Examination of short binary sequences for mfERG recording.

Area of Science:

• Ophthalmology
• Neuroscience
• Biomedical Engineering

Background:

• Multifocal electroretinography (mfERG) initially used long sequences with short inter-stimulus intervals.
• Slower mfERG sequences have been developed to analyze specific retinal components like Oscillatory Potentials (OPs) and Optic Nerve Head Components (ONHC).
• Reducing sequence length improves patient comfort and reduces recording time, but risks losing response orthogonality, especially with multiple stimulated areas.

Purpose of the Study:

• To verify if a short mfERG sequence, specifically the one used by the Roland Retiscan stimulating 19 hexagons, can maintain the separation of first and higher-order responses for each stimulated area.
• To provide mathematical validation for the use of short sequences in slow mfERG protocols.
• To describe an empirical testing method for validating these short sequences.

Main Methods:

• Utilized m-sequences of length n=9 to drive 19 hexagons in the Roland Retiscan system.
• Employed photodiodes connected to a Diagnosys Espion to record responses.
• Analyzed recorded data using Excel and MATLAB to determine sequence properties and correlation coefficients.

Main Results:

• Confirmed that the sequences used were m-sequences of length n=9.
• Found that the correlation coefficients between all sequences and between decoding sequences were -1/(2n-1).
• Demonstrated that the sequences driving each hexagon were shifted by 26 steps, ensuring response separation.

Conclusions:

• Short mfERG sequences are mathematically validated for slow mfERG protocols.
• The tested short sequence effectively maintains the separation of first and higher-order responses for each stimulated area.
• This validation supports the use of shorter sequences for improved patient comfort and diagnostic efficiency in mfERG testing.