What typically causes "painless" acute persistent loss of vision?

The primary cause of a "painless" acute persistent loss of vision is central retinal vein occlusion (CRVO). This condition occurs when one of the main veins draining blood from the retina becomes blocked, leading to increased retinal vascular permeability, edema, and potential retinal ischemia. Patients often present with sudden vision loss, but it typically occurs without pain.

Understanding the characteristics of CRVO is important for distinguishing it from other eye conditions. For example, acute glaucoma usually presents with severe pain, redness, and associated symptoms such as nausea and vomiting, along with vision changes. Uveitis may cause vision loss as well, but it often comes with discomfort, redness, and potentially photophobia. Retrobulbar neuritis can lead to vision loss and may indeed be painless, but it typically involves ocular pain, especially with eye movements.

In summary, CRVO is recognized for causing a very distinct profile of vision loss that is painless and acute, making it the appropriate answer for this question.