episcleral venous pressure is the pressure inside the small veins on the white of the eye (the episclera). It helps determine how easily fluid inside the eye can drain into the bloodstream. It is most commonly discussed in glaucoma and in conditions that affect venous blood flow around the eye. Clinicians use it as part of understanding why eye pressure is high or difficult to control.

aqueous outflow is the normal drainage of aqueous humor, the clear fluid inside the front of the eye. It is a key part of how the eye maintains healthy intraocular pressure (IOP). Clinicians use the term when discussing glaucoma, eye pressure testing, and pressure-lowering treatments. It is also used in research and surgical planning to describe where fluid exits the eye.

corneal limbal stem cells are specialized cells found at the limbus, the border between the clear cornea and the white sclera. They help renew and repair the corneal epithelium, the cornea’s thin outer “skin.” When these cells are damaged or depleted, the corneal surface can become unstable and cloudy. They are commonly discussed in ocular surface disease care and in certain forms of corneal surface reconstruction.

The tear meniscus is the small “strip” of tears that sits along the edge of the eyelids. It acts like a visible reservoir of the tear film, most often seen at the lower lid margin. Clinicians use it as a practical sign of tear volume and ocular surface health. It is commonly assessed during dry eye and tearing (watery eye) evaluations.

The mucin layer is the mucus-rich interface that helps tears spread evenly over the front of the eye. It is part of the tear film that coats the cornea and conjunctiva every time you blink. In plain terms, it helps the eye’s surface stay “wettable” and comfortable. It is commonly discussed in dry eye disease, contact lens tolerance, and ocular surface exams.

The aqueous layer is the watery middle layer of the tear film that coats the front of the eye. It is produced mainly by the lacrimal glands and spreads with each blink. It helps keep the cornea clear, comfortable, and protected. The term is commonly used when discussing dry eye disease, contact lenses, and ocular surface testing.

The lipid layer is the oily, outermost layer of the tear film that coats the front of the eye. It is mainly produced by the meibomian glands in the eyelids. Its plain role is to slow tear evaporation and help keep vision clear and comfortable. Clinicians commonly discuss it when evaluating dry eye disease and eyelid gland dysfunction.

The tear film is a very thin layer of tears that coats the front surface of the eye. It keeps the eye comfortable and helps create a smooth optical surface for clear vision. Clinicians discuss the tear film when evaluating dry eye, irritation, and fluctuating vision. It is also a focus in contact lens fitting and before many eye surgeries.

Moll glands are small sweat glands located at the eyelid margin, near the eyelashes. They are a normal part of eyelid anatomy and are present in both upper and lower lids. Clinicians refer to Moll glands when describing eyelid health and certain eyelid lumps. They are most commonly discussed in eye exams, eyelid disease, and minor eyelid procedures.

Zeis glands are tiny oil (sebaceous) glands located at the base of the eyelashes. They open into eyelash follicles and produce an oily secretion that helps lubricate the lash line. In clinical eye care, they are most often discussed during eyelid exams and when evaluating “styes” near the lashes. They are part of the broader system of eyelid margin structures that support ocular surface comfort.

meibomian glands are oil-producing glands located in the eyelids. They release an oily substance (meibum) onto the eye’s surface. This oil helps stabilize the tear film and reduce tear evaporation. The term is commonly used in dry eye care, eyelid disease evaluation, and pre-surgical eye assessments.

A canaliculus is a small channel in the eyelid that helps drain tears from the eye. In eye care, canaliculus most often refers to the lacrimal canaliculus, part of the tear drainage system. It connects the punctum (the tiny opening on the eyelid margin) to the lacrimal sac near the nose. Clinicians talk about the canaliculus when evaluating watery eyes, infections, or eyelid injuries.

A punctum is a tiny opening on the eyelid margin near the inner corner of the eye. It is part of the tear drainage system that moves tears from the eye surface into the nose. Clinicians use the term punctum in exams, imaging, and procedures that manage tearing and dry eye. It is commonly discussed in relation to punctal stenosis, tear drainage obstruction, and punctal plugs.

The nasolacrimal duct is part of the tear drainage system that carries tears from the eye into the nose. It connects the lacrimal sac near the inner corner of the eyelids to the nasal cavity. Clinicians discuss the nasolacrimal duct when evaluating watering eyes (epiphora) and recurrent infections. It is also a key structure in several common eye and ENT-adjacent procedures.

The lacrimal sac is a small collecting chamber in the inner corner of the eye’s drainage system. It gathers tears from the eyelids and helps move them into the nose. Clinicians discuss the lacrimal sac when evaluating watery eyes, infections near the nose bridge, or tear drainage blockage. It is also a key landmark in tear-duct testing and certain surgeries.

The lacrimal gland is the main tear-producing gland of the eye. It sits in the upper outer area of the eye socket, just above the eyelid. Its tears help keep the front of the eye smooth, comfortable, and clear. Clinicians commonly discuss the lacrimal gland when evaluating dry eye, swelling near the outer upper eyelid, or orbital (eye socket) disease.

The orbital apex is the narrow, deep “back corner” of the eye socket (orbit). It is the area where key nerves and blood vessels enter the orbit to reach the eye and eye muscles. Clinicians use the term orbital apex when describing anatomy, imaging findings, and certain vision-threatening conditions. It is also referenced in planning surgeries near the orbit, sinuses, or skull base.

The orbital septum is a thin sheet of fibrous tissue in the eyelids. It forms a boundary between the eyelid tissues and the deeper orbital (eye socket) contents. Clinicians use it as an anatomic landmark in eye exams, imaging interpretation, and eyelid surgery. It is discussed often when evaluating eyelid swelling or planning procedures around eyelid fat.

The orbit is the bony socket and surrounding space that contains the eye and its supporting structures. It includes muscles, nerves, blood vessels, fat, and connective tissue that help the eye move and function. In everyday language, “orbit” often means the eye socket. In eye care, orbit is a common term in exams, imaging reports, and surgical planning.

The conjunctival sac is the space between the eyelids and the front of the eye. It is lined by the conjunctiva, a thin, clear tissue that helps protect and lubricate the eye. Clinicians commonly use the conjunctival sac to place eye drops or ointment and to examine the ocular surface. It is also a practical location for rinsing the eye or collecting certain diagnostic samples.