How to adress all the subject you are applying to in your personal statement

how do you address all the subject you want to apply for in your personal statement without focusing on mainly one .p.s want to apply for optometry and biomedical science

Ideally you do this by
applying for a single subject or
applying for subjects that are very closely related (ie a selection of modern languages/biological science courses) or
applying for universities/courses that state outright they place little to no weighting on the PS.

Optometry is very competitive like most vocational health courses. Biomed can be the same if you're applying for a health professional accredited course (the academic versions of biomed are often used as back up choices for medicine applicants and so are generally accepting of a PS devoted to another subject).

The deadline for applying is over 6 months away - you have plenty of time to decide which subject to focus on (or do the research to ask universities directly if they'll be likely to reject you if you apply with a PS focused on something else). I'd advise you to use it to the full.

One technique that's often very helpful is to write 2 separate PSs, one for each subject. Quite often it will be obvious when writing which you would prefer and therefore which you should be applying to.