Implantable Collamer Lens (ICL): Suitability, Procedure, Risks and Recovery

Author: Dr Val Phua
Estimated reading time: 22 minutesd to reduce dependence on spectacles or contact lenses.

It is sometimes called an “implantable contact lens”. However, the formal name is Implantable Collamer Lens because the lens is made from a proprietary collagen-containing copolymer known as Collamer.

Unlike an ordinary contact lens, an ICL is placed inside the eye.

Unlike cataract surgery or refractive lens exchange, the natural lens is not removed.

During ICL surgery:

A small incision is made at the edge of the cornea.
The flexible ICL is inserted into the eye.
The lens unfolds behind the iris.
It is positioned in front of the natural crystalline lens.
The corneal incision usually seals without stitches.

ICL surgery is principally used to correct:

Myopia, or short-sightedness
Myopic astigmatism using a toric ICL
Selected low, moderate or high myopic prescriptions

ICL surgery was historically associated mainly with very high myopia or corneas unsuitable for LASIK. Contemporary evidence shows that central-port ICLs can also provide effective and predictable correction for selected patients with low-to-moderate myopia. The decision should nevertheless be based on the individual eye rather than the spectacle prescription alone. es include:

No removal of corneal stromal tissue
Treatment of higher myopic prescriptions
Preservation of the natural corneal shape
Good optical quality
Correction of astigmatism with a toric lens
Rapid visual recovery
Removal or exchange of the lens when medically necessary

However, ICL implantation is intraocular surgery.

Possible complications include:

Raised eye pressure
Inflammation
Infection
Incorrect lens sizing
Excessively low or high vault
Cataract formation
Corneal endothelial cell loss
Toric lens rotation
Residual refractive error
Glare or halos
Rare loss of vision

Careful sizing, precise surgery and long-term monitoring are therefore essential.

The Quick Answer

What Is an ICL?

An ICL is a thin, flexible phakic intraocular lens.

“Phakic” means that the natural crystalline lens remains inside the eye.

The ICL is positioned:

Behind the coloured iris
In front of the natural lens
With its supporting footplates resting in the ciliary sulcus region

The patient does not normally see or feel the lens once it is in place.

What Does ICL Surgery Correct?

ICL surgery is most commonly used to correct:

Myopia
Hyperopia
Astigmatism
Presbyopia

It does not directly treat:

Cataract
Keratoconus
Retinal disease
Glaucoma
Amblyopia

Is ICL Surgery Painful?

Most patients experience little or no pain during surgery.

Anaesthetic eye drops are commonly used.

Some patients also receive:

Mild intravenous sedation
Intracameral anaesthetic
Regional anaesthesia
General anaesthesia in unusual circumstances

The patient may notice:

Bright lights
Gentle pressure
Cool fluid
Movement or blurred shapes

Sharp pain is not expected and should be reported immediately.

How Long Does the Procedure Take?

The surgical portion commonly takes approximately 10 to 30 minutes per eye in an uncomplicated case.

Additional time is required for:

Registration
Pupil dilation
Preparation
Anaesthesia
Postoperative monitoring
Eye-pressure checks
Discharge instructions

How Quickly Does Vision Recover?

Many patients notice substantial improvement within one day.

Vision commonly continues improving over:

Several days
Several weeks
Occasionally several months

Temporary blur may be caused by:

Pupil dilation
Corneal swelling
Inflammation
Dry eye
Residual refractive error
Adaptation to the new optical system

Is the ICL Permanent?

The lens is designed to remain inside the eye long term.

It does not need routine replacement after a fixed number of years.

However, the ICL may be removed or exchanged if:

The vault is unsuitable
The lens rotates
The prescription changes significantly
Cataract develops
Eye pressure becomes problematic
Another intraocular procedure is required

Is ICL Surgery Reversible?

The ICL can usually be surgically removed.

This is more accurately described as removable rather than completely reversible.

Removal does not guarantee that the eye returns perfectly to its preoperative state because:

An incision has been made.
The eye has undergone intraocular surgery.
Endothelial cells may have been lost.
Inflammation or another complication may have occurred.
The natural prescription may have changed with age.

Will I Never Need Spectacles Again?

Not necessarily.

Spectacles may still be useful for:

Fine distance vision
Night driving
Residual astigmatism
Reading after presbyopia develops
Computer work
Future prescription changes
Cataract-related refractive changes

The aim is to reduce dependence on spectacles or contact lenses, not to guarantee that they will never be required again.

What Is Collamer?

Collamer is a collagen-containing polymer used to manufacture the ICL.

The lens is:

Soft
Foldable
Biocompatible
Designed for placement inside the eye
Available in different powers and sizes

Its flexibility allows the lens to be inserted through a small corneal incision.

Where Is the ICL Positioned?

The ICL is placed in the posterior chamber of the eye.

This means it lies:

Behind the iris
In front of the natural crystalline lens
With its footplates positioned in the ciliary sulcus region

It should not be confused with an anterior-chamber phakic lens positioned in front of the iris.

What Is the Central Port?

Modern EVO-type ICLs have a small opening in the centre of the lens.

This central port allows aqueous fluid to move from behind the iris towards the front of the eye.

The design helps maintain aqueous circulation around the natural crystalline lens and usually removes the need for a preoperative peripheral iridotomy that was commonly required with earlier ICL models. Reviews of central-port ICL studies report high refractive predictability and a favourable safety profile when patients are selected and monitored appropriately. al Port Affect Vision?

The central opening is very small.

Most patients do not consciously see it.

Some may experience:

Halos
Rings around lights
Glare
Light scatter

These symptoms may be influenced by:

The central port
Pupil size
Residual refractive error
Dry eye
Natural lens reflections
The optical interaction between the ICL and the eye

Symptoms often become less noticeable with time, but they may persist in some patients.

Who May Be Suitable for ICL Surgery?

A suitable candidate generally has:

Myopia or myopic astigmatism within an available treatment range
A stable spectacle prescription
Adequate anterior-chamber depth
Adequate corneal endothelial cell density
Suitable internal eye dimensions
A healthy natural crystalline lens
No uncontrolled glaucoma
No active eye inflammation
No visually significant cataract
Realistic expectations
The ability to attend long-term follow-up

Regulatory indications, available lens powers and age ranges vary between countries and lens models. In the United States, FDA indications for EVO/EVO+ ICLs were expanded in November 2025 from ages 21–45 to ages 21–60, illustrating that approved ranges can change and should not be treated as universal rules. t the Prescription Be?

The prescription should generally remain stable for at least approximately one year.

Significant ongoing change increases the risk that residual myopia develops after surgery.

Instability may occur with:

Younger age
Progressive myopia
Pregnancy
Breastfeeding
Poorly controlled diabetes
Hormonal change
Developing cataract
Certain medications

Is There a Minimum Age?

ICL surgery is generally performed in adults with stable refraction.

The exact minimum age depends on:

Local regulatory approval
Lens model
Prescription stability
Eye development
Surgeon assessment

Reaching the minimum permitted age does not automatically establish suitability.

Is There a Maximum Age?

There is no single biological cut-off that applies to every patient.

Increasing age raises other considerations, including:

Presbyopia
Early cataract
Reduced accommodation
Endothelial cell density
Glaucoma risk
Future need for cataract surgery
Changing visual priorities

Patients with early cataract may be better served by cataract surgery rather than placing an ICL in front of a lens that may soon require removal.

Can ICL Treat Low Myopia?

Yes, in selected patients.

ICL may be considered for lower myopia when:

The cornea is unsuitable for laser surgery
Dry-eye risk is significant
The patient prefers not to remove corneal tissue
Optical quality is a priority
The anatomy is suitable
The patient accepts intraocular surgical risks and long-term monitoring

Studies comparing ICL with SMILE in low or moderate myopia have reported similar safety, efficacy and refractive predictability. Halos were more frequently reported after ICL in some cohorts, while corneal laser procedures produced greater changes in some corneal higher-order aberrations. ferent from high-myopia treatment because a patient with a low prescription may also be an excellent candidate for spectacles, contact lenses or corneal laser surgery.

Is ICL Especially Useful for High Myopia?

ICL is particularly valuable for high myopia because:

No corneal stromal tissue is removed.
Very high powers can be corrected.
The cornea retains its preoperative shape.
Optical zones are not created by flattening the cornea.
Corrected visual acuity may improve in selected high myopes.

A meta-analysis comparing ICL with SMILE for high myopia found comparable refractive predictability, with ICL showing favourable efficacy and safety indices and less induction of total higher-order aberrations. Halos were more common after ICL. Suitable?

ICL may be unsuitable or require special caution in patients with:

Shallow anterior chambers
Low endothelial cell density
Visually significant cataract
Uncontrolled glaucoma
Narrow drainage angles
Active uveitis
Active eye infection
Severe iris abnormality
Significant zonular weakness
Uncontrolled diabetes
Pregnancy or breastfeeding
Unstable refraction
Unrealistic expectations

Pregnancy and Breastfeeding

Elective ICL surgery is generally postponed during pregnancy and breastfeeding.

Possible concerns include:

Refractive fluctuation
Hormonal changes
Medication exposure
Changing corneal or lens measurements
The elective nature of surgery

Measurements should be repeated after the prescription has stabilised.

Diabetes

Well-controlled diabetes does not automatically exclude every patient.

The assessment should consider:

Blood-glucose stability
HbA1c
Diabetic retinopathy
Lens clarity
Endothelial cell density
Wound healing
Infection risk
Prescription stability

Poorly controlled diabetes may cause fluctuating refraction and less predictable healing.

Keratoconus

An ICL does not treat keratoconus or strengthen the cornea.

It may be considered in selected patients when:

Keratoconus is stable
Corneal cross-linking has already been performed when indicated
The remaining refractive error is suitable
Spectacles or contact lenses provide useful corrected vision
Corneal shape is sufficiently stable for lens-power calculation

A systematic review found that ICL implantation after cross-linking can improve refractive outcomes in selected keratoconic eyes, but the quality and duration of evidence remain more limited than for ordinary myopia. require rigid or scleral contact lenses for irregular astigmatism.

Glaucoma

Patients with glaucoma require careful assessment because ICL implantation can affect:

Anterior-chamber angle width
Aqueous flow
Intraocular pressure
Pigment dispersion
Future glaucoma treatment

An eye with advanced or uncontrolled glaucoma may not be suitable.

Cataract

A visually significant cataract generally makes ICL implantation inappropriate.

The natural lens is already becoming cloudy and may need to be removed.

In such cases, cataract surgery with an appropriate intraocular lens may address both:

Lens opacity
Refractive error

The Pre-ICL Assessment

The preoperative assessment determines:

Whether the eye has enough internal space
Which lens power is required
Whether a toric lens is needed
Which lens size is most appropriate
Whether the corneal endothelium is healthy
Whether retinal or optic-nerve disease limits visual potential

Medical and Ocular History

Important information includes:

Previous eye surgery
Eye trauma
Glaucoma
Uveitis
Retinal tears or detachment
Cataract
Diabetes
Autoimmune disease
Medication
Pregnancy plans
Contact-lens use
Previous corneal laser surgery
Family history of retinal disease or glaucoma

Visual-Acuity Testing

Both unaided and corrected vision are measured.

Corrected visual acuity helps determine the eye’s visual potential.

ICL cannot reverse poor vision caused by:

Amblyopia
Macular disease
Optic-nerve damage
Retinal scarring
Advanced glaucoma

Manifest Refraction

The subjective spectacle prescription is measured carefully.

Small inaccuracies may affect:

ICL power
Residual spherical error
Toric power
Toric axis planning

Cycloplegic Refraction

Dilating drops relax the focusing mechanism.

This may be helpful in:

Younger adults
Inconsistent refraction
Accommodative spasm
Large differences between measurements

Corneal Topography and Tomography

Although ICL does not reshape the cornea, corneal mapping remains valuable.

It may identify:

Keratoconus
Irregular astigmatism
Contact-lens warpage
Previous laser surgery
Corneal disease
The corneal component of astigmatism

ICL may correct regular refractive astigmatism but does not regularise a severely irregular cornea.

Anterior-Chamber Depth

Anterior-chamber depth is the distance between the corneal endothelium and the natural lens.

An adequate depth is required to provide space for the ICL while protecting:

The corneal endothelium
The drainage angle
The natural lens

The required minimum depends on:

Lens model
Regulatory indication
Measurement method
Eye anatomy
Surgeon assessment

White-to-White Measurement

White-to-white is the visible horizontal corneal diameter.

It has traditionally been combined with anterior-chamber depth to recommend an ICL size.

However, the ICL rests behind the iris, and the visible corneal diameter does not directly measure the ciliary sulcus.

Anterior-Segment OCT

Anterior-segment OCT can measure structures including:

Anterior-chamber width
Angle-to-angle distance
Lens rise
Crystalline-lens position
Anterior-chamber area
Anterior-chamber volume

It may also be used after surgery to measure vault, lens position and angle configuration.

Ultrasound Biomicroscopy

Ultrasound biomicroscopy can image structures hidden behind the iris.

It may assess:

Sulcus-to-sulcus distance
Ciliary-body anatomy
ICL footplate position
Lens rise
Posterior-chamber relationships

Modern sizing approaches may combine white-to-white, anterior-chamber depth, AS-OCT or ultrasound measurements. No current formula predicts every postoperative vault perfectly because the ciliary sulcus, crystalline lens and ICL can interact in complex ways. ll Count

The corneal endothelium is the innermost layer of the cornea.

These cells pump fluid out of the cornea to keep it clear.

They do not regenerate substantially after loss.

An endothelial cell count is therefore performed before ICL surgery.

The result is interpreted according to:

Age
Cell density
Cell shape
Cell-size variation
Anterior-chamber depth
Expected long-term risk

Pupil Measurement

Pupil size may influence:

Halos
Glare
Night vision
Awareness of the central port
Optical-zone interactions

A large pupil does not automatically exclude ICL surgery but should be included in counselling.

Eye-Pressure Measurement

Eye pressure is measured before surgery.

The drainage angles should also be assessed because ICL implantation may narrow the angles.

Dilated Retinal Examination

High myopia increases the lifetime risk of:

Retinal tears
Retinal detachment
Myopic macular degeneration
Macular schisis
Other peripheral retinal abnormalities

ICL corrects the focus of the eye but does not shorten the eyeball or remove these retinal risks.

What Is ICL Sizing?

ICLs are available in several overall lengths.

The selected size affects how the lens sits behind the iris.

A lens that is relatively large for the eye generally produces greater forward bowing or vault.

A lens that is relatively small may produce lower vault.

Sizing is one of the most important parts of ICL planning.

What Is Vault?

Vault is the distance between:

The back surface of the ICL
The front surface of the natural crystalline lens

The vault is usually assessed centrally.

It is commonly measured using anterior-segment OCT.

Why Is Vault Important?

The ICL should be separated from the natural lens while avoiding excessive crowding of the anterior chamber.

A suitable vault helps reduce the risk of:

Contact with the natural lens
Cataract
Angle narrowing
Pigment dispersion
Raised eye pressure
Endothelial cell loss
Lens instability

What Is an Ideal Vault?

There is no single perfect measurement for every eye.

A commonly used clinical target is approximately 250 to 750 micrometres, although acceptable ranges depend on:

Patient age
Anterior-chamber anatomy
Angle width
Endothelial cell density
Lens position
Changes over time
Surgeon judgement

Vault should not be interpreted as an isolated number.

Does Vault Change?

Yes.

Vault may vary with:

Pupil size
Lighting
Accommodation
Age
Natural-lens growth
ICL orientation
Body position
Measurement device

Long-term studies show that vault commonly decreases gradually over time as the natural lens changes with age. ow vault places the ICL closer to the natural lens.

Possible concerns include:

Anterior subcapsular lens opacity
Cataract
Lens contact
Reduced margin for future natural-lens growth

However, a low numerical vault does not always require surgery.

Ten-year data involving central-port ICLs found stable vision and pressure in both low- and normal-vault groups, with no ICL-induced anterior subcapsular opacity in that cohort. The results do not mean that every low vault is safe; age, actual lens contact and other anatomical findings remain important. excessive vault pushes the iris forwards.

Possible concerns include:

Narrowing of the drainage angle
Raised eye pressure
Pigment dispersion
Iris contact
Increased proximity to the corneal endothelium

A paired-eye study with seven-year follow-up found greater endothelial cell loss in eyes with higher vault than in their lower-vault fellow eyes, supporting continued monitoring rather than assuming that high vault is harmless. f the Vault Is Unsuitable?

Management depends on:

Actual vault
Symptoms
Eye pressure
Angle width
Endothelial cell count
Natural-lens changes
Patient age

Options may include:

Observation
More frequent review
Rotating the ICL to a different orientation
Exchanging the ICL for a different size
Removing the ICL

How Is ICL Surgery Performed?

Step 1: Confirming the Plan

Before surgery, the team confirms:

Patient identity
Correct eye
ICL model
Lens power
Lens size
Toric power and axis when applicable
Allergies
Medication
Consent

Step 2: Pupil Dilation

Dilating drops enlarge the pupil.

A well-dilated pupil allows the lens to pass safely behind the iris.

Step 3: Anaesthesia

Anaesthetic eye drops numb the eye.

Some patients receive mild sedation.

Step 4: Sterile Preparation

The eyelids and surrounding skin are cleaned.

A sterile drape is placed around the eye.

An eyelid holder gently keeps the eye open.

Step 5: Creating the Corneal Incision

A small incision is made near the edge of the cornea.

Additional tiny side-port incisions may be used.

Step 6: Maintaining the Anterior Chamber

The surgeon may use:

An ophthalmic viscosurgical device
Balanced salt solution
A combination of techniques

These maintain space and protect delicate structures.

Studies comparing selected techniques with and without viscosurgical material have reported satisfactory outcomes, but the method should be chosen by the surgeon according to the eye and surgical system. ing the ICL

The folded lens is loaded into an injector cartridge.

It is delivered through the corneal incision into the anterior chamber.

Step 8: Allowing the Lens to Unfold

The flexible ICL unfolds inside the eye.

The surgeon ensures that its orientation is correct.

Step 9: Positioning Behind the Iris

The four footplates are gently placed behind the iris.

The lens is centred in front of the natural lens.

Step 10: Aligning a Toric ICL

A toric ICL must be aligned with its intended axis.

The surgeon may use:

Preoperative corneal marks
Digital image guidance
Intraoperative axis systems
Reference marks on the lens

Step 11: Removing Viscoelastic

When a viscosurgical device has been used, it must be removed thoroughly.

Retained material may cause a postoperative pressure spike.

Step 12: Checking the Eye

The surgeon checks:

ICL position
Pupil shape
Anterior-chamber depth
Wound sealing
Eye pressure or chamber firmness
Absence of significant bleeding

The incision commonly seals without stitches.

Can Both Eyes Be Treated on the Same Day?

Practice varies.

ICL surgery may be performed:

One eye at a time
On separate dates
Bilaterally on the same day under strict protocols

Reasons for separating the procedures include:

Assessing the first-eye vault
Confirming the first-eye refractive result
Reducing simultaneous bilateral recovery
Reducing the theoretical impact of a bilateral complication

Same-day surgery may be considered in selected settings with independent sterile preparation for each eye.

What Is a Toric ICL?

A toric ICL corrects both:

Myopia
Astigmatism

It contains a cylindrical optical correction that must remain aligned with a specific axis.

Why Is Toric Alignment Important?

A toric lens loses astigmatic effectiveness when it rotates away from its intended position.

Increasing rotation may cause:

Residual astigmatism
Blurred vision
Ghosting
Reduced unaided vision

Can a Toric ICL Rotate?

Yes.

Small degrees of rotation may have little clinical effect.

More significant rotation may require:

Observation
Spectacle correction
Surgical realignment
Lens exchange

Modern toric ICL studies generally report favourable rotational stability. In a 2025 study of 403 eyes, approximately 5% experienced defined rotation events, which were managed with realignment or exchange when necessary. orrect Presbyopia?

A standard ICL does not restore accommodation.

The natural lens continues ageing.

Patients may therefore need reading spectacles as presbyopia develops.

Possible strategies include:

Both eyes corrected for distance
Mild monovision
Leaving one eye slightly short-sighted
Presbyopia-correcting ICL designs where available

Presbyopia-correcting ICL technology has shown promising early outcomes, but long-term evidence is less extensive than for standard myopic ICLs. mmediately After Surgery?

Temporary symptoms may include:

Blurred vision
Light sensitivity
Mild aching
Grittiness
Watering
Halos
A dilated pupil
A bloodshot eye

Vision may be clearer within hours but can fluctuate.

Eye Drops After Surgery

Medication may include:

Antibiotic drops
Steroid drops
Non-steroidal anti-inflammatory drops
Eye-pressure-lowering medication
Lubricating drops

The exact regimen varies.

Patients should:

Wash their hands
Avoid touching the bottle tip to the eye
Space different drops apart
Follow the prescribed taper
Avoid stopping steroid medication without advice

The First Day

A postoperative review commonly assesses:

Unaided vision
ICL position
Vault
Eye pressure
Corneal clarity
Inflammation
Pupil response

Early eye-pressure monitoring is particularly important.

The First Week

Vision commonly continues to sharpen.

Temporary symptoms may include:

Halos
Glare
Mild dryness
Fluctuating focus
Light sensitivity

The First Month

The refractive result and lens position generally become more stable.

A toric lens axis may be rechecked.

Long-Term Follow-Up

An ICL should not be treated as an operation that requires no further eye care.

Long-term examinations may assess:

Vision
Refraction
Eye pressure
Anterior-chamber angle
Vault
Natural-lens clarity
Endothelial cell density
Retina
Toric alignment

Eight- and ten-year studies of central-port ICLs report generally stable refractive outcomes and favourable safety in followed cohorts, but exchanges, residual-error treatments and age-related cataracts still occurred. l Results

Modern ICL implantation is generally effective and predictable in carefully selected patients.

A 2025 systematic review and meta-analysis of central-port V4c and V5 lenses concluded that these lenses provide high efficacy, predictability and safety in healthy adult eyes. depend on:

Accuracy of refraction
Lens power
Toric alignment
Lens sizing
Healing
Macular and optic-nerve health
Natural-lens clarity
Ocular-surface quality

Can Vision Become Better Than It Was with Spectacles?

Some high-myopic patients gain lines of corrected visual acuity after ICL surgery.

Possible reasons include:

Reduced image minification compared with strong minus spectacles
Improved retinal image size
Reduced spectacle-induced peripheral distortion
Good preservation of corneal optics

Improvement is possible but should not be guaranteed.

Visual Quality

ICL avoids the corneal reshaping involved in LASIK, PRK and SMILE.

Potential optical benefits include:

Less induction of some corneal higher-order aberrations
Large effective optical treatment
Preservation of corneal asphericity
Good contrast in selected high-myopic eyes

However, possible visual symptoms include:

Halos
Glare
Rings
Starbursts
Ghosting
Night-driving difficulty

Comparative studies commonly identify halos as one of the leading visual complaints after ICL, despite high overall satisfaction. ctive Error

The final prescription may differ from the intended target.

Possible causes include:

Measurement variation
Lens-power limitations
Toric misalignment
Surgically induced corneal astigmatism
Natural refractive change
Lens rotation
Healing

Management may include:

Spectacles
Contact lenses
Corneal laser enhancement
Toric realignment
ICL exchange

Raised Eye Pressure

Eye pressure may rise because of:

Retained viscosurgical material
Steroid response
Pupillary block
Excessive vault
Angle narrowing
Pigment dispersion
Inflammation

Possible symptoms include:

Eye pain
Headache
Halos
Nausea
Blurred vision

A pressure rise may also be asymptomatic.

Pupillary Block

Pupillary block occurs when aqueous fluid cannot pass normally from behind the iris to the front of the eye.

This can cause sudden marked elevation of eye pressure.

The central port in current EVO-type lenses substantially reduces the need for preoperative iridotomy and the risk of pupillary block related to absent aqueous flow, but block remains possible if the central port is obstructed or another problem occurs.

Pigment Dispersion

An ICL with excessive vault or unfavourable position may contact the back of the iris.

This may release pigment.

Pigment can accumulate in the drainage system and contribute to:

Raised eye pressure
Pigment dispersion
Secondary glaucoma

Long-term pressure and angle monitoring remain important even when early recovery is uncomplicated.

Cataract Formation

The natural crystalline lens remains in the eye and continues ageing.

Cataract may develop because of:

Natural age-related change
Low vault
Contact between the ICL and natural lens
Surgical trauma
Metabolic or genetic factors

Earlier ICL designs without a central port had a greater historical concern regarding anterior subcapsular lens opacity.

Central-port lenses appear to have reduced this risk, although they do not prevent ordinary age-related cataract. Long-term studies continue to identify age and low vault as relevant associations with cataract development. f a Cataract Develops?

Treatment may involve:

Removing the ICL
Performing cataract surgery
Replacing the cloudy natural lens with an intraocular lens

The ICL is usually removed during the cataract operation.

Endothelial Cell Loss

Intraocular surgery causes some endothelial cell loss.

The ICL also occupies space within the anterior segment.

A 2024 meta-analysis found average endothelial cell loss of approximately:

1.3% at three months
1.8% at 12 months
3.8% at a mean follow-up of about 21 months

The pattern suggested that early surgical trauma contributed substantially to the initial loss. elial behaviour varies between studies and individuals.

Continued monitoring is particularly important when there is:

High vault
Shallow anterior chamber
Low preoperative cell density
Age-related endothelial decline
Previous intraocular surgery

Infection

Endophthalmitis is a rare but serious infection inside the eye.

Possible symptoms include:

Increasing pain
Increasing redness
Worsening vision
Marked light sensitivity
Eyelid swelling
Discharge

Urgent treatment is required.

Inflammation

Mild inflammation is expected after surgery.

More significant inflammation may cause:

Pain
Light sensitivity
Blurred vision
Redness
Deposits on the ICL
Posterior synechiae

Treatment may include steroid and pupil-dilating medication.

Corneal Swelling

Temporary corneal swelling may occur because of:

Surgical manipulation
Raised pressure
Endothelial stress
Inflammation

Persistent swelling requires assessment of endothelial function and eye pressure.

Lens Decentration

The ICL may not remain perfectly centred.

Minor decentration may cause no symptoms.

Significant decentration may contribute to:

Glare
Halos
Reduced optical quality
Vault asymmetry
Iris contact

Retinal Detachment

ICL surgery does not remove the retinal risks associated with high myopia.

A highly myopic eye remains long and structurally predisposed to:

Retinal tears
Retinal detachment
Myopic macular degeneration

New flashes, floaters or a curtain-like shadow require urgent retinal assessment.

Does ICL Cause Dry Eye?

ICL surgery generally causes less direct corneal nerve disruption than LASIK, PRK or SMILE because the central cornea is not reshaped.

Temporary dryness can still occur because of:

Surgical drops
The corneal incision
Eyelid preparation
Reduced blinking
Pre-existing contact-lens-related disease
Postoperative medication

Patients with significant pre-existing dry eye should still be treated before surgery.

ICL Versus LASIK

Possible Advantages of ICL

No corneal stromal tissue removal
Suitable for higher myopia
Preserves corneal shape
Removable or exchangeable
Often favourable optical quality in high myopia
No LASIK flap

Possible Advantages of LASIK

No intraocular implant
No cataract or vault concern
No long-term endothelial monitoring specific to a phakic lens
Rapid recovery
Easier enhancement in suitable corneas
Lower surgical complexity for low prescriptions

Important Difference

LASIK creates a permanent corneal alteration.

ICL introduces a permanent intraocular implant unless removed.

Neither is risk-free.

ICL Versus SMILE

Possible Advantages of ICL

No corneal tissue removal
Suitable for higher myopia
Less induction of corneal higher-order aberrations
Removable or exchangeable

Possible Advantages of SMILE

No intraocular surgery
No implant sizing or vault issue
No ICL-related cataract risk
No need for long-term endothelial monitoring related to an implant
Small corneal incision

Meta-analysis suggests that ICL may offer optical and corrected-vision advantages in high myopia, while halos are more common after ICL. or TransPRK

Possible Advantages of ICL

Faster early visual recovery
No epithelial defect
No corneal haze
No removal of corneal stromal tissue
Suitable for higher prescriptions

Possible Advantages of Surface Laser

No intraocular implant
No vault or sizing issue
No lens-related cataract concern
No intraocular surgical infection risk
No long-term implant monitoring

Surface laser may be preferable for a low prescription and structurally normal cornea when the patient accepts slower recovery.

ICL Versus Cataract Surgery

ICL preserves the natural lens.

This preserves accommodation in younger patients.

Cataract surgery removes the natural lens and replaces it with an artificial intraocular lens.

Cataract surgery may be more appropriate when:

A cataract is present
Accommodation is already significantly reduced
Lens-related refractive change is occurring
The natural lens will probably require removal soon

Clear-lens extraction in a young high myope also removes accommodation and carries retinal considerations.

Is ICL Better Than Laser Eye Surgery?

There is no universal answer.

ICL may be favoured when:

Myopia is high
The cornea is thin
Corneal tomography is unsuitable
Dry-eye risk is high
Optical-quality preservation is a priority
The patient accepts intraocular surgery

Corneal laser may be favoured when:

The prescription is within a safe range
The cornea is healthy
The patient prefers to avoid an intraocular implant
Long-term vault and endothelial monitoring are undesirable

Can the ICL Be Felt?

No.

The lens is inside the eye and is not in contact with the eyelids.

A persistent foreign-body sensation is more likely to be caused by:

Dry eye
The corneal incision
Eyelid inflammation
A surface abrasion
Postoperative drops

Can the ICL Fall Out?

No.

The lens is positioned behind the iris and cannot fall out through normal activity.

It can move or rotate inside the eye, particularly if its size or support is unsuitable.

Can I Rub My Eyes?

Eye rubbing should be avoided during early healing.

Long-term vigorous rubbing should also be discouraged because it can:

Irritate the ocular surface
Worsen allergy
Cause eye trauma
Affect patients with keratoconus susceptibility

When Can I Exercise?

Gentle walking is generally possible early.

Strenuous exercise, heavy lifting and contact sports may need to be avoided temporarily.

The surgeon’s specific instructions take priority.

When Can I Swim?

Swimming is usually avoided during the early healing period because water may contain:

Bacteria
Parasites
Chemicals
Irritants

When Can I Use Screens?

Screens do not damage the ICL.

Prolonged screen use may worsen dryness and eye fatigue because blinking decreases.

When Can I Drive?

Driving should resume only when:

Vision meets the legal standard
The patient feels confident
Glare is manageable
Depth perception is satisfactory
Sedative effects have resolved
The surgeon has not advised otherwise

The patient should not drive home immediately after surgery.

When Can I Fly?

Routine uncomplicated ICL surgery does not place a gas bubble inside the eye and usually does not prevent flying.

Travel should not interfere with:

Early postoperative reviews
Eye-pressure checks
Access to urgent care

Common Myths

“ICL Means Implantable Contact Lens”

Commonly used, but technically imprecise.

The formal name is Implantable Collamer Lens.

“The ICL Replaces the Natural Lens”

False.

The natural lens remains inside the eye.

“ICL Is Only for Extremely High Myopia”

False.

It is particularly useful for high myopia but may be considered for selected low-to-moderate myopia.

“ICL Is Completely Reversible”

Misleading.

The lens can usually be removed, but the eye has still undergone intraocular surgery.

“The ICL Prevents Presbyopia”

False.

The natural lens continues ageing.

“The ICL Prevents Cataract”

False.

The natural lens can still develop cataract.

“The ICL Never Needs Monitoring”

False.

Vault, eye pressure, lens clarity and endothelial cells require long-term review.

“A High Vault Is Always Better Than a Low Vault”

False.

Both excessive and insufficient vault may create different risks.

“A Low Vault Always Requires Immediate Exchange”

False.

Management depends on lens contact, age, cataract change, pressure, anatomy and the trend over time.

“ICL Removes the Retinal Risk of High Myopia”

False.

The eyeball remains anatomically myopic.

“The ICL Can Be Seen by Other People”

Usually false.

The lens is positioned behind the iris and is generally not visible during ordinary interaction.

“ICL Is Safer Than LASIK for Everyone”

False.

The procedures have different risk profiles.

The safest choice depends on the individual eye.

Frequently Asked Questions

Can ICL Correct Astigmatism?

Yes.

A toric ICL can correct myopia and regular astigmatism.

Irregular astigmatism may not be fully corrected.

Can Both Eyes Have Different ICL Sizes?

Yes.

The eyes may differ in:

White-to-white diameter
Sulcus dimensions
Lens rise
Anterior-chamber depth
Previous surgical result

Each eye should be planned individually.

Can Both Eyes Have Different Powers?

Yes.

Lens power is selected separately for each eye.

Can ICL Correct Very High Myopia?

Yes, within the available lens-power range and anatomical suitability.

The retina and macula should also be assessed because high myopia may limit visual potential.

Can ICL Improve My Night Vision?

Reducing a strong spectacle prescription may improve visual quality for some patients.

Others may notice new halos or rings.

Night-vision outcomes vary.

Can ICL Cause Halos?

Yes.

Halos are among the more frequently reported visual symptoms after ICL.

They often improve but may persist.

Can the Central Hole Be Seen?

Most patients do not perceive it directly.

A minority may notice rings or halos under particular lighting conditions.

What Happens if the ICL Is the Wrong Size?

The eye may develop:

Low vault
High vault
Angle narrowing
Lens contact
Excessive iris contact
Optical symptoms

The lens may require rotation, exchange or removal.

Can an ICL Be Repositioned?

Yes.

A toric lens may be surgically realigned.

A lens may also be rotated to alter vault in selected cases.

Can ICL Be Exchanged for Another Size?

Yes.

Lens exchange is possible when the size or vault is unsuitable.

It is another intraocular operation and carries additional risk.

Can I Have LASIK After ICL?

A small residual prescription may sometimes be corrected with LASIK or PRK if:

The cornea is suitable
Refraction is stable
The ICL is well positioned
The expected benefit justifies the risk

Can I Have ICL After LASIK?

Yes, in selected patients.

ICL may be considered for:

Residual myopia
Recurrent myopia
A prescription too large for further safe corneal treatment

Previous LASIK measurements and corneal health must be assessed.

Can I Have Cataract Surgery Later?

Yes.

The ICL is usually removed when cataract surgery is performed.

The cataract surgeon then implants an appropriate intraocular lens.

Can ICL Treat Lazy Eye?

No.

It can correct the optical prescription but cannot reverse amblyopia established during childhood.

Does ICL Change Eye Colour?

No.

The iris is not altered.

Can I Wear Contact Lenses After ICL?

Yes, if needed.

Possible reasons include:

Residual refractive error
Irregular astigmatism
Special visual tasks

Can ICL Cause Blindness?

Severe permanent visual loss is rare but possible.

Potential causes include:

Infection
Uncontrolled glaucoma
Severe endothelial failure
Retinal complications
Major inflammation
Other unrelated ocular disease

The risk is small but not zero.

How Often Should the ICL Be Checked?

The schedule is individualised.

Long-term review may include:

Annual examination
Eye-pressure measurement
Vault assessment
Endothelial cell count
Natural-lens assessment
Retinal examination

More frequent review may be needed when vault, pressure or endothelial findings are borderline.

When to Seek Urgent Eye Care

Seek urgent assessment for:

Increasing eye pain
Increasing redness
Rapidly worsening vision
Severe headache
Nausea or vomiting
Marked halos with pain
Thick discharge
Significant light sensitivity
Sudden loss of previously improving vision
New flashes
A sudden shower of floaters
A curtain or shadow
Eye trauma

These symptoms may indicate:

Raised eye pressure
Infection
Significant inflammation
Retinal tear or detachment
Another ocular emergency

An ICL Assessment Checklist

Visual Goals to Discuss

Distance vision
Reading vision
Computer vision
Night driving
Contact sports
Occupation
Spectacle independence
Tolerance of halos
Future presbyopia

Medical Information to Report

Diabetes
Autoimmune disease
Pregnancy or breastfeeding
Medication
Allergies
Previous healing problems
Family history of glaucoma

Eye History to Report

Previous LASIK, PRK or SMILE
Keratoconus
Corneal cross-linking
Glaucoma
Uveitis
Cataract
Retinal tear or detachment
Intravitreal injections
Eye trauma
Contact-lens intolerance

Measurements That May Be Required

Manifest refraction
Cycloplegic refraction
Corneal topography
Corneal tomography
Anterior-chamber depth
White-to-white diameter
AS-OCT measurements
Ultrasound biomicroscopy
Endothelial cell count
Eye pressure
Pupil size
Dilated retinal examination

Questions to Ask the Surgeon

Am I genuinely suitable for ICL?
Why is ICL preferred over LASIK, SMILE or PRK?
Which ICL model will be used?
Is a toric ICL required?
How was the lens size selected?
What vault is expected?
What happens if the vault is too low or high?
What is my endothelial cell count?
Is my anterior chamber deep enough?
What is my risk of cataract?
What is my risk of raised eye pressure?
How likely are halos?
Can the lens rotate?
How would residual refractive error be managed?
Can the lens be removed or exchanged?
How frequently will I need long-term review?
What symptoms require urgent assessment?

The Bottom Line

An Implantable Collamer Lens is a phakic intraocular lens positioned behind the iris and in front of the natural crystalline lens.

It may correct:

Myopia
Myopic astigmatism with a toric ICL
Selected low, moderate or high prescriptions

Potential advantages include:

No removal of corneal stromal tissue
Treatment of high myopia
Preservation of corneal shape
Good optical quality
Rapid visual recovery
Removal or exchange when necessary

Possible disadvantages include:

Intraocular surgery
Need for precise sizing
Lifelong monitoring
Halos or glare
Risk of cataract
Risk of raised pressure
Endothelial cell loss
Toric rotation
Need for lens exchange in selected cases

Vault is a central part of ICL care.

Low vault may increase concern about the natural lens and cataract.

High vault may narrow the drainage angle and increase concern about pressure, iris contact or endothelial health.

Modern central-port ICLs have reduced some of the problems associated with earlier lens designs and have demonstrated favourable outcomes over eight to ten years in published cohorts. Nevertheless, long-term monitoring remains necessary because the natural lens, anterior chamber and corneal endothelium continue changing with age. depends on:

Prescription
Corneal structure
Anterior-chamber anatomy
Endothelial health
Age
Retinal condition
Visual goals
Acceptance of intraocular surgical risks

The most important message is:

ICL surgery should not be selected merely because it can correct a high prescription or avoid corneal laser treatment. A safe result depends on careful anatomical assessment, accurate lens power and size selection, suitable vault, precise surgery and long-term monitoring of the natural lens, eye pressure and corneal endothelium.

References

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