The Effect of Refractive Amblyopia on the Frisby Stereotest.

Purpose: To identify the expected degree of stereoacuity measured by the Frisby Stereotest, in various degrees of unilateral refractive amblyopia.

Methods: A prospective investigation of 22 patients, with a clinical diagnosis of unilateral refractive amblyopia. All patients were aged 4-12 years and seen between February and November 2021.All patients were recruited to the study at their first return visit with new glasses as prescribed by our physicians, following a cycloplegic refraction. All patients had a full orthoptic examination including the near Frisby Stereotest, visual acuity assessment, an induced tropia test (ITT) using a 20 base-in prism. A fixation preference qualified as amblyopia for the purpose of this study. All tests performed are part of our routine examination.

Results: Regression analysis was performed on the data to identify a correlation between variables. We compared the Frisby scores with the maximum visual acuity difference between the eyes, the amblyopic visual acuity, the non-amblyopic visual acuity, and the spherical equivalent of the patients' refractions.Analysis revealed a strong relationship between both the visual acuity difference and the Frisby score (r = 0.64, R² = 0.41), and the amblyopic visual acuity and Frisby score (r = 0.73, R² = 0.53). There was no relationship between the anisometropia based on spherical equivalent refractions (r = 0.03, R² = 0.0007).

Conclusions: Given the moderate-to-strong correlation noted between visual acuity and stereoacuity, we suggest that the Frisby Stereotest can be utilized to imply possible refractive amblyopia and allow earlier intervention which may lead to more successful outcomes.