Factors That Cause Increased Intraocular Pressure
Multiple systemic, ocular, and lifestyle factors can elevate intraocular pressure, with the most clinically significant being systemic arterial hypertension (which increases aqueous production through enhanced ciliary body perfusion), topical corticosteroid use, diabetes mellitus, higher body mass index, and certain body positions—particularly prone positioning.
Systemic Factors
Cardiovascular and Metabolic Conditions
Systemic arterial hypertension is strongly associated with elevated IOP through increased perfusion of the ciliary body, resulting in increased aqueous production 1. After adjustment for confounding factors, patients with hypertension have a 17% increased risk of developing elevated IOP, and this risk increases to 48% when combined with diabetes 1.
Diabetes mellitus is independently associated with elevated IOP 1, 2, 3. The mechanism may involve changes in corneal biomechanics and alterations in aqueous humor dynamics.
Higher body mass index (BMI) correlates with elevated IOP across multiple population studies 4, 2, 3. Each increase in BMI is associated with measurable IOP elevation, and this relationship persists longitudinally over time 4.
Metabolic syndrome shows a dose-response relationship with IOP—each additional component of metabolic syndrome increases mean IOP by 0.33 mmHg 5. Related features including hepatic steatosis, increased left ventricular mass, and proteinuria are also strongly associated with higher IOP 5.
Other Systemic Associations
Hypothyroidism may increase IOP through alterations in mucopolysaccharides in the trabecular meshwork and decreased cellular metabolism 1.
Alcohol consumption is associated with higher IOP and increased prevalence of ocular hypertension (IOP >21 mmHg), though absolute effect sizes are small 6.
Ocular Factors
Anatomical Characteristics
Thicker central corneal thickness is one of the strongest predictors of higher measured IOP 2, 3. This represents both a true biomechanical effect and a measurement artifact.
Steeper corneal curvature correlates with higher IOP measurements 3.
Longer axial length (axial myopia) is associated with elevated IOP 3, though the relationship is complex due to altered scleral biomechanics.
Darker iris color shows positive correlation with elevated IOP 2.
Nuclear sclerosis (lens changes) is associated with higher IOP 2.
Iatrogenic Causes
Topical corticosteroids can cause significant IOP elevation, particularly in susceptible individuals. This is especially important after keratorefractive surgery where aggressive corticosteroid use may lead to undetected pressure elevation 1.
Surgical procedures: During LASIK, SMILE, and femtosecond laser-assisted cataract surgery, IOP briefly increases upon application of the suction ring and vacuum 1. Post-phacoemulsification IOP spikes are common in the first 24 hours 7.
Positional and Lifestyle Factors
Body Position Effects
Prone position causes the most dramatic IOP increase—approximately 3.22 mmHg higher than sitting and 2.24 mmHg higher than supine 8. This is clinically significant for patients who sleep face-down.
Supine position increases IOP by approximately 1.30 mmHg compared to sitting 8.
Standing position initially shows minimal change, but IOP increases significantly (0.53 mmHg) after standing for 5 minutes 8. This suggests dynamic vascular effects on aqueous production.
Temporal Variations
IOP fluctuates with circadian rhythm, with maximal daily IOP often occurring outside office hours 9, 10. This is critical because isolated office measurements may miss peak pressures that contribute to glaucomatous damage.
Age-related changes show a non-linear pattern—IOP increases with aging, with greater changes in younger subjects and women 4.
Clinical Implications and Pitfalls
Key Considerations
Multiple factors often coexist: Patients with hypertension, diabetes, and elevated BMI have cumulative IOP elevation risk 1, 5.
Measurement timing matters: Single office measurements miss circadian peaks and positional variations 9, 10, 8.
Corneal properties confound measurements: Thicker corneas lead to artificially elevated readings, while post-refractive surgery corneas may underestimate true IOP 1, 3.
Medication effects: Always consider corticosteroid-induced IOP elevation, particularly in post-surgical patients where inflammation may mask the pressure rise 1.
Risk Factor Recognition
Clinicians should identify high-risk subgroups:
- Patients with metabolic syndrome components
- Those on systemic antihypertensives (who may have low perfusion pressure despite elevated IOP)
- Post-surgical patients on corticosteroids
- Individuals with prone sleeping habits
- Patients with myopic progression 4
The relationship between systemic hypertension and glaucoma remains controversial because treatment with antihypertensives may cause systemic hypotension, reducing optic nerve perfusion despite controlling IOP 1. This creates a complex clinical scenario requiring individualized blood pressure management.