Hypotony of the eye is also known as ocular hypotony. It defines the low intraocular pressure (IOP). It is also responsible for decreasing eye vision. Under normal conditions, IOP is generally between 10 and 20 mm Hg. mm Hg is a way to report pressure and refers to millimeters of mercury. When the IOP level drops below 10 mm Hg, an eye is considered to be hypotonous. However, it may not cause a obstacle unless the IOP drops below 5 mm Hg.
Causes Of Hypotony
There are many causes for hypotony. The most common causes are chronic inflammation within the eye, post surgical wound leak or detachment of the retina. It is also often held responsible for shallowing of the anterior chamber (front inner part of the eye) and detachment of the choroid (layer of the eye lying between the sclera and retina).
Filtering surgery is the most common surgical procedure associated with post-surgical hypotony. To treat glaucoma, the most common type of surgical procedure is trabeculectomy. It involves the removal of peripheral cornea (clear membrane in front of the eye) or part of the trabecular meshwork (eye’s drainage canals). This surgery is performed to increase the fluid flow from the eye. Post-surgical hypotony can lead to following conditions depending on its severity and duration:
- swollen optic discs
- engorged retinal vessels
- folds in the retina and choroid
Chronic hypotony occurs rarely today after a trabeculectomy because of modern technology.
Treatment Of Hypotony
Treatment of hypotony is crucial when it becomes a relevant cause for visual loss. Depending on the cause, hypotony can be treated with a variety of modern techniques. To repair post-surgical leaks, few methods are listed:
- placement of an oversized contact lens
- patching
- various suturing techniques
- injecting blood to promote scarring
- drainage of fluid external to the choroid
