# Refractive Errors and Their Management > Refractive errors for NEET-PG Ophthalmology: myopia, hypermetropia, astigmatism, presbyopia additions by age, spectacles, contact lenses, LASIK and ICL. - Canonical URL: https://prepelephant.com/topics/neet-pg/ophthalmology/refractive-errors-management - Exam / course: NEET-PG · Subject: Ophthalmology - Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team - First published: 2026-10-02 - Last updated: 2026-10-02 - How to cite: "Refractive Errors and Their Management", PrepElephant, https://prepelephant.com/topics/neet-pg/ophthalmology/refractive-errors-management ## Direct answer A normal eye focuses parallel rays of distant light exactly on the retina (emmetropia); refractive error is the mismatch between refractive power and axial length. In myopia the image falls in front of the retina and a concave (minus) lens corrects it; in hypermetropia it falls behind and a convex (plus) lens is needed; astigmatism differs in different meridians and requires a cylindrical lens; presbyopia is the age-related failure of accommodation managed with a near addition. Beyond spectacles, rigid and soft contact lenses, corneal laser surgery (LASIK, PRK, SMILE) and, for extreme myopia, implantable collamer lenses reshape or supplement the optical system. ## What you must remember - Myopia: axial myopia is the commonest type; far point lies at a finite distance (1/dioptres in metres, so −2.5 D focuses at 40 cm); corrected by the weakest concave lens giving 6/6. - Simple versus pathological myopia: simple school myopia stabilises in the twenties; pathological (degenerative) myopia shows progressive axial length with posterior staphyloma, lacquer cracks, Fuchs spot, lattice degeneration and a lifelong retinal detachment risk. - Hypermetropia: total hypermetropia = latent (masked by accommodation) + manifest (facultative + absolute); young patients compensate, so always refract children under cycloplegia. - Astigmatism: regular (with-the-rule, against-the-rule, oblique) corrected by cylinders; irregular astigmatism — classically keratoconus — is corrected by rigid gas-permeable contact lenses, never by spectacles. - Presbyopia additions by age: about +1.0 D at 40 years, +1.5 D at 45, +2.0 D at 50, +2.5 D at 55, +3.0 D at 60 — the table examiners ask for directly. - Surgical options: LASIK (flap plus excimer ablation) and PRK (surface ablation) for roughly −1 to −8 or −10 D with adequate corneal thickness and stable refraction; SMILE avoids a flap; phakic implantable collamer lens for myopia beyond laser range; clear lens exchange in presbyopic high myopes. - Anisometropia above about 2.5–3 D makes spectacle correction intolerable through aniseikonia — contact lenses or the surgical route win. - Every child with subnormal vision or squint needs cycloplegic refraction (atropine 1 per cent in young children, cyclopentolate otherwise) before any surgical talk. ## Numbers worth prescribing by Put a 45-year-old tailor in the chair. He has never worn glasses, reads at 40 cm but now pushes the newspaper to arm's length. Distance vision is 6/6 each eye, so his amplitude of accommodation has simply fallen — from about 14 D at age ten to a couple of dioptres now — and his near point has receded beyond a comfortable working distance. Prescribe the age-appropriate +1.5 D addition over his distance correction, check it at his actual working distance, and warn him the addition will rise about half a dioptre every five years. Contrast him with a 22-year-old student at −3.5 D each eye: her far point is roughly 28 cm, her near work unaided is fine but the blackboard is blurred; full correction in the weakest minus lenses, yearly review, and a dilated peripheral retina check because even moderate myopia thins the peripheral retina. If she asks about LASIK at −3.5 D with stable refraction for a year, normal topography and adequate pachymetry, she is an ideal candidate; her cousin at −14 D with a thin cornea is not — the implantable collamer lens is his answer. ## How the exam frames it Expect one-liners built on arithmetic and definitions: the far point of a −2.5 D myope (40 cm), the power of the correcting lens for a hypermetrope whose near point is 50 cm, or which addition suits a 55-year-old (answer +2.5 D). Stems describing "best vision with a pinhole in a young patient" point to refractive error, and "progressive myopia with night-driving halos and streaks" points to keratoconus. Viva examiners probe why contact lenses beat spectacles in anisometropia and in irregular astigmatism — retinal image size and surface tear-lens correction respectively. ## Frequently asked questions ### What is the far point of a −2.5 D myopic eye? Forty centimetres; the far point in metres equals one divided by the myopia in dioptres, which is also how a myope sees clearly without glasses by bringing objects to that distance. ### What lens corrects hypermetropia and why? A convex (plus) lens, because it adds converging power so that parallel rays focus on the retina rather than behind it; part of the error may be hidden by accommodation, hence cycloplegic refraction. ### What near addition is typical at 50 years of age? About +2.0 D over the distance correction, rising to +2.5 D at 55 and +3.0 D at 60, reflecting the falling amplitude of accommodation. ### How is irregular astigmatism corrected and why not with spectacles? A rigid gas-permeable contact lens, because its tear lens replaces the irregular corneal surface with a regular optical front; spectacles cannot compensate meridian-to-meridian irregularity. ### Which surgical option suits a −14 D myope with thin corneas? An implantable collamer (phakic intraocular) lens, since excimer laser ablation of that magnitude would leave an unstable, ectasia-prone cornea. ### What fundus changes mark pathological myopia? Posterior staphyloma, lacquer cracks, Fuchs spot at the macula, peripheral lattice degeneration and areas of chorioretinal atrophy — with regular dilated examination for treatable detachment-risk lesions.