Limitations
Micro-aberrations scatter light and blur the spots.
Blurry spots contain useful information about optical scatter.
Notes:
The second limitation concerns aberrations which are not necessarily large in magnitude, but are on a very fine spatial scale. These “micro-aberratons”, or “higher-order” aberrations, scatter light and blur the spots formed by the optometer.
Although these blurry spots are problematic, they nevertheless contain useful information about the degree and location of scattering sources inside the eye.