Terms used in this guideline

Terms used in this guideline

Acceptable IOP Intraocular pressure (IOP) at or below the target level considered by the healthcare professional treating the person to be sufficiently low to minimise or arrest disease progression. See 'Target IOP'.

Adherence The extent to which the person's behaviour matches the prescriber's recommendations. Adherence emphasises the need for agreement and that the person is free to decide whether or not to adhere to the doctor's recommendation.

Blindness 1. Inability to see. 2. Absence or loss of sight severe enough for someone to be unable to perform any work for which eyesight is essential.

Conversion Worsening of suspected COAG or OHT with the development of visual field loss in keeping with optic nerve head appearance. To make this judgement the healthcare professional must know the eye's earlier clinical state.

Glaucoma A disease of the optic nerve with characteristic changes in the optic nerve head (optic disc) and typical defects in the visual field with or without raised IOP. See also types of glaucoma listed below.

Glaucoma, chronic open angle glaucoma (COAG) Glaucoma without evident secondary cause, which follows a chronic time course and occurs in the presence of an open anterior chamber angle (the trabecular meshwork is visible on gonioscopy). In this guideline the term COAG is used regardless of the level of IOP and has been extended to include COAG associated with pseudoexfoliation and pigment dispersion.

Glaucoma (COAG); early, moderate and advanced The definitions are based on the Hodapp classification of visual field loss for the stages of glaucoma (see section 1.8.6 of the full guideline). These can be summarised approximately in terms of mean defect (MD) as follows: early, MD greater than –6 dB; moderate, MD –6 dB to greater than –12 dB; advanced, MD –12 dB to greater than –20 dB. Severe visual impairment (blindness) is defined as MD –20 dB or worse.

Glaucoma, suspected When, regardless of the level of the IOP, the optic nerve head (optic disc) and/or visual field show changes that suggest possible glaucomatous damage.

Gonioscope Mirrored contact lens (goniolens), used with slit lamp biomicroscopy, or a contact prism lens (gonioprism) which enables observation of the anterior chamber angle.

Gonioscopy Examination of the anterior chamber angle using a gonioscope to observe angle structures and estimate depth of angle.

Healthcare professional For the purposes of this guideline the term 'healthcare professional' refers to a trained individual involved in glaucoma‑related care including: ophthalmologists, optometrists, orthoptists, pharmacists, nurses and GPs.

Intraocular pressure (IOP) The internal pressure of the fluid contained within the eye.

Laser trabeculoplasty A surgical procedure to deliver a series of laser burns to the trabecular meshwork to improve the outflow of aqueous humour in open angle glaucoma.

Ocular hypertension (OHT) Consistently or recurrently elevated IOP (greater than 21 mmHg) in the absence of clinical evidence of optic nerve damage or visual field defect.

Perimetry The systematic measurement of visual field function using different types and intensities of stimuli.

Progression The worsening of COAG as clinically judged by the healthcare professional caring for the person on the basis of the assessment of visual field loss and optic nerve head appearance. To make this judgement the healthcare professional must know the eye's earlier clinical state.

Target IOP A dynamic, clinical judgement about what level of IOP is considered by the healthcare professional treating the person to be sufficiently low to minimise or arrest disease progression or onset and avoid disability from sight loss within a person's expected lifetime.

Tonometry A test to measure IOP using an instrument called a tonometer.

Trabeculectomy A surgical procedure that lowers IOP by creating a fistula, which allows aqueous outflow from the anterior chamber of the eye to the subtenon space.

Van Herick's peripheral anterior chamber depth assessment A slit lamp estimation of the depth of the peripheral anterior chamber of the eye; it is used as a proxy measure for judging whether the anterior chamber angle is open.

Visual field The area which can be seen when the eye is directed forward, including both central and peripheral vision.

  • National Institute for Health and Care Excellence (NICE)