Abstract
Purpose: :
to present a new glaucomatous visual field staging system (GVFSS), which intends to provide not only the severity of damage but the location and position in relation to the blind spot, central fixation and number of hemifields involved.
Methods: :
Charts from patients with glaucoma diagnosis submitted to automated perimetry (program 24-2, Swedish Interactive Thresholding Algorithm, Humphrey Field Analyzer II; Carl Zeiss Meditec Inc, Dublin, CA) from January 2005 to September 2008 were reviewed. A visual field criteria was used to establish glaucoma stages. Early, moderate and severe visual field defect were characterized based on the presence of abnormal points with p value less than 1% in the pattern deviation probability map.The new visual field index (VFI) provided by Humphrey Field Analyser was evaluated for each glaucoma stage previously described.The description of visual field defect by the USP Visual Field Staging System is divided in three parts.The first part defines the visual field defect as early (E), moderate (M) or severe (S) according to VFI. The second part reports if the defect is located outside 10 degrees of the visual field (10+), between 5 and 10 degrees (10) or inside 5 degrees of the visual field (5). The third part describes if the visual field defect is located in only one hemifield (1) or in both hemifields (2) and if it connects to the blind spot (B) or not (A) based on points depressed below 0.5% level on the pattern deviation plot.
Results: :
210 eyes with glaucomatous visual field defect were included in this study (58 eyes with early visual field defect, 73 with moderate visual defect and 79 with severe visual field defect). Based on the distribution of VFI values, limits for each group were established considering extreme values and the fact that classifying a more severe visual field defect as less severe would be less acceptable than the opposite situation.The 98th percentile of VFI value in the moderate group ( 91%) was used to establish the limit between early and moderate visual field defect.The limit between eyes with moderate visual field defect and severe visual field defect was based on the 98th percentile of VFI value in the severe group ( 78%).being visual fields with VFI > 78% and ≤ 91 % classified as moderate visual field defect and ≤78% as severe with moderate visual field defect.
Keywords: perimetry • visual fields • clinical research methodology