A Novel Device for Vergence Exercises: Testing Automatic Dual Rotational Risley Prisms on Asymptomatic Adults and Patients with Convergence Insufficiency

Introduction: This study investigated the effects of automatic dual rotational Risley prisms (ADRRPs), a mobile phone application-operated device, on vergence abilities in young adults.

Methods: Fifty-six participants aged 20-24 performed vergence exercises. The test group used prisms with power changes from 30Δ base-out to 10Δ base-in, while the control group used plano lenses for 10 min. Ophthalmic examinations included lateral heterophoria, near point of convergence (NPC), vergence facility (VF), negative fusional vergence (NFV), and positive fusional vergence (PFV), all measured before and after the vergence exercises. Pre- and post-test results were analyzed using a paired sample t test. Additionally, three cases with convergence insufficiency (CI) performed similar exercises for 12 weeks.

Results: Participants were divided into the test group (n = 39; age 21.82 ± 1.10 years) and control group (n = 17; age 20.53 ± 0.51 years). In the test group, NPC improved from 6.11 ± 2.52 cm to 5.77 ± 2.30 cm (p = 0.023). VF increased from 13.75 ± 4.10 cpm to 16.50 ± 4.42 cpm (p = 0.007). PFV at 6 m and 0.4 m increased from 19.49 ± 6.77∆ to 22.19 ± 6.64∆ (p < 0.001) and 20.51 ± 7.05∆ to 22.69 ± 6.44∆ (p = 0.012), respectively. After 12 weeks, convergence insufficiency symptom survey scores for cases with CI decreased significantly, with NPC improving from 7.0 to 0 cm, 6.0 to 5.8 cm, and 6.0 to 4.7 cm. PFV increased from 10 to 25∆, 20 to 30∆, and 25 to 50∆.

Conclusion: This preliminary study showed the effect of ADRRPs on improving vergence abilities. Further studies are needed to investigate the long-term sustainability and effects in a larger population of individuals with CI of this approach.