Imposed positive defocus changes choroidal blood flow in young human subjects

Area of Science:

• Ophthalmology
• Physiology
• Optometry

Background:

• Previous research indicates positive defocus affects axial length and choroidal thickness within 30 minutes.
• The underlying mechanism, particularly the role of choroidal blood flow, remains to be fully elucidated.

Purpose of the Study:

• To investigate if short-term positive defocus alters choroidal blood flow.
• To determine the relationship between changes in choroidal blood flow and axial length.

Main Methods:

• Eighteen young adults were exposed to 30 minutes of monocular positive defocus (+2.5D).
• Axial length and ocular blood flow (choroidal, optic nerve head, retinal vessels) were measured using low-coherent interferometry and laser speckle flowgraphy.
• Measurements were taken before and after the defocus period.

Main Results:

• Positive defocus significantly altered choroidal blood flow, with changes negatively correlated with axial length changes (R = -0.67, p < 0.01).
• Defocused eyes showed significantly greater changes in choroidal blood flow compared to control eyes (p < 0.05).
• No significant association was found between optic nerve head or retinal blood flow and induced axial length changes.

Conclusions:

• Short-term positive defocus selectively impacts choroidal blood flow in young adults.
• The findings suggest that blood flow modulation plays a role in the choroidal response to optical defocus.
• Retinal and optic nerve head blood flow are not significantly affected by short-term positive defocus.