Sometimes, the best approach to expanding a small pupil for cataract surgery is to use iris hooks. These are small, plastic retractors which can be placed via their own tiny incisions to temporarily expand the pupil and hold the iris tissue out of the way during cataract surgery.
There are some important pearls for their use:
- create a small limbal incision, narrower than a typical paracentesis incision, by not fully advancing your usual side-port blade
- angle the incision from the limbus down to the pupil margin. this slight downward angle is different than a typical paracentesis when the blade tends to be parallel to the iris or angled slightly up
- have a sufficient fill of viscoelastic in the anterior chamber
- you can use either 4 or 5 iris hooks to create a square or pentagonal opening, respectively
- place all hooks on the cornea first, then begin inserting them into the eye, one by one
- place one hook around the pupil margin and then slide the retaining collar only part way down the shaft. do not advance to full tension until all 4 hooks are placed.
- now you can tighten each hook to retract the iris and expand the pupil
In this case there is also some important learning regarding the white cataract. First, we must remember to stain the anterior lens capsule with trypan blue dye prior to instilling viscoelastic which coats the capsule and prevents the dye from sticking. This can be done with a small pupil by placing the trypan blue dye, drop by drop, under the iris in the four quadrants. Then viscoelastic can be used to fill the anterior chamber. You will see in this video that when the iris hooks expand the pupil, the underlying anterior capsule is nicely stained blue.
This cataract is also intumescent which means that there is a high risk of the dreaded Argentinian Flag Sign when the capsular tear extends rapidly to the zonular attachment and even to the posterior capsule. In this case we use the Double Capsulorhexis technique to avoid this. This involves keeping the anterior chamber pressure higher than the pressure within the capsular bag using viscoelastic. This will help prevent egress of the liquified lens cortex and will allow us to create a small capsulorhexis.
With this completed, we can then rock the endo-nucleus and release all the trapped liquified lens cortex material. After the lens capsular bag has been decompressed, we can then create the main phaco incision and then expand the capsulorhexis into the desired 5 mm diameter. Note that you cannot achieve a sufficiently high anterior chamber pressure for this technique if you have already created the main phaco incision. This is why we delay the main incision until after creating the first, small capsulorhexis.
At the end of the surgery, the easiest way to remove the iris hooks is simply to give them a quick tug and pull them out. No need to loosen the stay collars. Because the hooks are flexible plastic, they will simply bend and release the iris without damage.
Click below to learn from this important case: