Friday, August 18, 2006

How Amazing Technology Is Used To Literally Map Out Your Cornea

A remarkable innovative technique called "corneal topography" can generate a computer printout that shows the curvature and the "hills and valleys" of your cornea. By studying these brightly color-coded contour maps, your physician can diagnose corneal shape abnormalities and monitor changes in the front surface of your eye. A thorough understanding of the various elevations of your eye's bubble-like window can help your doctor decide whether you are a candidate for refractive surgery. If you decide to have LASIK, a specialist can literally take "before and after" pictures that show surgically-induced changes in your corneal topography. Used in evaluating your results, these maps show the pre and post-surgical dioptric (refractive) power of your cornea. Rare complications usually can be easily pinpointed. For a nearsighted person, such elevation "photos" should show the flattening effect of the operation on the cornea.

To create topography maps of your cornea, high resolution video cameras that are attached to a specially programmed computer photograph your eye's front surface and profile. Each half-diopter change in elevation, which has a different light-focusing power, is represented by a different shade of color. The steeper curvatures, or "hills," are colored in warm shades of reds, oranges, and yellows while the flatter "valleys" are cool shades of light and dark blue. The middle areas are green. In other words, the steepest elevations with greatest refractive power are bright red and the lowest elevations with the least dioptric power are dark blue.

Kept in your chart, these elevation maps graphically illustrate the different refractive power of many points on your cornea and most irregularities in its surface. Corneal topography helps your doctor see how the pattern of your astigmatism looks on paper. As you now know, this refractive error is often caused by unevenness in the curvature of the cornea's surface. Topographic maps may also enable your physician to rule out subclinical keratoconus (a cone-shaped steepening and thinning of the cornea that causes irregular astigmatism). In addition, he can diagnose subtle conditions with corneal topography that might be missed with less sophisticated tests.

Your eye doctor will compare the astigmatism shown on your corneal maps to the total refractive astigmatism that your glasses correct. These measurements don't always agree. Some astigmatism is caused by irregularities within the eye. Laser surgery corrects only corneal astigmatism. Hence, corneal topography helps your doctor predict how much of your astigmatism can be successfully treated with the laser.

Corneal maps also can help your doctor find the best contact lens fit for you. A computer generated image of your cornea can quickly "try on" many different types of contact lenses from the computer's large database of soft, soft toric (for astigmatism), and rigid gas permeable lenses without placing a single lens in your eye.

posted by Trey Koehler @ 11:30 AM   0 comments  

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