Several new classes of eye drugs over the last few years have had a dramatic effect on eye pressure control, reducing the need for surgery. The four classes of drugs used include:

1. Prostaglandins (increases fluid draining out of the eye)

2. Carbonic anhydrase inhibitors (works by reducing aqueous secretion "turning off the tap")

3. Beta blockers (works by reducing aqueous secretion "turning off the tap")

4. Alpha blockers (dual mechanism of action)

More recently, a new class of glaucoma drug has been developed. These are known as Rho kinase, or ROCK inhibitors. ROCK inhibitors have been shown to increase aqueous outflow by relaxing cells
in the trabecular meshwork and increasing the spaces between them. There also may be some "neuroprotective" benefit. Other drug classes on the horizon include an adenosine-1 agonists. Interestingly some of these drugs may be available as subtenons inserts, meaning that the drops do not need to be instilled but can be implanted just inside the lid / around the eye.

View of iStent on a Sovereign. The iStent is barely visible to the naked eye, and is positioned below the front upper hoof of the horse on the coin. This coin measures 21mm in diameter, and the iStent is less than 1mm in length. This stent is made of titanium and is inserted into the drainage angle to help lower eye pressure. It is a less invasive type of surgery compared to trabeculectomy, with a lower risk of serious complications. Eye pressure reductions with this technique are less than with trabeculectomy however; iStent is a technique suited for those with less advanced disease.

The Xen implant and iStent are both considered as "MIGS" - Minimally invasive glaucoma surgery.

The difference between the Xen implant and the iStent is that the Xen implant is a full thickness device. The iStent is designed to open up part of the trabecular meshwork, whereas the Xen implant is a thin micro-tubule that crosses the trabecular meshwork completely. For more information about the Xen implant, please see the links to the left for another article.

Mr. Bergheim - a founder of the company that now makes the iStent implant - had a close family member who was diagnosed with glaucoma at a young age. In search of a treatment, he contacted Richard Hill, MD, an ophthalmologist at the University of California to discuss treatment options. Trabeculectomy was the recommended therapy and the only viable option at the time. During their discussions, Dr. Hill presented the concept of a trabecular micro-bypass stent. He had spent several years analyzing the clinical potential of implanting a micro-bypass stent into Schlemm’s canal to restore physiologic outflow while avoiding the major drawbacks of invasive glaucoma surgeries. The pair then collaborated with Mory Gharib, PhD, who is the Hans W. Liepmann Professor of Aeronautics and the Professor of Bio-Inspired Engineering at the California Institute of Technology. Mr. Bergheim, Dr. Hill and Dr. Gharib later formed Glaukos and began development of the micro-bypass stent. Dr. Gharib provided the fluid mechanics of the design, as well as technical leadership. Dr. Gharib developed the first prototype and within one year the first human implant of the micro-bypass stent was performed.

Purple arrow: iStent snorkel opening which drains aqueous fluid out of eye
Red arrow: length of iStent

Glaucoma surgery is required in some cases if eye pressure remains high - despite the more conservative measures of laser (such as selective laser trabeculoplasty) or eye drops. Conventional surgery for glaucoma and the gold standard is known as trabeculectomy with mitomycin C. Other alternative approached include non-penetrating surgery (eg viscocanalostomy). Non-penetrating approaches are not generally as effective as trabeculectomy, and are more time-consuming to perform, and may often require laser to scleral tissue after treatment.

Trabeculectomy can be performed with cataract surgery or alone. Mr Galloway prefers to perform cataract surgery ahead of trabeculectomy in most cases, but this is not always required. Glaucoma surgery is performed in an eye theatre, and generally takes 30 to 45 minutes to complete. It is usually performed under local anaesthetic but can easily be done under general anaesthesia. Local anaesthesia is often preferred as the recovery time is quicker, with a shorter hospital visit. If glaucoma is complex, or there has been recent trauma to the eye, general anaesthesia may be preferred.

How is a trabeculectomy performed?

First, eye drops are put in to numb the eye. Local anaesthetic is then given. This may sting for a few seconds - usually about 10 to 20 seconds only. After that, the eye becomes numb, and the vision remains blurred for several hours as a result. Surgery is performed with you lying down. You may be aware of bright lights during surgery. A small pocket of the surface tissues of the eye is created, and an anti scarring medicine is applied to the outer coat of the eye. Then, a small flap of tissue is fashioned to provide a covering over a miniature (less than 1mm) opening made into the eye. The flap covers the opening and is stitched back down with several sutures. 2 of these sutures may be releasable - allowing the surgeon to remove them later quickly. The releasable sutures are buried under the surface, and also buried within the cornea, so can be left alone without issue if there is no need for removal.

Do's and Dont's after glaucoma surgery

* do not rub or press on the eye.
* use the drops as instructed
* continue with normal light daily activities
* avoid splashing soap, water or anything else into the eye
* wash your hair in the shower avoiding getting water into the eye
* be aware that the vision is often very blurred for a number of weeks
* plan to be off work for 2 weeks
* do not carry out strenuous exercise
* do not drive unless, or until, you are told it is safe to do so

Mitomycin C - used in glaucoma surgery to reduce scarring.