Eye strain is a common issue, often experienced after long periods of reading or staring at digital screens. This condition, also known as asthenopia, causes temporary discomfort and fatigue due to the overuse of the eye’s focusing muscles. In contrast, high eye pressure, medically termed ocular hypertension, is a measurement of the fluid pressure inside the eyeball. A normal pressure range is typically between 10 and 21 millimeters of mercury (mmHg). Many people who experience the headache and discomfort of eye strain worry that this feeling might be causing the dangerous condition of high eye pressure.
Is Eye Strain Linked to High Eye Pressure
Eye strain does not cause high eye pressure, despite the common concern that links the two conditions. The pressure felt during eye strain is muscular tension, not a build-up of fluid pressure within the eye itself. This misconception often arises because both conditions can cause similar symptoms, such as headaches or a feeling of pressure behind the eyes.
The discomfort from strain is acute and temporary, resolving with rest, whereas true high intraocular pressure (IOP) is a chronic, physiological measurement. High IOP is a sustained elevation of fluid pressure inside the eye that requires professional measurement. Ocular hypertension is a medical condition where the IOP is consistently above the normal range, exceeding 21 mmHg.
While some activities associated with eye strain, like prolonged screen time, might be indirectly linked to minor, temporary fluctuations in eye pressure, they are not recognized as a direct cause of chronic ocular hypertension.
How Eye Strain Differs From High Eye Pressure
Eye strain is fundamentally an issue of muscle fatigue, affecting both the ciliary muscle, which controls the lens’s focusing power, and the external muscles that move the eye. When you focus intensely on a near object, these muscles must continuously contract, leading to fatigue, pain, and sometimes blurred vision or dry eyes. Prolonged visual tasks, such as reading or using a computer, reduce the natural blink rate.
High eye pressure, however, is a problem of fluid dynamics, specifically the balance between the production and drainage of the aqueous humor. This clear fluid nourishes the front part of the eye and maintains its shape. Unlike eye strain, which produces noticeable symptoms like discomfort and headaches, high IOP is asymptomatic. Therefore, it can only be detected through a specialized eye examination, which is why it is often called the “silent thief of sight” when it leads to glaucoma.
Primary Causes of Elevated Intraocular Pressure
Elevated intraocular pressure is an imbalance in the eye’s fluid management system. The eye constantly produces a fluid called aqueous humor, which flows through the pupil and drains out through the trabecular meshwork. Pressure increases when the fluid is produced too quickly or, more commonly, when the trabecular meshwork is blocked or drains the fluid too slowly.
Several non-strain related factors can contribute to this problem, including genetic predisposition and advancing age. Certain medications are also known to elevate IOP, particularly the prolonged use of corticosteroid eye drops or oral steroids. Other underlying health conditions, such as diabetes and hypertension, increase the risk of developing ocular hypertension. High IOP can damage the optic nerve, leading to glaucoma and irreversible vision loss.
Practical Ways to Relieve Eye Strain
Since eye strain is caused by muscle overuse and dry eyes, relief centers on giving the eyes frequent breaks and improving lubrication. The most widely recommended technique is the 20-20-20 rule, which involves looking at an object 20 feet away for 20 seconds every 20 minutes of screen time. This simple action allows the ciliary muscle to relax its focus and also prompts an increase in the blink rate.
Adjusting the workspace setup can also reduce visual fatigue. Position the computer screen approximately an arm’s length away and slightly below eye level. Using artificial tears can help combat the dryness that results from a decreased blink rate during intense focus. Finally, ensuring that the room lighting is appropriate and that reflections or glare are minimized on screens.