​Dr Zainah graduated from the Faculty of Medicine, National University of Singapore in 1992. She completed her ophthalmology residency training in Singapore and obtained her post-graduate Ophthalmology qualifications in 1997. She subsequently underwent 3 years of advance surgical training and attained her specialist accreditation in 2001.

She was involved in the organisation and running of microsurgical and cataract surgery courses locally and internationally as well as training of registrars and overseas fellows in cataract surgery. She spent three months observing at the practice of renowned cataract surgeons Dr Howard Fine in Oregon and one week with Dr Akahoshi Takayuki in Tokyo.

Dr Zainah was Examiner for Master of Medicine (Ophthalmology) in 2006 and Examiner for Fellow of Academy of Medicine in 2008. She also contributed to parts of the Cataract & IOL chapter for the book titled Asian Perspective in Ophthalmology. She was accorded the Excellence in Teaching Award from Dean of Medical Faculty, National University of Singapore in 2008.

Dr Zainah served as the Deputy Head for both the Cataract & Comprehensive Ophthalmology Department and Training & Education Department in 2007. She was offered Headship role for both departments but had to shorten/decline the positions as she moved to Christchurch, New Zealand in 2008 for family reasons.

Dr Zainah worked as a Consultant in the Christchurch Hospital when she was in New Zealand where she was also involved in training of registrars in cataract surgery as well as planning cataract surgery pathways. She also did locum work in private practice as well as in ophthalmology clinics in other New Zealand cities of Invercargill/ Nelson/Whangarei/Manukau/Blenheim. She occasionally returned to SNEC as a Visiting Consultant during this period.