2020–2021 BCSC Basic and Clinical Science Course™
2 Fundamentals and Principles of Ophthalmology
Part IV: Biochemistry and Metabolism
Chapter 8: Cornea
The Bowman layer is immediately beneath the epithelial basal lamina and is composed of randomly packed type I and type V collagen fibers that are 30 nm in diameter. The fibers are enmeshed in a matrix consisting of proteoglycans and glycoproteins. The Bowman layer is secreted during embryogenesis by the anterior stromal keratocytes and epithelium. It is acellular and does not regenerate when damaged.
It is thought that this layer, by virtue of its acellularity and packing distribution, serves to prevent exposure of stromal keratocytes to growth factors secreted by epithelial cells, such as transforming growth factor β. This effect is notable because, in excimer laser surgery (photorefractive keratectomy [PRK] or laser subepithelial keratomileusis [LASEK]), the Bowman layer is removed, along with anterior corneal stromal tissue. Corneal haze, a potentially significant postoperative complication of these procedures, is presumably due to absence of the Bowman layer and consequent keratocyte exposure to growth factors. In LASIK, by contrast, the Bowman layer is transected but retained; central corneal haze is thus extremely rare after this procedure.
Excerpted from BCSC 2020-2021 series: Section 2 - Fundamentals and Principles of Ophthalmology. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.