The long-term goal of this project is to utilize very high-speed optical coherence tomography (OCT) technology to guide surgical treatments of corneal diseases. OCT is well known for its exquisite resolution, but until recently it has not had sufficient speed to capture the shape of the cornea because of eye motion during OCT scanning. The development of Fourier-domain (FD) OCT technology has made the requisite speed possible. The objective of this project is to develop methods for imaging the cornea with an FD-OCT system that will precisely measure corneal shape and use this information to guide surgery. Cataract surgery in patients with previous laser vision correction often leads to significant near- or far-sightedness, a problem that could be resolved by using a more accurate intraocular lens power selection formula based on the measurement of corneal refractive power with OCT.
Inclusion Criteria: * The subjects will be patients seeking cataract surgery with implantation of monofocal IOLs (including toric IOLs) but not multifocal or accommodative IOLs. * Subjects will have had post-laser vision correction (LVC) such as previous LASIK, PRK, laser sub-epithelial keratectomy (LASEK), epi-LASIK (surface laser ablation under a microkeratome-created epithelial flap) or RK. The post-LVC group will be subdivided into those who have previous hyperopic LVC and those who have previous myopic LVC. Exclusion Criteria: * Inability to give informed consent. * Inability to maintain stable fixation for OCT imaging. * Inability to commit to required visits to complete the study. * Eyes with concurrent cataract, retinal diseases, glaucoma, or other eye conditions that may limit the visual outcome after surgery.