Keratoconus is an eye condition affecting the cornea, the clear, dome-shaped front surface of the eye. This progressive disorder causes the cornea to thin and bulge outward, forming a cone-like shape. This altered curvature distorts vision, leading to irregular astigmatism and nearsightedness, which results in blurry and distorted vision. The condition typically progresses over several years, often stabilizing in mid-adulthood. While the exact cause remains under investigation, it is understood to involve a combination of genetic and environmental influences.
Global Occurrence Rates
The reported prevalence of keratoconus varies significantly across different regions and studies, largely due to diverse diagnostic criteria and methodologies. Historically considered rare, recent data suggests it may be more common than previously thought. Some studies indicate global prevalence rates ranging from 0.3 to 54.4 per 100,000 people per year. Certain areas, like the Middle East and Central India, have reported higher prevalence rates, sometimes affecting up to 5% of the population. This wide range highlights the challenge in pinpointing an exact global figure, as detection methods and population screenings differ.
Annual incidence rates also show variability, with estimates ranging from 50 to 230 cases per 100,000 population. For example, in Denmark, the incidence has been estimated at 1.3 per 100,000 per year. In the United States, a 2019 study indicated a national prevalence of 0.04% among Medicaid and Children’s Health Insurance Program enrollees. These figures underscore that while keratoconus is not universally widespread, its occurrence is notable and can be regionally concentrated.
Demographic Patterns
Keratoconus typically manifests during adolescence or early adulthood, with onset most often observed between 20 and 30 years of age. Progression of the condition usually continues until approximately 35 years of age, after which it tends to stabilize. While keratoconus affects both men and women, some studies suggest a slight male predominance. However, other research indicates no significant gender difference or even a higher incidence in females in some populations.
Ethnic background also plays a role in keratoconus prevalence. Populations of Middle Eastern and South Asian descent, including individuals of Indian and Pakistani origin, have shown higher rates compared to Caucasian populations. For example, a UK study found a higher incidence in Asian communities compared to Caucasians. This variation may be linked to a combination of genetic predispositions and environmental factors.
Factors Influencing Reported Figures
The variability in reported keratoconus prevalence figures can be attributed to several factors, particularly advancements in diagnostic technologies. Improved imaging techniques, such as corneal topography and tomography, allow for earlier and more frequent detection of subtle corneal changes, including subclinical cases that might have previously gone undiagnosed. Corneal topography, which maps the surface curvature of the cornea, is now considered a standard for screening. These tools can identify keratoconus even before visual symptoms become apparent.
Increased awareness among clinicians also contributes to higher detection rates. As healthcare professionals become more adept at recognizing early signs of the condition, more individuals receive a diagnosis. Population screening efforts, particularly in settings like preoperative assessments for refractive surgery, also uncover previously undiagnosed cases. Environmental factors, such as chronic eye rubbing and allergic conditions like atopy, are recognized as potential influences on individual risk, which can indirectly affect observed commonality within populations.