Vertical Cup-to-Disc Classification Model Predicts Glaucoma 10 Years in Advance

Researchers have proposed a classification model based on a patient’s vertical cup-to-disc ratio (VCDR) that can distinguish eyes likely to develop glaucoma from those that will maintain nonglaucoma status in 10 years, according to a study published in the Journal of Glaucoma.

The researchers aimed to classify normal healthy individuals into distinct classes based on VCDR to subsequently identify normal healthy control volunteers for participation in future genomic studies.

The study was initiated in March 2005. The researchers selected and contacted 842 volunteers older than 40 years who received a first glaucoma examination (fundus photograph, visual field, slit lamp, and intraocular pressure) between March 2005 and March 2010. Those who consented underwent a second examination 10 years after the first examination, between April 2016 and July 2019. 

The team evaluated glaucoma transition rates (GTRs) among the volunteers who returned to participate in the second examination after a 10-year period.

A total of 421 of 842 volunteers participated in the second ophthalmic examination. There were 131 men, with an average age of 69.9±9.9 years and 290 women, with an average age of 68.8±8.2 years. The researchers diagnosed each volunteer as “healthy normal” or “glaucoma suspect” based upon their first glaucoma screening examinations.  

They then further classified healthy normal volunteers into 3 grades of N1 (VCDR <0.3, no notching or nerve fiber layer defect, and no undermining), N2 (0.3 ≤ VCDR <0.6, no notching or nerve fiber layer defect, and no undermining), and N3 (0.3≤VCDR<0.6 with undermining and notching or nerve fiber layer defect, or 0.6≤VCDR<0.7 and notching or nerve fiber layer defect). The average age amongst the groups was approximately 59 years at the first examination.

At the second examination, the average age was 69.9±9.9 among men and 68.8±8.2 among women. Among the groups, the average age was 67.4±8.6 years in the N1 group, 69.1±8.8 years in the N2 group, 69.7±8.9 years in the N3 group, 66.5±8.4 years in the GS group, and 73.0±7.2 years in those who developed glaucoma.

The researchers estimated the GTRs as 1.3% in both the N1 and N2 groups, 3.9% in the N3 group, and 18.2% in the GS group. They found that the GTRs were lower in N1 and N2 than in N3 or GS and that the VCDR of the N1-to-N1 group and N2-to-N2 groups did not increase during the 10-year study period. 

“Considering the continuous progression from healthy normal subjects to GS and further to glaucoma, followed by increases in VCDR from around 0.3 to over 0.7, it may be rational to use VCDR as an index to classify so-called healthy normal [individuals],” according to the researchers.

Disclosure: This research was supported by Santen Pharmaceutical Co., Ltd. Please see the original reference for a full list of disclosures.