Refractive Defects of Vision and their Correction

Vision Defects

• Another name for myopia is nearsightedness.
• In hypermetropia, the vision is affected as the light rays from a closeby object are focused at a point behind the retina.
• Myopia is corrected using a concave lens.
• The exact cause of myopia is not known, but it is thought to be related to a combination of genetic and environmental factors.
• Myopia, or nearsightedness, is a defect that can be corrected by using a concave lens.
• In myopia, the far point is closer than normal.
• Hypermetropia arises when the light rays from a closeby object are focused at a point behind the retina.
• Presbyopia arises due to the gradual weakening of the ciliary muscles and diminishing flexibility of the eye lens.
• In some individuals, bifocal lenses are required for correcting both myopia and hypermetropia.
• Hypermetropia is a defect that arises when the focal length of the eye lens is too long or the eyeball has become too small.
• In hypermetropia, the focal length of the eye lens is too long or the eyeball has become too small.
• A convex lens is used to provide additional focusing power required for forming the image on the retina in individuals with hypermetropia.
• Hypermetropia can be corrected by using a convex lens of appropriate power.
• In individuals requiring correction for both myopia and hypermetropia, bifocal lenses facilitate distant vision.
• Presbyopia arises when the near point of a person gradually recedes away due to the weakening of the power of accommodation with ageing.
• Hypermetropia arises because the eyeball has become too small or the focal length of the eye lens is too long.
• Bifocal lenses can be used to correct both myopia and hypermetropia in some individuals.

Photosynthesis

• Autotrophs fulfill their carbon and energy requirements through the process of photosynthesis.
• Heterotrophs directly or indirectly depend on autotrophs for their survival.
• Autotrophs are organisms that use simple food material obtained from inorganic sources like carbon dioxide and water.
• Enzymes are the bio-catalysts used by organisms to break down complex substances into simpler ones for energy and growth.
• Photosynthesis involves the conversion of substances from the outside into stored forms of energy in autotrophs.
• The primary purpose of storing carbohydrates in the form of starch in plants is to provide energy for growth and development.
• The initial step of photosynthesis involves the absorption of light energy by pigments such as chlorophyll.
• Chlorophyll, essential for photosynthesis, resides in chloroplasts in plant cells.
• Chlorophyll plays a crucial role in the process of photosynthesis by absorbing light energy.
• In C4 plants, the steps of photosynthesis do not occur immediately after each other.

Learn about the common refractive defects of vision such as myopia, hypermetropia, and presbyopia, and how they can be corrected using suitable spherical lenses. This quiz provides an overview of these vision issues and their remedies.