The optometrist’s role in managing age-related macular degeneration with OCT-A

OCT's ability to detect early vascular changes, differentiate between AMD subtypes, and guide treatment decisions makes it an essential tool for optometrists.

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Age-related macular degeneration (AMD) remains a significant cause of vision loss among older adults and is on the rise.¹ Early detection and management of AMD are crucial to preserving visual function. Optical coherence tomography angiography (OCT-A) has emerged as a noninvasive, high-resolution imaging modality that provides detailed visualization of the retinal and choroidal vasculature. This technology offers a new dimension in AMD assessment and monitoring. This article explores the role of OCT-A in AMD detection, classification, and treatment guidance.

OCT-A detects blood flow within retinal and choroidal vessels without requiring dye injection, as with fluorescein angiography (FA) or indocyanine green angiography (ICGA). By analyzing motion contrast from repeated scans, OCT-A generates detailed vascular maps of different retinal layers, making it particularly useful for detecting choriocapillaris abnormalities and neovascularization in patients with AMD.²

Identifying early AMD changes

OCT-A provides insights into microvascular alterations before the development of clinically significant structural changes, often before visual acuity is affected.³ It can detect early choriocapillaris flow deficits, which predict AMD progression.⁴ The flow deficits may worsen even while staging remains the same.⁵ Key findings in early AMD include reduced choriocapillaris density and perfusion, indicative of impaired blood flow. Additionally, increased flow voids are observed, signaling ischemic stress in the retinal tissue. Subclinical nonexudative choroidal neovascularization (CNV) may also be present, which can precede the development of wet AMD.

Differentiating between dry and wet AMD

OCT-A can uniquely distinguish between dry and wet AMD, guiding clinical decision-making. Dry AMD is characterized by progressive changes to the choriocapillaris, leading to photoreceptor and retinal pigment epithelium (RPE) dysfunction. Wet AMD is defined by the presence of CNV, which appears as a tangled vascular network within the outer retina or sub-RPE space. OCT-A allows early detection of CNV even before fluid accumulation occurs.

Identifying nonexudative CNV

Figure. This image shows a neovascular net in the choriocapillaris. This patient was monitored for 2 years before anti-VEGF injections were needed. (Image courtesy of Michael Cymbor, OD, FAAO.)

Identifying nonexudative CNV is important as it represents a subtype of neovascularization that lacks detectable leakage on traditional FA (Figure). OCT-A plays a key role in the early detection of CNV before vision-threatening exudation occurs. It also helps monitor CNV growth patterns, which can assess the risk of conversion to active exudative AMD. Additionally, OCT-A aids in establishing more precise treatment timelines for initiating anti-VEGF therapy.

Monitoring treatment response to anti-VEGF therapy

OCT-A is valuable in assessing the effectiveness of intravitreal anti-VEGF injections by tracking the regression or persistence of CNV. It also helps evaluate vascular remodeling that occurs following treatment. Additionally, OCT-A can detect recurrent neovascularization before fluid reaccumulation becomes clinically evident, allowing for earlier intervention.

OCT-A in geographic atrophy evaluation

OCT-A is key in evaluating geographic atrophy (GA), the advanced form of dry AMD associated with progressive RPE and photoreceptor loss. OCT-A helps identify choriocapillaris flow loss that precedes GA expansion, differentiate between non-neovascular and neovascular atrophy, and predict GA progression by analyzing vascular integrity at the lesion margins.

Advantages of OCT-A over traditional imaging modalities

OCT-A offers several advantages compared with traditional imaging modalities like FA and ICGA. It is noninvasive as it does not require dye injection, reducing patient risk and discomfort. OCT-A also has a significantly shorter acquisition time than FA or ICGA, and its layer-by-layer visualization allows precise localization of vascular pathology.

Challenges and limitations of OCT-A

However, OCT-A does pose some challenges and limitations. Motion artifacts caused by patient movement can affect image quality. Also, it is more susceptible to reduced scan quality from tear film insufficiency and cataracts. OCT-A is meant to complement and not replace standard OCT. Additionally, due to a learning curve, interpreting OCT-A images requires significant experience and expertise.

Conclusion

OCT-A has improved AMD management by providing new insights into retinal and choroidal vasculature. Its ability to detect early vascular changes, differentiate between AMD subtypes, and guide treatment decisions makes it an essential tool for optometrists. By integrating OCT-A into clinical practice, optometrists can enhance early diagnosis, improve monitoring precision, and contribute to better visual outcomes for patients with AMD.

References

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3. de Oliveira Dias JR, Zhang Q, Garcia JMB, et al. Natural history of subclinical neovascularization in nonexudative age-related macular degeneration using swept-source OCT angiography. Ophthalmology. 2018;125(2):255-266. doi:10.1016/j.ophtha.2017.08.030
4. Borrelli E, Savastano MC, De Vitis L, et al. Choriocapillaris flow deficits in early and intermediate age-related macular degeneration: a longitudinal study using OCT angiography. Eye. 2020;34(5):1019-1026. doi:10.1038/s41433-020-01298-9
5. Tiosano L, Corradetti G, Sadda SR. Progression of choriocapillaris flow deficits in clinically stable intermediate age-related macular degeneration. Eye (Lond). 2021;35(11):2991-2998. doi:10.1038/s41433-020-01298-9