Marcella Q. Salomao, MD and Steven E. Wilson, MD. Corneal Molecular and Cellular Biology Update for the Refractive Surgeon. J Refract Surg. 2009 May

Source: Source: Heickell AG, Vesaluoma MH, Tervo TM, Vannas A, Krootila K. Late traumatic dislocation of laser in situ keratomileusis flaps. J Cataract Refract Surg. 2004 Jan;30(1):253-6.

Thomas and Tanzer seem to say that LASIK flaps can't be dislocated by a single strike by a tree branch...



Source: Thomas KE, Tanzer DJ. Visual acuity recovery after late traumatic femtosecond laser in situ keratomileusis flap loss. J Cataract Refract Surg. 2009 Jun;35(6):1134-7.

So, I looked up the full text of the article that they referenced...



Source: Laurent JM, Schallhorn SC, Spigelmire JR, Tanzer DJ. Stability of the laser in situ keratomileusis corneal flap in rabbit eyes. J Cataract Refract Surg. 2006 Jun;32(6):1046-51.

Can you believe what they do to these rabbits? I also wanted to see what other case studies reported about flap dislocation by a tree branch...



Source: Heickell AG, Vesaluoma MH, Tervo TM, Vannas A, Krootila K. Late traumatic dislocation of laser in situ keratomileusis flaps. J Cataract Refract Surg. 2004 Jan;30(1):253-6.



Source: Mifflin M, Kim M. Laser in situ keratomileusis flap dehiscence 3 years postoperatively. J Cataract Refract Surg. 2002 May;28(5):733-5.

I would recommend that military members who have LASIK watch out for tree branches.

Source: Varssano D, Waisbourd M, Berkner L, Regenbogen M, Hazarbassanov R, Michaeli A. Late-onset laser in situ keratomileusis-related corneal ulcer--a case series. Cornea. 2009 Jun;28(5):586-8.

Source: J Cataract Refract Surg. 2003 Apr;29(4):808-20. Histological and immunohistochemical findings after laser in situ keratomileusis in human corneas. Philipp WE, Speicher L, Göttinger W.

Ursea R, Feng MT. Traumatic Flap Striae 6 Years After LASIK: Case Report and Literature Review. J Refract Surg. 2009 Dec 28:1-7. doi: 10.3928/1081597X-20091209-02.

PURPOSE: To report a case of traumatic flap striae without flap dislocation 6 years after LASIK and provide a literature review of surgical flap striae, late traumatic flap striae, and their management.

METHODS: A 28-year-old man presented with late traumatic flap striae without concurrent flap dislocation, which closely approximated the longest reported interval between LASIK and the development of flap striae.

RESULTS: In the absence of flap dislocation, the finding of striae alone was subtle and went undetected initially. The flap was successfully refloated, stretched, and smoothed with recovery of 20/20 vision.

CONCLUSIONS: Traumatic LASIK flap complications may occur many years after the original procedure. This report presents the first case of late traumatic flap striae without concurrent flap dislocation. Proper management can restore good visual function.

From the full text:

The LASIK flap remains vulnerable to late striae formation in the context of trauma and flap dislocation. Although reports of late traumatic striae are fortunately rare, they suggest that flaps remain at risk for months to years after surgery... Six uneventful years after LASIK, he was punched in the right eye, which resulted in pain and immediate decreased vision... Slit-lamp examination revealed previously unseen oblique wrinkles in the central flap, bisecting the flap from 2 o’clock to 7 o’clock, and in the periphery without exposed stromal bed. He was treated with aggressive artificial tear lubrication and referred to our office 25 days after initial trauma for management of the flap striae and astigmatism... Delayed trauma has been shown to cause flap defects, demonstrating that LASIK flaps remain vulnerable to traumatic dehiscence and dislocation even 6 or 7 years after surgery... Diminished wound healing at the LASIK flap–bed interface prevents loss of corneal transparency but also weakens flap adhesion... These findings are consistent with the clinical observation that LASIK flaps are easily lifted once fibrous adhesions at peripheral flap edges are interrupted, even many years after LASIK. Furthermore, if interface transparency is indicative of absent wound healing, one might expect that the interface remains a potential space and flap adhesion is impaired for the lifetime of the flap... Minimal flap shifts can cause striae and we speculate that these may occur with the recruitment of tissue laxity from elsewhere, perhaps due to persistence of the tenting effect, poor interface healing in the central optical zone, or both... Nevertheless, the best course of action remains prevention. It is imperative that late traumatic flap complications should be discussed with prospective LASIK patients. Military, law enforcement, and contact sport personnel should be counseled to consider surface ablation or wear eye protection. Regarding the latter, however, we recommend that safety counseling be broadened to all patients in light of the mundane mechanisms of injury seen and the random nature of trauma. Given the growing evidence for chronic flap vulnerability and the relative youth of many LASIK recipients, long-term risks are increasingly relevant.

Arch Ophthalmol. 2010 Apr;128(4):426-36.

Correlation between epithelial ingrowth and basement membrane remodeling in human corneas after laser-assisted in situ keratomileusis.

Fournié PR, Gordon GM, Dawson DG, Malecaze FJ, Edelhauser HF, Fini ME.

Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida, USA. fournie.p@chu-toulouse.fr

Abstract

OBJECTIVE: To further investigate the hypothesis that epithelial ingrowth in human corneas after laser-assisted in situ keratomileusis (LASIK) correlates with basement membrane remodeling, as suggested by the presence of matrix metalloproteinase 9 around epithelial cells in the lamellar scar.

METHODS: Immunohistochemical analysis and transmission electron microscopy were applied to human postmortem corneas with post-LASIK epithelial ingrowth.

RESULTS: Epithelial ingrowth into the flap margin was observed in 8 of 18 corneas (44%). Matrix metalloproteinase 9 immunolocalized around ingrown epithelium in 6 of these 8 corneas (75%). There was a positive correlation between the presence of matrix metalloproteinase 9 at the wound margin and discontinuities in the basement membrane, as determined by laminin and beta(4) integrin immunofluorescence. Transforming growth factor beta2 was present into the stroma of some corneas with epithelial ingrowth and interrupted basement membrane, suggesting some degree of epithelial-stromal interaction. Transmission electron microscopy confirmed large areas of remodeled basement membrane along ingrown epithelial cells.

CONCLUSIONS: The neo-basement membrane components underlying the ingrown cells in human corneas with epithelial ingrowth after LASIK appear to be partially disassembled. Epithelial-stromal interaction over time may be related to prolonged wound healing remodeling, which calls into question the stability of the flap.

__________

Layperson's interpretation:

1. 18 corneas which had undergone LASIK were examined after death of the patient.

2. Almost half of these corneas exhibited epithelial ingrowth.

3. Examinations utilizing the electron microscope revealed alteration of the relationship between the outer corneal layer (epithelium) and the underlying corneal tissue (stroma). This altered relationship may be due to prolonged wound healing which calls into question the stability of the lasik flap.