Near vision

Near vision is the ability of the eye to focus on objects that are close, typically within arm's reach. This ability is crucial for tasks such as reading, writing, and computer work. Near vision is controlled by a process called accommodation, which involves the ciliary muscle changing the shape of the lens to focus light onto the retina.

Physiology

The process of accommodation begins when the ciliary muscle contracts, causing the lens to become more curved. This increases the lens's refractive index, allowing it to focus light from close objects onto the retina. The ability to accommodate decreases with age, a condition known as presbyopia.

Assessment

Near vision is typically assessed using a Jaeger chart or a Snellen chart. These charts contain rows of letters or numbers of decreasing size, which the patient is asked to read from a set distance. The smallest row that the patient can read accurately determines their near visual acuity.

Disorders

Several disorders can affect near vision, including:

• Myopia: Also known as nearsightedness, this is a condition where the eye can see close objects clearly, but distant objects appear blurry.
• Hyperopia: Also known as farsightedness, this is a condition where the eye can see distant objects clearly, but close objects appear blurry.
• Astigmatism: This is a condition where the eye does not focus light evenly onto the retina, causing blurred or distorted vision.
• Presbyopia: This is a condition that affects most people over age 40, where the eye's lens hardens and can no longer change shape easily, making it difficult to focus on close objects.

Treatment

Treatment for disorders of near vision typically involves corrective lenses, such as glasses or contact lenses. In some cases, refractive surgery such as LASIK or PRK may be an option.

Near vision Resources
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