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OP1.2 | Refractive Errors: Classification and Correction — SDL Guide (Part 3)
Management Principles: Prescribing, Public Health and Myopia Control
Management of refractive errors encompasses three domains: accurate optical prescription, counselling about the natural history and complications of the specific error, and — in the case of childhood myopia — active strategies to slow progression. Each domain requires clinical decision-making, not merely the mechanical output of a refraction machine.
For myopia, the management goal is not simply to correct the current error but to monitor for progression and to detect complications. In children and young adults, myopia typically progresses by 0.5–1.0 D per year until the mid-twenties; each increase in axial length raises the risk of pathological complications. The prescription is updated annually. Myopia control is now an evidence-based subspecialty: low-dose atropine 0.01% (the ATOM2 trial, Singapore) reduces progression by approximately 50–60% with minimal side effects; orthokeratology (overnight rigid contact lenses) and dual-focus contact lenses also have good evidence. Increased outdoor time (at least 1–2 hours per day) reduces the incidence of myopia in children, though the mechanism is not fully established (bright light and dopamine release are implicated). High myopes (>−6 D) require annual dilated fundoscopy to screen for lattice degeneration, retinal tears, and early detachment.
For hypermetropia, the decision to prescribe depends on the patient's age, the degree of error, and the symptoms. Low hypermetropia in an asymptomatic young adult may not need correction. Symptomatic patients or those with accommodative esotropia require full cycloplegic correction. Children with significant hypermetropia (>+3.50 D) should be corrected even if asymptomatic, to prevent accommodative esotropia and amblyopia.
For presbyopia, the reading addition is titrated empirically: the weakest plus lens that gives comfortable near vision at the patient's preferred reading distance is prescribed. Patient counselling about the progressive nature of presbyopia — that the prescription will need updating every 2–3 years through the sixties — is important. Options include single-vision reading glasses, bifocals (distance on top, near segment below), trifocals, and progressive (varifocal) lenses, which provide a gradient of correction from distance to near without a visible segment boundary.
For the NPCBVI public health programme, free spectacle distribution to school-age children and adults at vision centres targets the enormous burden of uncorrected refractive error as a preventable cause of visual impairment. Awareness of referral pathways and eligibility criteria is part of the physician's role in primary care.
CLINICAL PEARL
The myopic night-shift trap: A patient in their 40s reports that their myopia seems to have decreased — they no longer need their distance glasses as much. Do NOT reassure them that their myopia has 'improved'. This is a classic presentation of nuclear sclerotic cataract causing index myopia (the hardening lens nucleus increases its refractive index, temporarily making the patient more myopic — or in a previously hypermetropic patient, apparently emmetropic — the so-called 'second sight of the aged'). The initial myopia increase will eventually give way to significant visual deterioration as the cataract opacifies further. Recognising this pattern — a middle-aged or older patient reporting unexpected improvement in distance vision — prompts slit-lamp examination for cataract.
SELF-CHECK
An 8-year-old child is brought with esotropia (convergent squint). Cycloplegic refraction reveals +5.00 D in both eyes. Which intervention is MOST appropriate as the first step?
A. Surgical correction of the squint immediately
B. Full hypermetropic spectacle correction
C. Minus lens prescription to reduce accommodative effort
D. Observation — the squint will resolve with age
Reveal Answer
Answer: B. Full hypermetropic spectacle correction
Accommodative esotropia in a child is caused by excessive accommodative effort in hypermetropia, which drives accommodative convergence and produces the squint. The first and primary treatment is full cycloplegic correction of the hypermetropia with convex (plus) lenses. Reducing the accommodative demand eliminates the stimulus for excessive convergence, and the squint may resolve completely. Surgery is only indicated if the squint persists after adequate optical correction and amblyopia treatment. Minus lenses would worsen the situation by increasing accommodative demand.
Self-Assessment: Integrating Refractive Error Knowledge
Use the following scenarios to test your ability to apply — not merely recall — the material in this module. Attempt each before consulting your notes, then check your reasoning against the content above.
Scenario 1: A 16-year-old student presents with distance VA 6/36 in both eyes and near VA N5. With a pinhole, distance VA improves to 6/9. Cycloplegic refraction reveals −4.50 D in both eyes, stable for the past year. She plays competitive football. (a) Name the refractive error. (b) What correction is indicated? (c) What public health measure would you advise to slow progression? (d) What complication would you screen for annually at her degree of myopia?
Scenario 2: A 7-year-old boy is brought by parents who notice he squints inward with his right eye when reading. VA: RE 6/6, LE 6/6 unaided. Cover test shows right esotropia on near fixation. Cycloplegic refraction: RE +4.50 D, LE +4.50 D. (a) What type of refractive error is present? (b) Explain the mechanism linking hypermetropia to the esotropia. (c) What is the first treatment step?
Scenario 3: A 51-year-old lawyer with previously normal vision reports that she can no longer read her phone without holding it at arm's length. Distance vision is 6/6 unaided. Non-cycloplegic refraction shows plano in both eyes. (a) Name the condition. (b) What is the primary mechanism? (c) What near addition power would you estimate for her age? (d) What lens options would you discuss?
For each scenario, construct a complete answer covering diagnosis, mechanism, correction type, and any management priority. Inability to answer any part indicates a gap to revisit before proceeding to OP1.4 (refractive surgery).