Author: Dr Val Phua
Estimated reading time: 20 minutes
Keratoconus is a condition in which the cornea—the clear front surface of the eye—becomes progressively thinner, weaker and more irregularly shaped.
A healthy cornea has a smooth, rounded dome shape. In keratoconus, an area of the cornea gradually steepens and bulges forward, producing a cone-like or asymmetrical shape.
This altered shape prevents light from focusing evenly on the retina and may cause:
- Blurred vision
- Distorted vision
- Irregular astigmatism
- Increasing short-sightedness
- Ghosting or multiple images
- Glare
- Halos
- Light sensitivity
- Difficulty driving at night
- Frequent changes in spectacle prescription
Keratoconus commonly begins during adolescence or early adulthood, although it can be detected in childhood or later life. It usually affects both eyes, but one eye may be considerably more affected than the other. Younger patients and those with steeper or more advanced corneas generally require particularly careful monitoring because progression may be faster.
Modern corneal imaging can detect keratoconus before obvious clinical signs or severe visual loss develop.
Treatment has two separate goals:
- Stabilise the cornea to prevent further progression.
- Improve vision by correcting the irregular corneal shape.
Corneal collagen cross-linking is the principal treatment used to stabilise progressive keratoconus. Glasses and contact lenses improve vision but do not reliably stop the underlying disease from worsening.
The Quick Answer
What Is Keratoconus?
Keratoconus is a corneal ectasia—a condition in which the cornea becomes abnormally thin and protrudes forwards.
The resulting corneal surface is not simply too steep. It is usually:
- Asymmetrical
- Irregular
- Optically distorted
- Thinner in the affected area
- Biomechanically less stable
This produces irregular astigmatism and higher-order optical aberrations that ordinary spectacles may not fully correct.
What Are the First Symptoms?
Early symptoms may include:
- Increasing astigmatism
- A prescription that changes frequently
- Vision that remains unclear despite new glasses
- Ghosting around words
- Multiple outlines around lights
- Glare while driving
- Difficulty seeing at night
- One eye becoming noticeably worse
- Eye strain or headaches from unequal vision
Some patients have no symptoms and are diagnosed during:
- A routine eye examination
- Assessment for LASIK
- Screening because a relative has keratoconus
- Investigation of unexplained astigmatism
- Corneal imaging before cataract surgery
Does Keratoconus Cause Blindness?
Keratoconus does not usually cause complete loss of all vision.
However, advanced disease can cause substantial visual disability through:
- Severe irregular astigmatism
- Corneal scarring
- Contact-lens intolerance
- Acute corneal hydrops
- Inability to obtain useful vision with glasses
Modern cross-linking, specialised contact lenses and corneal surgery mean that most patients can maintain or regain useful functional vision.
Can Keratoconus Be Cured?
There is currently no treatment that permanently restores the cornea to its original natural structure.
However:
- Cross-linking can stabilise progressive disease.
- Contact lenses can provide excellent visual correction.
- Corneal ring procedures may improve corneal shape in selected patients.
- Corneal transplantation can restore useful vision in advanced cases.
The condition is therefore manageable, particularly when detected early.
Can Eyedrops Treat Keratoconus?
No eyedrop has been proven to reverse established corneal thinning or reshape the cornea.
Eyedrops may nevertheless be important for treating associated:
- Allergy
- Itching
- Dry eye
- Blepharitis
- Contact-lens irritation
Controlling itch is important because repeated eye rubbing is strongly associated with keratoconus and may contribute to progression.
Understanding the Cornea
What Is the Cornea?
The cornea is the transparent front surface of the eye.
It lies in front of:
- The iris
- The pupil
- The natural lens
The cornea provides a large proportion of the eye’s focusing power.
For clear vision, it must remain:
- Transparent
- Smooth
- Regularly curved
- Mechanically stable
The Corneal Layers
The main corneal layers include:
- Epithelium
- Bowman’s layer
- Stroma
- Descemet’s membrane
- Endothelium
The stroma accounts for most of the corneal thickness and contains organised collagen fibres.
In keratoconus, the stromal structure becomes progressively thinner and mechanically weaker.
Why Does the Cone Cause Blurred Vision?
A regular cornea focuses incoming light into a relatively precise image.
A keratoconic cornea bends different light rays by different amounts, creating:
- Irregular astigmatism
- Coma-like aberration
- Ghost images
- Smearing
- Reduced contrast
- Poor night vision
This explains why increasing the strength of ordinary glasses may not produce completely clear vision.
How Common Is Keratoconus?
Older teaching often described keratoconus as affecting approximately 1 in 2,000 people.
Modern imaging detects milder and previously unrecognised disease, and current prevalence estimates vary substantially between populations.
A 2025 systematic review estimated a pooled worldwide prevalence of approximately 0.24%, or about 289 cases per 100,000 people. The prevalence varied markedly by age, geography and study method, with the highest rates occurring among younger adults and in certain regions of Africa, the Middle East and South Asia.
What Causes Keratoconus?
There Is No Single Cause
Keratoconus is believed to result from an interaction between:
- Genetic susceptibility
- Corneal biomechanics
- Cellular and biochemical changes
- Environmental exposure
- Mechanical trauma
- Hormonal factors
Different combinations may be important in different patients.
Family History
Keratoconus does not follow one simple pattern of inheritance in most families.
However, having an affected close relative increases risk.
A meta-analysis found strong associations between keratoconus and:
- Family history
- Eye rubbing
- Allergy
Relatives of affected patients may benefit from corneal imaging, particularly during adolescence or before refractive surgery.
Eye Rubbing
Frequent or forceful eye rubbing is one of the most important modifiable associations.
Rubbing may expose a susceptible cornea to repeated:
- Mechanical pressure
- Shearing stress
- Epithelial trauma
- Inflammatory mediator release
Patients should avoid:
- Knuckle rubbing
- Pressing the eye into a pillow
- Rubbing through the eyelid
- Repeatedly pushing on an itchy eye
The underlying reason for rubbing—such as allergy or dry eye—should also be treated.
Allergy and Atopy
Keratoconus may be associated with:
- Allergic conjunctivitis
- Vernal keratoconjunctivitis
- Eczema
- Asthma
- Allergic rhinitis
The relationship may involve both inflammation and repeated eye rubbing.
Down Syndrome and Other Conditions
Keratoconus is reported more frequently in association with conditions including:
- Down syndrome
- Certain connective-tissue disorders
- Leber congenital amaurosis
- Floppy eyelid syndrome
Not every patient with keratoconus requires extensive genetic or systemic investigation. The need depends on the history and examination.
Common Symptoms
Blurred Vision
Vision may remain blurred despite an apparently appropriate spectacle prescription.
Distortion
Straight lines may appear:
- Bent
- Slanted
- Stretched
- Compressed
- Uneven
Ghosting and Multiple Images
A single letter or light may appear to have:
- A shadow
- A second outline
- Multiple overlapping copies
- A tail extending in one direction
This may remain present when the other eye is covered.
Increasing Astigmatism
The spectacle cylinder may:
- Increase
- Change axis
- Become difficult to refine
- Differ substantially between measurements
Increasing Short-Sightedness
The steepening cornea may shift the prescription towards greater myopia.
Glare and Halos
Patients may notice:
- Halos around headlights
- Starbursts
- Smearing around signs
- Reduced night-driving confidence
- Difficulty in rain or low light
Light Sensitivity
Bright sunlight and artificial lights may become uncomfortable.
Frequent Prescription Changes
Repeated spectacle changes over a short period may be an early clue, particularly in a child or young adult.
Poor Vision With Glasses but Better Vision Through a Pinhole
The pinhole temporarily blocks some irregular light rays and may improve vision.
This suggests that optical irregularity is contributing, although it does not establish the diagnosis.
Does Keratoconus Affect Both Eyes?
Keratoconus is generally considered a bilateral condition, but the two eyes are often highly asymmetrical.
One eye may have:
- Clear clinical keratoconus
while the other shows:
- Mild tomography changes
- Forme-fruste or subclinical disease
- No definite abnormality on the first examination
The apparently better eye still requires monitoring.
Does Keratoconus Always Progress?
No
Some corneas remain stable for many years.
Others progress over a relatively short period.
The course cannot be predicted from age alone.
Who Is More Likely to Progress?
Progression is generally more concerning in:
- Children
- Teenagers
- Young adults
- Patients with documented recent changes
- Steeper corneas
- Patients with persistent eye rubbing
- Patients with poorly controlled allergy
- Eyes with significant asymmetry
Paediatric keratoconus can progress rapidly and may present at a more advanced stage than adult disease.
Can Keratoconus Progress After Age 40?
Yes.
Progression becomes less common with increasing age but does not become impossible.
Monitoring may remain necessary when:
- Scans are changing.
- Vision or prescription is deteriorating.
- Eye rubbing continues.
- Pregnancy or hormonal change is occurring.
- The cornea remains biomechanically vulnerable.
- Previous cross-linking appears to have lost effect.
How Is Progression Defined?
There is no single measurement that proves progression in every eye.
The ophthalmologist may look for consistent change in:
- Maximum corneal curvature
- Anterior corneal steepening
- Posterior corneal elevation
- Thinnest corneal measurement
- Location of the thinnest point
- Manifest refraction
- Corrected vision
- ABCD progression parameters
- Higher-order aberrations
- Contact-lens fit
A small isolated change may represent:
- Measurement variability
- Dry eye
- Contact-lens warpage
- Poor fixation
- Differences between devices
Progression should usually be confirmed using repeatable measurements and the overall pattern of change.
Keratoconus in Children
Why Is Childhood Disease Important?
Children may:
- Progress more rapidly
- Present with more advanced disease
- Rub their eyes frequently
- Have significant allergy
- Fail to report visual symptoms
- Depend on one better eye without realising the other is worsening
Possible Warning Signs
Parents may notice that a child:
- Sits very close to screens
- Squints
- Rubs the eyes
- Has rapidly changing astigmatism
- Sees poorly despite new glasses
- Covers one eye
- Struggles with night vision
- Performs worse on monocular vision testing
Should Children With a Family History Be Screened?
Corneal imaging should be considered in children or adolescents with:
- A parent or sibling with keratoconus
- Increasing astigmatism
- Reduced corrected vision
- Significant eye rubbing
- Vernal or severe allergic eye disease
Early detection provides an opportunity to intervene before advanced thinning or scarring develops.
Is Cross-Linking Used in Children?
Yes.
Cross-linking may be recommended when progression is documented or when the risk of rapid progression is judged to be high.
Long-term studies show that cross-linking can stabilise many paediatric eyes, although children may have a greater lifetime risk of further progression and may require prolonged monitoring or occasional retreatment.
How Is Keratoconus Diagnosed?
Symptom and Prescription History
The clinician may ask about:
- Frequent spectacle changes
- Eye rubbing
- Allergy
- Family history
- Poor night vision
- Contact-lens wear
- Previous laser eye surgery
- Unequal vision
- Previous scans
Refraction
Refraction may demonstrate:
- Myopia
- Increasing astigmatism
- Irregular or unstable cylinder
- Reduced best-corrected vision
- A scissoring reflex during retinoscopy
Slit-Lamp Examination
Clinical signs may include:
- Corneal thinning
- Conical protrusion
- Fleischer ring
- Vogt striae
- Apical scarring
- Prominent corneal nerves
- Munson sign in advanced disease
Early keratoconus may have no obvious slit-lamp signs.
Keratometry
Keratometry measures the curvature of the central anterior cornea.
It may identify steep or irregular readings but does not provide a complete assessment of early disease.
Corneal Topography
Topography maps the anterior corneal surface.
It may demonstrate:
- Inferior or inferotemporal steepening
- Asymmetrical bow-tie patterns
- Skewed radial axes
- Irregular astigmatism
- Localised cone patterns
Corneal Tomography
Tomography evaluates both the front and back surfaces of the cornea and constructs a three-dimensional corneal model.
It may measure:
- Anterior elevation
- Posterior elevation
- Corneal thickness distribution
- Thinnest point
- Rate of thickness progression
- Belin–Ambrósio indices
- ABCD staging parameters
Tomography has improved the detection of early or subclinical keratoconus and is essential when refractive surgery is being considered.
Pachymetry
Pachymetry measures corneal thickness.
The thinnest point in keratoconus is commonly displaced away from the central geometric point.
Thickness alone cannot diagnose keratoconus because some normal corneas are thin and some keratoconic corneas are not extremely thin.
Epithelial Thickness Mapping
The epithelium may partially mask stromal irregularity by becoming:
- Thinner over the cone
- Thicker around it
Epithelial OCT mapping may help identify early ectatic patterns or distinguish true keratoconus from some topographic abnormalities.
Corneal Biomechanical Assessment
Devices such as the Corvis ST or Ocular Response Analyzer assess aspects of corneal deformation.
Biomechanical indices may support:
- Early detection
- Refractive-surgery screening
- Differentiation from normal corneas
- Assessment of ectasia risk
They are adjuncts rather than replacements for tomography and clinical evaluation.
Staging Keratoconus
Amsler–Krumeich Classification
The traditional Amsler–Krumeich classification considers:
- Refraction
- Keratometry
- Corneal thickness
- Scarring
It remains familiar but does not fully represent modern tomography.
ABCD Classification
The ABCD system evaluates:
- A: Anterior radius of curvature
- B: Posterior radius of curvature
- C: Thinnest corneal thickness
- D: Distance visual acuity
It can help document disease stage and monitor progression.
Staging Does Not Decide Treatment by Itself
Treatment should also consider:
- Age
- Documented progression
- Visual needs
- Contact-lens tolerance
- Scarring
- Corneal thickness
- Cone location
- Pregnancy plans
- Risk of eye rubbing
Conditions That Can Resemble Keratoconus
Pellucid Marginal Degeneration
Pellucid marginal degeneration typically causes:
- Inferior peripheral thinning
- Steepening above the thinned area
- A crab-claw or kissing-dove topographic pattern
It can overlap with keratoconus and may require similar management, although treatment planning differs.
Post-LASIK or Post-PRK Ectasia
Corneal ectasia can occur after refractive surgery when the cornea becomes structurally unstable.
The previous surgical history helps distinguish it from primary keratoconus.
Contact-Lens Warpage
Rigid or poorly fitting contact lenses may temporarily alter corneal shape.
Lenses may need to be discontinued before reliable tomography is performed.
Irregular Corneal Scarring
Scarring from infection, trauma or previous surgery can produce irregular topography without true progressive ectasia.
Terrien Marginal Degeneration
Terrien degeneration generally causes peripheral thinning with a different clinical pattern.
Treatment Goals
Stabilisation and Vision Correction Are Different
Cross-linking aims mainly to prevent further progression.
Glasses and contact lenses aim to improve the way the patient sees.
A patient may therefore require both:
- Cross-linking for stability
- Contact lenses for visual rehabilitation
Treatment Should Be Individualised
The most appropriate plan depends on:
- Age
- Progression
- Corneal thickness
- Cone location
- Corneal scarring
- Vision with glasses
- Contact-lens tolerance
- Occupation
- Lifestyle
- Access to follow-up
Stop Eye Rubbing
Why This Matters
Avoiding eye rubbing is one of the most important non-surgical measures.
Treat the Cause of Itching
Management may include:
- Anti-allergy eyedrops
- Preservative-free lubricants
- Cold compresses
- Blepharitis treatment
- Environmental allergen reduction
- Specialist allergy or dermatology care
A Safer Response to Itching
Instead of rubbing:
- Close the eye gently.
- Apply a cold compress.
- Use prescribed allergy treatment.
- Blink several times.
- Seek review if itching remains uncontrolled.
Glasses
When Can Glasses Work Well?
Glasses may provide useful vision in:
- Early keratoconus
- Mild regular astigmatism
- Stable disease
- Patients who tolerate some residual distortion
Limitations
As irregular astigmatism increases, spectacles may no longer produce sharp vision.
The two eyes may also require very different prescriptions, creating image-size imbalance.
Soft Contact Lenses
Standard Soft Lenses
Ordinary soft lenses may work for mild disease but usually follow the irregular corneal surface and may not neutralise advanced distortion.
Custom Keratoconus Soft Lenses
Thicker or specially designed soft lenses may mask some irregularity while providing better comfort than a rigid lens.
They may not produce the same optical quality as a well-fitted rigid or scleral lens in more advanced disease.
Rigid Gas-Permeable Contact Lenses
How Do They Improve Vision?
A rigid lens creates a regular front optical surface.
The tear layer between the lens and cornea helps neutralise irregular astigmatism.
Possible Benefits
- Sharper vision than glasses
- Improved contrast
- Reduced ghosting
- Customised fitting
- Good oxygen transmission
Possible Difficulties
- Initial discomfort
- Lens displacement
- Dust entering beneath the lens
- Limited wearing time
- Corneal staining
- Difficulty fitting a highly irregular cone
Contact lenses improve vision but do not reliably stop keratoconus progression.
Hybrid Contact Lenses
Hybrid lenses combine:
- A rigid central optical zone
- A soft surrounding skirt
They aim to provide rigid-lens vision with greater comfort and stability.
Possible problems include:
- Tight fit
- Removal difficulty
- Limited tear exchange
- Cost
- Lens replacement requirements
Scleral Contact Lenses
What Is a Scleral Lens?
A scleral lens is a large rigid lens that rests on the white part of the eye and vaults over the cornea.
The space beneath the lens is filled with sterile preservative-free saline.
Benefits
Scleral lenses may provide:
- Excellent correction of irregular astigmatism
- Greater stability
- Improved comfort
- Protection of the corneal surface
- Better vision in advanced keratoconus
Recent evidence supports sustained improvement in visual acuity and quality of life for many keratoconus patients using scleral lenses.
Possible Difficulties
- Handling and insertion
- Removal
- Midday fogging
- Cost
- Long fitting process
- Reduced oxygen transmission if poorly fitted
- Need for specialised solutions
Can Tap Water Be Used?
No.
Only the recommended sterile preservative-free solution should be used to fill the lens.
Contact lenses should never be rinsed or stored using tap water because of the risk of serious infection.
Corneal Collagen Cross-Linking
What Is Cross-Linking?
Corneal collagen cross-linking, or CXL, uses:
- Riboflavin, which is vitamin B2
- Controlled ultraviolet-A light
The photochemical reaction creates additional bonds within the corneal stroma and increases its biomechanical stability.
What Is the Main Purpose?
The principal goal is to:
- Slow or stop progression
- Reduce the likelihood of advanced ectasia
- Reduce the future need for transplantation
Cross-linking is not primarily a laser vision-correction procedure.
Some patients experience modest corneal flattening or improved vision, but these improvements cannot be guaranteed.
Who Should Be Considered?
CXL is commonly considered for:
- Documented progressive keratoconus
- Young patients at high risk of progression
- Progressive post-refractive-surgery ectasia
- Selected paediatric cases
- Patients showing repeatable tomographic deterioration
Does Every Stable Adult Need Cross-Linking?
Not necessarily.
Observation may be appropriate when:
- The cornea is stable on serial imaging.
- The patient is older.
- Vision and refraction are stable.
- There are no major high-risk features.
- Follow-up is reliable.
The potential benefit should be balanced against treatment risks.
Epithelium-Off Cross-Linking
What Happens?
In conventional epithelium-off CXL:
- Numbing drops are applied.
- The central corneal epithelium is removed.
- Riboflavin drops are applied.
- Corneal thickness is checked.
- Ultraviolet-A light is delivered.
- A bandage contact lens is placed.
- Antibiotic and anti-inflammatory drops are prescribed.
Why Is the Epithelium Removed?
The epithelium limits riboflavin penetration into the stroma.
Removing it allows more reliable stromal riboflavin absorption.
Evidence
Epithelium-off cross-linking has the most established long-term evidence.
Studies and reviews report stability extending beyond ten years in many treated eyes, although no treatment prevents progression in every patient.
Accelerated Cross-Linking
What Does Accelerated Mean?
Accelerated protocols use:
- Higher ultraviolet intensity
- Shorter exposure duration
The total delivered energy may be similar, but the biological effect is not necessarily identical to the conventional protocol.
Many accelerated protocols have shown good safety and stabilisation, although results depend on:
- Treatment intensity
- Oxygen availability
- Corneal thickness
- Treatment duration
- Patient age
Epithelium-On Cross-Linking
What Is It?
Epithelium-on, or transepithelial, cross-linking leaves the corneal epithelium substantially intact.
Potential advantages include:
- Less early pain
- Faster surface recovery
- Lower infection risk
- Reduced haze
- Earlier return to normal activity
Does It Work as Well?
Transepithelial techniques differ considerably in:
- Riboflavin formulation
- Oxygen supplementation
- Electrical delivery
- Ultraviolet pattern
- Treatment time
Older transepithelial protocols often produced a shallower or less predictable effect than conventional epithelium-off treatment.
In October 2025, the US FDA approved a specific oxygen-assisted epithelium-on cross-linking system for keratoconus in patients aged 13 years and older. This approval applies to that particular treatment system and should not be interpreted as proof that all “epi-on” protocols are equivalent. Availability and approval differ between countries.
Cross-Linking in Thin Corneas
Conventional treatment has minimum thickness requirements to protect the corneal endothelium.
Selected thin corneas may be treated using modified techniques involving:
- Hypo-osmolar riboflavin
- Contact-lens-assisted cross-linking
- Individualised irradiation
- Sub400 protocols
- Other specialist modifications
These cases require careful selection because very thin corneas may have:
- Greater treatment risk
- Less predictable effect
- Advanced disease
- Reduced visual potential
Recovery After Cross-Linking
The First Few Days
After epithelium-off treatment, patients may experience:
- Pain
- Grittiness
- Watering
- Light sensitivity
- Redness
- Blurred vision
The epithelium usually heals over several days.
The First Few Weeks
Vision may fluctuate because of:
- Surface healing
- Corneal haze
- Tear-film instability
- Changing corneal curvature
The First Several Months
The cornea continues to remodel.
Spectacle or contact-lens measurements may need to be delayed until the surface and shape are sufficiently stable.
Contact Lenses
Rigid or scleral lenses are generally resumed only after the treating specialist confirms that epithelial healing and corneal stability are adequate.
Risks of Cross-Linking
Possible risks include:
- Pain
- Delayed epithelial healing
- Infection
- Corneal haze
- Scarring
- Reduced corrected vision
- Sterile infiltrates
- Herpes reactivation
- Endothelial damage
- Continued progression
- Need for repeat treatment
Serious complications are uncommon when appropriate protocols and patient selection are used, but CXL is not risk-free.
Can Keratoconus Progress After Cross-Linking?
Yes.
Possible reasons include:
- Aggressive disease
- Young age
- Very steep preoperative cornea
- Continued eye rubbing
- Inadequate treatment depth
- Long-term loss of treatment effect
- Measurement variability mistaken for progression
Patients require continued tomography after treatment.
Repeat cross-linking may be considered when convincing progression is demonstrated and the cornea remains suitable.
Intrastromal Corneal Ring Segments
What Are They?
Intrastromal corneal ring segments are small curved implants placed within channels in the corneal stroma.
They are sometimes called:
- ICRS
- Corneal ring segments
- Intracorneal rings
What Do They Do?
Ring segments may:
- Flatten part of the cornea
- Reduce irregularity
- Improve spectacle-corrected vision
- Improve contact-lens tolerance
- Delay or reduce the need for transplantation
They do not reliably stop progression and may be combined with cross-linking.
Who May Benefit?
Possible candidates include patients with:
- Moderate keratoconus
- Clear central cornea
- Contact-lens intolerance
- Suitable corneal thickness
- A cone pattern that matches an available segment design
Risks
Possible complications include:
- Infection
- Segment extrusion
- Migration
- Corneal melting
- Glare
- Halos
- Poor visual result
- Need for removal
Corneal Allogenic Intrastromal Ring Segments
What Are CAIRS?
Corneal allogenic intrastromal ring segments, or CAIRS, use donor corneal tissue rather than a synthetic plastic segment.
The tissue is implanted within channels created in the patient’s cornea.
Possible Advantages
Proposed advantages include:
- Greater biocompatibility
- Customisable segment dimensions
- Ability to treat selected thin or irregular corneas
- Reduced risk of synthetic-segment extrusion
Recent reviews and meta-analyses report promising improvements in corneal shape and vision, but CAIRS is an evolving treatment with less long-term evidence than established cross-linking or corneal transplantation.
Topography-Guided Surface Laser With Cross-Linking
What Is the Aim?
Selected centres combine limited topography-guided surface laser treatment with cross-linking.
The purpose is to:
- Regularise the corneal surface
- Reduce higher-order aberrations
- Improve corrected vision
- Stabilise the remaining cornea
Is This the Same as Ordinary LASIK?
No.
LASIK removes stromal tissue and creates a flap, which is generally inappropriate in keratoconus because it may further weaken the cornea.
Any therapeutic laser treatment in keratoconus must be:
- Conservative
- Surface-based
- Carefully calculated
- Combined with biomechanical stabilisation
- Performed only in selected corneas
It is not suitable for very thin or advanced disease.
Can a Patient With Keratoconus Have LASIK?
Ordinary LASIK is generally contraindicated in established keratoconus.
Removing corneal tissue may:
- Further weaken the cornea
- Accelerate ectasia
- Produce unpredictable vision
- Make future treatment more difficult
Patients with suspicious tomography should not undergo routine laser refractive surgery until the risk has been carefully evaluated.
Implantable Collamer Lens and Keratoconus
An implantable lens can correct:
- Myopia
- Regular astigmatism
It does not correct all irregular corneal aberrations and does not stabilise progressive keratoconus.
An implantable lens may be considered only in carefully selected patients with:
- Stable disease
- Adequate vision with a spectacle-type correction
- Suitable anterior-chamber anatomy
- No evidence of ongoing progression
Cross-linking may be required first.
Corneal Transplantation
When Is a Transplant Considered?
Corneal transplantation may be considered when:
- Useful vision cannot be achieved with contact lenses.
- Contact lenses cannot be tolerated.
- Central corneal scarring is present.
- The cornea is extremely thin or irregular.
- Previous treatments have not provided adequate function.
- Acute hydrops has caused visually significant scarring.
Only a minority of modern keratoconus patients require transplantation when disease is detected and stabilised early.
Deep Anterior Lamellar Keratoplasty
What Is DALK?
Deep anterior lamellar keratoplasty replaces the diseased corneal stroma while preserving the patient’s own:
- Descemet’s membrane
- Corneal endothelium
Advantages
Potential advantages include:
- No endothelial rejection
- Better long-term preservation of endothelial cells
- Lower risk from intraocular entry
- Greater structural integrity after some forms of trauma
Limitations
DALK can be technically demanding and may result in:
- Interface haze
- Residual stromal tissue
- Irregular astigmatism
- Conversion to full-thickness transplantation if Descemet’s membrane is perforated
Penetrating Keratoplasty
What Is It?
Penetrating keratoplasty replaces the full thickness of the central cornea.
When May It Be Preferred?
It may be considered when:
- Scarring extends deeply to Descemet’s membrane.
- Previous hydrops has caused significant posterior scarring.
- DALK is not technically achievable.
- A previous lamellar procedure has failed.
- Full-thickness disease is present.
DALK Versus Penetrating Keratoplasty
Both procedures can provide useful visual rehabilitation.
Large modern analyses suggest that DALK offers better endothelial preservation and fewer rejection-related complications, while penetrating keratoplasty may have advantages in selected advanced corneas and can sometimes provide a clearer interface. The choice depends on the depth of scarring, surgeon experience and individual anatomy.
Recovery After Corneal Transplantation
Visual recovery may take:
- Many months
- More than one year
- Longer while sutures are adjusted or removed
Patients may still require:
- Glasses
- Rigid contact lenses
- Scleral lenses
- Astigmatism treatment
- Cataract surgery
- Further corneal procedures
A transplant replaces the abnormal corneal tissue but does not guarantee freedom from visual correction.
Acute Corneal Hydrops
What Is Acute Hydrops?
Acute corneal hydrops occurs when Descemet’s membrane tears and fluid from inside the eye enters the corneal stroma.
It causes sudden:
- Severe corneal swelling
- Cloudy or white corneal appearance
- Marked visual loss
- Light sensitivity
- Pain or discomfort
- Watering
Is It an Emergency?
Yes.
Sudden corneal clouding in a patient with keratoconus requires urgent ophthalmic assessment.
The main immediate concerns include:
- Confirming the diagnosis
- Excluding infection
- Controlling pain
- Limiting complications
- Monitoring for corneal perforation
Treatment
Treatment may include:
- Hypertonic saline
- Cycloplegic drops
- Pressure-lowering medication
- Lubrication
- Protective measures
- Intracameral air or gas
- Compression sutures
- Other specialist procedures
Hydrops may eventually resolve, but it often leaves a corneal scar. Modern procedures may shorten recovery in selected severe cases.
Pregnancy and Keratoconus
Hormonal and biomechanical changes during pregnancy may affect the cornea.
Patients with known keratoconus should report:
- Rapidly changing vision
- Increasing astigmatism
- Reduced contact-lens tolerance
- New distortion
Elective cross-linking is generally avoided during pregnancy, and treatment timing should be discussed before conception when progression is known or strongly suspected.
Cataract Surgery and Keratoconus
Why Is Planning More Difficult?
Keratoconus affects:
- Corneal curvature measurements
- Astigmatism
- Intraocular-lens calculations
- Prediction of the postoperative prescription
Stable Disease Is Important
Corneal progression should be assessed before cataract surgery, especially in younger patients.
Unstable keratoconus may continue changing after the cataract has been removed.
Contact Lenses Must Be Removed Before Measurements
Rigid or scleral lenses can temporarily alter corneal shape.
They may need to be discontinued for a suitable period before:
- Keratometry
- Tomography
- Biometry
- Toric-lens planning
The required period varies according to lens type and corneal response.
Which Intraocular Lens Is Suitable?
A monofocal lens is commonly preferred when significant irregularity is present.
A toric lens may be considered when:
- The astigmatism has a sufficiently regular component.
- Measurements are repeatable.
- The cornea is stable.
- The patient obtains useful spectacle-corrected vision.
- Expectations are realistic.
Multifocal or trifocal lenses generally require caution because keratoconus already causes:
- Higher-order aberrations
- Glare
- Reduced contrast
- Irregular astigmatism
Can Glasses Still Be Used After Cross-Linking or Surgery?
Yes.
Cross-linking does not prevent the use of:
- Glasses
- Soft contact lenses
- Rigid lenses
- Hybrid lenses
- Scleral lenses
The prescription may change as the cornea remodels.
Driving With Keratoconus
Driving ability depends on more than ordinary daytime visual acuity.
Patients may struggle with:
- Night glare
- Halos
- Ghosting
- Rain
- Oncoming headlights
- Road-sign recognition
- Reduced contrast
A patient may meet the legal visual-acuity requirement but still feel unsafe at night.
Driving should be avoided when vision is not adequate for the conditions.
Common Myths
“Keratoconus Is Just Astigmatism”
False.
Keratoconus causes progressive corneal thinning and irregularity.
“A Stronger Pair of Glasses Will Always Fix It”
False.
Spectacles cannot fully correct advanced irregular astigmatism.
“Contact Lenses Stop Progression”
False.
They improve vision but do not reliably strengthen the cornea.
“Cross-Linking Makes Vision Perfect”
False.
Its primary purpose is stabilisation.
“Cross-Linking Is Needed Only When Vision Is Very Poor”
False.
The greatest value may come from stabilising the cornea before advanced damage and scarring develop.
“Keratoconus Always Leads to a Corneal Transplant”
False.
Many patients are successfully managed with cross-linking and contact lenses.
“Rubbing Is Harmless if the Eye Is Closed”
False.
Pressure transmitted through the eyelid can still affect the cornea.
“LASIK Can Correct Keratoconus”
False.
Ordinary LASIK may worsen corneal instability.
Frequently Asked Questions
Is Keratoconus Hereditary?
Genetic susceptibility is important, but inheritance is usually complex.
A family history increases risk without guaranteeing that a relative will develop the disease.
Should My Children Be Screened?
Screening is sensible when a parent or sibling has keratoconus, particularly if the child has:
- Astigmatism
- Allergy
- Eye rubbing
- Reduced corrected vision
Can Keratoconus Develop in Only One Eye?
The disease may appear unilateral clinically, but subtle abnormalities may later be detected in the other eye.
How Often Should Tomography Be Repeated?
The interval depends on:
- Age
- Disease severity
- Recent change
- Previous cross-linking
- Symptoms
- Eye-rubbing behaviour
Children or progressing patients may require scans every few months, while stable older adults may be reviewed less frequently.
What Is Forme-Fruste Keratoconus?
This term is used for subtle or incomplete keratoconus, often detected through corneal imaging before obvious clinical signs appear.
Can Keratoconus Stabilise Naturally?
Yes.
Some patients become stable without treatment, particularly later in adulthood.
The difficulty is predicting which young corneas will progress.
Can Cross-Linking Be Repeated?
Yes, in selected cases with convincing post-treatment progression and adequate corneal safety parameters.
Will Cross-Linking Remove the Need for Contact Lenses?
Not necessarily.
Many patients continue to need rigid or scleral lenses for best vision.
Is Cross-Linking Painful?
Epithelium-off treatment commonly causes moderate discomfort for the first few days.
Pain is generally lower with epithelium-on treatment, but efficacy depends on the specific protocol.
How Long Does Cross-Linking Last?
Long-term studies show stability beyond ten years in many patients.
Lifelong stability cannot be guaranteed, particularly in young or advanced cases.
Can I Exercise After Cross-Linking?
Avoid swimming, dusty environments, eye rubbing and activities that risk eye trauma until the epithelial surface has healed and the surgeon permits resumption.
Can Keratoconus Return After a Corneal Transplant?
True recurrence within the graft is uncommon but has been reported many years later.
Vision can also change because of:
- Graft astigmatism
- Suture changes
- Graft rejection
- Cataract
- Other eye disease
Are Scleral Lenses Safe?
They can be very effective when professionally fitted and correctly handled.
Poor hygiene, water exposure or inappropriate wear may cause serious complications.
Can Keratoconus Cause a Sudden White Cornea?
Yes.
Acute hydrops may cause sudden severe swelling and clouding.
Infection can also cause a white corneal spot, so urgent assessment is necessary.
When to Seek Urgent Eye Care
Arrange urgent same-day ophthalmic assessment for:
- Sudden severe reduction in vision
- Sudden corneal clouding
- A new white or grey corneal area
- Significant pain
- Increasing redness
- Marked light sensitivity
- Discharge
- A painful red eye while wearing contact lenses
- Trauma to a thin or transplanted cornea
- Sudden symptoms after cross-linking or corneal surgery
These symptoms may indicate:
- Acute corneal hydrops
- Corneal infection
- Corneal abrasion
- Graft rejection
- Postoperative complication
- Rare corneal perforation
A Keratoconus Monitoring Checklist
Symptoms to Track
- Blurred vision
- Increasing distortion
- Ghosting
- Night glare
- Changing prescription
- Reduced contact-lens comfort
- Sudden clouding
Risk Factors to Address
- Eye rubbing
- Allergy
- Dry eye
- Blepharitis
- Poor contact-lens hygiene
- Missed follow-up
Tests That May Be Used
- Refraction
- Keratometry
- Corneal topography
- Corneal tomography
- Pachymetry
- Epithelial mapping
- Corneal biomechanics
- Slit-lamp examination
- Visual acuity
Questions to Ask
- Is the keratoconus progressing?
- How reliable are the scan changes?
- Am I a candidate for cross-linking?
- Which CXL protocol is recommended?
- Is the cornea thick enough?
- Should my family members be screened?
- Which contact lens is most appropriate?
- Would a ring procedure help?
- Is there significant corneal scarring?
- Could I eventually require a transplant?
- Is the other eye affected?
- How often should I be reviewed?
The Bottom Line
Keratoconus is a condition in which the cornea becomes thinner, steeper and irregularly shaped.
It commonly causes:
- Blurred vision
- Irregular astigmatism
- Ghosting
- Glare
- Halos
- Poor night vision
- Frequent prescription changes
The condition often begins during adolescence or early adulthood and usually affects both eyes unevenly.
Important risk factors and associations include:
- Family history
- Eye rubbing
- Allergy
- Younger age
- Certain systemic or developmental conditions
Diagnosis requires more than a glasses test.
Modern evaluation may include:
- Corneal topography
- Corneal tomography
- Pachymetry
- Epithelial mapping
- Biomechanical assessment
Treatment has two separate goals.
To stabilise progressive disease:
- Avoid eye rubbing.
- Treat allergy.
- Consider corneal collagen cross-linking.
To improve vision:
- Glasses may help early disease.
- Rigid, hybrid or scleral contact lenses can correct irregular astigmatism.
- Intrastromal ring procedures may improve corneal shape in selected patients.
- Corneal transplantation may be required for severe scarring or contact-lens intolerance.
Cross-linking has transformed keratoconus care by allowing many progressive corneas to be stabilised before advanced visual loss develops.
The most important principles are:
Detect the disease early.
Do not rub the eyes.
Monitor for progression.
Stabilise the cornea before irreversible thinning and scarring occur.
References
- Singh RB, Koh S, Sharma N, et al. Keratoconus. Nat Rev Dis Primers. 2024;10. doi:10.1038/s41572-024-00565-3. PMID: 39448666.
- Jhanji V, et al. Corneal ectasia Preferred Practice Pattern®. Ophthalmology. 2024;131. doi:10.1016/j.ophtha.2024.01.010.
- Sriranganathan A, Chan CC, Dhillon J, Felfeli T. Global incidence and prevalence of keratoconus: a systematic review and meta-analysis. Cornea. 2025. doi:10.1097/ICO.0000000000003973. PMID: 40833011.
- Santodomingo-Rubido J, Carracedo G, Suzaki A, et al. Keratoconus: an updated review. Cont Lens Anterior Eye. 2022;45(3):101559. PMID: 34991971.
- Seth I, Bulloch G, Vine M, et al. The association between keratoconus and allergic eye diseases, eye rubbing, and atopy: a systematic review and meta-analysis. Clin Exp Ophthalmol. 2023;51. PMID: 36882200.
- Hashemi H, Heydarian S, Hooshmand E, et al. The prevalence and risk factors for keratoconus: a systematic review and meta-analysis. Cornea. 2020;39(2):263–270. PMID: 31498247.
- Cehelyk EK, Syed ZA. Long-term outcomes of corneal crosslinking. Curr Opin Ophthalmol. 2024;35(4):315–321. doi:10.1097/ICU.0000000000001054. PMID: 38700950.
- Greenstein SA, Fry KL, Hersh PS. Long-term outcomes after corneal cross-linking for keratoconus and corneal ectasia. Eye Contact Lens. 2023. PMID: 37565471.
- Caruso C, et al. Corneal collagen cross-linking in patients with keratoconus: up-to-date. J Clin Med. 2024. PMID: 38766341.
- Gupta Y, et al. Pediatric keratoconus. Curr Opin Ophthalmol. 2025. PMID: 39396644.
- Ahmet S, et al. Long-term results of accelerated corneal collagen cross-linking in paediatric keratoconus. Eye. 2024. PMID: 38609652.
- Mushtaq A, et al. Long-term effectiveness of scleral-lens treatment in keratoconus. Eye Contact Lens. 2025. PMID: 39781287.
- Friedrich M, et al. Visual and topographic outcomes after corneal allogeneic intrastromal ring-segment implantation: a systematic review and meta-analysis. Cornea. 2025. PMID: 40157443.
- Awad AA, et al. Deep anterior lamellar keratoplasty versus penetrating keratoplasty for keratoconus: a systematic review and meta-analysis of 27,018 eyes. Am J Ophthalmol. 2025. PMID: 39943883.
- Bafna RK, Kalra N, Asif MI, et al. Management of acute corneal hydrops: current perspectives. Indian J Ophthalmol. 2024;72(4):495–507. doi:10.4103/IJO.IJO_2160_23. PMID: 38317314.
- U.S. Food and Drug Administration. Epioxa and Epioxa HD prescribing information. FDA; 2025.
