LASIK Educational Material
Laser Eye Surgery
Risks and Complications - Part Two
Part One (on separate page)Intra-operativePart Two
Post-operativePart Three (on a new page)
Over-correction, Under-correction or RegressionNight or dim-light vision complications
Potential complications can be divided into two distinct categories:
· Intra-operative - occurring during the procedure
· Post-operative - occurring during the healing phase
Surgical complications associated with the healing that occurs after the patient leaves the operating room. (Click on link or scroll down)
Diffuse lamellar keratitis (DLK)
The CRS-USA LASIK Study noted that overall, 5.8% of LASIK patients experienced complications at the three-month follow up period that did not occur during the procedure itself.
These complications included corneal edema (0.6%), corneal scarring (0.1%), persistent epithelial defect (0.5%), significant glare (0.2%), persistent discomfort or pain (0.5%), interface epithelium (0.6%), cap thinning (0.1%) and interface debris (3.2%).
It is important to note that interface debris - retained metallic particles, lint, etc. under the flap - almost always causes no harm to the health or vision of the eye. None of these complications resulted in a loss of two or more lines of BCVA, and there were no infections among the study population.
Keep in mind that many advances have been made since then. A more recent study of 598 eyes noted post-operative complications in 0.9% of cases.
Diffuse lamellar keratitis (DLK)
Diffuse lamellar keratitis is a unique and relatively uncommon post-operative condition following LASIK. Non-severe forms have been estimated in less than 1% of cases; severe cases comprise an even lesser amount.
A number of names including Sands of the Sahara have been used to describe this condition, which is characterized by an accumulation of inflammatory cells under the flap. The condition usually appears at one to three days after LASIK. However, there have been reports of late onset DLK. Multiple causes have been hypothesized, but no single explanation accounts for all cases.
At the early stages of this condition, there would most likely be no discernable symptoms, and only an examination by your doctor could reveal its existence. When caught early, the inflammation associated with DLK is easy to treat.
Approximately 80% of DLK will clear up within the first 24 to 48 hours, although it could take several weeks until it completely subsides.
DLK can be treated without visual loss when it is detected and treated early. Therefore it is imperative that you maintain your surgeon's recommended post-operative follow-up examination schedule.
Carefully review your immediate post-operative expectations with Dr. Cutarelli prior to your surgery. Review your follow-up schedule and all post-surgical instructions. Then, if you notice something about your vision that deviates from Dr. Cutarelli's expectations, notify him immediately.
Flap Striae (folds or wrinkles)
Flap striae are wrinkles or folds in the flap after LASIK surgery. Minor flap striae usually do not interfere with vision. In such cases, treatment is unnecessary. Occasionally, the striae are serious enough to decrease visual acuity and intervention is necessary.
To remove the striae, the flap might be lifted, gently smoothed out, and then laid back down in the proper position. In cases of persistent striae, sutures may be necessary.
According to a study involving 1019 eyes, 11 eyes experienced folds in the flap that required repositioning because of poor vision. The average postoperative time for repositioning was six days. In one eye, the folds persisted to the next day, so the flap was repositioned again and sutured.
There are a number of causes of striae. Sometimes, rubbing the eyelids before the flap has had a chance to bond can cause subtle wrinkles. You can significantly reduce this risk by keeping your hands away from your eyes for several weeks after surgery.
Sometimes, striae form without an apparent cause. They seem more common in very high myopes than in other patients.
Epithelial ingrowth is a condition in which epithelial cells, which normally cover the surface of the cornea, grow beneath the flap. Most epithelial ingrowth does not affect vision and does not require treatment.
One study of 1013 eyes demonstrated a 14.7% incidence rate, with 1.7% of eyes requiring surgical removal because it interfered with vision.
Another study of 783 eyes noted only 3 eyes experienced this complication. Another study of 589 eyes noted that peripheral epithelial ingrowth occurred in 4 cases (0.6%).
In such cases, many doctors will simply leave the ingrowth alone and monitor it at post-operative visits. However, in about 1-2% (of the cases), epithelial ingrowth occurs within the field of vision or affects an area wide enough to require surgical treatment or removal.
Central visually significant epithelial ingrowth can appear as early as 1-2 days post-operatively, but most often appear at 1-3 months post-operatively. Left unattended, the cells that characterize visually significant epithelial ingrowth can release enzymes that melt the flap, causing vision loss. Therefore, it is important that you attend all follow-up visits with Dr. Cutarelli, especially for the first 6 months post-operatively.
Treatment usually involves prescribed eye drops to minimize the effects. At other times a more aggressive approach will be necessary. Removing the epithelial cells is a relatively simple procedure.
The flap is lifted, the exposed interface surfaces are wiped, and the flap is then carefully replaced. In rare cases where the epithelial ingrowth persists despite such removals, sutures may be required to secure the flap down and ensure that ingrowth cannot re-occur.
It is not uncommon to experience some symptoms of dry eyes post-operatively; especially during the first few weeks while the majority of corneal healing takes place.
The symptoms can vary widely - from being relatively asymptomatic, to intermittent dryness at certain times during the day, to feeling the typical dry sensation much or all of the day, sometimes accompanied by blurry vision or an increase in glare and halos. When dry eye is treated, those symptoms typically diminish.
Clinical dry eye is comparatively easy to diagnose and the great majority of patients respond well to treatment options ranging from using preservative-free eye drops to the insertion of punctal plugs, depending on the severity of the case. For almost all patients, dry eye symptoms gradually subside over the first few weeks or months after LASIK surgery.
As early as December 1999, ophthalmologists were paying attention to the possible connection between LASIK and dry eye. At the 1999 joint meeting of the American Academy of Ophthalmology and the Pan-American Association of Ophthalmology, the results of a survey of 550 patients after LASIK were reported. Forty to fifty percent noted experiencing dry eyes at some time of the day 3 months post-operatively. Dr. Richard Lindstrom noted that while the overall frequency of complications after LASIK is decreasing, the incidence of dry eye after LASIK is increasing. Dr. Roger Steinert supported Dr. Lindstrom's assertion and provided a possible explanation:
- Some patients seek LASIK precisely because they are contact lens intolerant, and such intolerance is often indicative of dry eyes
Dr. Marguerite McDonald noted several other possible explanations for the increased frequency of this condition post-operatively:
- Use of post-operative steroids after LASIK may exacerbate pre-existing dry eye
- Previous contact lens wear disrupts normal corneal physiology
- Hormonal changes during menopause or birth control pills can cause dry eye
- Surgery itself may cause dry eye by cutting the nerves of the central cornea or damaging cilia
Since then, several studies have demonstrated that some patients may experience a decrease in corneal sensation following LASIK for the first six months following the procedure as the nerves of the cornea regenerate.
Corneal sensation is characterized by a feedback loop. When the eye is dry, a message is sent to the brain. The brain then stimulates the eye's lacrimal glands to produce tears. However, creating the flap cuts the nerves of the cornea. For some eyes, this process temporarily affects the cornea's ability to respond to dryness. When corneal sensation decreases, the feedback loop is disrupted, and the eye will experience dry eye symptoms.
Dry eye symptoms may exist for patients for several months following LASIK, even if there were no symptoms or signs of dry eye prior to surgery. Those patients who have severe conditions pre-operatively need to be aware that, because surgery can exacerbate the symptoms, they may be deemed ineligible for surgery.
Continue to: Risks, Part 3