Dry Eyes after LASIK

Dry eye is the most common complication of LASIK eye surgery. Dry eyes after LASIK may be a life-altering, chronic condition. Refractive surgeons are aware that LASIK induces dry eye, yet patients are not receiving full informed consent as to the chronic nature and severity of this condition. Dry eye may interfere in the healing process and lead to corneal erosions and refractive regression.

Patient suffers severe dry eye pain after LASIK

The FDA website warns that LASIK patients may develop "severe dry eye syndrome" which "may be permanent".

In August, 2002, LASIK patient David Shell testified before the FDA Ophthalmic Devices Panel:
“My LASIK dry eye is  not a minor problem, as  downplayed by some ophthalmologists. It's a disability.  I  estimate that I am blind approximately 10  percent  of the time due to my eyes being  closed  because of the pain.  At the time of my surgery, I  was  told only a small number  of patients experience a complication  from  this  procedure.  There  is substantial  evidence  that shows this crippling side effect to be relatively common.” 

Research and discussion of dry eyes after LASIK can be found at this link: Dry Eyes after LASIK

What is dry eye?

The continuous production and drainage of tears is important to the eye's health. Tears keep the eye moist, help wounds heal, and protect against eye infection. In people with dry eye, the eye produces fewer or less quality tears and is unable to keep its surface lubricated and comfortable.

The tear film consists of three layers--an outer, oily (lipid) layer that keeps tears from evaporating too quickly and helps tears remain on the eye; a middle (aqueous) layer that nourishes the cornea and conjunctiva; and a bottom (mucin) layer that helps to spread the aqueous layer across the eye to ensure that the eye remains wet. As we age, the eyes usually produce fewer tears. Also, in some cases, the lipid and mucin layers produced by the eye are of such poor quality that tears cannot remain in the eye long enough to keep the eye sufficiently lubricated.

The main symptom of dry eye is usually a scratchy or sandy feeling as if something is in the eye. Other symptoms may include stinging or burning of the eye; episodes of excess tearing that follow periods of very dry sensation; a stringy discharge from the eye; and pain and redness of the eye. Sometimes people with dry eye experience heaviness of the eyelids or blurred, changing, or decreased vision, although loss of vision is uncommon.
Source: National Eye Institute

What causes dry eyes after LASIK?

Research points to corneal nerve damage during surgery as the cause of dry eyes after LASIK. The nerves of the cornea that play a vital role in tear production are severed when the flap is cut. A medical study published in 2004 reveals that three years after LASIK the corneal nerves have not recovered (see below). Read more

Frequency of post-LASIK dry eye

Symptoms of dryness may occur in more than 50% of patients, with other complications such as fluctuating vision, decreased best spectacle-corrected visiual acuity, and severe discomfort occurring in approximately 10% of patients.
Source: Ambrósio R Jr, Tervo T, Wilson SE. LASIK-associated dry eye and neurotrophic epitheliopathy: pathophysiology and strategies for prevention and treatment. J Refract Surg. 2008 Apr;24(4):396-407.

Approximately 20% of patients experienced dryness symptoms that were worse or significantly worse than preoperative dryness. (FDA clinical trials, six months post-op data).
Bailey MD, Zadnik K. Outcomes of LASIK for myopia with FDA-approved lasers. Cornea. 2007 Apr;26(3):246-54.

The incidence of dry eye gradually decreased over the observation period in both groups to a 36.36% overall incidence and a 41.18% incidence in the superior-hinge group at 6 months.
Source: De Paiva et al. The incidence and risk factors for developing dry eye after myopic LASIK.
Am J Ophthalmol. 2006 Mar;141(3):438-45.

Marguerite McDonald, MD: "With LASIK, roughly half of my patients had dry eye complaints after surgery - and in about half of these, the symptoms were severe." RefractiveEyecare.com December 2005

LASIK-induced dry eyes may lead to refractive regression. Read more

Read the personal experience of a patient with post-LASIK dry eye Click here

Abstracts of medical studies regarding post-LASIK dry eye:

Corneal reinnervation after LASIK: prospective 3-year longitudinal study.
Invest Ophthalmol Vis Sci. 2004 Nov;45(11):3991-6.
Calvillo MP, McLaren JW, Hodge DO, Bourne WM.
Department of Ophthalmology, Mayo Clinic College of Medicine, Rochester, MN 55905, USA.

PURPOSE: To measure the return of innervation to the cornea during 3 years after LASIK.

METHODS: Seventeen corneas of 11 patients who had undergone LASIK to correct myopia from -2.0 D to -11.0 D were examined by confocal microscopy before surgery, and at 1, 3, 6, 12, 24, and 36 months after surgery. In all available scans, the number of nerve fiber bundles and their density (visible length of nerve per frame area), orientation (mean angle), and depth in the cornea were measured.

RESULTS: The number and density of subbasal nerves decreased >90% in the first month after LASIK. By 6 months these nerves began to recover, and by 2 years they reached densities not significantly different from those before LASIK. Between 2 and 3 years they decreased again, so that at 3 years the numbers remained <60% of the pre-LASIK numbers (P <0.001). In the stromal flap most nerve fiber bundles were also lost after LASIK, and these began recovering by the third month, but by the third year they did not reach their original numbers (P <0.001). In the stromal bed (posterior to the LASIK flap interface), there were no significant changes in nerve number or density. As the subbasal nerves returned, their mean orientation did not change from the predominantly vertical orientation before LASIK. Nerve orientation in the stromal flap and the stromal bed also did not change.

CONCLUSIONS: Both subbasal and stromal corneal nerves in LASIK flaps recover slowly and do not return to preoperative densities by 3 years after LASIK. The numbers of subbasal nerves appear to decrease between 2 and 3 years after LASIK. The orientation of the regenerated subbasal nerves remains predominantly vertical.

Change to corneal morphology after refractive surgery (myopic laser in situ keratomileusis) as viewed with a confocal microscope.
Optom Vis Sci. 2003 Oct;80(10):690-7.
Perez-Gomez I, Efron N.
Department of Optometry and Neuroscience, UMIST, Manchester, United Kingdom. i.perez-gomez@umist.ac.uk

PURPOSE: This study aimed to look at morphological changes induced by myopic laser in situ keratomileusis (LASIK) in the human cornea using the confocal microscope and to investigate the link between these changes and alterations to corneal sensitivity.

METHODS: An in vivo slit-scanning real-time confocal microscope (Tomey ConfoScan P4, Erlangen, Germany) fitted with an Achroplan 40x/0.75 NA immersion objective and a Cochet-Bonnet esthesiometer were used to examine the morphology and sensitivity of the central corneas of six subjects (12 eyes) at an initial visit (before surgery), and at 1 week, 1 month, 3 months, and 6 months after LASIK for myopia.

RESULTS: Keratocyte density anterior to the flap interface showed differences between visits (p < 0.0001) and was found to be lower than at the initial visit at 1 week, 1 month, 3 months, and 6 months. Microfolds were noted at the level of the anterior limiting membrane in 11 of 12 eyes after surgery at all visits. Highly reflective flap interface particles were seen in all eyes at all visits after surgery. The subepithelial nerve fiber layer was clearly visible before surgery but could not be imaged in any of the eyes after surgery. Short, unconnected nerve fibers were observed 3 months after surgery; these appeared to form anastomosing interconnections after 6 months. Postsurgical corneal sensitivity was reduced during the first 3 months and recovered to presurgical levels after 6 months.

CONCLUSION: LASIK showed a decrease in anterior keratocyte density and microfolds in the anterior limiting membrane, and reflective particles were observed at the flap interface. Corneal sensitivity was depressed during the first 6 months after LASIK surgery; this time course paralleled the appearance of nerve regeneration during this period. Confocal microscopy is capable of providing interesting new insights into the effects of refractive surgery on corneal morphology.

The incidence and risk factors for developing dry eye after myopic LASIK.
Am J Ophthalmol. 2006 Mar;141(3):438-45.
De Paiva CS, Chen Z, Koch DD, Hamill MB, Manuel FK, Hassan SS, Wilhelmus KR, Pflugfelder SC.
Department of Ophthalmology, Cullen Eye Institute, Baylor College of Medicine, 6565 Fannin Street, NC 205, Houston, TX 77030, USA.

PURPOSE: To determine the incidence of dry eye and its risk factors after myopic laser-assisted in situ keratomileusis (LASIK).

DESIGN: Single-center, prospective randomized clinical trial of 35 adult patients, aged 24 to 54 years, with myopia undergoing LASIK.

METHODS: setting and study population: Participants were randomized to undergo LASIK with a superior or a nasal hinge flap. They were evaluated at 1 week and 1, 3, and 6 months after surgery. intervention: Bilateral LASIK with either a superior-hinge Hansatome microkeratome (n = 17) or a nasal-hinge Amadeus microkeratome (n = 18). main outcome measures: The criterion for dry eye was a total corneal fluorescein staining score > or =3. Visual acuity, ocular surface parameters, and corneal sensitivity were also analyzed. Cox proportional-hazard regression was used to assess rate ratios (RRs) with 95% confidence intervals.

RESULTS: The incidence of dry eye in the nasal- and superior-hinge group was eight (47.06%) of 17 and nine (52.94%) of 17 at 1 week, seven (38.89%) of 18 and seven (41.18%) of 17 at 1 month, four (25%) of 16 and three (17.65%) of 17 at 3 months, and two (12.50%) of 16 and six (35.29%) of 17 at 6 months, respectively. Dry eye was associated with level of preoperative myopia (RR 0.88/each diopter, P = .04), laser-calculated ablation depth (RR 1.01/microm, P = 0.01), and combined ablation depth and flap thickness (RR 1.01/microm, P = 0.01).

CONCLUSIONS: Dry eye occurs commonly after LASIK surgery in patients with no history of dry eye. The risk of developing dry eye is correlated with the degree of preoperative myopia and the depth of laser treatment.

Excerpts from the full text:

"The incidence of dry eye for the nasal-hinge group was zero (0%) of 18 at baseline, eight (47.06%) of 17 at 1 week, five (27.78%) of 18 at 1 month, four (25%) of 16 at 3 months, and five (31.25%) of 16 at 6 months. The incidence in eyes with superior hinge flap was zero (0%) of 17, nine (52.94%) of 17, four (23.53%) of 17, four (23.53%) of 17, and seven (41.18%) of 17 at baseline, 1 week, 1 month, 3 months, and 6 months, respectively."

"The incidence of dry eye gradually decreased over the observation period in both groups to a 36.36% overall incidence and a 41.18% incidence in the superior-hinge group at 6 months."

"On the basis of these findings, patients should be counseled about the risk of developing dry eye after LASIK..."

"Dry eye occurs commonly after laser-assisted in situ keratomileusis (LASIK) surgery in patients with no history of dry eye."

Reinnervation in the cornea after LASIK.
Invest Ophthalmol Vis Sci. 2002 Dec;43(12):3660-4.
Lee BH, McLaren JW, Erie JC, Hodge DO, Bourne WM.
Department of Ophthalmology, Mayo Clinic, Rochester, Minnesota, USA.

PURPOSE: Nerve fibers in the cornea are disrupted by photorefractive procedures. In this study, the denervation and reinnervation of human central corneas were evaluated by sequential, quantitative measurements of nerves viewed by confocal microscopy in vivo during the first year after LASIK.

METHODS: Seventeen eyes were studied of 11 patients who had undergone LASIK to correct myopia from -2.0 D to -11.0 D. Eyes were treated with an excimer laser with a planned 180- micro m flap. Central corneas were scanned throughout their full thicknesses by confocal microscopy before and at 1 week and 1, 3, 6, and 12 months after LASIK. Nerve fiber bundles appeared as bright, well-defined, linear structures that were sometimes branched and usually appeared in several consecutive frames. The number of nerve fiber bundles per scan in two to eight scans per eye per visit was determined in the subbasal region, the full-thickness stroma, the stromal flap (layer between the most anterior keratocyte and the flap interface), and the stromal bed (layer between the flap interface and the endothelium).

RESULTS: In the subbasal region, the number of nerve fiber bundles decreased by more than 90% 1 week after LASIK and was significantly lower at all times after surgery than it was before surgery (P < 0.001). It increased 6 and 12 months after LASIK, but remained less than half of the preoperative value. In the stromal flap, the number of nerves at all times after surgery was also significantly less than before surgery (P < 0.001) and did not increase significantly by 1 year. In the stromal bed, there were no significant differences among any of the nerve measurements before and after LASIK (P = 0.24).

CONCLUSIONS: In the corneal flap, the number of subbasal and stromal nerve fiber bundles decreases by 90% immediately after LASIK. During the first year after LASIK, subbasal nerve fiber bundles gradually return, although by 1 year their number remains less than half of that before LASIK.