When an eye specialist examines the back of your eye, a distinct pattern called a tessellated fundus may be noted. The “fundus” refers to the interior surface of the eye, including the retina, optic disc, and blood vessels. A tessellated, or mosaic, appearance is characterized by a visible, tiled pattern of light and dark areas across this surface. This finding is not a disease but a description of what the doctor observes. Understanding the structures that create this pattern helps clarify if it is a variation of normal anatomy or an indication of an underlying change.
The Anatomy Behind the Appearance
The patterned look of a tessellated fundus results from the interplay between two distinct layers beneath the light-sensing retina. The innermost layer is the Retinal Pigment Epithelium (RPE), a sheet of cells containing melanin, the pigment responsible for coloring the skin and hair. The RPE normally acts as a dark screen, obscuring the structures beneath it from view. Directly under the RPE lies the choroid, a dense network of large blood vessels that supplies oxygen and nutrients to the outer layers of the retina.
The tessellated pattern becomes visible when the RPE contains less melanin pigment or when the entire RPE layer is thinner. This reduced pigmentation creates a translucent screen, allowing light to penetrate and reflect off the underlying choroidal vessels. The dark stripes of the pattern are the shadows of these large blood vessels, while the lighter spaces are areas of less pigment and thinner tissue. The visibility of this vascular network is directly proportional to the RPE’s pigment density.
Tessellated Fundus as a Normal Variation
In many individuals, a tessellated fundus represents a benign physiological variation. This appearance is strongly associated with the natural distribution of melanin, meaning individuals with lighter skin tones or fairer hair often exhibit this pattern. The RPE layer in these cases is naturally less pigmented, a condition sometimes referred to as a “blonde fundus.” This reduced pigment density allows for the easy visualization of the choroidal vasculature without any structural abnormality or disease.
When the eye is otherwise healthy, this mosaic pattern is a stable finding that does not impact visual acuity or lead to future complications. It simply reflects a normal, healthy eye with less dense pigmentation in the back layers. For these individuals, the observation of a tessellated fundus during a routine exam requires no specific treatment or heightened concern.
The Pathological Significance
The presence of a tessellated fundus can indicate structural changes within the eye rather than natural pigmentation differences. This appearance is frequently observed in eyes that have experienced mechanical stretching and thinning, often due to moderate to high myopia, or nearsightedness. High myopia is defined as a refractive error of six diopters or more, or an eye with a significantly longer axial length. In these cases, the eyeball has elongated, causing the layers of the eye wall to stretch and become thinner.
The stretching of the eye wall leads to a corresponding thinning of the RPE and the choroid, which makes the underlying choroidal vessels more prominent and the tessellated pattern more pronounced. This type of pathological tessellation is considered the earliest stage in the classification of myopic maculopathy, which describes vision-threatening complications associated with high myopia. The increased visibility of the choroidal vessels in this context is a physical sign of reduced tissue thickness.
The thinning of the choroid and RPE increases the risk for more serious complications due to mechanical stress. These risks include the development of diffuse chorioretinal atrophy, where the thinned tissue wastes away, and choroidal neovascularization, which is the growth of abnormal blood vessels beneath the retina. Because the tessellated fundus can be an initial indicator of these progressive changes, regular monitoring is often recommended for individuals with high myopia. This closer observation allows eye care professionals to track the stability of the eye and intervene promptly if advanced myopic complications develop.