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AM J OPTOM & PHYSIOL OPTICS

Vol. 64, No. 6

in alternate ocular occlusion. The viewing tar-

gets presented during the on cycle were 6/7.5

(20/25) visual stimuli. Both the control and the

experimen.tal patients received experience in

identical telebinoculars, with identical viewing

stimuli, during the same session time and day.

The experimental group had a plus lens placed

in front of the right eye and a minus lens in

front of the left eye during alternating monoc-

ular accommodative training. During the on cy-

cle the patient was required to clear the lens

interposed between the eye and the 6/7.5 (20/

25) visual stimuli. After 5 min, the plus and

minus lenses were switched. If the patient was

able to maintain clarity for 5 min with plus and

minus lenses, without any signs of ocular fa-

tigue, the power of the next pair of lenses was

increased. In addition, the patient had to dem-

onstrate instantaneous accommodative changes.

However, if the patient could clear one lens but

not the other, only the lens cleared was in-

creased according to the following sequence:

+0.50/—0.50; +0.75/—1.00; +1.00/—2.00; +1.25/

—3.00; +1.50/—4.00; +1.75/—4.50; +2.00/—5.00;

+2.25/—5.50; +2.50/—6.00 D. By the end of

twelve 30-mm sessions, all patients were ex-

pected to clear a +2.50/—6.00 D within 2 s

without any signs of fatigue. The final value

represented 8.50 D accommodative change.

The matched control subjects underwent the

same training as the experimental subjects with

one exception. During each of the twelve 30-mm

training sessions (2 times per week for 6 weeks),

the accommodative lenses marked with plus and

minus values (e.g., +0.50/-0.50) were actually

piano lenses. Neither the patient nor the thera-

pist was made aware of this fact. Thus, during

training, control patients experienced no altered

accommodative demand. At the end of 12 ses-

sions, both the experimental and control groups

once again underwent accommodative testing,

vergence testing, and the asthenopia rating

questionnaire.

After this testing, the experimental patients

received an additional 6 weeks of training iden-

tical to that of the control group, i.e., all training

was now with plano lenses. The control group

patients also received another 12 weeks of train-

ing. The conditions were identical to those of

the original experimental group so that training

was performed with lenses having different val-

ues of accommodative demand (e.g., +0.5/—0.5).

This matched-subjects crossover design was

used to control primarily for “order of treatment

effects” and to demonstrate that patients

switched from piano to accommodative demand

lenses would show corresponding changes in

accommodative amplitude and in asthenopia.

After this second 12-week period, both groups

again received a third clinical testing and as-

thenopia questionnaire. Once again, all evalua-

tions were done by clinicians having no know!-

edge of the patient’s ocular status or group,

experimental or control.

RESULTS

Fig. 2 depicts the mean absolute values of

accommodative amplitude during baseline, ex-

perimental, and control conditions as a function

of the order of treatments. The abscissa depicts

the three phases of testing, i.e., baseline, phase

1, and phase 2. Mean accommodative amplitude

for all patients in each phase (determined by

minus lens to blur) is plotted on the ordinate.

The experimental and control groups performed

similarly at the initial baseline, 5.25 and 5.08 D,

respectively. However, patients who received ex-

perimental training during phase 1 showed a

marked increase in accommodative amplitude

compared to the control group. Amplitudes after

phase 1 were 8.00 and 5.16 D, respectively. The

latter value did not differ from its initial baseline

measure. After phase 2, a substantial change in

performance could be seen for the control group.

Accommodative amplitude increased to 7.5 D

for these patients, whereas it remained virtually

unchanged for the original experimental group.

When the data from all patients were combined

so as to compare the change in accommodative

amplitude after either experimental or control

conditions, a statistically significant difference

was observed (t = 7.36, dF = 4, p <0.01).

Table 1 presents changes in accommodative

amplitude for each patient after exposure to

plano lenses or accommodative demand lenses.

The order of assignment to groups is also indi-

cated. As is apparent, all but one patient showed

an increase in accommodative amplitude after

exposure to the experimental condition that was

greater than that to the control condition. Table

1 also shows that the mean change of accom-

modative amplitude was significantly larger

after experimental than control conditions.

Fig. 3 presents the mean absolute asthenopia

scores for experimental and control groups dur-

ing baseline, phase 1, and phase 2 conditions.

Asthenopia scores are presented on the ordinate,

whereas phases of testing are presented on the

abscissa. The scores during initial baseline test-

ing were somewhat lower for the experimental

than for the control group patients, 6.0 and 8.67,

respectively (the higher the score, the fewer the

symptoms). After phase 1, patients who received

experimental training showed a marked reduc-

tion in symptoms compared to the control group,

13.0 and 9.33, respectively. The control group

showed only a small change from baseline find-

ings. After phase 2, when the original experi-

mental and control groups received the cross-