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Endoscopic cyclophotocoagulation laser for glaucoma

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Laura Goemann BA
Pacific University College of Optometry, Oregon, USA

Dr Leonid Skorin Jr
OD DO MS FAAO FAOCO
Mayo Clinic Health System, Minnesota USA

 

The focus of current glaucoma therapy is the stabilisation of intraocular pressure (IOP). This is achieved by promoting the balance of production and outflow of aqueous humour using ophthalmic medication or surgical procedures. Surgical intervention is reserved until ophthalmic medication is no longer ideal.

This occurs when the maximum medical therapy fails to reduce IOP to sufficient levels or if it is in the patient’s best interest to discontinue or reduce eye-drop therapy. The patient may have intolerable adverse reactions or compliance issues, or may be unable to afford the medications, as is the case in some countries.

Most commonly-used glaucoma surgical procedures, such as trabeculectomy, aim to increase the outflow of aqueous by altering the trabecular meshwork structure. The production of aqueous can also be addressed surgically. Endoscopic cyclophotocoagulation (ECP) laser targets the ciliary processes of the ciliary body where aqueous is produced. This laser procedure decreases aqueous production by causing atrophy to the ciliary processes.

ECP can be used for most types of glaucoma from mild to severe. ECP has been indicated for the treatment of primary open-angle glaucoma (POAG), normal-tensive glaucoma and secondary glaucomas including pigmentary and pseudoexfoliative glaucoma. It can also be used when angle remodelling surgeries such as selective laser trabeculoplasty (SLT) are contraindicated. These include chronic closed-angle glaucoma, angle recession, plateau iris, neovascular glaucoma, iridocorneal syndrome and difficult to treat congenital glaucoma.1,2 Although there are no absolute contraindications, ECP should not be used in uveitic glaucoma and when the eye pressures exceed 40 mmHg.3

Procedure

ECP utilises a hand-held endoscopic probe that is inserted intraocularly and provides the surgeon with the precision required to selectively target the ciliary body processes, thereby limiting subsequent laser damage to the nearby structures. The instrument approach can be either an anterior approach through the pupil or posteriorly by entering the eye through the pars plana. The pars plana approach is best for aphakic eyes or eyes with a posterior synechiae and uses an incision into the sclera which is placed 3.5 mm posterior to the limbus.2-4 The anterior approach uses a limbal incision. This approach is more commonly used and is suitable for phakic, posterior chamber pseudophakic or aphakic eyes.3

The incision used in phaco-emulsification cataract extraction is easily adapted to the ECP probe, allowing the two procedures to be performed concurrently. Though ECP can be performed independently, combining these two procedures reduces any additional risk to the patient associated with an extra procedure. When combined, the ECP procedure is completed after the cataract has been removed and the intraocular lens (IOL) is in position.

Following IOL placement, viscoelastic is injected underneath the iris to expand the area surrounding the ciliary body. The endoscopic probe is inserted through the limbal incision and directed beneath the iris (Figure 1).

 

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Figure 1. ECP probe placed intraocularly through limbal incision

 

Within the 20-gauge endoscopic probe are four components: a light source, 810 nm diode laser, helium-neon aiming laser and video camera (Figure 2).5 The video feed is directed to a separate screen that the surgeon uses to visualise the procedure.

 

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Figure 2. Endoscopic probe used in ECP

 

A single incision site allows 300 degrees of treatment and a second incision must be placed to treat a full 360 degrees.2 While treatment of 180 degrees is necessary to achieve significant reduction in IOP, treatment should be applied to 360 degrees to reach target IOPs in many adults.4 In paediatric patients, the response is more unpredictable and treatment is applied to 180 to 270 degrees in the initial procedure.4 If the response is insufficient, the surgery can be repeated to ablate the remaining ciliary processes.

During the procedure, each individual ciliary process is visualised while the photocoagulation laser is applied. The foot-pedal-controlled diode laser emits pulsed, continuous energy that is absorbed by the pigment, causing necrosis of the ciliary body epithelium and stroma (Figure 3).2,6 As each ciliary process is treated, it shrinks and becomes whitened (Figure 4).

 

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Figure 3. ECP instrument panel

 

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Figure 4. Ciliary processes viewed during ECP. The whitening and shrinking of the ablated ciliary processes is seen on the right (black arrow). The ciliary processes on the left have not been ablated (red arrow).

 

This visual feedback is useful for the surgeon to monitor for the treatment’s endpoint. If too much energy is applied to a single ciliary process, it may rupture, causing bleeding and reduced visibility.3 Direct visualisation is also important to ensure adequate treatment. In pseudoexfoliation cases, the processes are smaller and covered with pseudoexfoliative material (Figure 5). More energy is required and the laser needs to be placed closer to the process to achieve adequate absorption and atrophy.3

 

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Figure 5. Ciliary processes in an eye with pseudoexfoliation. The pseudoexfoliative material is apparent on the zonules (white arrow) and ciliary processes (red arrow).

 

As with any procedure, there is risk of infection. Therefore, the patient should be prescribed a topical antibiotic beginning three days prior to surgery and continued for one week after surgery. To help with inflammation and prepare the eye for surgery, a topical non-steroidal anti-inflammatory is used for three days prior and one week following the procedure. A topical steroid is also used following surgery, every two hours for the first week followed by a slow taper for one month. This regimen is similar to that of post-cataract care, making the two surgeries even more compatible.

Patients should remain on their anti-glaucoma medications for up to one month following the procedure. This allows the IOP to stabilise. Anti-glaucoma medications should be stopped one at a time at one month intervals if multiple medications were used prior to surgery. The number that can be discontinued will depend on the final target IOP.

ECP versus TCP

While similar in mechanism of action, trans-scleral cyclophotocoagulation (TCP) has an entirely different approach. TCP is done extraocularly through the sclera. The biggest limitation of TCP is the lack of direct visualisation of the ciliary body, leading to increased risk of collateral damage and variable treatment efficacy. A majority of the TCP misses the ciliary body processes and instead affects the pars plana, which is located further posteriorly.2 Even when the application is more accurate, most of the ciliary processes are destroyed only partially. This difficulty arises because the only feedback of the treatment’s endpoint is an audible popping sound, indicating over-treatment has occured.2

The efficacy of TCP is variable due to the nature of the approach. The absorption depends on the thickness of scleral tissue, angle of the probe and the pressure applied against the sclera.2 As little as 35 per cent of the energy emitted during TCP actually reaches the pigmented epithelial cells of the ciliary body, with the remainder being absorbed by other tissues or just being reflected.2,6

Following TCP, patients may experience pain, inflammation, cystoid macular oedema, hypotony and a phthisical eye with permanent vision loss.3 Due to the increased risk of these vision-threatening complications, this blind approach is often reserved for eyes with limited visual potential or severe pain associated with uncontrolled increased IOP.

Efficacy of ECP

The main mechanism of IOP reduction in ECP is the destruction of the secretory ciliary epithelium.6 Additional effects are from vascular damage and ischaemia of the ciliary body processes.6 Due to vascular damage and uveitis, the IOP decreases significantly during the first week, increases over the course of the next month and finally stabilises.6 Following ECP, ciliary epithelial remodelling may occur to a greater extent than with TCP, leading to regression of treatment and increased IOP. However, this newly-remodelled epithelial tissue’s capability to secrete aqueous is unclear.6

A greater reduction in IOP and higher rate of success are seen in eyes with higher preoperative IOP or chronic angle-closure glaucoma.7 Patients with a secondary glaucoma have shown a greater lowering effect on IOP than POAG. Patients with POAG had an average of 22 per cent IOP decrease while secondary glaucoma patients had an IOP decrease of 29 per cent.2 Previous failed glaucoma surgery may also have an impact on efficacy of ECP as patients with no previous surgical intervention showed a decrease in IOP of 30 per cent, while those who had had previous surgeries had a decrease of 17 per cent.2

ECP is safer and comparable in IOP lowering effect when compared against other glaucoma surgeries. A randomised, prospective study found a similar decrease in IOP with a 29 per cent reduction with ECP and a 32 per cent reduction with trabeculectomy.2 One study found no significant difference in effect of ECP compared to that of an Ahmed valve (shunt surgery) at 20 months.6 While the effect was the same, complications associated with the Ahmed valve were more frequent than with ECP.6

Cataract surgery itself perpetuates a certain degree of IOP-lowering effect; however, this effect tends to diminish after two years. When paired with ECP, the decrease in IOP remains significant with an additional benefit of decreased anti-glaucoma medication dependence.3,7 At year three, there is no significant difference in IOP between cataract extraction alone and the combined procedure; however, there is a significant decrease in the number of topical medications used.7 In a study with multiple types of glaucoma, the mean reduction in IOP with the combined procedure was 20 per cent at one year.7 In a Brazilian study of 368 eyes, the average IOP decreased from 23.1 mmHg to 12.1 mmHg at two years. The use of anti-glaucoma medication also was reduced from 1.4 to 0.4 ophthalmic medications.7

When cataract extraction and ECP are combined, the manipulation of the ciliary processes with ECP also has an effect on the position of the implanted IOL. A study of 139 eyes found a significant increase in deviation from the desired refractive endpoint when ECP was performed in conjunction with cataract surgery.1 Eyes which were treated with ECP had an average myopic shift of 0.54 dioptres compared to an average 0.26 dioptres myopic shift outcome of eyes that had cataract surgery alone.1 Therefore, when the procedures are combined, consideration should be made when choosing the appropriate IOL power.

Complications of ECP include endophthalmitis, hyphaema, phthisis bulbi and hypotony although the incidence of these complications is rare. Neovascular and paediatric patients are at higher risk of long-term hypotony. Hypotony in these patients can be averted with more conservative laser treatment.2,6

Conclusion

ECP has been shown to be effective in managing multiple types of glaucoma. It has previously been reserved for end-stage glaucoma due to concerns of potentially visually compromising complications such as hypotony and phthisis bulbi. With the increase in safety compared to TCP, ECP should be considered earlier in the disease process. It should especially be considered in glaucoma patients who are also having cataract surgery as the two procedures can be combined without any significant additional risk.

 

1.            Wang J, Campos-Möller X, Shah M, Sheybani A, et al. Effect of endocyclophotocoagulation on refractive outcomes in angle-closure eyes after phacoemulsification and posterior chamber intraocular lens implantation. J Cataract Refract Surg 2016; 42: 132-137.

2.            Kaplowitz K, Kuei A, Klenofsky B, et al. The use of endoscopic cyclophotocoagulation for moderate to advanced glaucoma. Acta Ophthalmol 2015: 93: 395-401.

3.            Skorin L. Consider ECP for glaucoma. Review of Optometry 2008; 145: 11: 43-48.

4.            Lin S. Endoscopic cyclophotocoag-ulation. Br J Ophthalmol 2002; 86: 12: 1434-1438.

5.            Groehler J, Skorin L. Endoscopic cyclophotocoagulation: A viable treatment for glaucoma. The Indian Optician 2009; 41: 236: 206-210.

6.            Bloom PA, Dharmaraj S. Endoscopic and transscleral cyclophotocoagulation. Br J Ophthalmol 2006; 90: 666-668.

7.            Roberts S, Mulvahill M, SooHoo J, et al. Efficacy of combined cataract extraction and endoscopic cyclophotocoagulation for the reduction of intraocular pressure and medication burden. Int J Ophthalmol 2016; 9: 5: 693-698.



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