Use of New Imaging Technology to Assess Effect of Enzyme Replacment Therapy on Eye Disease Progession in Mucopolysacchardiosis

The mucopolysaccharidoses (MPS) are a group of hereditary disorders which arise from defects in enzymes which break down glycosaminoglycans (GAGs) which occur in a wide variety of tissues, resulting in multiple systemic complications. Sight loss occurs in MPS due to corneal clouding, retinal degeneration, glaucoma and damage to the optic nerve. Corneal opacification occurs in infancy in several MPS subtypes and in the untreated disease the opacification is thought to be progressive, contributing to significant visual impairment in many patients. Improvements in quality of life and lifespan as a result of early treatment (with enzyme replacement therapy and haematopoetic stem cell transplantation) have meant that management of ocular complications and preservation of vision has increased importance.

A repeatable, reliable technique for quantification of corneal clouding will allow objective demonstration of the effect of treatments such as ERT in stabilisation or improvement of corneal clouding, and to establish the natural history of corneal opacification in MPS.

The investigators have previously developed the Iris camera (Irisguard Corp, McLean, VA 22102, USA) technology to give an objective measure of corneal clouding (Irisguard model IGAD100 ®) (Aslam et al 2009). The investigators demonstrated that use of the iris camera for corneal opacification assessment in MPS is feasibile, practical and has shown evidence for validity and reliability (Aslam et al 2012) (research funded in part by Biomarin Europe Ltd). The densitometry program for the Pentacam® Scheimpflug camera has also been shown to be able to provide measurements of corneal clouding in MPS .This research proposal will allow us to use to these techniques to quantify corneal clouding over time in MPS patients and to assess the effects of treatment with ERT and HSCT on corneal opacification.