Understanding Vision Defects: Clear Distant Vision but Blurred Near Vision

The question asks about a vision defect where a person can see distant objects clearly but has difficulty seeing nearby objects distinctly. This is a common type of refractive error.

Analyzing the Symptoms

The key symptom described is good vision for far-away things and poor vision for close-up things. Let's look at the given options to identify which vision defect matches this description.

Exploring the Options

Let's examine each option provided:

• Hypermetropia: This condition, also known as farsightedness, occurs when light entering the eye is focused behind the retina instead of directly on it. This causes distant objects to be seen clearly, while nearby objects appear blurred. This aligns perfectly with the symptoms described in the question.
• Myopia: This condition, also known as nearsightedness, is the opposite of hypermetropia. It occurs when light is focused in front of the retina. People with myopia can see nearby objects clearly, but distant objects appear blurred.
• Presbyopia: This is an age-related condition where the eye's natural lens loses flexibility, making it difficult to focus on close-up objects. While it results in difficulty seeing nearby objects, the primary cause is different from hypermetropia and it typically affects people as they age. However, the symptom of blurred near vision is present.
• Hypopetropia: This is not a standard recognized term for a human vision defect.

Connecting Symptoms to the Correct Defect

Based on the analysis of the options, the defect characterized by clear distant vision and blurred nearby vision is specifically hypermetropia.

In hypermetropia, the eyeball might be too short, or the cornea/lens might not be curved enough, leading to the light rays converging behind the retina. To correct hypermetropia, convex lenses are used. Convex lenses converge light rays more strongly before they enter the eye, helping the image focus correctly on the retina.

Correction for Hypermetropia

Hypermetropia is typically corrected using spectacle lenses or contact lenses that are convex (converging) in nature. These lenses help to increase the refractive power of the eye, ensuring that the light converges on the retina.

Revision Table: Key Vision Defects

Additional Information on Eye Vision and Refraction

The human eye works by refracting (bending) light rays to focus them on the retina, a light-sensitive layer at the back of the eye. The cornea and the lens are the main parts responsible for this refraction. The ciliary muscles adjust the shape of the lens (accommodation) to focus on objects at different distances.

Refractive errors like hypermetropia, myopia, and astigmatism occur when the eye cannot focus light precisely on the retina. These errors can often be corrected using external lenses (glasses or contact lenses) or through refractive surgery.

• Refraction: The bending of light as it passes through different mediums, like from air into the cornea and lens of the eye.
• Retina: The layer at the back of the eye containing photoreceptor cells (rods and cones) that convert light into electrical signals sent to the brain.
• Accommodation: The process by which the eye's lens changes shape to focus on objects at varying distances. This ability decreases with age, contributing to presbyopia.

Understanding these basic concepts helps in grasping how vision defects like hypermetropia affect focusing and how corrective lenses work to restore clear vision.