New clinical pathways for keratoconus

Abstract

Pre-2000, the clinical management of keratoconus centred on rigid contact lens fitting when spectacle corrected acuity was no longer adequate, and transplantation where contact lens wear failed. Over the last decade, outcome data have accumulated for new interventions including corneal collagen crosslinking, intracorneal ring implantation, topographic phototherapeutic keratectomy, and phakic intraocular lens implantation. We review the current evidence base for these interventions and their place in new management pathways for keratoconus under two key headings: corneal shape stabilisation and visual rehabilitation.

Figure 1

Forest plot of meta-analysis of 12 month results from placebo-controlled randomised trials showing (a) disease progression (defined in these trials by an increase in maximum keratometry (Kmax) ≥1D) is significantly less likely after collagen CXL; and (b) disease regression (reduction of Kmax ≥1D) is significantly more likely after CXL.

Figure 2

A decision tree for intervention at presentation in keratoconus. We are currently exploring the role for transepithelial collagen CXL at presentation for younger patients with keratometric stage II disease; and ICRS in combination with transepithelial CXL to provide a gross shape correction in patients with reduced spectacle CDVA at presentation and higher levels of coma or keratometric stage III disease.

Figure 3

A pathway for shape stabilisation after initial intervention in keratoconus. Emerging transepithelial corneal CXL protocols avoid most of the complications associated with epithelium-off CXL but may be less effective.^, CXL can be repeated if there is continued disease progression.

Figure 4

A pathway for visual rehabilitation in stage II and III keratoconus. Initial intervention in keratoconus (Figure 2) may include collagen CXL±intracorneal ring segment implantation (ICRS). Neither intervention provides a predictable shape change. After a 2-year period to allow shape stabilisation post-CXL,^, further fine shape correction with topographic PRK^{, ,} may therefore be required to achieve good spectacle CDVA. If CDVA is good but uncorrected distance vision remains poor (UDVA) remains poor, then patients may opt for pIOL implantation^{, , , , ,} to complete visual rehabilitation.