Analysis of the vergence facility test using different prismatic dioptric powers.

ABSTRACT

CLINICAL RELEVANCE The vergence facility (VF) test is important in a complete optometric examination, but there is still controversy over which prismatic power combinations to use according to the patient age, especially in children. BACKGROUND: The aim of this work is to study the VF test using three different prismatic power combinations in four age groups, with a view to determine the best prismatic power for performing the test. METHODS: The VF of 122 healthy subjects was evaluated using three prismatic flippers with different powers 8∆ base-in with 8∆ base-out (8BI/8BO∆), 3BI/12BO∆ and 5BI/15BO∆. The number of cycles per minute (cpm) was counted. RESULTS: The participants were divided into four age groups. The mean age of group 1 was 6.69 ± 0.65 years, that of group 2 was 9.36 ± 0.87 years, that of group 3 was 12.08 ± 0.79 years and that of group 4 was 28.67 ± 8.11 years. The mean cpm value in VF was higher for near vision than in distance vision. The lowest cpm values were observed in the youngest group (group 1) (far vision 8BI/8BO∆ 2.32 cpm, 3BI/12BO∆ 2.68 cpm and 5BI/15BO∆ 1.59 cpm; near vision 8/8∆ 6.59 cpm, 3BI/12BO∆ 7.77 cpm and 5BI/15BO∆ 5.27 cpm). The cpm values increased progressively with age, with group 4 achieving the highest cpm values (far vision 8BI/8BO∆ 3.61 cpm, 3BI/12BO∆ 8.56 cpm and 5BI/15BO∆ 5.28 cpm; near vision 8BI/8BO∆ 10.22 cpm, 3BI/12BO∆ 12.28 cpm and 5BI/15BO∆ 10.89 cpm). CONCLUSIONS: VF increased with age. The youngest children achieved the lowest cpm values, which progressively increased until the highest cpm values were achieved in adults. The best results were found with 3BI/12BO∆ in all groups in near and far vision. Higher cpm values were achieved in near vision than in far vision with all flippers in all groups.