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Trifocal IOLs can, if implanted with caution, be suitable for patients with keratoconus.
Special to Ophthalmology Times®
Premium IOLs have a very high-tech, sophisticated optical system that works excellently when the cornea is in perfect condition. Therefore, they are contraindicated in patients who have corneal haze, scar, or oedema.
A patient who has a posterior corneal elevation is susceptible to higher-order aberrations (HOAs) or early keratoconus.
Consequently, many surgeons will refrain from using premium IOLs in such cases. As one of the first surgeons in Saudi Arabia to use a trifocal lens, I meticulously select my patients.
Addressing the challenge
In Saudi Arabia, keratoconus is prevalent because of the dry atmosphere, seasonal allergies, and consanguinity.
However, not all patients have the same severity of disease. Some live their entire lives without knowing they have keratoconus or without signs of the condition. Others present early with signs and symptoms.
Many patients who present to me with the desire to be spectacle-free have questionable corneal tomography images.
The first patient with keratoconus I treated with a trifocal lens (AT LISA tri toric 939 M/MP; Carl Zeiss Meditec) was one of my colleagues, a 52-year-old physician with a mild but stable form of keratoconus.
Her central cornea seemed to be normal and the steepening was at the inferior part of the cornea, sparing the central 5-mm zone. The HOA at the 6-mm zone was 1.2 μm, outside the normally accepted range of up to 0.5 μm.
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The patient was keen to try trifocal lenses, so after long discussion and counselling the procedure was undertaken.
Postoperatively, she was incredibly happy, with uncorrected visual acuity 6/6 at near, distance, and intermediate. She had no visually disturbing aberrations.
I then performed the same procedure on her sister, who suffers from subclinical keratoconus and who also responded very well.
That is when I began to consider premium IOLs for certain cases of patients with keratoconus. I developed my own criteria for selection and, so far, patients have been very satisfied.
I have performed this procedure on 4 patients (8 eyes) with different categories of keratoconus but who all have 1 thing in common—the central 5-mm zone with an accepted range of HOA. It is not extremely high, but it is apparent that they do not have a normal posterior cornea.
Related: Estimating the total cornea power in keratoconus patients
During diagnosis, all patients undergo a routine, complete ophthalmic examination, which includes dry and wet refraction.
Patients also undergo a meticulous clinical assessment and detailed history taking, including family history, previous trauma, allergies, any spectacles changes and the frequency of these changes, and contact lens use.
Next, we perform corneal tomography, which is key for diagnosing keratoconus and precisely shows the anterior corneal curvature and the posterior corneal curvature.
Using 4-maps analysis, I perform the Belin/Ambrosio Enhanced Ectasia analysis and I study them carefully. Then I check the elevation maps, both in the forms of best-fit sphere and the best-fit toric ellipsoid.
I compare the maps and see whether the patient has good spectacle correction. If the patient does not have high central aberration, I then consider implanting a trifocal lens.
I speak with the patients about HOA photic phenomena and explain that they should anticipate some glare and halos over time.
I show them a picture of what glare and halos will look like so they know what to expect in the coming weeks. I also discuss mental adaptation and how their vision might be adapted to some aberration.
The good thing about patients with keratoconus is that they are used to a minimum amount of light, glare, and halos. If their central vision is OK, it is not exaggerated by premium lenses.
In all of my cases, glare and halos have turned out to be benign. However, I still like to set realistic expectations for patients.
I perform a routine phacoemulsification and painstakingly center the IOL. The plate-haptic design IOL centers itself easily and this is a strong point in favor of this design.
I like to place 1 suture to be sure that the lens does not move, especially if ectatic corneas have delayed healing or might have microleaks and fluctuation in eye pressure, which can change the lens position.
If the patient is receiving a toric lens, I ensure that the anterior chamber maintains its stability.
Related: IOL dilemma: Replacement or rescue
The postoperative regimen is similar to that of a routine phaco procedure. I examine the patient and remove the suture within the first week and no later than 2 weeks from surgery. Then I reassess the patient’s vision at 2 weeks, 6 weeks, and 3 months.
One step of utmost importance is assuring the patient that the lens is removable if he or she is not happy.
I offer patients a lens removal within the first 6 weeks if the aberration is higher than anticipated, and this provides some reassurance for the patient.
A 56-year-old breast cancer survivor with subclinical keratoconus wanted to treat herself by getting her eyesight back. She had heard about premium lenses and presented to me with a specific interest in trying them.
Related: Vision simulator provides preoperative glimpse at postoperative eyesight
Considering her condition, I conducted an examination and determined that she was fine to move forward with the procedure. She told me that she was reborn after 2 things: recovering from breast cancer and being spectacle-free for the first time in her life.
A 48-year-old man in a sensitive diplomatic position presented to me and shared that his use of spectacles was causing some embarrassment because there were times when he was unable to wear them but still required to read things and he felt that this was disabling him.
He was considering leaving his job because of his inability to focus.
He had posterior corneal elevation. The procedure was successful, and he has returned to work without anyone knowing that he had undergone the procedure.
Sometimes, surgeons can be afraid of technology because we do not know what is hidden behind it, and we refrain from exploring new advancements because we do not want our patients to have an unsatisfactory experience.
Given my recent experience with implanting premium lenses in challenging cases, I have changed my perspective and now view these opportunities as another way to give my patients a chance and a better outcome.
With the confidence that I can exchange the lens with minimum complications as a backup plan and considering that there is no cost to the patient because I work in a government hospital, I have to ask myself why not.
In the end, the patients with keratoconus who have received premium lenses are the happiest patients I have.
This is probably because they are used to some amount of HOA, so they adapt to their new IOLs faster and have higher tolerance than individuals with normal eyes.
About the author
Anoud Al Saati, MD
Al Saati is chief of the Anterior Segment Division at Prince Sultan Military Medical City, Riyadh, Saudi Arabia. She has no financial disclosures to make regarding any of the lenses used in this case series.