This site is in the middle of a major expansion. It was originally designed as a resource for vision professionals who wanted to better understand how to care for patients with vision impairments. I'm now reworking the site with content for the general public — people with low vision and people who want to know more about low vision. Once that section is complete, I'll rework the section for vision professionals to better integrate with the general public section. Keep checking back to see how it's going, and if you find the content helpful please consider contributing to support the effort.


With achromatopsia, we’re dealing with the rod response only. We’re used to thinking of the rods as only being relevant in scotopic and mesopic conditions, but they’re contributing in the lower photopic light levels as well — it’s just that their contribution is dwarfed by the cone response.

Remember that throughout these discussions I’ve only been considering the VV for mesopic levels and upwards. To really consider the full VV for rods we’d need to extend the chart quite a bit into the lower illumination levels.

Without any cones, we’d expect to see a substantial loss of the high spatial frequencies, but less impairment in mesopic conditions, and no impairment in scotopic conditions.


Visual Volume: Achromatopsia

What this makes clear is how critically-important filters are going to be, to shift normal illumination levels down into the visual volume.

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