Eye gaze

Also called Eye tracking, Eye control, Gaze access, Eye-gaze technology

Choosing by looking: a camera under the screen tracks the eyes, and a steady gaze on a cell selects it. Fast, hands-free, and fussier than it looks.

What it is

Eye gaze is direct selection with the eyes. A small bar under the screen shines a safe infrared light at the face and a camera works out where each eye is pointing. A pointer follows the gaze, and looking at a cell for a set time (dwell selection), blinking, or pressing a switch selects it.

It is the access method that most changes what is possible for people who cannot move much else, and it is also the method with the most ways to go wrong.

Who it can help

People who can control their eyes but little else: motor neurone disease, cerebral palsy with severe physical involvement, Rett syndrome, spinal muscular atrophy, locked-in syndrome, high spinal injury. Children as young as two have used it for choosing and play.

It is harder for people with nystagmus, a squint, ptosis, very thick glasses, cortical visual impairment, or an involuntary head movement that takes the eyes out of the camera's box. It needs stable seating and a stable screen. And it is tiring: holding a gaze deliberately for hours is work, and a person with a working hand or head is usually better off with that.

How it works

The camera needs to see both eyes (or one, on some systems) within a box roughly 30 by 20 centimetres, about 50 to 70 centimetres from the screen. Calibration teaches it this person's eyes by having them look at a few points. From then on the software maps gaze to screen position at up to dozens of times a second.

Selection is by dwell (typically 0.5 to 1.5 seconds), by a blink of set length, or by a switch. Cells are large, because gaze accuracy is around a centimetre at best and worse at the edges. Modern eye-gaze bars attach to a tablet or Windows device; dedicated systems build the camera into the device. The whole thing lives on a mount, because the camera-to-eye geometry must not change.

Getting started

Ask for a trial before anything else; eye gaze is expensive and the only way to know is to try it on the person, seated as they normally are, on a good day and a bad one. Start with cause-and-effect games and big-target choosing, not a communication grid, so the person learns what looking-to-choose feels like.

Meanwhile, practise the low-tech version: an alphabet board or a clear perspex E-tran frame held between you, where the person looks at a letter and you read it. It proves the eyes can point and it is the backup for every eye-gaze user for ever.

Where to get help

Eye gaze for communication is assessed and, for eligible people, funded by the specialised AAC services commissioned by NHS England; the route in is an AAC assessment via your speech and language therapist. The ACE Centre and CALL Scotland publish free eye-gaze guides, Tobii Dynavox and Smartbox make the main systems used in the UK, and the MND Association can advise on timing for people whose needs are changing fast.