The Surgical Decision-Making Process

1. Essentials of Glaucoma Therapy
2. Introduction to Basic Concepts of Glaucoma Surgery
3. The Surgical Decision-Making Process

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Surgical Anatomy →

Primary authors	Kathryn L. Pepple, MD, PhD R. Rand Allingham, MD

Glaucoma is a potentially blinding disease, affecting 2% to 3% of the United States population, that includes a group of diseases with a characteristic optic neuropathy and typical pattern of progressive vision loss. Glaucoma is also a disease that can progress to blindness, even in the treated patient population. Lowering intraocular pressure (IOP) is the only intervention that has proven successful in halting or delaying the rate of visual loss over time. Initial therapy for most forms of glaucoma center on medical and/or laser therapy. When these therapies fail to control the disease process, surgical intervention is generally recommended.

Although each patient represents a unique combination of factors that relate to disease process, comorbid conditions, and social and other factors that require individualized care, there are helpful guidelines that can assist the decision-making process regarding when to offer surgery and which procedures to recommend. Surgical techniques have evolved dramatically over the years and, along with new technologies and approaches, promise to improve outcomes. In the following chapter, we will discuss when to pursue surgical intervention and how to choose the most ­appropriate procedure (Table 1-1).

The Decision to Proceed to Surgery

Table 1-1. Factors that Should Be Evaluated in Trabeculectomy, Glaucoma Implants, or a Cyclodestructive Procedure

Factor	Trabeculectomy	Glaucoma Implant	Cyclophotocoagulation
Postoperative intraocular pressure requirement	Need for IOP <13 mm Hg	IOP in mid-teens or higher	Reduction of IOP from current level
Need to reduce or eliminate glaucoma medications	Likely to eliminate medications in near term	Likely to reduce need for ­glaucoma medications, not likely to eliminate	Unpredictable, usually medications required
Long-term risk of postoperative infection	Moderate, 1% per year	Rare	No increased risk
Average period of success	5 years	5 years	Variable
Need for frequent postoperative appointments	High	Moderate	Low
Complexity of postoperative care	High	Moderate	Low
Risk of visual acuity loss	Low to moderate	Low to moderate	Moderate to high
Risk of postoperative complication	Moderate to high	Moderate	Low to moderate
Open angle glaucoma (OAG) or exfoliation glaucoma, pigmentary glaucoma with no prior incisional surgery	Generally first option	Considered if additional factors (eg, difficulty with postoperative care)	Rarely performed
OAG or exfoliation glaucoma, pigmentary glaucoma with prior incisional surgery	Good option if conjunctiva acceptable	Good option in most cases	Rarely performed unless reduced visual acuity or other factors present
Inflammatory glaucomas, neovascular glaucoma,­ traumatic glaucoma (major ocular trauma)	Poor to fair option, only if conjunctiva acceptable	Good option	Fair option depending on visual acuity, increased risk of hypotony or phthisis with poor aqueous outflow (eg, extensive angle closure)
Glaucoma of infancy or early childhood (after goniotomy or trabeculotomy if indicated)	Poor to fair option, depending on ability to comply with surgical regimen	Good option	Option in cases with poor visual potential or after surgical glaucoma procedures

There is a large body of information that outlines the process for the initial diagnosis of glaucoma, how to establish an appropriate target IOP, and how to initiate management with either medical or laser therapy. Before proceeding with surgery, it is essential to step back and take a fresh look at the patient. One wants to discover that the patient was taking steroid-containing medications, has early angle closure, or has not been adherent with medications before performing a major surgical intervention. From this point further, we will assume that a correct diagnosis of glaucoma has been made and that, as part of the patient’s ongoing care, there is a need for surgical intervention.

The most common indication for surgery is when, despite maximal medical and laser therapy, visual field loss or optic nerve damage continues. Surgery is also pursued when the likelihood of progression with the current management plan is judged to be high. When maximal medical and laser therapy has failed, patients will frequently fall into 1 of 2 categories: either the patient is seemingly “well” controlled (goal IOP achieved) or “poorly” controlled (goal IOP not achieved). When progression occurs with a presumably therapeutic IOP, this suggests that a lower target IOP is required. In the poorly controlled group, progression indicates a failure of drug and laser therapy to achieve the goal IOP. Surgery may be required for patients who cannot tolerate topical medications or those who are not able to adhere to the prescribed medical regimen. Less commonly, patients may present with previously undiagnosed and advanced glaucoma or an acute glaucomatous condition. Often, these patients will need rapid IOP lowering, which is unlikely to be achieved with medical or laser therapy. However, these modalities will often be attempted over a short-term window to give less invasive therapies a chance to begin the process of IOP lowering and to prepare the patient for the need for surgery.

The Collaborative Initial Glaucoma Treatment Study (CIGTS) was conducted to determine the role for surgery versus medical therapy as initial management for patients with newly diagnosed open-angle glaucoma. The medical arm allowed the use of currently available topical medications, whereas the surgical arm consisted of trabeculectomy with or without 5-fluorouracil (5 -FU). Each arm had the intention of lowering IOP to a target IOP that was assigned as a function of the baseline IOP and initial visual field, such that patients with more severe disease had lower target IOPs. After controlling for vision loss from postoperative cataract progression, no difference was found in disease progression between the medical versus surgically managed groups. This result suggests early surgery has a role in glaucoma treatment; however, the risks of serious postoperative complications (eg, endophthalmitis) have historically encouraged a more conservative approach among practitioners.

Discussing Surgery With Your Patients

For many patients, understanding the balance between the risks and benefits of surgery is difficult. Many glaucoma patients have excellent central vision, so they understandably feel that there is nothing “wrong” with their vision. In these cases, there is a need to discuss how glaucoma causes vision loss and why surgery is required despite seemingly good vision. Due to the chronic nature of this disease and typically slow rate of progression, most patients will require several visits before surgical procedures are scheduled. Familiarizing patients with their visual field results and how they have progressed over time can be an effective approach to educate patients about vision loss in glaucoma and help them to understand the need for incisional surgery.

Regardless of the type of surgery, it is very important that the patient understands the risks of the procedure so they can be weighed against the benefits. In this era of high-precision cataract and refractive surgery, patients can easily have unrealistic expectations for glaucoma surgery. Specifically, the patient needs to understand that the intent of glaucoma surgery is not to improve vision but rather to prevent continuing vision loss. Patients also need to be cautioned that if they are phakic, glaucoma surgery will likely cause progression of cataract development. In addition, it is important to explain that there may be a need to continue eye drops even after a successful surgery. The most serious risks of glaucoma surgery include infections such as endophthalmitis and blebitis, suprachoroidal hemorrhages, retinal detachment, choroidal effusion, and hypotony with or without maculopathy. The incidence of more serious complications varies in the literature and, although uncommon, they are not rare and carry significant morbidity. Therefore, the balance of the risk of long-term vision loss from glaucoma versus the risk of short-term visual loss from surgical complications must be addressed by the treating physician and understood by each patient.

Choosing an Operative Technique

Two main categories of surgery are commonly offered to adults with glaucoma: trabeculectomy and glaucoma implants, sometimes called tube shunts. Less commonly performed glaucoma surgeries are goniotomy, trabeculotomy, and laser photocoagulation of the ciliary body. Goniotomy and trabeculectomy are more common in the pediatric glaucoma population, whereas photocoagulation of the ciliary body with endocyclophoto-coagulation (ECP) and transscleral diode cycloablation (TDC) are generally utilized in the later stages of the disease or in refractory or end-stage glaucoma patients.

Answering a few questions about your patient can help determine which surgical intervention is most appropriate: (1) What is the target IOP? (2) Has he or she had prior glaucoma surgery? (3) Does the patient have a secondary form of glaucoma such as neovascular glaucoma or uveitis? For maximum IOP lowering, trabeculectomy with mitomycin C (MMC) is usually considered the gold standard for IOP reduction into the teens or upper single digits. However, it is rarely the appropriate choice for patients with secondary forms of glaucoma, such as neovascular glaucoma or uveitis. Glaucoma implant surgery (eg, Baerveldt, Ahmed, or Molteno) is commonly used for eyes that have failed prior trabeculectomy or other ocular incisional surgery or in cases in which trabeculectomy, with or without antifibrotic treatment, has a high probability of failure. However, glaucoma implant surgery is increasing in popularity among surgeons.

This section on Choosing an Operative Technique is a very general framework for the considerations of surgical management, and additional information will generally be required to customize treatment for the individual patient. These considerations will be explored in more detail in the chapters that follow. In general, most patients can be divided into 2 groups. The first consists of patients with open-angle forms of glaucoma, including primary open-angle glaucoma (POAG), normal-tension glaucoma (NTG), and patients with noninflammatory secondary forms of glaucoma, such as pigment dispersion, exfoliation, and adult developmental glaucomas (eg, Axenfeld-Rieger syndrome). For this group, a trabeculectomy with or without antifibrotic agents is most commonly performed as a primary surgical procedure. However, glaucoma implants are increasingly being performed for glaucoma occurring in younger patients, particularly infants, and in patients with higher risk for postoperative inflammation. A variation on the traditional trabeculectomy uses the Ex-Press mini shunt (Alcon, Fort Worth, Texas) to enter the anterior chamber in place of an incisional sclerostomy. The Ex-Press mini shunt is a stainless steel device, that has a flat metal plate positioned under the scleral flap and a 50-µm tip that is inserted into the anterior chamber. The shunt provides a more predictable rate of flow than the traditional sclerostomy, does not require an iridectomy, and the resultant blebs tend to be lower. If a primary trabeculectomy fails, one may consider repeat trabeculectomy or glaucoma implant surgery. In cases in which repeat surgery fails to control IOP within the target range, cyclodestructive procedures such as TDC and ECP are a final option.

Patients with inflammatory forms of secondary glaucoma, such as neovascular glaucoma and uveitic glaucoma, have a high rate of trabeculectomy failure due to scarring and fibrosis of the sclerostomy and bleb. In these cases, glaucoma implants are frequently chosen for primary surgery. In patients with a significant inflammatory component to their disease, some surgeons feel that use of a valved glaucoma implant (eg, the Ahmed glaucoma valve [New World Medical, Inc., Rancho Cucamonga, California]) versus a nonvalved glaucoma implant (eg, the Baerveldt implant [Abbott Medical Optics, Santa Ana, California]) reduces the risk of postoperative hypotony and its attendant complications. If the target IOP is not achieved after trabeculectomy or glaucoma implant surgery, an additional implant or cycloablation type of surgery can be performed.

To avoid the postoperative complications associated with the more common procedures such as trabeculectomy with antimetabolites and tube shunts, newer IOP-lowering technologies continue to be developed. Examples of new technologies include canaloplasty, the Trabeculotome (Katena Eye Instruments, Denville, New Jersey), the iStent (Glaukos Corp., Laguna Hills, California), and the SOLX suprachoroidal shunt (SOLX, Waltham, MA), and their potential uses will be more fully explored in further chapters. Due to their recent emergence, there is limited data on their long-term safety and efficacy, and none have been compared in randomized controlled trials with established surgeries. However, if proven effective, these new technologies could offer the possibility of IOP lowering without the complications associated with blebs or large extraocular implants.

Conclusion

Many options for IOP-lowering surgery are available to the glaucoma surgeon. Choosing the course of therapy that offers the greatest likelihood of success and the fewest return trips to the operating room is an important strategic goal. Keeping abreast of new techniques that improve success and/ or reduce the risk of complications is key to the optimal management­ of this chronic disease.

Key Points

1. The decision to proceed to surgery requires balancing the risks and benefits of surgery against the risk of progressive vision loss.
2. The surgical technique you choose should be influenced by each patient’s unique disease presentation and his or her prior treatment history.
3. Preoperative patient education is a key factor in establishing appropriate expectations for postsurgical goals and outcomes.