20.2 Medical Terminology, Anatomy, and Physiology

20.2 Medical Terminology, Anatomy, and Physiology

Medical terminology is built from three parts: a prefix (beginning, often a location or number), a root word (the body part or meaning), and a suffix (the ending, often a condition or procedure). Decode in this order: suffix, then prefix, then root. Blepharitis = blephar- (eyelid) + -itis (inflammation) = inflammation of the eyelid.

High-yield word parts

Prefixes worth memorizing

• hyper- (above/excess) vs hypo- (below/deficient): hypertension vs hypotension.
• brady- (slow) vs tachy- (fast): bradycardia vs tachycardia.
• bi- (two), uni- (one), a-/an- (without, as in aphakia = no lens).

Anatomical orientation

The exam expects standard directional language from the anatomical position (standing, facing forward, palms forward):

• Superior / inferior = toward the head / toward the feet.
• Medial / lateral = toward the midline / away from the midline. For the eye, nasal = medial, temporal = lateral.
• Anterior / posterior = front / back; the anterior segment is in front of the lens, the posterior segment behind it.
• Proximal / distal = nearer to / farther from the point of attachment.
• The three body planes are sagittal (left-right split), coronal/frontal (front-back split), and transverse/horizontal (top-bottom split).

Physiology that touches the eye

The circulatory system delivers oxygenated blood; the retina is fed by the central retinal artery and the choroid, so any systemic vascular disease shows up in the fundus. The nervous system controls vision through cranial nerve II (optic) for sight and cranial nerves III, IV, and VI for eye movement; cranial nerve VII closes the lids. The endocrine system, especially the thyroid and pancreas, drives diseases (Graves disease, diabetes) with direct ocular signs. When documenting, write the decoded meaning, never a guessed abbreviation, because the medical record is a legal document.

Cranial nerves of the eye in detail

Four cranial nerves matter most for ophthalmology, and the exam often asks which nerve a deficit points to:

Pluralizing and reading medical terms

Many medical plurals follow Latin and Greek rules the exam expects: -um becomes -a (one bacterium, many bacteria), -us becomes -i (one nucleus, many nuclei), -is becomes -es (one diagnosis, many diagnoses), and -a becomes -ae (one conjunctiva, many conjunctivae). Watch for sound-alike traps: mydriasis is pupil dilation while miosis is pupil constriction; hyperopia is farsightedness while myopia is nearsightedness. A single misread vowel can flip the meaning, so decode rather than guess.

Why orientation matters in charting

The assistant records findings for each eye using OD (right eye, oculus dexter), OS (left eye, oculus sinister), and OU (both eyes, oculus uterque). Confusing OD and OS sends a finding or a medication order to the wrong eye, a patient-safety error. Combining accurate word-part decoding, correct directional terms, and the standard OD/OS/OU abbreviations is what lets the assistant document cleanly and read the physician's notes without error.

Common abbreviations the assistant must read

The chart is dense with shorthand, and misreading it causes errors. Memorize the everyday ophthalmic and medical abbreviations:

Reading a frequency order safely

Dosing abbreviations are a classic trap because they look similar. b.i.d. means twice a day, t.i.d. three times, and q.i.d. four times; q.d. (once daily) and q.i.d. differ by a single letter yet by a fourfold dose, which is why many institutions now spell out frequencies. When you transcribe a physician's instruction for a patient, write the plain-language schedule ("one drop in the right eye twice a day") rather than relying on the abbreviation alone.

Why precise language protects patients

Every term you decode feeds a legal medical record and a treatment decision. Confusing hyperopia with hypertropia, or mydriatic (dilating) with miotic (constricting), can send the wrong drop into a patient's eye. Anatomy, terminology, and abbreviation literacy together form the foundation that the rest of the General Medical Knowledge domain — systemic disease, pharmacology, and emergencies — is built on, so this is the section to master first.