Medicine treatment of glaucoma in Australia 2012–2019: prevalence, incidence and persistence

Introduction

Glaucoma is a chronic, blinding, neurodegenerative disease of the optic nerve, the incidence and progression rate of which increases with increasing intraocular pressure (IOP). It affects approximately 3% of Australians 50 years and older and increases exponentially with age.1 It is the leading cause of irreversible, preventable blindness in Australia and the world.2–4 There is no cure for glaucoma, but early detection and treatment with medicines to reduce IOP can halt or significantly slow the progression of vison loss and preclude more invasive surgical interventions. Clinical practice guidelines recommend topical eye drops as a first treatment option to prevent damage to the optic nerve by reducing pressure in the eye(s); followed by laser treatment in conjunction with or as an alternative to drops.2 5

As a chronic condition, glaucoma requires persistent treatment for optimum management. Most medical treatments are topical and administered once or two times per day, for as long as they are effective. However, research using electronic bottle monitoring found that people do not consistently take their prescribed antiglaucoma eye drops in 45% of cases.6 Other factors, such as difficulty instilling eye drops, mental and physical health conditions and forgetfulness present challenges to optimal adherence7

In Australia, population-based estimates of persistence to incident treatments have been reported at less than 40% at 12 months, dropping further to 24% at 24 months.8 However, this research is over a decade old and the contemporary patterns of glaucoma medicine use and persistence in the country are unclear. Therefore, we aimed to describe the use of glaucoma medicines in Australia using contemporary, population-based data. We detailed the incidence and prevalence of glaucoma therapy between 2012 and 2019 and estimated the persistence to glaucoma treatment in a cohort of people initiating glaucoma medicines.

Data sources and methods

Results

Between 2013 and 2019, a total of 2 865 309 PBS-listed glaucoma medicines were dispensed to 67 785 people 18 years and older. Prostaglandin analogues (PA) accounted for 43% of all glaucoma medicine dispensings across the period, followed by FDCs (32%) and carbonic anhydrase inhibitors (CAIs) (9.4%).

Prevalence of glaucoma medicine treatment

The annual prevalence of treatment remained consistent across the study period; 180 per 10 000 population in 2013 and 184 per 10 000 population in 2019 (online supplemental table B). Prevalence of treatment increased with each age group and peaked among people aged 85 years and older (figure 1/ online supplemental table B). PAs were the most prevalent glaucoma medicine, followed by FDCs and CAIs (online supplemental table B). Women had slightly higher treatment prevalence than men throughout the study period.

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Figure 1

Prevalence (left) and incidence (right) of glaucoma medicine treatment by age group.

Incidence of glaucoma medicine treatment

Incidence also remained stable across the study period; with 36 new users per 10 000 population in 2013 and 37 new users per 10 000 population in 2019 (online supplemental table C). Incidence was similar between sexes and increased with each age group, peaking in ages 75–84 years (figure 1).

Persistence to treatment

Among the 34 900 people initiating glaucoma medicines during 2014–2019, 37.0% remained on treatment at 6 months from initiation, 29.8% at 12 months and 19.2% at 36 months (figure 2; online supplemental table D). The most frequently initiated treatments were PAs (42.2%), CAIs (23.1%) and sympathomimetics (10.2%; table 1). Most people were prescribed 4–6 repeats or zero repeats at initiation (table 1). With a median follow-up time of 31.3 months (IQR: 12.6–51.4), the median time on any glaucoma treatment was 2.3 months (IQR: 1.0–19.2). Treatment duration varied by the number of repeats prescribed at initiation, with those prescribed 4–6 repeats having the longest median treatment duration, 8.5 months (IQR: 1.7–51.5) and those prescribed zero repeats have the shortest treatment duration, 1.0 months (IQR: 1.0–1.0; online supplemental figure A). The median treatment duration was 13.2 months (IQR: 2.5—not reached) for those initiating PAs but less than 3 months for people initiating all other medicine classes (figure 3; online supplemental table D). Persistence increased with age—the proportion of people who remained on treatment at 12 months from initiation was 35.8%, 40.4% and 43.9%, respectively, among ages 65–74 years, 75–84 years and 85 years and older (figure 4; online supplemental table D).

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Figure 2

Persistence with glaucoma medicine treatment. Main analysis (90-day period with no dispensings used to define a treatment break) shown in green; sensitivity analyses (30-day and 180-day periods used to define treatment break) shown in red and blue. NR, not reached.

Table 1

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Characteristics of people initiating glaucoma medicines (2014–2019), included in persistence analysis

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Figure 3

Persistence with glaucoma medicine treatment, by initiated medicine (90 days used to define treatment break). FDC, fixed-dose combinations; NR, not reached.

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Figure 4

Persistence with glaucoma medicine treatment, by age group (90 days used to define treatment break).

Discussion

Persistence with glaucoma medicines is crucial for treatment efficacy and our study suggests that most people in Australia have suboptimal persistence. Our national, population-based study highlights that only one-third of people initiating treatment remained on treatment 6–12 months following initiation. Such a low rate of persistence has implications for treatment efficacy—if these medicines are not being used in accordance with recommended guidelines, efficacy estimates from clinical trials may not be translating to the real world. Progression of glaucoma can often be managed with these treatments and our findings represent a potentially significant public health issue for Australia. While treatment persistence increased with age, and glaucoma is primarily a condition of old age,2 our findings suggest the need for targeted interventions to improve treatment adherence in Australia.

Persistence and adherence to topical glaucoma therapy is a long standing challenge, with people self-reporting high levels of persistence that are not borne out by studies of pharmaceutical claims.14–17 Our persistence findings were similar to those observed in a decade-old Australian study,8 suggesting that little has changed in Australia to improve treatment persistence during the past decade. The previous study found that 39% of people remained on treatment at 12 months from initiation compared with 37% in the current analysis. Though the authors used a 6-month lookback period to define treatment initiation (compared with our use of 12 months to define initiation), the previous study used the same data source as our study and our results are a highly comparable. Our findings are also in line with those reported from a population-based study from Taiwan, where 24% of people persisted with treatment to 2 years, and the 2-year persistence rate increased with age and was higher for people receiving PAs.16

To account for the fact that some people may use IOP-lowering medicines short-term—such as those recovering from cataract surgery—we stratified our persistence analyses by the number of repeat prescriptions at initiation. A typical dispensing equates to a month’s supply of medicine, and most people were dispensed medicines with either zero repeat prescriptions (one total prescription) or five repeats (six total prescriptions). Persistence was notably higher in those prescribed 4–6 repeats at initiation. While less than half of these people were on treatment at 1 year from initiation, 25% were still on treatment at 52 months or longer (per our 75th percentile estimate of treatment duration), highlighting that there is a subgroup of people who do persist with their initiated treatment.

The patient organisation, Glaucoma Australia, launched multiple educational campaigns aimed at improving treatment persistence during the study period.18 19 Skalicky et al note that these programmes may have improved patients’ knowledge about their treatment and reduced anxieties, but they did not impact medicine adherence.20 FDC treatments are also seen as a strategy for improving medicine adherence as they reduce the number of medicines a person must remember to take.2 We found that persistence with FDCs was low and similar to that with beta blockers or other, non-FDC medicine combinations. Interestingly, Hwang et al found that 2-year persistence was higher for people not taking FDCs and for those taking three or more medicines.16 A recent, small-sample pilot study found that the biggest challenges to persistence with treatment were patient difficulty in administering medicines, patient memory and a diagnosis of depression.7 The situation is further complicated by the ‘white-coat adherence’ phenomenon, whereby people begin using glaucoma medicines more regularly in the days leading up to a visit with their physician—causing their IOP to appear to be under control—only to reduce adherence again following the visit.17 More research is needed to design effective interventions to improve treatment persistence and adherence.

Just as persistence has remained constant over the past decade in Australia, we observed steady annual prevalence and incidence for glaucoma medicine treatment of around 180/10 000 and 36/10 000 between 2013 and 2019. These figures are similar to those reported from international studies.21 22 While prevalence and incidence have remained constant in Australia over the study period, the absolute size of the population entering the age groups at highest risk of developing glaucoma (65+ years) has grown dramatically and, as with many other conditions, treatment for glaucoma is likely to demand more resources in the coming decade. Non-medical therapies are being increasingly used to treat glaucoma, particularly laser trabeculoplasty.2 Australian Medicare statistics show noticeable increases in several of these procedures from 2017 to 2018 (online supplemental figure B). These procedures have the potential to impact the use of glaucoma medicines.

Conclusions

The prevalence and incidence of glaucoma treatment have not changed in Australia over the past decade, and real-world persistence with treatment remains poor. As a result, this form of treatment in real-world practice may be less effective than clinical trials have reported. The preventable disease progression implied by our findings represent a potentially important public health problem for Australia and similar countries. FDCs have not improved the situation to date and targeted interventions are required to improve treatment persistence. Population-based linkage studies may be helpful to elucidate the key characteristics responsible for prolonged persistence to medical therapy.