Abstract
PurposeA newly developed head-mounted perimeter termed “imo” enables visual field (VF) testing without a fixed head position. Because the positional relationship between the subject’s head and the imo is fixed, the effects of head position changes on the test results are small compared with those obtained using a stationary perimeter. However, only ocular counter-roll (OCR) induced by head tilt might affect VF testing. To quantitatively reveal the effects of head tilt and OCR on the VF test results, we investigated the associations among the head-tilt angle, OCR amplitude and VF testing results.Subjects and methodsFor 20 healthy subjects, we binocularly recorded static OCR (s-OCR) while tilting the subject’s head at an arbitrary angle ranging from 0° to 60° rightward or leftward in 10° increments. By monitoring iris patterns, we evaluated the s-OCR amplitude. We also performed blind spot detection while tilting the subject’s head by an arbitrary angle ranging from 0° to 50° rightward or leftward in 10° increments to calculate the angle by which the blind spot rotates because of head tilt.ResultsThe association between s-OCR amplitude and head-tilt angle showed a sinusoidal relationship. In blind spot detection, the blind spot rotated to the opposite direction of the head tilt, and the association between the rotation angle of the blind spot and the head-tilt angle also showed a sinusoidal relationship. The rotation angle of the blind spot was strongly correlated with the s-OCR amplitude (R2≥0.94, p<0.0001). A head tilt greater than 20° with imo causes interference between adjacent test areas.ConclusionsBoth the s-OCR amplitude and the rotation angle of the blind spot were correlated with the head-tilt angle by sinusoidal regression. The rotated VF was correlated with the s-OCR amplitude. During perimetry using imo, the change in the subject’s head tilt should be limited to 20°.
Highlights
A head-mounted perimeter termed “imo” (CREWT Medical Systems, Inc., Tokyo, Japan) is a newly developed portable standard automated perimeter (SAP) that was released in 2015 [1]
Both the s-ocular counter-roll (OCR) amplitude and the rotation angle of the blind spot were correlated with the head-tilt angle by sinusoidal regression
The rotated visual field (VF) was correlated with the static OCR (s-OCR)
Summary
A head-mounted perimeter termed “imo” (CREWT Medical Systems, Inc., Tokyo, Japan) is a newly developed portable standard automated perimeter (SAP) that was released in 2015 [1]. Because the imo is compact, it can be carried and used to test the visual field (VF) anywhere. Using the imo, highly accurate measurement results can be obtained with examination times nearly equivalent to those of widely used SAPs such as the Humphrey Field Analyzer (HFA) (Carl Zeiss Meditec, Dublin, CA, USA) and Octopus perimeter (Haag-Streit, Koeniz, Switzerland). Because the imo is head-mounted, subjects do not need to fix their head position during an examination. Patients who could not previously participate in VF testing with a stationary perimeter might be able to undergo perimetry with the imo. The positional relationship between the subject’s head and the imo is fixed; the effects of head position changes on VF measurements are small compared with those obtained with the stationary perimeter. Only ocular counter-roll (OCR) induced by head tilt might affect VF testing
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