title: Usefulness of frequency-doubling technology for perimetrically normal eyes of open-angle glaucoma patients with unilateral field loss.
abstract: OBJECTIVE
  To determine whether frequency-doubling technology (FDT) perimetry detects visual field loss in perimetrically normal eyes of patients with open-angle glaucoma (OAG) and whether these visual field defects subsequently are detected by standard automated perimetry (SAP), and to explore the relating factors of the progression from abnormalities based on FDT to visual field loss based on SAP.
  
  
  METHODS
  Prospective cohort study.
  
  
  METHODS
  Sixty-eight OAG patients with unilateral field loss detected by SAP (Octopus, G2 program; Interzeig, Schlieren, Switzerland).
  
  
  METHODS
  Perimetrically normal eyes of participants were examined with the FDT N-30 threshold program (Humphrey Instruments, Welch-Allyn, Skaneateles, NY). The visual field examination was followed by a series of SAP examinations administered over 3 years.
  
  
  METHODS
  The relationship between FDT and subsequent SAP results in perimetrically normal eyes was analyzed. Glaucomatous optic neuropathy (GON), visual field indices, intraocular pressure (IOP), and central corneal thickness (CCT) were compared between converters (eyes with subsequent SAP abnormality) and nonconverters within perimetrically normal eyes with abnormal FDT results. Finally, the SAP test points were matched to the abnormal FDT sectors. The relative risk (RR) of subsequent SAP abnormality corresponding to FDT abnormal sectors was calculated.
  
  
  RESULTS
  Sixty perimetrically normal eyes of 60 participants had complete data and a qualifying follow-up. Baseline FDT results were abnormal in 65%. Of the eyes with abnormal FDT results, 51% developed abnormal SAP results after 4 to 27 months, whereas none of the eyes with normal FDT results developed abnormal SAP results (P<0.05). In perimetrically normal eyes with abnormal FDT results, converters had a greater cup-to-disc ratio, more eyes with GON, larger and deeper cups, and worse FDT mean deviation than nonconverters (P<0.05). The IOP and CCT did not differ between the 2 groups. The RR of subsequent SAP abnormality corresponding to abnormal FDT sectors was 5.38 (95% confidence interval, 3.61-8.04; P<0.05).
  
  
  CONCLUSIONS
  In perimetrically normal eyes of OAG patients, FDT detected visual field loss in almost 2 of every 3 of these eyes and also predicted to some extent future visual field loss on SAP. Severity of glaucomatous neuropathy at baseline was related to conversion of abnormalities on FDT to visual field loss on SAP.
authors.affiliation: Peking University Third Hospital, Peking University Eye Center, Key Laboratory of Vision Loss and Restoration, Ministry of Education, Beijing, People's Republic of China.
authors.forename: Xiang
authors.initials: X
authors.lastname: Fan
authors.forename: Ling-Ling
authors.initials: LL
authors.lastname: Wu
authors.forename: Zhi-Zhong
authors.initials: ZZ
authors.lastname: Ma
authors.forename: Ge-Ge
authors.initials: GG
authors.lastname: Xiao
authors.forename: Feng
authors.initials: F
authors.lastname: Liu
mesh_terms: D000328:Adult; D000368:Aged; D018450:Disease Progression; D005260:Female; D007839:Functional Laterality; D005902:Glaucoma, Open-Angle / Q000175:diagnosis*; D006801:Humans; D007429:Intraocular Pressure; D008297:Male; D008875:Middle Aged; D009901:Optic Nerve Diseases / Q000175:diagnosis*; D011446:Prospective Studies; D018570:Risk Assessment; D014065:Tonometry, Ocular; D014786:Vision Disorders / Q000175:diagnosis*; D058609:Visual Field Tests / Q000379:methods*; D014794:Visual Fields; D055815:Young Adult