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Management of primary open angle glaucoma

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Jenna Cryer
BMedSci(VisionSci) MOptom Flinders University

 

A 54-year-old Caucasian male presented for a general eye examination, wanting to update the prescription in his 11-year-old spectacles. The patient is scheduled to see a local ophthalmologist every six months but had not done so for nine months.

The ophthalmologist had previously prescribed Travatan for the patient’s primary open angle glaucoma (POAG) treatment but it had not adequately lowered the IOPs. For the following 18 months, the ophthalmologist then prescribed DuoTrav nocte; however, due to intolerable side-effects the patient had voluntarily ceased this treatment three months before presenting to update his prescription. Soon after commencing the DuoTrav treatment, the patient had been experiencing mood changes and was unable to wear his soft disposable contact lenses for more than one or two days due to discomfort.

General health was reported as good with no medications and the patient had no known family history of glaucoma, macular degeneration, diabetes or hypertension.

BCVAs were 6/9+ OD and 6/9+ OS with a distance refraction of -7.25/-1.25 x 84 OD and -7.00/-1.50 x 68 OS. Pupils, EOM movements and slit-lamp anterior examination showed no abnormal defects, and open angles were recorded.

Posterior slitlamp examination on VOLK showed an asymmetrical C/D ratio of 0.3 OD and 0.6 OS, with the macular appearing flat and clear. Perkins tonometry results were 21.5 mmHg OD, 28 mmHg OS at 11:15 am.

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Figure 1. HFA 24-2 visual field results OD: no abnormal defects

 

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Figure 2. HFA 24-2 visual field results OS: inferior arcuate and paracentral scotomas

 

Humphrey Visual Field Analyzer 24-2 results of the right eye showed reliable indices, no abnormal defects, GHT within normal limits (Figure 1). The field of the left eye showed reliable indices, GHT outside normal limits and glaucomatous field changes (inferior arcuate and paracentral scotomas) (Figure 2).

OCT optic nerve head analysis of both eyes revealed vertical C/D ratios 0.2 OD and 0.8 OS and showed OS RNFL thinning superiorly and inferiorly and OD RNFL thinning mostly superiorly (Figure 3). This patient was prescribed multifocal spectacles and was asked to return for a dilated fundus examination due to high myopia and for a better optic disc view.

Cirrus HD OCT 5- Line Raster at the next visit five days later showed no abnormalities OD and cystoid macular oedema OS (Figure 4). The patient was referred to the original ophthalmologist in regards to ceasing topical DuoTrav due to intolerable side-effects, the development of left cystoid macular oedema (CMO) and assessment for selective laser trabeculoplasty (SLT).

 

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Figure 3. Cirrus OCT optic nerve head analysis OU

 

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Figure 4. Cirrus OCT HD 5 Line Raster OS showing CMO

 

The ophthalmologist agreed that the patient was receiving some beta-blocker and prostaglandin analogue side-effects (mood changes and CMO). SLT was completed in the left eye one week later and the patient was to have a second session completed.

Diagnosis

The patient was diagnosed with POAG, as he presented with elevated IOPs of 21.5 mmHg and 28 mmHg right and left, along with open anterior chamber drainage angles, high myopia, RNFL thinning on OCT and glaucomatous VF defects in the left eye. The patient’s mood swings could be attributed to the beta-blocker Timolol and the CMO was likely to have been caused by the prostaglandin travoprost in the DuoTrav drops that were prescribed. Contact lens intolerance is also a common side-effect from topical glaucoma medications.

POAG is often bilateral but asymmetric and it has been reported that on average, there is 50 per cent as much damage in the better eye than in the worse eye.1

Other differentials that were eliminated were normal tension glaucoma, ocular hypertension, primary angle closure glaucoma, pigmentary glaucoma (PG), pseudoexfoliation glaucoma, physiological cupping and thick CCTs causing higher tonometry readings.

Discussion

Reducing IOP can slow the onset and progression of glaucoma. The only factor that can be controlled in glaucoma is IOP, therefore current treatments for POAG are aimed at lowering IOP.2,3

The NHMRC guidelines suggest topical hypotensives as the first line of treatment for POAG and this patient was originally started on Travatan 0.004% as prostaglandin analogues (PGAs) have the highest efficacy, the most favourable side-effects and administration required only once daily. Before the patient was changed from Travatan to DuoTrav, Lumigan would have been another treatment option as there is some evidence suggesting it may be slightly more effective than the other PGAs in IOP reduction. This would have depended on how far the patient was from reaching target IOP on Travatan, as the additional IOP decrease from Lumigan is most likely to be only minor.

PGA use can result in reversible macular oedema4 and it is believed that this patient experienced the CMO from the PGA in the DuoTrav drops, due to disruption in the blood-aqueous barrier.5

Although beta-blockers are also considered a first-line medical treatment by the NHMRC guidelines, they have a slightly lower efficacy compared to PGAs and usually need to be administered twice daily.4,6 Beta-blockers require careful consideration before prescribing as systemic side-effects can occur due to the presence of beta-receptors in the heart and lungs. Depression is an associated systemic side-effect and it is believed that the patient’s mood changes were due to the timolol in the DuoTrav.

Although combination glaucoma drops are considered as a second treatment choice by the NHMRC guidelines, a majority contain timolol 0.5%; therefore, changing the patient from DuoTrav to another combination drop may still have resulted in the neurological adverse effects. It is unlikely that a carbonic anhydrase inhibitor, alpha-agonist or miotic would have lowered the patient’s IOP by a greater amount, therefore SLT was the next appropriate option.

Laser trabeculoplasty is the next line of treatment after topical hypotensive failure, or it can be offered as an additive to medical treatment.4 It has been shown to be as effective as initial treatment with topical medication, with average IOP reduction rates ranging between 20 and 30 per cent. 

Because the patient did not reach his target IOP with the initial Travatan 0.004%, and then experienced intolerable side-effects with DuoTrav, SLT was considered. The ophthalmologist agreed with this assessment and SLT was commenced on the left eye. Because the effects of the laser appear to diminish over time, this patient will need to be monitored closely and SLT may need to be repeated.

Surgical IOP reduction is offered when medications and/or laser therapy are unsuitable or fail.4 Filtering surgery is an invasive procedure and therefore the risks and benefits need to be explored, and intensive proactive post-operative care is required.7 It has been shown to have success rates of 75-90 per cent in previously unoperated eyes, and post-operative hypotensives are needed in 15-50 per cent of these patients.4,8 Glaucoma drainage devices provide adequate long-term IOP reduction, but are usually reserved for glaucoma eyes where trabeculectomy is unsuitable or has failed. Filtering surgery may be a future option for this patient once SLT and medical therapy have failed. 

 

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Table 1. Risk factors for the development of POAG

 

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Table 2. Treatment options in Australia for POAG

 

1. Quigley H. Glaucoma. The Lancet 2011; 377: 9774: 1367-1377.

2. Kwon Y, Fingert J, Kuehn M, Alward W. Mechanisms of disease: primary open-angle glaucoma. New Eng J Medicine 2009; 360: 11: 1113-1124.

3. Kass M. The Ocular Hypertension Treatment Study. Arch Ophthalmol 2002; 120: 6: 701.

4. NHMRC. Guidelines For the Screening, Prognosis, Diagnosis, Management and Prevention of Glaucoma. Canberra: National Health and Medical Research Council; 2010. Available at: https://www.nhmrc.gov.au/_files_nhmrc/publications/attachments/cp113_glaucoma_120404.pdf. [Accessed 11 January 2016].

5. Miyake L, Ibaraki N. Prostaglandins and cystoid macular oedema. Survey Ophthalmol 2002; 47: 1: S203-218.

6. Parrish R, Palmberg P, Sheu W. A comparison of latanoprost, bimatoprost, and travoprost in patients with elevated intraocular pressure. Amer J Ophthalmol 2003; 135: 5: 688-703.

7. Kirwan JF et al. Trabeculectomy in the 21st century. Ophthalmology 2013; 120: 12: 2532-2539.

8. American Optometric Association. Optometric clinical practice guidelines: Care of the patients with open angle glaucoma. St Louis: American Optometric Association; 2010. Available at: http://www.aoa.org/documents/optometrists/CPG-9.pdf. [Accessed 11 January 2016].



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