Myopia, hypermetropia, astigmatism and presbyopia

01OverviewDefinition, clinical context and the essential points that orientate the chapter.

Refraction describes how the eye's optical power and length combine to focus light. In an emmetropic eye with accommodation relaxed, distant parallel rays focus on the retina. Myopia and hypermetropia reflect a mismatch between that focal plane and the retinal position. Astigmatism adds unequal focusing in different meridians. These errors are measured in dioptres and can often be corrected effectively, but a prescription is not a complete assessment of the eye's health.

Accommodation changes the natural lens's power for near tasks. A young person can sometimes compensate for hypermetropia through accommodation and may have good distance acuity while experiencing near strain. With increasing age, accommodation declines and presbyopia makes close work more difficult. This is distinct from an anatomically short hypermetropic eye: a myopic adult can also become presbyopic, sometimes noticing that removing distance spectacles helps reading.

Management must address the person's age and goals. In adults this often means an accurate spectacle or contact lens correction with investigation of unexplained changes. In children, clear vision supports learning and prevents amblyopia, while progressive myopia may also merit a dedicated management discussion. Reducing spectacle dependence by surgery later in life does not shorten a long eye or remove its retinal risks. Similarly, using a reading aid for presbyopia does not eliminate the need to evaluate persistent or asymmetric blur.

Key points

Myopia focuses distant light in front of the retina when accommodation is relaxed and is corrected with minus power.
Hypermetropia focuses light behind the retina without accommodation and is corrected with plus power.
Astigmatism involves different focusing powers in different meridians and usually needs cylindrical correction.
Presbyopia is an age-related loss of accommodation and can coexist with any distance refractive error.
Use refraction and ocular examination together; pinhole improvement alone does not exclude eye disease.
Childhood myopia management aims to slow progression while maintaining clear optical correction and monitoring eye health.

02AetiologyUnderlying causes, associations and risk factors, with why each one matters.

Eye length and optical power

Myopia commonly accompanies axial elongation, whereas hypermetropia often reflects a relatively short eye. Corneal and lenticular power also contribute, so equal spectacle errors do not imply identical anatomy.

Corneal and lenticular shape

Astigmatism usually arises from unequal curvature of the cornea, with possible contributions from the lens. It may be regular and correctable with a cylinder or irregular because of scarring or ectasia.

Ageing accommodation

The ageing natural lens and accommodative system become less able to increase focusing power for near targets. Presbyopia becomes symptomatic according to working distance, lighting, baseline refraction and visual demands.

03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.

1
Myopic defocus
When distance light focuses anterior to the retina, a minus lens reduces the eye's effective converging power. Nearer objects can remain clearer without correction, but the useful working distance depends on the refractive error.
2
Hypermetropic demand
A plus lens supplies converging power needed to move focus forward onto the retina. Uncorrected hypermetropia can require accommodation even for distance, placing extra demand on the near focusing system.
3
Meridional blur
In regular astigmatism, perpendicular principal meridians have different powers. A cylindrical or toric component supplies the appropriate difference; spherical correction alone may leave orientation-dependent blur or ghosting.
4
Presbyopic near point
As accommodation declines, the nearest distance that can be focused comfortably moves away. Additional plus power for near reduces the accommodative demand without correcting every other cause of near visual difficulty.

04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.

Distance and near pattern

Ask which tasks are blurred and whether symptoms occur with current spectacles, without them or only after prolonged work. Distance blur with relatively clearer near vision suggests myopia; near strain can occur with hypermetropia or presbyopia. These patterns guide testing but do not replace refraction.

Age and trajectory

Clarify when spectacles began, family myopia, previous prescriptions and the rate of change. Younger onset and progression matter when counselling about childhood myopia. A stable adult prescription is a different problem from rapidly increasing myopia in a young child.

Interocular and binocular function

Check each eye separately and assess alignment and binocular symptoms. In a child, significant hypermetropia may contribute to accommodative esotropia. New binocular diplopia requires a separate assessment rather than simply attributing it to astigmatism.

Correction and exposure history

Review spectacle fit, contact lens type, wear duration, overnight use, water exposure and hygiene. Ask about previous laser or lens surgery. These details can explain optical symptoms and identify corneal risks that a refraction printout will not show.

Red flags requiring action

A myopic patient with new flashes, a shower of floaters or a field curtain needs urgent retinal examination.
Pain, photophobia or a corneal white spot in a contact-lens wearer suggests microbial keratitis.
Rapidly increasing or irregular astigmatism may indicate corneal ectasia and warrants corneal assessment.
A child with very early, unusually high or asymmetric myopia needs assessment for associated ocular or systemic disease.

05InvestigationsWhat to request, why it matters and how to interpret it.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
Monocular distance and near acuityFirst step
Why
Define the functional deficit before and after correction.
Interpretation and limitations
Test with the relevant current correction and document each eye. Pinhole can suggest an optical component by reducing peripheral rays, but incomplete or absent improvement needs interpretation in context. It is not a substitute for examining the ocular structures.
02
Objective and subjective refraction
Why
Measure spherical and cylindrical correction and refine usable focus.
Interpretation and limitations
Retinoscopy or autorefraction provides objective information, with subjective refinement when possible. Cylinder power requires an axis. In children, cycloplegic refraction may be needed to reveal hypermetropia or avoid overestimating myopia from active accommodation.
03
Corneal assessment and topography
Why
Investigate irregular or unexpectedly changing astigmatism and lens intolerance.
Interpretation and limitations
Inspect the ocular surface and cornea. Topography or tomography helps identify ectatic patterns and assess suitability for specialist correction or surgery. Increasing cylinder in a young person should not be dismissed as an ordinary prescription change without considering keratoconus.
04
Ocular health and myopia measurements
Why
Assess associated pathology and quantify progression when relevant.
Interpretation and limitations
Examine the posterior segment and measure pressure as clinically indicated. A myopia management service uses repeatable refraction and may track axial length. Interpret change using comparable methods and dates; measurements made with different accommodative states are not directly equivalent.

06Differential diagnosisRealistic alternatives and the features that help distinguish them.

Lens or glucose-related change

Cataract and changing glycaemia can alter refraction. A new prescription requirement, especially a rapid or asymmetric change, should prompt attention to ocular and systemic context rather than repeated spectacle replacement alone.

Ocular surface or corneal disease

Tear instability causes fluctuating clarity, while keratoconus or corneal scarring can produce irregular astigmatism. Symptoms, examination and topography distinguish these from a stable regular refractive error.

Retinal or optic nerve disease

Persistent reduction despite appropriate correction, distortion, field loss or a relative afferent pupillary defect suggests another cause. Coexisting refractive error must not distract from investigating that abnormality.

07ManagementImmediate care, first-line treatment, alternatives and escalation.

01CorrectProvide clear and comfortable everyday visionFirst stepAlternativeExamination identifies a refractive error without an urgent alternative cause.

1Explain the error and trial the required spherical, cylindrical or near addition with the person's usual tasks in mind.
2Select spectacles or professionally fitted contact lenses according to optical needs, handling ability and ocular surface health.
3Check adaptation, fit and binocular comfort after major changes, especially with anisometropia or a new presbyopic correction.
4Investigate persistent symptoms despite an apparently adequate prescription instead of repeatedly increasing lens strength.

02Childhood progressionDiscuss a myopia management planA child has myopia or evidence of continuing myopic progression.

1Provide appropriate refractive correction and establish baseline progression, family history, ocular findings and any atypical features.
2Discuss outdoor activity, sensible breaks from sustained near work and the available optical or pharmacological options with realistic expectations.
3Refer to a clinician competent in myopia management when considering specialist spectacles, contact lens strategies or low-dose atropine.
4Agree review measures and adverse-effect reporting, explaining that slowing progression does not mean reversing the existing refractive error.

03Near difficultyAssess likely presbyopia in an adultClose work has become progressively harder as accommodative reserve declines.

1Measure distance and near vision and exclude a new ocular problem, particularly when symptoms are asymmetric or involve distortion.
2Discuss a near addition, occupational lenses, multifocal spectacles or suitable contact lens approaches for the working distances required.
3Explain that removing minus distance spectacles may help a myopic person read, while still leaving distance correction necessary.
4Review continuing difficulty and lighting needs, especially when a simple reading aid fails to improve functional near vision.

Key medicines and prescribing safety1 treatment · regimens, roles and cautions

Slows progressive childhood myopia; initiation is licensed at ages 3–14 years, refraction −0.5 to −6.0 D and progression at least 0.5 D/year.

Ryjunea 0.1 mg/mL atropine for childhood myopia

This is a paediatric indication: in eligible children, instil one drop in each eye once daily, preferably at bedtime, under a myopia-competent prescriber.

Do not substitute atropine 1%. Contraindications include primary or angle-closure glaucoma and relevant anticholinergic allergy. Assess atypical or syndromic myopia before treatment. Discuss photophobia, near blur and systemic anticholinergic effects, with extra caution in cardiac disease, fever, Down syndrome or spastic paralysis. Compress the lacrimal sac for one minute; remove contact lenses before dosing and wait fifteen minutes before reinsertion. Separate other eye drops by at least fifteen minutes.

08ComplicationsImportant consequences, why they occur and why they matter clinically.

Developmental amblyopia

Uncorrected substantial or unequal refractive errors can impair visual development in childhood. Anisometropia may be missed because the better eye compensates, making monocular assessment important.

Myopic ocular disease

Increasing axial myopia is associated with retinal detachment, myopic macular disease and other ocular risks. Good corrected acuity or successful refractive surgery does not remove the need for appropriate surveillance.

Visual strain and functional limitation

Uncorrected blur can affect school tasks, driving, reading and work. Headache alone is nonspecific, so apparent refractive strain should be reconsidered when correction does not resolve the complaint.

09Monitoring and follow-upTreatment response, safety checks and longer-term review.

Review correction, monocular acuity and ocular health at an interval appropriate to age, refractive change and associated disease; do not equate a stable prescription with a normal retina.
For myopia treatment, use a recorded baseline and comparable follow-up measurements to assess progression and discuss whether treatment remains useful and tolerable.
With low-dose atropine, assess adverse effects and ongoing need; the product advises considering tapering and stopping during adolescence once progression is below 0.5 D over two years, with monitoring for one year after cessation.
Check contact lens hygiene and adherence to replacement and wear schedules; discomfort or reduced vision should trigger assessment before further lens wear.
Review children's spectacle use and visual development, including whether significant asymmetry, strabismus or amblyopia requires orthoptic or ophthalmic care.
Advise against cycling, driving or operating machinery while atropine-related vision remains blurred; review troublesome symptoms. If treatment continues into reproductive age, reassess pregnancy or breastfeeding with the prescriber before use.

10Special situationsVariants, exceptions and circumstances that change the usual approach.

Minus and plus are optical directions

A minus prescription does not measure retinal health or define every cause of myopia. A plus prescription does not guarantee good distance vision without correction, particularly when the refractive error exceeds accommodative reserve. Explain the actual test result rather than relying on everyday labels alone.

Near work is not the whole explanation

Myopia reflects genetic and environmental influences. Encourage practical healthy visual habits without blaming a child or family for developing the condition. Management discussions should distinguish measures intended to reduce onset risk from treatments intended to slow established progression.

Accommodation can hide hypermetropia

A child can accommodate during testing and appear less hypermetropic than they are. Cycloplegia helps reveal the underlying refraction when clinically appropriate. This matters in assessment of strabismus and suspected amblyopia as well as selection of spectacles.

Presbyopia and myopia can coexist

A myopic adult may use an uncorrected near focal point to read when their accommodation declines. That practical strategy does not restore accommodation and may not work for every distance or degree of myopia. Occupational requirements help determine the most useful correction.

11Common pitfallsFrequent interpretation and management errors.

01
Assuming presbyopia is the same anatomical condition as hypermetropia.
02
Prescribing a stronger spherical lens for irregular astigmatism without assessing the cornea.
03
Using improvement through a pinhole to dismiss coexisting retinal or optic nerve pathology.
04
Describing all low-dose atropine treatment as unlicensed despite the current UK paediatric product.
05
Telling a patient that laser correction of myopia removes the lifetime risks associated with a long eye.