Dr. Orwa Nasser MD MPH - Corneal Topography/Tomography

Corneal Topography/Tomography

Corneal topography is a special photography technique that maps the surface of the cornea. It works much like a 3D (three-dimensional) map of the world, that helps identify features like mountains and valleys. But with a topography scan, a doctor can find distortions in the curvature of the cornea, which is normally smooth. It also helps doctors monitor eye disease and plan for surgery.

Corneal Tomography is another special photography technique that maps the cornea but is is more advanced than the topography by its ability to scan not only the anterior surface of the cornea but also the posterior surface in the cornea, Corneal tomography also compares between that maps of the anterior and posterior cornea and can give much more information and can discover subtle corneal conditions like keratoconus or other corneal ectasia conditions. 
 
Uses: 
Corneal tomography and topography can be used to map the cornea in order to diagnose, manage and follow up after several corneal conditions like:

• Astigmatism and keratoconus: Topography can help find astigmatism and early cases of keratoconus and track their progression.
• Scarring: Trauma (injury) or infections can scar the cornea. This changes the shape of the cornea.
• Contact lens fitting: Topography scans help find what type of contact lens can be worn to improve vision. If the scan shows a lot of distortion, sometimes a special hard contact lens (RGP) can help correct vision.
• Growths: The size of pterygia or other growths can be monitored with topography.
   

How Does Corneal Topography Help with Surgery?

• Refractive surgery: Topography and tomography can help in the decision of whether the cornea is suitable for refractive surgery. During refractive surgery like LASIK, the shape of the cornea is changed to correct refractive errors like myopia (nearsightedness). A topography scan helps the surgeon understand how to precisely reshape the cornea.
• Cataract: When cataracts make the eye’s natural lens cloudy, it is replaced with an intraocular lens (IOL) during cataract surgery. Corneal topography helps surgeons select the right IOL in some cases.
• Corneal transplants: After a corneal transplant, a surgeon may use corneal topography to help a patient heal correctly. The images help assess which stitches should be removed and when based on the shape of the cornea.
• Corneal cross-linking: Corneal cross-linking surgery helps strengthen a cornea with keratoconus. A topography scan may be done to see if this surgery is needed. After surgery, scans are done to monitor the eye.
   

How is the test performed? 
The test takes only few seconds and it's noninvasive (nothing touches your eye during the scan) and painless. You will be seated facing a large bowl with lighted circles inside it. The chin and forehead rests keep your head secure to get the clearest images. You will be asked to stare at a fixed target in the bowl while the pictures are taken.