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Flat iris: causes, symptoms, diagnosis, treatment
Medical expert of the article
Last reviewed: 08.07.2025
[ Pathophysiology of flat iris
In a flat configuration, the iris is displaced anteriorly in the root region due to pressure from large or abnormally positioned ciliary processes. If the dislocation is sufficiently pronounced, closure of the trabecular meshwork may occur. In older individuals, a component of relative pupillary block may also be present.
Flat iris syndrome is defined as occlusion of the trabecular meshwork with functioning laser peripheral iridotomy.
Symptoms of Flat Iris
Symptoms, as with secondary angle closure, with relative pupillary block depend on the rate of angle closure. If there is a relative pupillary block component, an acute increase in intraocular pressure develops; symptoms will be the same as with acute angle closure. In most cases, angle closure occurs slowly, with no symptoms until intraocular pressure increases significantly or severe visual field changes develop.
Diagnosis of flat iris
Usually the eye is calm, the anterior chamber is deep in the center. Compression gonioscopy reveals a protruding outer ridge of the iris, bulging anteriorly with ciliary processes. Occasionally, individual processes can be seen with compression. Changes in the optic nerve depend on the duration and severity of the rise in intraocular pressure.
Treatment of flat iris
In the absence of trabecular meshwork closure, no surgical intervention is required in the presence of a flat iris. In the presence of a relative pupillary block, laser peripheral iridotomy is indicated.
In case of flat iris syndrome, it is important to perform iridoplasty to "move" the iris away from the angle. The usual treatment consists of applying 16 laser coagulates with an argon green laser at the extreme periphery. The laser coagulate size is usually 500 µm, 0.5 sec, 200-400 mJ.
As a result, such patients are faced with the question of the need for filtering surgery.