Abstract
Purpose :
Diagnostic delay in identifying intracranial pressure (ICP) elevation may lead to permanent visual impairment or profound neurological disability. Invasive, poorly tolerated methods currently used have associated clinical risk. Optical Coherence Tomography (OCT) and retinal infrared (IR) video offer a non-invasive, non-contact imaging method. Absence of spontaneous venous pulsation (SVP) on IR video alongside OCT optic nerve head (ONH) swelling raises suspicion of elevated ICP.
However, OCT is typically table-top mounted, installed in primary eye care centres or hospital ophthalmology departments and is inaccessible in acute or high dependency care settings. We aim to establish the feasibility of OCT, OCT-Angiography (OCTa) and IR video as a bedside investigation for acutely unwell hospital inpatients including intensive care.
Methods :
The Heidelberg Flex™ imaging system is a flexible and mobile ophthalmic imaging solution with a highly capable imaging head mounted on a flexible arm on a wheel-based structure. One individual using a foot pedal took images in healthy control and conscious hospital inpatients laying supine. Three individuals were needed to image unconscious patients. One individual held patients’ heads still and lids open, one operated the computer interface and one operated the imaging head. Due to the flexibility of the mobile imaging head, it was possible to capture ONH imaging independent on patient fixation, a significant advantage in unconscious patients. Hypromellose 0.3% eye drops were used prior to imaging for unconscious patients. No mydriatic drops were used.
Results :
OCT and OCTa box scans plus IR en-face video centred on the ONH were acquired from both eyes for all conscious study patients. OCT videos, positioned to intersect a main branch of the retinal vein, were also captured. OCTa was not possible on unconscious patients due to poor fixation and lack of patient blink. OCT video failed to identify SVP possibly due to the fact that several images are averaged to produce each frame. However, SVP was clearly detectable on IR en-face video.
Conclusions :
The Heidelberg Flex™ imaging system presents a useful method to non-invasively confirm normal ICP in acutely unwell hospital inpatients, including intensive care patients. En-face IR video is more effective than OCT video in identifying SVP and thus normal ICP.
This is a 2021 ARVO Annual Meeting abstract.