Visual field testing (perimetry) is the cornerstone of glaucoma assessment. It is a means of assessing peripheral vision sensitivity in one’s eye. Up until very recently, perimetry has only been possible on dedicated machines. These machines represent a barrier to accessing healthcare for many people; they are large, cumbersome, labour intensive and expensive. Clearly there are many advantages for online perimetry that could be performed on any computer. Online perimetry is easier to use, a more enjoyable experience and more easily accessible than machine-based perimetry. It represents significant cost savings for both patients and clinicians.
As an Ophthalmologist and busy glaucoma specialist in Melbourne, thousands of my patients are performing such testing annually; I am acutely aware of the limitations of machine-based visual field testing. It is unpleasant for my patients, it slows down the clinic, the machines are expensive to acquire and maintain, and require a great deal of staff involvement. Clearly there is a great benefit to provide a new way of performing perimetry, that is more intuitive, user-friendly, and can work on any computer. That is precisely what we at Eyeonic have developed with the online Eyeonic visual field test.
But how is it possible to provide perimetry that works on any computer?
Surely there is a reason why complex, single-purpose equipment is considered necessary.
Eyeonic is an Australian health-tech company that has taken on the challenge of delivering online perimetry for any computer.
Eyeonic is passionate about improving eye health globally by making evidence-based online vision testing accessible to everyone. Yes there are logistical hurdles, but we have considered these, using all the advantages of widespread modern technology to overcome them.
The challenges that online perimetry must overcome include:
Screen Size Variation
Different computer screens come in different sizes, and different aspect ratios (ratio of height to width)
Different Screen Parameters
Screen display can vary in several ways, including brightness, contrast, gamma (which is the relationship between the coded color and the screen output) and the white tone.
Variations within screen display
Even within an individual screen the display can vary; for example, especially for older screens, the centre of the display is brighter than the corners.
Controlled testing environment
For vision testing, the room lighting, spectacle correction, head position, and closure of the other eye are all critical for testing success. It is vital these factors are controlled with clear instructions to the user to ensure testing validity.
So how do we do it?
Here are the features that make online visual field testing possible.
Spinning Fixation Target
The central target is a spinning golden star. Conventional machine based perimetry use a motionless dot of light, which is hard to keep staring at. We have found a slowly rotating fixation target is easier to maintain gaze on, and our users agree!
Flickering Test Target
Most conventional perimetry machines use small spots of white light against a dark background; the brightness of the spot determines the ease or difficulty of seeing the target. This works well for dedicated perimetry machines, but the small variations between screens and within a screen make this method not great for computer-based, online visual field testing. In comparison contrast testing works well for perimetry delivered on computer screens. For contrast testing the target is a flickering target, and it’s brightness is determined by the difference between light and dark bars. These differences are more resilient to different screen types, and are more resistant to variations within the screen. This is because they do not rely on a diffuse background; rather the difference in contrast within the target.
Viewing Distance Adjusted for Screen Size
Computer monitors come in different sizes; Eyeonic’s test needs to work on them all. By measuring the screen size, the Eyeonic app can place the test specifically for that monitor, and determine the correct viewing distance for that monitor type. In general, people sit closer for smaller screens, and further back for larger screens, to maintain a constant visual angle.
Blind Spot Localisation
We all have a blind spot – not just a figurative one, but a real one in our vision! This is the area corresponding to where the optic nerve enters the eye, and there is no sensitive retinal tissue. It is generally located 15 degrees to the outside of midline. Finding the blind spot is an important component of Eyeonic’s online visual field test. It helps determining the right head position relative to the screen, and ensures the test is being performed correctly.
Monitor Calibration
As mentioned above monitors can have different parameters set (eg brightness, contrast, gamma) which can affect test performance. The online Eyeonic visual field test can detect a non-calibrated monitor early on and guide the user through a simple calibration process.
User Head Position
It is important that for anyone taking the online vision test their head position remains constant. To achieve this, the app engages the user’s webcam which monitors their head position – should this move to close to the screen, far from the screen, too far left or right, the test pauses and the user corrects their position.
Through the combination of our features, texted and perfected through a vigorous scientific evaluation process, Eyeonic’s visual field test can provide perimetry on any computer accurately, enjoyably and with improved access and convenience to machine-based visual field testing.
Clearly there is a great benefit to provide a new way of performing perimetry, that is more intuitive, user-friendly, and can work on any computer. That is precisely what we at Eyeonic have developed with the online Eyeonic visual field test.