Inside the Eye: Interactive 3D Explorer
How to use this explorer
The explorer opens on a whole eye you can turn in 3D. Drag to rotate it, and scroll or pinch to zoom. Three buttons along the bottom change the scene: Whole eye, Cross-section, and Retina view. The Parts and settings panel lets you search for a structure by its name or by what it does, so typing "colored ring" finds the iris. The same panel holds a Take it apart slider, a choice of iris colors, and label controls.
Two more modes sit in the header. The Guided tour has 12 stops. It opens on the whole eye, follows light from the tear film to the retina and its signal on to the optic nerve, and ends with the eye pulled apart. The Microscope puts one tissue at a time on its own stage: the cornea, the retina, the lens, and the drainage angle. On a phone, the Open full screen link above the explorer gives the model the whole display.
This explorer is a teaching illustration. It does not diagnose anything, and an eye exam is what evaluates your own eyes. If your vision changes suddenly, contact your eye doctor right away, or go to the nearest emergency department.
Three ways to look at the eye
Whole eye
From the outside you see the white sclera, the clear cornea over the colored iris, and the optic nerve leaving the back. An adult eye is about 24 millimeters from front to back, roughly the size of a large marble.
Cross-section
The cross-section cuts the eye in half so you can see how the parts nest. Three coats wrap the globe: the outer sclera and cornea, the blood-rich choroid in the middle, and the retina on the inside.
Retina view
The retina view looks in through the pupil at the back wall of the eye, the same view your doctor has during an exam. You can see the optic disc where the nerve fibers leave, the blood vessels that branch out from it, and the macula off to one side. It is one of the few places in the body where blood vessels and nerve tissue can be looked at directly, which is part of why a comprehensive eye exam includes a careful look at it.
The guided tour: following light in 12 stops
Tear film and cornea
Light meets the tear film first, a thin layer of fluid that keeps the surface smooth enough to focus through. Beneath it, the cornea does most of the eye's focusing work, because light bends hardest where it crosses from air into the watery layers inside. Patients fit for scleral contact lenses often have a cornea with an irregular curve, and a scleral lens vaults over it on a cushion of fluid.
Aqueous fluid, iris and pupil
Behind the cornea is a chamber of clear fluid called aqueous humor, which feeds the cornea and lens. The iris is the colored ring, driven by two sets of muscle fibers. One squeezes the pupil small in bright light and the other pulls it wide in the dark. The pupil is the opening left in the middle.
Lens
Just behind the pupil hangs the crystalline lens, held in place by thousands of fine threads called zonules. The zonules run to the ciliary body, a ring of muscle behind the iris. The cornea sets most of the eye's focus, and the lens makes the fine adjustment between far and near.
Vitreous
The large space behind the lens holds the vitreous, a clear gel that fills most of the eye's volume. Strands in the gel can clump with age and cast the drifting shadows people notice as floaters. Long-standing floaters that have not changed are usually harmless. A sudden new shower of them, flashes of light, or a shadow across your vision needs to be looked at right away. Contact your eye doctor, or go to the nearest emergency department.
Retina, macula and fovea
Light lands on the retina, a thin film of nerve tissue that grows out of the brain before birth and stays connected to it for life. At its center sits the macula, the small patch that carries your sharpest vision. The fovea is the shallow pit at the center of the macula, where the overlying wiring is swept aside so light reaches the cones with less tissue in the way. Nearsightedness often traces back to an eyeball that has grown slightly too long for its own optics, which is why myopia management for children aims to slow that growth early.
Rods and cones
Partway through the tour the scale changes and the camera drops into the retina itself. Rods handle dim light and motion at the edges of your view. Cones handle color and fine detail, and they are packed most tightly at the fovea.
Optic nerve
About a million nerve fibers gather at one spot and leave the eye together as the optic nerve. That spot has no rods or cones, so every eye has a small blind spot the brain fills in. Optic nerve tissue does not grow back once it is lost, which is why routine exams look at it year after year. The last stop of the tour pulls the whole eye apart so you can see every piece in order.
Under the microscope
Cornea: five clear layers
The cornea stage separates five layers. The epithelium is the surface skin, and it heals quickly. Bowman's layer is a tough sheet beneath it. The stroma is the thick middle, made of collagen laid down so evenly that it stays transparent. Descemet's membrane backs the stroma, and the endothelium pumps fluid out to keep the cornea clear. Contact lens comfort depends a great deal on how well the surface layer holds a stable tear film.
Retina layers
The retina stage lifts out a magnified block with its layers stacked in order, from the nerve fibers on the inner surface down to the rods and cones, the pigment layer that supports them, and the fine blood supply beneath. Changes in macular health often show up in one of these layers on an imaging scan before a person notices any change in vision.
Lens and focus
The lens stage is animated. For distance, the ciliary muscle relaxes, the zonules pull tight, and the lens flattens. For near, the muscle contracts, the zonules slacken, and the lens rounds up. That change is called accommodation. The presbyopia setting shows the same muscle working against a stiffer lens, which is why reading glasses or multifocal lenses tend to arrive in the 40s. The cataract setting shows the lens clouding, which becomes more common later in life.
Drainage angle
The drainage stage opens the angle where the iris meets the cornea. Aqueous fluid filters through the trabecular meshwork, a sponge-like tissue, and collects in Schlemm's canal on its way out of the eye. The balance between fluid made and fluid drained sets the pressure inside the eye. Raised pressure is a major risk factor for glaucoma, which damages the optic nerve. Glaucoma can also develop at normal pressure, so an exam checks the nerve itself along with the number.
About this illustration
This is an educational 3D illustration created for Central Ohio Vision and Eyecare in New Albany, Ohio. Colors are illustrative and used to tell structures apart. Cell sizes, numbers, and spacing are simplified and enlarged so they read clearly on screen.
References: National Eye Institute, How the Eyes Work; Webvision, Simple Anatomy of the Retina and Photoreceptors; American Academy of Ophthalmology EyeWiki, Basic Histology of the Eye.
More interactive explainers live in the COVE education hub.
Book an eye exam in New Albany
A comprehensive eye exam looks at nearly every structure covered above, from the cornea and lens to the retina, macula, and optic nerve. Dr. Matthew Karres, Dr. Amy Keller, and Dr. Kayli Dennis all see patients for routine and specialty eyecare at COVE.
Schedule an eye exam online, or call (614) 933-0575.