New nonlinear multivariable model shows the relationship between central corneal thickness and HRTII topographic parameters in glaucoma patients

Figures & data

Figure 1 Developed nonlinear multivariable regression model.

Figure 2 Actual and estimated values of the central corneal thickness using the nonlinear multivariable regression model for the data set of 49 eyes measured.

Figure 3 Distribution of corneal thickness according to diagnosis (POAG, NTG, PXF, PG).

Abbreviations: CCT, central corneal thickness; NTG, normal tension glaucoma; PG, pigmentary glaucoma; POAG, primary open-angle glaucoma; PXF, pseudoexfoliative glaucoma.

Table 1 Descriptive statistics per type of glaucoma (mean ± SD)

Parameter	Total	POAG	PXF	NTG	PG
Eyes (n)	49	29	10	5	5
CCT (μm)	549.8 (±33.08)	551.06 (±31.82)	565.60 (±41.42)	530.40 (±19.47)	530.40 (±15.10)
IOP (mmHg)	16.4 (±2.66)	16.82 (±2.91)	14.90 (±1.52)	16.20 (±2.48)	17.20 (±2.58)
Age (years)	61.97 (±12.01)	62.3 (±11.48)	70.4 (±6.25)	57.40 (±10.5)	47.8 (±12.47)
MD (dB)	−3.80 (±4.96)	−3.39 (±4.83)	−3.07 (±2.19)	−10.38 (±7.36)	−1.04 (±1.02)
Disc area (mm^2)	2.131 (±0.385)	2.161 (±0.365)	1.981 (±0.277)	2.465 (±0.589)	1.922 (±0.253)
Cup area (mm^2)	0.788 (±0.493)	0.763 (±0.467)	0.654 (±0.410)	1.410 (±0.503)	0.577 (±0.413)
Cup/Disc area ratio	0.353 (±0.189)	0.339 (±0.184)	0.318 (±0.186)	0.566 (±0.121)	0.291 (±0.185)
Rim/Disc area ratio	0.646 (±0.189)	0.660 (±0.184)	0.681 (±0.186)	0.433 (±0.121)	0.709 (±0.185)
Cup volume (mm^3)	0.249 (±0.273)	0.248 (±0.291)	0.166 (±0.166)	0.502 (±0.323)	0.165 (±0.170)
Rim volume (mm^3)	0.315 (±0.143)	0.327 (±0.136)	0.325 (±0.153)	0.183 (±0.085)	0.360 (±0.172)
CSM	−0.124 (±0.080)	−0.131 (±0.076)	−0.143 (±0.074)	−0.018 (±0.055)	−0.153 (±0.067)
Linear C/D ratio	0.570 (±0.167)	0.561 (±0.158)	0.535 (±0.186)	0.749 (±0.080)	0.516 (±0.173)
FSM	0.252 (±1.978)	0.519 (±1.838)	0.873 (±1.888)	−2.509 (±1.139)	0.226 (±1.733)
MRA*	1.69 (±0.82)	1.48 (±0.68)	1.70 (±0.82)	2.8 (±0.44)	1.80 (±1.09)

Notes: *The values of Moorfields regression analysis can be within normal limits, borderline, outside normal limits, which are represented by the arithmetic values 1 to 3, respectively.

Abbreviations: CCT, central corneal thickness; CSM, cup shape measure; IOP, intraocular pressure; FSM, Frederick S Mikelberg discriminant function; MD, mean defect; MRA, Moorfields regression analysis; NTG, normal tension glaucoma; PG, pigmentary glaucoma; POAG, primary open-angle glaucoma; PXF, pseudoexfoliative glaucoma.

Table 2 R² criterion between the experimental and the predicted values of CCT for simple linear regression model of one input variable

Parameter	R^2	F-test	t-test	F-test (satisfied)	t-test (satisfied)
Age	0.0032	0.1506	−0.3887	No	No
Md	0.0491	2.3063	1.5573	No	No
Refraction	0.0008	0.0390	0.1976	No	No
IOP	0.0093	0.4371	0.6643	No	No
Disc area	0.0242	1.1385	−1.0802	No	No
Cup area	0.1033	4.8547	−2.3268	p < 0.1	p < 0.05
Rim area	0.0777	3.6515	1.9897	p < 0.1	p < 0.1
Rim area temporal	0.0550	2.5867	1.6545	No	p ≈ 0.1
Rim area temp/sup	0.0203	0.9534	0.9865	No	No
Rim area temp/inf	0.0314	1.4780	1.2353	No	No
Rim area nasal	0.1534	7.2109	2.9185	p < 0.01	p < 0.01
Rim area nas/sup	0.0181	0.8498	0.9303	No	No
Rim area nas/inf	0.0341	1.6026	1.2881	No	No
Cup/disc area ratio	0.1099	5.1630	−2.4083	p < 0.05	p < 0.05
Rim/disc area ratio	0.1099	5.1630	2.4083	p < 0.05	p < 0.05
Cup volume	0.1095	5.1485	−2.4045	p < 0.05	p < 0.05
Rim volume	0.0706	3.3172	1.8892	p < 0.1	p < 0.1
Rim volume temporal	0.0683	3.2098	1.8561	p < 0.1	p < 0.1
Rim volume temp/sup	0.0201	0.9444	0.9817	No	No
Rim volume temp/inf	0.0178	0.8371	0.9232	No	No
Rim volume nasal	0.1551	7.2884	2.9370	p < 0.01	p < 0.01
Rim volume nas/sup	0.0115	0.5424	0.7408	No	No
Rim volume nas/inf	0.0341	1.6031	1.2883	No	No
Min cup depth	0.0388	1.8238	−1.3775	No	No
Max cup depth	0.0061	0.2872	−0.5376	No	No
Height variation contour	0.0180	0.8467	0.9286	No	No
CSM	0.0648	3.0454	−1.8046	p < 0.1	p < 0.1
Mean RNFL thickness	0.0518	2.4354	1.6026	No	No
RNFL thickness temporal	0.0307	1.4439	1.2205	No	No
RNFL thickness temp/sup	0.0239	1.1238	1.0730	No	No
RNFL thickness temp/inf	0.0756	3.5555	1.9612	p < 0.1	p < 0.1
RNFL thickness nasal	0.0495	2.3285	1.5652	No	No
RNFL thickness nas/sup	0.0306	1.4384	1.2181	No	No
RNFL thickness nas/inf	0.0259	1.2186	1.1185	No	No
RNFLcross sectional area	0.0432	2.0323	1.4575	No	No
Linear c/d ratio	0.0783	3.6815	−1.9986	p < 0.1	p < 0.1
Max. Contour elevation	0.0227	1.0662	−1.0445	No	No
Max. Contour depression	0.0001	0.0070	−0.0836	No	No
CLM temporal superior	0.0178	0.8388	0.9241	No	No
CLM temporal inferior	0.0702	3.2971	1.8830	p < 0.1	p < 0.1
Average variability SD	0.0007	0.0328	−0.1811	No	No
Reference height	0.0058	0.2732	0.5243	No	No
FSM discriminant function	0.0823	3.8686	2.0532	p < 0.1	p < 0.05
RB discriminant function	0.0517	2.4277	1.6000	No	No
Cup area temporal	0.0582	2.7360	−1.7044	p ≈ 0.1	p < 0.1
Cup area temp/sup	0.0574	2.6984	−1.6920	p ≈ 0.1	p < 0.1
Cup area temp/inf	0.1103	5.1825	−2.4134	p < 0.05	p < 0.05
Cup area nasal	0.1213	5.6991	−2.5467	p < 0.05	p < 0.05
Cup area nasal/sup	0.0649	3.0505	−1.8062	p < 0.1	p < 0.1
Cup area nasal/inf	0.1352	6.3532	−2.7104	p < 0.05	p < 0.01
Cup volume temporal	0.0868	4.0803	−2.1138	p ≈ 0.05	p < 0.05
Cup volume temp/sup	0.0659	3.0992	−1.8215	p < 0.1	p < 0.1
Cup volume temp/inf	0.1386	6.5143	−2.7500	p < 0.05	p < 0.01
Cup volume nasal	0.0804	3.7769	−2.0266	p < 0.1	p ≈ 0.05
Cup volume nasal/sup	0.0426	2.0007	−1.4456	No	No
Cup volume nasal/inf	0.1205	5.6637	−2.5377	p < 0.05	p < 0.05
CSM temporal	0.0446	2.0958	−1.4811	No	No
CSM temp/sup	0.0085	0.3987	−0.6341	No	No
CSM temp/inf	0.0756	3.5512	−1.9600	p < 0.1	p < 0.1
CSM nasal	0.0021	0.0978	−0.3130	No	No
CSM nasal/sup	0.0176	0.8256	−0.9167	No	No
CSM nasal/inf	0.0066	0.3082	−0.5570	No	No
Diagnosis	0.1113	5.2317	−2.4263	p < 0.05	p < 0.05
MRA	0.1100	5.1702	−2.4102	p < 0.05	p < 0.05

Notes: *The last two variables (diagnosis, MRA) are linguistic ones, so it was necessary to modify them.

^† The values of diagnosis can be PXF, POAG, PG, NTG, which are represented by the arithmetic values 1 to 4, respectively. This variable is omitted in the cases of different models for each kind of glaucoma diagnosis.

^‡ The MRA values can be within normal limits, borderline, outside normal limits, which are represented by the arithmetic values 1 to 3, respectively.

Abbreviations: CCT, central corneal thickness; CSM, cup shape measure; CLM, contour line modulation; IOP, intraocular pressure; FSM, Frederick S Mikelberg discriminant function; MD, mean defect; MRA, Moorfields regression analysis; NTG, normal tension glaucoma; RB, Renuka Bathija; RNFL, retinal nerve fiber layer; PG, pigmentary glaucoma; POAG, primary open-angle glaucoma; PXF, pseudoexfoliative glaucoma.