Optic Nerve Tortuosity on Earth and in Space

Area of Science:

• Ophthalmology
• Neurology
• Aerospace Medicine

Background:

• Spaceflight Associated Neuro-ocular Syndrome (SANS) is a condition affecting astronauts on long-duration missions.
• Optic nerve tortuosity (ONT) is a detected sign in SANS but requires further analysis.
• Understanding terrestrial ONT can provide insights into SANS.

Purpose of the Study:

• To review terrestrial causes and measurement methods for optic nerve tortuosity (ONT).
• To establish objective and standardized techniques for ONT assessment.
• To explore the relationship between ONT and intracranial pressure.

Main Methods:

• Conducted literature searches on PubMed and ScienceDirect using terms related to optic nerve tortuosity.
• Reviewed studies published from 1955 to October 2018.
• Identified and analyzed various terrestrial causes and measurement techniques for ONT.

Main Results:

• Objective measurement criteria for ONT include lack of optic nerve congruity and subarachnoid space dilation.
• The tortuosity index provides a quantitative measure of ONT and allows tracking of changes.
• Numerous terrestrial conditions, often involving pressure changes, are associated with ONT.

Conclusions:

• Standardized, objective measurement techniques are essential for accurate ONT assessment.
• The tortuosity index shows potential for monitoring intraindividual changes in ONT.
• Investigating the link between intracranial pressure and ONT may illuminate SANS mechanisms.