Glaucoma | IOA Madrid
When we diagnose a patient with glaucoma, the only modifiable risk factor is the intraocular pressure. Decreasing the intraocular pressure to target limits enables in most cases to slow down and even stop the progression of this pathology.
In this task, the initial action is the treatment with topical medication, that is, with eye drops. There are different families and protocols, yet we can divide them into two:
- Monotherapy: Only one drug is applied, it is the first-line treatment for glaucoma with not excessively high pressures when diagnosed. The most used drugs in this case ate beta blockers and analogues of prostaglandins. The first reduce the production of the aqueous humor produced by the eye (“they close the tap”) and the second increase the drainage of the aqueous humor through the episcleral, an alternative path to the iridocorneal angle that enables significant decreases.
Combined therapy: More than one drug is applied in the same eye drop. Usually a beta blocker is combined with another active ingredients, either analogues of protaglandins, inhibitors of carbonic anhydrase, alpha-agonists, etc. It is used mainly when the isolated monohterapy has not achieved a desired targeted PIO, or if there is intolerance to the active ingredients separately.
The current trend is the use of single-dose eye drops and free of preservatives with the aim of preserving the external surface of the eye and not create undesired intolerance, as they chronic treatments and one of the most frequent causes of the poor compliance of the treatment is the presence of adverse reactions to it, usually caused by ABAK (benzalkomium chloride) preservatives in eye drops.
Laser treatment in glaucoma is widely spread. We mainly use two modes, iridotomy and trabeculoplasty.
- Iridotomy: Consist in performing an orifice with YAG laser in the upper part of the iris that enables a communication between the anterior and posterior chamber of the eye. This orifice allows us an escape valve of the aqueous humor in cases of severe closed angle glaucoma and papillary blocks, typical of patients with very thick chambers, severe hyperopia and very mature cataracts. It is a safe procedure that is carried out on an outpatient basis with topical anaesthetic, and that requires myosis (making the pupil smaller), so the day of the operation the patient may have blurred vision.
- Trabeculoplasty: Consists in applying laser in the anatomic area of the iridocorneal angle, more specifically in the pigmented area of the trabeculum. It is indicated for patients who do not tolerate well the medical treatment with drops, as a previous step to consider a surgical operations and especially in patients with pigment and pseudo-exfoliative glaucoma, with an obstruction due to extra cellular matter in the pre-trabecular anatomical area.
- There are two types of lasers to carry out this procedure:
- ALT Laser (Aragon Laser Trabeculoplasty): Consists in making small burns in the trabeculum with the aim of stretching the fibres and reduce the flow-passage resistance at this level. 180 ocular degrees are usually treated, to preserve the rest in case a re-operation is necessary. It is a safe, simple and outpatient basis procedure..
- SLT laser (Selective Trabeculoplasty): This is another type of ocular laser with a lower threshold, that enables performing the same function as the previous without producing visible burns, and therefore tissue damage. This procedure is performed with the same protocol as the previous, although in some occasions repeated treatments are required to obtain an acceptable target pressure, as it loses effectiveness over time.
The surgical treatment of glaucoma has evolved greatly over the past years. The main objective of any operation in glaucoma is to reduce the intraocular pressure enough to slow down and even definitely stop the loss of nervous fibres of the optic nerve, that secondarily cause a progressive loss of the visual field.
We classify glaucoma surgery treatment int two main groups:
- Perforator surgery:
In this technique a fistula or connection is produced between the internal part of the eye (anterior chamber) and the subconjuntival, episcleral or suproachoroidal area, causing a reduction or flow of the eye pressure in that direction. Via epiescleral venous drainage and circulating venous flow. This group causes a significant reduction of the intraocular pressure. There are different techniques:
- Trabeculectomy with express implant: : Modification of the anterior that causes possible complications such as hyphema or bleeding in the anterior chamber, choroidal detachment and post-surgery ocular hypotonia
MIGS:A new branch of surgery that is revolutionising surgical treatment, as it achieves reasonably low pressures, with minimum risk, as the incisions are smaller than 1 mm. Among them, the most frequently performed is the surgery with Xen valve, which is a device with collagen that is inserted an internal in the anterior chamber, and causes a fistula between the intraocular part and the subconjuntival space.
Valves (Ahmed and Molteno): Are external reservoirs that are indicated for highly refractive cases such as neurovascular glaucoma. It is a very simple and useful technique that provides a stable pressure in these cases that due to their complexity and development, require a step further than the conventional techniques.
- Non-perforator surgery:
In this surgical technique a fistula is not performed, that is, there is no continuity solution between the internal and the external part of the eye. Between them we leave a tissue layer (we respect it) Descemet membrane that allows flow passing through it. The major advantage of this technique is the low frequency of intraocular complications, such as infections, eye hypotonia. It requires a greater technical skill and the use of antimetabolites such as mitomycin C and collagen suprachoroidal implants (SK, Gel, Esnoper, etc.) to maintain a good scleral lake that keeps the intraocular pressure down.
All these surgical techniques are carried out on outpatient basis.
The most frequently used anaesthetic is peribulbar, so that the patient does not feel anything during the operation, although on some occasions (especially with MIGS techniques) drops can be used.
In most cases it is recommended to perform cataract surgery at the same time, which is known as combined surgery.