Small Pupils in Cataract and Lens Replacement Surgery: What PXE, Diabetic, and Elderly Patients Should Know About Pupil Expanders and Premium Lens Outcomes
- Posted
- Medically Reviewed by: Mr Mfazo Hove, Consultant Ophthalmic Surgeon
- Author: Mr Mfazo Hove
- Published: November 23, 2025
- Last Updated: January 7, 2026
Not every eye behaves the same way during cataract or lens replacement surgery. Some patients naturally have small pupils – and this can affect both the surgical approach and the choice of lens implant.
Small pupils are especially common in:
- Pseudo-exfoliation (PXF/PXE)
- Diabetes
- Elderly patients
- Patients using long-term glaucoma drops
- Those with previous uveitis
- Individuals with senile sphincter rigidity
This blog explains why small pupils matter, how surgeons safely enlarge them using pupil expanders, and whether these expanders affect the final outcome in premium lens cases.
1. Why small pupils matter during cataract or lens replacement surgery
Successful cataract/lens surgery relies on:
- Clear access to the lens
- A stable pupil
- Controlled illumination
- Sufficient space to manoeuvre instruments safely
When pupils remain at 2–3 mm, this becomes difficult because:
- The capsulorrhexis is harder to see
- The lens nucleus is tighter to access
- The zonules may be weak (especially in PXE)
- There is less margin for error
- The risk of iris trauma increases
To maintain safety, surgeons use pupil expansion devices.
2. Main pupil expansion devices used today
- Malyugin Ring (2.0 / 2.5 versions)
- The most popular worldwide
- Creates a round, stable 6–7 mm pupil
- Minimises iris trauma
- Quick to insert and remove
- Excellent for PXE and elderly eyes
- Iris Hooks
- Versatile and inexpensive
- Offer adjustable expansion
- Useful in extremely floppy irides
- Create a “square pupil” rather than round
- Slightly more manipulation of the iris
- Other expansion rings (B-HEX, I-Ring)
- Provide stable circular dilation
- Reduced iris stretch
- Good for surgeons comfortable with ring-based devices
3. Why PXE, diabetics, and elderly patients often need expanders
- A) PXE (Pseudo-exfoliation)
- Poor dilation
- Weak zonules
- Floppy iris
- Higher risk of surgical complications
- Pupil expanders reduce that risk
- B) Diabetes
- Neuropathy reduces sympathetic dilation
- Sphincter muscle becomes rigid
- Pupils often “snap back” after minimal dilation
- Expanders ensure a stable working area
- C) Elderly patients
- Age-related stiffening of the iris
- Smaller baseline pupil sizes
- Narrow mesopic pupil range
- Pupils may become progressively harder to dilate with drops
4. Do pupil expanders damage the eye or affect premium lenses?
Short answer:
When used correctly, they do not reduce the quality of vision or limit premium lens outcomes.
However, there are considerations.
5. Effects of pupil expanders on the surgical outcome
- Temporary postoperative pupil irregularity
Some patients may experience:
- Mild ovalisation
- Slight eccentricity
- Transient photic symptoms
These usually resolve within days to weeks.
- Very rarely, long-term pupil shape change
More likely with:
- Rigid hooks
- Over-stretching
- Very fibrotic irides
- PXF cases with friable tissue
- Prior uveitis
Even in these cases, the effect on vision is generally mild.
6. Effects on multifocal or EDOF lens performance
This is where the subtle nuance matters.
- A) Multifocal lenses
These depend on:
- A round pupil
- Centrally aligned optics
- Balanced distribution of light
If the pupil remains slightly oval long-term:
- Some patients may experience small changes in night vision
- Halos/glare may be mildly accentuated
- Depth-of-focus behaviour may shift slightly
However, in practice:
- Most pupils return to near-normal shape
- Multifocal performance remains good
- Only rare cases have lasting visual impact
- B) EDOF lenses
EDOF implants are more tolerant.
- They do not split light
- They are less pupil-dependent
- They perform well even with slight irregularities
- They are ideal for small pupil or PXE cases
- C) Monofocal lenses
Completely unaffected.
7. Does stretching the pupil affect long-term dilation?
Not usually.
The pupil is elastic and returns to its natural behaviour.
Rare exceptions:
- PXE with friable iris
- Iris hooks applied aggressively
- Pre-existing sphincter damage
- Severe intraoperative floppy iris syndrome (IFIS)
Even then, the impact is typically small.
8. Does using an expander increase light scatter or glare long-term?
There is no evidence that properly used expanders create:
- Long-term glare
- Increased halos
- Reduced contrast
- Impaired night vision
Short-term glare immediately after surgery may be from:
- Pupil oedema
- Inflammation
- Temporary irregularity
These resolve with healing.
9. Are premium lenses safe in small-pupil patients?
Yes – with the right pre-operative assessment.
Surgeons consider:
- Baseline photopic pupil
- Mesopic pupil size
- Iris rigidity
- Risk of IFIS
- PXE severity
- Diabetes stage
- Whether hooks/rings will be needed
- Patient’s night-driving profile
In general:
- Multifocal lenses: safe in most small-pupil patients if the pupil is regular post-op
- EDOF lenses: the best premium choice for PXE/diabetics
- Monofocal lenses: always safe
10. Why careful technique matters more than the device
A pupil expander is simply a tool. Outcomes depend on:
- Gentle handling
- Balanced tension
- Avoiding sphincter tears
- Minimising iris manipulation
- Good fluidics
- Avoiding zonular stress in PXE
- Ensuring centred capsulorrhexis
- Choosing the right lens for the patient
Blue Fin Vision®’s approach prioritises pupil preservation, iris safety, and non-traumatic expansion techniques to ensure visual outcomes are never compromised.
11. Summary: Small pupils are manageable, and expanders protect vision - not harm it
Pupil expanders are essential for safety in:
- PXE
- Diabetics
- Elderly patients
- Anyone with naturally small pupils
When used properly, they:
- Protect the iris
- Improve surgical visibility
- Reduce complications
- Preserve the capsular bag
- Maintain excellent lens centration
- Support excellent outcomes with premium lenses
And most importantly:
They do not reduce visual quality after surgery.
They make the surgery safer, more controlled, and more predictable.
