Intra-observer reliability of the Harms tangent screen test

Area of Science:

• Ophthalmology
• Clinical Measurement Science

Background:

• Diplopia, often caused by strabismus, significantly impacts patient quality of life.
• Accurate ocular motility analysis is crucial for diagnosing and managing strabismus.

Purpose of the Study:

• To evaluate the intra-observer reliability of the Harms Tangent Screen Test (HTS).
• To assess the consistency of HTS measurements for ocular motility in patients with diplopia due to strabismus.

Main Methods:

• Prospective clinical case study involving 58 patients with diplopia.
• Subjective assessment of squint angles using HTS across nine diagnostic gaze positions.
• Repeatability assessed via consecutive measurements by the same examiner, analyzed with intraclass correlation coefficients (ICCs) and 95% limits of agreement (LOA).

Main Results:

• High ICCs for horizontal (≥0.99), vertical (0.96-0.99), and torsional (0.93-0.98) squint angles.
• Mean differences between measurements were ≤0.5° for primary gaze.
• LOA ranged from -3.1° to 3.1° across different angle types.

Conclusions:

• The Harms Tangent Screen Test (HTS) demonstrates good repeatability and consistent measurement reliability.
• HTS is a reliable tool for ocular motility analysis in patients with strabismus-induced diplopia across all gaze positions.