Optical coherence tomography of the human crystalline lens and its application to the structural assessment of cataract in the Down syndrome eye.

Abstract

Down syndrome (DS) is the most common cause of intellectual disability in humans and is associated with intellectual and physical complications, including Alzheimer’s disease (AD). Ophthalmic problems are common in DS often resulting in mild-moderate visual impairment. Cataract (reported prevalence 4-72%) has also been reported, but morphology and type are not well understood. Recently, researchers have described ‘supranuclear’ cataract in the eyes of typically developed adults with AD and those with DS, linking this with beta-amyloid (Ab) peptide accumulation, pathognomonic of AD. However, this assertion seems precipitous, given the lack of characterisation of lens opacities in DS.

This study has established a method of objectively grading any morphology of cataract using Optical Coherence Tomography (OCT). In a cohort of 90 typically developed adults aged 50 years and older, this newly-developed method was validated by comparing its measures of lens opacity to the commonly used, slit-lamp based Lens Opacities Classification System III. OCT subsequently characterised the morphology of lens opacity in a group of individuals with DS aged 6-55 years. Lens opacities were common in DS (prevalence 77.8%). Their presence was unrelated to age or visual acuity. The most common presentation was dot-like opacities scattered throughout the crystalline lens cortex and, occasionally, nucleus. These opacities were not supranuclear and do not appear to be consistent with Ab accumulation. There was little evidence of early onset of agerelated nuclear, cortical and posterior-subcapsular cataract types. Retinal structure was examined using posterior-segment OCT in DS. Increased macular and nerve fibre layer thickness was found, in opposition to the neural thinning found in AD.

In summary, this work has developed and validated a novel technique of assessing crystalline lens structure, provided original, detailed quantitative data on typical DS cataract morphology, and shown that the DS eye does not exhibit the characteristic features reported in AD.

Date of Award	Jul 2018
Original language	English
Sponsors	Department for Employment and Learning (DEL)
Supervisor	Kathryn Saunders (Supervisor) & Julie-Anne Little (Supervisor)