As far as I know there is no standard import function in WL. I suggest to take one of the txt files, because these are ASCII files while all others are binary files. The differences between the ASCII files are small. Each optic simulation software supplier has a few features embedded in the belonging files.
I propose to use the Opticad_txt file, because this is almost the original ProSource ASCII format.
As the final step, you can read the file content with a Code similar to https://reference.wolfram.com/applications/eda/ImportingAndExportingData.html
To test your code I suggest to take a file with less rays.