Abstract
Purpose :
To determine the development of iris structure from birth to adulthood using handheld anterior segment optical coherence tomography (HHAS-OCT) and to investigate the effect of iris pigmentation
Methods :
In this cross-sectional study design, HHAS-OCT images were acquired (18x6mm scan sequence) from 123 participants under 18 and 83 participants from 18-40 years capturing the pupil centre, nasal and temporal anterior chamber angles, full irides and corneal reflection. Eyes were classified as lightly (blue and green eyes) and heavily (all brown eyes) pigmented. The following nasal and temporal surfaces/borders were segmented using ImageJ: (i) anterior surface of the iris, (ii) anterior surface of the posterior epithelial layer (PEL) (iii) posterior surface of the iris, and (iv) corneal posterior surface. The stromal anterior border layer (SAB), PEL and total thickness (TT) of the iris were calculated. Linear mixed models were generated for statistical analysis using a logarithmic transformation of age including fixed factors of: side (nasal or temporal), sex (male or female), eye (left or right) and iris pigmentation (heavy or light)
Results :
Total iris thickness develops from 237µm (95% C.I. 208, 268 µm) at birth with a logarithmic relationship to a mean of 385µm (95% C.I. 293, 477 µm) in 18-40 year olds (y = 31.7 ln(x) + 307) with the data plateauing at around 10 years. These changes were a result of the direct changes in the SAB layer with age whereas the PEL remained relatively unchanged at a mean of 52.4µm (S.D. 10.2µm). SAB layer thickness was significantly thicker (P=0.005), the PEL thinner (P=0.020) and the TT thicker (P=0.043) in more heavily compared to more lightly pigmented eyes. This effect is seen in nasal and temporal irides
Conclusions :
The iris thickness increases rapidly in the first few years of life plateauing at around 10 years and above. The change in iris thickness with age is mainly due to the changes in SAB layer rather than the changes in the PEL. The data also provides comparative age-adjusted values for anterior eye diseases
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.