Detectable differences in blood vessel architecture in the eyes of people with Fabry disease could prove useful in diagnosing the disease early, a study has found.
The study, “Optical Coherence Tomography Angiography Findings in Fabry Disease,” was published in the Journal of Clinical Medicine.
Fabry disease can affect many systems in the body, including the eyes, where some of the earliest symptoms occur. The disease can result in changes in the vasculature (blood vessels) of the eyes as detectable by a fundus examination — a technique used by healthcare professionals to look directly at the fundus, the only part of the eye where vasculature can be visualized.
However, fundus exams are highly subjective, so researchers are proposing the use of optical coherence tomography angiography (OCT-A). In simplest terms, OCT-A is a relatively new imaging technique that is functionally similar to a fundus exam — in that the goal is to visualize blood vessels in the eye — but because the process is done primarily by a computer, rather than by a human, there is less subjectivity.
In the new study, researchers used OCT-A to analyze the eyes of 54 people with Fabry disease (34 female, 20 male, average age of 44.1 years) and 70 people without Fabry (36 female, 34 male, average age of 42.3 years).
The OCT-A software analyzed images of the whole retina, and two regions in the retina called the fovea and the parafovea. The retina is a layer of tissue that lines the back of the eye and receives light which is then converted into neural signals to the brain for visual recognition.
For each eye analyzed, the software then automatically calculated vessel density in different vascular networks of the retina: the superficial capillary plexus — which is the region in the retina closer to the surface of the eye — and the deep capillary plexus, which is deeper in the retina.
Among the Fabry patients, 79.6% showed signs of cardiac involvement, 14.8% of renal involvement, and 17.1% of central nervous system involvement, and 70.4% were receiving enzyme replacement therapy at the time.
A total of 25 Fabry patients showed signs of eye involvement: 18 had cornea verticillata (a whorl-like pattern of golden brown or gray deposits in the cornea) and seven had lenticular opacities (also known as cataracts).
The researchers found significant differences in blood vessel density between the groups, but the level of these differences depended on the region of the eye being analyzed.
In the superficial capillary plexus, eyes from people with Fabry had significantly lower vessel density on average (49.95% vs. 51.99% of the people without Fabry). However, in the deep capillary plexus, Fabry eyes had significantly higher average vessel density (54.82% vs. 50.93%). Similar distinctions were seen in the fovea and parafovea, as well as in the whole image of the retina.
The reasons for these differences aren’t totally clear but the researchers speculated that they could be due to the buildup of globotriaosylceramide (a hallmark of Fabry disease), or to differences in blood flow or clotting in Fabry patients. More research is required to fully understand the precise mechanism involved, the researchers said.
“[O]ur study for the first time provides evidence about a complex pattern of microvascular changes affecting the retinal vascular network of [Fabry] patients,” the researchers said. “Given that this condition is characterized by significant systemic vascular involvement, a detailed evaluation of retinal vascular perfusion, using an objective and reproducible tool such as OCT-A, may contribute to early diagnosis.”