Pigmented fundus lesions are commonly encountered on routine ophthalmological dilated examinations and may be sent to your practice for further evaluation after being identified by another health care professional. Pigmented lesions may represent a benign or malignant process. They can be congenital, acquired, or the result of an infectious or inflammatory process affecting the retinal pigment epithelium (RPE), the layer that provides the natural pigmentation of the fundus.
Generally, outside of congenital lesions, pigmented lesions tend to be seen more in the elderly population (over 40), with a split prevalence among males and females. Prevalence rates vary from 0.2 to 30% for choroidal nevi.1-3
Some lesions have discrete focal patterns, while others may be more diffuse; various lesions have a predisposition for specific ethnic groups, and others may occur due to different environmental exposures. Sometimes a combination of factors may lead to the development of a pigmented lesion.
RPE cells contain melanosomes of neuroectodermal origin that develop during the second trimester of development. RPE cells transport nutrients, ions, and water, phagocytose the outer rods and cones, maintain the blood-ocular border, metabolize vitamin A, secrete factors essential to the integrity of the retina structurally, convert all-trans-retinal into 11-cis retinal, and absorb light with protection against photooxidation.4
Disruptions of the RPE layer may lead to:
- atrophy of RPE cells,
producing various pigmented configurations.4
Most pigmented lesions are asymptomatic and discovered incidentally during routine eye exams; however, some may present with symptoms ranging from floaters, field loss, photopsias, reduced visual acuity, and pain. While some lesions may be harmless, others may be sight or even life-threatening.
Distinguishing and diagnosing lesions represents a diagnostic challenge for eyecare providers. Some studies reveal as low as a third of new intraocular tumor patients referred to tertiary ocular oncology care centers are sent with the correct diagnosis.5 In this overview, we will discuss the differential diagnoses and the management of some of the more common pigmented lesions encountered on routine clinical examination.
Congenital Hypertrophy of Retinal Pigment Epithelium (CHRPE)
Congenital hypertrophy of retinal pigment epithelium (CHRPE) represents an asymptomatic solitary, flat, and well-demarcated pigmented lesion whose shape may be round, elliptical, or irregular. These lesions may also contain non-pigmented areas within called "lacunae" and non-pigmented lines at the lesional margins ("halo"). Additionally, there may be overlying retinal vessel abnormalities such as vascular sheathing and attenuation.
As the name suggests, CHRPE occurs secondary to hypertrophy and hyperpigmentation of the RPE layer. CHRPE lesions should be classified as typical or atypical.
Typical lesions are often round and solitary as described above and may even feature enlargement of the lacunae over time. Typical CHRPE lesions can sometimes have a "bear track" appearance when multiple small lesions are seen in a cluster pattern.
Atypical lesions include pigmented RPE lesions that are pisciform or spindle-shaped, bilateral, and multiple in number. Atypical presentations of CHRPE may represent a higher predisposition for familial adenomatous polyposis (FAP), a risk factor for developing colon cancer.
Figure 1 demonstrates typical grouped CHRPE.
Figure 1: Mishra et al.
Figure 2 illustrates atypical pisiform CHRPE.
Figure 2: Diebert et al.
On fundus autofluorescence (AF), CHRPE displays a uniform area of hypo-autofluorescence while the lacunae appear iso-auto fluorescent. On infrared (IR) imaging, CHRPE lesions are hyporeflective, while the lacunae are hyperreflective.
On OCT, CHRPE appears as a thicker, brighter RPE band with overlying disruption (sometimes absence) of the outer nuclear layer and ellipsoid zone (see Figure 4 below).