The Education Committee carefully selects presentations from the World Glaucoma Congress 2017 in Helsinki for your benefit. This month Dr. Parul Ichhpujani introduces the following sessions: Myopia and Glaucoma, Laser treatment of Glaucoma and MIGS: The Evidence.
Myopia and Glaucoma
- High myopia and glaucoma: Aspects in etiology, anatomy and pathogenesis by Dr. Jost Jonas
- Myopic changes vs. glaucomatous changes by Dr. Kazuhisa Sugiyama
- How to diagnose glaucoma among highly myopic eyes by Dr. Robert Chang
- The retinal nerve fibre layer in myopia- implications for glaucoma by Dr. Vinay Nangia
- 5. Surgical complications in myopic patients by Dr. Ricardo Guedes
Dr. Jonas delivered an enlightening lecture on high myopia and glaucoma. He reported that the axial elongation associated increase in glaucomatous optic neuropathy (GON) prevalence was associated with parapapillary delta zone as surrogate for an elongated peripapillary scleral flange and with larger optic disc size. He showed the potential usefulness of differentiating between parapapillary gamma zone and delta zone, clinically as well as on OCT. He cited his collaborative studies, Central India Eye and Medical study and the Beijing Eye study.
Dr. Sugiyama highlighted the fact that myopic primary open angle glaucoma is a combination of myopic optic neuropathy and glaucomatous optic neuropathy.
He talked about progressive tilting of the optic disc with a nasal shift of the temporal optic disc margin and simultaneous development or enlargement of peripapillary atrophy in childhood with myopic shift. He suggested if GON is predominant, it has frequent disc hemorrhages (DHs), which may cause more progression in visual field (VF) losses. However, when the myopic optic neuropathy or gamma PPA is predominant, it has less DHs and may result in less progressive VF loss.
Dr. Robert Chang spoke on behalf of Prof Mingguang He. He addressed the challenges of diagnosing glaucoma in a patient who is highly myopic.
He talked about the Zhongshan Ophthalmic Center-Brien Holden Vision Institute (ZOC BHVI) High Myopia Registry Study, which provided information about the kind of field defects myopes tend to have.
He suggested the need to compare disc images and visual fields over time, since the rate of change can be slow and to have a more conservative approach, if the intraocular pressure is not elevated.
Dr. Vinay Nangia spoke on Retinal nerve fiber layer thickness in myopia in relation to glaucoma. He highlighted that there were several parameters besides axial length, which influenced the RNFL thickness in myopes. These included the size of optic disc, disc diameter, presence of gamma zone, centration of RNFL circle, pattern of vascular origins from the optic disc and possible asymmetric changes in the axial length of the eye.
Dr. Ricardo Guedes talked about the need to consider the unique traits of myopic eyes before surgical intervention for glaucoma and to choose safer and more conservative approaches, such as MIGS, NPGS, etc. He highlighted that large intraoperative or postoperative IOP fluctuations must be avoided in cases where trabeculectomy is performed. In cases with postoperative hypotony, early intervention must be done to prevent vision loss due to hypotony maculopathy.
Laser treatment of Glaucoma: Evidence Update and Practical Tips
- Trabeculoplasty by Dr. Mark Latina
- Transscleral cyclophotocoagulation by Dr. Paul Chew
- Iridotomy by Dr. Mani Baskaran
- Iridoplasty by Dr. Andrew White
Dr. Mark Latina gave an update on how to best use Selective Laser Trabeculoplasty (SLT) in clinical practice. He talked about choosing SLT early in the course of therapy, as 360 degrees of SLT gives approximately 30% IOP reduction (similar to prostaglandins) with 100% compliance, 85-90% success rate and negligible adverse effects. The efficacy of SLT drops to half if used later as a second line of therapy. He highlighted the value of SLT to the MIGS canal procedures. He introduced the new rotating SLT lens, the Latina indexing goniolens. He also reported a new technique adopted by Dr Michael Belkin, using transscleral SLT without a goniolens, resulting in about 20% IOP reduction.
Dr. Paul Chew spoke on Micropulse Transscleral Cyclophototherapy. He talked about how Micropulse (Transcleral) Pars Plana Phototherapy (MP3) results in increased uveoscleral outflow in a nondestructive, non-thermal manner. The IOP reduction with the MP3 is similar to conventional Transscleral cyclophotocoagulation(TSCPC), but is more consistent and more predictable, without the risk of hypotony.
Dr. Mani Baskaran spoke on evidence updates and practical tips for Laser peripheral iridotomy (LPI) in angle closure disease. He talked about the risk factors for progression despite LPI (older age, male gender, high baseline IOP and diabetes), in light of results of the ANALIS study. Long-term changes in lens vault may decrease the effect of LPI over time. He highlighted that safe practice of LPI with proper training is essential. Temporal LPI is safer in terms of visual symptoms and post LPI gonioscopy is quintessential to ascertain the mechanism of angle closure.
Dr. Andrew White talked about Argon laser peripheral iridoplasty (ALPI) citing the Asia Pacific Glaucoma guidelines. He quoted the need to recognize plateau iris, where this procedure works well. ALPI is also a useful temporizing measure for acute attack of angle closure, lens induced angle closure, but not for chronic angle closure with PAS. He suggested doing an ALPI, after a Pilocarpine test (if IOP drops after 45 minutes of Pilocarpine, then ALPI is likely to work).
MIGS: The Evidence
- Incorporating MIGS into your practice (what MIG for who?) by Dr. Leon Au
- Trabeculotomy by Dr. Sameh Mosead
- iStent by Dr. Lydia Chang
- Hydrus by Dr. Norbert Pfeiffer
- Cypass, iStent Supra by Dr. Carl Erb
Dr. Leon Au advocated the ab-interno MIGS (Schlemmn canal and suprachoroidal surgeries) for their conjunctival sparing and low risk profile for mild cases of glaucoma, with a target IOP in mid to late teens. He suggested ab externo MIGS (XEN, InnFocus) for moderate to severe glaucoma with target IOP in early teens. He emphasised the need to understand the concept well, practice at wet labs and evaluate and then re evaluate the correct patient and appropriate MIGS procedure.
Dr. Sameh Mosaed talked about ab interno trabeculotomy using the Trabectome system. She highlighted the fact that this MIGS procedure can be performed anywhere along the spectrum of the disease and is appropriate for target IOP in mid teens. She talked about the outcome analysis of the available global Trabectome experience and the outcome data from the literature. Broadly, patients undergoing Trabectome had about 30% IOP reduction and a 60% reduction in glaucoma medications.
Dr. Lydia Chang provided evidence for the success and safety profile of the trabecular bypass device, iStent. She said that multiple (2 or 3) standalone iStents (SOLO) provided a good access to the collector channels, achieved 30-40% IOP reduction alongwith reduction in glaucoma medications. Literature review showed Combined Phaco-iStent to be more effective than SOLO iStent.
Dr Chang quoted from literature that both procedures had a sustained efficacy lasting from 36-48 months. Although, more data is needed to comment on the value for money and quality of life with iStent.
Dr. Norbert Pfeiffer talked about the pros and cons of Hydrus microstent. He reported that the proportion of patients with a 20% reduction in washed out diurnal IOP was significantly higher in the Hydrus with concurrent cataract surgery group at 24 months compared with just the cataract surgery group, with no differences in safety.
Dr. Carl Erb talked about the ab interno suprachoroidal stents, Cypass and iStent Supra. He discussed the published literature on efficacy and safety of Cypass in patients with mild to moderate OAG, either as a standalone procedure or combined with phacoemulsification. He highlighted the results of the major randomised trial, COMPASS trial, which showed that nearly 80% of subjects in the Cypass arm achieved an unmedicated IOP decrease versus baseline of ≥20%. Early hypotony and transient hyphema are the common but manageable adverse effects with these stents.