Characterization of Iris and Lens in Subtypes of Congenital Glaucoma using Ultrasound Biomicroscopy: A Case-Control Study

Abstract

Purpose : Broad etiologic categories of congenital glaucoma include: 1) Primary, 2) Syndromic (Sturge-Weber syndrome, Oculo-Cerebral-Renal Lowe syndrome, Muscle-Eye-Brain disease, among others), and 3) Secondary (following congenital cataract or uveitis). Anatomic variants of the iris and lens have been described in association with each of these subtypes, but anatomic variants do not currently play a significant role in clinical glaucoma evaluation. We undertook a comparison of iris and lens parameters among diverse congenital glaucoma etiologies to describe the different structural patterns.

Methods : Subjects were aged 0.25-12.5 years. Cases were defined as diagnosis of glaucoma prior to age 24 months; controls were age-matched subjects with normal eye exam undergoing general surgical procedure. 16 subjects with glaucoma and 16 controls were enrolled. Ultrasound biomicroscopy (UBM) images (n=128) of the anterior segment were analyzed using ImageJ software by an observer masked to glaucoma status.

Results : Five lens and iris measurements (Fig. 1) were found to be significantly different between glaucoma and control eyes. Glaucomatous eyes had longer cross-sectional iris trajectory (P=0.04), more iris convexity (P=0.0002), lower iris thickness (P<0.0001) (Fig. 2), increased angle-opening-distance (AOD500, P<0.0001), and thinner lens (P=0.004). Overall, syndromic glaucoma demonstrated more extreme differences than primary or secondary glaucoma, relative to controls. Earlier age of disease onset and increased number of invasive glaucoma surgeries were also associated with more extreme anatomic variants.

Conclusions : Consideration of congenital glaucoma subtypes on a continuum of anomalous anatomy offers a better understanding of iris and lens changes associated with this family of diverse diseases. Iris and lens thickness may be markers for glaucoma severity. In the future, these associations with glaucoma subtype may improve diagnosis and lead to generalizable treatment heuristics in the context of diseases of variable severity, particularly in cases of unknown or multifactorial etiology.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.

 

Sample UBM images with relevant anatomic variants demonstrated 1A) iris trajectory (yellow), iris thickness (blue), AOD500 (green), lens thickness (red), and 1B) iris convexity (orange).

 

Mean maximal iris thickness among eyes with 6 glaucoma subtypes (blue), compared to age-matched controls (green).