A new study in the American Journal of Ophthalmology explored whether the use of oral nitrates in patients with chronic ischemic heart disease (IHD) had an effect on the development of ocular hypertension (OHT) and glaucoma.
Give me some background first.
The role of systemic drugs in glaucoma risk has been explored in clinical studies over the last few years.
Case in point: Research has shown that taking nitrates may produce a small decrease in IOP by reducing systemic systolic blood pressure through vasodilation.
Tell me more.
As evidenced by prior research, the mechanisms of protective effects of oral nitrates on glaucoma are multifactorial.
For example: Nitric oxide has a vasodilating effect, which improves perfusion of the eye and optic nerve.
Further, chronic use of nitrates has been shown to significantly dilate retinal veins, potentially suggesting increased perfusion of the retina and optic nerve and protecting against ischemic damage.
Interesting … now, talk about this study.
This was a retrospective clinical cohort study comparing patients who took oral nitrates with those who did not among a population of adult patients with chronic IHD.
Throughout the study’s duration: Patients were required to have at least one eye examination within 1 year, another within 1-3 years, and another within 3-5 years.
Talk about these participants.
The study population consisted of individuals who met the following criteria:
- Age ≥ 40
- Diagnosis of chronic IHD
- Received at least 4 refill prescriptions for oral nitrates (with a minimum treatment duration of 1 year)
- No prior diagnosis of glaucoma, glaucoma suspect, or ocular hypertension
Findings?
Open-angle glaucoma (OAG) risk was significantly lower in those who used nitrates at 3 years (p = 0.008) and 5 years (p < 0.01).
In addition, the risk of POAG was lower in those who used nitrates at 3 years (p < 0.01) and 5 years (p < 0.01)
Those who used nitrates were less likely to need treatment with first-line glaucoma therapy at 1, 3, and 5 years (p<0.01)
However: There was not a significant association between nitrate use and ocular hypertension.
Noted. Any limitations?
This study relied on electronic health records (EHRs), which may have erroneous or incomplete reporting of diagnoses and treatments.
Additionally, the results may not have extrapolated to the entire population of those taking oral nitrates, as the study participants were diagnosed with chronic IHD
In both study groups, there was high (74%) use of corticosteroids, a known risk factor for OAG
- And importantly: Residual confounding factors such as genetic predisposition and lifestyle may have contributed to patients’ glaucoma risk.
Expert opinion?
The study authors concluded that oral nitrates are not currently recommended for the treatment or prevention of glaucoma by any organization.
Anything else?
Looking beyond this study, the effect of dietary nitrates has previously been explored, with the Netherlands- and population-based, long-term Rotterdam study previously finding an association with a lower risk of glaucoma.
Relating this back to the study at hand: Nitrate intake from both vegetable and non-vegetable sources were associated with a lower risk of OAG.
Take home.
The results of this study suggest that oral nitrate use may have a protective effect against glaucoma development.
However, further research in the setting of randomized controlled trials (RCTs) are needed to establish this relationship and guide treatment recommendations for glaucoma.