In my opinion, the concept of subspecialty in optometery is a bit vague. Even if you are qualified by a residency, this might not qualify you as being a "subspecialist" per se in the eyes of the licensing authorities of any state.
With that limitation in mind, there are recognized residencies or fellowships which many employers recognize and want in their applicants.
1. In my opinion, the greates opportunity for a career in industry outside of private practice or education is with contact lens or ophthalmic lens companies. The former more than the latter. Many companies want clincal research optometerists to both design as well as collect the clinical data which can best be done by examination of the patient at a company-sponsored contact lens clincial facility.
2. Low vision is also something that will get much traction in the future. There are already well over several thousand US Army veterans who have suffered some degree of service - connected eye or brain injury. Low vision optometrists who are also schooled in TBI(trauamatic brain injury) will be in demand at the Veterans Administration. There is also a need for post stroke rehabilitation.
3. Geriatrics isn't really a recognized subspeciality by itself but there are many who will need to complement a geriatric medical practice. I am a consultant to a geriatric clinic and am aware of these issues.
HTH
