About Prescription Eyeglasses

The correct prescription eyeglasses can improve quality of life in many ways. An optometrist or ophthalmologist will do a physical eye exam to check the health of the eyes, and then recommend a prescription.
Prescription eyewear design has come a long way in recent years so everyone is sure to find something suitable.

History

• The exact date the first pair of prescription eyeglasses was invented is not known. The earliest recorded evidence of prescription eyewear use is in the 13th century. However, it wasn't until the 15th century that glasses for distance were invented. These first glasses were very rudimentary. They had to be held in place by hand. In the 17th century, a London optician designed the first sidepieces for glasses that allowed for wear ability.

  Benjamin Franklin invented the first bifocals in 1784. These allowed for distance and close up vision correction.

  It wasn't until the 19th century that doctors found a way to examine the eyes and make set prescriptions. Before this, people just tried various pairs of glasses until finding the one that worked best.

Significance

• Prescription eyeglasses are used to improve the following vision impairments:

  Nearsightedness or Myopia: Nearsightedness occurs when you can see objects clearly close up, but they are blurry far away.

  Near focusing problems or Presbyopia: Presbyopia occurs gradually as the eye loses its ability to focus on nearby objects.

  Farsightedness or Hyperopia: Farsightedness occurs when you can see objects clearly in the distance, but they are blurry close up.

  Astigmatism: Astigmatism occurs when there is a curvature in either the cornea or lens of the eye.

Function

• Eyeglass lenses are cylindrical or spherical. A spherical surface is shaped like a ball with some roundness throughout. The lenses can curve either inward (concave) or outward (convex). Concave surfaces are always on the back of the lenses.

  A cylindrical lens is shaped like a football.

  The focusing ability of a pair of eyeglasses is determined by its thickness, index of refraction, and the difference in curvature between the front and back surfaces. The index of refraction is determined by how a given material the lens is made of bends light. A higher index of refraction means more light bend ability.

  Concave lenses help correct nearsightedness. Cylindrical lenses help correct astigmatism, and convex lenses are used to help correct farsightedness.

Identification

• Prescription eyeglass lenses are divided into four categories.

  Single vision lenses are often prescribed for people under forty. Single vision lenses have the same focal power throughout the lens. For this reason, they are used to treat all eye conditions.

  Bifocal lenses are made up of two parts. The top part of the lens helps with distance and the bottom with close up vision. Bifocals are now available with or without the line across the middle.

  Trifocal lenses have three fields of vision: The top for distance, middle for intermediate, and bottom for close up reading. Trifocals differ from bifocals in that they are fitted higher on the eye.

  Multifocal lenses include bifocal, trifocal, and progressive addition lenses. Progressive lenses are bifocals without lines. Their power increases from top to bottom with no clear dividing line between powers.

Considerations

• The price for prescription eyeglasses varies. Some factors that determine price include the index of refraction level, lens material, specialized lenses, and tinting.

  The manufacturer is another factor in the price of prescription eyeglasses. Designer eyewear costs more than generic. Always check with your insurance provider to see which glasses are covered under your plan. Some insurance plans only cover generic brands completely. If you purchase a designer name brand, you will have to pay the difference.