeons, have reviewed the success rate of orthoptic therapy for X(l’) and have cited Moore’s study (165) as “proof’ that orthoptics is at best an equivocal method of treatment. However, over 20 studies cited above, using a variety of techniques, document the potential effectiveness of orthoptics.

Romano & Wilson (107) recently surveyed 104 selected senior and charter members of the American Association for Pediatric Ophthalmology and Strabismus (AAPOS) of which 65 replied. Half of the respondents queried rarely or never used orthoptics. Of the 52% who routinely used orthoptics, 88% used occlusion, 65% used minus lenses, 53% used prisms, 5% used sunglasses, and 27% used orthoptic exercises.

Duckman, an optometrist, (136),in his 1987 review of the efficacy of vision training for Xl’s, combined orthoptic data for X(l’) including convergence insufficiency type X(l) from 8 studies that included 615 patients.

He reported that the results of orthoptics in 62% of these 615 patients were classified as “good” or “excellent”. If the studies which included convergence insufficiency type X(l’)s were excluded, then 184 of 291 (63%) DEX(T) cases could still be classified as “good” or “excellent”.

Most of these retrospective studies were performed in a clinic environment and as such did not represent optimal conditions (as might be obtained in a scientific laboratory setting).

The first documented surgical treatment for strabismus occurred on October 26, 1839. It was performed by Johann Friederich Dieffenbach, a genera! surgeon, who has become known as the Father of Plastic Surgery (168). Based on the method of performing a tenotomy on the achilles tendon in the club foot, he transected the medial rectus muscle tendon for the correction of “internal squint” (esotropia)(169).

Within a short period of time, he and others performed hundreds of ocular muscle tenotomies on both medial and lateral rectus muscles. Over the next one hundred years, refinements in surgical technique occurred with tenotomy being

Summer of 1993

Volume 8 (No.3): 185-216

abandoned and replaced with more accurate technique.

Any discussion of surgery must properly deal with three questions: 1) who to operate on, i.e., what clinical features of the strabismus does the patient have that requires surgical intervention, 2) what specific surgical procedure should be performed, and 3) what is the criteria for a success or cure?

In general, surgical intervention is considered when non-surgical therapy is failing; there is a deterioration in binocularity manifested by increasing tropia position, squinting, photophobia and asthenopia; and/or there is parental or personal unhappiness when alternative therapies have not met expectations.

Once surgery has been decided upon, the surgeon must decide on the specific procedure. Dunnington (11) (1927) was the first to suggest that surgery should be performed only on the lateral rectus muscle for pure divergence excess XT He recommended that open tenotomy be performed on one or both lateral recti, depending upon the size of the deviation. Dunnington’s ideal postoperative position was an initial overcorrection of 15 “prism degrees”.

However, free tenotomy soon lost favor due to its variable success and imprecise nature. Tenotomy was replaced by measured recession as the most effective method to weaken a muscle as originally described by Prince in 1887 (170), later refined by Jameson (171) (1922), and popularized at midcentury by Costenbader (12,172), then by Jampolsky (173), Knapp (174), Parks (175), Dunlap (64), and others over the next decade.

Costenbader used bilateral lateral rectus muscle recessions. He reported final over- corrections in two cases in 1950. This led Sugar (177) to advocate in 1956 that at least one recession of a medial rectus muscle should be done to prevent the development of a consecutive El’. (We believe these two cases might have been convergence insufficiency type XTs).

Burian (10) in 1966 strongly advocated measured bilateral lateral rectus muscle recessions for true divergence excess.

In a recent survey conducted by Romano & Wilson (167) of charter and senior members of the AAPOS, the vast majority indicated that they performed bilateral lateral rectus muscle recessions for both DEXT and basic X(T). The amount of surgical recession was based primarily upon the distance measurement. The amount of surgery was calculated by

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