What does loss of PLR suggest in a cataract patient?

What does loss of PLR suggest in a cataract patient?

• A. Normal aging of the eye
• B. Optic nerve disease only
• C. Concurrent retinal disease
• D. Intraocular infection

Answer: (C)

Pupillary light reflex relies on the retina detecting light and sending a signal through the optic nerve to the brain, which then triggers constriction of the pupil via the parasympathetic pathway. A cataract can dim light but does not usually abolish the reflex because some light still reaches the retina to trigger constriction if the cataract isn’t utterly dense. When the reflex is lost in a patient with a cataract, it suggests another problem along the reflex arc—most likely retinal disease that impairs the retina’s ability to sense light or transmit the signal. Intraocular infection can affect the eye but doesn’t typically cause a complete PLR loss in this context, and optic nerve disease could also cause PLR loss, but in the setting described, concurrent retinal disease is the most plausible explanation.

Pupillary light reflex relies on the retina detecting light and sending a signal through the optic nerve to the brain, which then triggers constriction of the pupil via the parasympathetic pathway. A cataract can dim light but does not usually abolish the reflex because some light still reaches the retina to trigger constriction if the cataract isn’t utterly dense. When the reflex is lost in a patient with a cataract, it suggests another problem along the reflex arc—most likely retinal disease that impairs the retina’s ability to sense light or transmit the signal. Intraocular infection can affect the eye but doesn’t typically cause a complete PLR loss in this context, and optic nerve disease could also cause PLR loss, but in the setting described, concurrent retinal disease is the most plausible explanation.