Disc-foveal angle and ocular counterrolling as a key in its interpretation

Area of Science:

• Ophthalmology and Optometry
• Neuroscience
• Biomechanics

Background:

• Accurate measurement of the disc-foveal angle (DFA) is crucial for analyzing fundus photographs.
• Existing methods for DFA measurement can be time-consuming.
• Understanding ocular responses to head position is important for interpreting visual field data.

Purpose of the Study:

• To introduce a rapid and reproducible technique for measuring the disc-foveal angle (DFA).
• To establish normative DFA values in a cohort of individuals.
• To investigate the role of DFA measurement in analyzing paired fundus photographs, considering head position.

Main Methods:

• Disc-foveal angle (DFA) was analyzed using Keynote software on 440 fundus photographs from 20 individuals.
• Eleven distinct head positions were assessed using a cervical range of motion device.
• Reproducibility and correlation were evaluated between two fundus camera systems (Topcon OCT 3D-2000 and TRC-50EX).

Main Results:

• A statistically significant difference in mean DFA was observed between the right (5.5±3.4°) and left (8.6±2.9°) eyes (P=0.001).
• The mean absolute difference in DFA between eyes increased with head tilt (P=0.000).
• Ocular counterrolling (OCR) was measured in the roll plane, with values varying based on head tilt direction and degree.

Conclusions:

• The developed DFA measurement technique is both time-efficient and reproducible.
• The left eye consistently exhibits a higher DFA compared to the right eye.
• The findings provide valuable insights for interpreting paired fundus photographs, particularly concerning ocular responses to head movements.