Binocular Vision &

Eye Muscle Surgery Qm!y°

Chutter, an orthoptist, (152) (1977) also studied the effect of part-time occlusion on X(T). The dominant eye was initially patched for one week, then alternated. Fifty-one patients were treated: 28 simulated DEX(T), 12 convergence insufficiency type X(T), 4 true DEX(T), and 5 constant XTs. The patients ranged from 4-10 years of age.

Results indicated that patients patched for 3 to 8 hours a day every day did as well, if not better than, patients with full-time patching. Seventy-six percent improved in both groups. The average length of time of treatment was 6 weeks. Patients with deviations greater than 25 pd benefitted from patching but ultimately needed surgery. Improvement consisted of a decrease in the size of deviation and an improvement in fusional ranges and recovery measurements.

lacobucci & Henderson (153) (1965) used constant occlusion for periods up to three months on 17 X(T)s. Fifty-three percent had stronger fusion demonstrated by a change from an intermittent strabismus to a phoria.

Spoor & Hiles (154) (1979) in a prospective study of 38 young children (average age 29 months) with part-time occlusion showed that approximately 50% were changed from an intermittent strabismus to a phoria; approximately 10% became worse. The results were better when the deviation was under 20g.

Spoor & Hiles (155) also subsequently reported their long term results with occlusion by re-evaluating 34 of the original 38 patients who underwent occlusion therapy. The mean age at the beginning of the study was 2 years 5 months, while the mean duration of occlusion was 15 months. The mean age of their patients at the end of the study was 8 years 4 months. Of the initial 22 patients with good results, 18 were able to participate in the study. Fourteen of the 18 (78%) patients maintained a small exophoria after discontinuing occlusion therapy. The remaining four decompensated and underwent surgery.

They also reported the results of 14 patients who failed initial occlusion therapy and underwent surgery. They reported that excellent results were obtained. They felt that occlusion retarded the development of suppression and thus improved the development of fusional amplitudes.

Freeman & Isenberg (156) in 1989 presented a series of 11 early onset X(T)s treated with part-time occlusion for 4-6 hours per day (age 9 months to 5 years 2 months). All patients initially had some

Major Review: Intermittent Evotropia; Basic and Divergence Excess Type

improvement. Three patients (27%) developed a constant XT and required surgery; another three remained phone avoiding the need for surgery; and five continued to require intermittent patching to maintain their improved status. Similar findings were reported in slightly older children (age 17 months to 13 years) in a subsequent study (157).

Minus lenses have been used to stimulate accommodative-convergence in an attempt to reduce exodeviations. Results have been controversial.

Caltrider and Jampolsky (158) (1983) prescribed over correcting minus lenses (-2.00 to 4.00 D) for 35 children with X(T). Of these, 46% showed a change from a poorly controlled X(T) to a well controlled exophoria, 26% decreased their deviation by 15° while their deviation remained latent. Ten of the original 35 were followed for more than a year and 70% of those maintained their improved status of binocularity. The duration of minus lens therapy was from 2-15 months with the median being 18 months. The patients were slowly weaned off the minus lens therapy.

They also reported a decrease in the distance-near AC/A in 38% of the children wearing lenses. The greatest change occurred in those children who had the highest distance-near AC/A ratios. They noted that there was a significant change in the distance deviation while a minimal change occurred in the near deviation.

Though Caltrider & Jampolsky suggest that this represents a change in AC/A ratio, a simpler explanation would invoke the slow vergence system (vergence aftereffects). The esophoria generated at near would be initially eliminated by fusional divergence. However, over time, feedback from fusional divergence at near to the slow vergence system would result in relative orthophorization and reduction of the apparent AC/A ratio.

lacobucci et a! (159) (1986) reported treating with minus lenses 37 patients who were initially undercorrected surgically. Followup time was from 3-9 years. After an average of 24 month.s of followup, they classified 35% as “excellent”, 14% as “satisfactory”, and 46% as “poor”. (Initially, 75% were classified as “poor”.) Interestingly, they did not find any relationship between success with over minus lenses and AC/A ratios.

The reported long term success of (over) minus lens therapy is surprisingly good when one considers that most DE

Summer of 1993 Volume 8 (No.3): 185-216

cases have a normal AU/A

Rutstein et al (160) (1989) evaluated the possibility that the minus lenses might result in an increase in myopia. They reported that there was no “statistically significant” difference in the development of myopia between their patient sample wearing minus lens overcorrection and the reported incidence of naturally occurring myopia.

Veronneau-Troutman et al (161) (1976) performed a retrospective study on 37 X(T)s (average age 8.5 years; range 2-26 years) who were prescribed prisms to correct their exodeviation. Some of the patients wore prisms only, while others had orthoptics and/or surgery.

They reported that some constant XTs became intermittent while others became phone. They also observed convergence amplitudes improved with prismatic correction. They reported that 19% were “cured” with prisms alone. However, three cases increased their angle of exodeviation following the wearing of prisms. [Ed note:

An early prism adaptation test?]

The amount of prism for NRC DEXT was XT + XT/2 while for ARC DEXT they overcorrected the deviation. The mean increase in convergence ranges was 8 pd without orthoptics and 10 pd with orthoptics.

Pratt-Johnson & Tillson (162) (1979) reported that 8 of 12 patients with exodeviations smaller than 20k, who wore prisms which eliminated their deviation, were “cured” after wearing the prisms for 1 to 2.5 years. The patients’ ages were between 2 and 8 years. On the other hand, those children who did not wear the prism glasses failed to show any improvement. The authors stated that it was difficult to get some of the children to wear their prism spectacles.

Auditory biofeedback using an infrared eye movement monitor has been described by Goldrich (163) (1982). Using a variable pitched tone, Goldrich provided auditory biofeedback for the positional sense of the eye. The goal of therapy was to use biofeedback to maintain normal alignment of the eyes in a non-visual environment, i.e., a darkened room, while the patient performed a non-visual task. He treated 12 XTs (7 DEX(T)s, 3 basic X(T)s, and 2 constant XT).

Treatment took 8-18 hours for DEX(T) with 71% achieving “excellent” results. The

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