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There are two kinds of "custom" laser eye surgeries: topography-guided procedures and wavefront-guided procedures.
Topography-guided procedures are used almost exclusively for therapeutic purposes (versus wavefront procedures which are commonly used on primary LASIK procedures now). Topography-guided procedures are typically used to attempt to correct gross ablation defects, that is, large abnormalities of the corneal surface caused by a previous laser eye surgery, such as decentration, irregular astigmatism or overly small optical zones. Topo procedures are also sometimes used to attempt to correct irregular astigmatism caused by other complications.
Topography captures the actual shape of the cornea, as opposed to wavefront aberrometry which measures the wavefront error as light passes through the eye. For this reason, when there are significant abnormalities, using topography data is thought to be more appropriate. |
