Table 2

Comparison between the three groups (DS group, mild keratoconus group and control group) in relation to pachymetry, corneal volume and corneal aberrometry of the posterior surface

	DS group				Mild keratoconus group				Control group				P value
	Cases, no.	Minimum	Maximum	Mean (SD)	Cases, no.	Minimum	Maximum	Mean (SD)	Cases, no.	Minimum	Maximum	Mean (SD)	DS group – mild keratoconus group	DS group – control group	Mild keratoconus group – control group
Pachymetry, µm
Central	37	425	552	497.68±26.88	45	443	620	500.56±36.83	40	482	603	538.95±31.67	0.77	<0.001	<0.001
Nasal	37	495	650	552.08±34.35	45	511	678	572.40±33.41	40	537	671	606.45±37.94	0.005	<0.001	<0.001
Temporal	37	458	593	525±29	45	478	672	541.71±33.51	40	521	649	574.45±33.86	0.07	<0.001	<0.001
Superior	37	506	652	561.16±32.92	45	524	694	585.33±33.37	40	552	677	618.85±34.52	0.001	<0.001	<0.001
Inferior	37	481	586	535.81±26.84	45	477	657	557.93±34.99	40	525	650	593.43±34.90	<0.01	<0.001	<0.001
Corneal volume (Ø=10 mm), mm³
Corneal volume	37	48.6	61	53.69±3.23	46	49.8	64.9	55.61±3.06	40	48.3	62.7	57.39±3.40	<0.05	<0.001	<0.05
Corneal aberrometry (posterior surface), µm
Total RMS	37	0.17	6.79	1.21±1.55	45	0.21	1.82	0.70±0.42	40	0.14	0.61	0.28±0.10	0.82	<0.001	<0.001
High-order RMS	37	0.11	6.1	1.07±1.43	45	0.15	1.54	0.56±0.36	40	0.07	0.33	0.15±0.06	0.75	<0.001	<0.001
Primary coma RMS	37	0.01	3.36	0.32±0.64	45	0.02	0.72	0.23±0.20	40	0	0.09	0.05±0.02	<0.05	0.001	<0.001
Primary spherical aberration RMS	37	−0.22	2.2	0.19±0.43	45	−0.12	0.34	0.06±0.09	40	−0.03	0.07	0.01±0.03	0.44	<0.01	<0.01
Coma-like RMS	37	0.08	4.74	0.88±1.09	45	0.12	1.47	0.51±0.34	40	0.05	0.32	0.13±0.07	0.78	<0.001	<0.001
Spherical-like RMS	37	0.04	3.84	0.59±0.94	45	0.04	0.61	0.23±0.13	40	0.03	0.14	0.07±0.27	0.74	<0.001	<0.001

DS, Down syndrome; RMS, root mean square.