In ophthalmology, three widely repeated figures do not survive a reading of the sources. There is no acuity threshold for cataract surgery. Injections for macular degeneration do not produce a lasting gain in vision. And the 20-20-20 rule has no primary source. All three come from trials and guidelines, not from opinion.
The questions we get asked
When is a cataract operated on?
When functional impairment justifies it, and the reference guideline states that the decision must not rest on measured acuity alone. Waiting beyond six months worsens outcomes, but the intermediate interval has never been tested.
Is a multifocal lens worth paying for?
This is the decision where the evidence is most asymmetric. The most marketed benefit is graded low certainty with documented publication bias; the harm, halos, is graded moderate certainty. The toric lens, by contrast, has an established benefit at high certainty with no photic trade-off.
Do injections save sight in macular degeneration?
They slow a loss. The 8-letter gain at one year is real; at five years the mean has fallen below baseline, and at seven years almost every eye shows macular atrophy.
How urgent is a retinal detachment?
It depends on the macula. If it is still attached, the urgency is real and counted in hours. If it is already detached, the useful window is six to seven days, not 24 hours.
What the figures say
| Finding | Figure | Source |
|---|---|---|
| Acuity threshold for cataract surgery | none | AAO, 2021 |
| Halos after a multifocal lens | risk multiplied by 3.6 | Cochrane, 2016 |
| Visual gain on anti-VEGF, 1 year then 5 years | plus 8 letters, then minus 3 | CATT, 2011 and 2016 |
| Primary success of first detachment surgery | 53.4 to 72.0 percent | SPR trial, 2007 |
| New visual symptoms after LASIK | 43 to 46 percent at 3 months | PROWL, 2017 |
| Glaucoma screening, people unaware they have it | 1 in 2 | see our dedicated article |
What Noria Health does, and does not do
We organise an ophthalmology consultation with a specialist team near Brussels, full assessment, OCT and review of existing imaging according to the reason for referral. Feasibility confirmed within 24 to 48 hours, follow-up documented at D14, D30 and D90.
We set no surgical indication remotely and we handle no emergency. Sudden loss of vision, flashes, a shower of floaters, a curtain across the field, or a red and painful eye all need same-day examination, without waiting for a reply from us.
Who reviewed this page
Noria Health editorial team.
Our ophthalmology articles
- Cataract: there is no acuity threshold for surgery
- Macular degeneration: 8 letters gained at one year, 3 lost at five
- The 20-20-20 rule has no source, and the trial that tested it is negative
- Glaucoma: 1 person in 2 does not know they have it
Have your case reviewed. Noria Health arranges a specialist consultation near Brussels and confirms feasibility within 24 to 48 hours. Open a case.