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Achromatopsia
Main Features
- Reduced vision due to lack of functioning cones
- Vision usually 20/200 with complete color blindness in complete forms
- Incomplete forms may have better vision and some color vision
- Nystagmus that may improve with age
- Central relative scotoma with normal peripheral visual fields
- Complete and Incomplete forms
- Usually stable but some see slow worsening of visual acuity and macular atrophy
Distinguishing Features
- Photophobia at birth or early infancy
- Better vision in dim illumination
- Sluggish pupil responses with paradoxical constriction in the dark
- Usually normal fundus appearance
- OCT may show ellipsoid zone disruption or absence, outer retinal atrophy and RPE loss
- ERG
- lack of cone function- 30 Hz flicker and single flash photoptic waveform is small and delayed
- normal ROD function- normal dark adapted dim and bright flash waveforms
Differential Dx
- Idiopathic Nystagmus Syndrome