Introduction
It is estimated to affect 1 in 30,000 individuals
- Usually sporadic, but can be genetically inherited via AD, AR, X-linked
- It is a heterogenous group of conditions, with at least 30 genes implicated
- It is divided into 2 groups, being stationary and progressive
Progressive Pathophysiology:
- Genetically heterogenous, with over 30 genes reported to cause.
- These proteins are involved in PR function, such as phototransduction, OS morphogenesis, neurotransmitter release
- Affects 3 important genes:
- ABCA4 gene (62% of AR)
- GUCY2D gene (34.6% of AD)
- RPGR gene (73% of X-linked)
Dead Giveaways
Stationary Cone Dystrophy
Is known as cone dysfunction syndrome since it does not progress
Most common is Complete Achromatopsia (rod monochromatism)
It is of AR inheritance with preserved rod function
This makes the biggest giveaway normal rod ERG's but absent cone ERG's
VA and colour vision also affected
Blue Cone Monochromatism also occurs
X-linked recessive, and the long and medium wavelengths are not present
Vision is not greatly affected, but there is usually only tritan colour vision
ERG displays reduced cone response
Progressive Cone-Rod Dystrophy
Presents in early childhood or adolescence, and usually only begins with cone involvement, before involving rods
OCT Findings are very variable
Absent interdigitation zone, ONL atrophy occurs, reduced EZ and loss of EZ. RPE atrophy also seen. Outer retinal loss mos prominent in the perifovea Depends on different grades
Grade 0: Normal eye has 4 distinct hyper-reflective bands
Grade 1: Irregular loss of EZ and obscurity of border between EZ and ELM
Grade 2: Central thinning and segmental foveal loss of EZ
Grade 3: Foveal thickening and perifoveal disurption of EZ
FAF Findings:
Can have mottling patterns, and different apperances, but usually Bull's eye pattern
Discrete hypo-FAF can be seen in regions of RPE atrophy, correlating to VF scotomas
The areas of hypo-AF mark the RPE atrophy, and all of these are variants of ABCA4 deficit. Pigment mottling will also appear hypo-AF 
Bull's eye maculopathy
diagnostic features
Stationary Cone Dystrophy
Reduced central vision, nystagmus, photophobia, colour vision abnormality
Scotopic ERG will be normal
Photopic white ERG will be absent
Progressive Fundus Findings (poor vision)
Fundus findings are variable
Minimal fundus changes
Blunted foveal reflex
Pigmentary mottling
Bull's eye maculopathy
Well-demarcated macular
Scotopic ERG will be slightly reduced
Photopic white ERG will be absent
Mild Condition:
Mild pigment mottling
Mottled hypo-AF
Perifoveal attenuation of EZ
Advanced Condition:
Macular atrophy
Macular hypo-FAF and hyper-FAF ring can occur due to thickening RP cells
Loss of EZ and RPE