Eyes - Refractive Errors.ppt

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  • The ability to see is dependent on the actions of several structures in and around the eyeball.
  • When you look at an object, light rays are reflected from the object to the cornea, which is where the miracle begins.
  • The light rays are bent, refracted and focused by the cornea, lens, and vitreous.
  • The lens' job is to make sure the rays come to a sharp focus on the retina.


  • The resulting image on the retina
  • is upside-down.
  • Here at the retina, the light rays are converted to electrical impulses which are then transmitted through the optic nerve, to the brain, where the image is translated and perceived in an upright position!
  • Think of the eye as a camera.
  • A camera needs a lens and a film to produce an image.
  • In the same way, the eyeball needs a lens (cornea, crystalline lens, vitreous) to refract, or focus the light and a film (retina) on which to focus the rays.


  • If any one or more of these components is not functioning correctly, the result is a poor picture.
  • The retina represents the film in our camera.It captures the image and sends it to the brain to be developed.
  • The macula is the highly sensitive area of the retina.
  • The macula is responsible for our critical focusing vision.
  • It is the part of the retina most used.We use our macula to read or to stare intently at an object.


  • Theanterior chamberis the area bounded in front by the cornea and in back by the lens, and filled with aqueous.
  • Theaqueousis a clear, watery solution in the anterior and posterior chambers.
  • Thearteryis the vessel supplying blood to the eye.
  • Thecanal of Schlemmis the passageway for the aqueous fluid to leave the eye.
  • Thechoroid , which carries blood vessels, is the inner coat between the sclera and the retina.


  • Theciliary bodyis an unseen part of the iris, and these together with the ora serrata form the uveal tract.
  • Theconjunctivais a clear membrane covering the white of the eye (sclera).
  • Thecorneais a clear, transparent portion of the outer coat of the eyeball through which light passes to the lens.
  • Theirisgives our eyes color and it functions like the aperture on a camera, enlarging in dim light and contracting in bright light. The aperture itself is known as the pupil.
  • Thelenshelps to focus light on the retina.


  • Themaculais a small area in the retina that provides our most central, acute vision.
  • Theoptic nerveconducts visual impulses to the brain from the retina.
  • Theora serrataand the ciliary body form the uveal tract, an unseen part of the iris.
  • Theposterior chamberis the area behind the iris, but in front of the lens, that is filled with aqueous.
  • Thepupilis the opening, or aperture, of the iris.
  • Therectus medialisis one of the six muscles of the eye.


  • Theretinais the innermost coat of the back of the eye, formed of light-sensitive nerve endings that carry the visual impulse to the optic nerve. The retina may be compared to the film of a camera.
  • Thesclerais the white of the eye.
  • Theveinis the vessel that carries blood away from the eye.
  • Thevitreousis a transparent, colorless mass of soft, gelatinous material filling the eyeball behind the lens.


  • Refractive errors
  • Conjunctivitis
  • Cataract
  • Glaucoma
  • Corneal Ulcer
  • Injuries of the eye
  • Diabetic Retionopathy


  • Name of the disease & terminologies
  • Etiology
  • History, signs and symptoms
  • Physical examination
  • Investigation
  • Treatment according to allopathic medicine
  • Other therapies
  • Yoga practices
  • Books and journals for reference

13. REFRACTIVE ERRORS imperfections in the focusing power of the eye, for example, hyperopia, myopia, and astigmatism. Hyperopia(Long sightedness) Myopia(Short sightedness) Astigmatism 14.

  • Refractive errors are disorders, not diseases.
  • A refractive error means that the shape of the eye does not bend light correctly, resulting in a blurred image.
  • Light has to be refracted or bent by the cornea and the lens to the retina in order for us to see.
  • Normally, the rays of light entering the eye are brought to a precise focus on the retina, the light sensitive layer lining the back of the eye.
  • When such a focus is not achieved, a refractive error results and the vision is not clear.


  • When the light rays are focused in front of the retina, the resulting condition is termed Myopia (short-sightedness).
  • In Hyperopia (long-sightedness), the light rays come to a focus behind the retina.
  • Astigmatism (cylindrical error) occurs when incoming light rays are unable to reach a common focus within the eye.
  • Wavefronta measure of the total refractive errors of the eye, including nearsightedness, farsightedness, astigmatism, and other refractive errors that cannot be corrected with glasses or contacts.


  • Myopia (distant objects are blurry)
  • Hyperopia (close objects are blurry)
  • Presbyopia (aging of the lens in the eye)
  • Astigmatism (blurred vision at all distances)

Common refractive disorders are 17.

  • Long sighted patients have a blurred vision of close objects.
  • They suffer from eye strain and headache after doing close work.
  • Irritability and nervousness after prolonged concentration.


  • Children complain of their inability to see the blackboard.
  • Shortsighted people often have headaches or suffer from eyestrain.
  • They have blurry distant vision and tend to squint for a better image.


  • Patients with astigmatism have blurred or distorted vision at all distances.
  • It can also cause images to appear doubled, particularly at night.
  • Patients have inconsistent difficulty focusing on various objects such as finely printed words and lines.
  • Headache and fatigue are common as the person tends to strain their eyes.
  • Squinting, eye discomfort and
  • irritation are also frequent.


  • Tiny blind spots appear at the edges of the visual field (peripheral or side vision) that slowly get larger and spread
  • Blurred vision
  • Appearance of colored halos around lights
  • Adjustment problems on entering a dark room
  • Repeated difficulties that new eyeglass prescriptions do not help
  • Peripheral (side) vision is decreasing
  • Severe eye and head pain
  • Nausea or vomiting
  • Appearance of rainbow-colored halos around bright lights
  • Rapid loss of vision


  • Refractive disorders are commonly treated using corrective lenses, such as eyeglasses or contact lenses.
  • Refractive surgery can also be used to correct some refractive disorders.


  • Non surgical options for the correction of refractive errors include spectacles and contact lenses.
  • Spectacles contain lenses that suitably refract the incoming rays of light and enable them to focus on the retina.
  • Contact lenses perform the same function but are placed on the cornea-the clear front portion of the eye.
  • Hence, they provide better cosmesis and improved quality of vision in the higher refractory errors.

How are refractive errors corrected? 23.

  • Surgical procedures attempt to eliminate the external aids like glasses and contact lenses.
  • In Radial Keratotomy, where four to eight corneal incisions are made involving 95-99% of the corneal thickness, to flatten the central corneal.
  • The weakened peripheral cornea is pushed outwards by the pressure within the eye.
  • This results in a flattening of the central cornea which corrects a myopic refractive error.
  • Similar incisions when made in a hexagonal fashion in the mid-peripheral cornea result in a forward protrusion of the central cornea.


  • This procedure is termed Hexagonal Keratotomy and is used to treat hyperopia.
  • To correct astigmatism, straight or curved incisions are made in the mid peripheral cornea and the procedure is termed Astigmatic Keratotomy.
  • All incisional procedures weaken the s