Keratoconus

Progression and monitoring
of keratoconus

After the diagnosis, one question dominates all others: is this keratoconus changing? The answer determines what follows, more than the severity recorded on the day of the examination. Moderate but stable keratoconus does not call for the same approach as early keratoconus that shifts from one check-up to the next.

Why progression matters more than severity

Severity describes where your cornea stands today. Progression describes what it is in the process of doing. These are two different pieces of information, and it is the second that guides decisions.

Advanced but long-stable keratoconus essentially poses a question of correction: how to obtain the best possible vision with this cornea as it is. Keratoconus that is still discreet but changing poses a different question — how to halt its future course.

This is the purpose of monitoring: it does not merely record, it produces the information on which a decision can be based.

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Treating keratoconus →

What “progressing” means

Every measurement carries a degree of variability: two examinations performed on the same day never give strictly identical figures. Speaking of progression therefore implies a change that exceeds that variability, and not a mere difference of decimals between two reports.

The elements usually taken into account combine several parameters:

  • an increase in the curvature of the front surface of the cornea;
  • a change in the back surface, often the earliest;
  • thinning of the cornea at its thinnest point;
  • a change in the correction or in corrected vision, particularly in astigmatism.

There is no universally accepted definition of progression, nor a single threshold valid for every patient. It is a body of evidence, interpreted in the light of your age and of how long ago the diagnosis was made.

Two examinations can only be compared if they are comparable. Reference values vary from one technology to another: an examination performed on a different instrument, or under different conditions — lenses worn the day before, untreated dryness — cannot be set against the previous one. This is why it is useful to keep your earlier reports and to bring them to the consultation, including those carried out elsewhere.

How often to monitor

The rhythm of check-ups is not the same for everyone. It takes account of age, of how long ago the diagnosis was made, and of what previous examinations have shown.

As a rule, monitoring is closer in the months following diagnosis — the time needed to establish whether the disease is stable — then spaces out when several successive examinations agree. It is also closer in young patients, in whom progression is on average more rapid.

These intervals are indicative and adapted to each situation. A perceived change in vision warrants seeking advice sooner than the scheduled check-up.

In adolescents and young adults

This is the situation that demands the most attention. Keratoconus diagnosed before the age of twenty progresses on average faster and for longer than keratoconus discovered in adulthood, and the margin for manoeuvre is narrower.

Three practical consequences follow:

  • monitoring is closer, and finding a change there carries more weight;
  • controlling eye rubbing and treating any ocular allergy take on their full importance;
  • screening brothers and sisters is warranted at the same time.

Keratoconus →

What “stabilised” means

The course of keratoconus tends to slow over the years, without this constituting a rule on which to base an individual decision. Above all, stability is not an assumption: it is a conclusion, drawn from comparing successive examinations over a sufficient period.

Two nuances deserve emphasis. Keratoconus regarded as stable may change again. And stability of the disease does not mean the end of follow-up: vision, tolerance of lenses and the state of the cornea continue to evolve, and follow-up accompanies them.

Living with monitored keratoconus

Between check-ups, vision that fluctuates slightly with fatigue, dryness or lighting is usual and does not necessarily indicate progression. Adjusting the correction may be necessary more often than for another patient: that is a consequence of the disease, not a shortcoming of the previous correction.

Do not wait for the scheduled check-up

Seek advice without waiting for your scheduled appointment in the event of a rapid and unusual drop in vision, particularly if it is accompanied by frank pain or marked discomfort in the light.

When monitoring leads to a decision

Two situations lead to considering an intervention: documented progression, and vision that has become insufficient despite well-conducted optical correction. They do not call for the same responses.

In both cases the decision rests on examinations compared over time, never on an isolated one — and doing nothing, while continuing to monitor, remains a fully valid option.

Treating keratoconus →

Keratoconus to monitor, or examinations to compare?

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How the disease is recognised and measured

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