In cone-rod dystrophy, which photoreceptors are lost first, followed by which are affected next?

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Multiple Choice

In cone-rod dystrophy, which photoreceptors are lost first, followed by which are affected next?

Cone-rod dystrophy starts with loss of cones, the photoreceptors that mediate daylight, color vision, and fine central vision. When cones deteriorate first, people notice blurred central vision, trouble with colors, and reduced visual acuity early on. Objective tests often show a greater early reduction in cone-driven (photopic) responses compared to rod-driven (scotopic) responses. As the disease progresses, the rods are affected next, leading to night vision difficulties and gradual peripheral vision loss. That sequence—cones first, then rods—is what defines cone-rod dystrophy. The other patterns don’t fit the typical progression: rods-first describes rod-cone dystrophy; simultaneous loss or loss limited to cones would not align with the progression seen in cone-rod dystrophy.

Cone-rod dystrophy starts with loss of cones, the photoreceptors that mediate daylight, color vision, and fine central vision. When cones deteriorate first, people notice blurred central vision, trouble with colors, and reduced visual acuity early on. Objective tests often show a greater early reduction in cone-driven (photopic) responses compared to rod-driven (scotopic) responses. As the disease progresses, the rods are affected next, leading to night vision difficulties and gradual peripheral vision loss. That sequence—cones first, then rods—is what defines cone-rod dystrophy. The other patterns don’t fit the typical progression: rods-first describes rod-cone dystrophy; simultaneous loss or loss limited to cones would not align with the progression seen in cone-rod dystrophy.

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