Age and increased incidence of "forward bowing" of the iris in normal eyes

Purpose and methods: The incidence of forward bowing of the iris, width of the iridocorneal angle, and distance between the apex of the angle and the scleral spur were studied using high-frequency (50 MHz) ultrasound B-scan i mages in 90 normal eyes from Japanese volunteers. Results: The incidence of forward bowing of the iris, defined as a 120-mu m anterior shifting of the posterior profile of the iris, increased from 0% in subjects under 31 years old to 50% in subjects 71 years of age and older . The: iridocorneal angle was significantly narrower and the distance betwe en the apex of the angle and the scleral spur was significantly less in eye s with forward bowing. Of the risk factors (age, axial length, sex, and cor neal curvature), age (p = 0.0005) was the most significant risk factor for forward bowing of the iris; Conclusion: Forward bowing of the iris is not uncommon in the elderly. Half of the Japanese subjects in this Study 71 years of age and older had this condition, even though they had no optic nerve atrophy or elevation in intr aocular pressure (IOP) at the time of examination.