LASIK Complications

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Article initiated by:

Ladan Espandar, M.D., M.S., Majid Moshirfar, M.D.

All contributors:

Brad H. Feldman, M.D., Alex Kozak, Koushik Tripathy, MD (AIIMS), Vandana Reddy, MD, Riccardo Vinciguerra, MD, Bruno Battaglia, Anjali K. Pathak, M.D., Majid Moshirfar, M.D., Ladan Espandar, M.D., M.S., Brian Shafer, MD, Shaina N. Kumar, M.D.

Assigned editor:

Brian Shafer, MD

Review:

Assigned status Update Pending

 by Brian Shafer, MD on February 13, 2024.

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Contributing Editors:	add

LASIK complications can be categorized to intraoperative and postoperative complications:

Intraoperative Complications

The intraoperative complication rate of Laser in situ keratomileusis (LASIK) has been reported to be in between 0.7-6.6%. The most common is flap-related, after either with a traditional mechanical microkeratome or femtosecond (FS) Laser. Depending on the method of flap creation, some differences in complications do exist.

Microkeratome-related flap complications

Flap Buttonhole

Buttonholes can occur when the microkeratome exits the epithelium prematurely and then re-enters the flap again, creating a "donut."

• Risk factors include
  • suction loss
  • corneal scars or prior corneal surgery
  • steep corneas
  • large diameter flap
  • decreased intraocular pressure
  • defective blade
  • abnormal advancement of blade

Management: Abort laser ablation and do not lift the flap. A bandage contact lens can be placed temporarily. Most commonly, any laser procedure is delayed for several weeks and then PRK can be performed.

Free Cap

A free cap occurs when the entire flap is dislodged from the cornea. Risk factors include inadequate suction, a flat cornea, defective blades, and a decentered ring. A larger ring, stop ring, and larger flap hinge can help prevent free caps.

Management: Management depends on the residual stromal bed and the free cap. If the stromal bed is regular and the cap of normal thickness, laser ablation can be continued. The free cap should be placed in BSS and then replaced on the bed. Care must be taken to orient the cap properly (epithelium facing up).

Incomplete, short, or irregular flaps

Incomplete flaps can occur if the microkeratome stops prematurely. Some predisposing factors include flat corneas, corneal scars, low intraocular pressure, and loss of suction.

Management: Depending on the amount of residual stroma and the location of the flap hinge, the surgeon should decide to either terminate the procedure or continue with LASIK. If enough stroma is available for ablation and the flap hinge is beyond the visual axis, ablation may be continued. On the other hand, if the flap hinge is within the visual axis, the ablation should be aborted.

Corneal perforation

Perforation through the cornea is a rare but devastating complication. It has been reported in older models of mechanical microkeratomes that were not properly assembled or with an inappropriate depth. Other risk factors include extremely thin corneas.

Management: Immediately de-activate the suction, remove the microkeratome, and repair the perforation in a sterile manner (in the operating room if necessary).

Femtosecond Laser-related flap complications

Vertical gas breakthrough

The mechanism by which the femtosecond laser works creates bubbles within the flap. These bubbles usually resolve with lifting of the flap but at times, vertical gas breakthrough (escape of gas bubbles from the dissection plane into the subepithelial space) or an opaque bubble layer (escape of gas bubbles into the stroma) can occur. The cause is unknown but a thin flap or a focal break in the Bowman's layer may be causative.

Management: Lift the flap cautiously and perform laser ablation.

Anterior chamber gas bubbles

The cause of gas bubbles entering the anterior chamber during FS laser-assisted flap creation is not well known, but one theory is that the gas bubbles escape from the dissection plane into the trabecular meshwork, and then into the anterior chamber. The incidence of this complication is very low and therefore risk factors have not been well established. The anterior chamber bubbles can interfere with pupillary tracking, but usually are self limiting and resolve over a short period of time.

Management: Lift the flap cautiously and perform laser ablation.

Rainbow glare

First described in 2008, this optical issue is described by patients as a "rainbow glare" when looking at white light sources. The cause is thought to be secondary to the pattern on the underside of LASIK flap resulting in light diffraction . Most cases are self-limited but for persistent symptoms, the surgeon can attempt to lift the flap and perform undersurface ablation.

Microkeratome and FS-related flap complications

Corneal Epithelial Defect

Epithelial defects are reported to occur intraoperatively at a rate of 0.6%-14%. This rate is lower with the use of femtosecond lasers. The risk factors of epithelial erosion during LASIK include

• older age,
• steep cornea,
• previous corneal trauma,
• preoperative hyperopa,
• diabetes mellitus,
• history of contact lens use
• increased corneal thickness,
• epithelial basement membrane dystrophy (EBMD), and
• type of microkeratome.

Epithelial defect can predispose to

• delayed healing,
• diffuse lamellar keratitis (DLK),
• epithelial ingrowth,
• flap striae, and
• infectious keratitis.

Prevention: limiting toxic topical medications, minimizing use of topical anesthetics, frequent use of lubricating drops, preoperative inspection of blade, and meticulous microkeratome maintenance.

Management: A bandage soft contact lens may be used for larger defects (>1 mm), and topical lubricants are beneficial until re-epithelialization occurs. In addition, topical antibiotics and steroids may be required to prevent infection.

Limbal Bleeding

Limbal hemorrhage can occur secondary to the microkeratome blade or femtosecond laser. Predisposing factors include large diameter flaps, hyperopia, or using inappropriately sized/improperly positioned suction rings. Corneal pannus (such as in chronic contact lens wearers) is also a risk factor for limbal bleeding. Limbal bleeding has been associated with delayed wound healing, sterile interface keratitis, and decreased contrast sensitivity and glare acuity.

Management: Apply gentle pressure on the oozing vessels either directly with a dry sponge, or by pushing a fold of conjunctiva over the limbal feeder vessels. Remove any visible blood in the ablation zone prior to returning the flap to its original position. After replacing the flap, phenylephrine 2.5% may be used to constrict the blood vessels. With topical phenylephrine 2.5%, keep in mind that secondary iris dilation may cause some interference with laser treatment.

Interface Debris

While creating and lifting the flap, debris can accumulate within the interface. Sources of interface debris include meibomian gland secretions, particles from sponge, talc from gloves, metallic or plastic fragments during use of the microkeratome, red blood cells, epithelial cells, and debris from tear film.

Prevention: Use an aspirating speculum, operate in a lint-free environment, drape the lashes and eyelids.

Management: Most interface debris is harmless to the patient, but if an inflammatory reaction is elicited, the flap should be lifted and irrigated, and the debris removed.

Postoperative Complications

Overcorrection and Undercorrection

Undercorrection is the most common complication after primary LASIK. Overcorrection is mostly seen after retreatment. Both are related to the ablation algorithm, nomogram, age, and the amount of refractive error.

Visual aberrations

Twenty percent of patients will report some form of visual change. Flap creation alone leads to higher-order aberrations. Some patients may suffer from visual changes such as glare, halo, or star-bursting patterns around lights, haze, and decreased contrast sensitivity. The FDA reports that visual disturbances tend to stabilize three to six months after the procedure.

Flap Fold or Striae

The risk factors for flap folds include

• excessive irrigation of flap during LASIK,
• poor repositioning of the flap at the end of procedure,
• thin flaps, and
• deep and highly myopic ablation with flap-bed mismatch.

Flap folds may be classified into macro- and microstriae.

Macrostriae

Macrostriae are full thickness, rolling stromal folds, occur because of flap malposition or slippage.

Management: If found early in the post-operative period, the flap should be immediately lifted, irrigated, and repositioned. A bandage contact lens is also recommended. After 24 hours, macrostriae may require refloating, de-epithelialization, hydration, stroking, and suturing. If folds are identified much later, surgical intervention may be required. However, if patients are asymptomatic and content with their vision, these folds can also simply be monitored.

Microstriae

Microstriae are fine folds in Bowman’s layer, occur because of mismatch of flap to new bed and often visually insignificant.

Management: Observation with aggressive lubrication, if visually significant perform refloating, stroking, and suturing.

Flap Dislocation

Flap dislocation can occur years after LASIK.

The risk factors are

• excessive lid squeezing,
• eye rubbing,
• excessive dry eye,
• presence of epithelial abrasion,
• poor intraoperative repositioning,
• excessive irrigation of flap, and
• trauma.

Prevention: Check adhesion of flap at the end of procedure, remind the patient not to squeeze or rub the eyes, and wear the shield for the first 24 hours and every night for the first week.

Management: Reposition the flap, suture the flap in the event of persistent fold, and use lubricants.

Dry Eye

Dry eye is one of the most common side effects of LASIK (incidence of 60-70%) . With flap creation, there is loss of afferent corneal nerves which leads to ocular surface issues.

Prevention: Perform a thorough exam preoperatively to identify signs of dry eye and treat aggressively with topical lubrication, cyclosporine A, and systemic treatment with oral tetracyclines and oral omega-3 fatty acids.

Management: Mild dry eye syndrome: frequent use of non-preserved artificial tears, and gels. Severe dry eye syndrome: topical cyclosporine A, topical corticosteroid, oral tetracyclines, oral omega-3 fatty acids, and punctal occlusion.

Diffuse Lamellar Keratitis (DLK)

DLK is described as a sterile inflammation of the stroma/interface that can occur in the early post-operative period. See the discussion in Diffuse Lamellar Keratitis section.

Pressure-induced Stromal Keratitis (PISK)

PISK is a late-onset interface opacity similar to DLK with a visible fluid cleft in the interface as a result of elevated IOP because of prolonged corticosteroid treatment.

Management: Rapid tapering or cessation of the corticosteroids and use of anti-glaucoma medication to lower IOP.

Central Toxic Keratitis (CTK)

See the discussion in Central Toxic Keratitis section.

Infectious Keratitis

Although quite rare, infection under a LASIK flap is one of the most vision threatening complications and must be differentiated from the sterile DLK. If presentation is within the first 2 weeks postoperatively, the most common causative organisms are gram-positive bacteria (Staphylococcus and Streptococcus species). If presentation is several weeks postoperatively, the surgeon should consider more atypical organisms (mycobacteria and fungi).

Symptoms: include decreased visual acuity, pain, photophobia, and redness. Unlike DLK (which presents on day 1 or 2 post-operatively), onset of infectious keratitis typically occurs on day 3-4 post-operatively. It also differs from DLK in that it is usually unilateral.

Differential Diagnosis: DLK (usually seen within first 24 hours after surgery and typically begins at flap periphery)

Prevention: Adequate sterilization of the instruments, preoperative treatment of blepharitis and dry eye syndrome, use of sterile surgical technique, postoperative antibiotic prophylaxis.

Management: Lift the flap, culture the interface, and irrigate with antibiotics. Start empirical fortified treatment including vancomycin (50 mg/ml), tobramycin (14 mg/ml), or gatifloxacin, moxifloxacin.

Atypical mycobacteria: topical clarithromycin (10 mg/ml), oral clarithromycin (500 mg bid), and topical amikacin (8 mg/ml).

Fungal keratitis: Natamycin (50 mg/ml), amphotericin (1.5 mg/ml).

Epithelial Ingrowth

This is the most common interface complication (with an incidence reported between 1% and 20%), however it is less common in FS-created flaps. The presentation is typically weeks-months after surgery. The risk factors are:

• poor adhesion of the flap edges,
• epithelial abrasions at the flap margin,
• buttonhole flap,
• free cap,
• ablation at the edge of stromal bed,
• epithelial irregularity at the edge of flap,
• introduction of epithelial cells during the cut, or
• insertion of instruments,
• inadequate irrigation,
• previous RK, and
• reoperation.

Two types of epithelial ingrowth recognized: isolated epithelial pearls in the interface, and epithelial sheet growing into the interface from the periphery.

Symptoms: reduced vision, irregular astigmatism, and risk of stromal melting.

Prevention: Avoid epithelial defects, remove epithelial cells and debris from the interface, and avoid wide ablation zone.

Management: No treatment is necessary for asymptomatic, isolated, or peripheral nests. If the patient is symptomatic, or if there are findings of flap melt or irregular topography, lift the flap to expose the affected area and scrape the underside of the flap and the stromal bed before repositioning the flap. In severe cases, flap amputation may be necessary.

Ectasia

See the discussion in Post Lasik Ectasia section.

Rare Complications

Ischemic optic neuropathy, retinal detachment, vitreous hemorrhage, and posterior vitreous detachment, are potential but very rare complications of LASIK, occurring in less than 0.1% of patients.