The Stages of Keratoconus

How Common Is Keratoconus?

Older studies once suggested that keratoconus was rare, with estimates of about 1 in 2,000 people. However, newer diagnostic tools such as corneal tomography have revealed much higher numbers.

• A 2025 PLOS study in Japan found keratoconus in 0.85% of adults and keratoconus-suspect cases in 1.46%.
• Other international research shows prevalence ranging from 1 in 750 to 1 in 50, depending on the population studied and diagnostic methods.
• In the Philippines, while exact prevalence data is limited, eye specialists report increasing numbers of diagnosed cases, likely due to improved screening.

These findings highlight that keratoconus is more common than previously believed, particularly among younger age groups.

Stages of Keratoconus

Early Stage (Mild or Subclinical Keratoconus)

The early stage is the most important to detect, because this is when interventions are most effective.

Key Characteristics:

• Subtle vision changes: mild blurring, ghosting, halos, or double images.
• Increased light sensitivity, especially at night.
• Frequent prescription changes for glasses.
• Corneal shape changes detectable only with imaging tools.
• Sometimes referred to as forme fruste keratoconus or early-onset keratoconus.

Diagnostic Tools:

• Corneal topography is critical, as it reveals irregular curvature before clinical symptoms become severe.
• Pachymetry helps detect thinning, even when patients report only mild symptoms.

Treatment:

• Eyeglasses or soft contact lenses often suffice at this stage.
• Close monitoring is required.
• In some cases, doctors may recommend corneal collagen cross-linking (CXL) to strengthen the cornea and prevent progression.

Intermediate Stage (Moderate Keratoconus)

If the disease progresses, patients move into the moderate stage.

Key Characteristics:

• More pronounced cone-shaped cornea.
• Moderate vision impairment not fully correctable with glasses.
• Worsening astigmatism.
• Corneal thinning becomes more evident.

Diagnostic Tools:

• Keratometry shows increased curvature.
• Tomography can highlight changes in the posterior corneal surface.

Treatment:

• CXL is highly recommended to stop or slow progression.
• Specialty contact lenses such as rigid gas permeable (RGP), hybrid, or scleral lenses may provide clearer vision.
• Studies confirm that early intervention with CXL can stabilize the disease in up to 90% of cases.

Advanced Stage (Severe Keratoconus)

In severe cases, keratoconus reaches its advanced stage, significantly affecting quality of life.

Key Characteristics:

• Severe vision loss.
• Significant corneal bulging.
• Corneal scarring that further distorts vision.
• Complications such as corneal hydrops, where fluid suddenly enters the cornea and causes swelling.

Diagnostic Tools:

• Advanced imaging may no longer provide accurate measurements if scarring is extensive.

Treatment:

• Corneal transplant (keratoplasty) is often required when vision cannot be corrected by lenses.
• Alternatives such as Intacs (intracorneal ring segments) may help in select cases.
• Scleral lenses may still improve vision for some patients.

Treatment Pathways by Stage

Early Stage:

• Glasses, soft lenses.
• Observation and regular monitoring.
• Preventive cross-linking in select cases.

Intermediate Stage:

• Corneal collagen cross-linking (gold standard).
• Specialty lenses: RGP, scleral, hybrid.

Advanced Stage:

• Corneal graft (keratoplasty).
• Intacs or corneal implants.
• Custom scleral lenses.