Binocular Vision &

Eye Muscle Surgery Qlrly°

Major Review: hztennittent Exorropia;

Basic and Divergence Excess Type

Summer of 1993

Volume 8 (No.3): 185-216

beginning of therapy are those in which the patient can easily attain normal binocular alignment, i.e., large, detailed stereo targets presented at near.

Therapy continues along a spectrum from third degree to first degree targets until normal alignment can be attained even in the absence of disparity cues, i.e., superimposition targets presented at 20 feet or more. The hardest orthoptic task for the X(T) patient to perform is cheiroscopic tracing. For some unexplained reason, X(T)s demonstrate less suppression when tracing in a mirror cheiroscope as compared to a Brewster cheiroscope.

Increasing fusional ranges is of minimal importance according to the Flax/Brock model since there is a minimal deficiency in this area. Flax (69,70) feels the development of diplopia awareness is also unimportant since postural awareness keeps the eyes in proper alignment.

Due to the apparently high AC/A, eso fixation disparity, and accommodative facility deficit, Flax feels that plus lenses should be prescribed for near vision use. However, as previously stated, the apparent high AC/A ratio and eso fixation disparity measured are probably secondary to proximal convergence and/or fusional after effects. Dynamic accommodative studies demonstrate subtle accommodative deficits which are not, however, clinically relevant.

Flax’s model of therapy without the utilization of a near prescription of plus lenses is consistent with the first author’s chameleon model. However, the first author advocates the utilization of red lens diplopia awareness therapy prior to employing the Brock/Flax therapeutic regimen. The purpose of diplopia awareness is to provide the patient with an additional sensory biofeedback mechanism to acknowledge the exodeviation. Once the patient achieves diplopia awareness, therapy consists of conditioning the disparity vergence system to eliminate diplopia via the fusional vergence system. The first author advocates the use of various reinforcement contingencies to assure appropriate binocular responses.

The second phase of the first author’s therapy is identical to the Flax/Brock model in which fading procedures are used to slowly eliminate retinal and contour cues. The patient at the end of therapy demonstrates NRC, elimination of suppression, and normal binocular alignment in the absence of disparity or fusion cues.

Constant normal binocular alignment is then maintained by disparity vergence and “postural awareness”. Disparity vergence, through a feedback signal to the slow

vergence system reduces the phoria, thw eliminating the exodeviation. Although thc basic exodeviation is still present and car be elicited through prolonged occlusion the binocular system has functionally decreased the fusional demand by using slow vergence or fusional aftereffects.

Goldrich (141) reported in 1981 a ret rospective study of 28 DEXT cases (ag 5-35 years) treated with the Brock/Flax techniques. All patients had deviations less than 35& Weekly in-office training was supplemented with home therapy. Therap) consisted of motility, accommodative facil ity, near and distance vergence, anti suppression and jump duction techniques Therapy consisted of 45 minute in-office therapy with supplemental home therapy Success criteria were very rigid, lie repor ted 72% classified as “excellent” (averag number sessions = 29), 10% were “good” 14% were “fair”, and only 3% remainec “poor”. In other words, 96% improvec while 82% were transformed from “strabis mus” to “no strabismus with comfort” ir approximately 7 months.

Ludlum (142) in reported in 1961 a ret rospective study of vision training in 58 X(T)s who had at least 8 sessions of ther apy. Therapy was mostly in-office 45 minute sessions 2-3 times a week (mean 23 sessions, range 10-76). Therapy was well detailed and included motility, accommodation, fu.sion amplitude, anti- suppression, and accommodation-convergence training. Ludlum also included occlusion techniques. Criteria for complete success was allowing the deviation to occur less than 1% of the time with immediate recovery of fusion based upon diplopia. Partial success was defined as a deviation occurring between 1-5% of the time with recovery of fusion occurring immediately upon deviation. Complete success occurred in 52%; partial success (strabismu.s up to 5%, a need for prisms, and/or a lack of stereopsis) in 40%. Long term results (143) of at least 3 years demonstrated that 63% remained cured.

Etting (144,145) (1978,1973) presented two retrospective studies for a combined total of 23 patients with DEXT. They had at least 24 in-office therapy sessions. According to Etting, 91% of the patients with Xl’ were “cured”.

I-Ioffman et al (146) also reported in 1970 a high success rate (95%). All their patients except one had a deviation less than 30A. The criteria of success and the accurate classification of patients provided by Etting was not provided by I-Ioffman et

a!.

Daum (147) reported in 1986 another

retrospective study on the effects of orthoptics in DEXT. He reported that the angle of deviation decreased at distance more than at near resulting in a decrease in the AC/A ratio.

Heath & Hofstetter (148) had also reported in 1952 that the stimulus AC/A decreased from 10/1 to 6/1 after training. Vaegan (149) in 1979 demonstrated that 30% of his patients who had significant exodeviations before therapy showed eso fixation disparity after therapy. Daum (147) in 1986 reported that both positive and negative fusional vergences and their respective recoveries increased after therapy.

Goldrich (141) reported (1980) improvement in ocular motility, accommodative facility, vergence ranges! flexibility and a decrease in suppression after therapy.

Flynn et al reported in 1976 (150), that while treating amblyopic X(T)s with patching, they noted an improvement in sensory and motor fusion as determined by an elimination of the suppression scotoma; a reduction of the angle of deviation; and! or improvement in fusional ranges. They studied 31 X(l’)s who were alternately oceluded full time for 6-12 weeks (average age 7.6 years, SD 3.3). The mean pretherapy distance deviation was 20 pd (±7.2k) and 15.4 diopters (±11.8k) at near.

Sixty-seven percent of the patients had an improvement in their sensory motor performance. In 22%, the deviation became almost phone; fusion improved and all evidence of suppression on a synoptophore or in free space disappeared. The motor effect consisted of a reduction in the angle and/or a change from a tropia to a phoria. The most common sensory change was elimination of the suppression scotoma with a report of spontaneous diplopia.

Twelve patients, almost 33% of his sample, had a negative effect from patching, i.e., an increase in the size and character of the deviation. Flynn et al stated that it was impossible in retrospect to predict which children would respond negatively or positively to occlusion.

Velez (151) reported (in the same book) that he had evaluated 221 Xl’ patients with deviations greater than 20a who had surgery and/or antisuppression techniques. He reported that antisuppression techniques did not affect his post-surgical results. Velez did not describe which antisuppression techniques were used, or how long or well they were u.sed.

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