Belin ABCD staging system may aid in monitoring keratoconus progression
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PHILADELPHIA — The Belin ABCD staging classification may be useful for monitoring keratoconus progression after corneal cross-linking, according to a speaker at the Wills Eye Conference.
Neil Vadhar, MD, and colleagues performed a retrospective review of 104 keratoconus patients who underwent cross-linking from January 2016 to June 2019. Patients were evaluated preoperatively and at months 3 and 6 postoperatively using the ABCD staging system on the Oculus Pentacam.
The Belin ABCD system grades the anterior corneal surface, posterior corneal surface and corneal thickness. The A value is derived from the anterior radius of the curvature, and the B value is the back radius of the curvature, both obtained at a 3-mm optical zone centered on the thinnest point. The C value is corneal thickness, and the D value, which was not a factor used in the study, is the distance corrected visual acuity.
“The advantage of the Belin ABCD staging is that, one, it’s centered on the thinnest point rather than the apex of the cornea, and it looks at both the anterior and posterior surfaces of the cornea,” Vadhar said, adding that the posterior surface is where initial changes in keratoconus are sometimes seen.
The only statistically significant change in the staging value after corneal cross-linking was a worsening in corneal thickness at postoperative month 3 (P = .00016). There was a trend toward worsening of the A and B values at month 3 as well. However, at month 6, the A value, which was least affected, improved compared with baseline, and the B and C values trended back toward baseline.
This result may be expected because cross-linking occurs in the anterior cornea, Vadhar said.
“The posterior surface may not necessarily be affected by cross-linking. Progression of the posterior curvature may be normal after cross-linking and may actually lead to stabilization of the cornea as the stroma compacts,” he said. – by Erin T. Welsh
Reference:
Vadhar N. Assessing progression of keratoconus using the ABCD classification following collagen crosslinking. Presented at: Wills Eye Conference; March 5-7, 2020; Philadelphia.
Disclosure: Vadhar reports no relevant financial disclosures.
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