When a patient’s glaucoma cannot be adequately controlled with topical intraocular pressure (IOP)-lowering therapy alone, surgical intervention is considered the next line of defense and it is the optometrist’s role to determine whether a patient is a good candidate for a surgical referral. Prior to considering surgical options, concomitant ocular surface disease (OSD), which is known to be very prevalent among patients who have glaucoma, must be addressed. As is the case with any ocular surgery, a healthy ocular surface will improve the likelihood of a good surgical outcome. Surgical intervention might even be a more desirable option than topical therapy in patients being treated with multiple antiglaucoma drops as toxicity from preservatives in topical antiglaucoma drops has been known to exacerbate OSD.
Here, we define the current glaucoma surgeries, identify the patients who could benefit from a consultation, contraindications, complications and the post-op care relative to each. The O.D.’s role in all the surgeries mentioned is to identify the patients who would benefit from the procedure and to provide education regarding the procedures’ risks and benefits in order to manage patient expectations.
SELECTIVE LASER TRABECULOPLASTY (SLT)
SLT is the use of a frequency doubled Nd:YAG laser to selectively treat the pigmented trabecular meshwork cells without causing structural damage. The exact mechanism by which the laser increases aqueous outflow is not known; however, it is thought that the laser energy causes a biological response that recruits immune cells, such as macrophages, to clean out any debris that has accumulated in the trabecular meshwork.
Patient candidates. The surgery can be used to treat primary open-angle glaucoma, low-tension glaucoma, pseudoexfoliative glaucoma, pigment dispersion glaucoma and ocular hypertension. SLT is indicated as a first-line treatment in patients who have early to moderate stages of disease, for patients whose IOP is not adequately controlled with topical drugs alone and for patients who would like reduced dependence on drops (due to adverse reactions to drops, cost or poor compliance).
Contraindications. SLT is contraindicated in patients who have narrow angles where the trabecular meshwork is not clearly visible, inflammatory glaucoma, neovascular glaucoma, congenital glaucoma, traumatic glaucoma and in patients who are unable to hold a steady position at the slit lamp.
Complications. The most common complications of SLT are a post-procedure IOP spike (measured one hour after the procedure to ensure this has not occurred) and inflammation. Rarely corneal edema occurs, but when it does, it typically resolves in a few days. If necessary, IOP is lowered with topical medication in office. SLT can be repeated, if needed.
Post-op care. The optometrist may perform the procedure in those states (Oklahoma, Kentucky, Louisiana, Alaska and Arkansas) that enable him or her to do so. Regardless of whether the patient is referred to an ophthalmologist for SLT, the O.D. typically sees the patient at a one-week follow-up to monitor inflammation, then four to six weeks post-procedure to monitor IOP. Clinical experience and the literature indicate it ultimately takes about six weeks to see the full effect of an SLT procedure. If the IOP spike is considerably high (> 40 mmHg), which is rare and usually occurs in the first few hours to days following the procedure, the optometrist may consider referring the patient back to the treating surgeon for necessary treatment.
LASER PERIPHERAL IRIDOTOMY (LPI)
LPI involves the use of an argon or Nd:YAG laser to create a small hole in the peripheral iris. This allows a secondary route for aqueous to get to the trabecular meshwork for drainage when its traditional route is impeded by pupillary block.
Patient candidates. This procedure is indicated for primary-angle closure, secondary pupil block, prophylaxis for narrow anterior chamber angles and diagnostically in plateau iris and aqueous misdirection. Of note: Failure to see the entire trabecular meshwork over at least two quadrants, or 180°, of the angle may necessitate a diagnosis of a primary angle closure suspect in your patient, warranting consideration for an LPI.
Contraindications. These are a cloudy cornea, iridocorneal contact due to a flat anterior chamber, angle closure secondary to neovascularization, inflammatory glaucoma or if the patient is unable to hold a steady position at the slit lamp.
Complications. The most common complications following LPI are IOP spikes and inflammation. Patients are monitored one hour post-procedure for IOP spikes.
Other possible complications: hyphema, diplopia, corneal injury, lens opacities, retinal trauma and permanent vision loss.
Post-op care. LPI may be within the O.D.’s state scope-of-practice, or you may need to refer the patient to an ophthalmologist for the procedure. The patient may be prescribed a topical steroid to use four times daily for one-week post-procedure to help control post-procedure inflammation. At the one-week follow-up, the patient should be seen to ensure the PI hole is patent, the angle has deepened and to monitor IOP and inflammation. If a significant hyphema (> grade 1) is seen on any of the post-op visits, or if the IOP is significantly elevated (> 40 mmHg), the optometrist may consider referring the patient back to the treating surgeon for necessary treatment.
ENDOSCOPIC CYCLOPHOTOCOAGULATION (ECP)
ECP aims to decrease IOP by reducing aqueous production. This is accomplished with the use of an 810 nm diode laser attached to an endoscope that targets and destroys the non-pigmented ciliary epithelium. The endoscope is often inserted through a clear corneal incision, allowing this procedure to be easily coupled with cataract extraction; however, the endoscope also may be inserted through a pars plana incision.
Patient candidates. ECP has traditionally been reserved for refractory glaucoma, pediatric glaucoma and cases in which invasive glaucoma filtering surgeries carry too high a risk of complication. More recently, ECP is gaining in popularity for patients who have more mild-to-moderate glaucoma, due to its low risk of complications. Given that ECP can be easily combined with cataract surgery, it is important for optometrists to identify patients who may benefit from this procedure as an adjunct to their cataract extraction. Such patients are those using multiple glaucoma drops and/or are noncompliant with their medications.
Contraindications. If a patient is unable to have intraocular surgery for any reason, ECP may be contraindicated.
Complications. Some possible complications of ECP are inflammation, pain, reduced vision, hyphema, vitreous hemorrhage and cataract formation. There is a very low risk of hypotony with ECP.
Post-op care. The post-op care for ECP is a one-day, one-week and one-month follow-up. Post-op drops are the same as those used in cataract surgery, including a topical antibiotic, steroid and NSAID. Topical glaucoma drops are often continued after ECP, as the procedure does not create a sudden drop in IOP. Topical drops may be discontinued thereafter if sufficient IOP lowering is achieved. If an IOP spike develops and is considerably high (> 40 mmHg), which is rare and usually occurs in the first few hours to days following the procedure, the optometrist may consider referring the patient back to the treating surgeon for necessary treatment.
MINIMALLY INVASIVE GLAUCOMA SURGERIES (MIGS)
MIGS utilize microscopic devices to lower IOP, while causing minimal trauma to the eye. Specifically, they are associated with a decreased risk of complications, such as hypotony, suprachoroidal hemorrhage and choroidal effusion when compared to other traditional, invasive glaucoma surgeries, such as trabeculectomy. MIGS are comprised of trabecular microbypass stents, subconjunctival microshunts and suprachoroidal drainage devices. Most MIGS are performed in combination with cataract surgery; however, some may be performed independently. Trabecular microbypass stents decrease IOP by improving aqueous outflow through its natural outflow pathway via Schlemm’s canal. Subconjunctival microshunts provide an alternative to the traditional pathway for aqueous outflow and can be thought of as a microtrabeculectomy. Suprachoroidal drainage devices increase uveoscleral outflow by draining aqueous into the suprachoroidal space.
Patient candidates. Given their lower risk of complications, MIGS can be used in the early stages of glaucoma. Keep in mind the risk/reward for any MIGS procedures: Trabecular microbypass stents are likely the safest of the three devices, but likely lower the IOP by the least amount. Subconjunctival microshunts will offer the greatest IOP reduction, but carry more risk, as they are essentially a “mini-bleb” procedure. Suprachoroidal drainage devices are in the middle of the two, according to Current Opinion in Ophthalmology. Carefully weigh the need for IOP reduction against the possible risks of the procedure when recommending a procedure to a patient.
Additionally, optometrists should keep MIGS in mind when referring their mild-to-moderate stage glaucoma patients for cataract extraction, as these combined procedures could reduce the number of topical glaucoma drugs a patient is taking and potentially eliminate issues related to poor patient compliance with topical drugs.
Contraindications. These can include inflammatory glaucoma, angle closure, neovascular glaucoma and other types of secondary glaucoma.
Complications. The most common complications of MIGS are temporary IOP spikes and hyphema. The downside to MIGS is that some of the devices typically do not reduce post-operative IOP as well as the more invasive glaucoma surgeries.
Post-op care. The post-op drops and follow-up schedule for MIGS are the same as traditional cataract surgery. Gonioscopy should be performed within the first few weeks following surgery to ensure the implanted device is in the correct position and not obstructed. If a significant hyphema (> grade 1) is seen on any of the post-op visits or if the IOP is significantly elevated (> 40 mmHg), the optometrist may consider referring the patient back to the treating surgeon for necessary treatment.
GLAUCOMA DRAINAGE IMPLANTS
Glaucoma tube shunts involve tube insertion into the anterior chamber through a scleral fistula to drain aqueous to an episcleral reservoir created by an endplate. Tube shunts can be valved or non-valved. Valved shunts lower IOP immediately following surgery, as they allow aqueous to leave the eye when IOP is above a certain IOP (relative to the patient). Non-valved devices rely on the formation of a capsule around the endplate to provide resistance to aqueous outflow; however, formation of this capsule can take about four to six weeks following surgery. These shunts are partly occluded with sutures that will temporarily restrict aqueous outflow until the capsule is formed. One non-valved device, in particular, is placed under a partial-thickness scleral flap to allow aqueous to drain from the anterior chamber into a subconjunctival bleb. Essentially, it works as a modified trabeculectomy, without the peripheral iridectomy. Potential post-op complications are similar to that of trabeculectomy; however, the frequency of complications is lower.
Patient candidates. Glaucoma drainage implants are typically reserved for more advanced stages of glaucoma, including refractory glaucoma, neovascular glaucoma, inflammatory glaucoma and when trabeculectomy has failed or has a high risk of failing.
Contraindications. If a patient is unable to have intraocular surgery for any reason, tube/shunts may be contraindicated.
Complications. Complications of tube shunts are hypotony, choroidal effusion, choroidal hemorrhage, erosion of overlying conjunctiva, corneal endothelial damage by the tube, obstruction of the tube/shunt lumen, endplate migration, diplopia from improper endplate placement or scarring and infection.
Post-op care. Glaucoma drops are typically continued during the post-op period for non-valved procedures, but are typically discontinued in valved procedures, as the IOP lowering effect is immediate. Other post-op drops are topical antibiotics and topical steroids. The post-op follow-up schedule is typically one-day and one-week post-tube/shunt surgery. If any of the above complications are noted on any follow-up visits, the co-managing O.D. may want to consider referring the patient back to the treating surgeon. Glaucoma drainage implants may worsen OSD, so optometrists should also monitor for signs and symptoms of dry eye post-operatively.
TRABECULECTOMY
This is a surgical procedure that involves the creation of a partial thickness scleral flap into the anterior chamber and iridectomy, allowing an alternate route for aqueous outflow through a subconjunctival filtration bleb.
Patient candidates. Trabeculectomy is indicated for advanced stages of glaucoma when a low target IOP is required and when IOP is inadequately controlled through more conservative methods, such as topical medications, lasers and MIGS.
Contraindications. If a patient is unable to have intraocular surgery for any reason, trabeculectomy may be contraindicated.
Complications. Possible early post-op complications are bleb leaks, shallow anterior chamber, hypotony, suprachoroidal hemorrhage, choroidal effusion and infection. Late post-op complications are discomfort, bleb leaks, bleb failure and cataract development. Of the glaucoma surgeries discussed, trabeculectomy requires the most intensive follow-up schedule via surgeon. All patients should be seen for a one-day post-op; then, if there are no complications, they should be seen weekly for the next three weeks. If no early post-op complications have occurred, the surgeon may release the patient back to the care of the referring optometrist.
Post-op care. After the initial follow-up period described, typically, patients are then seen every other week for the next two months. At every post-op visit, the appearance of the bleb needs to be evaluated closely. Ideally, the bleb should be diffuse and elevated with minimal inflammation or vascularization and no leaks. A Seidel test should be performed at every post-op visit, as leaks can occur in the early or late post-operative period. If a leak is noted, the patient should be referred back to the surgeon for additional intervention. Filtering blebs can worsen OSD, so optometrists should also monitor for signs and symptoms of dry eye post-operatively.
STAY IN THE KNOW
With advances in technology and surgical techniques, the options are continually expanding. As a result, as primary care providers, it is crucial optometrists stay up-to-date on the latest glaucoma surgery advances, so they can determine patient candidacy (which includes taking into consideration the condition of the patient’s ocular surface), provide related education to meet patient expectations and close the loop on care post-operatively. OM
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