Choroidal nevus

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Choroidal Nevus
Other namesEye nevus, Eye freckle
Clipping 3.jpg
Picture of Choroidal nevus
Specialty Ophthalmology
CausesUnknown

Choroidal nevus (plural: nevi) is a type of eye neoplasm that is classified under choroidal tumors as a type of benign (non-cancerous) melanocytic tumor. [1] A choroidal nevus can be described as an unambiguous pigmented blue or green-gray choroidal lesion, found at the front of the eye, around the iris, [2] or the rear end of the eye. [3] [4]

Contents

Nevi are usually darkly pigmented tumors because they comprise melanocytes. Dr. Gass, one of the leading specialists on eye diseases, speculates that a choroidal nevus grows from small cells resting as hyperplastic lesions, and exhibits growth primarily. [5] In most cases, choroidal nevus is an asymptomatic disease, however, in serious conditions, adverse symptoms can be observed.

Choroidal nevus is usually diagnosed through an ophthalmic eye examination, or more specialized technologies such as photographic imaging, ophthalmoscopy, ultrasonography and ocular coherence tomography (OCT). Choroidal nevi can transform into a choroidal or ocular melanoma, becoming cancerous. Therefore, it is crucial to differentiate between a non-cancerous choroidal nevus and lethal melanoma.

Prevalence

The prevalence of choroidal nevus among the United States adult population above 40 years old is 4.7%. [4] In terms of ethnicity, a cohort study done in the United States reported that the prevalence of choroidal nevus was found more in whites (4.1%) than in Chinese (0.4%), blacks (0.7%) and Hispanics (1.2%). However, the difference between Chinese, blacks and Hispanics was not statistically significant. The prevalence of choroidal nevus did not vary between sex, but it did vary with age. The incidence of nevi was discovered to be highest in people between the ages of 55 to 74 and lowest in people aged between 75 and 84. [6] Hence, it is likely that there is a higher prevalence of the disease in people who are comparatively younger.

Another study on the prevalence of choroidal nevus among the female population investigated the role of obesity and reproductive factors in the development of the disease. Among premenopausal women, the risk of developing nevus is shown to be four times higher in those who had their first child before 25, compared to those who had their first child after 35. Moreover, among postmenopausal females, the prevalence in obese females was twice that of non-obese females. [7]

Signs and symptoms

A nevus in the Iris (the small black dot) Blue eye featuring a Nevus in the Iris.jpg
A nevus in the Iris (the small black dot)

Location of the nevi plays a role in determining whether the disease is associated with any symptoms. In unusual circumstances, when the nevus is located below the center of the retina, blurred vision [8] is the result. When a choroidal nevus becomes severe, it can cause leakage of fluid and abnormal development of vascular tissue [9] (neovascularization [10] ). This leads to retinal detachment in that part of the eye, which is observed as some loss of vision or flashing lights. [9] Additionally, if the nevus is present for an extended period of time (years), and hinders the removal of retinal waste products, this can result in the development of yellowish white specks and spots on the surface of the nevi, [9] called drusen.

Cause

Currently, the cause of choroidal nevus is unknown.

Forms of choroidal nevi

There are different ways to describe a choroidal nevus with its specific characteristics, such as halo choroidal nevus, giant choroidal nevus, and choroidal nevus with drusen. It is important to note that these characteristics and forms of nevi can and may overlap and be present at the same time.

Halo choroidal nevus

Halo choroidal nevus is described as a yellow halo around the darkly pigmented brown centre, or in other terms, a pigmented centre with a hypo-pigmented periphery. Halo nevi contribute to 5% of all choroidal nevi. [11] The pathogenesis of the halo nevus is not known, [1] but the presence of a halo around the choroidal nevus was statistically proven to have a relatively lower risk of transforming into melanoma and thus is a predictive factor for stability. [12] [11] A few indicators of a halo nevus include an absence of subretinal fluid and orange pigment, thickness level less than 2 mm, as well as the tumor margin being remote from the optic disk. [1]

Giant choroidal nevus

Typical Drusen Macular Soft Drusen.jpg
Typical Drusen

Giant choroidal nevus is described as one that has a basal diameter larger than 10mm. This variant contributes to 8% of all choroidal nevi. [13] Due to its large basal diameter and thickness, it can be easily mistaken and diagnosed as choroidal melanoma. [13] However, it does have the potential to grow into a melanoma. One study reported that over a period of 10 years, 18% of giant nevi grew into melanomas. [13] Some of the most common features observed among these transformed giant nevi are nearness to the foveola and ultrasonographic acoustic hollowness, [13] suggesting that these may be the reasons for the transformation into melanomas. Thus, patients with giant nevus require close monitoring.

Choroidal nevus with drusen

Choroidal nevus with drusen can be considered as a sign of chronicity since drusen take years to develop and appear. [14] Drusen are composed of lipids and can actually be an indicator that a tumour is a benign nevus as opposed to a cancerous melanoma. [15] In nevi imaged by OCT, about 41% are found to have drusen. [16]

Transformation of a nevus into melanoma

Mnemonic to help differentiate between melanomas and nevi Mnemonic to Help Differentiate Between Melanomas and Nevi.png
Mnemonic to help differentiate between melanomas and nevi

Naturally, nevi occur more frequently than melanoma. [17] Research shows that only about 1 in 9000 (in the United States population) [8] transform into melanomas. Patients are at particularly high risk if the following is observed:

If three or more of the above melanoma risk factors are observed, the risk of the choroidal nevus growing into a melanoma is greater than 50%. [12]

Pathophysiology and cytogenetics

The pathophysiology of choroidal melanoma (a type of uveal melanoma), is not well understood. [20] However, several molecular mechanisms and cytogenetics may be involved in the process of it becoming malignant. Chromosomal alterations, monosomy 3 and chromosome 8 gains have been identified to be associated with metastasis in uveal melanomas. [1] [21] Moreover BAP1, GNAQ, GNA11, SF3B1 and EIF1AX gene alterations were shown to be in correlation with uveal melanomas, each with a frequency of 18–45%. [21]

Other risk factors

Although transformation into a melanoma is considered to be sporadic, [20] several general risk factors are identified to be potentially relevant to the malignant transformation. These include light iris color, generally lower levels of melanin (light and untanned skin tones), exposure to arc welding due to intermittent ultraviolet exposure, [22] [23] as well as diseases such as ocular melanocytosis and dysplastic nevus syndrome. [23]

Differentiating between choroidal nevi and melanomas

Choroidal nevus has a few features that differentiate it from a choroidal melanoma, its malignant tumor form. Speed of growth: Nevi with slow growth in terms of size and in the absence of melanoma risk factors, do not show any signs of malignancy. The process of enlargement of the nevus can take up to an average of 15 years. [24] In a long-term follow up study on the growth of choroidal nevi, out of 284 nevi, 31% of the patients only showed slight enlargement of choroidal nevi without any clinical evidence or signs of transformation into melanoma. [24] In contrast, for small melanomas, the speed of growth is much faster, [13] [24] making it easily detectable in a short period of time. In fact, melanomas grow exponentially in thickness during their active growth phase. [24]

Ability to metastasis: Choroidal melanomas are able to undergo distant metastasis, whereas choroidal nevus is unable to do so. [24]

Risks factors for prediction of growth: There is a lack of overlap between the risk factors for the prediction of growth or enlargement of nevus and melanoma. While choroidal melanomas have multiple risk factors including even UV exposure and welding, the only risk factor for choroidal nevus is age. [24] Slow growth and enlargement of choroidal nevi are found to be more common in younger patients, before becoming stable in mid or late adulthood. [24]

Diagnosis

Unless the choroidal nevus has progressed to a symptomatic form, it can only be discovered during a normal eye examination. [8] The nevus is identified by its distinctive appearance. With a thickness of approximately 2mm and a color between brown to slate gray, the edge of the nevus blends into the retina. [8] It is entirely possible to have more than one nevus in an eye, or have nevi in both eyes. [8]

Diagnostic testing is carried out by ultrasound, fluorescein angiography and OCT. [8] Both OCT and ultrasound fall under ophthalmic diagnostic imaging, [17] allowing practitioners to take direct photographs of eye surfaces. The retinal pigment epithelium (RPE) can be captured as well, using autofluorescence, because the light waves can detect lipofuscin. [17]

A B-scan ultrasound provides the practitioner with an approximate size of the tumor, in addition to vertical and horizontal measurements, [14] while an A-scan determines the amount of internal reflectivity. [14] On the other hand, fluorescein angiography will aid in recognizing whether the tumor has developed its own circulation network. [14]

Optomap is a common diagnostic tool in recognizing a choroidal nevus from a melanoma. [14] It takes an image of the nevus or melanoma using two different lasers - which are red and green. [14] When using the green laser to view the retina, a nevus would be invisible while a melanoma would be visible. [14] Hence, optomap can distinguish a nevus from a melanoma.

Artificial Intelligence (AI) may have the potential for clinical diagnosis of choroidal nevus or melanoma. This can be achieved through machine learning, whereby a large dataset of imaging photographs of all sizes, shapes and location of nevi are used in training. [17] This would improve detection accuracy as well as the design of treatment for nevi and melanoma. [17]

Treatment

Since typical choroidal nevi do not have adverse effects, treatment is not required. Additionally, there are no safe methods to remove nevi from the eye as of now. [10] Nonetheless, annual evaluations and checkups by ophthalmologists are necessary. The American Academy of Ophthalmology recommends adults aged 40 and above to have full eye examinations, as vision loss and eye diseases are most likely to start around this age. [25]

Most choroidal nevi can be managed and monitored by OCT. However, the abnormal development of vascular tissue as a result of the development of nevi can be treated using anti-VEGF agents, injected through the veins. [8] These drugs inactivate the growth factor (VEGF) to reduce neovascularization and swelling. [8] If the choroidal nevus does transform into a melanoma, then it would be treated with cancer therapy.

See also

Related Research Articles

<span class="mw-page-title-main">Melanocytic nevus</span> Skin condition, mole

A melanocytic nevus is usually a noncancerous condition of pigment-producing skin cells. It is a type of melanocytic tumor that contains nevus cells. Some sources equate the term mole with "melanocytic nevus", but there are also sources that equate the term mole with any nevus form.

<span class="mw-page-title-main">Choroid</span> Vascular layer of the eye

The choroid, also known as the choroidea or choroid coat, is a part of the uvea, the vascular layer of the eye. It contains connective tissues, and lies between the retina and the sclera. The human choroid is thickest at the far extreme rear of the eye, while in the outlying areas it narrows to 0.1 mm. The choroid provides oxygen and nourishment to the outer layers of the retina. Along with the ciliary body and iris, the choroid forms the uveal tract.

<span class="mw-page-title-main">Heterochromia iridum</span> Difference in coloration, usually of the iris but also of hair or skin

Heterochromia is a variation in coloration most often used to describe color differences of the iris, but can also be applied to color variation of hair or skin. Heterochromia is determined by the production, delivery, and concentration of melanin. It may be inherited, or caused by genetic mosaicism, chimerism, disease, or injury. It occurs in humans and certain breeds of domesticated animals.

<span class="mw-page-title-main">Macular degeneration</span> Medical condition associated with vision loss

Macular degeneration, also known as age-related macular degeneration, is a medical condition which may result in blurred or no vision in the center of the visual field. Early on there are often no symptoms. Over time, however, some people experience a gradual worsening of vision that may affect one or both eyes. While it does not result in complete blindness, loss of central vision can make it hard to recognize faces, drive, read, or perform other activities of daily life. Visual hallucinations may also occur.

<span class="mw-page-title-main">Nevus</span> Mole or birthmark; visible, circumscribed, chronic skin lesion

Nevus is a nonspecific medical term for a visible, circumscribed, chronic lesion of the skin or mucosa. The term originates from nævus, which is Latin for "birthmark"; however, a nevus can be either congenital or acquired. Common terms, including mole, birthmark, and beauty mark, are used to describe nevi, but these terms do not distinguish specific types of nevi from one another.

<span class="mw-page-title-main">Dysplastic nevus</span> Medical condition

A dysplastic nevus or atypical mole is a nevus (mole) whose appearance is different from that of common moles. In 1992, the NIH recommended that the term "dysplastic nevus" be avoided in favor of the term "atypical mole". An atypical mole may also be referred to as an atypical melanocytic nevus, atypical nevus, B-K mole, Clark's nevus, dysplastic melanocytic nevus, or nevus with architectural disorder.

Ocular melanosis (OM) is a blue-gray and/or brown lesion of the conjunctiva that can be separated into benign conjunctival epithelial melanosis (BCEM) and primary acquired melanosis (PAM), of which the latter is considered a risk factor for uveal melanoma. The disease is caused by an increase of melanocytes in the iris, choroid, and surrounding structures. Overproduction of pigment by these cells can block the trabecular meshwork through which fluid drains from the eye. The increased fluid in the eye leads to increased pressure, which can lead to glaucoma. In humans, this is sometimes known as pigment dispersion syndrome.

<span class="mw-page-title-main">Congenital melanocytic nevus</span> Congenital mole caused by genetic mutations

The congenital melanocytic nevus is a type of melanocytic nevus found in infants at birth. This type of birthmark occurs in an estimated 1% of infants worldwide; it is located in the area of the head and neck 15% of the time.

<span class="mw-page-title-main">Becker's nevus</span> Medical condition

Becker's nevus is a benign skin disorder predominantly affecting males. The nevus can be present at birth, but more often shows up around puberty. It generally first appears as an irregular pigmentation on the torso or upper arm, and gradually enlarges irregularly, becoming thickened and often hairy (hypertrichosis). The nevus is due to an overgrowth of the epidermis, pigment cells (melanocytes), and hair follicles. This form of nevus was first documented in 1948 by American dermatologist Samuel William Becker (1894–1964).

<span class="mw-page-title-main">Uveal melanoma</span> Type of eye cancer

Uveal melanoma is a type of eye cancer in the uvea of the eye. It is traditionally classed as originating in the iris, choroid, and ciliary body, but can also be divided into class I and class II. Symptoms include blurred vision, loss of vision or photopsia, but there may be no symptoms.

<span class="mw-page-title-main">Eye neoplasm</span> Medical condition

An eye neoplasm is a tumor of the eye. A rare type of tumor, eye neoplasms can affect all parts of the eye, and can either be benign or malignant (cancerous), in which case it is known as eye cancer. Eye cancers can be primary or metastatic cancer. The two most common cancers that spread to the eye from another organ are breast cancer and lung cancer. Other less common sites of origin include the prostate, kidney, thyroid, skin, colon and blood or bone marrow.

<span class="mw-page-title-main">Optic disc drusen</span> Medical condition

Optic disc drusen (ODD) are globules of mucoproteins and mucopolysaccharides that progressively calcify in the optic disc. They are thought to be the remnants of the axonal transport system of degenerated retinal ganglion cells. ODD have also been referred to as congenitally elevated or anomalous discs, pseudopapilledema, pseudoneuritis, buried disc drusen, and disc hyaline bodies.

<span class="mw-page-title-main">Blue nevus</span> Type of melanocytic tumor

A blue nevus is a type of coloured mole, typically a single well-defined blue-black bump.

<span class="mw-page-title-main">Choroidal neovascularization</span> Creation of new blood vessels in the choroid layer of the eye

Choroidal neovascularization (CNV) is the creation of new blood vessels in the choroid layer of the eye. Choroidal neovascularization is a common cause of neovascular degenerative maculopathy commonly exacerbated by extreme myopia, malignant myopic degeneration, or age-related developments.

<span class="mw-page-title-main">Halo nevus</span> Medical condition

Halo nevus is a mole that is surrounded by a depigmented ring or 'halo'.

DecisionDx-UM is a prognostic test that accurately determines the metastatic risk associated with ocular melanoma tumors of the eye. Ocular melanoma is a term commonly used to describe tumors of the uveal tract such as uveal melanoma, choroidal melanoma, ciliary body melanoma, and iris melanoma. The DecisionDx-UM test was clinically validated on these tumors of the uveal tract. DecisionDx-UM assesses the gene expression profile (GEP) of a subset of genes which are differentially expressed in primary tumor cells compared to cells that have undergone transformation to a metastatic phenotype.

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Geographic atrophy (GA), also known as atrophic age-related macular degeneration (AMD) or advanced dry AMD, is an advanced form of age-related macular degeneration that can result in the progressive and irreversible loss of retinal tissue (photoreceptors, retinal pigment epithelium, choriocapillaris) which can lead to a loss of visual function over time. It is estimated that GA affects over 5 million people worldwide and approximately 1 million patients in the US, which is similar to the prevalence of neovascular (wet) AMD, the other advanced form of the disease.

<span class="mw-page-title-main">Melanocytoma</span>

A melanocytoma is a rare pigmented tumor that has been described as a variant of the melanocytic nevus and is a derivative of the neural crest. The term "melanocytoma" was introduced by Limas and Tio in 1972.

Polypoidal choroidal vasculopathy (PCV) is an eye disease primarily affecting the choroid. It may cause sudden blurring of vision or a scotoma in the central field of vision. Since Indocyanine green angiography gives better imaging of choroidal structures, it is more preferred in diagnosing PCV. Treatment options of PCV include careful observation, photodynamic therapy, thermal laser, intravitreal injection of anti-VEGF therapy, or combination therapy.

References

  1. 1 2 3 4 Chien, Jason L.; Sioufi, Kareem; Surakiatchanukul, Thamolwan; Shields, Jerry A.; Shields, Carol L. (May 2017). "Choroidal nevus: a review of prevalence, features, genetics, risks, and outcomes". Current Opinion in Ophthalmology. 28 (3): 228–237. doi:10.1097/ICU.0000000000000361. PMID   28141766. S2CID   19367181.
  2. ↑ Boyd, Kierstan (2022-01-11). "Nevus (Eye Freckle)". American Academy of Ophthalmology. Retrieved 2022-04-15.
  3. ↑ Sumich, P.; Mitchell, P.; Wang, J.J. (1998). "Choroidal nevi in a white population: the Blue Mountains Eye Study". Archives of Ophthalmology. 116 (5): 645–650. doi: 10.1001/archopht.116.5.645 . PMID   9596501.
  4. 1 2 Qiu, Mary; Shields, Carol L. (2015). "Choroidal Nevus in the United States Adult Population: Racial Disparities and Associated Factors in the National Health and Nutrition Examination Survey". Ophthalmology. 122 (10): 2071–2083. doi:10.1016/j.ophtha.2015.06.008. PMID   26255109.
  5. ↑ Gass, J.D. (1977). "Problems in the differential diagnosis of choroidal nevi and malignant melanomas. The XXXIII Edward Jackson Memorial Lecture". American Journal of Ophthalmology. 83 (3): 299–323. doi:10.1089/ten.2005.11.1254. PMID   848534.
  6. ↑ Greenstein, M. B.; Myers, C. E.; Meuer, S.M.; Klein, B. E.; Cotch, M. F.; Wong, T. Y.; Klein, R. (2011). "Prevalence and characteristics of choroidal nevi: the multi-ethnic study of atherosclerosis". Ophthalmology. 118 (12): 2468–73. doi:10.1016/j.ophtha.2011.05.007. PMC   3213310 . PMID   21820181.
  7. ↑ Qiu, Mary; Shields, Carol L. (2015). "Relationship Between Female Reproductive Factors and Choroidal Nevus in US Women: Analysis of Data From the 2005-2008 National Health and Nutrition Examination Survey". JAMA Ophthalmology. 133 (11): 1287–1294. doi: 10.1001/jamaophthalmol.2015.3178 . PMID   26402791.
  8. 1 2 3 4 5 6 7 8 "Choroidal Nevus - Patients - The American Society of Retina Specialists". www.asrs.org.
  9. 1 2 3 4 5 6 Optometrist, Dr J. R. Lacey, Therapeutic. "Choroidal Nevus: A Common Eye Condition that can Become Lethal". www.mastereyeassociates.com.{{cite web}}: CS1 maint: multiple names: authors list (link)
  10. 1 2 "Choroidal Nevus » New York Eye Cancer Center". New York Eye Cancer Center. 25 April 2016.
  11. 1 2 Shields, C. L.; Maktabi, A. M.; Jahnle, E.; Mashayekhi, A.; Lally, S. E.; Shields, J. A (2010). "Halo nevus of the choroid in 150 patients: the 2010 Henry van Dyke Lecture". Archives of Ophthalmology. 128 (7): 859–864. doi:10.1001/archophthalmol.2010.132. PMID   20625046.
  12. 1 2 Shields, C. L.; Furuta, M. M.; Berman, E.L.; Zahler, J.D.; Hoberman, D.M.; Dinh, D.H.; Mashayekhi, A.; Shields, J.A. (2009). "Choroidal nevus transformation into melanoma: analysis of 2514 consecutive cases". Archives of Ophthalmology. 127 (8): 981–987. doi:10.1001/archophthalmol.2009.151. PMID   19667334.
  13. 1 2 3 4 5 Li, H. K.; Shields, C. L.; Mashayekhi, A.; Randolph, J.D.; Bailey, T.; Burnbaum, J. Y.; Shields, J.A. (2010). "Giant choroidal nevus clinical features and natural course in 322 cases". Ophthalmology. 117 (2): 324–333. doi:10.1016/j.ophtha.2009.07.006. PMID   19969359.
  14. 1 2 3 4 5 6 7 "Differential diagnosis of ocular melanoma vs. choroidal nevus is crucial". www.healio.com.
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  16. ↑ Jonna, Gowtham; Daniels, Anthony B. (2019). "Enhanced Depth Imaging Optical Coherence Tomography of Ultrasonographically Flat Choroidal Nevi Demonstrates 5 Distinct Patterns". Ophthalmology. Retina. 3 (3): 270–277. doi:10.1016/j.oret.2018.10.004. ISSN   2468-7219. PMC   7906427 . PMID   31014705.
  17. 1 2 3 4 5 Shields, Carol L.; Lally, Sara E.; Dalvin, Lauren A.; et al. (17 February 2021). "White Paper on Ophthalmic Imaging for Choroidal Nevus Identification and Transformation into Melanoma". Translational Vision Science & Technology. 10 (2): 24. doi:10.1167/tvst.10.2.24. ISSN   2164-2591. PMC   7900849 . PMID   34003909.
  18. 1 2 3 4 5 Shields, Carol L.; Furuta, Minoru; Berman, Edwina L.; Zahler, Jonathan D.; Hoberman, Daniel M.; Dinh, Diep H.; Mashayekhi, Arman; Shields, Jerry A. (1 August 2009). "Choroidal Nevus Transformation Into Melanoma: Analysis of 2514 Consecutive Cases". Archives of Ophthalmology. 127 (8): 981–987. doi:10.1001/archophthalmol.2009.151. ISSN   0003-9950. PMID   19667334.
  19. ↑ Shields, C.L.; Dalvin, L.A.; Ancona-Lezama, D.; et al. (2019). "CHOROIDAL NEVUS IMAGING FEATURES IN 3,806 CASES AND RISK FACTORS FOR TRANSFORMATION INTO MELANOMA IN 2,355 CASES: The 2020". Retina. 39 (10): 1840–1851. doi: 10.1097/IAE.0000000000002440 . PMID   30608349. S2CID   58539759.
  20. 1 2 Monsivais-Rodríguez, Fabiola V.; Sweeney, Adam; Stacey, Andrew W.; Gupta, Divakar; Fry, Constance (19 January 2022). "Clinical Evaluation of Choroidal Melanoma". EyeWiki. American Academy of Ophthalmology. Retrieved 10 April 2022.
  21. 1 2 Krantz, Benjamin A.; Dave, Nikita; Komatsubara, Kimberly M.; Marr, Brian P.; Carvajal, Richard D. (2017). "Uveal melanoma: epidemiology, etiology, and treatment of primary disease". Clinical Ophthalmology. 11: 279–289. doi: 10.2147/OPTH.S89591 . ISSN   1177-5467. PMC   5298817 . PMID   28203054.
  22. ↑ Shah, C.P.; Weis, E.; Lajous, M.; Shields, J.A.; Shields, C.L. (2005). "Intermittent and chronic ultraviolet light exposure and uveal melanoma: a meta-analysis". Ophthalmology. 112 (9): 1599–1607. doi:10.1016/j.ophtha.2005.04.020. PMID   16051363.
  23. 1 2 Krantz, B.A.; Dave, N.; Komatsubara, K.M.; Marr, B. P.; Carvajal, R. D. (2017). "Uveal melanoma: epidemiology, etiology, and treatment of primary disease". Clinical Ophthalmology. 11: 279–289. doi: 10.2147/OPTH.S89591 . PMC   5298817 . PMID   28203054.
  24. 1 2 3 4 5 6 7 Mashayekhi, A.; Siu, S.; Shields, C.L.; Shields, J.A. (2011). "Slow enlargement of choroidal nevi: a long-term follow-up study". Ophthalmology. 118 (2): 382–388. doi:10.1016/j.ophtha.2010.06.006. PMID   20801518.
  25. ↑ Seltman, Whitney (7 November 2021). "How Often Should I Get My Eyes Checked?". WebMD. Retrieved 2 April 2022.
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