Presbyopia Surgery, Monovision and Historical Refractive Procedures

Separate spectacle independence from accommodation

Presbyopia surgery seeks useful vision across working distances. Most current optical strategies do not restore youthful physiological accommodation. A patient may accept improved near function while losing some contrast, stereoacuity or night comfort, but that decision depends on their tasks and expectations. Ask about driving, reading, screens, fine work, dominant eye, binocular status and tolerance of previous contact lenses before naming a preferred procedure.

Baseline refraction, ocular health, corneal tomography, surface quality and retinal/optic nerve function remain relevant in a presbyopic patient. A request to avoid glasses is not a reason to ignore a mild cataract or macular disorder. Discuss spectacles and contact lenses as well as surgery and explain that later ageing or lens opacity can change the result. Avoid promising permanent freedom from all correction.

Monovision and blended strategies

Monovision targets one eye predominantly for distance and the other for near. The intended anisometropia depends on desired working distance and tolerance. A mild near target can retain more binocular distance performance but provides less close reading ability. Larger differences can increase near range while reducing stereoacuity or binocular summation. Test ocular dominance in context rather than assuming it is immutable, and assess binocular vision rather than applying the same target pair to every patient.

A contact-lens simulation can reveal unacceptable imbalance before an irreversible treatment. It cannot reproduce every surgical aberration or future lens change, but it supports informed discussion. A patient with strabismus, amblyopia or marginal fusion may be less tolerant of intentionally unequal focus. Occupations requiring precise depth perception and night vision need particular attention.

Blended-vision approaches combine modest anisometropia with an extended depth of focus or altered aberration profile. The terminology is platform-specific and does not prove that stereoacuity is unchanged. Explain the actual optical mechanism and assess visual quality rather than relying on a marketing name. Monovision can be created by corneal treatment, contact lenses or IOL targets, each with different reversibility and risks.

Multifocal optics and lens procedures

Presbyopia-correcting IOLs divide light or extend the focus range, depending on design. Diffractive multifocal optics can provide useful near function but may cause halos, glare and reduced contrast. Extended-depth designs also involve trade-offs and do not guarantee the same near performance as every trifocal. Residual refractive error, decentration, surface disease and macular dysfunction can make these compromises more noticeable.

Refractive lens exchange removes remaining natural accommodation and carries intraocular surgical risks, including infection and retinal complications. It may be reasonable in selected presbyopic patients, but deserves caution in younger long myopic eyes. A toric monofocal with an appropriate target, bilateral distance monofocals with reading glasses, or staged decisions can all be valid alternatives. Assess the patient’s tolerance rather than assuming the most complex optic produces the best quality of vision.

Rings and corneal inlays

Intrastromal corneal ring segments redistribute corneal shape and are used in selected ectatic corneas to improve regularity or contact-lens tolerance. They do not directly arrest ectatic progression or function as a universal substitute for cross-linking. Implant depth, corneal thickness and central scarring affect suitability. Migration, extrusion, infection and insufficient effect are possible; a removable implant is not free of permanent tissue consequences.

Corneal inlays have used small-aperture or refractive principles to improve near vision. Their limitations include haze, inflammation, contrast effects, centration and potential need for removal. Historical authorisation does not establish current availability in every European country. Before discussing a specific device as an active treatment, check current model, regulatory status and long-term evidence. The syllabus includes older methods because patients still present with their consequences.

Incisional and thermal history

Radial keratotomy (RK) uses radial corneal incisions to flatten the central cornea. Long-term problems can include diurnal fluctuation, progressive hyperopic change, irregular astigmatism and wound vulnerability. A later cataract calculation must account for altered corneal optics and variable measurements; simply applying an untreated-cornea formula can produce refractive surprise. Surgical incisions should be planned to avoid destabilising previous RK wounds when possible.

Astigmatic keratotomy changes curvature by incisions in selected meridians. Effect depends on arc length, depth, diameter, corneal biomechanics and healing; an axis alone does not determine the dose. Thermal methods alter collagen and shape but can show regression and induced irregularity. Historical procedures should be understood mechanistically rather than memorised as uniformly successful permanent corrections.

A practical decision

A presbyopic night driver with excellent distance vision may value contrast more than close reading without glasses. A patient with previous RK needs stable repeated measurements and realistic discussion of uncertainty before cataract surgery. In either case, specify the goal, alternatives, reversibility and likely optical compromises. This is the clinical reasoning behind the EBO optics and refractive syllabus, rather than an endorsement of a particular commercial technique.