Findings from a study published in Ophthalmology evaluated the relationship between systemic arterial blood pressure (BP) and the rate of change in standard automated perimetry (SAP) in eyes with glaucoma and glaucoma suspects.
Give me some background.
While intraocular pressure (IOP) is generally the most important modifiable trait in glaucoma development and progression, normal-tension glaucoma (NTG) highlights how IOP can remain in a normal range while the disease continues to progress.
The existence of NTG indicates that mechanisms independent of IOP can also impact the optic nerve, such as reduced optic nerve perfusion due to impaired blood flow autoregulation—which may worsen due to systemic arterial hypotension.
Talk about the study.
In this prospective cohort study, investigators included 124 eyes (91 glaucoma, 33 suspects) of 64 participants (mean age 68.4±7.6 years) that were followed at the Bascom Palmer Eye Institute, Palm Beach Gardens, Florida.
A 24-hour ambulatory blood pressure monitoring (ABPM) was acquired at the baseline visit.
Then: Participants underwent ophthalmic examination, BP measurement, and SAP at 4-month intervals.
The research team utilized linear mixed models to investigate the effect of BP on the rates of SAP mean deviation (MD) change over time; these analyses were adjusted for:
- Inclusion of both eyes
- Age
- Gender
- Race
- IOP
- Baseline severity
- Central corneal thickness
What were the main outcome measures?
The effect of baseline 24-hour and follow-up mean arterial pressure (MAP), systolic blood pressure (SBP), and diastolic blood pressure (DBP) on change in SAP MD.
Findings?
Overall, the included eyes had an average of 8.9±1.5 SAP exams over 28.3±6.0 months of follow-up.
The median rate of SAP MD change was 0.14 dB/year (range -1.21-0.96 dB/year), with 9 eyes (7%) presenting with moderate to fast progression (SAP MD changes ≤-0.50 dB/year).
Anything else?
Each 10 mmHg lower in 24-hour average MAP and SBP was associated with -0.171 dB/year and -0.137 dB/year faster rates of SAP MD loss (P=0.045 and P=0.023, respectively).
Lower mean SBP during follow-up was significantly associated with MD progression (P=0.003).
Expert opinion?
The study authors speculated that “glaucomatous eyes with progression at low IOP levels may have a non-IOP dependent mechanism of disease progression and thus would benefit from 24-hour ABPM to determine if they have vascular risk factors for progression, such as low MAP or SBP.”
Further: Patients with a history of low SBP—or patients wherein an office-based BP reading indicates low BP—may benefit from such testing, given the risk for future fast progression.
Take home.
Lower baseline 24-hour ABPM measurements and low SBP during follow-up were significantly associated with rates of glaucomatous SAP progression.
Next steps?
With further research to validate the findings, these figures could potentially be used as predictors of the risk of glaucomatous progression.
For example: Theoretically, a patient with or at high risk for visual field progression could be identified with 24-hour BP monitoring with systemic hypotension while using systemic arterial hypertension medication.