What test provides definitive diagnosis of SARDS?

• A. Intraocular pressure measurement
• B. Electroretinogram (ERG)
• C. Visual field testing
• D. Fundus photography

Answer: (B)

Electroretinography directly tests retinal function, and that’s what makes it the deciding test for SARDS. In SARDS, the retina stops functioning abruptly, affecting both rods and cones. An ERG measures the electrical responses of these cells to light, and in SARDS you get severely reduced or completely non-recordable responses for both scotopic (rod-dominated) and photopic (cone-dominated) tests. This lack of retinal electrical activity confirms retinal dysfunction as the cause of sudden blindness, distinguishing it from issues that affect the optic nerve or structure of the eye. Other tests can show anatomy or general function—like intraocular pressure, fundus appearance, or visual fields—but they don’t demonstrate the retina’s functional status the way ERG does, so they cannot confirm SARDS on their own.