Electroretinograms in patients with achromatopsia.

Area of Science:

• Ophthalmology
• Genetics
• Electrodiagnostics

Background:

• Achromatopsia is a rare inherited retinal disorder characterized by reduced visual acuity, photophobia, and color vision deficits.
• X-linked achromatopsia (XLCA) and autosomal recessive achromatopsia (arCA) are the primary forms, caused by mutations in specific genes.
• Standard electroretinography (ERG) often shows normal rod function but undetectable cone responses in achromatopsia.

Purpose of the Study:

• To investigate residual cone function in patients with achromatopsia using advanced full-field electroretinogram (ffERG) techniques.
• To differentiate between X-linked and autosomal recessive forms of achromatopsia based on ERG findings.
• To explore the diagnostic and prognostic value of residual cone b-wave measurements.

Main Methods:

• Full-field electroretinograms (ffERGs) were performed on 20 patients (11 with XLCA, 9 with arCA).
• Computer averaging and narrow bandpass filtering were employed to detect sub-threshold cone b-wave responses.
• Cone response amplitudes to flickering orange and blue-green light were analyzed.

Main Results:

• Normal rod responses were recorded, but standard cone b-waves were undetectable.
• Residual cone b-wave responses were detected in 10 out of 20 patients using advanced ffERG analysis.
• Markedly different residual cone b-wave amplitudes were observed among XLCA families, suggesting at least two forms of XLCA.
• Autosomal recessive achromatopsia patients exhibited both protanope and deutanope type defects, while XLCA patients showed protanope type defects.

Conclusions:

• Advanced ffERG techniques can reveal residual cone function in achromatopsia patients.
• Residual cone b-wave amplitude measurements are valuable for diagnosing achromatopsia and potentially predicting outcomes.
• Distinct clinical and electrophysiological phenotypes suggest heterogeneity within X-linked achromatopsia.