Do you offer trabeculectomy as a primary intervention in advanced glaucoma?
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Aggressive treatment is necessary
The reason the NICE guidelines advise trabeculectomy at presentation with advanced disease is simply that the greatest risk factor for severe visual loss in glaucoma is advanced disease at presentation.
Randomized clinical trials such as the Moorfields Primary Treatment Trial and the Collaborative Initial Glaucoma Treatment Study have established clearly that trabeculectomy achieves greater IOP lowering than medical therapy in patients with primary glaucomas who have no risk factors for trabeculectomy failure.
In fact, the principal reason that a relatively crude, somewhat unpredictable, 54-year-old procedure that involves laborious early postoperative follow-up and postoperative manipulation is still widely performed, apart from its low cost, is that its efficacy is unmatched by any procedure that has come since.
Given that trabeculectomy is the most effective treatment available, the reasons for offering it at presentation in advanced disease are twofold. First, standard practice in the treatment of glaucoma is to manage the level of treatment aggression according to the rate of disease progression. When planning treatment initially, it is common course to formulate a rough treatment target as to the level of IOP that is most likely to eliminate or at least minimize the rate of glaucoma progression. It is generally accepted that further glaucoma-related optic nerve damage is easier to sustain in situations in which there is already significant damage. Eyes with the greatest damage to start with are therefore at the highest risk for further damage. It became generally accepted over the last 3 decades, reinforced by a post hoc analysis of the Advanced Glaucoma Intervention Study, that patients with advanced glaucoma sustain the lowest rates of disease progression when the IOP is around the lower end of the normal range. The studies listed above clearly show that medical therapy is unlikely to achieve the levels required, and it is widely accepted that trabeculectomy has a significant chance of achieving the required levels.
The second reason is quite simple. In some patients with advanced glaucoma, any progression at all may result in severe visual loss, so an attempt at less aggressive therapy carries a huge potential opportunity cost should it be ineffective and further progression occurs.
Keith Barton, MD, FRCP, FRCS, FRCOphth, is with University College London and Moorfields Eye Hospital, London.
Surgery not necessary in every patient
High-quality randomized controlled trials, such as the Treatment of Advanced Glaucoma Study (TAGS), are the cornerstone of evidence-based practice. However, clinicians still need to judge how to apply the evidence to individual patients.
TAGS enrolled patients with newly diagnosed glaucoma with severe disease in at least one eye. Two options were compared: early trabeculectomy vs. medical management. The results after 2 years of follow-up are important: Surgery is safe and more effective than medications to reduce IOP. The mean IOP at 2 years was 12.4 ± 4.7 mm Hg and 15.1 ± 4.8 mm Hg in the surgery group and medication group, respectively. Other important outcomes such as disease progression and quality of life were not different between the groups.
It would be fair to assume that surgery will be associated with better outcomes with longer-term follow-up and that it should be recommended to all patients diagnosed with severe glaucoma. Not necessarily so. Please consider the following facts.
First, there is a large standard deviation of IOP data; thus, a substantial proportion of patients treated with medications had IOP in the low teens, which may be sufficient to control the disease. In addition, a substantial proportion of patients who underwent early surgery had IOP in the mid-teens, which may not be an optimal IOP.
Second, criteria for trial participation included advanced glaucoma in at least one eye. However, there was a wide range of severities: Mean deviation loss was above –15 dB, with a standard deviation above 6 dB. Decision-making in a middle-aged patient with bilateral advanced glaucoma and mean deviation of more than 20 dB in both eyes is very different from an elderly patient with mean deviation of –12 dB in one eye and mild glaucoma in the fellow eye and with an untreated IOP in the low 20s.
Finally, and most importantly, we need to talk to our patients and understand their values and concerns, visual limitations and what is important to them. Patients with severe glaucoma are vulnerable and need our additional support and compassion in their difficult journey ahead.
- References:
- The Advanced Glaucoma Intervention Study Investigators. Ophthalmology. 1994;doi:10.1016/s0161-6420(94)31171-7.
- Cairns JE. Am J Ophthalmol. 1968;doi:10.1016/0002-9394(68)91288-9.
- King AJ, et al. Br J Ophthalmol. 2018;doi:10.1136/bjophthalmol-2017-310902.
- Lichter PR, et al. Ophthalmology. 2001;doi:10.1016/s0161-6420(01)00873-9.
- Migdal C, et al. Ophthalmology. 1994;doi:10.1016/s0161-6420(94)31120-1.
Augusto Azuara-Blanco, PhD, FRCS(Ed), FRCOphth, is with Queen’s University Belfast, United Kingdom.
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