Twenty years ago, when I did my residency training at the Jules Stein Eye Institute at the UCLA School of Medicine, I was taught to do large-incision extra-capsular cataract surgery first, before being allowed to learn phaco. Then we had to attain a reasonable level of surgical competence with scleral tunnel incisions before moving to corneal phaco incisions. This has largely gone by the wayside and most residents now start off by learning corneal phaco incisions.
But there are times when a scleral tunnel incision is not only helpful, but critical to the success of the surgery. There are cases where we do not wish to touch the cornea, such as this patient with 12-cut radial keratotomy. These kerato-refractive incisions are large and 90% depth and they are so closely spaced that we cannot safely place our phaco incision in between without intersecting them.
The scleral tunnel incision requires a few more steps and it adds a few minutes to the surgical procedure:
- Subconjunctival lidocaine should be injected at the planned incision site. Patients can also have a sub-Tenon’s or retro-bulbar block in order to give a higher level of comfort.
- A small conjunctival peritomy is performed for about 1.5 to 2 clock hours and the Tenon’s layer is focally removed.
- The crescent blade is used to make a half-scleral depth incision, parallel to the limbus and about 2 mm posterior to the corneal edge.
- The crescent blade is then used to create a tunnel into the edge of the cornea with the width being appropriate for your phaco tip.
- At the end of the procedure, the scleral tunnel is sutured with a single 10-0 nylon with the knot rotated and buried. The conjunctiva is closed with 8-0 vicryl.
During the surgery, the main challenge with the scleral tunnel is that the angle of the instruments is flatter due to the position of the incision. This is easily overcome with adjustment of the hand position.
Click below to learn how to perform phaco with a scleral tunnel incision: