Keratoconus patients who previously didn’t require surgical treatment had the greatest progression levels after six years if they were myopes with central-localizing steepening but normal mid-periphery flattening, a new study reports.

Spanish researchers sought to evaluate and characterize long-term clinical changes in keratoconus cases that didn’t require surgical treatment in this retrospective longitudinal study. This study was novel, since previous investigations analyzing keratoconus progression to date have evaluated advanced cases in which surgical intervention was needed or recommended, researchers noted. 

Investigators enrolled 68 non-surgically treated keratoconic eyes of 46 patients with a follow-up period of approximately six years. The patients had no significant visual problems (visual loss of less than two lines in six years). Researchers evaluated visual, refractive, topographic and aberrometric changes and divided the patients into two groups: those with progression and those without. The study defined a progression index and modeled its relationship with baseline data using multiple linear regression analysis.

The study found significant differences in a quantity of baseline parameters between progression and non-progression groups for changes in sphere, spherical-like and coma-like root mean square, central mean keratometry (mean keratometry in the 3mm central zone), corneal asphericity (mean asphericity in 8mm diameter corneal area), and central astigmatism (corneal astigmatism in 3.0-mm central zone). The progression index obtained a mean value of 24.39 ±51.09% and a median of 1.85%. This parameter was significantly related to the baseline sphere, steepest keratometry the 3mm central zone, and mean asphericity in 8mm diameter corneal area. 

More pronounced progression seems to be present in myopic eyes with central localized steepening but normal mid-periphery flattening, researchers said. The index created for this study may predict the level of progression in non-surgically treated keratoconus in the medium-long term, investigators said.