It has been suggested that an option to slow progression of visual field defects in optic nerve head drusen (ONHD) is to initiate treatment with ocular hypotensive agents. The treatment rationale in ONHD is similar to that in glaucoma management: by reducing intraocular pressure and therefore mechanical pressure on the optic disc, further retinal nerve fibre layer damage will decelerate or halt progression altogether. But is there evidence for its efficacy in the literature?
The overall prevalence rates of visual field loss in individuals with ONHD have been reported at 49–79 per cent.1-4 Not surprisingly, the likelihood of visual field loss corresponds to reduced retinal nerve fibre layer (RNFL) thickness on optical coherence tomography (OCT), which can often mimic glaucomatous RNFL thinning.5 Literature on visual field progression in ONHD is severely lacking, with no studies using standard automated perimetry to date. Visual field progression on Goldmann kinetic perimetry has been reported to occur in 22–42.9 per cent of individuals with ONHD.4-6 One study using the same technique found a mean annual visual field loss of 1.58 per cent per year, however these results cannot be directly compared to current static perimetry techniques used in Australian optometric practices.7 Two case reports of individuals with ONHD described rapidly progressive and symptomatic visual field constriction.8,9
ONHD AND OCULAR HYPERTENSION
It has been postulated that elevated intraocular pressures (IOPs) result in an accelerated apoptosis of the already compromised RNFL in ONHD.10 One study found that 90.9 per cent of patients with ONHD and ocular hypertension (OHT) showed visual field loss compared to 66.6 per cent of cases with ONHD only, and that OHT imparted a 6.6 times increased risk of visual field loss.10 Conversely, another study found no significant correlation between IOP and visual field mean deviation or RNFL thickness on OCT.11 At this stage, there does not appear to be a consensus on whether elevated IOP increases the risk of visual field loss.
EFFICACY OF OCULAR HYPOTENSIVE AGENTS ON SLOWING PROGRESSION
In the only study to date on ocular hypotensive agents and ONHD progression, treatment with brinzolamide appeared to slow RNFL progression on OCT and improve visual field mean deviation values over 12 months.12 However, potential crossover treatment effects and problems with study methodology may have confounded their results. From this study alone, it is difficult to draw firm conclusions on the efficacy of treatment on reducing ONHD progression.
THE VERDICT
At this stage, the evidence supporting ocular hypotensive treatment for individuals with ONHD and associated visual field loss is weak. Considering the potential for ONHD to cause marked symptomatic vision loss, more research in this area is warranted on two fronts. Firstly, it would be valuable to determine the likely rate of visual field progression in ONHD with static automated perimetry as the mainstay in modern clinical practice. Secondly, randomised control trials to determine the efficacy of ocular hypotensive agents on slowing RNFL and visual field progression are needed to determine the potential role of treatment in clinical practice.
Elizabeth Wong, BOptom (Hons), MOptom, GradCertOcTher, FAAO is a Centre For Eye Health (CFEH) senior staff optometrist who has worked in a variety of clinical settings including ophthalmology practice. She has a special interest in glaucoma and collaborative care, and was recently admitted as a Fellow of the American Academy of Optometry.
Janelle Tong, B. Optom (Hons), B. Sci is a clinical and research optometrist at Centre For Eye Health, who has previously worked in a full-scope private practice in Sydney. She is currently involved in research at CFEH, looking into models describing normal agerelated changes to the eye.
References
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- Malmqvist L, Wegener M, Sander BA, Hamann S. Peripapillary Retinal Nerve Fiber Layer Thickness Corresponds to Drusen Location and Extent of Visual Field Defects in Superficial and Buried Optic Disc Drusen. J Neuroophthalmol. 2016;36(1):41-5.
- Gili P, Flores-Rodriguez P, Martin-Rios MD, Carrasco Font C. Anatomical and functional impairment of the nerve fiber layer in patients with optic nerve head drusen. Graefes Arch Clin Exp Ophthalmol. 2013;251(10):2421-8.
- Mustonen E. Pseudopapilloedema with and without verified optic disc drusen. A cclinical analysis II: visual fields. Acta Ophthalmol. 1983;61:1057-66.
- Roh S, Noecker RJ, Schuman JS, Hedges TR, Weiter JJ, Mattox C. Effect of optic nerve head drusen on nerve fiber layer thickness11The authors have no proprietary interest in the development of this or competing instruments. Ophthalmology. 1998;105(5):878-85.
- Lansche RK, Rucker CW. Progression of defects in visual fields produced by hyaline bodies in optic disks. AMA Archives Ophthalmol. 1957;58:115-21.
- Lee AG, Zimmerman MB. The rate of visual field loss in optic nerve head drusen. Am J Ophthalmol. 2005;139(6):1062-6.
- Morris RW, Ellerbrock JM, Hamp AM, Joy JT, Roels P, Davis CN, Jr. Advanced visual field loss secondary to optic nerve head drusen: case report and literature review. Optometry. 2009;80(2):83-100.
- El-Assal K, J. Tatham A, K S. Rapidly Progressing Visual Loss Associated With Optic Nerve Head Drusen: Is There A Role For Lowering Intraocular Pressure? Journal of Ophthalmic Science. 2016;1(2):23-33.
- Grippo TM, Shihadeh WA, Schargus M, Gramer E, Tello C, Liebmann JM, et al. Optic nerve head drusen and visual field loss in normotensive and hypertensive eyes. J Glaucoma. 2008;17:100-4.
- Nolan KW, Lee MS, Jalalizadeh RA, Firl KC, Van Stavern GP, McClelland CM. Optic Nerve Head Drusen: The Relationship Between Intraocular Pressure and Optic Nerve Structure and Function. J Neuroophthalmol. 2018;38(2):147-50.
- Pojda-Wilczek D, Wycislo-Gawron P. The Effect of a Decrease in Intraocular Pressure on Optic Nerve Function in Patients with Optic Nerve Drusen. Ophthalmic Res. 2017:1-6.
