Pressure on optometrists to treat glaucoma is likely to grow as case numbers are predicted to rise 44% by 2035. Beta blockers will remain a part of the fight ahead, as Adrian O’Dowd reports.
Around 480,000 people in England have chronic primary open angle glaucoma (POAG) (Moorfields, 2019). Estimates of population prevalence for ocular hypertension (OHT) range from 4.5% to 9.4% for those over 40 years old (Burr et al, 2012), and 10% of those with untreated OHT will develop POAG within five years (COptom, 2018).
The Royal College of Ophthalmologists predicts that, between 2015 and 2035, glaucoma cases will rise by 44% (RCOphth, 2017).
Beta blockers or PGAs?
In 2009, NICE recommended that prostaglandin analogues (PGAs) should be the first choice of treatment for patients with glaucoma. NICE also recommended PGAs be used for patients with treatable OHT if their corneas were less than 555μm thick. Beta blockers were recommended for use in treatable OHT if the patient’s corneas were 555 to 590μm thick, providing they were not contraindicated – in which case a PGA should be used.
However, with the arrival of cost-effective generic PGAs, NICE changed its guidance in 2017 to recommend treatment with PGAs for patients with OHT who have intraocular pressure of 24mmHg or above, if they are at risk of visual impairment within their lifetime. Although corneal thickness is no longer mentioned specifically, it will be taken into account by the prescriber in determining whether the patient is at risk of visual impairment.
But beta blockers are not fading into insignificance. Daniel Hardiman-McCartney FCOptom, Clinical Adviser for the College, says: “Recent prescribing data shows that around 33% of items prescribed by GP practices for the treatment of glaucoma in England contain a beta blocker [Open Prescribing, 2019]. Although the use of stand-alone beta blockers is decreasing, a notable number of people will continue to be prescribed them as a combination therapy for the foreseeable future.”
Optometrists should be able to identify the side effects of both PGAs and beta blockers as part of active care for their patients (see Side effects).
Gus Gazzard, Director of the Glaucoma Service at Moorfields Eye Hospital, says side effects should be considered in all clinical decisions.
“The one situation in which people would knowingly not prescribe PGAs as first-line treatment would be when you are treating only one eye and you are concerned about the monocular side effects,” he says.
“PGAs can give you orbital fat atrophy, where the eye sinks back into the socket. It is asymmetric and can be very disfiguring. And there are rare occasions where one might choose a beta blocker, such as a past history of herpes simplex virus in the cornea because that can be reactivated. Some clinicians choose a non-prostaglandin as first line in the presence of previous uveitis in the context of macular oedema, but that is rare.
“Other side effects are often missed by people who are not thinking about them, such as depression, nightmares, vivid dreams and even psychosis that can occur with beta blockers. I’ve had a patient become almost suicidal on topical medication.”
A first choice?
For some patients, beta blockers may be the best treatment choice. Gus says: “The most common reason for moving to beta blockers is that people will not tolerate PGAs or that they do not work.”
Daniel agrees that beta blockers are very well tolerated in the eyes themselves, compared with PGAs, which can cause a red and irritated eye appearance.
Systemic side effects are caused by absorption into the bloodstream, mostly via the nasal mucosa. Rana et al (2015) have recorded side effects from the use of timolol, including bradycardia, hypoglycaemia, and falls/dizziness in one case study, although another (Ramdas et al, 2009) found patients using beta blockers were no more likely to have falls or suffer dizziness or orthostatic hypotension than those using PGAs.
However, these side effects can be minimised by closing the eyes following application and using punctal occlusion to prevent the drug from entering the tear drainage duct and systemic circulation.
Professor Philip Bloom, Consultant Ophthalmic Surgeon at Imperial College Healthcare NHS Trust and Chairman of the International Glaucoma Association, says beta blockers can be used safely as long as they are prescribed appropriately and the patient is monitored.
“They are a very effective medication, tried and tested,” says Philip. “They are predominantly quite safe and very well tolerated. They are also relatively inexpensive and widely available. The fact that they are available as combinations improves compliance and tolerability.”
Somehow, people don’t make the connection with beta blockers and breathing problems or fatigue
Overall health
Optometrists must observe the whole picture of a patient’s health and be vigilant when spotting the signs of potential side effects.
Daniel says: “Patients with glaucoma often have the benefit of having a nurse practitioner talking them through how to apply eye drops, but this is not always the case. As primary eye care specialists, optometrists should reinforce these messages and pick up on any issues that have been missed. The main emphasis should be on talking to the patient about how they are getting on and what their symptoms are.
“A lot of clinicians are taught about the effects of beta blockers, but somehow people don’t make the connection with breathing problems or fatigue. All optometrists can pick up on these symptoms during the routine sight test when proactively asking about them.”
These links are more likely to be detected by optometrists than GPs, he says: “Primary care optometrists are in a better position to pick up on these more subtle symptoms and join the dots together to highlight it as a concern with the clinician who prescribed the drug.”
Spotting side effects can be life-saving, Gus explains: “I recently saw a patient who narrowly escaped severe and life-threatening side effects of beta blockers because he had the common sense to look at the leaflet insert and sought help. Somebody had given him beta blockers without considering the fact that he had a particular cardiac arrhythmia which rendered him high risk.
“I’ve seen one patient end up in intensive care and many patients become severely ill because of the injudicious use of beta blockers. That can be down to the health professional or the patient not making the link or forgetting to tell them something.”
Patient confidence
Another issue is whether patients are completely happy with their treatment or may be using it ineffectively.
Helen Doe manages the Sightline telephone helpline that provides advice, information and support to people with glaucoma for charity the International Glaucoma Association.
She says: “We have callers who can’t take the beta blocker drop and they then worry about what else there is. We can reassure them there are other options.
“On the other hand, a lot of people don’t like the side effects of the prostaglandin, especially women, who ask about the darkness under their eyes.
“It is greatly important to take into account the patient’s overall health before treating them as long as the patient has told the optometrist everything.”
Another common problem is patients having problems putting the drops in, says Helen. “There are many compliance aids for people that we can advise on, and we can also invite people to look at our website because we have video demonstrations of how to put drops in.
“It would be really helpful if optometrists checked how the patient is putting the drops in. It is amazing how many people think they are doing it correctly but they’re not.
Side effects of beta blockers and PGAs
PGAs: eye colour change, darkening of eyelid skin, eyelash growth, droopy eyelids, sunken eyes, stinging, eye redness and itching.
Beta blockers: low blood pressure, fatigue, shortness of breath; (rarely) reduced libido, depression and sleep disturbance.
Future treatment
Despite the reliability of the most common eye drop treatments, glaucoma is likely to be treated differently in coming years, according to Philip. “Laser treatment is increasing in traction in terms of primary treatment.”
He says that the LiGHT study (Gazzard et al, 2019) shows that selective laser trabeculoplasty (SLT) is equivalent to drops at lowering IOP and probably
more cost-effective.
“Probably, between 5% and 10% are being treated initially by SLT now and that number will increase,” Philip says. “That will reduce the need for drops and means they will start using them later on in the course of their disease.”
However, for the time being, Gus concludes: “It is important to note that beta blockers remain an important, useful and powerful medication for lowering eye pressure.”
10% of those with untreated OHT will develop POAG within five years. (COptom, 2018)
33% of items prescribed by GP practices for the treatment of glaucoma in England contain a beta blocker. (Open Prescribing, 2019)
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