Poor Mitsy...she must be so confused with loss of her vision. As Bron said detached retinas can occur from high blood pressure. Also depending on the size and position of the pituitary tumour, this can affect the optics and cause a build up of fluids under the retina.
From a human Cushing's site
"
Cushing's and the Eyes. ... Answer: Patients with
Cushing's syndrome may rarely develop an
eye condition called central serous chorioretinopathy. This condition represents the accumulation of fluid behind the
retina of the
eye and may cause
detachment of the
retina resulting in impaired vision."
From a few articles I read (human cases) sometimes this can clear on its own...in other cases laser surgery is used.
https://www.medicalnewstoday.com/articles/320606.php
I really don't know what the options are for kitties. It would depend on whether the retina is totally detached in both eyes or partially detached. You may want to see if there is a veterinary ophthalmologist you can be referred to.
In the meantime Mitsy will be disoriented and confused. A friend on mine had detached retinas...both eyes at separate time and he said his vision was wavy, blurred, colour flashes and doubled. Mitsy may quite possibly still have some vision, depending on the extent of the detachment, but it will not be 'normal'. Trying to keep the usual items...food, water, litter box etc all within a close proximity and showing her where everything is may help her feel more comfortable.
Sending prayer for you and Mitsy
