Maharashtra HSC Ophthalmic Technician (Vocational) key terms

The clear, dome-shaped front window of the eye that bends incoming light and protects the iris and lens; it has no blood vessels and gets oxygen directly from air and tears.

Watery fluid produced by the ciliary body that fills the front chamber of the eye, nourishes the cornea and lens, and maintains intraocular pressure before draining at the angle.

The fluid pressure inside the eyeball, normally kept between about 10 and 21 mmHg by the balance of aqueous production and drainage; raised pressure damages the optic nerve.

The automatic change in shape of the crystalline lens, which becomes rounder for near vision and flatter for distance, so that images stay focused on the retina.

A transparent, elastic structure behind the iris that fine-tunes focus by changing curvature; it stiffens with age and becomes cloudy in cataract.

The light-sensitive inner layer of the eye containing rods and cones and the optic nerve fibres; it converts light into nerve signals sent to the brain.

The small central area of the retina packed with cone cells that gives sharp, detailed and colour vision; its centre, the fovea, provides the best acuity.

The bending of light rays as they pass from one medium to another, such as air into cornea, or the clinical measurement of a person's refractive error to prescribe lenses.

Short-sightedness in which parallel rays focus in front of the retina, usually because the eye is too long; distance vision is blurred and concave lenses correct it.

Long-sightedness in which parallel rays would focus behind the retina because the eye is too short or the cornea too flat; convex lenses correct it, and young patients may compensate by accommodation.

A refractive error in which the cornea or lens is unequally curved, so light focuses at different points; cylindrical lenses correct the blurred or distorted vision it causes.

Age-related loss of near focus caused by stiffening of the crystalline lens, appearing after about 40 years; reading glasses or bifocals restore clear near vision.

A lens thicker in the centre than at the edge that converges light rays; it is used to correct hyperopia and is described by its positive dioptric power.

A lens thinner in the centre than at the edge that diverges light rays; it is used to correct myopia and carries a negative dioptric power.

A lens curved in only one meridian, which bends light in that direction alone; it is prescribed with an axis to neutralise astigmatism.

The unit of lens power, equal to the reciprocal of focal length in metres; a 2-dioptre lens focuses parallel light at half a metre.

The meridian, expressed in degrees from 0 to 180, in which a cylindrical lens has no power; it is written on the prescription after the cylinder value.

An objective refraction technique in which the examiner sweeps a streak of light into the eye and observes the reflex movement to estimate the refractive error, especially in children.

A computerised instrument that measures refractive error and corneal curvature quickly by projecting light into the eye and analysing the reflected image; results are refined by subjective testing.

Measurement of the curvature and radius of the central cornea using reflected light, used to fit contact lenses, assess astigmatism and plan cataract surgery.

A binocular microscope combined with an adjustable slit of light that lets the examiner view the cornea, anterior chamber, lens and other front structures in optical section and at high magnification.

An instrument that measures intraocular pressure, either by gently flattening the cornea (applanation, as with Goldmann) or by non-contact air puff.

An instrument with a light and lenses used to examine the interior of the eye, particularly the optic disc, retinal vessels and macula, through a dilated pupil.

Clouding of the crystalline lens that gradually reduces vision and causes glare; the commonest cause of reversible blindness and treated by surgical removal with lens implantation.

A group of optic nerve disorders, often with raised intraocular pressure, that progressively narrow the visual field; early detection limits irreversible sight loss.

Damage to retinal blood vessels caused by long-standing diabetes, with microaneurysms, haemorrhages, exudates and new vessel growth that can lead to blindness if untreated.

Inflammation of the thin membrane covering the white of the eye and inner lids, causing redness, discharge and irritation; infectious forms spread easily, so hand hygiene is essential.

The sharpness of central vision, measured by identifying letters or symbols at a standard distance and recorded as a fraction such as 6/6 or 6/60.

A wall chart of letters arranged in rows of decreasing size, read at 6 metres to record distance visual acuity as the ratio of test distance to the distance at which a normal eye reads that row.

A small opaque disc with a central hole placed before the eye during acuity testing; if vision improves, the blur is refractive rather than caused by disease.

The total area a person can see while the eye is fixed straight ahead; it is mapped by perimetry to detect defects from glaucoma or neurological disease.

Testing that maps the extent and sensitivity of the visual field, using static or kinetic stimuli, to detect and monitor defects such as those caused by glaucoma.

An artificial lens implanted inside the eye, usually after cataract surgery, to replace the clouded natural lens and restore focus; its power is calculated before operation.

Measurement of eye length and corneal curvature before cataract surgery, used to calculate the power of the intraocular lens to be implanted.

A drug such as tropicamide or cyclopentolate that widens the pupil by relaxing the iris sphincter, allowing examination of the retina or cycloplegic refraction.

The central opening in the iris that controls how much light enters the eye; it narrows in bright light and widens in dim light or with mydriatic drops.

The coloured muscular ring in front of the lens whose sphincter and dilator muscles change pupil size and so regulate the amount of light reaching the retina.

A drop such as proparacaine or oxybuprocaine that numbs the surface of the eye for a short time, used before tonometry or minor procedures; it must never be given for home use.

Cleaning hands with soap and water or alcohol-based rub at the right moments, especially before and after patient contact, to prevent transmission of eye infections.

Routine infection-control measures applied to every patient, including hand hygiene, gloves, eye protection and safe sharps handling, because infection status is not always known.

Placing used needles and blades immediately into a puncture-resistant, labelled container without recapping, to prevent needlestick injury and blood-borne infection.

A patient's voluntary agreement to a test or procedure after receiving clear information about its purpose, benefits, risks and alternatives, documented in the record.

The duty to keep a patient's personal and clinical information private, sharing it only with those involved in care or as required by law.

The written or electronic file of a patient's history, examination findings, tests, treatment and consent, kept accurate, legible and secure as a legal document.

Delivery of eye-care advice, screening or follow-up by phone or video, useful for remote communities but limited by the need for hands-on examination and imaging.

Rapid testing of a population, such as schoolchildren, to identify those likely to have reduced vision and refer them for full examination; it is not a diagnosis.