What is minimally invasive glaucoma surgery

Glaucoma is an eye disease that gradually robs the eye of its vision. As Dr. Gonzalez Rodriguez explains one of the treatments for glaucoma is MIGS or minimally invasive glaucoma surgery.

The term MIGS, acronym for Micro Invasive Glaucoma Surgery, was coined by Dr Ike Ahmed of Toronto, Canada in 2009, to designate a series of surgical techniques that must comply with, among others, two main premises:

  1. Do not touch the conjunctiva.
  2. They are performed through a small incision in the clear cornea.

A priori, they present a series of advantages to be taken into account:

  • Faster recovery of visual function.
  • Minimal distortion of the ocular architecture, so they will not generate hardly any refractive changes.
  • Shorter surgical time.
  • Greater safety.
  • Less discomfort for the patient.

With the passing of the years, the appearance of new procedures that fit the definition, the enthusiasm generated in many professionals, the expectations created in more than a few patients, and why not say it, the commercial pressure of the industry, the term MIGS has become a powerful advertising slogan.

But all this clashes with the fact that, to quote Ike Ahmed’s own words, “MIGS techniques are safer because of their less invasive nature, offering modest efficacy”. In other words, so far, MIGS techniques are considered to be surgical techniques of moderate ocular hypotensive efficacy, although it is true that this is a field of research in which many resources are being invested in an attempt to improve this aspect. There is no doubt that not all patients need surgeries considered to be of maximum efficacy (which also carry a higher risk), and may benefit from MIGS techniques at any given time. On the other hand, it should not be forgotten that many of these techniques are especially indicated as a combined procedure, together with cataract surgery (phacoemulsification). It is well known that phacoemulsification itself produces a decrease in intraocular pressure (IOP), due to the changes it induces in the structures of the anterior pole of the eyeball, which is why MIGS techniques are often credited with part of the hypotensive effect of cataract surgery.

But in most glaucoma patients who require surgical treatment, the aim of surgery is to achieve sufficiently low intraocular pressures in the short, medium and, above all, in the long term, to significantly reduce the progression of the disease, so that MIGS techniques may not be enough for these patients with high hypotensive efficacy requirements.

On the other hand, most patients with early glaucoma in whom a moderate lowering of IOP may be sufficient, prefer medical treatment or laser procedures rather than going to the operating room. Although from the physician’s perspective this matter is debatable for innumerable reasons, the subjective perception of the initial glaucomatous patient, who does not feel his disease except for the information we give him, makes him less inclined to a surgical solution for his problem at the first moment of change. In the end, it will be the doctor’s experience, the degree of trust he generates in the patient, and the circumstances of each case that, with good judgment on the part of all, will tip the balance towards one solution or another.

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In which cases is it necessary to resort to this type of surgery?

As a general rule, MIGS are surgical procedures indicated in glaucomas with little or very little glaucomatous neurological damage. Patients with moderate-advanced damage are subsidiaries of surgical techniques that we have called “conventional” here, which have demonstrated superior hypotensive efficacy over many years.

To focus on practical examples, an ideal candidate for a MIGS procedure would be a patient who needs one or two drugs (active ingredients) to effectively control his or her blood pressure, with poor tolerance to eye drops, and who is going to undergo cataract surgery. This is obviously an example, which, although frequent, does not fit the profile of all possible candidates.

The issue of long-term tolerance of antiglaucomatous drops is of importance, which the patient often fails to gauge. The continued use of these drugs in daily instillation eye drops, often several times a day, is not at all innocuous for the ocular surface. There is now general agreement on the deleterious effect of certain preservatives, which can have serious consequences after years of continuous treatment. Preservative-free formulations are the order of the day, but they have by no means put an end to the problem, since the active ingredients are responsible for quite a few side effects that can be serious in some cases; therefore, the perception that many patients have that drugs are the safest procedure to treat glaucoma is not entirely true. From this we could conclude that another suitable candidate for MIGS surgery could be a patient who needs three or more active ingredients to control his or her blood pressure, whether or not he or she is going to undergo cataract surgery.

As can be seen, we could construct numerous examples. What is certain is that MIGS surgeries compete with other therapeutic measures of which we already have a long experience, and which are also presenting novelties and improvements, so the trend is towards individualization of treatment. We must not forget that although the risk is minor, MIGS techniques are surgical techniques that require training and surgical experience on the part of the surgeon. A characteristic of any filtering surgery is that for an optimal result, the postoperative period is as important or even more important than the surgical act itself. Therefore, the best guarantee (if we can speak of guarantees) is that the same surgeon who performs the intervention takes care of the postoperative period, in which the need for specific actions for each procedure will be frequent.