With a few exceptions, glaucoma is typically caused by a build-up of fluid inside the eye. This puts pressure on the optic nerve, damaging it and eventually leading to sight loss.
Occasionally, such as after a blow to the face, glaucoma may develop suddenly. But more often, the development is gradual. As a result, some irreparable damage may have occurred before an individual even knows that they have a problem. That’s one reason why regular sight tests are so important. The sooner that glaucoma is detected, the quicker interventions can take place.
So how do opticians detect glaucoma? Well, with glaucoma arising as a result of increased pressure in the eye, the first test is simply to measure that pressure. This measurement may be taken in a number of ways. The most common of which is the 'puff of air test'. A device called a tonometer sends a puff of air to the eye which compresses it before the eye then quickly bounces back into shape. The bounce back is measured to work out the pressure. The normal range for intraocular pressure is about 10-20mm HG, so regular eye tests will enable the optician to review and track any changes in eye pressure and identify when changes to pressure will require interventions.
The problem with the puff-of-air-test however is that the thickness of the cornea, the front of the eye, impacts the results. Thin corneas can mask increased eye pressure, whilst thick corneas could give rise to unnecessary concerns. A pachymeter is used to measure the thickness of the corner.
Another test commonly carried out is to identify whether any peripheral loss of vision has occurred. This generally requires an individual to press a button whenever they see a flashing light on a screen. Other investigations might include the taking of a photo of the optic nerve as well as viewing the area where the cornea meets the iris to see if any scarring might be preventing fluid from draining away.
Whilst it is not generally possible to reverse existing damage to the optic nerve, it can be possible to prevent any further deterioration. Initial treatments may look to the use of eye drops which are designed to reduce pressure in the eye. Other options include laser or other surgery to open up blocked pores, which may be preventing fluid from draining out of the eye.
Another option which has comparatively recently been offered in the UK is the use of an implant to lower eye pressure. The implant, called MINIject, has thousands of tiny holes which direct the excess fluid in the eye to drain away via an existing drainage network. The procedure can be performed under local anaesthetic either on its own or as an adjunct to cataract surgery.
Interestingly, Occuity has developed a non-contact, handheld device that will allow clinicians and technicians to take a corneal centre thickness measurement in a way that is safer, quicker and easier. The PM1 Pachymeter will be the world’s only non-contact, handheld optical pachymeter, the device which has already been through clinical trials and CE Certification is due to be launched to market later this year.