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Keratoconus
This change in corneal shape distorts vision and can lead to significant sight impairment. It typically affects both eyes, often starting in adolescence or early adulthood, and its progression can vary considerably between individuals.
Overview
Keratoconus is an eye condition characterised by a gradual thinning and steepening of the cornea, which is the transparent, dome-shaped outer layer at the front of the eye. Instead of maintaining its normal curved shape, the cornea progressively bulges forward, forming a cone-like protrusion. This change in shape prevents light from focusing correctly onto the retina at the back of the eye, leading to distorted and blurred vision [PMID:33606990].
While keratoconus usually affects both eyes, the degree of severity can differ significantly between them. The condition often begins during the teenage years or early 20s and can continue to progress for 10-20 years before stabilising. The speed and extent of progression are highly variable, making regular monitoring important.
Symptoms & clinical features
The initial symptoms of keratoconus are often subtle and can include mild blurring of vision and increased sensitivity to light (photophobia). As the condition progresses, vision typically becomes more distorted, and individuals may notice ghosting or multiple images, particularly in low light conditions. Night vision can also be significantly affected, with glare and halos around lights becoming more prominent [PMID:33606990].
Another common symptom is frequent changes in eyeglass prescription, as standard corrective lenses become less effective. In more advanced stages, scarring on the cornea can occur, further impairing vision. Some individuals may also experience eye irritation or discomfort, although pain is not a typical feature of keratoconus itself.
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Affected organs
Keratoconus exclusively affects the eye, specifically the cornea. The cornea plays a crucial role in focusing light onto the retina, and its normal shape is essential for clear vision. In keratoconus, the structural integrity of the corneal tissue is compromised, leading to its characteristic thinning and conical shape.
Risks & severity
The severity of keratoconus varies widely among individuals. In mild cases, vision can often be corrected with eyeglasses or soft contact lenses. However, as the condition advances, specialised contact lenses, such as rigid gas permeable lenses, are often required to achieve functional vision [PMID:30177708].
Untreated or rapidly progressive keratoconus can lead to significant vision impairment and, in advanced cases, may necessitate corneal transplantation. The lifetime risk of developing keratoconus is estimated to be around 1 in 2,000 in the general population. Factors that may influence progression include age of onset (earlier onset is sometimes associated with more rapid progression) and excessive eye rubbing, which is thought to exacerbate corneal thinning.
Genetic causes
Keratoconus is considered a complex or polygenic condition, meaning it is influenced by a combination of genetic factors and environmental elements. While no single gene has been identified as solely causative, research suggests that multiple genes may contribute to an individual's susceptibility to developing the condition. These genes are thought to play roles in maintaining the structural integrity of the cornea and its response to stress. However, the exact genetic mechanisms are still being investigated.
Environmental factors, such as eye rubbing, contact lens wear, and allergic eye conditions, are also believed to interact with genetic predispositions to influence the development and progression of keratoconus. This complex interplay means that even with a genetic predisposition, not everyone will develop the condition, and its severity can vary even within families.
Inheritance pattern
The inheritance pattern for keratoconus is considered polygenic or complex. This means that it doesn't follow a simple Mendelian inheritance pattern (like autosomal dominant or recessive). Instead, multiple genes, each contributing a small effect, combine with environmental factors to increase an individual's risk.
While there is often a family history of keratoconus, the way it is passed down is not straightforward. If one family member has keratoconus, other family members may have an increased risk, but it's not guaranteed they will develop the condition. Genetic counselling can help families understand these complex risks.
Diagnosis & testing
The diagnosis of keratoconus typically begins with an eye examination by an ophthalmologist or optometrist. Early signs may include irregular astigmatism that cannot be fully corrected with standard glasses. Specific diagnostic tests are then performed to confirm the presence and assess the severity of keratoconus.
The most important diagnostic tool is corneal topography, which maps the curvature and thickness of the entire corneal surface. This test can detect the characteristic steepening and thinning of the cornea. Other tests, such as pachymetry (measuring corneal thickness) and slit-lamp examination (to look for specific signs like Vogt's striae or Fleischer's ring), also aid in diagnosis. Genetic testing is not routinely used for diagnosing keratoconus due to its complex inheritance pattern.
Management & lifestyle
The management of keratoconus focuses on correcting vision, slowing or halting disease progression, and, in advanced cases, restoring corneal shape. In early stages, eyeglasses or soft contact lenses may provide adequate vision correction. As the condition progresses, specialised contact lenses, such as rigid gas permeable (RGP) lenses, hybrid lenses, or scleral lenses, are often prescribed to achieve better visual acuity by creating a smooth refractive surface over the irregular cornea.
For most individuals where the condition is progressing, corneal collagen cross-linking (CXL) is a common treatment. This procedure uses ultraviolet light combined with riboflavin eye drops to strengthen the corneal tissue and prevent further bulging [PMID:30177708]. In severe cases where vision cannot be corrected with contact lenses or significant corneal scarring occurs, surgical options like corneal transplants (keratoplasty) may be considered. Regular follow-up with an ophthalmologist is essential to monitor progression and adjust treatment as needed.
UK care pathway
In the UK, individuals with suspected keratoconus would typically be referred by their optician or GP to an ophthalmologist. The ophthalmologist will conduct comprehensive eye examinations and specialised corneal imaging to establish a diagnosis. Management plans are then developed, which may include referral to contact lens specialists or consideration of treatments like corneal collagen cross-linking or, in advanced cases, corneal transplantation.
While there isn't a specific NHS R-code for diagnostic genetic testing for keratoconus due to its polygenic nature, clinical geneticists or genetic counsellors may be involved if there are unusual features or a strong family history that warrants further investigation into broader inherited eye conditions. The NHS Genomic Medicine Service focuses on rare and inherited diseases with clearer genetic causes.
Frequently asked questions
What causes keratoconus?
Keratoconus is thought to be caused by a combination of genetic and environmental factors. While specific genes are being researched, it's not a single gene disorder. Factors like excessive eye rubbing, allergies, and certain systemic conditions may also contribute.
Can keratoconus lead to blindness?
While keratoconus can significantly impair vision and cause severe distortion, it rarely leads to complete blindness. However, without proper management, it can severely reduce vision quality and may require surgical intervention like corneal transplantation in advanced stages.
Is keratoconus curable?
Currently, there is no cure for keratoconus in the sense of reversing the corneal changes. However, treatments such as corneal collagen cross-linking can effectively halt or slow its progression, and various types of contact lenses or surgical procedures can help restore functional vision.
Can diet or lifestyle changes help with keratoconus?
There is no specific diet or lifestyle change proven to cure or prevent keratoconus. However, avoiding excessive eye rubbing is strongly recommended as it can worsen the condition. Managing allergic eye conditions can also reduce the urge to rub eyes, which may be beneficial.
How often do I need eye check-ups if I have keratoconus?
The frequency of eye check-ups depends on the severity and stability of your keratoconus. Initially, more frequent monitoring (e.g., every 6-12 months) may be needed to assess progression. Once stable, annual check-ups might be sufficient, but your ophthalmologist will advise you based on your individual condition.
References
- Santodomingo-Rubido J, Carracedo G, Suzaki A. Keratoconus: An updated review. Contact lens & anterior eye : the journal of the British Contact Lens Association. 2022. PMID: 34991971
- Bui AD, Truong A, Pasricha ND. Keratoconus Diagnosis and Treatment: Recent Advances and Future Directions. Clinical ophthalmology (Auckland, N.Z.). 2023. PMID: 37736107
- Gupta Y, Shanmugam C, K P. Pediatric keratoconus. Survey of ophthalmology. 2025. PMID: 39396644
- Asimellis G, Kaufman EJ. Keratoconus. 2024. PMID: 29262160
- Andreanos KD, Hashemi K, Petrelli M. Keratoconus Treatment Algorithm. Ophthalmology and therapy. 2017. PMID: 28755306
- Mannis MJ, Ling JJ, Kyrillos R. Keratoconus and Personality-A Review. Cornea. 2018. PMID: 29215397
- Unni P, Lee HJ. Systemic Associations with Keratoconus. Life (Basel, Switzerland). 2023. PMID: 37374145
- Sugar J, Macsai MS. What causes keratoconus? Cornea. 2012. PMID: 22406940