I'm currently trying to conduct a simple study to compare

- the conventional way of measuring proptosis on CT using the interzygomatic line

- a new method using a new landmark

Obviously the measurements would be different. My study seeks to the assess if the new method will correlate with the old method.

I've been in discussion with a statistician who suggested a a multilevel model because my study involves paired eyes from each patient.

However, after scouring the website, I see papers using linear regression models for similar studies.

From my understanding, multilevel models assesses how clustered data affects the outcome.

Is this actually necessary if I'm only needing to assess the correlation between two sets of measurement - despite it being paired eyes?