The Dry Eye Zone

Dry Eye Glossary

New to dry eye? Look up unfamiliar terms for all aspects of exploring dry eye disease.

Dry Eye Glossary

A

allogeneic serum
Serum eye drops prepared in the same way as autologous serum eye drops (see below), but from someone else's blood rather than your own.

anterior basement membrane dystrophy (ABMD)
   see EBMD

anterior blepharitis
The "outside edge" version of blepharitis occurring around the base of the eyelashes on the eyelids. It is commonly caused by bacteria (staphylococcal blepharitis) or "dandruff" (seborrheic blepharitis). Additional causes include allergies and mite infestations. Anterior blepharitis is typically the red, itchy, crusty/scaly type, but it can also cause meibomian gland dysfunction (MGD). The term blepharitis is sometimes used interchangeably with MGD, but they don't really have the same meaning.

aqueous deficient dry eye (ADDE)
ADDE is when the lacrimal (moisture-producing) glands, which produce the watery part of the tear film, are not producing enough due to disease or damage. The other, more common type of dry eye is evaporative dry eye (EDE). However, it's important to note that dry eye is a spectrum and many people have both types, at least in some degree.

aqueous tear deficiency: see aqueous deficient dry eye

atrophic MGD
When some or all of the meibomian (oil) glands in the eyelids have atrophied, and therefore aren't able to produce the lipids (oil) needed for the tear film.

autologous serum eye drops
This is made by drawing the patient's blood, centrifuging it to separate the components, and then diluting the serum for use as a natural artificial tear substitute. It is stored frozen. Preparation methods may vary slightly. Dilution rates range from 20% to 100%.
   See also: biological tear substitutes

B

bandage lens
Soft contact lens used therapeutically. Bandage lenses are commonly used post-surgically but they are also used for treating things like corneal erosions. It is common for bandage lenses to be worn continuously for up to 30 days.

basal tears
The tear fluid constantly secreted to lubricate, nourish and protect the eyes, as distinct from reflex tears and emotional tears, which are differently composed.
   Also called: constant tears

benzalkonium chloride
A preservative commonly used in prescription eye drops as well as in many over-the-counter drops. It is well known to have toxic effects on the cornea. Ref.

biological tear substitutes
Artificial tear products derived from blood, including autologous serum, platelet-rich plasma, and allogeneic serum.

blepharitis
Inflammation of the eyelids.
   See also: anterior blepharitis, posterior blepharitis, meibomian gland dysfunction

blephasteam
MGD treatment using a moist warm chamber for the eyes. Ref

Blephex
Eyelid cleansing device designed for in-office use only. Ref

blink rate
How many times you blink per minute, which is affected by many things including activity at the time as well as the health of the eyes and eyelids. Ref. 

buffers
Chemicals used in eyedrops to raise or lower the pH of the solution and to keep it stable. Examples of buffers include borate, citrate and phosphate buffers. Ref. 

C

canaliculus
Loop system of channels through which tears drain from the eye (via the puncta) into the lacrimal sac. 

cautery
   See punctal cautery

chalazion
Lump that forms due to blockage and swelling of an oil gland in the eyelid. Sometimes confused with a sty.  Ref

clinical signs
   See signs

conjunctiva
Mucous membrane covering the front of the eye and inside of the eyelids.

conjunctival chalasis
Wrinkled conjunctiva, i.e. excess folds in the conjunctiva.

constant tears
   See basal tears

cornea
The transparent, dome-shaped outermost layer of the eye. For people with dry eye, this is almost always the source of all the pain. The cornea consists of five layers: from the outside in, the epithelium, Bowman's layer, stroma (that's the majority of the cornea), Descemet's membrane, and endothelium. In dry eye we're concerned mostly with the outer layer - the corneal epithelium.

corneal epithelium
The outermost layer of the cornea. The epithelium is the only part of the cornea able to regenerate itself.

corneal erosion
When cells are lifted/torn off the corneal epithelium. It hurts, causes blurry vision and makes your eyes water (that is, if you aren't too dry to cry).
   See also: recurrent corneal erosion

corneal exposure
The cornea is meant to have the eyelids wiping back and forth approximately 17 times per minute. When injury, disease or other factors impair the regularity and completeness of your blink rate, some of the corneal surface can suffer from damaging over-exposure.
   See also: lagophthalmos

cyclosporine ophthalmic emulsion 0.05%
Immunosuppressive drug used to treat chronic dry eye. Approved by the FDA in 2003 and marketed by Allergan.
   Brand name(s): Restasis

D

debridement-scaling (of meibomian glands)
Scraping stuff off the lid margins (more or less).
   See also: microblepharoexfoliation

decongestant eyedrops
Over-the-counter eyedrops sold as "redness relievers" under brand names such as Visine and Clear Eyes, and containing vasoconstrictors. They are often subject to misuse due to lack of consumer awareness and failure to read the labelling. This misuse can cause or exacerbate dryness and damage to the cornea.

demodex
A common parasite in the eyelashes and lids that may be associated with blepharitis and MGD.

diquafosol
A topical secretagogue that stimulates water and mucous secretion.

doxycycline
A broad-spectrum antibiotic that is often prescribed as an oral treatment for meibomian gland dysfunction (MGD).

dysfunctional tear syndrome (DTS)
A name for dry eye disease proposed in 2006 by a Delphi consensus group.

E

epiphora
Excessive eye watering. This can be a symptom of dry eye. It can also occur when a tear duct is blocked, by inflammation or disease, or by punctal occlusion.

epithelial basement membrane dystrophy (EBMD)
A disease affecting the front of the cornea. It has a characteristic slit lamp appearance and is associated with recurrent corneal erosions.
   Also known as: anterior basement membrane dystrophy (ABMD), map dot fingerprint dystrophy (MDFD), Cogan's microcystic dystrophy

epithelium (corneal)
Outermost later of the cornea.

evaporative dry eye (EDE)
One of two main categories of dry eye - but bear in mind there's a lot of overlap. In EDE, the main problem is tear quality, rather than quantity. That is, it's not that you don't make enough tears (from lacrimal gland secretion) but rather that you don't have enough oil in your tears (from meibomian gland secretion) to keep them from evaporating faster than they should. Different cause, but similar results. 

eye print pro
"An optically clear prosthetic scleral device designed to match the exact contours of the individual eye..." EPP involves a technology to produce scleral lenses that are literally molded to your eye by taking an impression of the entire eye surface to design the lens from. Ref

F

filamentary keratitis
The dreaded mucous strings. These filaments are basically mucous and dead cells that form into strings and stick to the corneal surface. For some people they can be persistent, stubborn, and even very painful. Don't pull at them ("mucous fishing"): that can make it worse!

fluorescein
A dye commonly used in dry eye testing. It stains areas of the corneal surface that have been damaged i.e. where cells have been lost. As a powder, it's orange-red; in your eye it will be more yellowish.
    Other dyes: lissamine green, rose bengal

foreign body sensation
That feeling that something is in your eye, when there's really nothing there. It's a common symptom of dry eye. 

G

goblet cells
Cells in the conjunctiva that produce mucous, an essential part of keeping tears on the eyes.
    Ref: TFOS DEWS II Pathophysiology 4.4.3

graft-versus-host-disease (GvHD)
A complication of bone marrow or stem cell transplants from another person. Many patients with GvHD have extremely severe dry eye. 

H

hydroxypropyl cellulose ophthalmic insert
Basically a slow-release artificial tear in pellet form.
    Brand name: Lacrisert

I

idiopathic
Of unknown cause. When they just don't know why.

IDEEL Questionnaire
"Impact of Dry Eye on Every Life", a 55-item survey developed to assess symptoms, impact on daily life, and satisfaction with treatment. Copyright held by Alcon / Novartis. Ref: IDEEL

intense pulsed light (IPL)
A light-based technology employed in dermatology, including for treatment of rosacea. It is also used to treat meibomian gland dysfunction.

intracanalicular plug
Plugs are used to seal off the puncta (openings through which excess tears drain) as a dry eye treatment. Intracanalicular plugs are those that are designed to be inserted all the way into the canaliculus, as opposed to punctal plugs which are placed at the top of the punctum for safety and ease of removal if necessary. Many brands of intracanalicular plugs are dissolvable, while some are made of durable materials.

intraductal probing
Invasive penetration of the meibomian glands with the Maskin Meibomian Gland Intraductal Probe, as a treatment for obstructive meibomian gland dysfunction. Ref

K

keratoconjunctivitis sicca (KCS)
Dry eye, that is, dryness of the conjunctiva and cornea.
    Careful with the acronym - KCS also stands for keratoconus.

keratitis
Inflammation of the cornea.

kerato-
Pertaining to the cornea. 

L

lacrimal gland
Moisture-producing glands located above the eye, in the lateral part of the orbit.

lacrimation
Secretion of tears from the lacrimal glands.

lacrimal insufficiency: see aqueous deficient dry eye

lacrimal apparatus (lacrimal system)
Tear production and drainage system, beginning with the lacrimal glands, which secrete aqueous tears onto the ocular surface. Excess tears drain out through the puncta into the canaliculi (upper and lower), and from there into the lacrimal sac, and then through the nasolacrimal duct into the nasal cavity.

lacritin
Glycoprotein thought to promote basal tear secretion.
    Brand name: Lacripep

lacrisert: see hydroxypropyl cellulose ophthalmic insert. 

lagophthalmos
Incomplete eyelid closure. 

laserfit lenses
Digital lens design system which creates a non-invasive three-dimensional digital mold of the surface of the eye. Ref

lid margin disease: See blepharitis and MGD

lid massage
Refers to the part of a daily eyelid care regimen where you gently massage the lid margins to help express thickened oils after a warm compress. The medical counterpart to this is lid expression in office.

lid scrub
Common but misleading term for eyelid hygiene products. There is no "scrubbing" involved, just gentle cleansing. "Lid scrub" products come in many forms: pre-packaged pre-moistened wipes, foams, liquids, gels and sprays. Examples

lid wiper epitheliopathy (LWE)
The "lid wiper" is the inner edge of the upper lid "wiping" the eye during blinking. LWE is identified by staining of this part of the lid. It is thought that this pattern may be relevant for patients with dry eye symptoms but who don't have other classic clinical signs of dry eye.

lifitegrast ophthalmic solution 5%
Dry eye drug, approved by the FDA in 2016 and marketed by Shire.
     Brand name: Xiidra

lipid layer (of the tear film)
An oil layer, secreted by the meibomian glands in the eyelids. Its purpose is to seal in tears i.e. keep them from evaporating too quickly between blinks.

Lipiflow Thermal Pulsation System
A medical device used in-office to treat meibomian gland dysfunction through a combination of controlled heat, pressure and pulsation on the lid margins. Ref

lissamine green
One of three common stains used in diagnosing dry eye.
    See also: fluorescein, rose bengal

lubricin
Mucin-like glycoprotein secreted by cells that line joint tissues. It is being developed into a topical dry eye treatment.

M

map dot fingerprint dystrophy (MDFD): see EBMD

meibography
Photographic documentation of the meibomian glands using special illumination. Ref.

meibomian gland
Oil-secreting glands whose openings (orifices) are at the lid margin, the thin strip of skin between the lashes and the eye.

meibomian gland dysfunction (MGD)
Blockage or other abnormality of the meibomian glands that prevents them from secreting oil normally.

meibomitis, meibomianitis: see MGD

moisture chambers (moisture chamber glasses)
Glasses or sunglasses designed with a shield (such as foam or silicone, fixed or removable) filling the space in between the frame and the face so as to create a closed, but not airtight, chamber around the eyes. Moisture chambers block air movements and irritants and they increase the humidity in the space immediately around the eyes. More info

mucin / mucous layer (of the tear film)
This used to be described as the "bottom" layer of the tear film, but is now thought to be more mixed in with the aqueous layer. Mucous is secreted by the goblet cells of the conjunctiva and one of its key roles is helping tears adhere to the ocular surface, i.e. keeping the eye wet.

mucolytic
Something that dissolves mucous. Dry eye patients with excess mucous due to a poor quality tear film are sometimes prescribed mucolytic drops, for example to break up mucous filaments.

mucous fishing
The habit of constantly pulling mucous from your eyes.

N

nocturnal lagophthalmos
Incomplete eyelid closure during sleep.

non-steroidal anti-inflammatory (NSAID) eye drops
Topical drops typically prescribed to reduce pain and/or inflammation.

O

ocular rosacea
Condition causing redness and irritation of the eyes and eyelids, common in people who have facial rosacea.

ocular surface
The wet eye surfaces: cornea and conjunctiva.

ocular surface diseases
Diseases affecting the surfaces of the eye (cornea and conjunctiva), including but not limited to dry eye. 

Ocular Surface Disease Index (OSDI)
A simple 12-question survey used to score the severity of dry eye symptoms. This is one of many surveys, but it is one of the best-known and longest in use. It was used in Allergan's original clinical trials of Restasis. There is a smartphone app for it which is handy for routine scoring of your symptoms.

ocular surface sensitivity
How responsive your eye surface is to physical stimulus. A classic test is the Cochet-Bonnet aesthesiometer.

ocular surface staining
Application of a non-toxic dye to the eye surface in order to see damaged areas.

OD, OS
Right and left eye respectively.

ophthalmologist
Medical doctor. MD who specializes in eye and vision care. Ophthalmologists complete college and at least eight years of additional medical training, and are licensed to practice medicine and surgery.

optometrist
Doctor of Optometry. OD. Primary vision care providers who test and correct sight as well as diagnose, treat and manage diseases of the eyes and visual system. Optometrists complete college plus four years of optometry school. 

osmolarity
Concentration, as in, relative number of solute particles in a solution. Tear film osmolarity is an important measure of dry eye, with higher osmolarity meaning a greater likelihood of dry eye disease.

P

photophobia
Sensitivity to light.

phenal red thread test
Tear volume test where a cotton thread treated with pH indicator phenal red is placed under the lid for 15 seconds while you look straight ahead and blink normally. A wet length of 10mm or less is considered dry.  ref

pimecrolimus
Topical immunosuppressant calcineurin inhibitors.

platelet-rich plasma
Drops made by drawing your blood, centrifuging it to remove white and red blood cells, and packaging the undiluted plasma as an artificial tear. It is rich in platelets and growth factors, and is used undiluted. Ref

plugs
Tiny devices used to seal closed the puncta (tear drains) in order to increase the tear volume.
   See also: punctal plugs, intracanalicular plugs

posterior blepharitis
The "inside" version of blepharitis, that is, affecting the side of the lid toward the eye. 

pre-corneal tear film: see tear film

PROSE
"Prosthetic Replacement of the Ocular Surface Ecosystem". Treatment developed by BostonSight (501)(c)(3) nonprofit, founded in 1992 by the late Perry Rosenthal MD. From a medical perspective, PROSE is classed as a prosthetic device and is used to treat complex corneal disease. From a patient perspective, it's a large, sophisticated scleral lens.

punctal occlusion
Closing of the puncta (tear drains) in order to increase the retained tear volume, either by punctal plugs, intracanalicular plugs, or punctal cautery.

punctal plugs
Tiny medical devices, usually made of silicone, that are placed in the puncta to stop or reduce tear drainage, thus increasing retention of the tear film on the ocular surface. 
   See also: intracanalicular plugs

punctum, puncta
Small openings in the upper and lower corners of each eye by the nose through which excess tears drain into the nose (via the canaliculus, lacrimal sac and lacrimal duct). These are the openings that punctal plugs (a tiny device used in dry eye treatment) are placed in. They can also be sealed closed surgically.

R

rebamipide
Mucin secretagogue. 

recurrent corneal erosions (RCE)
Chronic breakdown of the corneal epithelium. In real-life terms, painful episodes usually occurring at night where cells are ripped off the surface of the epithelium causing sharp pain, blurred vision and tearing (unless the eyes are too dry). 

reflex tears
Tears triggered by sensory nerves in the cornea to flood the eye and wash out irritants such as smoke, fumes, dust or grit.

Restasis: see cyclosporine ophthalmic emulsion

rose bengal staining
A dye used in dry eye diagnosis, as it stains abnormal cells on the surface of the eye.
    See also: fluorescein, lissamine green

S

salivary gland transplantation
A treatment for extreme dry eye, where salivary glands are transplanted to replace lacrimal gland function. Ref

schirmer test / schirmer lacrimation test
The Schirmer's test is used to determine whether your lacrimal glands produce enough tears. Numbing (anaesthetic) drops may be used before the test to prevent tearing from irritation from the test itself, helping to ensure that it is measuring basal tears rather than reflex tears. One end of a strip of non-toxic filter paper is placed in each eye, and you keep your eyes closed during the test for 5 minutes, after which the amount of wetting of the strips is measured. Unanaesthetized Schirmer test is rather notorious for false negatives.

sclera
White of the eye.

scleral lens
A large, rigid contact lens whose edges rest on the sclera. Scleral lenses create a tear-filled vault over the cornea and are used to treat a variety of corneal diseases, many of which do not respond to other treatments.
   Also known as: ocular surface prosthesis; scleral contact lens

secretagogue
Medication that can stimulate secretion, for example, a mucin secretagogue enhances secretion of mucin to support tear film adhesion while an aqueous tear secretagogue enhances lacrimal gland secretion.

serum drops: see autologous serum

sicca syndrome
Dryness of the exocrine glands, including lacrimal (tear-producing) glands, when there is no evidence of autoimmune disease.

signs
Things doctors can see or measure with clinical or laboratory testing.
    Compare to: symptoms

sjogrens syndrome
Autoimmune disease characterized by dry eye and dry mouth (among others) due to inflammation of the moisture producing glands. 

stevens johnson syndrome (SJS)
A rare and serious disorder affecting the skin and mucous membranes, resulting from a reaction to a medication or an infection; causes severe dry eye symptoms. In some cases, it can cause extensive damage to the cornea. 

sty / stye
A red, swollen, painful bump at the edge of the eyelid caused by bacteria from the skin getting into and irritating the meibomian (oil) glands.

superficial punctate keratitis (SPK)
Small lesions or opacities on the corneal epithelium.
   Also called: superficial punctate keratopathy

symptoms
Things patients experience, for example: burning, stinging, grittiness, light sensitivity, "menthol sensation", soreness, fluctuating vision.
    Compare to: signs

T

tarsorrhaphy
Sewing upper and lower lids partially together in order to protect the cornea from exposure. Usually it's just a cinching in of the corners to reduce the total area of the cornea that's exposed, but it can be much more drastic and noticeable. With the emergence of better treatments for extreme dry eye, including PROSE and scleral lenses, this is a less common procedure than it used to be.

tear break-up time (TBUT)
Clinical test for evaporative dry eye (EDE), where fluorescein is added to your eye and you refrain from blinking while the tear film is observed under illumination. TBUT is the number of seconds it takes for the first dry spot to appear after you stop blinking.

tearlab
Brand name of a tear osmolarity diagnostic test.
   Ref: TearLab

tears: see tear film

tear film
A complex and far from completely understood fluid that coats the surface of the eye. In simplest terms, it contains water sandwiched between oil on top (lipid layer to slow down evaporation and smooth the surface) and mucous underneath (to help it spread and adhere properly to the eye surfaces). The tear film lubricates, protects and nourishes the eye surfaces including the cornea.

tear meniscus
The space tears take up on the curved surface of the eye - height or cross-sectional volume.
   See also: tear volume

tear volume
Quantitative measurement of the tear film (as opposed to tear composition). Tear volume is measured by tests such as Schirmer, phenol red thread test, and meniscometry.
   Ref: TFOS DEWS II Diagnostic Methodology, 6.4

truetear
A prescription neurostimulation device used to temporarily increase tear production. 
   Ref: Allergan TrueTear

U-V-W-X-Y-Z

vasoconstrictor eyedrops: see decongestant eyedrops

Xiidra: see lifitegrast