From other thread:
The thing is that most subspecialty trained docs want to practice their subspecialty and have no interest in doing tons of cataract Sx... the glaucoma doc wants to do glaucoma Sx, the retina doc wants to do retina Sx, and the corneal doc wants to do corneal Sx... it isn't always about the money. Some of the subspecialists at my centre does not even accept referrals for straight cataracts. There is simply not enough TIME in their clinic and OR to fit in a bunch of cataracts. At the same time there is a huge need for cataract Sx, especially in the upcoming years (every single person on earth eventually gets them), and this has mainly fallen into the realm of comprehensives docs. And like any surgery, the most cataracts you do, the more slick you get at it. If you're only doing 5 phacos a week, you're just not going to be as slick or safe as the person doing 30 a week. Not to mention nowadays there are plenty of advances in IOLs... you got your torics, multifocal, multifocal toric, etc. that you would need to keep up with the changing nuances of such advances on top of your own subspecialty interest.
Comp docs, at least where I am, also perform the most anterior segment lasers such as YAG PCO (as they perform the most cataract Sx) and SLT (as most mild-moderate glaucoma is managed by comps).
Comprehensive docs also receive lots of referrals for undifferentiated patients from GPs and optoms, and depending on the pathology they can generate lots of referrals for the subspecialists in the practice. In fact around where I am (academic centre in medium sized city with large catchment) the subspecialty clinics (outside of peds) rely almost exclusively on referrals from comprehensive ophthalmologists.
Lastly, there are a lot of patients with multiple ocular pathologies that simply does not require subspecialist care. Does it really make sense for a patient to see a glaucoma specialist Monday for their moderate stable glaucoma, then a retina specialist Wednesday to monitor for plaquinil maculopathy, then a cornea specialist Friday to follow up for their cataract, all the while waiting to have a biopsy of a minor lid lesion with an oculoplastic surgeon, when all they need is one visit with a comprehensive doc? This is the case more often than not.
Such is the case in Canada, not sure about the USA.