At least in the US, use or non-use of the slit lamp has little to do with the diagnosis, and everything to do with the practitioner.
It's years since I saw an MD ophthalmologist here without having a slit-lamp exam. It's just the way they do a complete exam, since you are sitting in their chair and they have it hanging in front of them.
Less so for optometrists.
The desert here in Arizona this last few weeks has been very pleasant indeed!