Blurred truth about glasses

1. Keloysius Mak Blurred truth about glasses

2. Non-Myopic Eye • Light converges on the retina, producing a clear and sharp image

3. Myopic Eye • Light converges before the retina, thus the image formed on the retina is blurred

4. Myopic Eye • If the cornea is too curved, or if the eyeball too broad, light rays from distant objects converge in front of the retina. This makes objects seem fuzzy or blurred. • Nearby objects don't look blurred because the light rays enter the eye at a slight angle. This means they focus on the retina properly.

5. What can be done? • Glasses • LASIK

6. Glasses • For nearsightedness, the glasses offer a concave lens that bends light rays outward, which normalizes the eyeball. • For farsightedness, the glasses use a convex lens that bends the light inward before it reaches the eye's lens, thereby correcting vision.

9. LASIK procedure • The patient receives topical anesthesia, and if desired a mild sedative - however, the patient is awake during the procedure. • Cleansing of the eyelid area, then paper taping the eyelashes to prevent infection. • A portable device called a speculum is positioned in the eye to prevent blinking. A suction ring is then placed on the eye, and a momentary blackness occurs. • An instrument called a microkeratome glides across the top layer of the cornea, making a thin incision - and creating a flap of tissue. • The physician lifts back this flap, then proceeds to position the laser and directs the laser energy. The patient will hear a series of pulses as the laser reshapes the cornea.

10. Why LASIK • Sophisticated technology has made LASIK a fast, virtually painless and very popular procedure. By 2001, over 2 million people world-wide had chosen LASIK for vision correction.

11. LASIK Dangers • NONE!

12. Advantages of rigid lenses • Gas-permeable rigid lenses have several advantages over soft lenses: • Visual acuity is better, especially in the persons with corneal astigmatism. • Allergic or toxic reactions to lens care solutions are less frequent. • Gas-permeable lenses last longer because they are more durable than soft lenses. • The cost of these lenses is usually less because of the longer lens life and lower cost of the material.

13. Why Rigid Lenses? • Correction of refractive errors such as myopia (nearsightedness) • Prescribed to patients who have suffered trauma to the cornea or who have corneal diseases such as keratoconus. 

14. Why Rigid Lenses are bad • Inability to transmit oxygen from the air to the cornea. • Risk of corneal swelling • Other complications

15. Electronic Bifocals • The new glasses could benefit people suffering from presbyopia, a condition in which faraway objects are in focus but those nearby appear blurry. • Spectacles that change prescriptions with the flick of a switch.

16. Future Glasses : TV Glasses •  Light-guide Optical Element (LOE) technology, which sends an image through a lens as thin as 3mm. The result is a personal display that looks like ordinary eyeglasses but provides the wearer with a virtual large-screen television.