Development and Preliminary Evaluation of a Smartphone App for Measuring Eye Alignment

Area of Science:

• Ophthalmology
• Medical Technology
• Biomedical Engineering

Background:

• Accurate measurement of eye deviations is crucial for diagnosing and managing various ocular conditions.
• Traditional methods for assessing eye alignment can be time-consuming and require specialized equipment.
• The integration of mobile technology offers potential for more accessible and efficient diagnostic tools.

Purpose of the Study:

• To evaluate the accuracy and consistency of a smartphone application designed for automated photographic Hirschberg testing.
• To assess the app's performance in measuring horizontal eye deviations in both nonstrabismic and strabismic individuals.

Main Methods:

• Three studies were conducted: gaze angle measurement against ground truth in nonstrabismic subjects (n=25), comparison of app-based phoria measurements with the modified Thorington (MT) test (n=14), and comparison of app-based strabismus measurements with cover test with prism neutralization (CTPN; n=66) and Synoptophore (n=34).
• Regression analyses were employed to compare app measurements with established clinical methods, quantifying magnitude and direction of eye deviations in prism diopters (Δ).

Main Results:

• The app demonstrated high accuracy in measuring gaze angles, closely matching ground truth (R² = 0.97, RMSE = 2.4Δ).
• Phoria measurements using the app were consistent with the MT test (R² = 0.97, RMSE = 1.7Δ).
• Strabismus measurements showed good consistency with CTPN (R² = 0.95), with improved agreement after near fixation correction (slope = 1.01), and were comparable to Synoptophore measurements (R² = 0.91).

Conclusions:

• Smartphone app measurements of manifest and latent eye deviations are consistent with established clinical assessment methods.
• The developed application serves as a convenient clinical tool for eye alignment measurement and holds promise for telemedicine applications.