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Defects in the eye happen due to many reasons. Due to growing age, the vision also decreases, and when the focal length alters, the vision also alters. We know that cataract is a common defect seen in the eye. Cataracts cause partial or sometimes complete vision loss when not treated properly. When the crystalline lens at old age becomes milky and cloudy, it is known as a cataract. When a person undergoes cataract surgery, the vision can be restored.
When the eye loses its ability to adjust its focal length, problems appear like a person cannot see the image correctly (blurring of vision), unable to view nearby objects or far away objects. When the defect in the refractive index occurs, the person cannot see the objects comfortably and distinctly. If not taken timely care of, the eyes might completely lose the power of accommodation. In this article, let us learn about various vision defects and their correction.
Correction : This condition can be corrected by using proper eyeglasses or contact lenses. Minor surgery also helps in restoring the vision with better clarity. Advancement in technology has made it easy to correct the refractive defects with contact lenses or through surgical interventions.
CBSE Class 10 Science Notes Chapter 11 Human Eye and Colourful World Pdf free download is part of Class 10 Science Notes for Quick Revision. Here we have given NCERT Class 10 Science Notes Chapter 11 Human Eye and Colourful World.
Defects of Vision and their CorrectionMyopia (Short-sightedness): It is a kind of defect in the human eye due to which a person can see near objects clearly but he cannot see the distant objects clearly. Myopia is due to(i) excessive curvature of the cornea.(ii) elongation of eyeball.
Correction: Since a concave lens has an ability to diverge incoming rays, it is used to correct this defect of vision. The image is allowed to format the retina by using a concave lens of suitable power as shown in the given figure.
Hypermetropia (Long-sightedness): It is a kind of defect in the human eye due to which, a person can see distant objects properly but cannot see the nearby objects clearly. It happens due to(i) decrease in the power of eye lens i.e., increase in focal length of eye lens.(ii) shortening of eyeball.
A hypermetropic eye has its least distance of distinct vision greater than 25 cm.Correction: Since a convex lens has the ability to converge incoming rays, it can be used to correct this defect of vision, as you already have seen in the animation. The ray diagram for the corrective measure for a hypermetropic eye is shown in the given figure.
Presbyopia: It is a kind of defect in human eye which occurs due to ageing. It happens due to the following reasons(i) decrease in flexibility of eye lens.(ii) gradual weakening of ciliary muscles.In this, a person may suffer from both myopia and hypermetropia.
27. Least cfistance of distinct vision: The minimum distance upto which an eye can see clearly is called the legist distance of distinct vision ; it is normally denoted by D. The least distance of distinct vision is equal to the distance between the eye and its near point. For a normal human eye, this distance is around 25 cm.
In this defect, an opaque, white membrane is developed on cornea due to which a person losses power of vision partially or completely. This defect can be removed by removing this membrane through surgery. In other words, a cataract is a clouding of the lens which prevents a sharp, clear image being produced. A cataract is arise because the lens is sealed in a capsule and as old cells die, they get trapped in the capsule, with time. This causes a clouding over the lens. This clouding cause results in blurred images.
Visual inspection is one of the oldest and most basic inspection methods that aid in securing quality assurance. It is done by looking over a piece of equipment and using raw human senses such as vision, hearing, touch, and smell to detect flaws.
Tumours and other compressive lesions could often present with visual impairment and/or visual field defects. Careful clinical assessment could aid in accurate diagnosis of the cause of the visual field defect and loss of vision. Compressive lesions of the visual pathway, especially lesions affecting optic nerve require a multi-disciplinary approach involving neurosurgeon, physician as well as the ophthalmologist. Treatment is given according to the cause.
Computer vision works much the same as human vision, except humans have a head start. Human sight has the advantage of lifetimes of context to train how to tell objects apart, how far away they are, whether they are moving and whether there is something wrong in an image.
Computer vision trains machines to perform these functions, but it has to do it in much less time with cameras, data and algorithms rather than retinas, optic nerves and a visual cortex. Because a system trained to inspect products or watch a production asset can analyze thousands of products or processes a minute, noticing imperceptible defects or issues, it can quickly surpass human capabilities.
Computer vision needs lots of data. It runs analyses of data over and over until it discerns distinctions and ultimately recognize images. For example, to train a computer to recognize automobile tires, it needs to be fed vast quantities of tire images and tire-related items to learn the differences and recognize a tire, especially one with no defects.
At about the same time, the first computer image scanning technology was developed, enabling computers to digitize and acquire images. Another milestone was reached in 1963 when computers were able to transform two-dimensional images into three-dimensional forms. In the 1960s, AI emerged as an academic field of study, and it also marked the beginning of the AI quest to solve the human vision problem.
5. The defect of vision in which the person is able to see distant object distinctly but cannot see nearby objects clearly is called(a) Long-sightedness(b) Far-sightedness(c) Hypermetropia(d) All above
33. The defect of vision in which a person cannot see the distant objects clearly but can see nearby objects clearly is called(a) myopia(b) hypermetropia(c) presbyopia(d) bifocal eye
This is an OMRON-developed image processing technology that can process color images without color conversion. Conventional color vision sensors convert the color into a filtered grey scale image for processing. Real Color Sensing processes 16.77 million real color information (256 tones for each of RGB). This enables more precise inspection, which is closer to the human eye.
Question 1.List four common refraction defects of vision. Suggest the way of correcting these defects. (CBSE 2014)Answer:Defects of vision:(i) Cataract: Crystalline lens of people at old age becomes milky and cloudy. This condition is called cataract.It is possible to restore vision through cataract surgery.
Mutation of the tyrosinase gene (TYR) causes oculocutaneous albinism, type 1 (OCA1), a condition characterized by reduced skin and eye melanin pigmentation and by vision loss. The retinal pigment epithelium influences postnatal visual development. Therefore, increasing ocular pigmentation in patients with OCA1 might enhance visual function. There are 2 forms of OCA1, OCA-1A and OCA-1B. Individuals with the former lack functional tyrosinase and therefore lack melanin, while individuals with the latter produce some melanin. We hypothesized that increasing plasma tyrosine concentrations using nitisinone, an FDA-approved inhibitor of tyrosine degradation, could stabilize tyrosinase and improve pigmentation in individuals with OCA1. Here, we tested this hypothesis in mice homozygous for either the Tyrc-2J null allele or the Tyrc-h allele, which model OCA-1A and OCA-1B, respectively. Only nitisinone-treated Tyrc-h/c-h mice manifested increased pigmentation in their fur and irides and had more pigmented melanosomes. High levels of tyrosine improved the stability and enzymatic function of the Tyrc-h protein and also increased overall melanin levels in melanocytes from a human with OCA-1B. These results suggest that the use of nitisinone in OCA-1B patients could improve their pigmentation and potentially ameliorate vision loss.
Following the featured articles in volume 18 was a section labeled "Comments," in which critics of children's literature with expertise in psychoanalysis offered several friendly but serious criticisms of the enterprise undertaken in the articles. These critics saw psychoanalytic interpretation of children's literature as often derivative, uncritical, and lagging in its use of psychoanalytic sources (Steig, Hogan, and Zipes), and as therefore perpetuating many of the faults of classical psychoanalytic practice, especially its divorce from a living context and its domineering stance toward its analysand (Knoepflmacher, Steig). Furthermore, it had not yet fully grasped its natural potential for exposing adult defects from the point of view of childhood interests (Phillips and Wojcik-Andrews). It also lacked a philosophical articulation of its own analytic project (Hogan, Knoepflmacher, Phillips and Wojcik-Andrews). Finally, by "denying the historical significance of the author's psychology and fantasizing" (Zipes 141), it missed its own deepest implications for the study of literary composition, creativity, and fantasy (Zipes, Knoepflmacher). My shorthand names for these criticisms: scholarly weakness, universalizing, normalizing adult defects, lacking philosophical vision, and missing the main chance. [End Page 267] 2b1af7f3a8