Pupil-based detection of asymmetric glaucomatous damage - comparison of the Konan RAPDx pupillograph, swinging flashlight method, and magnifier-assisted swinging flashlight method

Abstract

Purpose: Afferent pupillary defect (APD) testing is most commonly performed using the swinging flashlight method (SFM). The magnifier-assisted SFM (MA-SFM), which involves holding a +20-diopter lens in front of the eye being examined, has previously been found to increase the sensitivity of APD detection. Pupillography devices, such as the Konan RAPDx, may also allow for improved APD detection, while providing objective measurements of pupil response parameters. This study aims to compare the ability of the RAPDx pupillograph with the SFM and MA-SFM in the detection of asymmetric glaucomatous damage.

Methods: 118 patients presenting to the glaucoma service underwent full clinical examinations and APD testing with the SFM, MA-SFM, and RAPDx pupillograph. Each test was performed by separate examiners who were blinded to the patient’s clinical information and to the results of the other tests. Using the SFM and MA-SFM, an apparently positive APD was defined by the presence of immediate or delayed pupillary dilation. Using the RAPDx pupillograph, an apparently positive APD was defined by a calculated index of defect, Amp_c, greater than 0.2 (representing the negative log of the difference between the amplitudes of constriction in one eye versus the other). An APD (positive SFM, positive MA-SFM, or Amp_c > 0.2) was considered “corroborated” when there was a difference of (a) ≥ 1 Disc Damage Likelihood Scale unit between both eyes or (b) ≥ 0.1 cup/disc ratio between both eyes.

Results: 22/118 (18.6%) patients were unable to complete pupillography testing for reasons such as ptosis and irregular or fixed pupils. 39/118 patients were excluded because of retinal disease or insufficient clinical data. Apparent APDs were detected in 15/57 (26.3%), 35/57 (61.4%), and 35/57 (61.4%) by the SFM, MA-SFM, and RAPDx, respectively. “Corroborated” APDs were found in 9/57 (15.8%), 21/57 (36.8%), and 22/57 (38.6%) by the SFM, MA-SFM, and RAPDx, respectively. Clinically detected asymmetry in disc damage was missed in 28/57 (49.1%), 12/57 (21.1%), and 12/57 (21.1%) by the SFM, MA-SFM, and RAPDx, respectively.

Conclusions: The RAPDx pupillograph and MA-SFM are useful tools in the detection of asymmetric glaucomatous damage and are able to detect apparent and “corroborated” APDs more often than the SFM.

Keywords: 668 pupillary reflex • 667 pupil • 550 imaging/image analysis: clinical