Iris freckles: Potential biomarker for AMD

(image Credit: AdobeStock/starush)

Hakan Koc, MD, and Seda Uzunoğlu, MD, reported that iris details should not be ignored when screening for age-related macular degeneration (AMD).¹ They are from the Faculty of Medicine, Department of Ophthalmology, Giresun University, Giresun, Turkey.

Koc and Uzunoğlu enumerated the risk factors for AMD: aging, smoking, long periods of exposure to sunlight, increased body mass index, alcohol consumption, hypertension, previous cataract surgery, lipid profile disorder, genetic factors, and oxidative stress.² Visible light and ultraviolet (UV), they explained, are considered risk factors for AMD.³ A meta-analysis reported that the risk of AMD increased significantly in individuals exposed to higher levels of sunlight.⁴ A large study also found that exposure to UV radiation increased the risk of AMD.⁵

Iris freckles are the most common melanocytic iris lesions, and UV sunlight is a well-known promoter of melanogenesis. Eyes are exposed to light most of the time, and therefore sunlight also affects the iris.^6-8 Another study reported a higher rate of iris freckles in patients with UV-associated skin cancer.⁹

The investigators conducted a case-control study to determine if there was an association between AMD and iris freckles. They used a mobile phone camera to obtain iris photographs of 300 eyes of 300 patients with AMD and 300 eyes of 300 healthy volunteers. The photographs were classified according to the Descriptive Iris Color Classification Scale.¹⁰

The average ages of the AMD and control groups did not differ significantly 73.05 ± 6.93 and 73.43 ± 5.72, respectively.

In the AMD group, freckles were seen in 200 (66.7%) and not in 100 patients (33.3%). In the control group, freckles were present in 142 (47.3%) of the patients in the control group and not in 158 controls (52.7%). “There was a significant difference in the presence of freckles between the 2 groups (P < 0.001). The average number of freckles in the AMD group was 3.97 ± 3.07, and the number of freckles in the control group was 3.06 ± 2.55 (P = 0.001),” the authors reported.

They concluded, “We think that evaluation of iris details, especially the presence of iris freckles, should be used routinely in AMD screening. The risk of AMD can be predicted by evaluating iris details, which is an easy and inexpensive method. The presence of iris freckles can be used as a potential biomarker for AMD. Therefore, we strongly support routine assessment of iris details, particularly the presence of iris freckles, in screening for AMD.”

References

1. Koc H, Uzunoğlu S. A potential biomarker for age-related macular degeneration disease: iris freckles. Int J Retin Vitr. 2024;10:62 (2024). https://doi.org/10.1186/s40942-024-00575-z

2. Ferris FL, Fine SL, Hyman L. Age-related macular degeneration and blindness due to neovascular maculopathy. Arch Ophthalmol.1984;102:1640–1642.

3. Schick T, Ersoy L, Lechanteur YT, et al. History of sunlight exposure is a risk factor for age-related macular degeneration. Retina. 2016;36:787–90.

4. Sui GY, Liu GC, Liu GY, et al. Is sunlight exposure a risk factor for age-related macular degeneration? A systematic review and meta-analysis. Br J Ophthalmol. 2013;97:389–394.

5. Qu Y, Jiang Y, Zhang G, et al. Association of exposure to ultraviolet radiation and warm-season ozone air pollution with incident age-related macular degeneration: a nationwide cohort study in China. Sci Total Environ. 2024;938:173580.

6. Eagle RC. Iris pigmentation and pigmented lesions: an ultrastructural study. Trans Am Ophthalmol Soc. 1988;86:581–687.

7. Shields JA, Shields CL. Intraocular tumors: an atlas and textbook. 2008;Philadelphia: Wolters Kluwer.

8. Shields CL, Kancherla S, Patel J, et al. Clinical survey of 3680 iris tumors based on patient age at presentation. Ophthalmology. 2012;119:407–414.

9. Grigore M, Furtunescu F, Minca D, Costache M, Garbe C, Simionescu O. The iris signal: blue periphery, tan collaret and freckles pattern strong indicators for epidermal skin cancer in South-Eastern Europe. J Eur Acad Dermatol Venereol. 2018;32:1662–1667.

10. Simionescu O, Grigore M, Furtunescu F, Minca D, Chitu V, Costache M. A novel iris colour classification scale. Ann Res Rev Biol. 2014;4:2525–2534.