Most people understand the value of sunscreen for the skin. And most people also understand the importance of wearing sunglasses outdoors to protect the eyes. So, the need for an ophthalmic sunscreen is fairly obvious, so why has no one else thought of the idea? Well, they have. We are not the first to have conceived of an ophthalmic sunscreen — but we are definitely the first to have formulated it correctly.
The Multifactorial Challenges
of Developing an Ophthalmic
Sunscreen Solution
If you’ve ever gotten sunscreen into your eyes, you know how irritating they can be. No one else has been successful in formulating an ophthalmic sunscreen because it is an extremely challenging task. To describe our challenges, we must discuss the two types of sunscreen agents: inorganic vs. organic.
Inorganic Agents
Inorganic agents (zinc oxide/titanium dioxide) serve as a “molecular mirror” that “bounce off” UV rays from the skin (you often see lifeguards covering their noses with these products). But they have several problems that make them impossible for use in ophthalmic sunscreen solutions:
- You need to fully cover the area to protect it from the sun; we cannot do that on the human eye as it would cause extreme vision blurriness.
- They would wash off quickly as we blink.
- They are extremely toxic to the eyes.
Organic Agents
Organic agents (Avobenzone/Homosalate) serve as molecular “shock absorbers” from the sun. They absorb UV light and convert it into heat, thereby blocking their damaging effects. These agents work great, but they also have several problems:
- They are extremely irritating to the eyes, even in low concentrations.
- Almost all are oil soluble, causing severe vision blurriness for hours.
- They are not very photo-stable, which means they stop working quickly and would need frequent re-applications to maintain effectiveness.
- They provide good UVA protection but are not that effective in blocking UVB lights, which is the most damaging to the eyes. This means multiple agents would have to be combined for “meaningful” sun protection, which further adds to the complexity and potential side effects.
Calculating the Appropriate SPF
We have demonstrated that 0.25% of PBSA would provide an SPF of about 4 on human skin. However, an SPF of 4 on the skin is the equivalent of 5 times the protection on the eyes, i.e., an SPF of 20. That calculation is based on the interpalpebral surface area of the eye (the exposed region of the eye between the upper and lower eyelids) and the fact that the eyes are under indirect exposure to UV light (they receive UV rays bouncing off of water, snow, etc.)
An accurate calculation of a sun protection factor on the ocular surface is a completely novel idea, and we anticipate a great deal of research will ensue once our product is released on the market. We are extremely excited to introduce a whole new field of scientific research in ocular health science!
The Ultimate Formulation: PBSA
PBSA met all of our strict requirements for an ophthalmic sunscreen solution:
- It’s a water-soluble formulation, so it doesn’t cause any blurriness.
- It’s highly active in a pH range perfectly compatible with the eyes’s natural tears.
- It’s completely non-irritating to the eyes and skin, even in high concentrations.
- It provides outstanding UVB AND UVAII protection.
- It’s extremely photo-stable in solution and provides hours of sun protection.
- It’s approved by the FDA and has been heavily tested for years without exhibiting any adverse systemic adverse effects. It is currently used in countless high-end dermatologic products.
Optimizing the Ocular
Residence Time
One of the most important factors in the feasibility of an ophthalmic sunscreen solution is its ability to stay in the eyes without washing out with tears or blinking — the ocular residence time.
Glycerin-Based Artificial Tear
We have chosen a Glycerin-based artificial tear, ideal for patients more susceptible to evaporative tear loss as they work/play in hot weather. Glycerin improves the performance of demulcents and increases the residence time on the ocular surface by lengthening the tear breakup time, leading to a superior artificial tear product for people exposed to extreme heat.
We have also formulated our solution by utilizing PBSA acting as an osmolyte. The dual role of PBSA helps maintain the integrity of the corneal epithelial cells and the conjunctiva while maintaining the ionic strength of our aqueous solution.
Results of the Ocular Residence Study
We performed an ocular residence study on UVista Eye Drops using an Oculus Z Keratograph 5M, which accurately measures the tear meniscus height residing on the lower eyelids. This demonstrated that the instillation of a single drop of UVista increased the baseline central tear meniscus of the lower eyelid from 35um to 50um, which gradually decreased to 41um even after an hour from the initial instillation.
Considering the ocular residence time of our formulation, we suggest an application of this drop every 1.5 to 2 hours in intense sunlight, which is consistent with dermatological preparations.
The Pioneering Formulation
After years of rigorous testing and research, we have succeeded where no one else has — we have successfully identified a non-irritating, non-blurring ophthalmic sunscreen formulation perfectly compatible with the ocular surface for long-lasting sun protection. With this product, individuals who spend extended periods under the sun can protect their eyes without relying solely on sunglasses.
