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AM J OPTOM & PHYSIOL OPTICS

Vol. 60, No. 12

member of a pair was then randomly assigned

to either an experimental or control group. Pa-

tients in the experimental group initially re-

ceived a vergence training procedure identical

to that experienced during RDS baseline testing.

Training consisted of 100 trials per weekly ses-

sion. At the end of each session, maximum con-

vergence attained before the onset of diplopia

was recorded. The vectograms were then sepa-

rated in a base-out direction until diplopia oc-

curred, and the value was recorded. Patients in

the control condition received the same number

of RDS stimulus presentations as their matched

partners. The convergence demand, however, in

the control group remained constant (i.e., the

right and left views were superimposed at 40

cm). When a patient in the experimental con-

dition attained either a minimum of 25 of

positive relative convergence during three suc-

cessive sessions or completed 15 sessions, that

patient and his matched control partner re-

versed conditions. The new experimental group

received vergence training until the previously

stated criteria were met, whereas the new con-

trol group received an identical number of trials

and sessions without programmed changes in

vergence demand.

After this second phase, RDS baseline testing

was again performed, and traditional orthoptic

therapy was initiated. This included various ac-

commodative.’6”7 vergence, and stereoscopic

training procedures.4’8 After a minimum of eight

sessions, one per week of orthoptics, a final RDS

baseline evaluation was conducted along with

measurements of asthenopia and fixation dis-

parity curves.

Different experimenters performed various

clinical and experimental procedures through-

out this study without having access to patient

performance during other segments, so as to

minimize experimenter bias. All findings were

kept confidential until termination of the exper-

iment and all testing was standardized.

RESULTS

Vergence performance and asthenopia scores

for each patient during baseline, control, exper-

imental, and orthoptic therapy phases are pre-

sented in Fig. 1. Performance during RDS test-

ing and training represents maximum vergence

achieved in prism diopters, while vectographic

scores represent the break point in prism diop-

ters using base-out fusional stimuli. Asthenopia

scores represents the total of the patient’s score

on a questionnaire, with higher scores repre-

senting fewer and/or less severe symptoms.

It is evident that after the experimental phase

(automated vergence training) all patients ex-

hibited significant increases in maximum ver-

gence as compared to that recorded in the pre-

ceding baseline or control phase. Mean increase

in vergence for all seven patients was 17.7

(SD = 6.9). In contrast, a much smaller vergence

increase was noted after the control phase; mean

increase in convergence was only 2.4 (SD =

4.1) (Table 1). Statistical analysis revealed that

maximum vergence scores in baseline, control,

and experimental phases were significantly dif-

ferent (F = 7.75; DF = 2,12; p > 0.01). Increases

in vergence ranges for vectographic testing fol-

lowed a similar pattern, with larger increases

following the experimental phase (mean in-

crease = 5.57 pd SD = 6.68) than the control

phase (mean increase = 2.14 pd, SD 3.48).

These differences approached, but failed to

reach, statistical significance (F = 3.35; dF =

2,12; p < 0.10). After orthroptic therapy admin-

istered to five of these patients, retesting of

vergence ranges using vectographic stimuli was

completed. Findings indicated a moderate, but

variable, improvement in base-out break point

in comparison to that found at the end of the

experimental phase (mean improvement = 7.30

pd, SD = 13.39).

Fig. 1 also shows each patient’s asthenopia

score after baseline control and experimental

phases. A Friedman two-way analysis of

variance’8 revealed a statistically significant dif-

ference in reported symptoms between these

conditions (X2 = 8; dF = 2; P = 0.016). As

expected, larger changes occurred after the ex-

perimental phase (mean decrease in symptoms

= 6.42; SD = 3.46) than the control phase (mean

decrease in symptoms = 0.43; SD = 4.76). Fur-

ther decreases in symptoms occurred after or-

thoptic therapy in the four patients for whom

data were available (mean decrease in symptoms

from a mean baseline finding of 20 to the end of

orthoptics was 10.5 in these four patients (a

classification shift from “moderately uncomfort-

able” to “very comfortable”). The final asthen-

opic score (mean = 30.5; SD = 3.30) was close

to the upper limit of 35 which represents a

totally asymptomatic patient, thus indicating in

our small sample that orthoptic therapy signifi-

cantly reduced asthenopia.

Forced vergence fixation disparity curves for

six of the seven patients are presented in Fig. 2.

Each graph contains baseline and postexperi-

mental test curves, with five also showing post-

control test curves. Our forced-vergence fixation

disparity data for six patients were analyzed

with respect to curve type, curve range, curve

slope, magnitude of fixation disparity, and mag-

nitude of associated phoria. There was no