Trabeculectomy is the standard surgery for treating glaucoma, indicated in cases where patients have already undergone full treatment with medications and laser but still cannot control intraocular pressure to the desired level or cannot slow the progression of the disease. The main purpose of trabeculectomy is to create a drainage pathway for aqueous humor from inside the anterior chamber of the eye to the outside through a newly created opening at the junction of the cornea and sclera. A scleral tissue flap covers the outlet like a door before the aqueous humor drains into the subconjunctival space, appearing as a fluid-filled bleb (filtering bleb, Figure 1) on the surface of the eye. Some of the fluid in the bleb seeps through the conjunctiva to the outside, mixing with tears and is absorbed along with blood vessels, conjunctival tissues around the vessels, and lymphatic channels eventually.
Although trabeculectomy helps reduce intraocular pressure by draining a large amount of fluid at once, having a connection between the inside and outside of the eye can lead to various complications during and after surgery. Examples include hyphema (bleeding in the anterior chamber), low intraocular pressure, shallow or flat anterior chamber, choroidal detachment inside the eye, fluid or blood accumulation in the choroid, cataracts caused by surgery or worsening of pre-existing cataracts, and most importantly, intraocular infection (endophthalmitis), which is a severe condition that can cause vision loss and blindness.
Glaucoma surgery using a natural-mimicking method or deep sclerectomy is another technique developed based on the principle of draining fluid from the eye and creating a bleb on the eye surface similar to trabeculectomy. The two main differences are the absence of a perforation or connection between the inside and outside of the eye (nonpenetrating filtering procedure) and the creation of an additional fluid reservoir in the sclera (scleral lake). This reservoir lies beneath the scleral tissue flap similar to that found in trabeculectomy (Figures 1 and 2). Since the fluid reservoir must remain as a space, special devices or materials to support the space (space maintainer) are always used in conjunction with deep sclerectomy.
Healaflow (Aptissen, Geneva, Switzerland) is a special type of hyaluronic acid with dense cross-linking (reticulated hyaluronic acid). It appears as a clear and viscous gel (Figure 3) through which aqueous humor can flow and drain normally. It consists of more than 97% water, has a physiological pH of 7.0, and an osmolarity of 305 mOsm/kg. It remains in the fluid reservoir for up to 6 months before being absorbed by surrounding tissues. Healaflow is supplied in a ready-to-use syringe and can be used in trabeculectomy, deep sclerectomy, viscocanalostomy, and tube shunt surgeries. It is safe to inject into the scleral lake, under the scleral flap, and beneath the conjunctiva. Additionally, Healaflow has anti-inflammatory properties, is non-toxic, and has a low risk of allergic reactions because it is not derived from animal proteins.
Indications for deep sclerectomy include patients with primary and secondary open-angle glaucomas, uveitic glaucoma (glaucoma caused by intraocular inflammation), which deep sclerectomy causes less inflammation, and glaucoma in high myopes who are at high risk of choroidal detachment when undergoing trabeculectomy.
Groups that can undergo the procedure but require caution and may have less predictable outcomes include congenital glaucoma, narrow-angle glaucoma, glaucoma caused by angle trauma (post-traumatic angle recession), patients who have previously undergone certain types of laser treatment at the angle, and glaucoma with elevated episcleral venous pressure.
Contraindications for deep sclerectomy include primary and secondary angle-closure glaucomas, neovascular glaucoma caused by abnormal blood vessel growth inside the eye, and ICE syndrome.
Figure 1 shows the bleb on the eye surface after trabeculectomy surgery in the right eye performed previously, characterized by a clear, elevated wall within a limited area (A), compared to the bleb formed by deep sclerectomy combined with Healaflow at 2 months post-surgery in the left eye, which is flat, more widely distributed, and evenly elevated in all positions (B).
Figure 2 shows the bleb on the superior conjunctiva of the left eye (11-1 o’clock) of the same patient 2 years after deep sclerectomy combined with the use of the space maintainer Healaflow.
Figure 3 shows the packaging and Healaflow (Aptissen, Geneva, Switzerland) in a ready-to-use syringe, appearing as a clear and more viscous gel than usual.
Dr. Natamon Srisamran
Glaucoma Specialist Ophthalmologist
Eye and Laser Center, Phyathai 1 Hospital
