Keratoconus is more common than you'd think

Keratoconus used to be described as a rare eye condition. If you have just been diagnosed, it can feel isolating, as though you are the only person you know with a cone-shaped cornea. A large 2025 review of studies from around the world suggests keratoconus is more common than many people assume, and that how often it is found varies a great deal from place to place.

A quick note: this article is based on the published abstract of the review. We were not able to read the full paper, so we have used only the numbers reported in the abstract.

What the researchers did

Researchers from the University of Ottawa in Canada carried out a systematic review and meta-analysis. They searched three large medical databases (MedLine, Embase and Scopus) up to January 2024 for studies reporting how many people have keratoconus (prevalence) and how many new cases appear each year (incidence). They included all ages, both sexes and every region.

• Studies included: 55, with 53 combined in the meta-analysis.
• Design: pooling of population and clinic studies, not a trial, so there was no treatment, comparator group or masking involved.
• Statistics: random-effects models, with heterogeneity (how much the studies disagreed) assessed using χ² and I² statistics.

A quick word on confidence intervals

Every figure below comes with a 95% confidence interval (CI). Think of it as a range of plausible values. If the range is narrow, the estimate is fairly precise. If it is very wide, the true figure could be much lower or much higher than the headline number. In this review, many of the ranges are very wide, which is a sign the underlying studies differed a lot.

What they found

Overall numbers

• Prevalence: 289.1 per 100,000 people (95% CI 124.2 to 671.1).
• Incidence: 4.0 new cases per 100,000 person-years (95% CI 2.5 to 6.3).
• Global estimate: the authors estimate that over 23.7 million people worldwide are affected.

Sex and age

Males had slightly higher odds of keratoconus than females (odds ratio 1.10; 95% CI 1.07 to 1.13). An odds ratio above 1 means higher odds in males, and because the whole range stays above 1, the difference is unlikely to be due to chance alone, although it is small.

The 20 to 29 age group had the highest prevalence (525.5 per 100,000; 95% CI 92.6 to 2822.6) and the highest incidence (20.8 per 100,000 person-years; 95% CI 12.7 to 24.1). This fits with what we see in clinic: keratoconus is often picked up in the teens and twenties. We cover this in more detail in our article on early detection of keratoconus in teenagers.

Big differences between regions

Prevalence varied widely across the world. Within Asia alone, it was lowest in East Asia (12.7 per 100,000; 95% CI 2.81 to 57.0) and substantially higher in West Asia (682.0 per 100,000; 95% CI 141.8 to 3213.1) and South Asia (1374.5 per 100,000; 95% CI 537.2 to 3471.5). The highest regional prevalence was reported in Africa, although the figures for Africa in the abstract do not line up neatly (the headline estimate sits outside its own stated range), so we would treat that result with caution.

These differences may reflect genetics, environment, how each study looked for keratoconus, and which groups of people were tested. The abstract does not tell us which of these matter most. The review did not report a separate figure for New Zealand.

Rising over time

Both prevalence and incidence increased over time in the pooled data, with the highest prevalence in studies after 2020 (1155.2 per 100,000; 95% CI 32.4 to 29682.7) and the highest incidence in 2015 to 2019 (15.23 per 100,000 person-years; 95% CI 8.5 to 27.3). Look at that post-2020 range: it is enormous, so the exact figure is very uncertain.

Does this mean keratoconus is truly becoming more common? Not necessarily. The abstract does not explain the cause. One possible explanation is that modern corneal tomography picks up milder, earlier cases that older equipment would have missed, but that is our interpretation, not a finding of this study.

What this means for you

If you have keratoconus, you are far from alone. It also means it is worth having family members checked, particularly younger relatives, as early detection allows careful monitoring.

The right first step is an assessment with a keratoconus-focused optometrist. At Rose Optometry in Hamilton, our optometrists, including Jagrut Lallu and Jacqueline Rowe, diagnose keratoconus, track any change with repeat corneal maps, refer to an ophthalmologist for cross-linking if progression is documented, and fit specialty lenses. For many people, scleral lenses can provide clearer, more comfortable vision. If you are interested in the research side of eye care in New Zealand, visit the New Zealand Eye Research Centre.

What the studies can't tell us

• Abstract only. We have not seen the full paper, including which countries were included or how each study defined keratoconus.
• Very wide ranges. Many confidence intervals span huge ranges, which means the pooled estimates are imprecise.
• Studies differed. Heterogeneity was assessed, but we cannot see the results in the abstract. Different screening methods, devices and populations make pooling difficult.
• Some figures don't add up. As well as the Africa figure, the abstract describes the overall prevalence as 0.24% of the population, which does not match 289.1 per 100,000. This may be a reporting error; we cannot check it without the full paper.
• No New Zealand estimate. We cannot say from this review how common keratoconus is here.
• Cause of the rise is unknown. Better detection, changing populations and real increases cannot be separated using these data.

The take-home message

Keratoconus appears to be more common than once thought, with the highest rates in people in their twenties and wide variation around the world. The numbers come with large uncertainty, but the practical message is clear: early assessment and careful monitoring matter. If you or a family member would like to be checked, you can book a keratoconus assessment with our optometrists in Hamilton.

References

• Sriranganathan A, Chan CC, Dhillon J, et al. Global Incidence and Prevalence of Keratoconus: A Systematic Review and Meta-Analysis. Cornea. 2026;45(9):1080-1092. PMID 40833011. https://doi.org/10.1097/ICO.0000000000003973