Participants
The participants were 291 persons working in a software company in Bangalore, India. There was no attempt to calculate the sample size when planning the study. However based on the effect size obtained in the present study [0.66 with 0.9 power to detect a significant difference at alpha level 0.05], 50 subjects were required for each group while in fact at baseline there were 146 subjects in the yoga group and 145 in the control group.
All of them used a computer for at least 6 hours each day, for 5 days in a week. Persons of both sexes participated in the trial and their ages ranged between 21 and 49 years. The participants were screened to exclude those who: (i) had consulted a specialist for their visual symptoms, (ii) had uncorrected errors of refraction, (iii) had clinical conditions such as Sjögren's syndrome or kerato-conjunctivitis sicca and (iv) used medication associated with drying of the eyes (e.g., anti-histaminics). None of the participants had to be excluded based on these criteria. The details of the study were described to the participants and their consent to participate was obtained. The project was approved by the ethics committee of the yoga research foundation and had the approval of the human resource department of the software company.
Design of the study
291 participants were randomized prior to assessment as two groups using a standard random number table by the researchers responsible. The two groups were then designated as (i) intervention (i.e., yoga, n = 146) and (ii) wait list control (n = 145) by an office assistant from the software company who had no other role in the study. The yoga (YG) and wait list control (WL) groups were comparable with respect to age (group average (± S.D.) 32.8 (± 8.6) years and 31.9 (± 10.2) years, respectively) and gender-distribution (11 females in YG group and 13 in WL group).
Both groups were assessed at baseline and after 60 days. During the 60 days the YG group practiced yoga for an hour per day, for five days in a week. While the YG group practiced yoga the WL group spent the time in the recreation center of the software company where 60 percent of them talked to their friends, 12 percent spent time playing indoor games, 12 percent worked out in the gym and 16 percent watched television. The WL group had already been spending this time each day doing the same activities and hence during the 60 day period they were following their usual routine. During the 60 days there were 84 drop outs from the trial in the YG group and 90 from the WL group. The large number of drop outs was mainly due to the fact that the participants had demanding work schedules which interfered with their participating in: (i) the intervention (YG group) or recreational activities (WL group) and/or (ii) the assessments (both groups). To be considered as regular in their participation the YG group had to have a minimum of 38 days of attendance during the 60 day period. The trial profile is given in Figure 1.
Assessments
Visual discomfort including dryness, irritation, burning, redness, photo-sensitivity and possible remedial measures (e.g., the use of lubricating eye drops) were determined using a questionnaire [14]. It had 12 items, each of which had 4 possible choices. These were: (i) absent, (ii) rarely present (meaning one or two days per week), (iii) often (meaning more than two days per week) and (iv) continuous. The symptoms were considered during the week before assessment and the four alternatives (i-iv) were graded as '0', '1', '2' and '3', respectively. The person who administered the questionnaire and scored the response sheets was not aware to which group the subjects belonged.
Intervention (yoga)
The 60 minute yoga program included yoga postures (asanas, 15 minutes), regulated breathing (pranayamas, 10 minutes), exercises for the joints (sithilikarana vyayama, 10 minutes), visual cleansing exercises (trataka, 10 minutes), and guided relaxation (15 minutes).
The practice of trataka involves two sets of eye exercises. (i) Shifting the gaze (by moving the eyes alone) in eight directions. During this exercise, practitioners are asked to use their right thumb (and when gazing to the left, their left thumb) as a cue to direct their gaze. The directions are up, down, up to the left, down to the left, up to the right, down to the right and rotation of the eyes clock-wise and anti clock-wise. (ii) During the second exercise, practitioners gaze at a flame placed at eye level without blinking. While gazing at the flame, practitioners are instructed to focus their gaze on the flame and subsequently defocus while keeping their gaze on the flame. Throughout the practice practitioners should sit upright and should avoid moving their head to shift their gaze.
These techniques were selected either because previous research showed that they reduced physiological arousal [15, 16] or based on our unpublished clinical observations.
Data analysis
The data were analyzed using SPSS Version 10.0. Repeated measures analyses of variance (ANOVA) were carried out with one Between-subjects factor, viz., Groups (with two levels, i.e., YG and WL groups) and one Within-subjects factor, viz., Assessments (with two levels, i.e., baseline and day 60). Post-hoc analyses for multiple comparisons between mean values were done with Bonferroni adjustment.