Evaluation of Corneal Structure and Endothelial Morphological Characteristics in Type 2 Diabetic and Non-Diabetic Patients

Figures & data

Table 1 Demographic and Clinical Characteristics of the Study Population

Variable	DM Group (n= 60)	Non-DM Group (n= 47)	P
Age, years	72 ± 6	70 ± 6	0.050^A
Female, n (%)	38 (63%)	29 (62%)	0.863^C
Right eyes, n (%)	30 (50%)	18 (38%)	0.227^C
BMI, kg/m^2	27.9 ± 4.0	28.1 ± 5.0	0.847^A
Smoking history, n (%)	14 (23%)	18 (38%)	0.093^C
Systemic Hypertension, n (%)	49 (82%)	33 (70%)	0.165 ^C
Dyslipidemia, n (%)	50 (83%)	21 (45%)	<0.001 ^C
HbA1c levels, %	7.0 ± 1.1	5.5 ± 0.4	<0.001*^B
Duration of DM, years	11.0 ± 8.0	n/a	n/a
DR stage, n (%)
No DR	42 (70%)	n/a	n/a
NPDR mild-moderate	10 (17%)
NPDR Severe - PDR	8 (13%)
Oral antidiabetic agents, n (%)	56 (93%)	n/a	n/a
Insulin treatment, n (%)	15 (25%)	n/a	n/a

Notes: Data were derived from Independent samples t-test^A, Mann–Whitney test^B, Chi-square test^C. Continuous variables are reported as mean ± standard deviation. *P <0.05, statistical significance.

Abbreviations: BMI, body mass index; DM, diabetes mellitus; DR, diabetic retinopathy; HbA1c, glycated hemoglobin; kg/m², kilogram per meter square; NPDR, non-proliferative DR; PDR, proliferative DR; n/a, not applicable.

Table 2 Ocular Characteristics of the Study Population

Variable	DM Group (n= 60)	Non-DM Group (n= 47)	P
CCT ^§, μm	558 ± 35	559 ± 30	0.876^A
Corneal volume, mm^3	60.6 ± 4.0	60.0 ± 3.3	0.399^A
ECD, cell/mm^2	2375 ± 304	2449 ± 349	0.245^A
Average cell size, mm^2	428.3 ± 56.9	418.2 ± 69.3	0.410^A
CV of cell size, %	35.4 ± 5.9	34.8 ± 6.3	0.566^A
Hexagonal cells, %	55.8 ± 7.5	55.2 ± 8.7	0.712^A
Counted cells per eye, n	102 ± 20	94 ± 266	0.088^B

Notes: Data were derived from Independent samples t-test^A and Chi-square test^B. Continuous variables are reported as mean ± standard deviation. ^§ CCT (central corneal thickness) measured by Pentacam at corneal vertex.

Abbreviations: CV, coefficient of variation of cell size; DM, diabetes mellitus; ECD, endothelial cell density; mm, millimeter; mm², square millimeter; mm³, cubic millimeter; μm, micrometer.

Table 3 Subgroup Analysis of Diabetic Patients

Variable		DM Duration, Years	HbA1c, %	DR, n (%)	CCT ^§, μm	Corneal Volume, mm^3	ECD, Cell/mm^2	CV of Cell Size, %	Hexagonal Cells, %
DM Duration, years	<10 (n=30)	4.9 ± 2.4	6.6 ± 0.8	4 (13%)	557 ± 38	60.4 ± 4.4	2404 ± 295	35.8 ± 5.2	55.8 ± 8.1
	≥ 10 (n=30)	17.1 ± 7.0*	7.4 ± 1.3*	14 (47%)	559 ± 32	60.9 ± 3.6	2347 ± 314	35.1 ± 6.6	55.9 ± 7.0
HbA1c Levels, %	< 7.0(n=31)	7.6 ± 5.8	6.2 ± 0.5	5 (16%)	554 ± 39	60.0 ± 4.2	2370 ± 329	35.6 ± 6.5	54.9 ± 8.7
	≥ 7.0(n=29)	14.6 ± 8.6*	7.9 ± 1.0*	13 (45%)	562 ± 29	61.3 ± 3.8	2381 ± 279	35.3 ± 5.3	56.8 ± 5.8
DR	No (n=42)	8.4 ± 6.1	6.8 ± 1.1	–	556 ± 36	60.4 ± 4.3	2395 ± 310	35.7 ± 5.6	54.8 ± 7.0
	Yes (n=18)	17.1 ± 8.9*	7.4 ± 1.3*	–	563 ± 32	61.3 ± 3.3	2330 ± 293	34.9 ± 6.7	58.2 ± 8.2

Notes: Continuous variables are reported as mean ± standard deviation. *P <0.05, statistical significance. ^§ CCT measured by Pentacam at corneal vertex.

Abbreviations: CV, coefficient of variation of cell size; DM, diabetes mellitus; DR, diabetic retinopathy; ECD, endothelial cell density; CCT, central corneal thickness; HbA1c, glycated hemoglobin; mm, millimeter; mm², square millimeter; mm³, cubic millimeter; μm, micrometer.

Table 4 Multivariate Regression Analysis of the Relative Effects of Clinical and Ocular Characteristics on Endothelial Cell Density (ECD) and Central Corneal Thickness (CCT)

Variable	CCT, μm		ECD, Cell/mm^2
	B (95% CI)	P	B (95% CI)	P
Age, years
≤ 70 years	–	–	–	–
>70 years	−1.21(−7.83 to +5.41)	0.721	−140.14(−264.85 to −15.43)	0.028*
Female	−13.39 (−19.64 to −7.14)	<0.001*	−85.22 (−213.69 to +43.26)	0.194
CCT, μm	–	–	−1.50 (−5.13 to +2.13)	0.417
Corneal volume, mm^2	+7.61 (+6.73 to +8.48)	<0.001*	+25.60 (−6.39 to +57.59)	0.117
ECD, cell/mm^2	−0.004 (−0.01 to +0.01)	0.421	–	–
DM duration
Non-DM	–	–	–	–
No DR	−5.27 (−11.94 to +1.39)	0.121	−41.02(−169.98 to +87.94)	0.533
DR present	−6.31 (−15.03 to +2.40)	0.156	−142.20(−308.70 to +24.30)	0.094

Notes: Data were derived from generalized linear models. *P <0.05, statistical significance.

Abbreviations: B, beta coefficient; CI, confidence interval; CCT, central corneal thickness; DM, diabetes mellitus; ECD, endothelial cell density; CCT, central corneal thickness; mm, millimeter; mm², square millimeter; mm³, cubic millimeter; μm, micrometer. The remaining variables (smoking history, body mass index, systemic hypertension, dyslipidemia, axial length, intraocular pressure, HbA1c levels, diabetic retinopathy stage) did not influence the model and were excluded.