The passage "V 0.3/0.5 aiemalla lasikorjauksella" is to be interpreted as "Visus-value left eye / right eye (or vice versa, I am not sure) 0.3/0.5 when corrected with previous eyeglasses"

V 0.3/0.5 with earlier corrective lens

esim. Näöntarkkuuden asteittainen huononeminen, joka ei parane lasikorjauksella.

This is a highly contextual translation -- I am assuming that this is something like a report written after an eye exam and that this sentence is referring to the previous measurement. At least in the US, we refer to having an "eye examination" and then being "fitted" for glasses or contact lenses.

If this is not the right context, then this gloss is not correct. Marju's gloss seems appropriate to me if the sentence means that the reported VA measurement is what was achieved by the previous set of glasses.