The Lowdown of Hypotony
Dr. Visanee Tantisevi starts her dissertation explaining that there are mainly two cutoffs for defining hypotony: statistical hypotony, and clinically significant hypotony, if IOP is low enough to reduce vision.
As regards clinically significant hypotony, she emphasizes the importance to look for hypotony maculopathy first as visual loss from this condition may be permanent. She mentions other features of hypotony such as choroidal effusion, fast cataract progression and keratopathy.
Then she presents the causes of hypotony, such as postoperative, traumatic, bilateral hypotony and other causes and gives practical recommendations to deal with each one in a conservative way. She finalizes saying that these measures should be individualized in each patient in order to restore ocular structures and therefore visual acuity, and close monitoring for improvement is mandatory in order to intervene surgically if necessary.
Dr. Shlomo Melamed begins with the definition of Cyclodyalisis cleft, which is the separation of the ciliary body from the scleral spur creating a direct communication between the anterior chamber and the suprachoroidal space. He explains the mechanism leading to reduced IOP with its consequences on ocular structures and visual acuity.
He continues enumerating the most frequent causes: traumatic, idiopathic and therapeutic and explains briefly the epidemics of each one.
He mentions diagnostic tools such as gonioscopy, UBM and AS-OCT and finalizes his talk with very useful tips about treatment options to resolve the Cyclodyalisis cleft. These are: medical treatment, laser or surgical repair.
Dr. Shenton Chew tells us the challenges of trabeculectomy despite correct bleb morphology, such as patient discomfort, ocular surface disease and ocular hypotony. He emphasizes the importance of distinguishing numerical hypotony and clinically significant hypotony, which has specific signs and can lead to permanent visual impairment. Hypotony may trigger a vicious cycle of inflammation, ciliary body malfunction and more hypotony that should always be recognized early so it can be reverted.
He remarks the importance of preventing post-trab hypotony, recognizing risk factors for the condition, such as young myopic patients and ocular inflammation. Surgical technique is also crucial, especially the scleral flap creation and placing of the flap sutures. Dr Chew suggests some measures to perform during surgery to prevent hypotony.
Then he presents an algorithm to identify causes of early hypotony based on bleb height and possible treatments in each situation: wound leak, ciliary body shut-down, cyclodialysis cleft or over-filtration.
He also shows an algorithm for late hypotony focused on bleb morphology, and how to approach each cause.
In this presentation, Dr. Sonya Bennet emphasizes the importance of preventing rather than treating post-tube hypotony by planning the surgery. This includes identifying risk factors and having some intraoperative considerations, especially with non-valved tubes.
Then she presents treatment options for early management of hypotony, which depending on the eye´s response and severity of the clinical picture may be medically or surgically resolved. She explains that IOP usually rises during the first 4-6 weeks as the plate encapsulates.
In the case that hypotony persists more than 6 to 8 weeks, i.e. late hypotony, treatment should be considered if visual acuity is reduced. In this case, several surgical options are available to reduce aqueous flow. Another scenario is the occurrence of hypotony after removal of intraluminal sutures, in which replacement of sutures must be considered, either ab-interno or ab-externo.