If Contact Lenses Work for Your Keratoconus, Is Surgery Necessary?

I am not writing this to answer "which is better, lenses or surgery"; there is no such contest. Lenses and treatments answer different questions: one answers "how do I see today", the other "what will my cornea be like tomorrow". In short: a lens corrects vision, but it does not change the course of the disease.

I need to draw a line at the outset: this article does not tell you "your lens is enough, do not have surgery", nor the opposite. That decision can only be made with an examination and topography. You can read my article on working out which step you are on for a fuller framework on when CXL and CAIRS come onto the agenda and in what order; my focus here is different: not to describe the steps again, but to explain what changes and what does not on the lens axis.

If you see well with a lens, surgery is not automatically needed

The role of rigid and scleral lenses in quality of vision in keratoconus

In keratoconus the cornea takes on an irregular, conical shape, so that light enters the eye in a scattered way. In the early stage glasses may be enough; but as the irregularity increases, glasses cannot fully correct this scatter, because a spectacle lens is a regular surface and the cornea is not. A rigid gas-permeable (RGP) or scleral lens fills the space between the surface of the eye and the lens with the tear layer, in effect creating a new, smooth optical surface. In many of my patients this gives a clarity that could never be reached with glasses. In a recent observational study of 26 patients with keratoconus, mean best-corrected visual acuity rose from 0.21 to 0.83 with rigid or scleral lens wear (p=0.001), and this improvement was significantly associated with a gain in quality of life (p=0.007); the authors noted that the findings are preliminary because of the small sample.¹

What "I see well" means: clarity, comfort and tolerance are assessed together

The question I ask my patients is not one-dimensional. When we say "I see well" we mean three things together: visual acuity is sufficient, the lens can be worn comfortably for most of the day, and this arrangement is sustainable in the long term. If all three are met, I have no particular reason to recommend surgery to a patient simply because they "see with a lens". What brings surgery onto the agenda is not vision itself but another axis, which I describe below: progression.

There is one thing a lens cannot do: halt progression

A lens is an optical correction; it does not change the cornea itself

Here we come to the sentence I repeat most to my patients: a lens sits on the cornea; it does not act within the cornea. A lens makes no structural change in the corneal tissue; it does not strengthen collagen fibres, stop thinning or slow steepening. What it does is place an optical solution in front of the irregular surface that exists at that moment. If the disease is still progressing, a lens may delay your noticing it, but it cannot stop the progression itself.

Why progression can be missed while wearing a lens

There is a particular difficulty here that I meet often in clinic: a lens, even when worn for a short time, can temporarily change the shape of the cornea; this is sometimes called the lens "moulding" the cornea. In a one-year follow-up study of 65 patients with keratoconus, scleral lens wear (8 hours a day for one year) was shown to lead to measurable changes in corneal thickness and in anterior and posterior curvature, although these changes did not impair visual acuity.² In practice this means that a topography taken with the lens in, or immediately after it is removed, may show not the cornea's "real", lens-free state but its state under the lens's effect at that moment. This is why, in monitoring progression, topography is taken after a period without the lens.

So when does surgery really come onto the agenda?

The critical distinction: if progression is documented, CXL comes onto the agenda, even if the lens works well

Here I need to correct a mistake in reasoning that most of my patients make: the sentence "I see with my lens, so my disease has stopped" is not correct. Seeing well with a lens is not proof that the disease is not progressing; the only thing that shows that is topography repeated over time. If real progression (for example an increase in maximum keratometry, or thinning) is documented on consecutive measurements, CXL comes onto the agenda however well your lens is working. In that case the aim is not to change your vision but to preserve the vision you have at that moment, with or without a lens. I do not go into the detail of how progression is defined and staged here; I covered it in my article on working out which step you are on.

Why the follow-up interval is kept shorter in young patients

The reason I see my younger patients more often is this: keratoconus is a dynamic disease that can run a faster course, especially in adolescence and young adulthood. Quality of vision with a lens can be perfectly good in this age group, and that can lead to the mistaken idea that "everything is fine, we can space out the check-ups". Yet the good vision the lens provides is exactly the thing that can mask progression underneath. The purpose of the check-up is to follow not your vision but how your cornea behaves over time.

Two habits also matter in this period: not rubbing the eyes and, if present, having eye allergy treated. Avoiding eye rubbing and keeping accompanying allergic disease well controlled are among the basic recommendations in the management of keratoconus.⁶

When a lens stops being enough

Lens intolerance: being physically unable to wear a lens

In some of my patients the problem is not quality of vision but being physically unable to bear the lens: redness, a gritty sensation, the lens slipping often, or unbearable discomfort after a certain part of the day. This is called "lens intolerance", and moving on to the next type of lens does not always solve it. Of 31 patients who could not tolerate a rigid or soft lens and moved to a hybrid lens (rigid centre, soft skirt), 3 also gave up this lens because of intolerance (9.7%).⁷ In a mixed group that also included patients with corneal scars and patients after transplantation or refractive surgery alongside keratoconus, 12.5% of 32 patients who moved to a mini-scleral lens (a large-diameter rigid lens that rests on the white of the eye without touching the cornea) again gave up the lens.⁸ These rates reflect not the general keratoconus population but special groups who already could not tolerate one lens; what they show is clear: lens intolerance is not a problem that is always solved by "trying a slightly better lens".

When lens-corrected vision itself is not enough

A second picture, which I meet less often but which is real, is this: the patient wears the lens comfortably, but lens-corrected visual acuity itself is not enough for daily life (driving, reading, working). This usually arises when the corneal irregularity exceeds what a lens can compensate for optically. These two pictures, the physical tolerance problem and optical insufficiency, are different problems and may point to different solutions.

Where CAIRS fits in

CAIRS does not halt progression; it changes the geometry of the cornea

CAIRS (corneal allogenic intrastromal ring segments) is a treatment that changes the geometry of the cornea with thin segments prepared from human donor tissue and placed inside the cornea. I have to make the same distinction here too: CAIRS does not halt progression. Like a lens, it is a tool for reshaping and correction, but unlike a lens it changes the cornea's own shape permanently. If the disease is still actively progressing, the shape improvement obtained with CAIRS cannot be reliably guaranteed to last without CXL.

How CAIRS becomes an option for patients with lens intolerance

The group in which CAIRS finds its most concrete place in clinic is precisely patients who cannot physically tolerate a lens. In a series evaluating 17 eyes (16 patients) treated with ring segments prepared from human donor tissue, best-corrected visual acuity improved from 0.43 logMAR to 0.19 logMAR after surgery (on the logMAR scale a smaller number means better vision; p<0.001), and maximum keratometry (Kmax) fell from 57.3 dioptres to 51.4 dioptres (p<0.001); the authors described this treatment as an effective option for visual rehabilitation, particularly in patients with lens intolerance.¹⁰ In the same series, 9 of the 17 eyes also received CXL at least one month after surgery because of previously documented progression¹⁰; even when the vision problem is solved with CAIRS, CXL comes onto the agenda separately if there is progression.

Does lens wear end after CAIRS, or lessen?

I have to be realistic with my patients here: CAIRS reduces the need for lenses in many patients, or brings vision to a level that can be managed with glasses, but I do not give a guarantee that "I will never wear a lens again". The result varies with the cornea's initial irregularity and the degree of improvement CAIRS provides; some patients manage with glasses after CAIRS, while others may still need the support of a thin lens. So think of CAIRS not as "surgery to get rid of lenses" but as "a treatment that changes the shape of the cornea".

Where transplantation sits in this picture: the third step

I keep transplantation short in this article because I have covered it in detail elsewhere. Briefly: transplantation is the third-step treatment that comes onto the agenda when the cornea has lost its transparency, when excessive thinning threatens surgical safety, or when earlier options such as lenses and CAIRS/CXL have fallen short; it is not the first option that comes to mind. In most patients who manage well with lenses or are reshaped with CAIRS, transplantation never comes onto the agenda.

Modern scleral lenses can postpone this step even in severe keratoconus. In a series of eyes with a maximum keratometry of 70 dioptres or more, 40 of 51 eyes prescribed scleral lenses were still wearing them at a mean follow-up of 30.15 months; according to the authors, the need for transplantation in this group fell by more than half.¹¹

You can read the full sequence in my article describing the CXL, CAIRS and transplantation steps. For the overall picture of keratoconus treatment and how these steps took shape over the past decade, see Keratoconus Treatment: The Last 10 Years.

Three questions to ask yourself

This list is not for you to make a decision; it is so that you discuss the right subject with your doctor when you go for your examination:

Who makes this decision, and how

This article does not make a diagnosis and does not make a treatment decision. I draw no conclusion such as "your lens is enough, surgery is unnecessary" or "even if your lens is enough, surgery is essential", because I cannot; what determines it is corneal topography, pachymetry (measurement of corneal thickness), a detailed examination and, above all, change over time. How well you see with a lens is only one part of this assessment; perhaps the least decisive part.

Frequently asked questions