How fast does untreated keratoconus progress? Why age and your baseline map decide the monitoring schedule

If you have keratoconus, one of the first questions you probably asked was "how quickly is this going to get worse?" The honest answer has always been "it depends". A new systematic review and meta-analysis published in Current Eye Research in 2026 pulls together 92 studies of untreated keratoconus and puts some numbers on that answer. It also points to two things that seem to matter most: how old you are, and how steep your cornea already is on your baseline map.

A note on what we are working from. This article is based on the published abstract; the full text was not available to us, so details such as the range of follow-up, the statistical spread around each estimate and the funding statement could not be checked. We have used only the figures reported in the abstract.

What the researchers did

Tsai and colleagues searched four medical databases (PubMed, Embase, Web of Science and Scopus) up to 25 September 2025 for studies that followed keratoconus eyes that had not been treated with cross-linking or any other intervention for at least six months, and that measured change in corneal shape or thickness over time. Ninety-two studies met the criteria, covering 30,342 untreated keratoconus eyes. Forty-seven had enough comparable data to be pooled in a meta-analysis, a statistical way of combining many separate studies into one estimate.

The main measure was Kmax, the steepest point on the corneal curvature map, measured in dioptres (D). Kmax is the number most keratoconus clinics use to decide whether your cornea is stable or progressing.

How fast does untreated keratoconus progress?

Pooled across the studies, Kmax increased steadily with time:

• a mean change of 0.28 D at less than 12 months of follow-up,
• 0.62 D at 12 months, and
• 1.21 D beyond 12 months.

Each change was statistically significant (all P < .05). If you have not met a P-value before: it is the probability that a result at least this large could have turned up by chance if there were really no change. Below .05 is the conventional threshold for "significant". A P-value does not tell you how big or important the change is; that is what the dioptre figures are for.

The abstract also reports that mean keratometry (Kmean, the average curvature), steep and flat keratometry, and the thinnest corneal thickness all showed significant deterioration beyond 12 months. The exact size of those changes is not given in the abstract, so we cannot quote them.

A word on what "1.21 D" means for you. It is an average across thousands of eyes. Some barely moved; others steepened much faster. Averages describe a population, not your cornea, which is exactly why individual monitoring matters, as we discuss in our earlier post on advanced corneal imaging and keratoconus monitoring.

Why age and your baseline map decide the schedule

The most useful part of this paper is the meta-regression, an analysis that asks which features of a study population were associated with faster progression. Two predictors stood out: younger age and higher (steeper) baseline Kmean.

In the analyses restricted to Pentacam tomography, the numbers were striking:

• for every 1 D steeper the baseline Kmean was, Kmax was predicted to progress by an extra 0.54 D at 12 months (P < .001), and
• for every 10 years older a person was, Kmax progression was predicted to be 1.46 D less (P < .001).

In plain terms: a 15-year-old with an already-steep cornea is in a very different situation from a 40-year-old with a mild cone. The teenager is likely to need more frequent corneal maps and a lower threshold for referral; the adult may reasonably be watched at longer intervals. This fits with our earlier post on early detection of keratoconus in New Zealand teenagers, and it is why a keratoconus-focused optometrist will ask your age and look hard at your first tomography scan before deciding how often to see you.

The authors also make a point about which number to trust. Kmax is a single steepest point and can bounce around between scans. Baseline Kmean, an average over a wider area, "may be a more reproducible predictor of subsequent progression". They suggest a multidimensional approach, looking at curvature, thickness and newer tomographic indices together rather than Kmax alone. That is how sequential corneal mapping is done well.

What this means for your care in Hamilton

This paper sharpens the pathway rather than changing it. The front door for keratoconus in New Zealand is a keratoconus-focused optometrist, not a surgeon. The optometrist team at Rose Optometry (Jagrut Lallu, Jacqueline Rowe and colleagues) diagnoses keratoconus, documents progression with sequential corneal tomography, fits scleral lenses where vision needs it, and refers to an ophthalmologist for corneal cross-linking at the right moment, which is when the maps show genuine progression rather than measurement noise.

This review gives that team a better sense of who to watch closely. If you are young, or your baseline map is steep, expect more frequent scans. If you are older with a mild, stable cone, expect visits to be spaced out, with the door kept open. Cross-linking is not something to rush into on a single scan, nor something to delay when the trend is clear.

What the studies can't tell us

• Abstract only. We have not seen the full paper, so we cannot report confidence intervals, how much the included studies disagreed with each other (heterogeneity), study quality, or funding.
• Averages, not individuals. A pooled mean of 1.21 D beyond 12 months hides a wide spread. Your own rate of change can only be measured by repeat scans of your own eyes.
• Different devices, different numbers. The strongest predictor findings come from Pentacam-based analyses. Corneas measured on other tomographers, or on older topographers, may not follow the same figures.
• Untreated does not mean untouched. The abstract does not say how many eyes wore rigid or scleral lenses, or how eye rubbing was handled.
• Observational data. None of this tells us what would have happened had these eyes been cross-linked; it tells us only what tends to happen without treatment.
• No New Zealand-specific data are identified in the abstract. Keratoconus is reported to be more common in Māori and Pacific communities, and we do not know whether the pooled figures apply equally to New Zealand patients.

If you have keratoconus and are not sure when you were last mapped, a keratoconus assessment with the Rose Optometry team is the place to start. You can book a keratoconus assessment online, or read more about the keratoconus service at Rose Optometry.

Reference

• Tsai TH, Hsu JH, Tsai CL, Shao SC, Hsiao CH, Lin KK. Natural History and Progression of Untreated Keratoconus: An Updated Systematic Review and Meta-Analysis. Curr Eye Res. 2026;51(8):881-899. PMID 41978273. https://doi.org/10.1080/02713683.2026.2651259