I have long thought that the management of amblyopia could be better. Whether caused by ametropia, strabismus or deprivation, the loss of vision caused by amblyopia is still measured by subjective acuity scoring and managed primarily by occlusion. This approach has changed little, to my mind, since my mother’s ‘lazy eye’ was referred to the old Birmingham and Midland Eye Hospital (now an Hotel du Vin in the middle of town).
So, any new developments are always of interest and the many advances in electronic instrumentation are finally having some impact in both the early detection and treatment of amblyopia.
Detection
Autorefraction, carried out binocularly either with or without cycloplegia, has now been accepted and endorsed by the American Academy of Pediatrics as a valid vision screening method. Instruments such as the PlusOptix (from Carleton, figure 1) and the Spot Vision Screener (Welch Allyn, figure 2, below) offer rapid, accurate and, importantly, binocular refraction while digital capture also helps to detect even a small deviation from forward fixation.
The Spot Vision Screener was used successfully in a recent large scale trial in the US.1 Over 1,000 children were screened and those considered at risk of amblyopia referred with a success rate of 95%. The study concludes that ‘the overall predictive ability of the Spot is good, with a sensitivity of 0.88 and a specificity of 0.78. We recommend specific device refractive referral criteria to maximise screening effectiveness.’ Surely, there is no excuse for a universal early age screening programme in the UK using such instrumentation, especially considering the ease with which accurate data can be obtained with minimal training.
Management
There have been encouraging developments in recent years in the way amblyopia is treated. Though, ultimately, the aim is still to improve vision in the amblyopic eye by increasing the stimulus bias to that eye, the way this is done has finally evolved from simply applying a patch to the stronger eye for periods of time.
One novel approach to split the input to each eye is to use a dichroic display screen whereby there is subtly different input to each eye via worn visors. A major advantage of electronic displays is the improved compliance from younger patients required to undertake set periods of detailed viewing. This technique has been refined to a point whereby the input distribution can be altered to match the level of amblyopia. Other methods include the use of electronically controlled filters on spectacles, which can have the transmittance before the better sighted eye controlled or programmed from a remote location at set times.
One recent study has looked at the use of the RevitalVision treatment (figure 3, right).2 This technique allows a personalised target digital display for each individual to be viewed over set periods of time. Repetitive performance of these interactive visual perception tasks (VPTs) results in increased neural response and enhances the neural interactions in the visual cortex, leading to an improvement in visual function. In this latest study, researchers found ‘RevitalVision treatment improves best corrected visual acuity in amblyopic subjects not responding to part-time occlusion therapy.’
Also, because of good compliance and excellent repeatability, the study suggests that such software might now be considered as a viable alternative to traditional occlusion therapy (figure 4, left).
References
- Peterseim MMW et al. Effectiveness of the Spot Vision Screener using updated 2021 AAPOS guidelines. Journal of American Association for Pediatric Ophthalmology and Strabismus, 2023 Jan 13:S1091-8531(23)00008-3
- Magdalene D et al. Neural Vision Perceptual Learning as an Effective Treatment of amblyopia. Vision Development & Rehabilitation, Dec 2022, vol 8, issue 4, pp260-269