Keratoconus

Keratoconus is a progressive eye condition where the cornea—the transparent front part of the eye—becomes thinner and bulges outward into a cone-like shape. This abnormal curvature causes distorted and blurred vision, often not fully correctable with glasses. The name "keratoconus" is derived from the Greek words keras (cornea) and konos (cone).

As keratoconus progresses, it may lead to significant astigmatism, corneal scarring, and even severe vision loss. Early diagnosis is key to managing keratoconus effectively and preventing long-term visual impairment.

At Innovative Eye Care, located in Adelaide and Henley Beach, our optometrists have an extensive interest in keratoconus diagnosis and management. Our very own Lachlan Hoy authored the keratoconus chapter in the internationally renowned textbook Contact Lenses (2019)—a testament to our commitment to excellence.

What Is Keratoconus?

Keratoconus involves the thinning of the central cornea, causing it to protrude forward. This condition can lead to significant visual impairment, including:

• Blurred or distorted vision
• Increased sensitivity to light
• Halos and glare around lights, particularly at night
• Frequent changes in eyeglass prescription

Prevalence in Australia

Recent studies indicate that keratoconus affects approximately 1 in 84 Australian adults at age 20, making it one of the most prevalent corneal conditions in the country.

Risk Factors

Keratoconus can develop due to a combination of genetic and environmental factors:

• Genetic Factors: Family history of keratoconus, especially among first-degree relatives, and certain genetic conditions such as Down syndrome, Marfan syndrome, and Ehlers-Danlos syndrome.
• Environmental Factors: Chronic eye rubbing, allergies, hay fever, asthma, eczema, and floppy eyelid syndrome.

Early Signs and Diagnosis

Symptoms often begin in the teenage years and may progress into the 40s. Early signs include:

• Difficulty seeing at night
• Blurred or distorted vision
• Halos and glare
• Frequent changes in eyeglass prescription
• Blurred or distorted vision

A comprehensive eye examination is essential for diagnosis. Advanced imaging techniques, such as corneal tomography, are used to assess the cornea's shape and thickness, aiding in early detection and monitoring of the condition .

Diagnostic Tools

• Corneal Tomography: Provides detailed 3D maps of the cornea, including both anterior and posterior surfaces, and corneal thickness. This is the gold standard for diagnosing and monitoring keratoconus.
• Corvis ST: Measures the corneal biomechanics for a more comprehensive assessment of corneal health including early detection of keratoconus.
• Wavefront Aberrometry: Measures the amount of irregular optics in the eye. Important for fitting speciality contact lenses.
• Corneal Topography: Maps the front surface of the cornea, useful for contact lens fitting and assessing corneal shape.
• Slit Lamp Biomicroscopy: Allows visualisation of the cornea's structure and can detect signs like Fleischer's ring and Vogt's striae.
• Anterior Optical Coherence Tomography (OCT): Offers cross-sectional images of the cornea, aiding in the assessment of corneal layers and contact lens fitting.

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Management Options

Non-Surgical Treatments

1. Avoid Eye Rubbing

2. Spectacles

• In the early stages, vision may be corrected with glasses or soft contact lenses.

3. Custom Contact Lenses

When glasses are no longer effective, speciality contact lenses can restore clear vision:

• Rigid Gas Permeable (RGP) lenses
• Scleral lenses – vault over the cornea, providing a new optical surface

Our team uses advanced fitting software like EyeSpace to create precise, comfortable lens fits.

⚠️ Poorly fitted lenses can accelerate keratoconus progression.

Surgical Options

1. Corneal Collagen Cross-Linking (CXL)

Best for early-stage progressive keratoconus. CXL strengthens corneal tissue using UV light and riboflavin, reducing further thinning. It does not improve existing vision but aims to halt progression.

🔍 Minimum corneal thickness (~400µm) is required—another reason early diagnosis is critical.

2. Intracorneal Ring Segments (ICRS)

Plastic inserts reshape the cornea to reduce irregularity. Suitable for mild to moderate keratoconus.

3. Corneal Transplant (Keratoplasty)

Considered when:

• Vision cannot be corrected with lenses
• Corneal scarring is severe
• Contact lens intolerance occurs

Transplants may restore vision but carry risks, including graft rejection and the ongoing need for glasses or contact lenses.

Keratoconus vs. Pellucid Marginal Degeneration (PMD)

PMD is a rare condition causing thinning in the lower part of the cornea. While similar to keratoconus, PMD typically presents with against-the-rule astigmatism and requires specialised contact lens fitting, often with scleral lenses.

Book a Keratoconus Assessment in Adelaide or Henley Beach

If you're experiencing blurred vision, frequent prescription changes, or night glare, you may be developing keratoconus. At Innovative Eye Care, our optometrists are equipped with cutting-edge diagnostic tools and extensive experience to manage this condition effectively.

References

1) Lawless, M., Coster, D. J., Phillips, A.J., & Loane, M. 1989. Keratoconus: diagnosis and management. Aust N Z JOphthalmol, 17, 33-60.

2) Gomes, J. A., Rapuano, C. J., Belin, M. W.& Ambrosio, R., Jr. 2015. Global Consensus on Keratoconus Diagnosis. Cornea, 34, e-38-9.

3) Kennedy, R. H., Bourne, W. M. & Dyer,J. A. 1986. Apical changes in scarring in keratoconus. Am J Ophthalmol, 101,267-73.

4) Karimian, F., Aramesh, S., Rabei, H. M.,Javadi, M. A. & Rafati, N. 2008. Topographic evaluation of relatives of patients with keratoconus. Cornea, 27, 874-8.

5) Balasubramanian, S. A., Pye, D. C. &Willcox, M. D. 2013. Effects of eye rubbing on levels of protease, protease activity and cytokines in tears: relevance in keratoconus. Clin Exp Optom, 96,214-8.

6) Rabinowitz, Y. S. 1998. Keratoconus. Surveyof Ophthalmology, 42, 297-319.

7) Li, X., Rabinowitz, Y. S., Rasheed, K.& Yang, H. 2004. Longitudal study of normal eyes in unilateral keratoconus patients. Ophthalmology, 111, 440-6.

8) Romero-Jimenez, M., Santodomingo-Rubido, J.& Wolffsohn, J. S. 2010. Keratoconus: a review. Contact Lens and AnteriorEye, 33, 157-166.

9) Romero-Jimenez, M., Santodomingo-Rubido, J.& Wolffsohn, J. S. 2010. Keratoconus: a review. Contact Lens and AnteriorEye, 33, 157-166.

10) Lawless, M., Coster, D. J., Phillips, A.J., & Loane, M. 1989. Keratoconus: diagnosis and management. Aust N Z JOphthalmol, 17, 33-60.

11) Macsai, M. S., Varley, G. A. &Krachmer, J. H. 1990. Development of keratoconus after contact lens wear. Patient characteristics. Arch Ophthalmol, 108, 534-8.

12) Korb, D. R., Finnemore, V. M. & Herman,J. P. 1982. Apical changes and scarring in keratoconus as related to contact lens fitting techniques. J Am Optom Assoc, 53, 199-205.

13) Goodefrooij, D. A., Gans, R., Imhof, S. M.& Wisse, R. P. 2016. Nationwide reduction in the number of corneal transplantations for keratoconus following the implementation of cross-linking.Acta Ophthalmol, 94, 675-678.

14) Galvis, V., Tello, A., Ortiz, A. I. &Escaf, L. C. 2017. Patient selection for corneal collagen cross-linking: an updated review. Clin Ophthalmol, 11, 657-668.