Compression of the Choroid by Horizontal Duction

Area of Science:

• Ophthalmology
• Optics
• Human Anatomy

Background:

• The optic nerve's position can be altered by eye movements, potentially deforming the optic disc.
• Understanding changes in choroidal volume is crucial for assessing optic nerve health.

Purpose of the Study:

• To investigate how horizontal eye movements (duction) and age affect choroidal volume temporal to the optic disc.
• To quantify the impact of adduction and abduction on peripapillary choroidal volume in different age groups.

Main Methods:

• Optical coherence tomography (OCT) was used to image the optic disc and peripapillary choroid in 25 younger and 15 older adults.
• Subjects underwent imaging in central gaze, 35° adduction, and 35° abduction.
• Choroidal thickness was measured in specific regions temporal to the optic disc, and regional volume changes were calculated.

Main Results:

• In adduction, younger subjects showed a 42.4 nL (7.5%) reduction in choroidal volume, while older subjects had a 6.2 nL (1.3%) reduction.
• Volume reduction was most significant near the optic disc and extended further in younger individuals.
• No significant volume changes were observed during abduction.

Conclusions:

• Horizontal eye movements, particularly adduction, compress the temporal peripapillary choroid.
• This compression effect is more pronounced in younger individuals compared to older ones.
• The findings suggest that optic nerve tethering in adduction contributes to peripapillary tissue deformation.