Ocular drug delivery

Published on June 29, 2023   37 min

Other Talks in the Series: Drug Delivery

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Hello, my name is Dr. Emily Dosmar. I am a professor in the Department of Biology and Biomedical Engineering at Rose-Hulman Institute of Technology in Terre Haute, Indiana. Today, I'm going to speak with you about ocular drug delivery.
Today, I'm going to take you through the general principles governing ocular drug delivery. I'll touch on what the market looks like. We'll go over some fundamentals of ocular anatomy so you're familiar with the terms that we'll be using. We'll talk about some of the classic diseases of the eye and then we'll get into ocular drug delivery itself, where we'll talk about the four primary modalities of delivering pharmacological agents to the eye. We'll talk about topical, intravitreal, subretinal, and subconjunctival delivery.
The global ophthalmic drug delivery systems market is huge. As the baby boomer population ages and as people tend to live longer in general, it's especially important that we offer a solution to the ocular challenges that arise later in life. In 2021, the market was valued at 12.1 billion and is projected to expand at a compound annual growth of 8.3% from 2022-2030, so a significant amount of capital is wrapped up in this market.
I'd like to spend some time establishing some basic understanding of ocular anatomy that will help you as we discuss the different drug delivery modalities. The image that you see in front of you is a side view of the eye with the outward or the world-facing part of the eye on the left. As we move outward-in, we're going to start with our conversation about the sclera. The sclera is the tough outer layer of the eyeball. It's part of the white of the eye and there's a slight bulge in the sclera at the front of the eye that is a clear, thin, dome-shaped tissue called the cornea. The cornea is continuous with the sclera. The cornea is a transparent structure and it's part of the eye that covers the iris and the pupil and allows light to enter the inside of the eye. Moving inward, the conjunctiva is a thin, mucus membrane that lines the inside of the eyelids and covers the sclera. The lens which is further inside of the front of the eye, is a clear elliptical structure that sits right behind the iris, and it's the changes in the curvature of the lens that allow changes to our vision. We can sharpen the focus of our vision through changes in the lens. You'll see the large region of the eye labeled as the vitreous cavity. The vitreous cavity extends from the back of the lens to the back of the eyeball and is crucial for the eye to maintain its shape, and it's filled with a very special liquid called vitreous humor. We're going to touch on this later when we talk about intravitreal injections. The choroid is a thin layer of tissue that is part of the middle layer of the wall of the eye, so it lies between the sclera and the retina, which is at the back of the eye. The choroid is filled with blood vessels that bring oxygen and nutrients to the eye and has noteworthy blood flow that comes into play later when we talk about various types of drug delivery. The retina is a layer of photoreceptor cells and glial cells and several other cell types that sits at the back of the eye, and it captures incoming photons and transmits them along neuronal pathways as both electrical and chemical signals that the brain then uses to perceive vision and to build a visual picture. The retina is crucial for vision. I also want to note that the eye has a special immune privilege. It's one of the few structures in the body that has immune privilege, meaning that it limits its immune response and its inflammatory response so that it could preserve the integrity of the structure and not cause damage and pressure changes that could be devastating to the function of the eye. Part of this immune privilege is also found in the blood-retinal barrier. The blood-retinal barrier is a physiological barrier that regulates the flow of nutrients, metabolic waste products, ions, proteins, and water into and out of the retina, and it keeps things that should not enter the eye from entering the eye, but can also act as a pretty restrictive barrier to drugs trying to enter the eye.