keratoconjunctivitis sicca is the clinical term for “dry eye” that affects both the cornea and the conjunctiva. It describes an ocular surface condition where the tear film does not adequately protect and lubricate the eye. The term is commonly used in eye clinic notes, research literature, and diagnostic coding.

dry eye disease is a common condition in which the eye’s tear film does not adequately lubricate and protect the ocular surface. It can cause discomfort, visual fluctuation, and irritation that may come and go or persist over time. The term is used in eye clinics to describe a specific set of symptoms and clinical findings related to tear film dysfunction. It is discussed across ophthalmology, optometry, primary care, and vision science because it affects everyday activities like reading and screen use.

pattern standard deviation (PSD) is a number reported on many automated visual field tests. It describes how “uneven” a person’s sensitivity is across the tested field of vision. It is commonly used in glaucoma care and neuro-ophthalmology to summarize localized visual field loss. It is interpreted alongside other visual field indices and the full test printout.

mean deviation (MD) is a single number that summarizes how much a visual field test differs from expected normal vision for a person’s age. It is most commonly reported on automated perimetry tests used in glaucoma care and neuro-ophthalmology. It is expressed in decibels (dB) and typically becomes more negative as overall visual field loss increases. Clinicians use it as a “global index” to track change over time alongside other measurements.

visual field index (VFI) is a single number that summarizes how much of a person’s visual field is functioning compared with an age-adjusted “normal” reference. It is most commonly reported on automated visual field tests used in glaucoma care. Clinicians use it to describe severity and to track change over time in a way that is easy to trend. For patients, it can be a simpler snapshot than reading every point on a visual field printout.

orbital MRI is a magnetic resonance imaging scan focused on the eye sockets (orbits) and nearby structures. It creates detailed pictures of soft tissues, such as the optic nerve, eye muscles, and orbital fat. It is commonly used in ophthalmology, optometry referral pathways, neurology, and radiology. It helps clinicians evaluate eye-related symptoms when the cause may involve deeper tissues that cannot be seen on routine eye exam.

orbital CT is a computed tomography scan focused on the eye sockets (the orbits) and nearby facial structures. It uses X‑rays and computer processing to create detailed cross‑sectional images. It is commonly used in emergency care, eye clinics, and hospital radiology departments. Clinicians use it to evaluate trauma, inflammation, infection, tumors, and many orbital and sinus problems.

visual evoked potential (VEP) is a test that measures how the brain’s visual system responds to visual stimulation. It records tiny electrical signals from the back of the head (the visual cortex) after the eyes see a pattern or flash of light. Clinicians use it to evaluate how well signals travel from the eye through the optic nerve to the brain. It is commonly used in neuro-ophthalmology, optometry, and neurology when vision symptoms are difficult to explain with routine eye exams alone.

electro-oculography (EOG) is a test that records small electrical signals related to eye position and retinal health. It uses skin electrodes placed around the eyes to measure changes in electrical potential as the eyes move. In ophthalmology, it is most known for evaluating retinal pigment epithelium (RPE) function in certain retinal disorders. It is also used in some vestibular (balance) and neurology settings to track eye movements.

multifocal ERG is a retinal function test that records tiny electrical signals generated inside the eye in response to light patterns. It measures how different small areas of the central retina are working, rather than giving one overall average result. It is commonly used in ophthalmology and optometry clinics to evaluate unexplained vision symptoms and to support diagnosis or monitoring of macular and retinal conditions. It is a diagnostic test, not a treatment.

electroretinography (ERG) is a diagnostic test that measures the retina’s electrical responses to light. It helps clinicians assess how well retinal cells are functioning, even when the retina looks normal on exam. It is commonly used in ophthalmology and optometry clinics, hospital eye departments, and specialized retina practices. It can support diagnosis and monitoring of inherited, toxic, and ischemic retinal conditions.

esthesiometry is the measurement of sensation, most often the sensitivity of the cornea (the clear front window of the eye). It helps clinicians understand how well the eye can detect touch or other stimuli on the ocular surface. It is commonly used in ophthalmology and optometry to evaluate corneal nerve function. It can support the assessment of dry eye, nerve-related corneal disease, and recovery after certain eye surgeries.

corneal sensitivity is the cornea’s ability to feel touch, temperature, and irritation. It reflects how well corneal nerves and protective reflexes are functioning. Clinicians use it as a sign of ocular surface health and corneal nerve integrity. It is commonly assessed during evaluations for dry eye, corneal disease, and after eye surgery.

lid eversion means gently turning an eyelid outward to see the inner lid surface. It is most often done to examine the upper eyelid and the tissue behind it. Clinicians use it during routine eye exams and urgent evaluations for irritation or pain. It helps reveal problems that can hide under the lid, such as a foreign body or inflammation.

meibography is an eye imaging test that shows the structure of the meibomian glands inside the eyelids. It is most often used to evaluate dry eye related to meibomian gland dysfunction (MGD). The images help clinicians see gland loss, shortening, or blockage patterns more clearly than with a routine external view. It is commonly performed in optometry and ophthalmology clinics as part of ocular surface and dry eye evaluations.

tear osmolarity is a measurement of how concentrated the tear film is on the surface of the eye. It reflects the balance between water, salts (electrolytes), and other tear components. It is commonly used in eye clinics as part of dry eye disease evaluation and ocular surface assessment. It helps clinicians interpret symptoms and signs that may not always match.

rose bengal is a diagnostic dye used in eye exams to highlight certain problems on the eye’s surface. It is most often used in ophthalmology and optometry clinics during a slit-lamp exam. The dye can make damaged or unprotected areas of the cornea and conjunctiva easier to see. It is commonly discussed in the context of dry eye disease and other ocular surface disorders.

lissamine green is a diagnostic dye used during eye exams to highlight certain ocular surface changes. It helps clinicians see patterns of staining on the conjunctiva and cornea more clearly. It is most commonly used in dry eye and other ocular surface disease evaluations. It is applied as a drop or via a moistened dye strip in the clinic.

fluorescein is a fluorescent dye used to help clinicians see eye surface changes and certain blood vessels more clearly. It is commonly used in eye exams in optometry and ophthalmology clinics. In small amounts on the eye, it highlights scratches, dry spots, and contact lens fit patterns. When given into a vein for imaging, it can help map blood flow in the retina.

ocular surface staining is a clinical test that uses special dyes to highlight the surface of the eye. It helps clinicians see areas where the cornea or conjunctiva may be dry, irritated, or damaged. It is commonly performed during eye exams in optometry and ophthalmology clinics. It is often used when people have symptoms like burning, foreign-body sensation, or fluctuating vision.