Iris segmental atrophy is the result of a certain state of high intraocular pressure that impairs blood supply to the iris artery, causing ischemic segmental or fan-shaped atrophy consistent with the shape of the distribution of the iris artery. Iris segmental atrophy is a clinical manifestation of acute congestive glaucoma in remission. What are the causes of acute congestive glaucoma? 1. The basic etiology is related to the anatomical structure of the anterior segment, especially the state of the atrial angle. In addition, emotional excitement, prolonged work in a dark environment and close reading, climate change, seasonal changes may lead to its acute onset. 2. Pathogenesis Under normal circumstances, there is a certain resistance to the flow of atrial water from the posterior chamber to the anterior chamber through the pupil. When the physiological pupil is dilated (e.g., at night) or the lens is moved forward (e.g., prone), the pupillary block rises, and it can, to some extent, change the refractive state of the eye to accommodate certain physiological needs. As we age, the lens gradually enlarges and moves closer to the iris, and the physiological pupillary resistance rises. If there are also risk factors such as congenital microphthalmia, microcornea, hyperopia or shallow anterior chamber, the gap between the iris and the lens becomes narrower. When the pupillary resistance is elevated enough to prevent atrial flow so that the posterior chamber pressure is higher than the anterior chamber, the peripheral iris bulges forward and attaches to the trabecular meshwork causing atrial angle obstruction, which is pathologic pupillary block. If atrial angle closure is complete, it triggers an acute attack of glaucoma. Pupillary block is a common phenomenon in people with shallow anterior chamber (including angle-closure glaucoma and normal shallow anterior chamber). The same anatomical features of the anterior segment cause the same amount of pupillary block force, but the same amount of pupillary block force does not necessarily cause the same effect in different individuals, i.e., it does not necessarily cause the atrial angle to close. Although physiological pupillary block is likely to turn into pathological pupillary block only in patients with narrow atrial angles, not all individuals with shallow anterior and narrow atrial angles will experience atrial angle closure. This suggests that there are other causative and unknown factors at play in the cause of atrial angle closure in addition to the known factors. Common factors affecting pupillary blocking power include: As age increases, the lens increases in size and the distance between it and the iris shortens. Some statistics show that the lens thickness increases by 0.75 to 1.1 mm after age 50, with a forward shift of 0.4 to 0.6 mm. ultrasound measurements of the lens in patients with primary angle-closure glaucoma show an average thickening of 0.6 mm compared with normal subjects. the ratio of lens thickness to eye axis increases with age, more markedly in patients with glaucoma. The enlarged lens also causes the peripheral iris to shift forward and the atrial angle to narrow. Both age and accommodation can increase the convexity of the anterior surface of the lens, widening the contact surface with the iris and increasing the pupillary blocking force. The atrial angle can be blocked (e.g., a high-folded iris) or the iris can move away from the trabecular meshwork during contraction, widening the atrial angle. Eyes with this structure can be seen with the lens protruding into or even beyond the pupillary margin when the pupil is dilated. This can be easily seen under a slit-lamp microscope as the iris abuts the lens. The contraction of the ciliary muscle caused by the pupillary constrictor relaxes the suspensory ligament and causes the anterior surface of the lens to move forward, protrude, and thicken, which also increases the pupillary blocking force. The position of the lens is usually relatively fixed. When the lens is dislocated and swollen, its anterior surface shifts forward and the anterior chamber becomes shallow. Pronation can cause the entire lens-iris septum to move anteriorly. Hemorrhage at the back of the eye, tumors, increased posterior contents of the eye, and a smaller relative volume within the eye after scleral laparotomy can push the lens-iris septum anteriorly, with a subsequent narrowing of the atrial angle. The average axis of primary closed-angle glaucoma is 1 mm shorter than normal, and the distance between the anterior surface of the lens and the corneal endothelium is reduced by 1 mm. primary acute closed-angle glaucoma commonly occurs in hyperopic eyes and small eyes.