An Update on Corneal Biomechanics and Architecture in Diabetes

Table 1

Summary of prospective cross-sectional studies of CH, CRF, IOPg, and IOPcc in diabetes patients.

Author, year, country	Study groups/sample size	Mean age (years)	ORA parameters (mean mmHg) controls/diabetes	Outcomes (P value)	Associations
Goldich, 2008, Israel [108]	40 with diabetes (40 eyes)/40 controls (40 eyes)	60.9/63.8	CH: 10.7 ± 1.6/9.3 ± 1.4	0.0001	(i) Subjects with diabetes had higher CH and CRF values than those without diabetes
			CRF: 10.9 ± 1.7/9.6 ± 1.6	<0.0001
			IOPcc: 16.6 ± 4.4/17.7 ± 4.9	0.31	(ii) There was no any statistical difference between the groups in terms of IOPg and IOPcc.
			IOPg: 16.6 ± 4.3/16.1 ± 4.9	0.66
Sahin, 2009, Turkey [109]	43 with diabetes (81 eyes)/61 control (120 eyes)	55.3/53.1	CH: 9.51 ± 1.82/10.41 ± 1.66	0.0001	(i) CH was found to be significantly lower in diabetic patients
			CRF: 10.32 ± 1.76/10.36 ± 1.97	0.8	(ii) There was no significant difference in terms of CRF
			IOPcc: 18.81 ± 4.71/15.85 ± 3.24	0.0001	(iii) Mean CCT, GAT, IOPg, and IOPcc were significantly higher in diabetic patients than in healthy control subjects
			IOPg: 17.68 ± 4.42/15.34 ± 3.66	0.0001
Castro, 2010, Brazil [92]	44 primary open-angle glaucoma patients)		CH: 9.1 ± 1.9/7.8 ± 1.7	0.04	Diabetic patients presented significantly higher CH values than patients without diabetes. There was a significant and positive correlation between CH and CCT for all patients (r = 0.407, ).
	19 with diabetes (34 eyes)/25 without diabetes (40 eyes
Kotecha, 2010, UK [110]	61 with diabetes (61 eyes)	41.9/61.6/54.0	CH: 12.45 ± 1.74/10.90 ± 1.94/10.85 ± 1.68 CRF: 12.49 ± 2.01/11.50 ± 2.06/10.62 ± 1.64	0.008	(i) The CH was significantly greater in T1D patients.
	T1D (13 eyes)/T2D (48 eyes)/controls (123 eyes)			0.0001	(ii) The CRF was significantly greater in T1D and T2D patients.
					(iii) CH and CRF were weakly correlated with blood glucose concentration
Kara, 2012, Turkey [99]	46 T1D children (46 eyes)/50 controls (50 eyes)	14.2/14.5	CH: 12.3 ± 1.3/12.5 ± 1.5	0.609	(i) CH and CRF in T1D are similar to those of healthy controls.
			CRF: 12.4 ± 1.7/11.9 ± 1.5	0.152	(ii) IOPg and IOPcc in T1D are similar to those of healthy controls.
			IOPg: 17.4 ± 3.6/16.7 ± 2.9	0.232
			IOPcc: 15.5 ± 3.4/15.1 ± 2.7	0.446
Nalcacioglu-Yuksekkaya, 2014, Turkey [111]	68 T1D children (68 eyes)/74 controls (74 eyes)	12.7/12.9	CH: 10.8 ± 1.5/10.7 ± 1.7	0.624	(i) CH and CRF in T1D are similar to those of healthy controls.
			CRF: 10.9 ± 1.9/10.5 ± 1.6	0.207	(ii) IOPg and IOPcc in T1D are similar to those of healthy controls.
			IOPcc: 15.8 ± 3.0/15.3 ± 3.4	0.395
			IOPg: 15.9 ± 3.7/15.2 ± 3.4	0.263
Yazgan, 2014, Turkey [112]	156 with T2D (156 eyes)/74 controls (74 eyes)	57.75/57.91	CH: 10.37 ± 1.9/8.98 ± 1.4	0.0001	CH, CRF, CCT, IOPg and IOPcc values were higher in diabetes groups than controls. There was also a positive correlation between HbA1C level and intraocular pressure.
			CRF: 11.06 ± 2.3/8.99 ± 1.5	0.0001
			IOPg: 17.63 ± 3.9/14.80 ± 2.9	0.0001
			IOPcc: 17.70 ± 3.2/16.56 ± 2.4	0.026
Pérez-Rico, 2015, Spain [113]	94 diabetic patients (94 eyes)	59.8/62.2	CH: 10.23 ± 1.83/10.9 ± 1.39/11.43 ± 1.69	0.002	(i) CH was significantly lower in diabetic patients with elevated HbA1c than in controls and was affected by disease duration, whereas the CRF remained unaltered.
	54 uncontrolled diabetes/40 controlled diabetes/41 controls		CRF: 11.05 ± 1.97/11.21 ± 1.97/10.53 ± 1.78	0.263	(ii) IOPcc and IOPg were significantly higher in diabetic patients with elevated HbA1c than in controls.
			IOPcc: 18.45 ± 3.79/14.68 ± 2.67/14.55 ± 3.72	<0.0001
			IOPg: 18.16 ± 3.85/15.31 ± 3.14/14.46 ± 4.1	<0.0001
Schweitzer, 2016, France [91]	Diabetes (137 eyes)/controls (695 eyes)	—	CH: 9.79/9.28	0.003	Subjects with diabetes had higher CH and CRF values than those without diabetes. Consistently, subjects having fasting blood glucose values greater than or equal than 7.0 mM had significantly higher CH and CRF mean values compared with subjects having fasting blood glucose values lower than 6.1 mM (P < 0.05).
			CRF:10.35/9.63	0.003
Akkaya, 2016, Turkey [93]	101 primary open-angle glaucoma patients (101 eyes)		CH: 9.35  ± 1.49/8.86 ± 1.52	0.11	(i) CH in diabetes was similar to those of healthy controls.
	60 with diabetes (60 eyes)/41 without diabetes (41 eyes)		CRF: 10.15  ±  1.78/9.24 ± 1.92	0.01	(ii) RNFL thickness was measured by using Spectralis HRA + OCT.
					(iii) CRF, mean rim area, and rim volume were found to be significantly higher in the diabetic group when compared with nondiabetic group.
Bekmez, 2018, Turkey [114]	50 with T2D (50 eyes)/50 controls (50 eyes)	63.3/61.7	CH: 9.9 ± 1.5/10.5 ± 1.7	0.080	(i) There was no any statistical difference between the groups in terms of CH and CRF. However, mean CH and CRF values were found less in diabetic group.
			CRF: 10.4 ± 1.6/10.5 ± 1.7	0.730
			IOPcc: 17.8 ± 3.6/16.0 ± 3.1	0.006	(ii) Corneal biomechanical differences seen in diabetic patients may be associated with significantly higher IOP measurements.
			IOPg: 16.9 ± 3.5/15.4 ± 2.9	0.032

T1D = type 1 diabetes; T2D = type 2 diabetes; ORA = ocular response analyzer; CH = corneal hysteresis; CRF = corneal resistance factor; GAT = Goldmann applanation tonometry; IOP = intraocular pressure; CCT = central corneal thickness; IOPg = Goldmann-correlated intraocular pressure; IOPcc = corneal-compensated intraocular pressure.