I had a patient referred today who has keratoconus and a cataract and the question about which intraocular lens (IOL) to use came up as a wonderful discussion with the patient as well as my colleagues. While a Toric IOL may sound very appealing in a patient with a large amount of astigmatism, here are the problems:
a) Patients with KC have a dynamic (nonstatic) condition that could not only worsen but progression may include a change in both magnitude and direction of the astigmatism.
b) The astigmatism correctable by a Toric IOL is “regular” (orthogonal) astigmatism and patients with keratoconus have a large amount of non-orthogonal (asymmetric) and irregular (high order) astigmatism, not correctable with a Toric IOL.
c) Using a toric IOL essentially “adds” astigmatism to “offset” existing astigmatism and in doing so, you might be taking away the option of using a rigid contact lens on the cornea to treat astigmatism.
d) One condition where I think a Toric IOL might be a reasonable consideration is the patient who receives Intacs corneal ring segments and does not rub their eyes or push on their eyes during sleep (possibly cross linking as well) and demonstrates long-term stability with predominantly regular astigmatism.
Consideration of this matter is addressed by my good friend, colleague, and former Duke resident, Dr. Ralph Chu:
PREMIER SURGEON November/December 2011
Which IOL would you use in a patient with keratoconus?
Case presentation: The patient is a 75-year-old man who presented with gradual painless, progressive, decreased vision that interfered with his ability to read and to see street signs when driving during the past few years. He has a history of keratoconus and is having a harder time wearing his rigid gas permeable contact lenses due to increased discomfort.
Uncorrected visual acuity is 20/200 in the right eye and 20/400 in the left eye. Visual acuity with his contact lenses in is 20/60 in the right eye, 20/70 in the left eye and 20/50 in both. Best corrected vision without the contact lenses in is –5.50 +1.00 ×165 yielding 20/50 vision in the right eye and –6.00 +0.50 ×030 yielding 20/60 vision in the left eye. Brightness acuity testing under medium light is 20/100 in the right eye and 20/200 in the left eye.
IOP is normal. Slit lamp examination reveals corneal ectasia in both eyes, as well as 2+ nuclear sclerosis and cortical changes in each lens. There are some small drusen and retinal pigment epithelium changes noted in each eye, but the patient has a normal 0.2 cup-to-disc ratio.
- The patient has known keratoconus and cataracts that are now interfering with his vision. What lens options would you discuss with him?
- If you would choose a toric lens, how would you discuss this with the patient?
- How long would you have this patient out of contact lenses before calculating the IOL power?
Approach 1: John Bello, MD
This has the potential to be a complicated case with a possible unpleasant surgical outcome if it is not first discussed at great length with the patient.
First, I would want to know what the keratometry readings are and how stable they have been for as far back as possible to establish the stability of the cornea. This also assumes the recent decrease in vision is due to the cataract.
I would have the patient remove his hard contact lenses for at least 3 weeks and then perform keratometry readings on a weekly basis, for at least 3 weeks, until I feel they are stable. Then I would discuss the choice of a standard IOL vs. a toric IOL. I know the vendor doesn’t promote the use of toric lenses in keratoconus, but there is a possibility of using them, based on the corneal stability and the patient’s risk tolerance. If the cornea is unstable, one may consider pre-treating the cornea with an Intacs insert (Addition Technology) and/or corneal cross-linking.
The possible postop complications would consist of an unstable cornea, indicated by changing keratometry readings, which would create a worsening of his astigmatism. This may require an IOL exchange with a standard monofocal implant if a toric implant was initially selected.
Approach 2: Lance S. Ferguson, MD
Although this individual’s topographic maps suggest pellucid marginal degeneration (“kissing birds”), the precise pigeon-holing of the diagnosis is moot. The ectasia is obvious at the slit lamp, and he shows a high degree of irregular astigmatism in the central 3 mm.
Before any operative intervention, I would recommend that this patient undergo corneal cross-linking, even though his age of 75 years suggests he may already have had an adequate dose of UV. Not only should this preclude any ectatic progression with its associated unstable refractive problems subsequent to cataract extraction, but it may also create the opportunity for safer consecutive PRK should any significant spherical or cylindrical error remain. One may also consider Intacs to stabilize the topography prior to cross-linking.
After the cross-linking, I would follow serial topography with the RGP contact lenses discontinued until there was no change in the maps and select an Alcon toric IOL based on the most consistent A-scans and keratometry readings in the central 3 mm. I would advise against any incisional techniques to reduce cylinder.
During the preop stabilization period, I would arrange a consultation with a retinal specialist to assess the OCT findings suggestive of a retinal pigment epithelium tear or detachment, and if possible, perform potential acuity meter measurements. Irrespective of the potential acuity meter findings, I would counsel that the ultimate level of visual acuity in the left eye could nevertheless remain limited and that surgical refractive accuracy in both eyes is compromised by his underlying corneal condition. Finally, I would emphasize that our goal is not perfection but rather to reduce his dependency on contact lenses and improve his overall visual sensorium.
Approach 3: John D. Sheppard, MD
This patient has two decisions: First, do I want correction now? And second, am I willing to undergo multiple sequential procedures to obtain the best possible result? Due to acuity loss and glare disability, I would advise our patient to stop driving until correction is undertaken. Immediate ocular surface optimization, punctal plugs, nutrition, lid hygiene and directed appropriate measures are essential to eventual precise biometry and surgical success. When axial punctate keratopathy is eliminated and after at least 4 weeks of RGP-free time in the worst eye, axial length and keratometry readings can be taken.
If successful extended RGP wear is not possible and the patient is willing to consider a corneal collagen cross-linking procedure with at least 6 more months of follow-up care, sequential surgeries can be recommended. This idealized strategy would allow a quiet ocular surface, stabilized keratometry, minimized irregular astigmatism, and the best possible chance for obtaining an emmetropic IOL calculation. With corneal cross-linking, our patient also has the best chance of enjoying a contact lens-free life or using soft lenses and avoiding RGP dependence.
If urgency is paramount or the patient wishes to avoid multiple procedures, a best-shot calculation and IOL under these moderately steepened corneas is reasonable if patient expectations match. At 75, the prospects of severe rapid ectasia and steepening are minimal because the patient displays a mild, later-onset keratoconus phenotype. Many milder keratoconic patients are pleased with distance-correction monofocal IOLs bilaterally and a good refraction. If preop keratometry shows a clear-cut axis and only moderate distortion, the astute patient can be counseled regarding the advantages of a toric IOL, understanding that 20/20 uncorrected visual acuity is not obtainable.
Dr. Chu’s response
This case illustrates the difficulty of achieving accurate refractive outcomes in patients with keratoconus and cataracts. In my opinion, this would be an ideal situation for using intraoperative wavefront aberrometry to determine whether a toric IOL would be the best option and at which axis to place this IOL at the time of surgery.
The patient in this case presentation has not yet proceeded with surgery at this stage.
John Bello, MD, can be reached at Advanced Vision Specialists, 7447 W. Talcott Ave., Suite 406, Chicago, IL 60631; 773-775-9755 ; fax: 773-775-4306; email: firstname.lastname@example.org.
Y. Ralph Chu, MD, can be reached at Chu Vision Institute, 9117 Lyndale Ave. S., Bloomington, MN 55420; 952-835-0965 ; fax: 952-835-1092; email: email@example.com.
Lance S. Ferguson, MD, can be reached at Commonwealth Eye Surgery, 2353 Alexandria Drive, Suite 350, Lexington, KY 40504; 859-224-2655 ; email: firstname.lastname@example.org.
John D. Sheppard, MD, can be reached at Virginia Eye Consultants, 241 Corporate Blvd., Norfolk, VA 23502; 757-622-2200 ; fax: 757-622-4866; email: email@example.com.
Disclosures: Drs. Chu, Bello, Ferguson and Sheppard have no relevant financial disclosures.