Accommodation:  The process by which the eye increases optical power to focus on a near object.

Accommodative Lag:  The visual state in which the eyes focus beyond the target of interest.  This can induce hyperopic defocus.

Adnexa:  The appendages of an organ such as the eyelids and lacrimal glands of the eye.

Ametropia:  The term used to describe a variety of refractive errors including myopia, hyperopia, astigmatism and their possible combinations.

Anisometropia:  A condition in which the refractive power of one eye differs from that of the other.

Anterior Chamber:  The fluid-filled space in the eye bounded anteriorly by the cornea and posteriorly by the iris.

Anterior Chamber Angle:  Interior angle of the junction of the front surface of the iris and back surface of the cornea, where aqueous fluid is filtered out of the eye.

Astigmatism:  A refractive error in which light rays fail to come to a single focus on the retina due to unequal curvature of one or more refractive surfaces of the eye, usually in opposing meridians.

Axial Length:  The distance, usually expressed in millimetres, between the anterior and posterior poles of the eye.  Increase in axial length results in a change of refraction towards myopia or increase in myopia.

Best Vision Sphere:  The most positive (or least negative) spherical lens that provides the best visual acuity (not necessarily equal to the spherical equivalent refractive error).

Capsulorhexis:  A surgical technique in which a continuous circular opening is made in the anterior capsule of the crystalline lens to allow expression of the lens nucleus during cataract surgery.

Conjunctiva:  The mucous membrane which lines the inner surface of the eyelids and anterior sclera.

Contrast Sensitivity:  A measure of the ability to discern between images at different levels of luminance contrast. This is usually described as the reciprocal of the minimum perceptible contrast.

Cornea:  The transparent anterior surface of the eyeball, contributing significantly to the eye’s refractive power.

Corneal Staining:  Corneal epithelial cell damage, visibly detectable on the insertion of fluorescein, as a result of mechanical, toxic, hypoxic (reduced oxygen), infectious or inflammatory events.  

Defocus Curve:  An assessment technique used to simulate the range of distances over which a subject has useful vision. 

Digital Eyestrain:  A condition characterized by visual disturbance and/or ocular discomfort related to the use of digital devices and resulting from a range of stresses on the ocular system including glare, defocus, accommodation, fixation disparity, dryness, fatigue and discomfort.

Diffractive Intraocular Lenses: These devices divide light between two foci (typically distance and near) through the use of different diffractive orders. When the diffractive structure covers the entire lens surface, an equal amount of light is directed between the distance and near foci at all pupil diameters.

Dysphotopsia:  A disturbance of vision including light phenomena such as haloes; i.e. the subjective perception of a bright ring around a light source.

Early Treatment Diabetic Retinopathy Study (ETDRS) ChartA test chart employing the logMAR method of visual acuity (VA) measurement, consisting of five letters per line all of equal spacing.

Emmetropia:  The state of vision for an eye that is neither myopic nor hyperopic and, therefore, does not require correction of ametropia.

Emmetropization:  The physiological process by which an eye develops towards emmetropia. 

Fundus:  The inner lining of the eyeball, including the retina, optic nerve head, macula and fovea.

Gonioscopy:  Anexamination using a hand held lens to view the anterior chamber angle of the eye with particular relevance to glaucoma.

High Myopia:  Myopia in which the spherical equivalent refractive error of an eye is ≤ -6.00 D.

Hyperopia:  A condition where the focal rays of an object reach the retina before they converge into a focused image (also known as far-sightedness).

Hyperopic Defocus:  Any optical aberration in the eye where the focal plane lies behind the retina.  May occur naturally or be induced with lenses or by fatigue.

Intraocular Lens (IOL):  A small artificial lens, usually made of silicone or acrylic, inserted into the eye following extraction of the opaque crystalline lens during cataract surgery. IOLs are classified as Class III medical devices.

Intraocular Pressure (IOP):  The pressure created by continual renewal of aqueous fluid within the eye.

Keratometry:  Measurement of the front surface curvature of the eye. Usually limited to the central 3 mm of the cornea.

K-readings:  The measurements obtained from keratometry, usually taken in the flattest and steepest meridians of the cornea; expressed in either millimetres (mm) or dioptres (D).

Lid Wiper: Thin portion of the marginal conjunctiva of the upper eyelid that comes into contact with the anterior eye during blinking.

Landolt-C Chart: A chart for measuring visual acuity (VA) using the letter ‘C’ in four different orientations.

Limbus:  The transition zone between the white of the eye, the sclera, and the cornea.

LogMAR Chart:  A chart for testing visual acuity (VA), consisting of five letters per line and where each line represents a logarithmic progression in size of letters.

Meibomian Glands:  Sebacious glandslocated in the upper and lower eyelids which secrete the outermost, oily layer of the pre-corneal tear film.

Monovision:  Simultaneous correction of both distance and near vision by the prescribing of a distance lens in one eye (usually the dominant eye) and a near lens in the other.

Multi-zone Intraocular Lenses: These devices focus light from distant and near objects typically using two (or more) refractive powers, usually incorporated into circular or annular (ring-shaped) zones.

Myopia:  A condition where the focus of an object falls short of the retina, resulting in a blurred and imperfect image (also known as near-sightedness). The spherical equivalent objective refractive error is ≤ -0.50 D in either eye.

Myopia Control:  The term given to the various methods used to reduce or arrest the progression of myopia.

Multifocal Lens:  A design of lens providing focus at multiple working distances, typically near and far, but also mid distance.  Available in intraocular lens implant, spectacle and contact lens correction formats.

Orthokeratology (Ortho-K):  A method of vision correction that uses overnight wear of rigid gas permeable contact lenses to temporarily reshape the central cornea.

Phacoemulsification:  A surgical procedure in which the lens nucleus is fragmented and removed during cataract surgery using an ultrasonic probe.

Phakic IOL:  A small artificial lens implanted into the eye to correct for ametropia without requiring removal of the crystalline lens.

Phoria:  Misalignment of the eyes in the absence of a binocular fusion stimulus (exophoria = divergent, esophoria = convergent).

Posterior Chamber: The gel-filled space in the eye bounded anteriorly by the iris and posteriorly by the retina.

Pre-myopia: A refractive state of ≤ +0.75 D and > -0.50 D in children where a combination of baseline refraction, age, and other quantifiable risk factors provide a sufficient likelihood of the future development of myopia to merit preventative interventions.

Presbyopia: A refractive disorder where the accommodative ability of the eye decreases due to physiological ageing of the crystalline lens, resulting in an inability to focus adequately on near objects.

Sclera:  The tough, white, collagenous outer layer of the eye.

Simultaneous Vision Corrections: Optical corrections (either contact lenses or intraocular lenses) capable of providing distance, intermediate and near vision within the confines of the pupil aperture, allowing light rays from distance and near objects to be simultaneously imaged onto the retina.

Snellen Chart:  A chart for measuring visual acuity, usually consisting of letters, or numbers, printed in lines of decreasing size which a patient is asked to read or identify at a fixed distance.

Spherical Equivalent Refractive Error: A single measurement of an eye’s refractive error, calculated as the spherical component plus half of the cylindrical component.

Uvea: The pigmented vascular middle layer of the eye, consisting of the iris, choroid, and ciliary body.

Visual Acuity (VA):  A measure of the eye’s ability to resolve letters or numbers at a given distance according to a fixed standard.



Papillary Conjunctivitis:  Inflammation of conjunctival membrane lining the inner of the eyelid, characterised by large papillae as a result of sensitisation to antigenic material.

Causality:  An assessment of the relationship between an adverse event and the test article using the following categories: Not related, Unlikely related, Possibly related, Related.

Corneal Edema:  Fluid in stromal layer of cornea ± epithelial edema (bullae or microbullae).

Cumulative Adverse Event:  The total number of adverse events which have occurred at any time during an investigation.

Endophthalmitis:  Inflammation of tissues inside the eyeball.  Can be sterile or from intraocular infection.

Hyphema: Blood in the anterior chamber, present over a period of time.

Hypopyon:  Accumulation of leucocytes in the anterior chamber.

Infiltrative Event (IE):   A clinical finding characterised by the presence of one or more inflammatory cells in the cornea 

Iritis: Inflammation of the iris, causing pain, tearing, blurred vision, small pupil (miosis), and a red congested eye.  Evidenced by flare and/or cells in the anterior chamber, with or without keratic precipitates.

Keratoectasia:  Bulging forward of the cornea.

Lens Dislocation:  Displacement of the crystalline lens from its intended place.

Macular Edema:  Swelling of macular tissue from excess fluid accumulation. 

Microbial Keratitis (MK):  A rare, potentially sight-threatening microbial infection of the cornea associated with contact lens wear, characterised by progressive excavation of the corneal epithelium and necrosis of the underlying tissue.

Polymegethism:  An unusually large variation in the size of corneal endothelial cells.

Posterior Capsular Opacification (PCO): A complication occurring some time after cataract surgery involving opacification of the residual crystalline lens capsule and resulting in blurred, hazy vision. PCI is easily treated with an outpatient laser procedure.

Persistent Adverse Event:  An adverse event which is present at long-term follow-up (or at the one-year postoperative visit in IOL studies).

Pupillary Block:  Blockage of aqueous flow through the pupil, from the posterior chamber into the anterior chamber, caused by tight contact between the pupillary margin of the iris and the lens (or vitreous face only if aphakic, unless the IOL slips into the vitreous).

Raised IOP Requiring Treatment: Persistent elevation of intraocular pressure requiring medical and/or surgical treatment.

Retinal Detachment: Separation of retina from the underlying pigment epithelium associated with retinal hole formation (rhegmatogenous).

Severity Assessment:   A qualitative assessment of the degree of intensity of an adverse event as determined by the investigator according to the following scale: mild, moderate, severe. 

Superior Epithelial Arcuate Lesion (SEAL):  A mechanical injury characterised by an arc-like break in the epithelium of the superior cornea and associated with contact lens wear.

Superficial Punctate Keratitis (SPK):  Superficial erosion of the corneal epithelial surface, which typically stains on the insertion of fluorescein diagnostic dye into the eye’s tear film. 

Solution Induced Corneal Staining (SICS):  A form of diffuse corneal staining, typically observable over a minimum four-fifths of the corneal surface area, induced with certain contact lens/contact lens solution combinations.

Uveitis:  Inflammation of the uveal tract, i.e. iris, ciliary body, and choroid.



Adverse Event (AE):  Any unfavourable and unintended sign (including an abnormal laboratory finding), symptom, or disease temporally associated with the use of an investigational product, whether or not related to the investigational product

Audit:  A systematic and independent examination of trial related activities and documents to determine whether the evaluated trial related activities were conducted, and the data were recorded, analyzed and accurately reported according to the protocol, sponsor's standard operating procedures (SOPs), Good Clinical Practice (GCP), and the applicable regulatory requirement(s).

Audit Trail:  A process that captures details such as additions, deletions, or alterations of information in an electronic record without obliterating the original record.   

Case Report Form (CRF):  A printed, optical, or electronic document designed to record all of the protocol required information to be reported to the sponsor on each trial subject.

Chief Investigator (CI): The overall lead researcher for a research project (outside the UK the term Coordinating Investigator or Investigator may be used) and are responsible for the overall conduct of a research project.

Clinical Trial/Study/Investigation:  Any investigation in human subjects intended to discover or verify the clinical effects of an investigational product(s), and/or to identify any adverse reactions to an investigational product(s) with the object of ascertaining its safety and/or efficacy.

Clinical Trial/Study Report:  A written description of a trial/study of any therapeutic, prophylactic, or diagnostic agent conducted in human subjects, in which the clinical and statistical description, presentations, and analyses are fully integrated into a single report.

Contract Research Organization (CRO):  An organization (commercial, academic, or other) contracted by the sponsor to perform one or more of a sponsor's trial-related duties and functions.

Coordinating Committee:  A committee that a sponsor may organize to coordinate the conduct of a multicentre trial.

Coordinating Investigator: An investigator assigned the responsibility for the coordination of investigators at different centres participating in a multicentre trial.

Corrective Action: Action(s) that will be taken to eliminate a detected nonconformance.

Designee: Person or persons who are qualified and authorized (by virtue of job responsibility or delegation) to perform a task or responsibility on another person’s behalf (i.e., Sub-Investigator).

Electronic Medical Records (EMR): An EMR includes information about a patient's health history, such as diagnoses, medicines, tests, allergies, immunizations, and treatment plans.

Essential Documents:  Documents which individually and collectively permit evaluation of the conduct of a study and the quality of the data produced. These documents serve to demonstrate the compliance of the Investigator, Sponsor, and Monitor with the standards of GCP and with applicable regulatory requirements.

Good Clinical Practice (GCP):  A standard for the design, conduct, performance, monitoring, auditing, recording, analyses, and reporting of clinical trials that provides assurance that the data and reported results are credible and accurate, and that the rights, integrity, and confidentiality of trial subjects are protected.

ICH Guidelines:  International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH) - Guidelines for good clinical practice (GCP).

Independent Ethics Committee (IEC):  An independent body (a review board or a committee, institutional, regional, national, or supranational), constituted of medical professionals and non-medical members, whose responsibility it is to ensure the protection of the rights, safety and well-being of human subjects involved in a trial and to provide public assurance of that protection, by, among other things, reviewing and approving / providing favourable opinion on, the trial protocol, the suitability of the investigator(s), facilities, and the methods and material to be used in obtaining and documenting informed consent of the trial subjects.

Informed Consent:  A process by which a subject voluntarily confirms his or her willingness to participate in a particular trial, after having been informed of all aspects of the trial that are relevant to the subject's decision to participate. Informed consent is documented by means of a written, signed and dated informed consent form.

Institution (Medical):  Any public or private entity or agency or medical, dental or optometric facility where clinical trials are conducted.

Institutional Review Board (IRB):  An independent body constituted of medical, scientific, and non-scientific members, whose responsibility is to ensure the protection of the rights, safety and well-being of human subjects involved in a trial by, among other things, reviewing, approving, and providing continuing review of trial protocol and amendments and of the methods and material to be used in obtaining and documenting informed consent of the trial subjects.

Interim Clinical Trial/Study Report:  A report of intermediate results and their evaluation based on analyses performed during the course of a trial.

Investigational Product:  A product being tested or used as a reference in a clinical trial, including a product with a marketing authorization when used or assembled (e.g. packaged) in a way different from the approved form, or when used for an unapproved indication, or when used to gain further information about an approved use.

Investigator:  A person responsible for the conduct of the clinical trial at a trial site. If a trial is conducted by a team of individuals at a trial site, the investigator is the responsible leader of the team and may be called the principal investigator.

ISO 14155:2011 Clinical investigation of medical devices for human subjects - Good clinical practice:  The International Standard addressing GCP for the design, conduct, recording and reporting of clinical investigations carried out in human subjects to assess the safety or performance of medical devices for regulatory purposes. 

Clinical Investigator's Brochure:  A compilation of the clinical and nonclinical data on the investigational product(s) which is relevant to the study of the investigational product(s) in human subjects.

Legally Acceptable Representative:  An individual or other body authorized under applicable law to consent, on behalf of a prospective subject, to the subject's participation in the clinical trial.

Medical Device:  Any instrument, apparatus, appliance, material or other article, whether used alone or in combination intended by the manufacturer to be used for human beings for the purpose of:
• diagnosis, prevention, monitoring, treatment or alleviation of disease
• diagnosis, monitoring, treatment, alleviation of or compensation for an injury or handicap
• investigation, replacement or modification of the anatomy or of the physiological process
• control of conception and which does not achieve its principal intended action in or on the human body by pharmacological, immunological or metabolic means, but which may be assisted in its function by such means.

Monitoring:  The act of overseeing the progress of a clinical trial, and of ensuring that it is conducted, recorded, and reported in accordance with the protocol, Standard Operating Procedures (SOPs), Good Clinical Practice (GCP), and the applicable regulatory requirement(s).

Monitoring Report:  A written report from the monitor to the sponsor after each site visit and/or other trial-related communication according to the sponsor’s SOPs.

Multicentre Trial:  A clinical trial conducted according to a single protocol but at more than one site, and therefore, carried out by more than one investigator.

Patient-Reported Outcome (PRO): Information coming directly from patients or subjects through self-completed questionnaires or text messages or interviews responses about their perceptions, symptoms, satisfaction with treatment, adherence to prescribed regimens.

PROs include outcomes recorded by interviewers transcribing the views expressed by the patient, but the term does not apply to outcomes recorded by observers who rely on their own judgment. A PRO is usually a subjective assessment of feeling or function distinguished from a self-reported objective measurement such as body weight.

Per-Protocol: The subset of subjects who complied with the protocol sufficiently to ensure that these data would be likely to exhibit the effects of treatment according to the underlying scientific model.[ICH E9]

Protocol:  A document that describes the objective(s), design, methodology, statistical considerations, and organization of a trial. The protocol usually also gives the background and rationale for the trial, but these could be provided in other protocol referenced documents. Throughout the ICH GCP Guideline the term protocol refers to protocol and protocol amendments.

Protocol Amendment:  A written description of a change to or formal clarification of a protocol.

Protocol Deviation: Unplanned excursion from the protocol that occurs during the conduct of a study, which may or may not affect the safety of the subject or the integrity of clinical data.

Quality Assurance (QA):  All those planned and systematic actions that are established to ensure that the trial is performed and the data are generated, documented (recorded), and reported in compliance with Good Clinical Practice (GCP) and the applicable regulatory requirement(s).

Quality Control (QC):  The operational techniques and activities undertaken within the quality assurance system to verify that the requirements for quality of the trial-related activities have been fulfilled.

Query:  A request for clarification on a data item; specifically a request from a sponsor or sponsor’s representative to an investigator to resolve an error or inconsistency discovered during data review.

Randomization:  The process of assigning trial subjects to treatment or control groups using an element of chance to determine the assignments in order to reduce bias.

Regulatory Authorities:  Bodies having the power to regulate. In the ICH GCP guideline the expression Regulatory Authorities includes the authorities that review submitted clinical data and those that conduct inspections. These bodies are sometimes referred to as competent authorities.

Risk Based Monitoring: The process of ensuring the quality of clinical trials by identifying, assessing, monitoring and mitigating the risks that could affect the quality or safety of a study.

Screen Failure: Potential subject who did not meet one or more entry criteria required for participation in a trial.

Serious Adverse Event (SAE) or Serious Adverse Drug Reaction (Serious ADR):  Any untoward medical occurrence that at any dose:
• results in death or is life-threatening
• requires in-patient hospitalization or prolongation of existing hospitalization
• results in persistent or significant disability/incapacity (e.g. sight-loss)
• is a congenital anomaly/birth defect

Source Documentation:  Original documents, data, and records (e.g., hospital records, clinical and office charts, laboratory notes, memoranda, subjects' diaries or evaluation checklists, recorded data from automated instruments, copies or transcriptions certified after verification as being accurate copies, subject files, and records kept at the laboratories and at medico-technical departments involved in the clinical trial).

Sponsor:  An individual, company, institution, or organization which takes responsibility for the initiation, management, and/or financing of a clinical trial.

Standard Operating Procedures (SOPs):  Detailed, written instructions to achieve uniformity of the performance of a specific function.

Subinvestigator:  Any individual member of the clinical trial team designated and supervised by the investigator at a trial site to perform critical trial-related procedures and/or to make important trial-related decisions (e.g., associates, residents, research fellows).

Subject/Trial Subject:  An individual who participates in a clinical trial, either as a recipient of the investigational product(s) or as a control.

Trial Master File: The repository for all study-related essential documents collected before, during and after a trial, and maintained by the sponsor. These are documents collected from investigational sites as well as provided by the sponsor, which are filed in a systematic fashion in accordance with the structures outlined in a TMF procedure.

Trial Site:  The location(s) where trial-related activities are actually conducted.

Vulnerable Subjects:  Individuals whose willingness to volunteer in a clinical trial may be unduly influenced by the expectation, whether justified or not, of benefits associated with participation, or of a retaliatory response from senior members of a hierarchy in case of refusal to participate. Examples are members of a group with a hierarchical structure, such as medical, dental, and nursing students, subordinate personnel, employees of the pharmaceutical industry, members of the armed forces, and persons kept in detention. Other vulnerable subjects include unemployed or impoverished persons, minors, and those incapable of giving consent.



Attrition Bias:   Systematic differences in outcome data between groups either in the amount or nature of incomplete data.

Bias:  The introduction of systematic errors from the truth.

Contralateral Eye Design:  Ocular clinical study in which the two eyes receive different treatments.

Controlled Clinical Study:  A clinical study comparing the safety and effectiveness of the investigational device with a control.

Cross-over Design:   A study in which subjects receive a sequence of different interventions.  In the simplest cross-over design study, each participant receives either the investigational device or the control in the first period, and the other in the succeeding period,

Efficacy: The performance of an intervention or treatment under ideal and controlled conditions.

Effectiveness: The performance of an intervention or treatment under ‘real-world’ conditions.

Exploratory Stage:  Clinical development stage that includes initial development, evaluation, first-in- human and other feasibility studies.

Feasibility Study:   A preliminary clinical study to see if a larger pivotal study is practical and to refine the study protocol for the pivotal study.  A feasibility study is sometimes also called a pilot study.

Historical Control:   A control based on a group of subjects who were observed at some time in the past.

Incidence: The proportion of new cases of a disease over a particular period of time.

Masking/Blinding:  A procedure in which one or more parties to the trial are kept unaware of the treatment assignment(s). Single-masking usually refers to the subjects being unaware, and double-masking usually refers to the subjects, investigator(s), monitor, and, in some cases, data analysts being unaware of the treatment assignment(s).

Meta-analysis:  A statistical synthesis of the data from separate but similar (i.e., comparable) studies, leading to a quantitative summary of the pooled results.

Non-inferiority study:   Study designed to demonstrate that the safety or effectiveness of an investigational device is not worse than the comparator by more than a specified margin.

Observational Study:  Study that draws inferences about the possible effect of an intervention on subjects, but the investigator has not assigned subjects into treatment groups.

Open-label Design:   A clinical study in which the participant, health care professional, and others know which intervention or diagnostic test under study is being given (see also Non-Masked Study)

Paired Design:   The application of two or more interventions or diagnostic tests at the same point in time to the same subjects or subject specimens.  This design may be not appropriate if the interventions or test interfere with each other.

Parallel Group Design:   An (unpaired) design in which each study subject or subject specimen is assigned only one of several interventions or diagnostic tests being studied.

Performance Goal:   A numerical value (point estimate) that is considered sufficient for use as a comparison for a safety and/or effectiveness endpoint.

Pivotal Study:   A definitive clinical study in which evidence is gathered to support the safety and effectiveness evaluation of a medical device for its intended use.

Placebo Control Study:   A comparative investigation in which the results of the use of a particular treatment are compared with those from an ineffective treatment under otherwise similar conditions.

Prevalence:  The proportion of a population that possesses a particular trait or disease at a given time.  Often confused with incidence.

Registry Study:  An observational study, usually post-marketing, assessing the performance of a device in normal usage.

Selection Bias:   A type of bias caused by an error in the way subjects are assigned to groups in a clinical study, for instance, due to poor randomisation.

Stratification:   The division of a population into mutually exclusive and exhaustive sub-populations (called strata), which are thought to be more homogeneous, with respect to the characteristics investigated, than the total population.

Study Effect:    Errors in study outcomes due to the subjects behaving differently due to being measured in a study or due to their receiving better or more attentive care in a study. 

Study Endpoint:   A primary or secondary outcome used to judge the effectiveness of an investigation.

Superiority Study:  Study designed to demonstrate that the safety or effectiveness of the investigational device is superior to that of the comparator.

Temporal Bias:   Bias resulting from comparing results separated by a significant time interval, for example, using a historical control group that does not reflect current practice and may include a different subject population and/or outcomes than the contemporary study.