Risks and Complications of LASIK

An analysis of twelve FDA clinical trials for LASIK demonstrates that six months after LASIK, 17.5% of patients report halos, 19.7% report glare (starbursts), 19.3% have night-driving problems and 21% complain of eye dryness. Source: Bailey MD, Zadnik K. Outcomes of LASIK for myopia with FDA-approved lasers. Cornea 2007 Apr;26(3):246-54.

The public perception of LASIK is based largely on advertising, which is intended to entice patients to have surgery without disclosing risks, side effects and complications. LASIK surgeons behave more like used car salesmen than physicians, talking up LASIK benefits while downplaying the risks.

Some complications of LASIK may have disastrous consequences. LASIK complications such as dry eyes and night vision disturbances (starbursts and halos) occur frequently after LASIK.

Most prospective LASIK patients do not know how to locate unbiased, factual information concerning the risks and complications of LASIK. LASIK surgeons quote low complication rates, but what defines a "complication"? Read: The problem with LASIK complication rates

Joe R. McFarlane Jr., MD, JD: "We are also just now learning of some of the long-term complications of refractive surgery, which are being reflected in new allegations and lawsuits. For example, some patients are developing postrefractive ectasia years after the procedure; this condition not only compromises vision, but also may need to be treated with a corneal transplant". Source: EyeNet Magazine, November 2007.

In the early days of LASIK, no one knew how safe the procedure would prove to be in the long term. Now there are literally thousands of published studies on LASIK. But how reliable are studies published by LASIK surgeons? Read: Science of Refractive Surgery

By closely examining the methodology, we attempt to discern the truth about LASIK studies. Below are scientific reports and peer-reviewed studies about LASIK complications.

 

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.

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 >/=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/mum, P = 0.01), and combined ablation depth and flap thickness (RR 1.01/mum, 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.

Cohesive tensile strength of human LASIK wounds with histologic, ultrastructural, and clinical correlations.

J Refract Surg. 2005 Sep-Oct;21(5):433-45.
Schmack I, Dawson DG, McCarey BE, Waring GO 3rd, Grossniklaus HE, Edelhauser HF.

PURPOSE: To measure the cohesive tensile strength of human LASIK corneal wounds.

METHODS: Twenty-five human eye bank corneas from 13 donors that had LASIK were cut into 4-mm corneoscleral strips and dissected to expose the interface wound. Using a motorized pulling device, the force required to separate the wound was recorded. Intact and separated specimens were processed for light and electron microscopy. Five normal human eye bank corneas from 5 donors served as controls. A retrospective clinical study was done on 144 eyes that had LASIK flap-lift retreatments, providing clinical correlation.

RESULTS: The mean tensile strength of the central and paracentral LASIK wounds showed minimal change in strength over time after surgery, averaging 2.4% (0.72 +/- 0.33 g/mm) of controls (30.06 +/- 2.93 g/mm). In contrast, the mean peak tensile strength of the flap wound margin gradually increased over time after surgery, reaching maximum values by 3.5 years when the average was 28.1% (8.46 +/- 4.56 g/mm) of controls. Histologic and ultrastructural correlative studies found that the plane of separation always occurred in the lamellar wound, which consisted of a hypocellular primitive stromal scar centrally and paracentrally and a hypercellular fibrotic stromal scar at the flap wound margin. The pathologic correlations demonstrated that the strongest wound margin scars had no epithelial cell ingrowth-the strongest typically being wider or more peripherally located. In contrast, the weakest wound margin scars had epithelial cell ingrowth. The clinical series demonstrated the ability to lift LASIK flaps without complications during retreatments up to 8.4 years after initial surgery, correlating well with the laboratory results.

CONCLUSIONS: The human comeal stroma typically heals after LASIK in a limited and incomplete fashion; this results in a weak, central and paracentral hypocellular primitive stromal scar that averages 2.4% as strong as normal comeal stroma. Conversely, the LASIK flap wound margin heals by producing a 10-fold stronger, peripheral hypercellular fibrotic stromal scar that averages 28.1% as strong as normal comeal stromal, but displays marked variability.

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.

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.

Pathologic Findings in Postmortem Corneas After Successful Laser In Situ Keratomileusis.

Cornea. 24(1):92-102, January 2005.
Kramer, Theresa R MD, MBA; Chuckpaiwong, Varintorn MD; Dawson, Daniel G MD; L'Hernault, Nancy; Grossniklaus, Hans E MD; Edelhauser, Henry F PHD

Purpose: To examine the histologic and ultrastructural features of human corneas after successful laser in situ keratomileusis (LASIK).

Methods: Corneas from 48 eyes of 25 postmortem patients were processed for histology and transmission electron microscopy (TEM). The 25 patients had LASIK between 3 months and 7 years prior to death. Evaluation of all 5 layers of the cornea and the LASIK flap interface region was done using routine histology, periodic acid-Schiff (PAS)-stained specimens, toluidine blue-stained thick sections, and TEM.

Results: In patients for whom visual acuity was known, the first postoperative day uncorrected visual acuity was 20/15 to 20/30. In patients for whom clinical records were available, the postoperative corneal topography was normal and clinical examination showed a semicircular ring of haze at the wound margin of the LASIK flap. Histologically, the LASIK flap measured, on average, 142.7 [mu]m (range, 100-200). A spectrum of abnormal histopathologic and ultrastructural findings was present in all corneas. Findings at the flap surface included elongated basal epithelial cells, epithelial hyperplasia, thickening and undulations of the epithelial basement membrane (EBM), and undulations of Bowman's layer. Findings in or adjacent to the wound included collagen lamellar disarray; activated keratocytes; quiescent keratocytes with small vacuoles; epithelial ingrowth; eosinophilic deposits; PAS-positive, electron-dense granular material interspersed with randomly ordered collagen fibrils; increased spacing between collagen fibrils; and widely spaced banded collagen. There was no observable correlation between postoperative intervals and the severity or type of pathologic change except for the accumulation the electron-dense granular material.

Conclusions: Permanent pathologic changes were present in all post-LASIK corneas. These changes were most prevalent in the lamellar interface wound. These changes along with other pathologic alterations in post-LASIK corneas may change the functionality of the cornea after LASIK.