The Eye

At Calm Water Therapeutics we design interventions for the surface of the eye that can impact conditions affecting both the surface and interior of the eye.

Ocular Surface Anatomy

Not surprisingly, the eye is a complicated structure. In fact, only the brain is considered to be more anatomically intricate. The main visible eye structures include the pupil, cornea, iris, sclera, conjunctiva, eyelids and eyelashes.

Pupil

The pupil is the usually round aperture (opening) in the center of the iris, the colored part of the eye. The pupil’s role is to allow light to reach the back of the eye which, after passing through the lens and vitreous, is focused onto the retina where it is translated into an electrochemical signal that can be processed into and interpreted as an image by our brain.

Iris

The iris, the colored part of the eye, is composed of pigmented cells, muscle and connective tissue. The iris controls the amount of light getting into the eye by dilating or constricting, making the pupil larger or smaller respectively. The color of the iris results from a combination of locally produced melanin and the white connective tissue in the iris itself.

Cornea

The cornea, along with the sclera, forms the outer structure of the eye imparting its physical shape and containing and protecting its internal components. At its outer edges, the cornea is contiguous with the sclera; the transition point from sclera to the cornea is called the limbus. Unlike the sclera, the cornea is transparent and serves as the window through which light enters the eye. The cornea is also the most powerful refracting surface of the eye. The cornea is continually bathed in tears, and in fact, it is the tear/air interface that imparts the most important refractive transition for light entering the eye. The cornea is composed of 5 to 6 layers of several cell types including epithelial cells, keratocytes, and endothelial cells, and acellular materials including collagen and glycosaminoglycans. The epithelial cells continually turn over and are replenished from the limbal stem cells which reside at the limbus. The cornea is avascular obtaining its oxygen from the air and inner eye, and also utilizes the tears for metabolic support. The cornea is densely innervated, and corneal innervation plays an important role in maintaining ocular health. Corneal disease can involve all aspects of the cornea and corneal damage can occur from trauma as well as external eye disease and tear film abnormalities. Although smaller than the size of a dime, the cornea has enough complexity to make up a major part of a subsp

Sclera

The sclera is the white part of the eye and makes up the outer eyewall in all areas except the cornea. It is about 1mm thick and made of several layers composed of collagen and, in the deeper layers, various cell types. The front part of the sclera is white is covered by the conjunctiva.

Conjunctiva

The conjunctiva is a thin layer of richly innervated and vascularized connective tissue that covers the visible part of the sclera and the parts of the eyelids that touch the eyeball itself. Conjunctival tissue ends at the limbus. The portion of the conjunctiva that covers the sclera is called the bulbar conjunctiva while the palpebral conjunctiva covers the inside of the eyelids. This continuous layer effectively allows the eye to move with minimal friction and it serves as a protective barrier. It also prevents any surface foreign bodies from getting behind the eye. The conjunctiva becomes red and swollen when inflamed.

Tear Film

Like the eye itself, the tear film is quite complex being composed of 100’s of individual components that form essentially three layers on the surface of the eye: an outside (most anterior) lipid layer, a middle aqueous phase, and a posterior mucin layer which is in close contact with the cornea and conjunctiva.

Each major component of the tear film is secreted by a different gland: the lacrimal gland secretes aqueous tears, meibomian glands secrete lipids, and goblet cells secrete mucin. When present in the proper amounts and ratios, these three layers self-assemble to form the tear film that, when properly functioning, covers the entire external surface of the eye. The tear film has many functions including lubrication, moisture maintenance, protection from foreign bodies, and immune function. The tear film also plays a critical role in providing optimal vision as the air/tear interface is the greatest refracting surface of the eye. Corneal and conjunctival surfaces left unprotected because of a disrupted tear film are subject to a host of issues that can lead to structural damage and considerable pain and discomfort. Dry eye disease is fundamentally a disorder of the tear film; it is common and associated with discomfort and decreased vision.