Also, if you are concerned about the eyesight aspects of the Class One, the CAA at Gatwick are quite happy to assess that first, and if unsatisfactory will only charge you for that portion of the medical - not the full £400.
Phone them up and ask - they are in fact extremely helpful and pragmatic, in my experience.
Certainly speak to your optician first for his opinion on you c.f. the guidance from the CAA's website.