The First (89/48/EEC) and Second (92/51/EEC) European General Directives on the Mutual Recognition of Professional and Vocational Qualifications allow:
nationals of an European Union (EU) or European Economic Area (EEA) country (e.g., Spain);
who hold professional qualifications granted in their own country; to apply to another EU/EEA Member State (e.g., UK) to have their qualifications recognised for practice in that Member State. The applicant's post qualification practical experience must also be taken into account.
Under the Directives, the GOC is what is termed the UK "designated authority" for optics. The role of a designated authority is to consider applications under the Directives. The Council must decide whether there are any significant differences between the applicant's training and education in optics and that which is required of a UK qualified optician (either a dispensing optician or optometrist).
Once eligibility for registration as a dispensing optician or optometrist is achieved via this route, you may practise, but only when you have registered with the GOC. Once on the register you must renew your registration annually in order to maintain your license to practise.