Association between Combined Structure Function Index and Glaucoma Severity

Figure 1

Formula for calculating CSFI and SAP rgc is obtained from the eccentricity (degrees) and OCT rgc from age (years) and MD. Values of SAP rgc and OCT rgc thus obtained are balanced by MD to calculate wrgc. OCT rgc accounts for a greater proportion in the early stage and SAP rgc for a greater proportion in the advanced stage. Age-corrected normal RGC (expected RGC), the denominator of CSFI, is calculated from the disc area (mm²) on OCT and age, so that the rate of loss of wrgc is expressed as the CSFI (%). SAP, standard automated perimetry; OCT, optical coherence tomography; RGC or rgc, retinal ganglion cell; CSFI, combined structure function index; MD, mean deviation; RNFL, retinal nerve fiber layer.