title: Corneal viscoelastic differences between pseudoexfoliative glaucoma and primary open-angle glaucoma.
abstract: OBJECTIVE
  The aims of this study were to assess the biomechanical properties of corneas with pseudoexfoliative glaucoma (PEXG) and to compare them with those of patients with primary open-angle glaucoma (POAG).
  
  
  METHODS
  This prospective, comparative case series consisted of 73 eyes of 73 patients, 35 eyes with PEXG (PEXG group) and 38 eyes with POAG (POAG group). Corneal hysteresis (CH), corneal resistance factor (CRF), corneal-compensated intraocular pressure (IOPCC), and Goldmann-correlated intraocular pressure (IOPG) were determined by using ocular response analyzer (ORA). IOP using Goldmann applanation tonometer (GAT) and ultrasonic central corneal thickness (CCT) were also measured for each eye. Exclusion criteria included refractive error/astigmatism of >3.00 D, history of intraocular surgery, corneal disease, angle-closure glaucoma, and secondary glaucoma other than PEXG. In cases where both eyes were eligible, the right eye was preferred for analysis. The main outcome measures were CH, CRF, IOPCC, IOPG, and GAT. The results were statistically analyzed by using t test, general linear model, and the Pearson correlation test.
  
  
  RESULTS
  The mean CH was found to be significantly lower in patients with PEXG (8.8 ± 1.4 mm Hg) than those with primary open-angle glaucoma (9.9 ± 1.2 mm Hg; P=0.0007). The mean CRF was found to be significantly lower in patients with PEXG (9.5 ± 1.8 mm Hg) than those with POAG (11.1 ± 1.3 mm Hg; P<0.0001). IOPCC was not significantly different between the groups (PEXG, 16.7 ± 2.5 mm Hg; POAG, 16.9 ± 2.4 mm Hg; P=0.72). IOPG was significantly lower in PEXG group (14.7 ± 2.7 mm Hg) compared with the POAG group (16.5 ± 2.5 mm Hg; P=0.004). GAT was significantly lower in the PEXG group (14.6 ± 2.7 mm Hg) compared with the POAG group (16.4 ± 2.8 mm Hg; P=0.007). There was no significant difference between the groups regarding mean CCT (PEXG, 546.1 ± 34.9 μ; POAG, 549.1 ± 25 μ; P=0.66) and mean age (PEXG, 70.3 ± 8.2; POAG, 67.6 ± 8.8; P=0.17). The difference between the IOPCC and the GAT was 2.1 and 0.5 mm Hg in both PEXG and POAG groups, respectively.
  
  
  CONCLUSIONS
  Patients with PEXG had lower CH and CRF values than those with POAG. These findings require further investigation to assess the role of differing corneal biomechanical properties between the 2 groups and its association with poor prognosis among patients with PEXG.
authors.affiliation: Department of Ophthalmology, Cerrahpasa School of Medicine, Istanbul University, Istanbul, Turkey.
authors.forename: Ahmet
authors.initials: A
authors.lastname: Ozkok
authors.forename: Nevbahar
authors.initials: N
authors.lastname: Tamcelik
authors.forename: Akif
authors.initials: A
authors.lastname: Ozdamar
authors.forename: Ahmet M
authors.initials: AM
authors.lastname: Sarici
authors.forename: Erdogan
authors.initials: E
authors.lastname: Cicik
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D003315:Cornea / Q000503:physiopathology*; D063171:Corneal Pachymetry; D004548:Elasticity / Q000502:physiology*; D017889:Exfoliation Syndrome / Q000503:physiopathology*; D005260:Female; D005902:Glaucoma, Open-Angle / Q000503:physiopathology*; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D015203:Reproducibility of Results; D014065:Tonometry, Ocular; D014794:Visual Fields