Wearable HFA-compliant Visual Field Analyzer

Abstract

Purpose : We present a compact, wearable Humphrey-compliant perimeter (SVF, screening visual field) able to operate in any environment for the 24-2 self-examination. The device delivers Goldmann III stimuli from 1000 to 0.1 asb over a background of 3.14 asb, so to be suitable for screening.

Methods : The compactness of the SVF and its compliance with HFA were the main guidelines for the design. The stimuli are generated at 116 mm from the eye and delivered to the patient through a single close-up lens. The SVF is conceived to let the patient wear his own spectacles. Each stimulus is generated by an LED located in an appropriate hole behind an almost-opaque surface, which appears uniform when the stimuli are turned off. Since the stimuli pattern and the lens position are fixed, no moving parts are needed and the device results very compact and robust. The SVF has a large pupil to allow eye decentering and tilting, so it simplifies the self-alignment procedure, that is obtained thanks to a pupil camera and an OLED display. The pupil camera is also used during the exam to monitor the gaze of the patient and assess his fixation stability. The OLED, inserted in the path through a beam-splitter, displays some messages and provides the blind-spot examination. The eye under examination is automatically recognized. Over time the alignment is kept because the SVF is wearable and consequently unaffected by patient’s head movements. Finally, it is completely isolated by the surrounding environment, thus suppressing the room light during examinations. The device is powered directly by USB-C connection to a laptop or tablet, where a dedicated SW drives the patient through all operations, allowing a complete self-examination. The current strategy has an average duration of about 4’ per eye on healthy patients.

Results : The SVF is light and comfortable to wear. It provides complete isolation from room light, allowing to use it in any environment to perform visual field test examinations. It has been studied to be inexpensive. The exam has a short duration. Thus, it is suitable for screening. The HFA-compliance has been successfully tested on 20 healthy volunteers.

Conclusions : This work demonstrates that a compact device able to perform visual field tests with no moving parts and no room light interference is possible. Results are encouraging and open the way for a refinement of the proposed ideas.

This is a 2020 Imaging in the Eye Conference abstract.

 

The SVF prototype

 

The SVF optical layout