What is epithelial ingrowth after LASIK?

Epithelial cells proliferating in the flap interface A few epithelial cells slip beneath the flap edge and proliferate in nests or sheets within the interface, which is why the flap edge never seals like original tissue.

Overgrowth of conjunctival tissue onto the cornea

Regrowth of epithelium across a persistent defect

Keratinisation of the corneal surface epithelium

Why can aggressive epithelial ingrowth destroy a LASIK flap?

Epithelial cells release enzymes that digest stromal collagen Epithelial cells release enzymes capable of digesting the surrounding stromal collagen, which explains the risk of flap melt in the more aggressive cases.

The cells mechanically compress the endothelial pump

The cells trigger immune rejection of the flap

The cells obstruct the limbal supply to the flap

Which is the most important risk factor for epithelial ingrowth after LASIK?

An enhancement in which the flap is lifted again Enhancement procedures that lift the flap a second time are the most important risk factor, alongside buttonholes, tears, irregular edges and post-operative trauma.

A thin preoperative central cornea

Topical steroid use after surgery

A low preoperative refractive error

How is asymptomatic epithelial ingrowth after LASIK most often first detected?

As translucent islands at the peripheral flap edge Many cases are found incidentally at a routine check as small, grayish-white translucent islands at the peripheral flap edge, with no symptoms at all.

As a dense central infiltrate with pain

As diffuse haze across the whole interface

As linear folds running through the visual axis

Which feature points to diffuse lamellar keratitis rather than epithelial ingrowth?

Granular hazy deposits appearing in the first days Diffuse lamellar keratitis is a sterile inflammation that develops in the first days after surgery with granular, hazy deposits, unlike the translucent pearls of ingrowth.

Translucent pearls with a sharp rounded edge

A whitish line at the leading edge of the lesion

Slow progression across months of follow-up

How does epithelial ingrowth appear on anterior segment OCT?

A hyperreflective layer within the flap interface Anterior segment OCT shows the cells as a hyperreflective layer in the interface, while topography may show localized steepening or irregular astigmatism over the area.

A fluid cleft beneath Descemet membrane

Diffuse thickening of the epithelium alone

Complete loss of interface reflectivity

Which epithelial ingrowth after LASIK can reasonably be observed rather than removed?

Stable growth within 1 to 2 mm of the flap edge Small stable areas within 1 to 2 mm of the flap edge can be watched with regular follow-up and photographs, while growth that advances, reaches the visual axis, thins the flap or causes symptoms must be removed.

Growth that has reached the visual axis

Growth accompanied by flap thinning

Growth causing glare and irregular astigmatism

What does surgical removal of epithelial ingrowth after LASIK involve?

Scraping both the stromal bed and the flap underside The surgeon lifts the flap and scrapes epithelium from both the stromal bed and the underside of the flap before careful repositioning, sometimes adding sutures, fibrin glue or a bandage lens to prevent recurrence.

Excimer ablation of the central flap surface

Full-thickness penetrating keratoplasty

Amniotic membrane grafting over the flap edge

Which approach do surgeons often prefer for enhancement when a LASIK flap is old?

Surface ablation, avoiding lifting the flap Because lifting an old flap invites epithelial entry, surgeons often prefer surface ablation for enhancement in that situation.

Lifting the flap with a blunt spatula

Creating a second flap beneath the first

A repeat microkeratome pass at the same depth

What is the outcome of neglected, advanced epithelial ingrowth after LASIK?

Scarring with irregular astigmatism Most patients do well with timely treatment, but neglected advanced cases leave scars and irregular astigmatism after the flap thins and melts.

Spontaneous resolution with a clear cornea

Progressive endothelial cell loss and edema

Corneal vascularisation growing in from the limbus

Epithelial Ingrowth After LASIK: Signs and Treatment

After LASIK, the corneal flap is replaced and heals to the underlying stroma.

In some patients, a few epithelial cells slip beneath the flap edge and start to grow in the interface.

This is epithelial ingrowth, and it is one of the more important late complications after flap-based refractive surgery, because it can be self-limited and harmless or, in the worst case, destroy the flap.

How it happens

The edge of the flap does not seal like the original tissue.

Epithelium can enter the interface through a gap at the edge, through a buttonhole in the flap, or on the underside of a lifted flap during an enhancement.

Once the cells are inside, they proliferate in nests or sheets, and if the flap is not tightly adherent, the growth progresses.

Epithelial cells also release enzymes that can digest the stromal collagen around them, and this explains the risk of flap melt in more aggressive cases.

Risk factors

Enhancement procedures, in which the flap is lifted a second time, which is the most important risk factor
Flap buttonholes, tears, or irregular edges
Corneal trauma after surgery
Epithelial defects at the time of surgery, or a poorly adherent flap
Hyperopic LASIK, where a larger flap or a wider ablation is used
Older age, diabetes, and recurrent erosion

Test your knowledge 10 questions from this article

Clinical picture

Many cases are found incidentally at a routine check, as small, grayish-white, translucent islands at the peripheral flap edge, with no symptoms
Progressive cases produce blur, glare, irregular astigmatism, and sometimes pain or foreign-body sensation
Under the slit lamp, there are pearls or sheets of translucent cells with a sharp, rounded edge, which are best seen with retroillumination, and there may be a whitish line at the leading edge
In advanced cases, the overlying flap thins and melts, with stromal haze and scarring

Differential diagnosis

Diffuse lamellar keratitis, a sterile inflammation that develops in the first days, with granular, hazy deposits (see diffuse lamellar keratitis)
Infectious keratitis, which has an infiltrate, pain, and redness
Interface debris or fibers, which are non-progressive
Striae and flap folds, seen as linear lines
Pressure-induced interface fluid in patients with elevated intraocular pressure

Management

Observation is appropriate for small, peripheral, non-progressive ingrowth that does not threaten the visual axis or flap integrity, with regular follow-up and documentation by photographs.
Surgical removal is needed for progressive ingrowth, visual disturbance, flap melt, or involvement near the visual axis. The surgeon lifts the flap, scrapes the epithelium from both the stromal bed and the underside of the flap, and replaces the flap carefully. Sutures, fibrin glue, or a bandage lens may be used to prevent recurrence.
Nd:YAG laser has been used to ablate small nests.
Recurrent cases may need repeat treatment with additional measures, such as suturing the flap edge.

Prevention

Careful flap creation and repositioning, minimal manipulation, avoiding epithelial defects, and caution at the time of enhancement are important.

Surgeons often prefer surface ablation for enhancement when the flap is old, to avoid lifting it.

Epithelial Ingrowth After LASIK: When Cells Grow Where They Don’t Belong

How to find it

Examine the flap edges with a slit lamp, using direct illumination and retroillumination. Epithelial cells look like translucent, pearl-like clusters or sheets, with sharp margins and sometimes a fine whitish line at the border. Compare with previous visits, because the key question is whether the lesion has grown. Corneal topography may show localized steepening or irregular astigmatism over an area of ingrowth, and anterior segment OCT shows the cells as a hyperreflective layer in the interface.

Grading for decisions

Surgeons often grade ingrowth by the distance it has advanced from the flap edge and by its effect on the flap. Small areas within 1 to 2 mm of the edge that are stable can be watched. Areas that grow, that reach the visual axis, that cause flap thinning, or that cause symptoms need to be removed. Recurrent ingrowth after removal suggests a persistent entry point, and the surgeon may suture the flap or use glue.

Counselling

Explain to the patient that ingrowth is rare, that it can be treated, and that early detection helps to prevent damage. Patients who have had enhancement procedures or flap complications should be told to attend regular follow-up and to report blur, glare, or discomfort.

Documenting and sharing the finding

Record the location, size, and distance from the visual axis, and take an image. If you are not the operating surgeon, send a note to the surgeon, since the history of the flap and the enhancements is important in deciding on management.

Prognosis

Most patients have a good outcome with timely treatment.

Neglected, advanced cases can leave scars and irregular astigmatism.

References

Wang MY, Maloney RK. Epithelial ingrowth after laser in situ keratomileusis. Am J Ophthalmol. 2000;129:746-751.
Ting DSJ, Srinivasan S, Danjoux JP. Epithelial ingrowth following laser in situ keratomileusis (LASIK): prevalence, risk factors, management and visual outcomes. BMJ Open Ophthalmol. 2018;3:e000133.
Ambrosio R Jr, Wilson S. Complications of laser in situ keratomileusis: etiology, prevention, and treatment. J Refract Surg. 2001;17:350-379.
Krachmer JH, Mannis MJ, Holland EJ, eds. Cornea. 3rd ed. Philadelphia: Elsevier; 2011.

Test yourself

A few questions straight from this article.

1 / 10 0 correct

What is epithelial ingrowth after LASIK?
A few epithelial cells slip beneath the flap edge and proliferate in nests or sheets within the interface, which is why the flap edge never seals like original tissue.
Why can aggressive epithelial ingrowth destroy a LASIK flap?
Epithelial cells release enzymes capable of digesting the surrounding stromal collagen, which explains the risk of flap melt in the more aggressive cases.
Which is the most important risk factor for epithelial ingrowth after LASIK?
Enhancement procedures that lift the flap a second time are the most important risk factor, alongside buttonholes, tears, irregular edges and post-operative trauma.
How is asymptomatic epithelial ingrowth after LASIK most often first detected?
Many cases are found incidentally at a routine check as small, grayish-white translucent islands at the peripheral flap edge, with no symptoms at all.
Which feature points to diffuse lamellar keratitis rather than epithelial ingrowth?
Diffuse lamellar keratitis is a sterile inflammation that develops in the first days after surgery with granular, hazy deposits, unlike the translucent pearls of ingrowth.
How does epithelial ingrowth appear on anterior segment OCT?
Anterior segment OCT shows the cells as a hyperreflective layer in the interface, while topography may show localized steepening or irregular astigmatism over the area.
Which epithelial ingrowth after LASIK can reasonably be observed rather than removed?
Small stable areas within 1 to 2 mm of the flap edge can be watched with regular follow-up and photographs, while growth that advances, reaches the visual axis, thins the flap or causes symptoms must be removed.
What does surgical removal of epithelial ingrowth after LASIK involve?
The surgeon lifts the flap and scrapes epithelium from both the stromal bed and the underside of the flap before careful repositioning, sometimes adding sutures, fibrin glue or a bandage lens to prevent recurrence.
Which approach do surgeons often prefer for enhancement when a LASIK flap is old?
Because lifting an old flap invites epithelial entry, surgeons often prefer surface ablation for enhancement in that situation.
What is the outcome of neglected, advanced epithelial ingrowth after LASIK?
Most patients do well with timely treatment, but neglected advanced cases leave scars and irregular astigmatism after the flap thins and melts.

Ahmed Ophthalmologist

Writes and reviews the clinical articles on Educate. Every post is checked against peer-reviewed sources before it goes live.

Epithelial Ingrowth After LASIK: When Cells Grow Where They Don’t Belong