Changes in Corneal Clouding Over Time in Patients With Mucopolysaccharidosis

Mucopolysaccharidoses (MPSs) are a rare group of lysosomal storage disorders characterized by the accumulation of incompletely degraded glycosaminoglycans (GAGs) in multiple organ systems, including the eye. Visual loss occurs in MPS predominantly due to corneal clouding. Despite the success of enzyme replacement therapy (ERT) and hematopoietic stem cell transplantation (HSCT) in improving many systemic manifestations of MPS, less is known about their effect on corneal clouding. This study prospectively analyses the effect of both ERT and HSCT on corneal clouding using objective measures over time.

This is a prospective longitudinal observational study. Corneal clouding was assessed in each participant using slitlamp, digital slit-lamp photographs, and an iris camera (Corneal Opacification Measure [COM] and the Pentacam system).

Data were collected for 65 participants: 39 MPS I (Hurler), 5 MPS II (Hunter), 12 MPS IV (Morquio), and 9 MPS VI (Maroteaux-Lamy). Follow-up data are available for 45 participants (29 MPS I, 3 MPS II, 6 MPS IV, and 7 MPS VI).

This study found corneal clouding to be stable in most participants with MPS I, II, IV, and VI over a follow-up period of 5 to 75 months (median of 30 months) when measured with clinical corneal grading systems, graded digital slit-lamp images, and iris camera COMs. For those with Pentacam densitometry measures, there was a progression of corneal clouding, on average, in those with MPS I and MPS VI. There was no apparent difference in progression of corneal clouding between patients who were on ERT, HSCT, or no treatment.