Screening for macular disorders: the optometrist's perspective

Abstract

Macular screening services can take many forms, offering a variety of roles for optometrists. The need for screening has been demonstrated in industrialized and developing nations alike. Populations of particular interest for macular screening services include individuals at high risk for diabetes, not just diagnosed diabetics, since a significant proportion of those with diabetes do not realize it. Individuals who know they have diabetes are frequently not examined at the recommended intervals. Related populations include patients with a high likelihood of retinal vascular disease and high blood pressure. A second population is older individuals, who are at risk for age-related macular degeneration and degenerative myopia, key causes of vision loss depending upon geographic location and ethnicity. Images showing the complexity of lesions from diabetic retinopathy, age-related macular degeneration, and degenerative myopia illustrate the challenges of screening and classification. A third population to be screened is the large pediatric one. While many children are at risk for developing myopia, which could lead to high myopia, the risk of myopia and retinal damage is far more common in individuals who had low birth weight or premature birth. A variety of types of screening instrumentation are discussed in terms of practicality of use and cost. The technical challenges in populations with dark eyes, small pupils, and poor anterior-segment media are discussed. We discuss the wealth of screening strategies, from permanent sites with trained staff and expert graders to planned campaigns that target specific populations. Successful screening systems include instrumentation that is used within its limits, feedback and supervision during screening and grading, and clear pathways for referral for a complete examination or treatment.

Cones in ageing and harsh environments: the neural economy hypothesis

“…To understand the impact of potentially delaying an extreme loss of cones, we investigated the prevalence and causes of moderate to severe sight threatening visual impairment in 191 000 000 patients globally. We summarised two literature sources that are inexplicably isolated from each other: vision screening, particularly for diabetic retinopathy, and population‐based epidemiological studies . To foster communication between these segregated fields and call attention to the growing need for eyecare worldwide, we selected a high proportion of references from open access sources.…”

“…Advanced imaging techniques have allowed the documentation of changes to the retina, RPE, and choroid far beyond ophthalmic examination or colour fundus photography, due to the limitations of imaging with visible wavelength light. We document the harsh environment of cones, with NIR imaging 17,41,46 and multi-mode imaging 17,41,45,46,103 : drusen, RPE damage, layer distortions, and fluid within retinal layers.…”

Subtle changes in diabetic retinas localised in 3D using OCT

“…Vessel remodelling occurs in patients with a clinical classification of only mild or moderate non‐proliferative retinopathy . Thus, the early referral of diabetic patients is crucial when treatment or systemic glucose control can still prevent vision loss, by improving the present clinical classifications of DR …”

“…When viewing a digital colour image of the macula, the red and green colour channels can be separated to detect the presence of cystoid structures and hyperreflective foci, which for the outer retina are more visible in the red than in the green channel and are consistent with OCT findings in diabetic patients with DME . Thus, emphasis on damage to the outer blood retinal barrier, including the RPE, in DME may be imperative . Further, the significant impact on sight is related to the structures in deeper layers, including the deeper cysts being related to worse visual acuity, and photoreceptor integrity indicating which eyes had worse visual acuity .…”

“…The initial clinical classification of DR is based on the superficial retina and larger retinal vascular changes that lead to the leakage of fluids and lipids, and including growth of new vessels on the disc or elsewhere in the retina . However, most grading schemes of DR have not yet evolved to use modern improved imaging modalities as most of these grading schemes rely on fundus photography, which originally used flood illumination and lacked scanning techniques as well as a confocal aperture to improve contrast …”