Abstract
Keratoconus is the most common primary corneal ectasia characterized by progressive focal thinning. Patients experience increased irregular astigmatism, decreased visual acuity and corneal sensitivity. Corneal collagen crosslinking (CXL), a minimally invasive procedure, is effective in halting disease progression. Historically, keratoconus research was confined to ex vivo settings. In vivo confocal microscopy (IVCM) has been used to examine the corneal microstructure clinically. In this review, we discuss keratoconus cellular changes evaluated by IVCM before and after CXL. Cellular changes before CXL include decreased keratocyte and nerve densities, disorganized subbasal nerves with thickening, increased nerve tortuosity and shortened nerve fibre length. Repopulation of keratocytes occurs up to 1 year post procedure. IVCM also correlates corneal nerve status to functional corneal sensitivity. Immediately after CXL, there is reduced nerve density and keratocyte absence due to mechanical removal of the epithelium and CXL effect. Nerve regeneration begins after 1 month, with nerve fibre densities recovering to pre-operative levels between 6 months to 1 year and remains stable up to 5 years. Nerves remain tortuous and nerve densities are reduced. Corneal sensitivity is reduced immediately postoperatively but recovers with nerve regeneration. Our article provides comprehensive review on the use of IVCM imaging in keratoconus patients.
Highlights
Ophthalmology and Visual Sciences Academic Clinical Program, Duke-NUS Medical School, Abstract: Keratoconus is the most common primary corneal ectasia characterized by progressive focal thinning
As for genetic factors, alterations in Lysyl oxidase (LOX), Collagen Type V Alpha 1 Chain (COL5A1), and Forkhead box protein O1 (FOXO1) gene have been correlated to keratoconus pathogenesis [6,7,8]
With increasing recognition of the important role corneal nerves play in maintaining structure and function of the cornea, we aim to summarize the literature regarding the use of in vivo confocal microscopy in the keratoconic cornea before and after CXL in this review
Summary
Four international databases (Web of Science, PubMed, Scopus, and Google Scholar) were searched for relevant articles. All cross-sectional and longitudinal studies discussing keratoconus, cross linking and corneal sensitivity in the body, figures, or tables of the article were accepted without any restrictions
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