Pigment epithelium central limit ‐ Inner limit of the retina, Minimal Distance, PIMD, a morphometrical variable for glaucoma follow‐up

Abstract

PurposeTo establish the resolution of measurements of the minimal distance between the central limit of the pigment epithelium and the inner limit of the retina (PIMD) as measured with OCT.MethodsThe optic nerve head was topographically recorded with OCT (Topcon 3D, OCT‐2000, protocol: 6 × 6 mm 3D disc cube). The minimal distance between the inner limit of the retina and the central limit of the pigment epithelium was sampled 8 times resolved in 500 angles.ResultsThe angular minimal distance was longer in the upper and the lower meridian and averaged 0.21 mm. An analysis of the consequence of the resolution demonstrated that the minimal relevant significant average difference at α = 0.05 and aiming for β = 0.02 was 0.11 change (mm)/Average (mm). Thus, a change of 0.024 mm integrated over 2π is the detection limit at the selected statistical parameters. This corresponds to a local average change within one quadrant of 0.006 mm.ConclusionsPIMD has the potential to be a useful variable for follow‐up of nerve fiber loss in the optic nerve head.