Table 1.

Optical coherence tomography classification of keratoconus.

Stage	Characteristics
1	Thinning of epithelial and stromal layers at the conus. Corneal layers have a normal aspect.
2	Hyperreflective anomalies occurring at Bowman's layer level and epithelial thickening at the conus:
	2a: Clear stroma.
	2b: Stromal opacities.
3	Posterior displacement of the hyperreflective structures occurring at Bowman's layer level with increased epithelial thickening and stromal thinning:
	3a: Clear stroma.
	3b: Stromal opacities.
4	Pan-stromal scar.
5	Hydrops stage:
	5a: Acute onset, characterized by the rupture of Descemet's membrane with delamination of collagen lamellae, large fluid-filled intrastromal cysts, and the formation of epithelial edema.
	5b: Healing stage, pan-stromal scarring with a remaining aspect of Descemet's membrane rupture.