One of the most debatable and challenging topics in optometry and ophthalmology is the management of keratoconus patients requiring cataract surgery.
There’s no doubt that careful planning and clear communication is critical to cataract surgery success, particularly when your patient is keratoconic (KC). This involves the patient, optometrist, ophthalmologist, technicians etc.
Outcomes are usually excellent and patients can see out the rest of their days without having to wear contact lenses
A keratoconic fitted with contact lenses in their teens or twenties, will by definition, develop cataracts after 30 to 40 years of lens wear. Many keep going as long as they can, before cataract surgery becomes absolutely necessary, in order to retain their ability to drive legally, keep working and functioning with digital devices. In my experience, KC is often much worse in one eye than the other.
Intimate knowledge of your patient’s current and past history allows you to start the discussion.
AN EASY SOLUTION
For those with mild or forme fruste keratoconus (FFKC), and a history of reasonable best corrected vision in soft torics, disposable soft contact lenses (CLs), or spectacles, the decisions are almost as easy as in regular eyes. For toric soft lens or astigmatic spectacle lens wearers, a toric monofocal intraocular lens (IOL) is the first choice. Excellent acuity in both eyes and a history of successful monovision might mean we can replicate this with intraocular lenses (IOLs).
For wearers of high Dk low modulus soft lenses, one to four weeks of no CL wear before surgery – with stability confirmed by successive stable topographies over a week or two – seems to work. For these patients the whole process is usually completed in a matter of weeks. Post-surgery, we simply prescribe top up spectacles as indicated. Outcomes are usually excellent and patients can see out the rest of their days without having to wear CLs.
OBSTACLES
While toric IOLs can be implanted for some keratoconics, complex corneal rigid gas permeable (RGP) or scleral CLs are likely to be needed post-surgery.
Toric IOLs are not suitable for severe keratoconic patients – resulting vision will be inadequate, and a devastating refractive surprise can occur, with masses of vectordriven oblique/irregular astigmatism. By reverting to an RGP or scleral lens to restore a decent optical platform, we induce even more residual astigmatism. The only resolution is explantation of the toric IOL, or the fitting of complex prism ballast toric or bitoric corneal RGPs, or sclerals. To avoid this I usually work very closely with the surgeon and clearly detail the history and desired refractive targets.
As mentioned, one eye often has milder KC, (with a history of reasonable spectacle vision), and when this is the case, we target a toric IOL for that eye. For many, we achieve post-op vision of 6/12 or better, often in the 6/9 to 6/7.5 range. For the other, usually much worse eye, we use a non-toric monofocal IOL that’s targeted to a reduction in minus power of our final postop RGP/scleral. Of course we also need to cease CL wear before surgery for around six to eight weeks until topographically stable.
Patients wake up in the morning and see well with the better eye. Many will only wear the RGP for the worse eye for driving, watching sport and so on. Of course top up reading spectacles are usually necessary. The worse eye is also usually left with much better unaided vision.
A STABLE TEAR FILM
Where indicated, it’s important to implement treatment to ensure a stable tear film and healthy lids and lashes. This is widely recognised as critical to ensuring accurate biometrics and attaining targeted refractive end points. Wiping out nasty pathogens may also help reduce potential post-operative infections or endophthalmitis.
We can use a variety of strategies to treat meibomian gland dysfunction, blepharitis, Demodex and so on, per our favourite/ best practice methods. A history of apical abrasions, hurricane staining and/or recurrent corneal erosions, makes this even more critical. Counsel patients on managing drugs that may influence tear film stability or surgical outcomes.
