Abstract
Purpose :
Shallow anterior chamber is a risk factor for primary angle-closure glaucoma (PACG), and it was etiologically attributed to a genetically determined forward position of lens and an increased lens thickness (Lowe, 1970), while lens growth was not believed to be a contributing factor. The purpose of this study was to model the effect of lens growth on the anterior segment and refraction of the PACG eye.
Methods :
A PACG model eye is constructed by moving the lens position forward and increasing the lens thickness (LT) from a normal emmetropic model eye (Atchison, 2009). The lens position and LT were varied in the model to determine the changes in the anterior chamber depth (ACD), lens power and refraction of the PACG model eye. The distance from the lens equator to the sclera on the lens equatorial plane was considered as an influential factor in this model, and its effect on ACD and LT was analog to the ciliary muscle contraction in accommodation. Lens growth was also modeled to determine the age-related changes in ACD and lens parameters in the PACG model eye.
Results :
With a 0.65mm of lens forward movement and a 0.35mm of LT increase, as suggested by Lowe (1970), the PCAG model eye was found to be myopia of about -7.29D at 20 year old, and the myopic refraction remained (-4.50D) even the axial length of the eye was shorten about 1.00mm. In order to make the PCAG model eye to be close to emmetropic or hyperopic in refraction, the lens forward positioning and LT increases need to be less than 0.30mm and 0.15mm respectively. As the lens grows, a fast lens forward moving and related LT increasing in the PCAG model eye than the normal eye was found, and it made the ACD shorten about 0.35mm more in the PCAG eye than in the normal eye at about 50 to 60 year old. An additional factor could cause the ACD shorten about 0.20mm in the PCAG model eye.
Conclusions :
Multi-factorial contributors are involved in the process of shallowing of the anterior chamber in the PACG eye. While an inherent forward positioning of the lens, and related increase in lens thickness, still plays important role in the process, age-related lens growth makes comparable contribution to teh process also. Monitoring the lens growth related changes in ACD could be interesting in glaucoma diagnosis and treatment.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.