Macula

Macula

The macula is a highly specialized region in the central retina that is responsible for detailed central vision. It plays a crucial role in activities that require high visual acuity, such as reading, driving, facial recognition, and colour perception. At the centre of the macula lies the fovea, the area with the highest density of cone photoreceptors and the greatest visual resolution. Damage to the macula can therefore result in significant impairment of central vision and visual function.Because of its critical importance for visual quality, there is increasing interest in minimizing radiation dose to the macula whenever possible. Accurate delineation of a surrogate macular region may help support organ-sparing treatment strategies and improve the assessment of dose–effect relationships.

For contouring, the left and right macula should be delineated separately.The anatomical macula is an oval-shaped area of the retina measuring approximately 5–6 mm in diameter. It is located about 4 mm temporal and 0.8 mm inferior to the centre of the optic nerve head. The fovea is situated near the centre of the macula and represents the most visually sensitive region of the retina. As the macula itself cannot be reliably distinguished from the surrounding retina on routine CT or MRI scans, a reconstructed surrogate region can be generated.

Anatomical landmarks

• Select the slice passing through both the centre of the lens and the optic nerve.
• Using a 1 mm brush, contour a small region of retina aligned with the centre of the lens and located at least 2 mm lateral to the optic nerve. This reconstructed location represents the fovea.
• Create a 2 mm expansion around this reconstructed foveal location.
• Remove all portions extending into the vitreous body or outside the globe, retaining only the retinal component. This results in a circular retinal region approximately 5 mm in diameter corresponding to the reconstructed macula.

As eye movements can result in displacement of ocular structures by several millimetres, the use of an eye fixation protocol is recommended whenever feasible to improve reproducibility and maximize sparing of the macula during treatment.

The accompanying video demonstrates a step-by-step approach for identifying and contouring the reconstructed macular region using readily identifiable anatomical landmarks. This educational resource is intended to support consistent, accurate, and reproducible delineation for clinical and research applications.

Please site as follows:

Hofstede, D., Di Perri, D., Roelofs, E., Postma, A., Troost, E., & Eekers, D. EPTN International Neurological Contouring Atlas (INCA) instruction videos. CancerData, 2022. doi:10.17195/candat.2022.02.1