Ultrasonic evaluation of the lens thickness to axial length factor in primary closure angle glaucoma.

Ultrasonic biometry was done in 232 normal eyes and 138 eyes with primary angle closure glaucoma (ACG), using Ultrascan Digital B System IV (10 MHz). The ratio between the lens thickness and the axial length (lens thickness to axial length factor, LAF) was evaluated as a biometric index for assessing the eye with primary ACG in Chinese. LAF of 2.00 was found to be ideal point of demarcation between ACG and normal eyes (i.e., lens thickness equals to 1/5 of axial length). It appears that LAF is helpful in screening primary ACG eyes from eyes of the general population. This is similar to the anterior chamber depth of 2.5 mm which is recognized as a threshold for the occurrence of primary angle closure glaucoma.