A record number of optometrists attended the National Australasian College of Behavioural Optometrists Conference (NACBO) at Darling Harbour, Sydney in July, where the emphasis was on evidence based learning.
ACBO’s annual national conference, which ran in the lead up to the Optical Distributors and Manufacturers Australia (ODMA) Fair, provided 150 delegates with the latest evidence based practice on myopia, hyperopia, convergence insufficiency, strabismus, amblyopia, pattern glare, intermittent exotropia, accommodation insufficiency, and learning-related vision problems.
The conference commenced with a presentation by Professor Padmaja Sankaridurg from Brien Holden Vision Institute, who delivered the inaugural Brien Holden address, on the vast and increasingly important topic of myopia. The prevalence of myopia is expected to be 50 per cent, and high myopia 10 per cent, of the global population in 2050, with the prevalence expected to be evenly distributed between younger and older people. Faced with earlier onset of myopia with a population that is living longer, the consequences of this eye condition are significant for individuals, their family and the global community.
Prof. Sankaridurg spoke about the environmental and genetic risk factors of myopia, pointing out that children who have parents with myopia are at increased risk. However, she said it appeared to be environmental factors that played the dominant role in determining the risk of myopia. She said there was a clear difference between the prevalence of myopia between rural and urban areas with people living in urban areas significantly more likely to develop the condition. An association exists between the amount of time spent outdoors and the incidence of myopia, although the specific reason for this is yet to be determined. Additionally, she said research had found myopia progresses less in summer months compared to winter. Interestingly, while spending time outdoors lowered the risk of developing myopia, for those children who already had myopic, spending time outdoors did not alter its rate of progression.
eye care providers have to integrate their clinical experience with the best available evidence to make decisions about the care of the individual child
In terms of progression, younger children progress more quickly than older children and myopia progresses significantly faster amongst Asian than Caucasian children.
Professor Sankaridurg said controlling myopia, particularly in its earliest stages, was important because it could significantly reduce progression to high myopia and myopic macular degeneration, for which the consequence is vision impairment or blindness.
She went on to describe three strategies to control myopia: environmental, pharmaceutical and optical. Atropine was the most successful pharmaceutical strategy for myopia control although at one per cent, there were often significant side effects (photophobia, poor near visual acuity and allergic reactions) and 12 per cent of patients were non-responders. Prof. Sankaridurg said studies were analysing the value of administering 0.1 per cent atropine and although this seemed to help control myopia, it did not reduce axial length. An alternative pharmaceutical treatment may be methylxanthine though this is not currently commercially available.
In terms of optical strategies to control myopia, Prof. Sankaridurg said executive bifocal spectacle lenses had been shown to slow progression of myopia by 50 per cent compared to single vision lenses, possibly by either reducing accommodative dysfunction or reducing peripheral retinal defocus.
She said soft multi-focal contact lenses successfully reduce the rate of myopic progression by reducing peripheral retinal focus or inducing myopic defocus and shown in multiple trials to reduce progression by over 30 per cent. Orthokeratology, which flattens the cornea profile, resulting in peripheral defocus control, have been shown to significantly change the axial length and slow myopia control by 30 – 40 per cent.
Prof. Sankaridurg spoke about the extended depth of focus contact lens developed at Brien Holden Vision Institute and extensively researched. She said it had been demonstrated that this successfully controls the direction of growth of the retina to slow myopic progression and, being a single vision lens, provided better vision when compared with multifocal contact lenses.
Prof. Sankaridurg went on to advise optometrists to create risk profiles they could refer to during consults, that would provide an efficient guide to a patient’s likelihood of developing myopia or for their myopia progressing.
As keynote speaker at NACBO 2017, America’s Professor Susan Cotter delivered most of the presentations at the conference. With a strong focus on evidence-based research, including a session on what constitutes a sound randomised clinical trial, Prof. Cotter emphasised the value of vision therapy in eliminating symptoms in children with convergence insufficiency (CI). She presented data from randomised clinical trials, demonstrating that office-based vergence-accommodative therapy has been found to be considerably more effective than either pencil-push up treatment or home-based computer therapy in improving symptoms and clinical signs of symptomatic convergence insufficiency in children. Nearly 90 per cent of children whose symptomatic CI was successfully treated with office-based vision therapy remained either successful or improved one-year post-treatment. Prof. Cotter noted that the Convergence Insufficiency Symptom Survey (CISS) could be used to quantify symptoms in patients with CI; however, a high score was not diagnostic for CI.
Prescribing for Hyperopia in Early Childhood
Prof. Cotter stressed that the magnitude of hyperopia should not be the sole determinant when assessing the need to prescribe vision correction for young children with hyperopia. She noted that it was important to look at a multitude of factors – including patient age, symptoms, family history, academic performance, other clinical findings, and whether the magnitude of hyperopia is a known risk factor for the development of amblyopia or strabismus. Prof. Cotter provided data from a large population-based study of children, six to 72 months of age, that found a greater than six-fold increase in the risk of esotropia at levels of hyperopia as low as 2.00 D – 3.00 D. She then pointed out that it is not known, however, if prescribing prophylactically for hyperopia will decrease the incidence of developing esotropia.
Prof. Cotter said in terms of clinical findings, she pays particular attention to the child’s eye alignment, near stereoacuity, near visual acuity, and accommodative accuracy. She emphasised that a high lag of accommodation on dynamic retinoscopy would indicate the child was not focusing accurately and suggest the child would benefit from a hyperopic prescription. Prof. Cotter said there was no need to prescribe the full hyperopic correction for non-esotropic children, and that she typically cuts the plus symmetrically by an amount that would be considered normal for their age. “Leave them uncorrected by an amount of hyperopia that you consider negligible for their age, which is often in the range of 1.00 or 2.00D. First, there is no reason to prescribe full plus in the absence of esotropia, and second, cutting plus will likely allow for any emmetropisation to occur in cases where the emmetropisation process might still be active.”
She said practitioners often worry about prescribing for hyperopia in preschool children because they don’t want to disrupt the emmetropisation process. “I don’t worry that much about disrupting emmetropisation in four and five-year olds because most of the emmetropisation process is over by then,” she noted after presenting data from a longitudinal study of more than 200 three-month old infants who received serial cycloplegic refractions. The study found most of the emmetropisation action took place in the first 18 months of life and there was not much change after that. She also presented study results that showed prescribing a partial hyperopic prescription to infants with 3.00 to 6.00 D of hyperopia did not disrupt the emmetropisation process.
Prof. Cotter presented results from recent studies that found moderate amounts of uncorrected hyperopia were associated with reductions in visual function including visual acuity, stereoacuity, and accommodative response, as well as worse performance on tests of early literacy and visual motor integration. “The information coming out tells us we need to pay particular attention to moderately hyperopic preschool children and consider prescribing partial prescriptions for them, particularly if there is any indication that they are struggling academically.”
Citing an anecdotal case, she recalled a young girl with a moderate amount of uncorrected hyperopia who had been unsettled in the classroom. She prescribed glasses and soon after received a call from the girl’s teacher who said her behaviour had completely turned around – whereas she had been constantly unsettled in the classroom, she had become focussed and was a model child. Prof. Cotter said in cases like these, prescribing glasses could make a significant difference to a child’s behaviour and ability to learn, and ultimately to their academic performance and eventual career path. However, she emphasised that, at present, there are no evidence-based prescribing guidelines for hyperopia in young children, which can sometimes make it a bit tricky to decide if a hyperopic correction should be prescribed. She reiterated that eye care providers have to integrate their clinical experience with the best available evidence to make decisions about the care of the individual child.
In a presentation on amblyopia, Prof. Cotter said there is now a strong evidence base for treating this condition and because there is no known age cut-off in terms of visual plasticity for the recovery of visual acuity in amblyopic eyes, amblyopia treatment should not be withheld from school-age children and teenagers.
She noted that a cycloplegic refraction (two drops of one per cent cyclopentolate usually) should be completed when assessing an amblyopic child for the first time. She also provided prescribing guidelines that are based on cycloplegic refraction findings.
Prof. Cotter said the optical correction of refractive error alone has a true treatment effect beyond the immediate visual acuity gains from simply eliminating optical blur. In fact, for patients with no prior treatment (including refractive correction), there is a mean improvement of three lines in amblyopic eye visual acuity, occurring for both moderate and severe amblyopia. This optical treatment effect not only happens in young children, but also can occur in older children and adults. Prof. Cotter noted that eye care providers can prescribe the appropriate optical correction as the initial sole treatment for amblyopia and then follow the patient at six to eight week intervals to monitor for improvements in visual acuity. If amblyopia is still present once visual acuity stabilises, then part-time patching or atropine can be prescribed. In cases where the visual acuity improves from continued wear of the optical correction, the overall treatment burden will be less – she noted, “it is a lot easier to wear a patch when one has visual acuity of 20/50 rather than 20/100”. She also noted that residual amblyopia after conventional amblyopia treatment has been reported to be between 30 to 50 per cent, and this is one of the current amblyopia treatment conundrums.
Prof. Cotter said there is a recently published body of literature to support the concept that in amblyopia there is a structurally intact binocular visual system that is rendered functionally monocular by suppression, and that binocular fusion and increased visual acuity can occur if interocular stimulation is re-balanced. She said there are numerous studies that are currently evaluating this treatment hypothesis.
Sydney, Australia will be home to the 8th International Congress of Behavioural Optometry, themed Establishing The Future, from 26 –29 April 2018. Visit www.icbo.events