Central retinal vessel trunk exit location: An important factor while evaluating the neuroretinal rim

Area of Science:

• Ophthalmology
• Optic Nerve Head Imaging
• Glaucoma Diagnosis

Background:

• Optic nerve head (ONH) evaluation is crucial for distinguishing normal from glaucomatous disks.
• Inferior neuroretinal rim (NRR) thinning is an early indicator of glaucoma.
• NRR thickness can be influenced by factors like central retinal vessel trunk (CRVT) exit position.

Purpose of the Study:

• To investigate ocular parameters determining NRR thickness in different quadrants of normal eyes.
• To understand the relationship between CRVT position and NRR thickness variations.
• To assess factors influencing adherence to the ISNT rule in healthy optic nerves.

Main Methods:

• Retrospective analysis of demographic and ocular data from 773 eyes of 388 healthy subjects.
• Evaluation of CRVT exit location (central vs. noncentral).
• Assessment of neuroretinal rim thickness and adherence to the ISNT rule.

Main Results:

• Central CRVT exit occurred in 50% of eyes; superotemporal and inferotemporal were common noncentral sites.
• Noncentral CRVT increased the likelihood of not following the ISNT rule (odds ratio 1.42).
• The thinnest rim quadrant was typically superotemporal, but inferotemporal with inferotemporal CRVT exit. Larger disks, longer axial length, and inferonasal CRVT were associated with ISNT rule noncompliance.

Conclusions:

• Inferotemporal CRVT exit correlates with the thinnest inferotemporal rim, and the ISNT rule is often violated in normal eyes with specific characteristics.
• Noncompliance with the ISNT rule in normal eyes can be linked to disk size, axial length, and CRVT location.
• These findings suggest that ISNT rule violations in normal eyes do not necessarily indicate pathology, potentially avoiding unnecessary diagnostic procedures.