Maharashtra HSC Ophthalmic Technician (Vocational) cheat sheet

The fibrous tunic comprises the sclera (opaque, five-sixths) and cornea (transparent, one-sixth); the uveal tract comprises iris, ciliary body and choroid.

Tear film has three layers: lipid from meibomian glands, aqueous from lacrimal and accessory glands, and mucin from conjunctival goblet cells.

Aqueous humour is produced by the ciliary epithelium, flows through the pupil, and drains mainly via the trabecular meshwork into Schlemm canal and episcleral veins.

Normal adult intraocular pressure is approximately 10-21 mmHg; the reference range is a statistical guide, not a diagnostic threshold on its own.

The retina has ten layers; photoreceptors (rods for dim light, cones for colour and acuity) lie external to the bipolar and ganglion cells, so light traverses the inner retina first.

The macula lies temporal to the optic disc and contains the fovea centralis, the area of highest cone density and sharpest vision.

Six extraocular muscles: four recti (superior, inferior, medial, lateral) and two obliques; the superior oblique is supplied by the trochlear nerve (CN IV), lateral rectus by abducens (CN VI).

The optic nerve head has no photoreceptors, producing the physiological blind spot about 15 degrees temporal to fixation.

Cornea is avascular and derives oxygen mainly from air and limbal vessels; its transparency depends on regular collagen spacing and relative deturgescence.

Dioptric power of a surface: F = (n2 - n1)/r, with r in metres; a converging surface has positive power, a diverging surface negative power.

Thin lens combination in contact: F = F1 + F2; for lenses separated by distance d, F = F1 + F2 - d(F1)(F2).

Snell law: n1 sin i = n2 sin r; light bending toward the normal indicates entry into a denser medium.

Total internal reflection occurs when light travels from denser to rarer medium and the incident angle exceeds the critical angle, where sin c = n2/n1.

Reduced eye treats the eye as a single refracting surface with power about 60 D; the Gullstrand schematic eye gives more precise cardinal points.

Prism dioptre: 1 prism dioptre deviates a ray by 1 cm at 1 m; prism base is oriented toward the apex of the deviation to be corrected.

Magnification of a simple magnifier: M = 1 + D/F (D = 25 cm) for the image at infinity convention; a compound microscope uses objective and eyepiece powers multiplied.

Spherical aberration, coma, astigmatism, curvature of field and distortion are the five Seidel aberrations; chromatic aberration arises from dispersion.

Myopia is corrected with a concave (minus) lens; hyperopia with a convex (plus) lens; astigmatism with a cylindrical lens at the axis of the flattest meridian.

Emmetropia means parallel rays focus on the retina at rest; ametropia is any refractive error; presbyopia is loss of accommodation with age, not a refractive error of the globe.

Retinoscopy: neutralise the reflex with lenses; working distance lens (e.g. +1.50 D for 66 cm) is subtracted from the neutralising lens to obtain the net refraction.

Subjective refraction uses the duochrome test (red-green) to avoid over-minus; with best sphere, red and green targets should appear equally clear.

Spherical equivalent = sphere + half the cylinder; used for contact lens selection and for estimating refractive error in some screening contexts.

Keratometry measures anterior corneal curvature and derives corneal power; average corneal power is about 43-44 D; it is essential before contact lens fitting.

Jackson cross-cylinder flips are used to refine cylinder axis and power; the patient reports which of two positions is clearer.

Anisometropia is a difference in refractive error between eyes; significant anisometropia in children risks amblyopia and requires prompt referral.

Vertex distance matters for powers above about 4 D; a plus lens moved away from the eye increases effective power.

Slit lamp: illumination and observation arms share a pivot; magnification is changed by the drum; the cobalt blue filter is used with fluorescein.

Applanation tonometry (Goldmann) requires a calibrated biprism, fluorescein-stained tear film, and slit beam at about 60 degrees; IOP reading is multiplied by 10.

Direct ophthalmoscope gives an upright virtual image magnified about 15 times; indirect ophthalmoscopy with a condensing lens gives an inverted, reversed, real image.

Keratometer, autorefractor and lensmeter require daily calibration checks; a lensmeter verifies spectacle power, axis and optical centre.

Non-contact (air-puff) tonometer reduces cross-infection risk but is less accurate in irregular corneas and after refractive surgery.

Perimetry (Humphrey) requires reliable fixation, appropriate near correction, and monitoring of fixation losses, false positives and false negatives.

A-scan biometry measures axial length for intraocular lens power calculation; B-scan ultrasound is used when media are opaque.

Handle optical surfaces only by the mount; clean lenses with lint-free tissue and approved solution; never use dry abrasive cloth on coated optics.

Cataract is opacification of the crystalline lens; the only definitive treatment is surgical removal with intraocular lens implantation.

Open-angle glaucoma is usually asymptomatic until advanced; angle-closure presents with severe pain, halos, mid-dilated pupil and a shallow anterior chamber.

Diabetic retinopathy: non-proliferative shows microaneurysms, dot-blot haemorrhages, hard exudates; proliferative shows neovascularisation and risk of vitreous haemorrhage.

Age-related macular degeneration: dry type shows drusen and geographic atrophy; wet type shows choroidal neovascular membrane and requires urgent referral.

Trachoma is caused by Chlamydia trachomatis serovars A-C; repeated infection causes trichiasis, entropion and corneal scarring (the SAFE strategy addresses it).

Bacterial conjunctivitis presents with purulent discharge and papillary reaction; viral with watery discharge and follicles; allergic with itching and cobblestone papillae.

Corneal ulcer is a sight-threatening emergency; contact lens wearers with pain, photophobia and reduced vision require same-day review.

Retinopathy of prematurity affects premature infants; screening timing depends on birth weight and gestational age, and plus disease requires urgent treatment.

Snellen acuity is recorded as the distance at which the chart is used over the distance at which a normal eye reads that line (e.g. 6/6); it is not a percentage.

Test distance for standard Snellen is 6 m; for near vision use a reduced chart at 33-40 cm with appropriate reading correction.

Pinhole improves acuity in uncorrected refractive error but not in media opacity or retinal disease; it is a quick discrimination test.

Colour vision: Ishihara plates screen red-green defects; Farnsworth-Munsell arranges hues to grade severity.

Confrontation testing and Amsler grid are bedside tests; Amsler grid monitors metamorphopsia in macular disease.

Cover test detects manifest (tropia) and latent (phoria) deviation; alternate cover test reveals the total deviation.

Fluorescein staining with cobalt blue light detects corneal epithelial defects; Seidel test identifies aqueous leak from a perforation.

Schirmer test with anaesthesia measures basal tear secretion; less than 5 mm in 5 minutes suggests dry eye.

Visual field testing requires the patient to maintain central fixation and respond to stimuli; reliability indices must be checked before interpretation.

Before any procedure, verify patient identity, the eye to be treated, consent and allergy status; mark the site where policy requires.

Instil drops into the lower fornix with the patient looking up; avoid touching the eye or lashes with the bottle tip to prevent contamination.

Punctal occlusion for about one to two minutes after instillation reduces systemic absorption of drugs such as beta-blockers and atropine.

During minor surgery, maintain the sterile field, monitor the patient, and keep instrument and suture counts according to local protocol.

Intravitreal injection preparation uses povidone-iodine antisepsis, a lid speculum, and a no-touch technique; the assistant prepares and confirms the correct drug and dose.

Removal of a corneal foreign body requires magnification, good illumination, and documentation of depth; rust rings may need a burr.

After any procedure, record the agent used, eye, time, patient response and any adverse event in the clinical record.

When assisting with a patient who faints or has a vasovagal reaction, lie the patient flat, protect the airway, and call for clinical help.

Tropicamide and cyclopentolate are short-acting mydriatics/cycloplegics; atropine is long-acting and can cause systemic anticholinergic effects.

Phenylephrine dilates without cycloplegia; it is used for fundus examination but can raise blood pressure in susceptible patients.

Timolol, a non-selective beta-blocker, is contraindicated in asthma and heart block; punctal occlusion reduces systemic absorption.

Pilocarpine is a cholinergic miotic used in glaucoma and to reverse cycloplegia; it causes brow ache and miosis.

Topical anaesthetics (proxymetacaine, oxybuprocaine) are for procedures only; chronic use causes corneal epithelial toxicity and should be avoided.

Fluorescein is a diagnostic dye; it stains epithelial defects and is used with cobalt blue light and for applanation tonometry.

Antibiotic drops are prescribed for bacterial infection; viral conjunctivitis does not respond to antibiotics and steroid use requires ophthalmic supervision.

Record drug name, concentration, eye, time and any adverse reaction; check for allergies and expiry before instillation.

Hand hygiene is the single most effective measure; use alcohol-based rub for clean hands and soap and water when visibly soiled.

Sterilisation destroys all micro-organisms including spores; disinfection reduces but does not eliminate them. Autoclave cycles must be monitored and logged.

High-level disinfection is required for tonometer prisms and contact lenses used in trials; single-use items must never be reused.

Standard precautions treat all blood and body fluids as potentially infectious; gloves do not replace hand hygiene.

Sharps must be disposed of immediately in puncture-resistant containers; never recap a needle by hand.

Applanation tonometry carries a theoretical risk of prion transmission; follow local decontamination policy and use disposable tips where available.

Spill management: contain, clean with detergent, then disinfect with an appropriate agent such as sodium hypochlorite solution according to local policy.

Patient safety includes checking for falls risk, correct identification, and reporting incidents and near misses through the local system.

Cataract, uncorrected refractive error, glaucoma, diabetic retinopathy and childhood blindness are priority conditions in national eye health programmes.

The National Programme for Control of Blindness and Visual Impairment in India uses a district-level approach, with vision centres linked to higher facilities.

School vision screening aims to detect refractive error and amblyopia risk early; children with reduced acuity need refraction and follow-up, not just spectacles on site.

Vitamin A deficiency causes xerophthalmia and night blindness; supplementation and dietary education are preventive measures.

Diabetic retinopathy screening should be offered to all known diabetics; control of blood sugar and blood pressure reduces progression.

Glaucoma screening is not suited to simple IOP measurement alone; optic disc and visual field assessment are required for diagnosis.

Community awareness messages should be accurate, culturally appropriate and in the local language; avoid promising cure where only control is possible.

Referral pathways need defined criteria and feedback loops so that screened patients actually reach treatment and outcomes are recorded.

Confidentiality: patient information is shared only for direct care or with consent, or where law requires disclosure.

Informed consent requires capacity, adequate information about risks and alternatives, and a voluntary decision; it must be documented.

Scope of practice: an ophthalmic technician performs tasks within training and delegated authority and refers beyond that scope.

Records must be accurate, legible, contemporaneous, attributable and complete; late entries are marked as such and never altered retrospectively.

Objectivity: record what is observed and measured, not opinions about the patient; use neutral, factual language.

Communication: use plain language, confirm understanding, involve interpreters where needed, and respect patient dignity and privacy.

Report errors and near misses honestly; a duty of candour supports patient safety and professional accountability.

Avoid conflicts of interest and never accept inducements that could influence referral or purchasing decisions.