GLAUCOMA AND THE IMPROVEMENT OF SURGICAL INTERVENTION

GLAUCOMA AND THE IMPROVEMENTOF SURGICAL INTERVENTION byMichael Salter, MD

Until recently we have been relying on the same surgical techniques to manage glaucoma that were created over 50 years ago. What if we continued cataract surgery the same way for the past 50 years? Many complications existed then like large incisions, higher complications of edema and retinal detachment, and long recovery times.

Surgical techniques are starting to “get with the times.” There are only 4 current targets in glaucoma treatment. 1. Create an alternate way for aqueous to get out of the eye (artificial drain) 2. Decrease the production of aqueous humor at ciliary body. 3. Better facilitate flow through the trabecular meshwork and into Schlemms Canal. 4. Better facilitate flow through the eveoscleral pathway.

A timeline and synopsis glaucoma surgeries

Conventional Penetrating Glaucoma Surgery 1960’s to present This form of surgery bypasses the eye’s natural drainage pathways and is considered the “gold standard” today. The older surgery model involved a tube. High risk of erosion and exposure led to infection with tubes and this led to trabeculectomy or “trab”, “filter” or “express shunt”. “Trabs” can get eye pressure very low and may be option for end stage glaucoma cases, but downside is longer recovery, high incidence of of bleb leaks, shallow anterior chamber, hypotony, and choroidal detachments.

Laser Surgery Argon Laser Trabeculoplasty (ALT) 1974 Selective Laser Trabuloplasty (SLT) 1998 SLT is considered a first line surgical option. It works well, and arguably safer than using drops. It has been compared to prostaglandin drop treatment with similar efficacy. Most glaucoma specialist would prefer to begin treatment with SLT over drop therapy. ALT is not utilized much as it is considered more difficult and requires more precise treatment areas with less room for error.

Laser Iridotomy This is offered to those patients with a narrow angle (where cornea and iris meet). Asians are at highest risk, followed by whites and African Americans. This procedure should be offered to those with a very narrow angle and without evidence of glaucoma as a preventative.

Transscleral Cyclophotocoagulation Pros of this procedure are that it is noninvasive (no risk of infection), it is quick to do (in office), and repeatable. The cons are if too aggressive a robust inflammatory response can occur postoperatively. This surgery must be done under a retrobulbar block (injection of anesthesia behind the globe of the eye).

Micropulse CPC This is a new CPC using the Micro Pulse G6 Laser System. It has been shown to cause very little tissue damage with no incision and a safe procedure for mild moderate and severe cases of glaucoma.

Microinvasive Glaucoma Surgery (MIGS) 2004 to present MIGS is a no stitch glaucoma surgery that can be pe formed through a small clear cornea cataract incision and is commonly done in combination with cataract extraction.

Trabectome – a cauterizing tool that targets and removes the trabecular meshwork.

Kahook Duel Blade – a sharp device that “shaves” the trabecular meshwork.

iStent by Glaukos – the smallest device to be implanted in the human body and FDA approved for mid and moderate stage open angle glaucoma in 2012. Only FDA approved if implanted with cataract surgery. Studies have shown no increase in complications compared to cataract surgery alone. There is some risk with IOP spike and hyphema.

Second Generation iStent Inject This could be approved by the end of 2018 and is considered to be easier to place than the original iStent. It also allows for 2 stents instead of 1.

Cypass Stent – only approved with cataract surgery and creates a “cleft”. Risk are myopic shift, hyphema, hypotony and IOP spikes.

iStent Supra – a suprachoroidal stent FDA approval by 2018-2019.

Hydrus Stent – larger than iStent it bypasses the trabe ular network. Not yet approved by FDA.