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

6.

Review and Summary of the

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 diag-

nosis 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

J.

Cooper, MS, OD and N. Medow, MD

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 sur-

veyed 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 exer-

cises.

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 insuffi-

ciency type X(l) from 8 studies that

included 615 patients.

He reported that the results of orth-

optics in 62% of these 615 patients were

classified as “good” or “excellent”. If the

studies which included convergence insuf-

ficiency 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 la-

boratory setting).

B.

Surgery

1.

history:

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, de-

pending 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 meas-

ured 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 mus-

cle should be done to prevent the develop-

ment of a consecutive El’. (We believe

these two cases might have been conver-

gence 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

204