Assuming fixed dilated implies 1. multiple days after surgery with washout of dilation effects of drops 2. PCIOL in bag with no chance of prolapse of haptics into iris 3. pupil does not come down with pilocarpine 4. visual acuity is normal/no profound RAPD ie visual pathway intact, you are likely dealing with a sphincter tear. I would suggest https://www.aao.org/clinical-video/single-pass-four-throw-pupilloplasty

If the pupil was 'bound down' by past inflammation before the operation, simply freeing it up may damage the iris circumferentially. Other pre existing conditions include iris atrophy from any cause eg past herpetic infection, 'essential' iris atrophy, congenital pupillary abnormality...or the eye is blind anyway from a pre operative cause because of damage to the retina or optic nerve.

I have faced three of these cases in the last 10 years:-

1- the first one was diabetic had a dilated fixed pupil with clear cornea and I used frequent topical steroids with no response then I tried topical miotics but in vain.

2- the second one was also diabetic, had a dilated fixed pupil with moderate corneal oedema after event less cataract surgery. I tried frequent topical steroid but no response. Then I tried mechanical miosis in the theater but it didn't work

3- third case was hypertensive had fixed dilated pupil with clear cornea and elevated Iop and sectorial optic disc pallor. I prescribed frequent steroids and anti-glaucoma. The iop decreased and the pupil constricted only inferiorly.

I feel that it is a low grade toxicity

I

This can redult after strech pupilloplasty where iris sphincter is strectche to dilate the pupil.

Needless to say it can occur after sphincterotomy.

The causes could be:-

1. Sphicter tear

2. Atonic pupil.

3. Iatrogenic - some staff had used atropine eye drops by mistake.

4. Raised IOP due to unwashed viscoelastic.

5. Neurological cause -a missed internal ophthalmoplegia

Possible causes include causes of iris sphincter damage during surgery

1. Elevated IOP from retained Ocular Visco Elastic Device (OVD) elevated IOP can lead to Iron ischaemia

2. Irish trauma during surgery

3. Toxic anterior segment syndrome TASS

4. In adventure use of atropine intra or post operative

5. IOL dislocation

6. Pseudophakic glaucoma

7. Malayalam glaucoma

Have you find any answer?

Currently, I am treating one patient with this atonic pupil after uneventful phacoemulsification. I observed the patient until 1 month after surgery and prescribed pilocarpine for 2 weeks and nothing happened. With the patient's consent, I did the exploration of the iris by sweeping the anterior surface of the iris gently to release any possible entrapment posteriorly and inject carbachol intraocular. Right now is 2 weeks post injection and the pupil remains in the same size as before. I am thinking about further surgery: pupilloplasty since the patient suffered from photophobia. Meanwhile, I suggest the patient wear a tinted soft contact lens to deal with photophobia.

This could occur from damage to the long ciliary nerves though injudicious use of local anaesthetic and disruption of the slcleral tunnel for these nerves bilaterally. In those ‘anything goes’ days before phaco or extracap such surgery might be called ‘uncomplicated’ but was ‘anything but’ by today’s standards. Im taling 19C to ‘70s.

On temporary basis, Give patient tinted glasses and wait for 6 months. Sometimes it gradually recovers over the time. I had one such patients who fully recovered after 6-8 months..