I’m not sure about you, but the only time I really think about what’s in my eyes is when I sit up quickly and end up seeing floaters. Well, that, and any time I think about having crystals at the head of my optic nerves… but the American Academy of Ophthalmology says there’s nothing to worry about too much.
However, just as with any other part of the body, eyes have a wealth of information, and some interesting treatments have come up around them. Last time in our Amazing Samples blog series, we discussed curry the interesting applications of bone marrow research – this time, let’s take a long hard gander at ocular research.
A Brief Overview of the Eye
Let’s begin by briefly reviewing the parts of the eye. At a very basic level, the cornea, iris/pupil, and lens in the front of the eye work together to focus light in such a way that it hits the retinal tissue in the back of the eye, where signals get shunted through the optic nerve and to the brain, where the data is hashed together to make images. Surround this with the muscles to move the eye, ligaments to hold bits in place, the actual blood vessels, and the vitreous body (more like gel, though it liquefies over time) that fills the inside of the eye, and that’s an eyeball. There are many interesting facts about the eye’s makeup, such as the fact that each eye has a retinal blind spot at the optic nerve head (that your brain tries to ignore). If you want a closer look, there a dozens of sites like this to give you the full breakdown.
Accessing the Vitreous Body
Generally speaking, the vitreous body inside the eye has been held sacrosanct – unless there is no helping it, you leave it alone. Vitrectomies have been performed since Robert Machemer first developed the pars plana approach around 1970, but at the time it was primarily used for removing vitreous that compromised vision, such as being cloudy from blood. While still in use today, such treatments have a slight air of similarity to medieval medical technology—sure, drilling a hole in your head can relieve pressure-based headaches, but these days an aspirin should suffice. Vitrectomies are also used before attempting to use laser- or cryotherapy treatment of retinal detachments, and for that purpose there have been various advances in substitutes for the humor. Beyond using these treatments as a last resort, no one had wanted to risk compromising a patient’s vision by interfering with the vitreous... until recently.
When it comes to the applications of ocular samples, proteomics is an obvious front runner, at least over the past decade. For a number of ocular indications, such as age-related macular degeneration (AMD), cataracts, or various retinopathies, biomarkers in the vitreous are the best source of biomarkers for analytical and diagnostic purposes. For example, one lab has fine-tuned the diagnostic sampling process for small quantities of vitreous to be an in-office procedure with minimal complications, and has been using that technique to develop vitreous-based diagnostic tools for both wet and dry AMD, as well as diabetic retinopathy. Another doctor used the vitreous from other patients’ vitrectomies to discover that the vitreous body absorbs oxygen, and has accordingly hypothesized that the vitreous body’s liquefaction actually compromises its ability to protect the lens from retina-derived oxidative stress.
Additionally, the Journal of Visualized Experiments has a video and discussion on the dissection of the vitreous body for proteomic analysis. (We'd embed it, but this video really isn't for the squeamish or the weak of stomach.)
Biobanking Retinal Tissue
While the vitreous body might have great value as a diagnostic target, the actual retinas or corneas tend to be the elements that need actual treating or transplanting. Banking this tissue viably has always been problematic – not only are there so few human donors that some corneal transplants receive shark eyes, but many of the remaining eyes are used for other corneal transplants that the choroid and retinal tissue are even more difficult to obtain. This is especially true on the topic of cell therapies – beyond straightforward uses for transplantation, the retina has certain stem and progenitor cells that could be used as cell therapies, and this low availability has a detrimental effect on the number of groups developing such treatments.
However, as the Inside Biobanking blog mentioned a few months ago, there are many whole-globe eye biobanks, where they receive enough quantity of eyes that they can devote a certain portion for retinal stem cells. As there are various concerns with both endogenous induced pluripotent cells and embryonic or fetal stem cells, banking healthy retinal tissue might be the best course of action. Additionally, since biorepositories can equip themselves to track large amounts of data attached to each sample, issues like immunogenicity and histocompatability can be addressed beforehand and greatly reduce the chances of transplant rejection.
As this doctor explains, the corneal transplant procedure is required for two different reasons, for two very different age groups:
Anyone can be an eye donor, such as Janis Babson, who registered as a donor by her own initiative before passing away at the age of 10 from leukemia. If you’re interested in helping restore someone’s sight after you’ve passed, consider signing up with one of the many non-profit eyebanks around the world, such as this one.
Whether for biomarker research or cell therapy development, all parts of the eye can be an Amazing Sample. Do you work with retinal tissue, vitreous body, or other parts of the eye? Comment below to share your story!
The DO-HEALTH clinical trial is creating a biobank of processed samples for downstream research, greatly enhancing the potential value of the data collected during the interventions and potentially enabling the development of other preventive strategies. To learn more about this clinical trial and the biobank for biomarkers, download our eBook European DO-HEALTH Clinical Trial Aims at Simple, Affordable Interventions to Improve Senior Health.