METHODS

Subjects

In the first part of the study, we selected twenty eight children (aged between 11 and 17 years, group average age ± SD, 14.2 ± 1.9 years) at random from a special school for the visually impaired (Raman Maharshi Academy for the Blind, Bangalore, India). All of them had congenital visual impairment with an uncorrectable visual acuity of 6/60 or less in the better eye from birth, which is the conventional description of blindness (Sheridan, 1969). Blindness was due to peripheral causes, e.g., microphthalmos, congenital cataract or optic atrophy. We selected twenty eight children with normal vision (6/6 without correction) so as to exactly match those with impaired vision with respect to age and sex. We abtained the informed consent of the subjects and their guardians in accordance with the ethical guidelines of the Indian Council of Medical Research, New Delhi, India.

The second part of the study involved twenty four children of the twenty eight assessed in the first part of the study. These twenty four children were selected as they could be matched to form pairs, on the basis of age, sex and degree of visual impairment. The method for grading has been described below, under 'Measurements'. We then randomly assigned subjects of a pair to either of two groups, viz., yoga or physical activity. The group average age ± SD was 14.1 ± 1.9 years (yoga group) and 14.1 ± 2.2 years (physical activity group).

Design of the study

In the first part of the study forty children with ages between 11 and 17 years were selected at random from among a total of three hundred and forty children attending a special school for the blind. Out of the forty, twenty eight children with congenital visual impairment were selected for the first part of the study (VI group), as these could be exactly matched with twenty eight children with normal sight (NS group). Matching was based on age and sex. Both groups (visually impaired and normal sighted) were assessed under similar conditions, described in detail below.

The second part of the study was conducted on twenty-four children with impaired vision, out of the twenty eight assessed in the first part of the study. The baseline assessment was carried out in the same way as the first part of the study, one month later. After this the yoga group received training in yoga, while the physical activity group spent time in an outdoor activity (i.e., gardening) for the allotted hour, for five days a week. The yoga instructor spent an equal amount of time with children of both groups. After three weeks both groups were assessed once more. The final assessments were performed by the same persons, under similar conditions as the baseline assessments.

Measurements

Recordings for the first part of the study (VI group versus NS group), as well as for the second part (yoga versus physical activity group of visually impaired children), were made in a moderately lit, sound attenuated room. After an initial 15 minute period of supine rest, assessments were made for 10 minutes, also in the supine position and with eyes closed. The blood pressure was recorded from the right arm using a standard sphygmomanometer while the subject was seated. It was not possible to obtain blood pressure records for the second part of the study.

A 10 channel polygraph (Polyrite, Recorders and Medicare, Chandigarh, India) was used to record the electrocardiogram (EKG), respiration and skin resistance level (SRL). EKG was recorded using standard limb lead 1 configuration. Skin resistance was recorded using Ag/AgC1 disc electrodes with electrode gel (Medicon, Madras, India), placed in contact with the volar surfaces of the distal phalanges of the index and middle fingers of the left hand. A low level DC preamplifier was used and a constant current of 10 microamperes was passed between the electrodes. Respiration was recorded using a volumetric pressure transducer. Subjects were asked to stand erect and the transducer was fixed around the trunk, approximately 5 cm below the lower costal margin. The blood pressure was recorded with a sphygrnomanometer.

The degree of visual impairment was graded for all the children with impaired vision as follows: grade 0, the inability to differentiate between light and dark; grade 1, the ability to differentiate between light and dark; grade 2, the ability to perceive gross movements; and grade 3, ability to count fingers held at a distance of 30 em.

Data extraction and analysis

 Data extraction was carried out similarly for both parts of the study. The heart rate (in beats per minute) was obtained by counting the QRS complexes in successive 60 sec epochs, continuously. The breath rate (in cycles per minute) was similarly calculated by counting the breath cycles in 60 sec epochs, continuously. The SRL was sampled at 20 sec intervals. For each subject the average of the values obtained during the 10 minute session was used for analysis.

The data of the V1 group and the NS group were compared using the Mann- Whitney U test. The data of the yoga and physical activity groups obtained at the end of three weeks were compared to the respective baseline data using the Wilcoxon paired signed ranks test.

Yoga training

Yoga was taught by a trained instructor. Individuals with normal vision learn yoga by observing a demonstration while listening to instructions. In the visually impaired detailed verbal instructions were given to compensate. In addition, the instructor spent time with each subject correcting their practice (e.g. repositioning their limbs) with verbal instructions. Special emphasis was given to relaxing between practices and being aware of body sensations. Practices included simple yoga postures and yoga breathing exercises (50 minutes), followed by guided relaxation (10 minutes). Throughout the practices the emphasis was on awareness (of physical and other sensations) and relaxation.

Physical activity

The physical activity group did not learn yoga. During the allotted hour they spent time in the garden, doing a comparable amount of physical activity as the yoga group, such as bending forwards and stretching upwards. The yoga instructor spent time with these children every day and was equally familiar with them as with the yoga group.