A child sits close to the television and holds books near his face. Distance vision is blurred; near vision is clear. What is the refractive error and how is it corrected? ANSWER: MYOPIA (short sight), corrected with a CONCAVE (diverging) lens. MECHANISM: the image falls SHORT of the retina — in front of it — because the eye is too long or its optics too powerful. Distant objects blur; near objects still focus correctly. A concave lens diverges incoming light so the focal point moves back onto the retina. CONTRAST: HYPERMETROPIA image would fall BEYOND the retina; near blurs first; CONVEX lens ASTIGMATISM different power in different meridians, no single focus, blur at ALL distances; CYLINDRICAL correction

A 48-year-old finds she must hold the newspaper at arm's length. Distance vision is unchanged. What is this, and what is the mechanism? ANSWER: PRESBYOPIA — failure of ACCOMMODATION, not a refractive error in the usual sense. MECHANISM: the lens STIFFENS with age and loses the ability to change shape, so the eye can no longer increase its power for near work. TYPICAL HISTORY: middle age, holding things further away, worse in dim light and when tired, distance vision unaffected. TREATMENT: reading glasses. It happens to everyone eventually. THE EXCEPTION WORTH KNOWING: presbyopia arrives GRADUALLY. A relatively RAPID change in reading vision is something else — cataract commonly, and fluctuating refraction is a recognised presentation of poorly controlled DIABETES. A new or changing prescription in a middle-aged patient is a reason to check the glucose.

A patient's blurred vision improves fully when they look through a pinhole. What does this tell you? ANSWER: the problem is REFRACTIVE — the eye itself is healthy. A pinhole admits only the central rays of light, removing the effect of the eye's optical error, so a refractive problem improves. CLINICAL VALUE: it separates two situations quickly and without equipment. IMPROVES with pinhole → refractive; needs glasses DOES NOT improve → something wrong with the EYE — cataract, retinal or optic nerve disease — and needs examination This is a useful bedside test in any setting where formal refraction is not available.

A 7-year-old is described by his teacher as inattentive and is falling behind. How should vision be tested, and why does the method matter? ANSWER: test EACH EYE SEPARATELY, covering the other. WHY IT MATTERS: a child with one good eye and one poor eye sees normally with BOTH OPEN. He will not complain, will pass a casual test, and the poor eye goes unnoticed. TWO CONSEQUENCES OF MISSING IT: 1. SCHOOL PERFORMANCE — a child who cannot see the board is labelled inattentive or slow, and acquires that label instead of glasses. 2. AMBLYOPIA — a persistently blurred image prevents that eye's visual pathway from developing. Corrected EARLY, vision develops normally. Corrected after the developmental window closes, vision is PERMANENTLY lost even though the eye is structurally normal and the glasses are now correct. So the deadline here is developmental, not optical.

A 4-year-old has persistent obstruction of ONE nostril with foul-smelling discharge. She is otherwise well. What is the most likely cause? ANSWER: a retained NASAL FOREIGN BODY. THE DISCRIMINATOR IS LATERALITY: BILATERAL obstruction with sneezing and clear discharge → rhinitis, allergic or viral BILATERAL, long-standing, with LOSS OF SMELL → nasal polyps (ask about asthma and aspirin sensitivity) UNILATERAL → a different question entirely IN A CHILD: foreign body, often present for weeks — children do not reliably report putting it there, and the foul smell comes from the retained object. IN AN ADULT: unilateral obstruction, especially with BLEEDING or foul discharge, requires examination to EXCLUDE A TUMOUR. Bilateral is usually benign; unilateral earns a look.

A patient with several days of sinusitis develops swelling and redness around one eye. What is the concern, and what should be done? ANSWER: ORBITAL or PERIORBITAL infection spreading from the sinus. This is an EMERGENCY requiring urgent referral. ANATOMICAL REASON: the ORBIT lies immediately beside the sinuses, separated only by a thin plate of bone. FEATURES THAT RAISE THE CONCERN FURTHER: a PROPTOSED eye, or one that cannot move fully DOUBLE VISION REDUCED VISION — which threatens the optic nerve THE COMMON ERROR: treating it as conjunctivitis or an allergic reaction and sending the patient home with drops. Sight can be lost within a day. WHAT SHOULD CHANGE YOUR MIND: the presence of SINUS SYMPTOMS alongside a swollen eye. That combination is not conjunctivitis. ALSO CONSIDER intracranial spread: severe headache, altered consciousness, neck stiffness or focal signs.

A patient with sinus pain has thick green nasal discharge and asks for antibiotics. What is the correct response? ANSWER: coloured discharge alone does NOT indicate bacterial infection. 1. Most acute sinusitis is VIRAL and resolves without antibiotics. 2. The colour reflects inflammatory cells present in any upper respiratory infection — not the organism. 3. So colour is not a reason to prescribe. WHAT TO DO: explain the expected course, offer symptomatic relief, give safety-net advice, and say what would change your mind — the same consultation described in the antimicrobial chapters. WHAT WOULD CHANGE YOUR MIND: the complications, not the colour. Eye swelling, proptosis, double or reduced vision, severe headache, altered consciousness, or a patient who is systemically unwell.