Corneal epithelial basement membrane: Structure, function and regeneration.

Basement membranes are highly specialized extracellular matrices. More than providing scaffolds, basement membranes are recognized as dynamic and versatile structures that modulate cellular responses to regulate tissue development, function, and repair. Increasing evidence suggests that, in addition to providing structural support to adjacent cells, basement membranes serve as reservoirs and modulators of growth factors that direct and fine-tune cellular functions.

The Impact of Photorefractive Keratectomy and Mitomycin C on Corneal Nerves and Their Regeneration.

Purpose: To determine how photorefractive keratectomy (PRK) and mitomycin C (MMC) affect corneal nerves and their regeneration over time after surgery.

Methods: Twenty-eight New Zealand rabbits had corneal epithelial scraping with (n = 3) and without (n = 3) MMC 0.02% or -9.

The Corneal Basement Membranes and Stromal Fibrosis.

Purpose: The purpose of this review was to provide detailed insights into the pathophysiology of myofibroblast-mediated fibrosis (scarring or late haze) after corneal injury, surgery, or infection.

Method: Literature review.

Results: The epithelium and epithelial basement membrane (EBM) and/or endothelium and Descemet's basement membrane (BM) are commonly disrupted after corneal injuries, surgeries, and infections.

Fibrocyte migration, differentiation and apoptosis during the corneal wound healing response to injury.

The aim of this study was to determine whether bone marrow-derived fibrocytes migrate into the cornea after stromal scar-producing injury and differentiate into alpha-smooth muscle actin (αSMA) + myofibroblasts. Chimeric mice expressing green fluorescent protein (GFP) bone marrow cells had fibrosis (haze)-generating irregular phototherapeutic keratectomy (PTK). Multiplex immunohistochemistry (IHC) for GFP and fibrocyte markers (CD34, CD45, and vimentin) was used to detect fibrocyte infiltration into the corneal stroma and the development of GFP+ αSMA+ myofibroblasts.

Femtosecond Lasers and Corneal Surgical Procedures.

Our purpose is to present a broad review about the principles, early history, evolution, applications, and complications of femtosecond lasers used in refractive and nonrefractive corneal surgical procedures. Femtosecond laser technology added not only safety, precision, and reproducibility to established corneal surgical procedures such as laser in situ keratomileusis (LASIK) and astigmatic keratotomy, but it also introduced new promising concepts such as the intrastromal lenticule procedures with refractive lenticule extraction (ReLEx). Over time, the refinements in laser optics and the overall design of femtosecond laser platforms led to it becoming an essential tool for corneal surgeons.

Injury and defective regeneration of the epithelial basement membrane in corneal fibrosis: A paradigm for fibrosis in other organs?

Myofibroblast-mediated fibrosis is important in the pathophysiology of diseases in most organs. The cornea, the transparent anterior wall of the eye that functions to focus light on the retina, is commonly affected by fibrosis and provides an optimal model due to its simplicity and accessibility. Severe injuries to the cornea, including infection, surgery, and trauma, may trigger the development of myofibroblasts and fibrosis in the normally transparent connective tissue stroma.

Epithelial basement membrane injury and regeneration modulates corneal fibrosis after pseudomonas corneal ulcers in rabbits.

The purpose of this study was to investigate whether myofibroblast-related fibrosis (scarring) after microbial keratitis was modulated by the epithelial basement membrane (EBM) injury and regeneration. Rabbits were infected with Pseudomonas aeruginosa after epithelial scrape injury and the resultant severe keratitis was treated with topical tobramycin. Corneas were analyzed from one to four months after keratitis with slit lamp photos, immunohistochemistry for alpha-smooth muscle actin (α-SMA) and monocyte lineage marker CD11b, and transmission electron microscopy.

Regeneration of Defective Epithelial Basement Membrane and Restoration of Corneal Transparency After Photorefractive Keratectomy.

Purpose: To study regeneration of the normal ultrastructure of the epithelial basement membrane (EBM) in rabbit corneas that had -9.00 D photorefractive keratectomy (PRK) and developed late haze (fibrosis) with restoration of transparency over 1 to 4 months after surgery and in corneas that had incisional wounds.

Methods: Twenty-four rabbits had one of their eyes included in one of the two procedure groups (-9.

EBM regeneration and changes in EBM component mRNA expression in stromal cells after corneal injury.

Purpose: To investigate the production of the epithelial basement membrane (EBM) component mRNAs at time points before lamina lucida and lamina densa regeneration in anterior stromal cells after corneal injury that would heal with and without fibrosis.

Methods: Rabbit corneas were removed from 2 to 19 days after -4.5D or -9.

Phototherapeutic Keratectomy: Science and Art.

Purpose: To describe, with videos, the principles of excimer laser phototherapeutic keratectomy (PTK) for the treatment of corneal scars, corneal surface irregularity, and recurrent corneal erosions.

Methods: Depending on the pathology in a treated cornea, the epithelium is removed either by transepithelial PTK ablation with the excimer laser or thorough scraping with a scalpel blade. Stromal PTK can be performed with or without photorefractive keratectomy (PRK), depending on the refractive status of both eyes.

OCT Study of the Femtosecond Laser Opaque Bubble Layer.

Purpose: To characterize the location and regularity of the opaque bubble layer (OBL) in the corneal stroma after femtosecond laser-assisted LASIK (FS-LASIK) flap generation.

Methods: In this prospective study, 30 eyes of 15 patients who had FS-LASIK surgery for myopia, astigmatism, and/or hyperopia were included. Screen captures were obtained at the end of the flap creation and the eyes with hard type OBL were immediately imaged with anterior segment optical coherence tomography.

Corneal Collagen Cross-linking in Advanced Keratoconus: A 4-Year Follow-up Study.

Purpose: To analyze the safety and efficacy of standard corneal collagen cross-linking (CXL) in advanced cases of progressive keratoconus after 4 years of follow-up.

Methods: A retrospective case series of patients with advanced progressive keratoconus (stages 3 and 4 of Amsler-Krumeich classification) underwent standard CXL treatment. The parameters examined were changes in uncorrected visual acuity (UDVA), corrected visual acuity (CDVA), keratometry values (mean, flat, steep, and apical), pachymetry, and endothelial cell count at the baseline and at 12, 24, and 48 months postoperatively.

Corneal Molecular and Cellular Biology for the Refractive Surgeon: The Critical Role of the Epithelial Basement Membrane.

Purpose: To provide an overview of the recent advances concerning the corneal molecular and cellular biology processes involved in the wound healing response after excimer laser surface ablation and LASIK surgery.

Methods: Literature review.

Results: The corneal wound healing response is a complex cascade of events that impacts the predictability and stability of keratorefractive surgical procedures such as photorefractive keratectomy and LASIK.

Femtosecond Laser-Assisted LASIK Flap Complications.

Purpose: To discuss intraoperative and postoperative femtosecond laser-assisted LASIK flap complications and their management.

Methods: Review of published literature.

Results: Flap creation is a critical step in LASIK.

Differential expression of epithelial basement membrane components nidogens and perlecan in corneal stromal cells in vitro.

Purpose: The purpose of this study was to examine the expression of corneal epithelial basement membrane (EBM) components in different corneal stromal cell types. In vitro model systems were used to explore the expression of EBM components nidogen-1, nidogen-2, and perlecan that are the primary components in the lamina lucida and the lamina densa that defectively regenerate in corneas with stromal opacity after in -9.0 D photorefractive keratectomy (PRK).

Accelerated Corneal Collagen Cross-linking for Postoperative LASIK Ectasia: Two-Year Outcomes.

Purpose: To evaluate the effectiveness and safety of accelerated corneal collagen cross-linking for postoperative LASIK ectasia after 2 years.

Methods: A prospective, single-center case series was performed with patients treated for postoperative LASIK ectasia. All eyes underwent accelerated corneal collagen cross-linking (CCL-Vario Crosslinking; Peschke Meditrade GmbH, Zurich, Switzerland) at 9 mW/cm(2) for 10 minutes.

Epithelial basement membrane proteins perlecan and nidogen-2 are up-regulated in stromal cells after epithelial injury in human corneas.

The epithelial basement membrane (BM) is a specialized extracellular matrix that has been shown to have a critical role in corneal development, wound healing, and disease. Although the epithelial BM contributes to corneal homeostasis, relatively little is know about non-epithelial production of its components that may be important in defective regeneration of the epithelial basement membrane associated with opacity after photorefractive keratectomy. The purpose of the current study was to investigate stromal production of corneal epithelial BM proteins in wounded human corneas using immunohistochemistry.