Local and international expert clinicians and researchers presented lectures on topics ranging from contact lenses to neuro-ophthalmologic disorders at the annual SRC. A review provides valuable information that can be immediately put to use in practice.
The Southern Regional Congress (SRC) in May was considered to be one of the most successful ever held by the Optometrists Association of Australia (Victoria). The congress attracted a record number of attending delegates and featured a broad range of lectures and workshops, which have been reviewed below.
New to SRC in 2011, was the introduction of keypads to register session attendance and the option for additional continuing professional development points with the successful completion of interactive assessments.
Controversies in Nutritional Management of AMD
Associate Professor Diana Shechtman, from Nova South-eastern University of Optometry, provided an evidence-based update on the nutritional management of dry age-related macular degeneration (AMD). Citing the landmark investigation conducted by the National Eye Institute in the USA (2001), known as AREDS (Age-Related Eye Disease Study), A/Prof Shechtman described evidence supporting the benefit of dietary supplementation to slow the progression of AMD in at-risk patients.
Dr. Gentle assessed the latest theories and evidence behind the current strategies for attenuating childhood myopic progression
Involving over 4,700 participants aged between 55 and 80 years of age, AREDS demonstrated a 25 per cent reduction in the development of advanced AMD within a sub-population of patients treated with anti-oxidant/zinc supplementation.1
The benefit of nutritional supplementation in reducing AMD progression was evident in patients with intermediate AMD, defined clinically as: extensive (>15) intermediate-sized drusen (individual size: 63-124um), at least one large druse (>125 um, or approximately the width of the central retinal vein when exiting the optic nerve) or non-central geographic atrophy in one or both eyes. The original AREDS formulation consisted of a high-dose combination of Vitamin C (500mg), Vitamin E (400 IU), zinc (80mg), copper (2mg) and beta-carotene (15mG).
Beta-carotene has since been removed due to its reported association with lung carcinogenesis in patients with history of smoking within the past five years.2,3
Associate Professor Schechtman indicated that it was reasonable to suggest ‘anti-oxidant plus zinc’ supplements in suitable patients that present with the described clinical signs of AMD. However, caution was advised in patients concurrently taking Warfarin due to the potential interaction with Vitamin E which may potentiate abnormal bleeding.4
Side-effects associated with zinc supplementation have also been reported, including a potential link to Alzheimer’s disease 5, an increased risk of genito-urinary complications6 and reduced absorption of systemic tetracycline medications. A follow-up study, AREDS-2, is currently underway to assess the potential benefits of oral supplementation with macular carotenoids (lutein, 10mg and zeaxanthin, 2mg), and/or omega-3 long-chain polyunsaturated fatty acids (DHA and EPA, 1000mg) on the progression to advanced AMD.
Advances in Glaucoma Therapy
International keynote speaker Professor Bruce Onofrey from the University of Houston provided an engaging lecture on the latest perspectives relating to the therapeutic management of glaucoma. A major focus of the presentation was to emphasise the importance of using the most recent large-scale clinical studies as a foundation for guiding management decisions, in order to provide the highest standards of care to patients.
The presentation began with a summary of the findings from the Ocular Hypertension Treatment Study (OHTS, 2002), a large randomised trial that examined whether reducing intra-ocular pressure (IOP) was effective in delaying or preventing the onset of glaucoma and subsequent vision loss in patients who were at risk of developing the condition.
Individuals with both normal visual fields and optic nerve appearance, in association with a baseline IOP between 24 and 32 mmHg in at least one eye, were randomised to either receive topical anti-hypertensive treatment (n = 817) or to be observed without treatment (n = 819) over a minimum period of five years. It was found that treating ocular hypertensive patients with topical anti-glaucoma medication reduced the overall risk of these patients developing primary open angle glaucoma from 9.5 per cent to 4.4 per cent.7
In a companion paper 8, the authors also reported that the baseline factors associated with a higher risk of glaucomatous optic neuropathy were older age, larger horizontal and vertical cup-to-disc ratios, greater Humphrey visual field pattern standard deviation, higher intra-ocular pressure, African-American race and a thinner cornea.
Of these, reduced central corneal thickness was identified as the most significant baseline predictive factor for conversion to glaucoma. Patients with a corneal thickness of 555um or less were found to have a three-fold greater risk of developing primary open angle glaucoma after five years, compared with participants whose corneal thickness was greater than 588um. Professor Onofrey indicated that by considering these factors, practitioners could identify ocular hypertensive patients that were at moderate to high risk of developing glaucoma and who were therefore more likely to benefit from early therapeutic intervention.
Professor Onofrey also discussed the scientific evidence relating to the benefit of IOP reduction for reducing glaucomatous progression in patients with established disease. The Early Manifest Glaucoma Trial (EMGT, 2002) was a landmark investigation that definitively demonstrated that topical treatment with ocular hypotensives significantly delayed glaucomatous progression in both primary open angle – and normal tension – glaucoma.9
The magnitude of the initial IOP reduction was determined to be important, with each higher (or lower) unit mmHg of IOP at three-month follow up, being associated with a 10 per cent greater (or lower) risk of progression. Factors established to increase the risk of progressive glaucoma included: higher initial IOP, disc haemorrhage, pseudoexfoliation and bilateral disease.
Further supporting evidence for the importance of controlling IOP derived from the Advanced Glaucoma Intervention Study (AGIS), which showed that lower IOP was associated with reduced progression of visual deficits. Specifically, eyes with IOP less than 18 mmHg at all visits over the six year evaluation period, demonstrated virtually no change to the status of their visual field.10 A minimum 30 per cent reduction in IOP was found to be necessary to minimise the risk of developing further optic nerve damage.10
The lecture concluded with a discussion relating population studies that have demonstrated a link between low ocular perfusion pressure and glaucoma progression.11,12
Professor Onofrey recommended that practitioners consider the effect of different classes of IOP-lowering medications on systemic blood pressure in order to minimise the likelihood for low nocturnal ocular perfusion pressure.
The Future of Myopia Control
A lecture on one of the current hottest topics in optometry, ‘myopia control’ was presented by the Australian keynote speaker, Dr. Alex Gentle from The University of Melbourne. Using the clinical scenario of a young, progressive myope who attends seeking appropriate optometric management, Dr. Gentle assessed the latest theories and evidence behind the current strategies for attenuating childhood myopic progression.
Numerous clinical approaches have been postulated to potentially retard paediatric myopic progression, with some modalities now demonstrating more promise than others. Spectacle-based interventions including progressive-addition lenses (PALs), bifocal lenses, myopic under-correction, prism-corrected spectacles and aberration-controlled lenses were described. Citing multiple treatment trials, Dr. Gentle reported that current research
evidence indicates that treatment effects with spectacle lens modalities are overall relatively small. Of these strategies, a clinically-significant myopia control effect has only been demonstrated with PALs for myopic children with abnormal accommodation/vergence profiles.13
The potential role for contact lenses in myopia stabilisation was also explored. It was reported that both spherical soft14 and rigid15 contact lenses have been shown to have no significant effect on inhibiting myopic progression.
Overnight orthokeratology was discussed in the context of eliminating manifest myopia, with Dr. Gentle suggesting that further studies are still required to validate claims of its ability to also control axial elongation. Recent investigations conducted in Australia into dual-focus soft contact lenses (consisting of a distance centre and concentric near zone) were also reported to be promising, with a demonstrated 37 per cent reduction in myopic progression over ten-months, compared with standard single-vision contact lenses.16
Pharmacological interventions represent a further method of myopia control. A number of recent studies have demonstrated the efficacy of the topical muscarinic-receptor antagonists, atropine and pirenzipine, in slowing myopia progression by at least 40 per cent in most children.17-19
However, despite their positive treatment effects for retarding myopic refractive error, use of these agents for myopia control is cautioned due to their significant adverse ocular effects and the potential for withdrawal to lead to subsequent increased rates of myopia progression.20 Dr. Gentle concluded by emphasising that there is not ‘one path’ to myopia control; more research is required to elucidate the aetiology and pathogenesis of myopia and to fully understand the mechanisms underlying the observed effects of myopia control.
The Latest on Contact Lenses
Contact lenses were another important focus of the SRC continuing professional development program. Industry-sponsored forums and symposiums facilitated discussion relating to the future of contact lens care systems and a dynamic panel of local and international optometrists presented on the topic of toric and multifocal soft lens technology.
An interesting presentation delivered by Maria Markoulli, from the University of New South Wales, provided insights into the therapeutic application of contact lenses for the management of anterior segment disease and post-surgical complications.
Almost three-quarters of optometrists are reported to prescribe therapeutic contact lenses,21 with the most common indications including recurrent corneal erosions, bullous keratopathy, neurotrophic keratitis and corneal abrasions. The aim of treatment is to provide protection to the cornea during healing and to relieve pain during re-epithelialisation. The standard treatment protocol with a therapeutic contact lens is recognised to involve concomitant therapeutics, typically consisting of topical prophylactic broad-spectrum antibiotics 22 and a low-potency topical steroid to reduce inflammation.23 Miss Markoulli also discussed the promising future for therapeutic contact lenses for the delivery of ocular therapeutic agents used in the management of chronic ocular conditions such as glaucoma, inflammation and infection.
New research into the efficacy of silver-impregnated anti-bacterial contact lens storage cases in limiting microbial contamination was presented by Miss Jaya Dantam, from the Brien Holden Vision Institute. Microbial contamination of lens storage cases has been shown to be in the order of 53-83 per cent of cases, with about four in every five of microorganisms identified as potential pathogens.
In an attempt to minimise microbial contamination, anti-bacterial contact lenses cases impregnated with silver (a broad spectrum anti-microbial) have been commercially developed. Miss Dantam’s data indicate that compared with standard cases, silver-impregnation significantly reduces the recovery of fungii, gram-negative bacteria and gram-positive bacilli from lens storage cases. It was hypothesised that a reduced microbial loading in contact lens cases may limit the occurrence of contact lens-storage case related adverse responses.
The next Southern Regional Congress will be held in May 2012 and promises to again deliver an exciting, varied and high quality optometric education program.
Dr. Laura Downie, BOptom, PhD(Melb), PGCertOcTher, DipMus(Prac), AMusA is an optometrist who specialises in contact lenses. She has been published in scientific journals and is a clinical instructor to undergraduate optometry students.
References
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A randomised, placebo-controlled, clinical trial of high-dose supplementation with vitamins C and E, beta-carotene and zinc for age-related macular degeneration and vision loss: AREDS report no. 8. Arch Ophthalmol 2001; Oct 119(10):1417-1436.
2. Omenn GS, Goodman GE, Thornquist MD, Balmes J, Cullen MR, Glass A, Keogh JP, Meyskens FL, Valanis B, Williams JH, Barnhart S, Hammar S. Effects of combination of beta carotene and vitamin A on lung cancer and cardiovascular disease. N Engl J Med 1996; May 234(18):1150-1155.
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