Glaucoma is a clinical condition that is characterised by an increase in the pressure within the eyeball. It results in an alteration in vision and a number of other consequences. While there does exist a medical therapy in managing glaucoma, surgical management remains one of the best ways to treat this condition.
In this article, we shall briefly review the different surgical options available in treating glaucoma.
1. Laser trabeculoplasty
Within the eyeball exists a trabecular meshwork through which circulation of the vitreous humour which is the fluid within the eyeball occurs. An alteration in the structure of this trabecular meshwork is called a trabeculoplasty. Trabeculoplasty that is performed using laser is called a laser trabeculoplasty.
The primary indication for the use of laser trabeculoplasty is open angle glaucoma. Typically, there are two different types of lasers that may be used in this procedure. The first type is argon laser trabeculoplasty where an argon laser is used to create tiny holes within the trabecular meshwork. The next type is selective laser trabeculoplasty which involves the use of a specialised laser called Nd:YAG laser. This laser can be directed on certain cells specifically without causing damage to the surrounding structures. This makes it a better procedure when compared to argon laser trabeculoplasty. However, it appears that selective laser trabeculoplasty does not use the same power laser as argon laser and therefore patients may require repeat treatments in the future. Either way, the outcomes appear to be rather good with both the types of lasers.
The complication rates with laser trabeculoplasty are rather low but must be borne in mind. Following the procedure, patients may experience an increase in their intraocular pressure. On occasions, then maybe small capacity is seen on the corneal surface or patients may develop mild inflammation of the iris. An accumulation of blood in the anterior chamber (Called hyphema) can also be seen.
The iris is a circular tissue that is present within the eyeball. An iridotomy is a clinical procedure where small holes are made within the iris using either a laser or small surgical instruments. The holes allow for free circulation of fluid within the eyeball, thus promoting a reduction in the pressure within the eye. Typically, laser iridotomy is used in the management of angle closure glaucoma. As is the case with laser trabeculoplasty, an argon laser or an Nd:YAG laser is used to create the hole. The hole may be created at the bottom of the iris to promote drainage.
An iridectomy is a clinical procedure that involves the removal of a small portion of the iris. There are different kinds of iridectomy procedures that can involve either removal of the iris tissue at the periphery (called a peripheral iridectomy) or near the root of the iris or removal of a section of the iris tissue called sector iridectomy. An iridectomy once performed can result in an alteration in the shape of the people. Once again, this procedure is fairly beneficial in patients with glaucoma.
In the event that the trabeculoplasty fails, it colectomy may be offered to the patient. The procedure is fairly straightforward and involves the removal of a small amount of the sclera to obtain access to the trabecular meshwork. Once this has been done, a small part of the technical meshwork is removed and this allows for free flow of the aqueous fluid. In essence, it involves the creation of an alternate path that allows for free drainage of fluid.
When it comes to management of raised intraocular pressure i.e. glaucoma, the primary surgical treatment that is available is called filtering surgeries. There are different kinds of filtering surgeries but broadly classified they are defined as penetrating and non-penetrating surgeries.
Amongst the penetrating surgeries, there are protected surgeries, partial thickness filtering surgeries and subscale surgeries along with full thickness procedures. For example, a trabeculectomy is a protected filtering surgery that involves the removal of a small portion of the trabecular meshwork. Sometimes, filtering procedures can include an anterior sclerotomy where a small channel is created that allows for free drainage of aqueous fluid onto the surface of the eyeball.
Full thickness procedures within the penetrating surgery subtype can include posterior lip sclerectomy, thermal sclerotomy and sclerostomy. The main principle behind penetrating surgeries is the surgical procedure that is performed involves penetration of the anterior chamber of the eye.
Within non-penetrating surgeries are two different types - bleb forming surgeries and viscocanalostomy. The former procedure can include either a deep sclerectomy or an ab externo trabeculectomy.
The primary surgical technique involved in non-penetrating surgeries involves excision of the Schlemm’s canal. An incision is made on the sclera and a small flap is elevated to expose the canal. Once it has been done, free flow of the fluid within the eyeball occurs resulting in a reduction in pressure. However, following surgery, additions may develop and this can be prevented by the use of certain biocompatible devices such as the Ologen collagen matrix or Aqua flow collagen wick.
Complications from filtering surgeries
Patients who undergo filtering surgeries have a small risk of developing complications. Some of the common ones include the development of low intraocular pressure, accumulation of blood in the anterior chamber, endophthalmitis and transient elevation in the pressure within the eyeball. Some patients may be a risk of developing cataracts.
Glaucoma is a clinical condition that can result in numerous clinical symptoms. Treatments can be medical but therapeutic options offered to the patient are often surgical. Long-term outcomes can be rather good and a stepwise approach needs to be adopted in the management in initial stages. Of course, complications can occur as is the case with any procedure but these are rare when performed by experts.