Glaucoma accounts for 2% of visual impairment and 8% of global blindness. The aim of treatment in glaucoma is to prevent or slow the rate of disease progression by lowering the intraocular pressure (IOP) In patients with medically uncontrolled glaucoma surgical intervention is required to achieve a suitably low IOP.
Minimally Invasive Glaucoma Surgery (MIGS) is a recent development in glaucoma surgery which offer IOP reduction and quick post-operative recovery and reduced post-operative follow-up. The MIGS are usually combined with phacoemulsification but can be performed as solo procedures.
As these are done via an ab-interno approach they are thus associated with minimal trauma, very little or no scleral dissection and minimal or no conjunctival manipulation.
While traditional glaucoma surgeries can be effective, they permanently impact the anatomic structure of the eye.
Glaucoma management has been revolutionized by the introduction of MIGS, a heterogeneous group of procedures that achieve reliable IOP reduction with a favorable safety profile and quick postoperative recovery.
Although the most obvious benefit of MIGS is the lowering of IOP, other potential advantages include reduction of medication load, preservation of the ocular surface, and the decrease of diurnal IOP fluctuation.
Decreasing the frequency of eye drops can be very important to patients susceptible to ocular surface disease.
MIGS is a restorative treatment and unlike traditional glaucoma treatments, which bypass the eye’s natural drainage channels, MIGS restores the natural outflow pathways in order to reduce the elevated intraocular pressure associated with glaucoma.
MIGS works within the natural structures of the eye because no artificial pathways are created and no incisions are made within the visual field of the eye, MIGS has a high safety profile and requires minimal post-operative follow-up.
Most patients can return to normal day-to-day activities almost immediately following treatment.
In minimally invasive glaucoma surgery (MIGS) procedures, like in all glaucoma surgery, careful postoperative care is essential for best surgical outcomes. Furthermore, despite their improved safety profile, MIGS procedures have potential complications that may require additional attention.
The postoperative management of MIGS starts in the preoperative and intraoperative period. Choosing the best MIGS procedure for a patient should involve a discussion of the postoperative course and demands.
A survey of ophthalmologists in the United Kingdom demonstrated that there is a reduction in the number of postoperative visits with MIGS compared to traditional glaucoma surgery; this was most notable with angle-based procedures.
Additionally, 40% of responding glaucoma specialists took this postoperative burden into account when deciding on which procedure a patient should undergo. Glaucoma disease severity is another important consideration.
Goniotomy has been demonstrated to be an effective and safe alternative for patients with severe and refractory glaucoma. However, these patients may be at risk of progression with intraoperative and early postoperative IOP spikes.
Multiple studies have demonstrated that glaucomatous eyes are at an increased risk of IOP spikes in the postoperative period after cataract surgery, which is often due to retained viscoelastic.
Patients undergoing cataract surgery in combination with anglebased MIGS may be at increased risk of this due to the use of extra viscoelastic employed to improve angle visualization.
In these patients, the administration of oral acetazolamide in the perioperative period, specifically 1 hour before surgery, may reduce the risk of IOP elevation and potential vision loss. An additional consideration is the administration of intracameral miotics during angle surgery.
During MIGS, the use of miotics may assist with visualization of the angle. However, there is currently no evidence that the use of topical miotics reduce synechiae formation or improve surgical outcomes. Furthermore, many patients find the side effects uncomfortable.
For these reasons, many ophthalmologists have abandoned the use of postoperative pilocarpine for MIGS.
There is no evidence that the addition of anglebased MIGS to phacoemulsification increases inflammation postoperatively. As such, most of these patients do well with the typical postoperative drop regimen of a nonsteroidal anti-inflammatory plus topical steroid taper for 4 weeks postoperatively.
The presence of a postoperative hyphema in these patients may necessitate an extension of this regimen, because blood in the anterior chamber can be proinflammatory. Postoperative IOP management varies based on surgical goals, disease severity, and preoperative IOP control.
If the patient is poorly controlled on drops preoperatively and the purpose of surgery is IOP lowering, it may be necessary to continue IOP lowering drops. For patients who are well controlled on 1 or 2 drops, it may not be necessary to continue pressure-lowering drops postoperatively.
However, there is increased risk of developing steroidinduced IOP elevations after angle-based procedures, so continuation of pressure drops may be useful while the patients are completing the steroid taper.
Conversely, if the patient has a low IOP and a hyphema in the postoperative period, cessation of pressure-lowering drops may be beneficial to reduce blood reflux into the anterior chamber. Filtering MIGS After Xen Gel Stent (Allergan/Abbvie) placement, there is a need for careful monitoring of IOP and bleb morphology to ensure surgical success.
Although it achieves robust IOP lowering, multiple studies have demonstrated high rates (28% to 43%) of bleb needling. Thus, patients need frequent follow-up for IOP monitoring and bleb manipulation.
For this reason, many ophthalmologists follow these patients at the same frequency as post-trabeculectomy patients.
Cyclodestructive procedures can cause a fair amount of tissue destruction with increased postoperative inflammation, especially in nonWhite patients. For these reasons, it may be necessary to avoid cyclophotocoagulation in darkly pigmented eyes.
Patients with a history of persistent anterior-chamber inflammation or uveitis similarly may not be good candidates.
Angle-based MIGS Iatrogenic cyclodialysis clefts are a rare complication of angle-based procedures, but they can be difficult to manage.
Disinsertion of the ciliary muscle from the scleral spur allows for aqueous humor drainage into the suprachoroidal space, resulting in hypotony and possible shutdown of the conventional outflow pathway.
Medical management with atropine to allow for reapposition of the ciliary muscle to the sclera with reduction of steroid drops to promote scarring may result in closure of the cleft site.
Reports of cleft closure with argon laser, transscleral diode laser, and YAG laser treatment have all been described, as have transscleral diathermy and cryotherapy.
Surgical closure of the cleft may be necessary in patients with large, persistent clefts that have failed less invasive treatments. It is important to counsel these patients on the likelihood of IOP elevation after cleft closure.
Although some patients can be managed with medical therapy until conventional outflow returns after cleft closure, others may require further surgery to lower IOP. A recent report suggests that netarsudil (Rhopressa; Aerie Pharmaceuticals) may be particularly useful in these patients.
Hyphemas are common after angle-based surgery and can typically be managed with topical anti-inflammatory medications. Recurrent hyphemas occur less often and can be secondary to numerous causes; a thorough examination including gonioscopy may help identify the underlying etiology.
Patients with a low postoperative IOP, specifically less than episcleral venous pressure, are at risk of blood reflux.
These patients can be managed with reduction or cessation of IOP-lowering drops. Additionally, patients may experience recurrent hyphemas with pressure on the operative side during sleep, which may resolve by wearing a shield to sleep or with alternations in sleep positioning.
Any time a device is implanted in the eye, there is a risk of malpositioning or migration, with development of uveitis–glaucoma– hyphema syndrome, which should be on the differential for patients with recurrent hyphemas or persistent inflammation.
These require removal of the device and may necessitate incisional glaucoma surgery for IOP management. Xen Gel Stent - Low IOP can result in serous choroidal detachments.
These often resolve spontaneously, but the addition of atropine and steroids to deepen the anterior chamber and reduce inflammation may be necessary for these patients.
Postoperative hypotony may warrant the intracameral administration of viscoelastic materials to reform the anterior chamber and to decrease the flow of aqueous across the device. Dispersive viscoelastic material may be a better option than cohesive viscoelastics to reduce the risk of long-term IOP elevation after administration.
These patients should avoid strenuous activity and straining to avoid the risk of hemorrhagic choroidal detachments. In patients who develop hemorrhagic choroidal detachments, surgery is typically necessary and visual prognosis is guarded.
Another potential complication of Xen stent placement is a bleb leak, which may result from the use of antimetabolites and the high frequency of repeat needling procedures. Initial management depends highly on the clinical examination findings.
Small leaks with formed anterior chambers and no sequelae of hypotony can be managed conservatively with topical antibiotic drops, aqueous suppression, and ointment. Bandage contact lenses may also be useful in these patients to tamponade the leak.
More aggressive leaks can occur due to erosion of the stent through the conjunctiva. In these situations, surgical intervention is necessary.
Multiple approaches exist, including conjunctival dissection with direct closure, repositioning of the stent, removal of the stent with primary closure, and amniotic membrane placement with conjunctival transplantation.
Careful evaluation to rule out endophthalmitis is important in all patients with bleb leaks. MIGS procedures offer improved safety profiles compared to traditional filtering procedures, but complications can still occur and may be difficult to manage.
Routine MIGS can usually follow a postoperative taper that is similar to that used in cataract surgery, but inflammation should be closely monitored to achieve greater surgical success.
Additionally, careful attention should be given to IOP particularly in patients with more severe disease who are at risk of progression with IOP spikes.