Glaucoma still is the number one cause of preventable blindness in the Western world and is still a silent condition until it’s very late. Thus, it is worth remembering its importance and that of screening.
Glaucoma is the commonest form of optic neuropathy where the optic nerve, which comprises approximately 1.5 million nerve fibres subserving all visual functioning from vision to brightness to movement to colour etc., decays earlier than it should do in life.
This is typically due to increased eye pressure relative to the eye’s tolerance to that pressure. Genetic, vascular, and other unknown and untreatable factors also play a role but, in essence pressure, control is the treatment mainstay.
One of the modalities of monitoring glaucoma is the visual fields progress. Figure 1 shows a very characteristic pattern. The patient is slowly losing (note the time frame) the superior component of the visual field corresponding to a defect forming in the inferior part of the optic nerve. This can be seen with the ophthalmoscope and is represented below in the Heidelberg (HRT) scan showing the inferior notching of the nerve (Figure 2).
When we examine for glaucoma, we tend to examine the triad of intraocular pressure, the appearance of the nerve and the visual fields. No one thing in isolation typically can make the diagnosis.
Fortunately, through extensive epidemiological studies and increased awareness and improved screening by our optometrist colleagues, we are picking it up much earlier and therefore can intervene sooner. The greatest risk of severe glaucoma remains late detection in terms of progression.
Another major risk is genetic susceptibility – accounting for about 20%. Myopia or short sightedness tends to increase the risk of glaucoma as does migraine and lower blood pressure, presumedly because of impaired optic nerve head perfusion.
The fundamental treatment for glaucoma is still to get the pressure down and keep it down to an acceptable target pressure. This can be done via a range of modalities – a range drops would cover more than 90% of patient treatment. Often some adjunct laser or laser options are used, sometimes these are a primary treatment. Finally surgical options are used to lower the pressure in a small percentage of people.
Traditional trabeculectomy is still an excellent procedure, which is now challenged by MIGS or minimally invasive glaucoma surgery. While these techniques have shown great promise, they are still presenting their share of problems as with any device in terms or complications and efficacy.
Some MIGS devices beyond the scope of this article for researching include Xen stents, iStents, pressrflo stents and others such as the Hydrus. Having a considerable experience with the above, a traditional trabeculectomy is still a good option having the benefit of decades of data collection, but others are showing promise (and problems). No glaucoma surgery is without these. There is a next level shunt group for more severe and secondary glaucoma, also when other treatments have been exhausted.
Primary or open angle glaucoma is still by far the most significant glaucoma to concentrate on and unfortunately at medical school the feared acute angle glaucoma was pushed so hard as to colour our view about glaucoma, when, in fact, it probably represents 1% per year in the at-risk population, which is incredibly small.
In real numbers, it’s probably seen approximately once a year in a glaucoma practice. There is an in between phenomena which is referred to as chronic angle closure but is be treated as open angle glaucoma except one of the fundamentals is either lens removal (cataract), or peripheral iridotomy, which is becoming increasingly rare in my practice, especially with improved and safer lens/cataract surgery.
Just as general screening for other medical conditions is commonplace – prostate, breast, blood pressure etc. – glaucoma screening, which can certainly start at an optometry level, is still a fundamental part of a general health check which shouldn’t be overlooked.
Key messages
- Glaucoma remains an extremely common, treatable and challenging condition with devasting results if undetected
- Early detection and specialist referral is the key
- New surgical treatments are emerging but traditional surgery and drops remain mainstay treatment.
Author competing interests – nil