What's the "opposite" of glaucoma? (Eye pressure too LOW)?

I thought I remembered hearing about an eye disorder in which the pressure in the eye is too low, which basically would be the opposite of glaucoma.

Is there a term for this medical condition? I tried Googling it but all I found were references to glaucoma. I'm particularly curious what would happen to the eyeball, and to a person's vision, if the eyeball were allowed to become "under-inflated" (for lack of a better word).

Or is this simply not possible?

If the pressure is low (hypotensive), there is a greater risk of retinal detachment as there is insufficient pressure to stop the retina collapsing in.

Low tension glaucoma is simply glaucoma that has occurred at what we consider to be a normal pressure. Usually glaucoma occurs when the pressure exceeds 21mmHg. Low pressure glaucoma occurs at lower pressures than this.

Is they're an opposite?

This can only happen if there is a puncture in the eye ball. Otherwise the eye ball is a closed system that continually produces a fluid and drains it keeping a constant pressure in the eye. If the pressure is really low like 4mm Hg or lower this is called hypotony.

It is termed 'HOPOTONY'
A normal tension in the eyes is 10 - 20 mm of hg which is essential for the normal contour and functioning of the eye.

Low tension glaucoma is what I believe you are looking for, yes it is totally possible I hope the following info helps.

In this type of glaucoma it is believed not enough blood reaches the tiny arteries in the optic nerve blood from the heart flows towards the head, and then to the eye.
Behind the eye the blood flows in a small artery, and just behind the eye the small blood artery enters the optic nerve itself.
Inside the nerve this small artery provides even smaller tiny branches that reach the tissues of the nerve.
Without its blood supply, the nerve becomes damaged, and the sight will be reduced. In low tension glaucoma it is thought the primary problem is too low a pressure in the blood supply to the nerve. This is rather like having a low water pressure in a house... not enough water comes out of the tap.
We do no know why this is, but only rarely does the nerve become badly damaged.
Treatment is drops in most patients. The drops lower the pressure in the eye so more blood can flow in.
Occasionally an operation is needed to lower the pressure in the eye. This similarly allows more blood to flow in and reach the tiny vessels in the optic nerve.
Normally, fluid (a little like water, called 鈥榓queous humour鈥? is made in the middle chamber of the eye. It then flows through the pupil to the front chamber, and then out of the eye through small drainage channels. These channels are like a 'sieve' in the kitchen used to drain rice.
As mentioned, treatment is aimed at lowering the pressure in your eye, so more blood can flow into the optic nerve.
Occasionally an operation may be necessary. As part of the operation a small hole is made to let more fluid out of the eye. Your ophthalmic surgeon will discuss the pros and cons of the operation if it is necessary.