The term “bear tracks in the eyes” refers to a specific, often harmless finding during a routine eye examination. The formal medical name is Congenital Hypertrophy of the Retinal Pigment Epithelium (CHRPE). Although the name may sound alarming, these lesions are typically benign variations in the eye’s structure.
What Are Congenital Hypertrophy of the Retinal Pigment Epithelium (CHRPE)?
CHRPE lesions are flat, pigmented spots located in the fundus, the interior surface at the back of the eye. They originate in the retinal pigment epithelium (RPE), the layer of cells supporting the retina. Their dark appearance results from RPE cells in that area being larger and containing a higher concentration of melanin pigment.
These lesions are well-defined, usually circular or oval, and range in color from dark gray to black. The characteristic “bear tracks” appearance describes a less common variant called grouped pigmentation of the retina. This grouped type consists of multiple, smaller, dark spots clustered together in one sector, resembling animal footprints.
The most common presentation is a single, isolated lesion, typically found in the peripheral retina of one eye. Both isolated and grouped lesions are generally confined to one sector of one eye. Isolated lesions may sometimes have a clear, non-pigmented border or small, pale areas, called lacunae, within the dark spot.
The Developmental Cause and Non-Progressive Nature
The term “congenital” indicates that CHRPE is present from birth, stemming from a localized developmental anomaly. The lesions are not caused by external factors like injury or infection, but result from RPE cells developing differently. The condition involves a proliferation of RPE cells that are both larger (hypertrophy) and more numerous (hyperplasia).
For the majority of individuals with isolated CHRPE, the prognosis is excellent because the lesion is typically benign. They are generally asymptomatic and do not cause noticeable visual impairment, as they are often located away from the central vision area. Isolated CHRPE is considered non-progressive in a harmful sense and carries no increased risk of eye cancer, though some lesions may enlarge subtly over many years.
Systemic Implications: The Link to Familial Adenomatous Polyposis
While most CHRPE findings are isolated and benign, certain patterns can serve as an important clinical marker for Familial Adenomatous Polyposis (FAP). FAP is an autosomal dominant cancer syndrome that causes hundreds to thousands of adenomatous polyps in the colon and rectum. If left untreated, FAP carries an almost 100% risk of developing colorectal cancer.
This connection stems from a shared genetic cause: both FAP and FAP-associated CHRPE are linked to a mutation in the Adenomatous Polyposis Coli (APC) gene. This mutation is responsible for the uncontrolled cell growth leading to polyps and the pigmented eye lesions. Atypical or multiple CHRPE lesions are often considered the earliest extracolonic manifestation of FAP, sometimes detectable in infancy.
Ophthalmologists look for patterns highly suggestive of FAP, which differ from the common isolated lesion. FAP-associated lesions are frequently bilateral (appearing in both eyes) and scattered across multiple quadrants of the retina. They often exhibit a distinct “pisiform” or fish-shaped appearance with irregular borders, distinguishing them from the common bear track pattern. The presence of these specific patterns acts as a non-invasive screening tool, prompting referral for genetic testing and colon cancer screening.
Clinical Diagnosis and Long-Term Monitoring
CHRPE is typically discovered incidentally during a comprehensive dilated eye exam, as most individuals experience no symptoms. The ophthalmologist uses specialized instruments to view the back of the eye and identify the characteristic flat, pigmented lesions. Diagnosis requires thorough documentation of the lesion’s size, location, and specific characteristics.
If the lesions are isolated or fit the classic grouped “bear track” pattern, the ophthalmologist usually recommends observation and regular follow-up exams. This monitoring ensures the lesion remains stable and that no concerning changes, such as unexpected growth or malignant transformation, occur (though this is rare).
If the eye exam reveals multiple or bilateral lesions suggesting FAP, the ophthalmologist coordinates a referral to a gastroenterologist or genetic counselor. This multidisciplinary approach determines if the APC gene mutation is present and initiates necessary colorectal cancer screening, such as a colonoscopy. Even without a family history, the specific pattern of the eye lesions can be the first indication of a potential systemic risk.