That is tough because it's dependent on the age/health of the population too. The south for instance needs more retina because there's more diabetes.
The only specialty I have a definitive number for is oculoplastics. ASOPRS says you need about 250,000 people to support 1 ASOPRS surgeon. Here are best guesses for the others and I'm hopeful I'll get some corrections here for my own notes. All are population per 1 type of ophthalmologist:
Comprehensive: 20-25,000
Cornea: 25-100,000 (depends on how much comp vs actual cornea work is done)
Glaucoma: 100,000 (maybe less depending on how much comprehensive)
Retina: 100,000 (
How to Bring on a Retinal Specialist. this 2014 article says 20 comp docs to support 1 retina doc but not sure that translates into population well)
Pediatric: 200-250,000
Neuro: not even a guess, anyone else?
I will edit this if there is suggested updates either through consensus or links to data so there is not bad info left on the forum.