Presbyopia, the age-related loss of accommodation that typically becomes symptomatic in the early-to-mid forties, means the eye can no longer refocus from distance to near on its own. Soft multifocal contact lenses tackle this by presenting distance and near power to the eye at the same time. Understanding how that "simultaneous vision" works is the key to setting expectations and getting the fit right.
The short version
- Most soft multifocals are simultaneous-vision designs (centre-near, centre-distance or aspheric).
- The add is usually banded Low / Medium / High, not a single value.
- Determine ocular dominance; many designs bias the dominant eye to distance, non-dominant to near.
- Always follow the manufacturer's fitting guide; designs differ and are not interchangeable.
- Counsel on the vision compromise and allow time for neuroadaptation.
Why presbyopia needs a different approach
As the crystalline lens loses elasticity and the ciliary apparatus becomes less effective, the eye's ability to add plus power for near tasks declines. Spectacles solve this with separate zones (bifocals, progressives). Contact lenses can't rely on gaze shifting to a fixed near zone on the ocular surface, so most take a different route: deliver more than one power simultaneously and let the visual system select.
The optical strategies
Simultaneous vision (the great majority of soft multifocals)
Light from distance and near targets both reaches the retina at once; the visual system learns to attend to the in-focus image and suppress the blur. Layouts include:
- Centre-near: near power central, distance peripheral, often favoured for near-demanding patients.
- Centre-distance: distance power central, near peripheral.
- Aspheric / progressive: a gradual central-to-peripheral power change rather than distinct rings.
Alternating (translating) vision
Chiefly a rigid gas permeable strategy: distinct distance and near zones, with the lens translating up on downgaze so the near zone covers the pupil for reading. Excellent optics but design- and fit-specific; less common in soft lenses.
Monovision and modified monovision
Monovision corrects one eye for distance and the other for near using single-vision lenses; simple and often effective, but it sacrifices some binocular summation and stereopsis. Modified monovision combines a multifocal on one eye with a distance-biased or single-vision lens on the other, a useful middle path.
Add power
The add is the extra plus power needed for near, and it increases with age as accommodation declines. In contact lenses it is usually banded Low, Medium and High (sometimes with numeric ranges), because the design spreads power across zones rather than at one point. Start from the spectacle add to select the band, then refine on the eye.
Determining ocular dominance
Most fitting guides ask you to identify the dominant eye and bias it toward distance, with the non-dominant eye biased toward near. Common methods:
- Sighting dominance: the patient forms a small aperture with both hands and views a distant target through it; the eye that keeps the target is dominant.
- Sensory (blur) dominance: add ~+1.00 to +1.50 D over each eye in turn at distance; the eye that tolerates the blur least is typically dominant for distance.
The fitting process
- Refine the distance refraction and vertex-convert as needed (see the vertex guide).
- Select the starting lens and add from the manufacturer's fitting guide; do not improvise, as designs differ.
- Let the lenses settle and assess vision binocularly, in real-world lighting, at distance, intermediate and near.
- Over-refract carefully: use loose lenses in small (±0.25 D) steps, binocularly; avoid the temptation to pile on minus, which kills near vision.
- Adjust per the guide's flowchart: change one variable at a time.
Setting expectations
Counsel before you fit. Simultaneous-vision optics involve a genuine compromise: some reduction in contrast, occasional awareness of haloes (especially at night and with larger pupils), and a neuroadaptation period of days to a couple of weeks. Patients who understand this up front succeed far more often than those expecting instant, spectacle-crisp vision. Frame it as "very good all-round vision without readers," not "perfect vision at every distance."
Troubleshooting
| Complaint | Check first | Typical adjustment |
|---|---|---|
| Blurred distance | Distance sphere, centration | Refine distance (small steps); distance-bias the dominant eye |
| Blurred near | Add band, near sphere | Increase add or near-bias the non-dominant eye |
| Both blurred | Spherical Rx & lens centration | Recheck distance Rx and fit before changing add |
| Poor intermediate | Design suitability | Consider a different design or add profile |
| Night haloes / glare | Pupil size, design | Reassure during adaptation; consider alternative design |
Improving your success rate
- Select suitable candidates and set expectations early.
- Trust and follow the manufacturer's fitting guide; don't mix designs between eyes.
- Assess binocularly and functionally, not just letter-by-letter on a chart.
- Allow adaptation time and change one variable at a time.
- Consider modified monovision when a pure multifocal falls short.