The role of corneal hysteresis during the evaluation of patients with possible normal-tension glaucoma

Figures & data

Figure 1 What is hysteresis and CH?

Notes: Hysteresis is the difference in the behavior of the material between loading and unloading (eg, rubber band). CH is the difference between the pressure at which the cornea bends inward and the pressure at which the cornea bends outward.
Abbreviation: CH, corneal hysteresis.

Table 1 Chronological list of studies correlating CH and glaucoma

Study	Findings
Congdon et al,^Citation11 2006	Low CH, not CCT, is associated with progression of visual field loss over 5 years
Bochmann et al,^Citation12 2008	CH is lower in patients with acquired pits of the optic nerve independent of IOP
Sullivan-Mee et al,^Citation13 2008	CH is lower in patients with glaucoma than patients with OHTN, GS, or normal eyes independent of other risk factors
Wells et al,^Citation14 2008	Low CH is associated with increased mean cup depth independent of CCT and IOP
Abitbol et al,^Citation15 2010	CH is lower in glaucomatous eyes than normal eyes, not independent from CCT
Anand et al,^Citation16 2010	In asymmetric POAG, CH is significantly lower in the eye with more glaucomatous damage as defined by VF independent of IOP and CCT
Hirneiss et al,^Citation17 2011	In asymmetric POAG, there is no statistically significant difference between CH between the two eyes
Narayanaswamy et al,^Citation18 2011	CH is significantly lower in patients with PACG compared to normal eyes
Grise-Dulac et al,^Citation19 2011	CH is significantly lower in patients with NTG than in patients with POAG or normal eyes
Morita et al,^Citation20 2011	CH is significantly lower in patients with NTG, and CCT did not show a statistically significant difference
Mansouri et al,^Citation21 2012	Low CH was not associated with glaucomatous damage on multivariate analysis
De Moraes et al,^Citation22 2012	Multivariate analysis demonstrating that CH has a stronger correlation with glaucomatous progression than CCT
Kaushik et al,^Citation23 2012	CH is significantly lower in patients with POAG and NTG in comparison to normal subjects independent of IOP and CCT on multivariate analysis
Prata et al,^Citation24 2012	Low CH is associated with increased cup-to-disc ratio and mean cup depth, independent of IOP and disc size
Vu et al,^Citation25 2013	CH best correlates with mean deviation on VF in comparison to other structural markers of glaucomatous damage

Abbreviations: CH, corneal hysteresis; CCT, central corneal thickness; GS, glaucoma suspect; IOP, intraocular pressure; NTG, normal-tension glaucoma; OHTN, ocular hypertension; PACG, primary angle closure glaucoma; POAG, primary-open angle glaucoma; VF, visual field.

Table 2 Characteristics of study subjects

Characteristics N=# of eyes	NTG, N=21	Non-glaucoma eyes, N=55	P-value
Age, years,	75.6±6.9	78.5±7.9	0.1473
mean ± SD
Gender			0.1692
Female	14 (66.7)	27 (49.1)
Male	7 (33.3)	28 (50.9)
lOPc, mmHg	15.1±2.9	14.4±2.8	0.3063
CH, mmHg	9.1±0.4	8.9±0.7	0.1922
lOPg, mmHg	12.9±3.3	11.8±3.2	0.1820
CCT, mm	513.0±21.1	513.5±21.9	0.8129
c/d	0.6±0.2	0.5±0.2	0.0253
OCT	75.3±7.6	94.8±6.8	<0.0001
Laterality
Right	11 (52.4)	29 (52.7)	0.9784
Left	10 (47.6)	26 (47.3)
BCVA			0.2046
20/25	7 (33.3)	11 (20.0)
20/30	8 (38.1)	16 (29.1)
20/40	3 (14.3)	22 (40.0)
20/50	2 (9.5)	3 (5.5)
20/60	1 (4.8)	3 (5.5)
Pseudophakia	21 (100)	47 (85.5)	0.0975
DM	3 (14.3)	11 (20.0)	0.7453
Other CV RF	17 (81.0)	37 (67.3)	0.2744
Asymmetry	0 (0.0)	3 (5.5)	0.5564

Note: Asymmetry indicates cup/disc (c/d) asymmetry between two eyes.

Abbreviations: BCVA, best-corrected visual acuity; CH, corneal hysteresis; CCT, central cornea thickness; c/d, cup/disc ratio; CV RF, cardiovascular risk factor; DM, diabetes mellitus; IOP, intraocular pressure; IOPc, compensated IOP reading with ORA; IOPg, Goldmann equivalent IOP read by ORA; NTG, normal-tension glaucoma; OCT, optical coherence tomography; ORA, ocular response analyzer.

Figure 2 The percentage of NTG after screening those with the low CH (below 10) by OCT and visual field.

Abbreviations: NTG, normal-tension glaucoma; OCT, optical coherence tomography.

Table 3 Comparison between two groups with respect to CH and average thickness of RNFL

Characteristic	NTG, n=21	Non-glaucoma eyes, n=55	P-value
CH, mmHg	9.1±0.4	8.9±0.7	0.19
OCT (average thickness of RNFL, mm)	75.3±7.6	94.8±6.8	<0.001

Abbreviations: CH, corneal hysteresis; NTG, normal-tension glaucoma; OCT, optical coherence tomography; RNFL, retina nerve fiber layer.

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