title: Lack of Association Between Corneal Hysteresis and Corneal Resistance Factor With Glaucoma Severity in Primary Angle Closure Glaucoma.
abstract: OBJECTIVE
  We investigated the association between corneal hysteresis (CH) and corneal resistance factor (CRF) with glaucoma severity in primary angle closure glaucoma (PACG).
  
  
  METHODS
  We recruited 204 subjects with PACG. Each subject underwent CH and CRF measurements using the Ocular Response Analyzer (ORA), optic nerve head topography measurement using scanning laser ophthalmoscopy, and visual field assessment. Glaucoma severity was based on the visual field mean deviation (MD) and classified as mild (71), moderate (55), and severe (78).
  
  
  RESULTS
  The mean age ± SD of study subjects was 68.7 ± 8.9 years, with most being Chinese (n = 186; 91.2%). Corneal hysteresis and CRF were lowest in the severe PACG group (9.32 ± 1.86 and 9.50 ± 1.67 mm Hg) followed by moderate PACG (9.38 ± 1.88 and 9.73 ± 1.88 mm Hg) and mild PACG (9.47 ± 1.90 and 9.85 ± 1.75 mm Hg) respectively, but the differences were not significant (P = 0.89 and P = 0.46, respectively). There was a significant positive correlation between CH and central corneal thickness (CCT; correlation coefficient [r] = 0.26, P < 0.001), CRF and CCT (r = 0.43, P < 0.001), and negative correlation between CRF and vertical cup-disc ratio (VCDR; r = -0.20, P = 0.004), and CRF with cup-disc area (r = -0.14, P = 0.04). Corneal hysteresis and CRF were not correlated with MD (r = 0.01 for CH, r = 0.1 for CRF). After multivariate analyses, adjusting for age, sex, CCT, axial length, intraocular pressure, and number of glaucoma medication, no significant associations were noted between CH and CRF with MD, VCDR, disc area, rim area, or cup area.
  
  
  CONCLUSIONS
  Corneal biomechanical parameters measured by the ORA are not associated with severity of glaucoma in PACG.
authors.forename: Monisha E
authors.initials: ME
authors.lastname: Nongpiur
authors.affiliation: Singapore Eye Research Institute, Singapore 2Duke-NUS Graduate Medical School, Singapore.
authors.forename: Monisha
authors.initials: M
authors.lastname: E Nongpiur
authors.affiliation: Duke-NUS Graduate Medical School, Singapore.
authors.forename: Owen
authors.initials: O
authors.lastname: Png
authors.affiliation: Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
authors.forename: Jestin W
authors.initials: JW
authors.lastname: Chiew
authors.affiliation: Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
authors.forename: Kenric R
authors.initials: KR
authors.lastname: Fan
authors.affiliation: Singapore Eye Research Institute, Singapore 4In Vivo Biomechanics Laboratory, Department of Biomedical Engineering, National University of Singapore, Singapore.
authors.forename: Michael J A
authors.initials: MJ
authors.lastname: Girard
authors.affiliation: Singapore Eye Research Institute, Singapore 5Singapore National Eye Centre, Singapore.
authors.forename: Tina
authors.initials: T
authors.lastname: Wong
authors.affiliation: Singapore National Eye Centre, Singapore.
authors.forename: David
authors.initials: D
authors.lastname: Goh
authors.affiliation: Singapore National Eye Centre, Singapore.
authors.forename: Shamira A
authors.initials: SA
authors.lastname: Perera
authors.affiliation: Singapore Eye Research Institute, Singapore 3Yong Loo Lin School of Medicine, National University of Singapore, Singapore 5Singapore National Eye Centre, Singapore.
authors.forename: Tin
authors.initials: T
authors.lastname: Aung
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena / Q000502:physiology; D003315:Cornea / Q000473:pathology / Q000503:physiopathology*; D003430:Cross-Sectional Studies; D005260:Female; D015812:Glaucoma, Angle-Closure / Q000473:pathology / Q000503:physiopathology*; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology; D008297:Male; D008875:Middle Aged; D012720:Severity of Illness Index