What is Intraocular Pressure?
Intraocular pressure (IOP) is a measure of the pressure within the eye. Aqueous fluid is produced within the eye and should flow out through the trabecular meshwork. If there is a dysfunction, the IOP will increase resulting in damage to the optic nerve. Lowering intraocular pressure is currently the main therapeutic measure to treat and manage glaucoma. All types of glaucoma demonstrate optic-nerve damage (cupping, pallor, or both) associated with peripheral visual field defects.
- Intraocular pressure (IOP) is a measurement of aqueous production versus elimination from the eye.
- Measuring IOP is the main way to manage and treat Glaucoma
- Many internal and external factors affect IOP over time.
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Understanding Intraocular Pressure
Intraocular pressure (IOP), the pressure within the eyeball, is a function of the ciliary body’s aqueous production and elimination of aqueous humor through Schlemm’s canal. Normal IOP helps maintain the eyeball shape and allows the proper refraction of light in the anterior part of the eye. IOP is not a fixed measurement but changes over time with intrinsic circadian rhythm and can change in various lifestyle-related situations. Dietary habits and exercise can affect IOP.
Risk Factors for Intraocular Pressure
Studies report that percent body fat, systemic blood pressure, pulse rate, albumin, and HbA1c are correlated with high IOP while older age is correlated with low IOP.
Determining the target IOP in glaucoma patients is multi-faceted and requires attention to family history, glaucoma type, severity of disease, age, race, family history, corneal thickness, hysteresis, and initial IOP. Some patients will still have disease progression despite achieving target IOP.
Intraocular Pressure Symptoms
Patients are unlikely to experience any symptoms of high intraocular pressure if it’s elevated chronically. However, an acute rise in intraocular pressure, such as in angle closure glaucoma, will present with pain, redness, photophobia, decreased vision and headache.
What is Normal Intraocular Pressure?
Normal intraocular pressure ranges from 11-21 mmHg. Ocular hypertension usually applies to eyes with an IOP greater than the statistical upper limit of normal (21 mmHg). A thicker cornea leads to an overestimate of the IOP, while a thinner cornea may lead to underestimation of IOP. Large diurnal IOP fluctuation is an independent risk factor for glaucoma progression besides elevated IOP.
Diagnosing Intraocular Pressure
Intraocular pressure can be checked by your eye doctor. Tonometry can be performed using a variety of instruments including Goldman’s, iCARE, and tonopen.
Intraocular Pressure Treatment
Intraocular pressure is routinely checked by your eye doctor. If glaucoma or ocular hypertension is suspected, you may be asked to have your pressure checked every 3-6 months. If your glaucoma medications have been changed, your doctor will want to assess the effect the medication is having on your IOP and will check your pressure more often. In addition, if your doctor places you on a steroid eye drop for an ocular condition, they will have you return to have your IOP checked.