Found inside – Page 279This automatic adjustment in the curvature of the lens as it focuses on a nearby object is called accommodation ( FIGURE ... Because convergence occurs during all near - point work - reading , writing , sewing , knitting — it tends to strain the ... Found inside – Page 195In a bifocal eyeglass , the individual chooses either to look through the distance portion or the near portion depending on the location of the object to be viewed . Some recent contact lens and intraocular lens designs rely on a concept called ... Found inside – Page 356The lens , which consists of elastic fibers , thins or flattens to see a distant object , and it becomes rounder and wider to focus on an object ... The solution is simple : corrective lenses to do the work the lens of your eye can no longer do by itself . The text has been developed to meet the scope and sequence of most university physics courses and provides a foundation for a career in mathematics, science, or engineering. Found inside – Page 30device comes into action and by thickening the lens brings the light rays to focus on the retina . When viewing near objects a short eye has to increase the thickness of the lens still further to bring the light rays to focus on the retina . A short eye ... Found inside – Page 47We have seen that the required accommodation for a near object is greater behind a telescope , it is multiplied by the Figure 3 . ... lenses between the lenses , t , is 15 mm . instead of his conventional correction , thus If near objects are viewed through a ... The Galilean telescope occurs in many ophthalmological situations . This book considers the issues surrounding the occurrence, progression, and predictability of myopia (near-sightedness), with special emphasis on the 16- to 26-year-old population. Found inside – Page 54FIGURE 3.6 Detailed cross section of the front of the eye , showing changes in lens shape with accommodation . ... When the ciliary muscle relaxes , it also expands , pulling on the zonules and flattening the lens ( unaccommodated - for viewing distant objects ) . ... The actual transduction of light energy takes place in the retina , and we now turn our attention to this crucial component of the visual system . Found inside – Page 37When an object is close to the viewer , the eye muscles pull on the lens , flattening it out . Convergence is the ... as to the depth of the object . A viewer ' s two eyes converge when viewing near objects and diverge when viewing far objects . Found inside – Page 76The closest distance for which the lens can project a focussed image of the object is called the near point . For very young ... In a normal eye , the lens is flat when distant objects are viewed , and rounded when close - up objects are viewed . About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Found inside – Page 64Superior rectus muscle Sclera Choroid Conjunctiva Retina Iris Cornea Lens Anterior chamber Optic nerve Central artery of retina ... One in twenty cases of blindness now comes from such injuries . Abnormalities of the visual apparatus and common eye disorders In nearsightedness , or myopia , objects appear blurred unless they are held close to the eye . This is because the eyeball is usually too long in relation to the lens , and objects viewed at a distance come into a focal point in ... Found inside – Page 77If this occurs at the early stage of life that is during development , the visual connections from the poor eye to the brain will ... As the age continues to increase to adulthood , the lens used in viewing near objects or read small prints , looses its ... Found inside – Page 353This condition is referred to as myopia or short sight and can be corrected by placing a concave lens in front of the eye in order to balance its excess positive power. If the power of ... 17–3. pair with stronger convex lenses to see near objects. Found inside – Page 421tively too convergent , the images of distant objects will fall in front of the retina so that on the retina itself the image will be blurred . ... A third common type of defect in vision occurs when one or more of the refracting surfaces of the eye , such as the cornea or crystalline lens , are not perfectly spherical . ... What is the focal length of the lens needed to enable this person to see distant objects clearly ? Found inside – Page 277Observation shows that this is what actually happens : the corneal surface remains unchanged when a near object is looked at after a ... In the resting eye it is relaxed and the suspensory ligament of the lens is taut , and , pulling on its edge , drags it out laterally a little and ... To see a nearer object the ciliary muscle is contracted , and according to the degree of its contraction slackens the suspensory ... Found inside – Page 346When a swimmer is under clear water , why can ' t he see nearby objects clearly ? How do goggles help a swimmer to ... Find the focal length and the power of the lens which will bring the near point to 15 cm . Where would the near point for ... Found inside – Page 84Iris Macula Vitreous humour Pupil Lens Aqueous humour Cornea SEE ALSO WHAT THE BODY IS MADE OF p . ... Stopping down occurs automatically on exposure to bright light and on near viewing . ... This allows the lens to converge rays from a near object , these being more divergent than rays from a distant object . Found inside – Page 29Ametropia When this telescope is used by a myope , say , an uncorrected 5 D. myope , for viewing a distant object , two things happen : ( 1 ) to see the distant object clearly the lenses must be brought closer together , and ( 2 ) the magnification ... Found inside – Page 92Emmetropia occurs when the focal length of the dioptric media and the distance from the cornea to the retina are matched . While one ... Presbyopia is the inability of elderly patients to see close objects ; it is caused by hardening of the lens . Found inside – Page 19Cornea ( 2 ) - Sclera and Choriod ( 1 ) Aqueous Humor ( 6 ) - Vitreous Humor ( 6 ) – Retina ( 7 ) Pupil ( 4 ) Lens ( 5 ) Iris ( 3 ) Figure 1 . 7 The eye . ( Numbers in parentheses ... The reverse occurs for viewing near objects . The lens absorbs all ... Found inside – Page 9245a illustrates the two eyes observing a near object B through a pair of distance correcting lenses centred for distance . To observe B the eyes are called upon to converge into the directions CN and C , K , the left eye for example having ... Found inside – Page 100When the eye targets an object , the lens changes shape , altering the refractive power of the eye and allowing the object to come into focus . When viewing near objects , the lens has a round shape and when viewing distant objects , the lens ... Found inside – Page 376Accommodation for near vision necessitates three changes : increase in the curvature of the lens , constriction of the ... Single binocular vision ( seeing only one object instead of two when both eyes are used ) occurs when light rays from an ... Found inside – Page 461We see objects right side up because the brain interprets the images in this way. To see ... As you know, the farther away an object is from a convex lens, the closer to the lens the rays come to a focus. ... Then we can see distant objects clearly. Found inside – Page 578Such an eye cannot focus a distant object without a correcting lens , and can see only near objects distinctly . The vision is said to be near - sighted , and a diverging lens is needed to counteract the excessive refracting power of the eye , as ... Found inside – Page 1513Lenses are placed before the patient's eyes while reading from an eye chart . ... is a connection between the focusing of the lens of the eye ( accommodation ) and convergence of the eyes ( the two eyes turning in to point at a close object . ) ... Found inside – Page 34Emmetropia — Normal Refraction Distant objects can be seen when the normal eye is at rest (that is, not accommodating). ... Near objects can only be seen clearly if the eye is accommodating when the lens becomes fatter or more convex (see chapter 2). ... Light from a distant object comes to a focus in front of the retina. Found inside – Page 361This is what happens : The ciliary muscle contracts and in doing so draws the choroid forward . This permits the ciliary processes to move forward and inward , thus reducing the diameter of the ring which they form around the lens . ... Errors of Refraction To see nearby and distant objects clearly and distinctly , the light rays reflected from those objects must be focused directly upon the retina of the eye . Found inside – Page 184It results from the hordening of the lens, which decredses its dbility to focus on close objects. ... father, who need glasses for other reasons, often get glasses with bifocal lenses rather than carry around an extra pair of glasses just for reading. Found inside – Page 43Each of its eyes has some 30 , 000 lenses . This arrangement enables the insect - eating dragonfly to see distant objects in motion as well as nearer objects which are stationary . As an aid to efficient hunting , it can swivel its head almost 360 ... Found inside – Page 1035Refraction of light occurs at the corneal interface, aqueous humor, and crystalline lens. Light then is ... muscle contracts to increase the curvature of the lens for viewing of objects closer to the eye. The increased curvature of the lens increases its power, shortens the focal length, and focuses near objects on the retina. This is ... Found inside – Page 487For example , if the eyeball is constructed so that the distance between the lens and retina is too short , the light rays focus behind the retina . This causes difficulty in seeing objects close at hand and is called farsightedness ( hyperopia ) ( see Fig . 22-1 ) . If the opposite is ... and near vision . This hardening of the ciliary muscles occurs in many persons over 40 years of age and is known as presbyopia . Found inside – Page 3-5When objects near the eye are viewed , the distances between the various planes are reduced . ... Change in the shape of the crystalline lens to obtain accommodation is effected by means of an annular ciliary muscle which completely ... Found inside – Page 35Chapter V SEEING NEAR OR DISTANTACCOMMODATION THEN rays of light come from a source so distant , twenty or ... When the eyes are at rest , viewing distant objects , the lens is oval in shape , caused by the tension of muscle fibers ... Found inside – Page 3divergence of the rays coming from the near object to that of rays : from an object , GHD , ten inches off . ... Thus , supposing the lens enables us to see the object at one inch from the eye , it must appear ten times larger than it would at ten inches from it . ... The rays suffer aberration at both lenses ; but it so happens that those rays which were most refracted at the first lens fall more centrically on the ... Found inside – Page 171Astigmatism occurs often in conjunction with myopia or hyperopia . Caused by irregular curvature ... Patients with more than 2 diopters of astigmatism may not be able to achieve clear vision with soft contact lenses . Presbyopia affects ... They will then report eye ache or unclear vision when viewing near objects . Presbyopia ... Found inside – Page 28The lens can be such as to give no marginal astigmatism for a distant object. As an example, a minus ten sphere will ... Let Us suppose that the minus ten lens will be used for distant objects and also for reading. Then all three factors should be ... Found inside – Page 126Keep both eyes open and look at a distant object . Describe ... A convex lens in the eye refracts the light and makes it converge on the retina . Muscles attached to the lens adjust its shape so that you can see objects both near and far away . Found inside – Page 184required by a myope to see a near object . Due to the difference in accommodation the bespectacled hyperope would require less fusional convergence ( than with contact lenses ) and the bespectacled myope more fusional convergence . Found inside – Page 611emmetropic eye can , with its ciliary muscle completely relaxed , see all distant objects clearly , but to focus objects at close ... object comes nearer and nearer to his eye it finally portions of the lens in one plane are not bent comes near enough ... Found inside – Page 797... 797 The introduction of wide - aperture lenses to let in For camera shutters and other accessories , and for more light and reduce exposure times involves some history , see PHOTOGRAPHY . provision for bringing near objects into focus . Found inside – Page 340What happens is that the crystalline lens of the eye becomes less accommodating , to say the least . ... 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