Treating glaucoma is based on lowering the intraocular pressure (IOP). The aim is to slow the progression of disease. Unfortunately vision already lost cannot be restored. The choices of treatment are usually recommended in the following order:
- Medicines (eye drops)
Studies show that IOP follows a 24 hour circadian rhythm, typically peaking at night-time or early morning. This is true in healthy subjects and in patients with glaucoma.1-9 Given the association between non-uniform 24 hour IOP and progression of visual field damage in patients with NTG (normal tension glaucoma) and POAG (primary open angle glaucoma), it is important to control IOP over the full 24 hour period.10-12
The medicinal treatment of glaucoma normally continues for the rest of your life. For long-term treatment you should consider preservative free eye drops to ensure optimal tolerability of the medication. Medications work either to reduce the amount of aqueous humour (e.g. beta-blockers) or increase the drainage of aqueous humour (e.g. prostaglandin analogue drops). It is essential that you use the medicine as advised by your doctor, because it helps only if used properly.
Different categories of drops13
The drugs used in eye drops to treat glaucoma fall into various categories, according to the way they work.
Prostaglandin/prostamide analogues (bimatoprost, latanoprost, tafluprost and travoprost)
The action is to increase the flow of fluid out of the eye through surrounding tissue rather than through the usual drainage structures of the eye. The drops are used once a day, usually at night. Possible side effects include a pink/red eye that usually improves over a period of time. The iris may darken in colour (more commonly in those with green or hazel eyes and less commonly in blue eyes). Eyelashes may grow longer and darker and, in a small percentage of patients, the skin around the orbit of the eye may darken.
Beta blockers (timolol, carteolol, levobunolol and betaxolol)
The action of these drops is to reduce the production of fluid in the eye. They are used once in the morning or twice a day, as advised by your ophthalmologist. They are not usually prescribed for anyone susceptible to chest or breathing problems. Possible side-effects include a slow pulse, dizziness, asthma and tiredness. In some people these drops may cause depression, loss of libido or impotence. However, most people have no problems with them.
Carbonic anhydrase inhibitors (brinzolamide and dorzolamide)
The action of these drugs is to reduce production of fluid in the eye. These drops are used two or three times a day on their own, or twice a day if with another drop. Possible side-effects include burning sensation in the eye, a bitter taste in the mouth, headache and fatigue.
Alpha agonists (apraclondine and brimonidine)
The action is to reduce the production of fluid in the eye and to improve the flow of fluid out of the eye. They are usually used two or three times a day. Brimonidine is licensed for the long-term treatment of glaucoma but apraclonidine is for short-term use following, or to delay, laser treatment. Brimonidine is contra-indicated for children under the age of two years. Possible side effects include a dry mouth, tiredness and general weakness.
Occasionally a few people may develop a severe allergic reaction to these drops. If this happens, the eye becomes increasingly red, sore and sticky. Sometimes it can take several months for this to happen. If it does develop, you should consult your ophthalmologist or GP without delay.
Cholinergic agonist (pilocarpine)
The action is to improve the flow of fluid out of the eye through its usual route and the drops are used three or four times a day. Possible side effects include headache and red eye.
If you need two different types of medication, using a combination drop can have advantages over using two drops separately. It saves both time and having to keep two different bottles. It also means that you deliver less preservative to the eye, which may reduce the possibility of developing an allergic reaction to the preservatives. However, with the exception of one combination eye drop, all contain timolol, which may not be suitable for some patients because of possible side effects with the use of beta-blockers.
As an alternative, laser treatment (laser trabeculoplasty) aims at improving the outflow of the aqueous humour, in order to decrease the pressure – at least for a few years. If despite medical or laser therapy glaucoma progresses, surgical treatment may be used.13
The primary goal of glaucoma surgery is to achieve a target IOP without additional medication.13
The most common form of glaucoma surgery is trabeculectomy. This is a procedure to relieve IOP by removing part of the eye's trabecular meshwork and adjacent structures. It allows drainage of aqueous humor from within the eye to underneath the conjunctiva, where it is absorbed.13
The alternatives to trabeculectomy in open angle glaucoma include non-penetrating surgery and drainage devices.13
Santen MicroShunt is a glaucoma drainage device indicated for reduction of IOP in the eyes of patients with primary open angle glaucoma where IOP remains uncontrollable while on maximum tolerated medical therapy and/or where glaucoma progression warrants surgery.14
This device is inserted via an ‘ab externo’ surgical procedure and is made of a very inert bio-material called SIBS that has 15 year track record of use in coronary stents.15
The Santen MicroShunt device received a CE Mark on 9 January 2012 in Europe. In the United States a multicentre clinical trial is under way comparing the MicroShunt device to primary trabeculectomy in patients whose IOP is not sufficiently controlled with medication.15
- Agnifili L et al. Acta Ophthalmol 2015;93:e14–21
- Aptel F et al. J Glaucoma 2017;26:272–7
- Costa VP et al. Br J Ophthalmol 2010;94:1291–4
- Grippo TM et al. Invest Ophthalmol Vis Sci 2013;54:512–7
- Huang R et al. J Glaucoma 2015;24:550–5
- Lee YR et al. Invest Ophthalmol Vis Sci. 2012;53:881–7
- Mansouri K et al. Invest Ophthalmol Vis Sci. 2012;53:8050–6
- Mansouri K et al. Br J Ophthalmol 2011;95:627–9
- Mosaed S et al. Am J Ophthalmol 2005;139:320–4
- Ishida K et al. J Glaucoma 1998;7:372–7
- Konstas AG et al. J Ocul Pharmacol Ther 2012;28:26–32
- Sakata R et al. Invest Ophthalmol Vis Sci 2013;54:5313–20
- European Glaucoma Society. Br J Ophthalmol 2017;101:146-50
- SANTEN MICROSHUNT GLAUCOMA DRAINAGE SYSTEM Instructions for use
- Pinchuk L et al. Regen Biomater 2016;3:137–42