I think that schools will appreciate the experience, but at a lot of my interviews I was often asked about my experiences in different scopes of optometry. So I’d say if you get the job as an ophthalmic tech I would still shadow Optometry practices, and get my letter of rec from an OD.
Agree with optometry97. You are wanting to go to Optometry school, not Ophthalmology school I assume. Schools would rather see you working in Optometry, if the ophthalmology office has optometrist working as well that's fine. But, try to focus your time on the optometry world.