Multimodal imaging characterization of structural phenotypes and biomarkers in choroidal hemangioma associated with Sturge–Weber syndrome

The human eye is a complex camera, but unlike a machine, its internal layers are living tissue that constantly interact. At the back of the eye lies the retina, a delicate sheet of light-sensitive cells, which rests on a layer of pigment cells and a rich network of tiny blood vessels that supply them with oxygen. When this delicate balance is disturbed, the layers can warp, thicken, or develop strange deposits, often signaling a deeper problem. One such problem is Sturge–Weber syndrome, a rare condition present from birth that affects the skin, brain, and eyes. People with this syndrome often have a distinctive red birthmark on their face, caused by a tangle of blood vessels, and they frequently develop similar vascular tangles inside the eye. These internal tangles, known as choroidal hemangiomas, are benign growths of blood vessels that sit behind the retina. While they do not spread like cancer, they can cause significant vision loss by pushing on the retina or disrupting the flow of nutrients, yet they are often difficult to spot in their early stages because they can look like a subtle, reddish haze rather than a distinct lump.

For years, doctors have relied on standard photographs of the back of the eye to identify these growths, but this method often misses the subtle changes happening at the microscopic level. A new study from researchers at Sapienza University of Rome has taken a closer look, using a suite of advanced, non-invasive imaging tools to map the hidden structural changes caused by these vascular growths. By combining high-resolution photographs with deep-penetrating laser scans and cross-sectional views of the eye's layers, the team created a detailed portrait of how the eye remodels itself in response to the pressure and poor blood flow caused by the hemangioma. Their work reveals that the eye does not just passively sit under a mass; it actively changes its architecture in specific, predictable ways that can now be seen and measured without surgery.

The researchers examined the eyes of sixteen patients who had both Sturge–Weber syndrome and confirmed diffuse choroidal hemangiomas. They used a standardized protocol that included taking standard color photos, infrared images that see deeper into the eye, and specialized scans that slice through the retina to show its layers in high definition. The team, working independently and without knowing the specific details of each patient's case beforehand, looked for patterns in the images. They were searching for signs of stress in the neurosensory retina, the pigment layer, and the tiny capillaries that feed them. What they found was a consistent set of four distinct structural changes, or "phenotypes," that appeared across the group.

The most common finding, seen in more than four out of five eyes, was the appearance of tiny, bright dots scattered across the back of the eye. On the deep-penetrating infrared images, these looked like a fine, granular dusting of light. When the researchers matched these dots to the cross-sectional scans, they discovered these bright spots were actually small, round-to-angular structures located in the choriocapillaris, the layer of tiny blood vessels just beneath the retina. These structures appeared specifically in the area overlying the vascular tumor. The researchers suggest these dots likely represent a reaction to the tumor, where the blood vessels become compressed or scarred, and the pigment cells above them begin to change, perhaps forming small fibrous nodules as a response to the chronic stress.

In about two out of five eyes, the team observed a different kind of distortion: folds in the inner layers of the retina. On the surface images, these appeared as faint, linear wrinkles or ripples, particularly near the center of vision. The cross-sectional scans confirmed that these were physical undulations of the innermost membrane of the retina and the nerve fiber layer. This suggests that the growing mass of blood vessels beneath is physically pushing up on the retina, causing it to buckle and fold much like a rug might wrinkle if something heavy were placed underneath it. These folds were a clear sign that the tumor was exerting mechanical force on the delicate tissue above it.

A third finding, seen in roughly one-third of the eyes, involved the appearance of deposits that looked very similar to drusen, the yellowish spots often associated with age-related macular degeneration. However, in these patients, the deposits were not caused by aging but by the hemangioma. The scans showed granular, bright material sitting between the light-sensitive cells and the pigment layer. In some cases, this material formed small, distinct bumps. The researchers noted that this pattern closely resembled a specific stage of subretinal drusenoid deposits, a condition usually linked to poor blood flow and oxygen deprivation. Given that the hemangioma creates a chaotic and inefficient blood supply, the researchers propose that the resulting lack of oxygen causes the pigment cells to malfunction and leak this material, leading to the formation of these drusen-like structures.

The least common finding, appearing in fewer than one out of five eyes, was a sharp, bright line that curved across the back of the eye. This "demarcation line" was visible on the infrared images and corresponded to a sudden, steep rise in the retinal pigment layer on the cross-sectional scans. These cases were distinct because the tumors were significantly thicker, compared to the other eyes. In two-thirds of the eyes with this line, the researchers also saw a radiating pattern of cracks spreading out from the optic nerve, resembling a condition known as angioid streaks. The team suggests that the extreme thickness and volume of the tumor in these specific cases caused the underlying support layer of the eye to stretch and eventually fracture, creating these visible lines.

The study concludes that the eye's response to a Sturge–Weber hemangioma is not random but follows a specific spectrum of structural changes. These changes, ranging from tiny bright dots to large folds and cracks, are the result of two main forces: the physical pressure of the growing mass and the metabolic stress caused by an inefficient blood supply that fails to deliver enough oxygen to the outer retina. By identifying these specific patterns, the researchers have provided a new set of visual markers that doctors can use to track the disease. These markers offer a way to understand the chronicity of the condition and monitor its progression without invasive procedures. The work highlights that even when a tumor is benign, its presence triggers a complex cascade of remodeling in the surrounding tissue, and recognizing these subtle signs is crucial for preserving vision before irreversible damage occurs.