Hidden blind spot and pseudofixation loss

Abstract

Background: Correct mapping of the blind spot is important, as it serves as an estimate of fixation reliability. When the blind spot is not seen in the expected location in Humphrey visual field (HVF) printout, the clinician should give a thought to why this might be the case. Purpose: This video describes a series of cases, in which due to different reasons the blind spot could not be seen in the presumed expected location in the grayscale and numeric data of the HVF printout and the possible explanation behind this. Synopsis: When interpreting perimetry results, it is important to know whether the field test is reliable or not. A stimulus presented at the location of physiologic blind spot should not be seen by a patient with a steady fixation in Heijl-Krakau method. Responses will also occur, however, if the patient has a tendency for false-positive responses, or when the blind spot of the properly fixing eye is not in the location where the test stimulus is presented, because of anatomic variation, or if the patient's head is tilted while performing the test. Highlights: Perimetrist should recognize these potential artifact, during the test and relocate the blind spot. In case, such results are seen after finishing the test, it is recommended for the clinician to repeat the test. Video link: https://youtu.be/I1gxmMWqDQA.