Cataract and Keratoplasty
When both cataract and corneal opacity contribute to a patient’s vision loss, the surgeon has 3 options:
Remove the cataract first.
Repair the cornea first.
Combine the procedures.
Removing the cataract first requires adequate visualization of the anterior segment. It may be possible to remove the cataract and monitor the patient for worsening corneal opacity; however, eyes that exhibit corneal endothelial dysfunction are at higher risk of corneal decompensation following cataract surgery. Signs and symptoms of corneal endothelial dysfunction are microcystic edema, stromal thickening, low cell count on specular microscopy, and/or diurnal fluctuations in vision with prolonged blurred vision upon waking. Keratoplasty is indicated in these eyes.
A penetrating keratoplasty (PKP) or an endothelial keratoplasty (EK) may be performed, either as primary surgery or as part of a combined procedure with cataract extraction (ie, a triple procedure). The advantages of performing keratoplasty as a stand-alone procedure include less postoperative inflammation and more reliable keratometry readings for future calculation of IOL power. In patients with primarily corneal endothelial disease, the advantages of EK over PKP include faster rehabilitation and more dependable keratometry readings with which to calculate IOL power, although a hyperopic shift from 0.50 D to 1.50 D may be encountered.
A triple procedure (combined keratoplasty [PKP or EK], cataract extraction, and IOL implantation) may be chosen if both the cataract and the corneal disease are significant and the patient would benefit from concurrent treatment. Advantages of the triple procedure include a single visit to the operating room, which reduces the attendant perioperative surgical risks, and relatively rapid rehabilitation. Disadvantages of PKP with cataract surgery are decreased predictability of IOL calculation and a period of “open sky”; that is, exposure of the intraocular contents while the cataract is removed and the IOL is placed, prior to replacement of the corneal button. IOL power calculation may be less reliable for eyes that have undergone PKP than for those that have undergone EK.
In conjunction with cataract surgery, the advantages of EK (vs PKP) include the following:
faster corneal rehabilitation
higher likelihood of regular astigmatism postsurgically
relative ease of regrafting
The disadvantages of EK include the following:
Patients with EK often have hyperopic shifts from their corneal surgeries; therefore, when this procedure is combined with cataract surgery, it is preferable to aim for a slightly myopic correction. Cornea surgeons often find EK easier to perform in a pseudophakic eye than in a phakic eye. (For a detailed discussion of keratoplasty procedures, see BCSC Section 8, External Disease and Cornea.)
Even if the cataract is not the primary source of vision impairment, it may be advisable to extract it at time of corneal surgery because of the eventual need for cataract removal, the possible progression of cataract due to prolonged postoperative corticosteroid therapy, and the risk of additional damage to the corneal endothelium during secondary surgery.
Hwang RY, Gauthier DJ, Wallace D, Afshari NA. Refractive changes after Descemet stripping endothelial keratoplasty: a simplified mathematical model. Invest Ophthalmol Vis. 2011; 52(2):1043–1054.
Excerpted from BCSC 2020-2021 series: Section 11 - Lens and Cataract. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.