Correlation Between Myopic Refractive Error, Corneal Power and Central Corneal Thickness in the Egyptian Population

Figures & data

Table 1 Statistical Values of Refractive Errors and Corneal Parameters

	Mean	Standard Deviation	Median	Minimum	Maximum
SE	−3.60	1.85	−3.25	−0.75	−8.0
Sphere value	−3.09	1.87	−2.75	0	−8.0
RA	−1.03	0.95	−0.75	0	−4.5
CCT	539.23	32.24	537.00	470.00	638.00
Flat K	42.89	1.59	42.84	38.09	47.86
Steep K	44.14	1.58	44.10	38.41	48.01
KA	1.25	1.08	1.02	0	5.25
Average K	43.52	1.49	43.46	38.25	47.935

Abbreviations: SD, standard deviation; SE, spherical equivalent; RA, refractive astigmatism; CCT, central corneal thickness; KA, keratometric astigmatism.

Table 2 Comparison of Patients’ Data Between Two Age Groups

	18–30 Years					30–40 Years					p-value
	Mean	SD	Median	Minimum	Maximum	Mean	SD	Median	Minimum	Maximum
SE	−3.71	1.84	−3.25	−0.75	−8.0	−3.44	1.7	−3.12	−0.75	−8.0	0.009
Sphere value	−3.2	1.83	−2.75	0	−8.0	−2.92	1.76	−2.75	0	−7.75	0.006
RA	−1.01	0.75	−0.75	0	−4.5	−1.06	0.97	−0.75	0	−4.5	0.42
CCT	541.08	30.76	541.00	470.00	625.00	535.51	34.18	528	470.00	638.00	0.004
Flat K	42.95	1.43	42.9	38.3	47.2	42.77	1.52	42.72	38.09	47.86	0.048
Steep K	44.19	1.54	44.15	38.7	47.2	44.05	1.64	44.00	38.41	48.01	0.15
KA	1.24	0.84	1.00	0	5.25	1.27	0.89	1.07	0.01	5.22	0.46
Average K	43.57	1.43	43.55	38.5	47.6	43.41	1.52	43.34	38.25	47.93	0.077

Abbreviations: SD, standard deviation; SE, spherical equivalent; RA, refractive astigmatism; CCT, central corneal thickness; KA, keratometric astigmatism.

Table 3 Comparison Between Data of Males and Females

	Male					Female					p-value
	Mean	SD	Median	Minimum	Maximum	Mean	SD	Median	Minimum	Maximum
SE	−3.54	1.85	−3.25	−0.75	−8.0	−3.64	1.85	−3.25	−0.75	−8.0	0.347
Sphere value	−2.99	1.87	−2.75	0	−8.0	−3.14	1.86	−2.75	0	−8.0	0.149
RA	−1.09	0.98	−0.75	0	−4.5	−1.00	0.94	−0.75	0	−4.5	0.073
CCT	538.94	31.40	539.00	470.00	627.00	539.39	32.71	536.00	470.00	638.00	0.800
Flat K	42.61	1.43	42.58	38.09	46.60	43.05	1.66	43.00	39.11	47.86	<0.001
Steep K	43.86	1.60	43.82	38.41	47.87	44.30	1.54	44.25	40.02	48.01	<0.001
KA	1.25	0.91	1.00	0	5.22	1.26	1.17	1.04	0	5.25	0.867
Average K	43.24	1.45	43.23	38.25	47.13	43.67	1.49	43.63	39.56	47.93	<0.001

Abbreviations: SD, standard deviation; SE, spherical equivalent; RA, refractive astigmatism; CCT, central corneal thickness; KA, keratometric astigmatism.

Table 4 Correlation Value Between Different Parameters

		Spherical Equivalent (SE) by Absolute Value	Refractive Astigmatism (RA) by Absolute Value	Average K	Keratometric Astigmatism (KA) by Absolute Value	CCT
Refractive astigmatism (RA) by absolute value	r	0.0957
	p-value	<0.001
	N	1401
Average K	r	0.136	0.063
	p-value	<0.001	0.018
	N	1401	1401
Keratometric astigmatism (KA) by absolute value	r	−0.089	0.651	−0.015-
	p-value	0.001	<0.001	0.582
	N	1401	1401	1401
CCT	r	−0.027	0.035	−0.089	−0.018
	p-value	0.314	0.187	0.001	0.512
	N	1401	1401	1401	1401
Age	r	0.036	0.018	−0.018	−0.087	−0.094
	p-value	0.175	0.491	0.508	0.001	<0.001
	N	1401	1401	1401	1401	1401

Abbreviations: SD, standard deviation; SE, spherical equivalent; RA, refractive astigmatism; CCT, central corneal thickness; KA, keratometric astigmatism.

Figure 1 Correlation between spherical equivalent in absolute value and average K showing a statistically significant but weak positive correlation (r = 0.136, p-value <0.001).

Figure 2 Correlation between average k and central corneal thickness showing a statistically significant but weak negative correlation (r = −0.089, p-value = 0.001).

Figure 3 Correlation between absolute value of keratometric and refractive astigmatism showing a statistically significant strong positive correlation (r = 0.651, p-value <0.001).

Figure 4 Correlation between age and central corneal thickness showing a statistically significant but weak negative correlation (r = −0.094, p-value <0.001).