I bought two angled second last one because it was really good deal used.
I can glass with these all day long without any eye strain. Believe it or not I had a Swarovski ST80 that gave me eye strain.
I also own a Nikon Fieldscope ED 82 25-75x Straight and Meopta S2 20-70x Angled and Kowa 554 and Vortex Razor HD G1 16-48x65 and Bushnell Elites both models. Optolyth 80 new old stock that I got scammed buying from previous Optolyth dealer that have rotted glass and all eyepieces also rotted glass due to age and outright refused to refund my money on.