No need for pupil expansion rings or iris hooks for many cases (full video below)
Yesterday’s video about dealing with the small pupil in pseudo-exfoliation cataract surgery showed a specialized technique for just a few seconds: Pupil Stretching. Let’s explore that technique in more detail today.
The typical cataract has a diameter of about 10 mm and it has to come out of the eye, through the capsulorhexis and the pupil during cataract surgery. We break the cataract nucleus into pieces to aid in this, but having a smaller pupil makes the surgery significantly more challenging. If we can achieve about a 5 mm pupil and a 5 mm capsulorhexis, the surgery will be much smoother, safer for the patient, and less stressful for the surgeon. But do you need to spend the $125 (USD) or more for a single-use pupil expansion ring that has its own set of issues? Or must we use iris hooks which require extra incisions into the eye?
There is a way: pupil stretching utilizing instruments that you already have on your surgical tray. While there are instruments that are specifically designed for this purpose such as the 2, 3, and 4-prong pupil dilators made by Beehler and Moria, I prefer to simply use two choppers.
But before we get to pupil stretching, we should exhaust the other options for mydriasis:
- Topical pharmacologic dilation using standard agents (phenylephrine 2.5%, tropicamide 1%, cyclopentolate 1%) can be augmented with higher concentration medications such as phenylephrine 10%. Give these agents plenty of time to work with surgery performed about 30 minutes after instillation. Also studies have shown that pre-operative topical NSAIDs (non-steroidal anti-inflammatory drugs) can help maintain the mydriasis during surgery.
- Intra-cameral agents can also be administered directly into the anterior chamber such as preservative-free phenylephrine and lidocaine, both of which can aid in pupillary dilation. Some surgeons even use dilutions of epinephrine such as 1:5000 using balanced salt solution as the diluent.
- Visco-mydriasis means using the viscoelastic to push the iris outward and expand the pupil. This can aid in capsulorhexis creation but the effect is short lived because as soon as the viscoelastic is removed from the eye, the pupil starts to come down.
- At this point, after the above three steps have been implemented, pupil stretching becomes a reasonable option.
The technique requires two instruments, one in each hand, to securely hold the pupil margin at opposite sides and then bring them apart towards the angle of the eye. This can be repeated again after shifting the instruments 90 degrees to ensure a sufficient stretch. Now more viscoelastic can be used to hold the iris back and we can proceed with the remainder of the case. This will cause micro-tears in the sphincter which will allow the pupil to dilate more. Rarely this can cause a cosmetic defect such as corectopia.
This case is presented in its entirety to maximize learning for the surgeons in training.
Try the various techniques: pupil stretching, iris hooks, and disposable pupil expansion devices, then decide which works best for you in your particular situation.