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. 2016 Mar 11;3:6. doi: 10.1186/s40662-016-0038-6

Table 1.

Previously suggested parameters used to determine progression of ectatic disease

Suggested Parameter Value Representing Progression Validated
Spherical power, and higher order irregular astigmatism [32, 35] Positive Rate of Change per Year No
Spherical component, regular astigmatism, decentration component, and higher order irregularity [37] Positive Rate of Change per Year No
Kmax (steepest K) [27, 38] ≥ 1.00 D increase No
Kmax – Kmin [38] ≥ 1.00 D increase No
Kmean (average of Kmax and Kmin) ≥ 0.75 D increase No
Pachymetry [38] ≥ 2 % decrease in central thickness No
Back optic zone radius of the best fitting contact lens [27] 0.1 mm or more decrease No
Increase in the central K power [25] ≥ 1.50 D increase from baseline No
Manifest cylinder [38] Increase of ≥ 1.00 D in 24 months No
Manifest refraction spherical equivalent change (MRSE) [27, 38] ≥ 0.50 D No
ISV [22] Specific values for each KCN stage No
IHA [22] Specific values for each KCN stage No

ISV = index of surface variance, IHA = index of height asymmetry, KCN = keratoconus