Corneal topography in cataract surgery

Keratometry and videokeratography are the most important means of evaluating induced corneal changes after surgery and have comparable sensitivities in the paracentral region of the cornea. When cataract surgery is planned, corneal topography can be used preoperatively in the calculation of IOL power, particularly in difficult cases, such as in patients who have undergone corneal refractive surgery or penetrating keratoplasty. A study published in the past year suggests that the mean power in ring 3 of the Tomey TMS-1 videokeratoscope (Cambridge, MA) appears to give the most accurate estimate of corneal power for the calculation of IOL power after radial keratotomy. In the case of PRK, traditional methods of determining the corneal power can lead to great amounts of anisometropia. Further research is needed to develop more accurate methods of calculating IOL power after PRK. Videokeratography can also be used before cataract surgery in planning the location and size of the incision. In general, smaller temporal incisions result in less astigmatism than do larger superior incisions. Postoperatively, videokeratography can be used to detect tight sutures, torsion of the wound, internal wound gape, and irregular astigmatism, as well as to guide suture removal or in cases where best-corrected visual acuity is not adequate and there are no other obvious causes for poor vision to determine if corneal irregularities are present.