On the structural origin of refractive instability and corneal haze after excimer laser keratectomy for myopia

Møller‐Pedersen, Torben

doi:10.1034/j.1600-0420.81.s237.1.x

Cited by 15 publications

(11 citation statements)

References 99 publications

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“…These findings in rabbits provide a structural explanation for the clinically observed lack of post-LASIK wound healing that allows the corneal flap to be separated from its stromal bed for an indeterminate time after surgery. 4 5 Since the rabbit cornea otherwise is known to heal aggressively (following, for example, photorefractive keratectomy or a penetrating wound), [36][37][38] LASIK provides an interesting model for studying the basic regulation of corneal wound repair and the development of fibrosis. Further insight into these important aspects is required to improve the outcome of LASIK and other corneal refractive surgical procedures.…”

Section: Discussionmentioning

confidence: 99%

Characterisation of corneal fibrotic wound repair at the LASIK flap margin

Ivarsen

Laurberg²,

Møller‐Pedersen³

2003

British Journal of Ophthalmology

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Aim: To characterise temporal changes in corneal wound repair at the LASIK flap margin. Methods: 18 rabbits received monocular LASIK and were evaluated during 6 months using slit lamp and in vivo confocal microscopy. In three corneas, the exposed stroma was stained with DTAF. At various time points, corneas were processed for histology and stained for nuclei, f-actin, ED-A fibronectin, a-smooth muscle actin, TGF-b1, TGF-b2, TGF-b receptor II, and CTGF. Results: At day 1, leucocytes migrated from the conjunctival vessels into the cornea. Near the limbus, the leucocytes were organised in long chains stretching towards the flap edge. From day 4, elongated fibroblasts migrated from the periphery to align in a circumferential band (approximately 250 mm wide) next to the flap edge. The lateral extension of this stromal band was delimited by the incisional gap in the epithelial basement membrane. TGF-b1, TGF-b2, TGF-b receptor II, and CTGF were expressed in the band from day 2. Myofibroblasts were identified at week 3 and over time a 50 mm thick layer of fibrotic matrix was deposited. Concurrently, the peripheral circumferential band became narrower (width decreasing to 33% (SD 7%) at 4 months; n = 5) and showed an increased organisation with a gradual decline in reflectivity. At all time points, keratocytes within and below the flap remained quiescent and only minimal fibrosis developed at the interface. Conclusions: Fibrotic wound repair following LASIK is restricted to a narrow band peripheral to the corneal flap edge. The lateral extension of the fibrosis is sharply delimited by the incisional gap in the epithelial basement membrane. The fibrotic wound healing at the LASIK flap margin is associated with myofibroblast transformation and wound contraction and involves a TGF-b signalling pathway. L aser in situ keratomileusis (LASIK) is a modern refractive surgical procedure that involves temporary displacement of a hinged corneal tissue flap during laser treatment of the underlying stromal bed. LASIK is associated with a high risk of complications related to the corneal flap including epithelial ingrowth, flap melting, and traumatic flap dislocation.1-4 These complications may be related to the clinically observed lack of corneal wound healing that allows the corneal flap to be separated from its stromal bed for an indeterminate time after surgery. Thus, the LASIK interface is readily accessible for re-treatment more than 1 year after the initial procedure, 5 and corneal flap dehiscence has been observed several years after uneventful surgery. 4 Using slit lamp biomicroscopy, a white reflecting band is typically observed in the corneal flap periphery after LASIK (Fig 1). 2 6 Over time, this circumferential band undergoes characteristic changes in width, texture, and reflectivity. The band is generally believed to represent corneal wound healing 2 7-10 ; however, its exact nature, localisation, and significance have not been thoroughly investigated. Using a rabbit eye model, the present study characterises temporal ch...

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Section: Discussionmentioning

confidence: 99%

Characterisation of corneal fibrotic wound repair at the LASIK flap margin

Ivarsen

Laurberg²,

Møller‐Pedersen³

2003

British Journal of Ophthalmology

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“…The small amount of scattered light produced by this tissue has in particular been extensively researched in the literature [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. All previous theories explaining corneal transparency [21][22][23][24][25][26][27] have focused on light propagation in the stromal extracellular matrix.…”

Section: Introductionmentioning

confidence: 99%

“…Smaller organelles, such as mitochondria and endoplasmic reticulum, are likely responsible for scattering at larger angles. Møller-Pedersen [10,11] studied these particular unclear aspects. McCally et al [8] presented the first measurements of light-scattering and their link to the ultrastructure of scars.…”

Section: Introductionmentioning

confidence: 99%

Measurement of correlation between transmission and scattering during wound healing in hen corneas

Mar

Martínez-García

Blanco–Mezquita

et al. 2009

Journal of Modern Optics

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The aim of this work is to provide experimental data for corneal transparency and scattering to help create a more complete model of corneal transparency. The scattered light in 96 healing hen corneas was measured for three wavelengths by a scatterometer constructed in the Optics Laboratory (The University of Valladolid, Spain). With the help of mirrors and beamsplitters, the light from the three lasers is directed toward the cell containing the sample to be measured. The measured scattered light varies between six orders of magnitude. Corneal transmissivity, mean cosine of a scattering angle, and angular distribution of scattered light were all computed. The total transmitted light remained practically constant over a wide range of light values transmitted in a forward direction (direct transmissivity). The value of the mean cosine of the scattering direction is very close to the unit (g 4 0:98), even in corneas with high opacities. The behavior of g indicates that even damaged corneas evidence extremely small scattering, compared to other biological tissues. The transmission reduction of each cornea is related to an increase in scattered light. In all cases, scattered light is concentrated at very small angles. This behavior is acceptable in corneas that are healthy or which evidence small lesions, but remains in corneas that are severely injured.

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“…For example, the creation of a lamellar flap during the LASIK procedure increases the risk of intraoperative complications, such as irregular cuts, epithelial ingrowth, and infectious keratitis [2,3]. Postoperative scarring and haze is more common after PRK than LASIK [4].…”

Section: Introductionmentioning

confidence: 99%