CORNEAL DISEASE

Rudy MMA Nuijts MD

Performing cataract surgery in eyes with corneal pathologies like keratoconus or Fuchs syndrome poses many special problems, but there are a few simple rules that can help optimise outcomes, Rudy MMA Nuijts MD, PhD told a Young Ophthalmologists Symposium at the 19th ESCRS Winter Meeting in Istanbul, Turkey.
For example, in eyes with minimum and moderate keratoconus, measured keratometric values have sufficient accuracy for use in intraocular lens (IOL) power calculations. However, in eyes with advanced keratoconus, it is better to use a standard K value of 43.5D to avoid hyperopic outcomes due to an overestimation of the actual K values, said Dr Nuijts, University Eye Clinic, Maastricht, The Netherlands. 
“If you implant a low-power IOL in the eye and then you have to do a keratoplasty later on you will end up with a very low-power lens and a very significant hyperopic shift that will be difficult to correct,” he added.
Although keratoconus is generally a contraindication for toric IOLs, studies have shown that the lenses actually tend to be effective in eyes with stable stage 1 to stage 2 of keratoconus (Figures 1 and 2). (Visser N et al, Cataract surgery with toric intraocular lens implantation in keratoconus: a case report. Cornea. 2011 Jun;30(6):720-3)
In such cases, it is important to assess the effect of the cataract versus that of the keratoconus on the amount of vision loss. That may be achieved through reviewing the patients’ charts for their visual acuity and their K values over time. It is also important to remember that if the patient should require rigid contact lenses or a keratoplasty procedure later on they may require exchange of the toric IOLs for spherical IOLs.

Fuchs syndrome
In eyes with Fuchs syndrome, cataract surgery should only be performed without endothelial keratoplasty if the corneal thickness is 620µm to 630µm (Figure 3). (Doors M et al, Phacopower modulation and the risk for postoperative corneal decompensation: a randomized clinical trial. JAMA Ophthalmol. 2013 Nov;13 (11):1443-50)
A soft-shell ophthalmic viscosurgical device (OVD) technique should be used in such cases. In addition, the refractive target should be low myopia because of the hyperopic shift that may be induced by an endothelial graft later on. 
In eyes where the Fuchs syndrome is at a more advanced stage, the surgeon has to choose between doing two separate procedures, the cataract procedure followed by the endothelial keratoplasty, or both together in a triple procedure.
“The advantage of a two-stage procedure is that there is a more stable anterior segment which makes the surgery a little bit easier later on,” Dr Nuijts said.
When performing a triple procedure, the best results are generally obtained performing phacoemulsification followed by endothelial keratoplasty, he added. 

Rudy Nuijts: rudy.nuijts@mumc.nl
Nienke Visser: nienke.visser@mumc.nl