Rate of fractional change in corneal tomography parameters in keratoconus using a combination of predictive parameters

Table 1 Difference in value and rate of fractional change in parameters in patients with progressive keratoconus

Parameter		Kf (D)	Ks (D)	Kmax (D)	CA-HOA (µm)	Coma (µm)	SA (µm)	TCT (µm)	ACT (µm)	CCT (µm)	CV7 (mm³)	CV10 (mm³)
Initial visit (x₀)	Mean	51.8	56.7	66.6	8.7	6.1	− 3.5	429.4	446.8	465.6	23.0	57.4
	SD	9.4	10.6	13.5	4.1	3.6	3.9	76.2	72.7	68.4	1.8	4.7
	Median	51.2	56.8	69.1	8.8	5.6	− 3.0	424.5	435	464	22.5	56.7
Follow-up visit (x₁)	Mean	53.2	58.8	70.6	9.8	6.8	− 4.2	406.8	426.0	450.4	22.7	56.9
	SD	10.2	11.1	14.9	5.0	3.7	4.2	71.5	69.9	65.9	1.9	4.9
	Median	52.9	58.6	71	10.2	7.2	− 3.6	400	421	447.5	22.8	57.2
Rate of fractional change*	Mean	0.003	0.005	0.007	0.034	0.076	− 0.024	− 0.007	− 0.007	− 0.005	− 0.002	− 0.001
Rate of fractional change*	SD	0.009	0.008	0.010	0.105	0.140	0.193	0.009	0.010	0.009	0.009	0.010

Kf = flat central keratometry (anterior); Ks = steep central keratometry (anterior); Kmax = maximum keratometry (anterior); CA-HOA = corneal anterior surface higher-order aberrations at 8 mm; SA = spherical aberration, anterior surface at 8 mm; Coma = coma, anterior surface at 8 mm; TCT = thinnest corneal thickness; ACT = apical corneal thickness; CCT = central corneal thickness; CV7 = corneal volume at 7 mm; CV10 = corneal volume at 10 mm; SD = standard deviation
^*Rate of fractional change = (x₁ − x₀)/(|x₀|t_m), where t_m is time in months

ISSN: 2326-0254