Mini-monovision with an EDF lens buys little and costs contrast

Design

Prospective, randomised, patient- and examiner-masked single-centre trial

Population

60 patients (120 eyes) having bilateral cataract surgery with a refractive EDF intraocular lens; 55 completed

Primary outcome

Binocular uncorrected and corrected visual acuity at distance, intermediate and near at 3 months

Effect

No significant acuity differences (all ≤0.04 logMAR); emmetropia better by 0.10 logMAR at 5% (P<0.001) and 1.25% (P=0.01) contrast

Sixty patients having bilateral cataract surgery with a refractive extended depth of focus lens were randomised, patient- and examiner-masked, to mini-monovision at −0.75 D in the non-dominant eye or to emmetropia in both, and assessed at three months.

Binocular distance, intermediate and near acuity did not differ significantly between the strategies — all the differences were 0.04 logMAR or less, with intervals crossing zero. Defocus curves were comparable after correction for multiple comparisons, and stereopsis was preserved either way.

Where they differed was contrast. The emmetropic group was better by 0.10 logMAR at both 5 per cent and 1.25 per cent contrast, surviving Holm-Bonferroni correction, and the mini-monovision group reported more glare. Near spectacle dependence was slightly lower with mini-monovision, which is the gain being bought. With a lens of this design, the offset is not obviously worth it.

• With a refractive extended depth of focus lens, target emmetropia in both eyes unless the patient specifically prioritises near vision.
• Where mini-monovision is used, warn about glare and reduced low-contrast vision specifically.
• Do not extrapolate to diffractive multifocal lenses or to larger monovision offsets; this was −0.75 D with one lens.
• Three-month outcomes may not capture neuroadaptation to monovision.
• Fifty-five of 60 patients completed follow-up in a single centre — a small trial with a clean design.

Why it matters

It removes the assumption that adding a small monovision offset to a modern EDF lens is a free gain in near vision.

Don't overread it

One lens design, one centre, 55 patients analysed at three months.

The statistics, in plain English

Non-significant differences in a 60-patient trial are not proof of equivalence — the intervals around the acuity differences (for example −0.09 to 0.01 logMAR for intermediate vision) allow small real differences either way. The low-contrast findings are more secure because they survived Holm-Bonferroni correction, which is a deliberately conservative way of controlling for testing many outcomes at once. A 0.10 logMAR difference is one line on a chart, which matters most in exactly the conditions low-contrast testing simulates.

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