Effect on IOP after cataract surgery?

[NightHawkGuy]

My eye surgeon had told me that typically after cataract surgery IOP is lower about 4 points.
However its now 4 months after I had cataract surgery on my right eye and the IOP result in my last few eye doctor visits over the last couple months have remained close to what it was prior to the surgery.

I still am taking the same two eye drop medications in my right eye as I have for the past 3 years: Lumigan and Dorzolamide-Timilol (combo drop).   I'm getting 15-16 typically for IOP in my right eye with the medications measured with the blue light, and about 18 with a simple air puff test since I have thicker than average cornea.

I have had a complete dilated eye exam, eye photos, visual field test, and an OCT all done over the past couple months with my comprehensive ophthalmologist.  The glaucoma in my right eye has been stable for the past 3 years with the eyedrops. My right eye only has the defect in one quadrant shown on the VFT as the nasal superior quadrant.

About how long after cataract surgery should significant IOP lowering be noticeable and if not seen by then is the chances high that IOP will not lower anymore due to that?

[John C Hagan III, MD, FACS, FAAO]

If you were going to experience a 1-4 point drop it would have occurred by now so likely not going to happen.  Over large groups of people the drop is about 1-2  not 4 pts.  However over your lifetime your glaucoma will be milder and easier to control for having had the surgery. Remember also that glaucoma, like many diseases, often worsens and is more difficult to control.

[NightHawkGuy]

Interesting - thanks!

Also are minimally invasive glaucoma procedures such as Selective Laser Trabeculoplasty (SLT) now considered a good option to reduce the use of eyedrops with BAK preservative that over time can negatively affect the ocular surface?

[John C Hagan III, MD, FACS, FAAO]

Because of the problems with cost, compliance, and the ability to instill eye drops the % of people treated with SLT or the older ALT goes up every year.  I generally offer one/drop day trial of latanoprost, lumigan or Travatan-Z or SLT.   If patient chooses drops and one drop once per day I strongly recommend SLT before adding a second or third drop. The biggest change in glaucoma over the coming years will be putting MIGS device in eye at time of surgery (small drainage valve MIGS = minimally invasive glaucoma surgery) to try and eliminate need for any drops.

[NightHawkGuy]

Yes I learned that the glaucoma specialist eye surgeon at my local clinic does the iStent device implantation at the time of cataract surgery.  But I read it might only reduce IOP by about 1 point, so I didn't opt for that since the typical IOP reduction for cataract surgery is more than that.  I might consider other minimally invasive surgery in the future that offer at least a few points IOP reduction, if my right eye's IOP ever starts going up significantly even with my existing eyedrops or if they continue to be hard to get over the long term.

[John C Hagan III, MD, FACS, FAAO]

Once gain your data is not correct or if you did find a study with 1 mm reduction it is not typical.  No surgeon or patient or insurance company is going to spend extra money, take additional risks for 1 mm pressure reduction. In this study:  https://www.nature.com/articles/eye2016139

In 40+ patients at 3 years post OP average IOP was 4 mm lower and the person was on one fewer glaucoma drops.

[NightHawkGuy]

Is that average IOP reduction of 4mm for the combined cataract surgery effect with the iStent, since usually as I understand it the iStent is implanted during the same procedure as the IOL.

[John C Hagan III, MD, FACS, FAAO]

You are a smart guy you can pull up the various studies that have been done.  Assuming proper placement of istent the IOP will be lower when done in addition to the cataract/IOL surgery than the Cataract/IOL surgery alone. Of all the MIGS devices the istent has the lowest pressure lowering capacity. Some surgeons actually place 2 istents at the time of surgery.