Purpose:
To explore the rate of conversion from ocular hypertension to glaucoma by progression analyses on visual fields and scanning laser polarimetry.
Methods:
Four hundred sixteen subjects with ocular hypertension (intraocular pressure (IOP) ≥22 and ≤32 mmHg and normal visual fields) were measured every 6 months with a Humphey Field Analyzer (HFA, 24-2 program; Carl Zeiss Meditec (CZM), Dublin, USA) and with scanning laser polarimetry (GDxVCC and GDxECC; Carl Zeiss Meditec, Dublin, USA). Conversion to glaucoma was defined by either Guided Progression Analysis (GPA) (HFA-II-i, Software Version 4.2, CZM; GDx Review with GPA; Software Version 6.0.1, CZM) software of all 3 techniques flagging ‘likely progression’ or, in case of HFA, a negative rate of progression that was statistically significant, or in case of GDxVCC, a nerve fiber indicator (NFI) > 35 on at least 3 consecutive measurements. Two hundred and thirty five eyes of 132 subjects could be used for the progression analyses.
Results:
63 of the 235 eyes converted to glaucoma. The Venn Diagram shows the number of converting eyes for the 3 techniques. Of the 6 cases showing conversion in both the HFA and GDxVCC, 5 showed conversion in VCC by a reproducible NFI > 35.
Conclusions:
Both GDxECC and GDxVCC flagged glaucomatous conversion more often than did the HFA. There was little overlap between conversion shown in the HFA and the GDx. There was only moderate overlap between the GDxVCC and GDxECC in flagging conversion. To detect conversion of ocular hypertension to glaucoma, we recommend monitoring with scanning laser polarimetry in addition to visual field testing.
Keywords: visual fields • imaging/image analysis: clinical • nerve fiber layer