What is Hypotony?
Hypotony is low pressure inside the eye that can lead to vision loss.¹ Most commonly, hypotony results from eye surgery such as glaucoma surgery.² Trauma, like a blunt force to the eyeball socket with penetration of the eye, can also lead to hypotony.¹
Common symptoms of hypotony include pain, vision loss and visual disturbance, but some people experience no symptoms at all. ³ Hypotony requires treatment, including medication and possibly surgery, to prevent further damage and vision loss.¹
Hypotony can last for weeks or longer (chronic hypotony) and if left untreated, can result in permanent structural damage to the eye with vision loss.³
- Hypotony is a serious eye condition resulting from eye surgery or trauma.
- Some people experience vision changes and pain, while others experience no symptoms at all.
- Early detection of hypotony is critical and patients should seek treatment immediately.
Someone with hypotony has intraocular pressure (IOP) less than 6.5 mm Hg (millimeters of mercury).¹ Patients with IOP below 5 mm Hg often experience vision loss.¹ Normal IOP is between 12-21 mm Hg.¹ In hypotony maculopathy, the low IOP causes changes to the back of the eye, including choroidal folds in the retina and optic nerve edema, leading to vision changes.¹
Causes of Hypotony
Most cases of hypotony occur after eye surgery. An eye doctor will monitor pressure to ensure IOP starts to normalize. If pressure is still low after three months, it is considered chronic hypotony.⁵
Glaucoma filtering surgery is a common cause of hypotony.¹ In trabeculectomy, the eye surgeon creates an incision in the scleral flap called a filtering “bleb” to increase fluid (aqueous humor) flow from the eye.¹ In some cases, the filtering bleb causes too much fluid to leave the eye.² In addition to an over-filtering bleb, trauma and eye infections or inflammation can lead to a bleb leak.² This increased outflow reduces the pressure in the eye, leading to hypotony.²
In some cases, the ciliary body (space in the eye that produces fluid) doesn’t produce enough aqueous humor and the decreased aqueous humor leads to hypotony.³ This can happen after eye trauma, retinal detachment, eye inflammation or eye surgery, though it is rare.⁵
An eye surgeon (ophthalmologist) should treat hypotony immediately to prevent further damage and the onset of hypotony maculopathy. Treatment will depend on the cause of hypotony.
- Non-surgical treatments include topical antibiotics and aqueous suppressants (to reduce aqueous outflow). For a bleb leak, a bandage contact lens may be used as a seal until natural healing and closure happens. ¹
- Some cases will require autologous blood injections to promote scarring, surgical glue to seal the leak, or compression sutures to stop the fluid outflow.¹
- Surgical bleb revision is warranted if the above conservative measures fail.
- If the hypotony is from penetrating eye trauma, scleral rupture, or retinal detachment, surgery is also warranted.
- If a patient develops chronic hypotony maculopathy, retina surgery may be required.
If hypotony is not diagnosed early and treated promptly, permanent damage and vision loss may occur from damage to the retina and optic nerve.