Diagnostic Technology
Diagnostic technology for glaucoma is evolving at a rapid pace. Examples of optic nerve imaging technology that aid in the early detection and management of glaucoma are: digital fundus photography, confocal scanning laser ophthalmoscopy (HRT), and optical coherence tomography (OCT). Other important diagnostic measures include gonioscopy, slit lamp examination, perimetry and occasionally ultrasound biomicroscopy. Genetic testing may be indicated in individuals with disease onset before age 50, or for patients with an affected family member with disease onset before age 50.
Medical Management
Many glaucoma medicines—such as prostaglandin analogs, beta blockers, alpha agonists, carbonic anhydrase inhibitors, and combination therapies—are available to lower intraocular pressure (IOP). Prostaglandins often have the best user compliance because they are required only once daily.
FLASH UPDATE
Two new glaucoma drugs will become available in early 2018: netarsudil (Rhopressa®) and latanoprostene bunod (Vyzulta™)
Netarsudil ophthalmic solution (Rhopressa®, Aerie Pharmaceuticals) is a rho kinaseinhibitor administered in the evening to lower IOP in open-angle glaucoma or ocular hypertension by targeting the trabecular meshwork. FDA-approved in December 2017, Rhopressa® lowers IOP by as much as timolol 0.5% for many glaucoma patients. The most common side effect (53%) is conjunctival hyperemia, or eye redness. Other common (approximately 20%) ocular adverse reactions are corneal verticillata (seen within first four weeks; resolved upon discontinuation of treatment), instillation site pain, and conjunctival hemorrhage.
Latanoprostene bunod ophthalmic solution (Vyzulta™, Bausch + Lomb and Nicox) is the first dual-acting prostaglandin analog - nitric oxide donator. FDA-approved in June 2017, this once-daily eye drop lowers eye pressure in open-angle glaucoma or ocular hypertension patients. Vyzulta™ seems to lower IOP by ~1-2 mm Hg more than latanoprost. The most common ocular adverse reactions with incidence ≥2% are conjunctival hyperemia (6%), eye irritation (4%), eye pain (3%), and instillation site pain (2%).
Surgical Management
Minimally invasive glaucoma surgery (MIGS) procedures are generally considered ones that limit surgical manipulation of the sclera and conjunctiva. They take less time and support faster postoperative eye healing than traditional glaucoma surgery, and the microscopic devices are less intimidating to patients. However, these procedures are not always as effective at lowering IOP and may not be appropriate for patients with advanced glaucoma or very high eye pressures. MIGS procedures concentrate on two pathways: 1. Increasing aqueous outflow and 2. Lowering aqueous production. Most MIGS procedures focus on the former and are approved for patients with ocular hypertension and mild-to-moderate glaucoma.
MIGS Procedures that Increase Aqueous Outflow:
The iStent® is currently the most commonly used MIGS procedure in the United States. It is an implantable canal-based device that bypasses the trabecular meshwork. It has the potential to mildly reduce eye pressure in combination with standard cataract surgery and may reduce a patient’s need for glaucoma eye drops.
The Trabectome® is an electrocautery device that ablates part of the trabecular meshwork. When combined with cataract surgery, the Trabectome® can lower eye pressure to the mid-teens. In use since 2004, the Trabectome® indications have broadened to include its use after failed trabeculectomy and in narrow angles.
The Kahook Dual Blade® is a single-use instrument that makes precise incisions of the trabecular meshwork with minimal residual leaflets. It has been shown to reduce IOP up to 25% when combined with cataract surgery, although more studies are needed to determine its efficacy.
The CyPass® Micro-Stent is an implantable suprachoroidal shunt that drains the aqueous into the suprachoroidal space. Implantation of CyPass® is made through a clear corneal incision, which avoids the formation of a filtering bleb. CyPass® is used in combination with cataract surgery or as a stand-alone procedure in patients with mild-to-moderate primary open-angle glaucoma. In the COMPASS Study, more than 98% of the CyPass® Micro-Stent group achieved 20/40 or better best-corrected visual acuity compared to a control group. Over the past year, the use of Cypass® has broadened and some complications have been observed in patients who have severe glaucoma or who are hyperopic. Significant IOP elevation from sudden closure of the cleft and refractive shift can occur in the postoperative period and requires careful monitoring.
The Xen Gel Stent® is an ab interno implantable device that drains the aqueous into the subconjunctival space. Once inserted, a low-lying diffuse bleb is created. According to the clinical trial used for FDA approval, reduced mean IOP was reported to be >25%in >80% of eyes treated, and the mean number of medications was decreased from 3.5 to 1.7.
Trabeculotomies and canaloplasties can be performed using the iTrack™ device, an illuminated microcatheter that allows cauterization and dilation of all components of outflow resistance. According to some studies, it can reduce IOP by up to 34% and medication use by up to 66%. It can be done as a stand-alone procedure or with cataract extraction.
MIGS Procedures that Lower Aqueous Production:
Endoscopic Cyclophotocoagulation (ECP) is a laser procedure that can lower IOP by treating the ciliary processes directly. ECP can be performed in combination with cataract surgery or as a stand-alone procedure. It can be especially beneficial in patients with narrow-angle glaucoma or plateau iris syndrome.
MicroPulse Cyclophotocoagulation is a transcleral, non-penetrating procedure that targets the ciliary processes. It is associated with fewer complications than a traditional diode laser and can significantly reduce IOP. Like ECP, it can be combined with cataract surgery, although care must be taken to control postoperative inflammation.