MIRROR -The simplest and the most common optical instrument. -Uses the Law of Reflection to redirect light it receives. -It reflects most of the light in one direction. -Good reflecting mirrors can have 85% reflectance. Types of Mirror 1. Plane Mirror A mirror with a flat surface. Image formed: Laterally inverted Upright and always the same size as the object they reflect. Virtual image (images appear to behind the mirror) at the same distance as the object in front of the mirror. Examples:
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design of a rigid gas permeable lens‚ worn overnight to reshape the cornea curvature temporarily for the correction of Myopia and Astigmatism. These cornea refractive therapy would be indicated to people with low to mild myopia‚ (-4 diopters or less). The flatter central zone which is closer to the cornea exerts gentle pressure while the periphery surrounding the central visual zone is steeper than the cornea‚ allowing room for the cornea to mould and change its shape. With a steeper peripheral curvature
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facial nerve. The delicate‚ transparent mucous membrane that covers the inside of the eyelids and the anterior surface of the eye is the conjunctiva. The sclera is the white‚ tough‚ fibrous connective tissue that makes up the whites of the eyes. The cornea is the window of the eye and helps to focus entering light rays. The iris is the colored portion of the eye. The muscles of the iris involuntarily increase or decrease the diameter of the pupil. The pupil is the dark‚ round central opening that allows
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Question 1 - Definitions Visual Acuity Visual acuity is a test used to determine the smallest letters a person can read on a standardized chart (Snellen chart) or a card held 14 – 20 feet away. This test may be done in a health care provider’s office‚ a school‚ a workplace‚ or elsewhere. Visual acuity is expressed as a fraction. • The top number refers to the distance you stand from the chart. This is usually 20 feet. • The bottom number indicates the distance at which a person with normal
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1- Conjunctiva- the conjunctiva’s structure is a fine transparent mucous membrane and its main function is to cover and protect the surface of the eye. It also lubricates the eye as it moves in the socket. 2- Cornea- the corneas structure is a transparent front window through which light enters the eyeball. It is made up of 3 main structures which are the epithelium‚ stroma and endothelium. Its function is that it performs much of the initial focusing of the image by
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Contact lens is made up of plastic material and is directly placed on the anterior surface of eye to correct vision deficiences. Contact lens is used as substitution of spectacles. Currently‚ contact lens is more preferable as it comes in variety. One can change their eye color and appearance using colored pigment lens. The present methods of manufacturing includes mainly – Spin casting and Mold casting. But this has disadvantage of generation of ripple marks on the posterior surface and also distorted
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includes the cornea The choroid‚ which provides oxygen and nourishment to the eye and includes the pupil‚ iris‚ and lens The retina‚ which allows us to piece images together and includes cones and rods. The Process of Sight The easiest way to understand the component pieces of the eye and how they contribute to human sight is to follow the normal processing of an image. All vision is based on the perception of electromagnetic rays. These rays‚ in the form of light‚ must pass through the cornea‚ which focuses
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intestines‚ lungs‚ skin‚ bone‚ bone marrow‚ and cornea (the front part of the eye). [source: medlineplus.com] 2.Organ donations usually occur for patients with kidney failure‚ heart disease‚ lung disease‚ and cirrhosis of the liver. For patients who need a kidney or a liver‚ a living donor’s organs can be utilized‚ since we are already born with an extra kidney and the liver is regenerative. However‚ if the patient needs a heart‚ lung‚ pancreas or cornea‚ the organ needs to come from a deceased donor
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The process was carried out as a screw at eight different speeds ranged from the 5 to 500 mm/min hit the cornea‚ which is located in the apex of the eye globe‚ thereafter‚ the amount of load as well as the displacement on that were recorded via a 50 kgf load cell and an extensometer‚ respectively. The results showed that by increasing the rate of load on the
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Degeneration is a rare corneal ectatic disorder(PMC). This bilateral‚ non-hereditary ‚ idiopathic disorder is characterized by irregular astigmatism(Collagen cross-linking in the treatment of pellucid marginal degeneration)and thinning of the peripheral cornea in absence of inflammation‚ often affecting the inferior quadrant in a crescentic fashion. The disorder includes an area of corneal protrusion above the point of maximal thinning. This is the hallmark of the disorder and is what distinguishes it from
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