The Advanced Glaucoma Intervention Study (AGIS): 10. Variability among academic glaucoma subspecialists in assessing...

Area of Science:

• Ophthalmology
• Optic Nerve Imaging
• Glaucoma Diagnosis

Background:

• The Advanced Glaucoma Intervention Study (AGIS) suggested a link between partial optic disc rim notching and reduced risk of visual field loss.
• This finding is counterintuitive, as optic disc rim notching is typically associated with increased glaucoma progression.
• The AGIS protocol lacked defined criteria for classifying optic disc rim notching.

Purpose of the Study:

• To assess the interobserver and intraobserver agreement among glaucoma specialists in classifying optic disc rim notching.
• To evaluate the reliability of optic disc rim notching classification in the absence of standardized definitions.

Main Methods:

• Fourteen glaucoma subspecialists reviewed 26 stereoscopic disc photographs of eyes with varying degrees of glaucomatous optic neuropathy.
• Ophthalmologists classified images into three categories: no notching, notching not to the edge, or notching to the edge.
• Ten specialists reclassified the same images after several hours to assess intraobserver agreement.

Main Results:

• Interobserver agreement was substantial on only 11 of 26 images (42%), with significant disagreement on the remaining 15.
• Intraobserver agreement showed that none of the 10 specialists reclassified all images identically, with 80% overall reproducibility.
• Disagreements were frequent, particularly in distinguishing between notching present but not to the edge versus notching to the edge.

Conclusions:

• Without standardized definitions and examples, glaucoma specialists exhibit considerable disagreement in characterizing optic disc rim notching.
• While intraobserver agreement was relatively high, interobserver variability suggests a need for clearer classification criteria.
• Development and validation of a standard photographic classification system for optic disc rim notching are recommended.