Normative values for clinical measures used to classify accommodative and vergence anomalies in a sample of high school children in South Africa.

AIM: To determine normative values for stereoacuity, accommodative and vergence measures for high school populations.

METHODS

Using a multi-stage random cluster sampling, 1211 children (481 males and 730 females) between 13 and 18 years of age, with a median age of 16 years, were selected. Visual acuity, stereoacuity and suppression, refractive errors, near point of convergence, heterophoria and fusional vergences, as well as, amplitude of accommodation, accommodative response, facility and relative accommodation were evaluated.

RESULTS

Most data did not have a normal distribution. The range of normality for the vergence measures were: near point of convergence break, 5-10cm, recovery, 6-13cm, near lateral phoria, 2.5-6 prism dioptre (pd) (nasal), near vertical, orthophoria to 0.50pd, negative fusional vergence break, 12-23pd, recovery, 8-17pd, positive fusional vergence break, 16-35 and recovery 11-24pd. For accommodative measures, the range of normality for accommodative measures was: amplitude of accommodation, 12-18pd, accommodative response, plano to +0.75D, binocular accommodative facility, 5-12 cycles per minute (cpm), negative relative accommodation, 1.75-2.50DS, positive relative accommodation, -2.0 to -3.0DS and 17-69s arc for stereoacuity.

CONCLUSION

This study provides norms for clinical measures which could be used to classify accommodative and vergence parameters for children aged 13-18 years in this population or beyond. Findings should be applied in the context of the measurement techniques and the associated limitations outlined in this report.