Doctors classify keratoconus into stages based on how much the cornea has thinned and changed shape. While there are a few staging systems, one common method classifies it from mild to severe.

Keratoconus is an eye condition where the cornea, the clear front surface of the eye, becomes thin and bulges out. This can cause vision problems like blurriness and distortion.

Doctors use staging to determine how advanced the condition is. This helps them choose the most suitable treatment for you, ranging from specialized contact lenses to surgery.

Read on to learn more about the different stages of keratoconus.

Doctors typically stage keratoconus based on the severity of corneal thinning, the degree of corneal steepening (where the cornea becomes more cone-shaped), and the presence of scarring.

One common method of staging is the Amsler-Krumeich classification system. This categorizes keratoconus into four stages based on the extent of corneal changes. In this article, we’ll explain the symptoms and treatment options for each stage based on this system.

Stage 1 keratoconus is characterized by minimal corneal steepening and little to no scarring. You might have mild blurring, distorted vision, and increased sensitivity to light.

Treatment usually involves prescription eyeglasses or soft contact lenses.

Your doctor might also recommend rigid gas permeable (RGP) lenses, which are a type of hard contact lens. These are durable and oxygen-permeable, and they maintain their shape on the eye for clear vision. They’re custom-made for your eye shape.

Regular monitoring by an eye care professional is essential to track any progression and adjust treatment as needed.

Moderate keratoconus is characterized by increased corneal steepening and possible scarring. You may have more pronounced blurring, distorted vision, and noticeable astigmatism.

Treatment often involves RGP contact lenses to improve your vision by masking corneal irregularities.

Your doctor might also recommend corneal collagen cross-linking (CXL) to strengthen the cornea, slowing the progression of the condition.

During the CXL procedure, a professional will apply riboflavin (vitamin B2) eye drops to the cornea, which they’ll then expose to UV light. This combination strengthens the collagen fibers in the cornea, helping stabilize its shape and prevent further bulging.

A 2020 study found that 1 year after CXL treatment, there was no significant change in keratoconus stage compared with before the treatment. This indicates that CXL is associated with slower keratoconus progression.

Another treatment option is Intacs, which are small plastic rings implanted into the cornea. These can enhance the shape of the cornea, improving your vision. In some locations, the segments are made of donor cornea tissue.

Advanced keratoconus is characterized by significant corneal thinning, pronounced bulging, and scarring. You may have blurring, distorted vision, and astigmatism.

Treatment options may include RGP contact lenses, custom or scleral lenses for improved vision correction, and CXL to stabilize the cornea and prevent further vision problems.

In severe cases, a corneal transplant (keratoplasty) may be necessary to restore your vision.

It’s also important to note that, in rare cases, people at this stage can experience hydrops, which is a buildup of fluid in the cornea. This can cause severe pain and redness, so it’s best to contact an eye doctor about it.

Severe keratoconus is characterized by a very thin and bulging cornea with extensive scarring. You could have severe vision impairment, significant astigmatism, and an irregular corneal shape that contact lenses can’t effectively correct.

If other treatment options don’t help, you may need a corneal transplant. The type of transplant you’ll need — either full-thickness (penetrating keratoplasty) or partial-thickness (deep anterior lamellar keratoplasty, or DALK) — depends on your individual case.

One study comparing penetrating keratoplasty and DALK found that DALK tended to have fewer side effects, such as cataracts, rejection of the transplant by the body’s immune system, and high eye pressure.

DALK also showed better results in terms of improving the number of cells in the inner layer of the cornea. This keeps the cornea clear.

The diagnostic tests that doctors use to determine the stage of keratoconus primarily assess the shape, thickness, and condition of your cornea. They can include:

  • Corneal topography: This gold-standard test creates a detailed map of the cornea’s surface, showing any irregularities or steepening characteristic of keratoconus. The severity of the irregularity can help determine the stage.
  • Pachymetry: This measures the thickness of the cornea. Thinning of the cornea is a hallmark of keratoconus, and the degree of thinning can indicate the stage of the condition.
  • Slit lamp examination: This exam allows your eye doctor to visually inspect the cornea for signs of thinning, scarring, or other irregularities. However, early stage keratoconus may go undetected on a slit lamp exam.
  • Refraction test: This test assesses the degree of nearsightedness or astigmatism caused by keratoconus, which can vary based on the stage of the condition.
  • Keratometry: This measures the curvature of the cornea, which is typically more pronounced in advanced stages of keratoconus.

Using AI for the diagnosis and staging of keratoconus

Artificial intelligence (AI) is revolutionizing eye care by aiding in the early detection and monitoring of conditions like keratoconus. AI can analyze corneal images to develop algorithms that can accurately distinguish between healthy and keratoconic eyes.

For example, one AI algorithm was able to identify different stages of keratoconus using images from over 3,000 eyes. Another algorithm, using 3,000 corneal images, could diagnose keratoconus with 99.3% accuracy.

Researchers have also used AI to predict how keratoconus might progress in individual cases, helping doctors decide when to start treatment.

Keratoconus is a progressive eye condition characterized by the thinning and steepening of the cornea, affecting approximately 1 in 375 to 1 in 2,000 people worldwide.

It’s often possible to manage mild cases with glasses or contact lenses, while more advanced stages may need treatments like CXL or surgery.

Early diagnosis and proper management can help maintain your vision and improve your quality of life. Detecting it early can prevent it from progressing, help retain your vision, and reduce the treatment you’ll need down the line.