(1)
Newcastle Eye Centre Royal Victoria Infirmary, Newcastle upon Tyne, UK
Electronic Supplementary Material
The online version of this chapter (doi:10.1007/978-3-319-59924-3_13) contains supplementary material, which is available to authorized users.
The main corneal and side-port paracentesis incisions are the last modules for the Trainee to learn before combining all the cataract steps to perform whole case surgery. This chapter discusses the paracentesis incision whilst Chap. 14 deals with the main incision. Rear-ended modular training provides Trainees with the opportunity to observe many corneal side port paracentesis incisions before their first attempt. However, it is only natural to remain hesitant about holding a blade near the eye and creating an incision. The paracentesis step can be learnt as a separate step to the main incision providing the opportunity to quickly overcome this anxiety.
Alternatively, once the principles are understood, and several paracentesis attempts have been made, the two modules could be practised simultaneously.
13.1 The Paracentesis
The paracentesis is also referred to as the side-port. It is an incision made to accommodate a second instrument (the phacoemulsification probe is the primary instrument) or can be used to inject viscoelastic or other fluids into the eye. The side-port is usually created 60- to 90-degrees away from the main incision, however the location can vary according to the preference of the surgeon (at this stage of rear-ended modular training, the Trainee will appreciate the standard paracentesis incision location usually made by their Trainer).
The side-port wound is created by pushing a blade through the cornea to create an internal and external ostium (Fig. 13.1). The width of the second instrument, at the level of the shaft, dictates the diameter of the paracentesis. A small size allows the incision to self-seal, but it is common for surgeons to hydrate the side port wound at the end of surgery to ensure it does not leak in the immediate post operative period.
Fig. 13.1
Paracentesis side port. External ostium (solid arrow), internal ostium (open arrow)
Trainees should aim to reproduce a consistent incision in every case, but commonly encounter problems as they are learning. These may include:
- 1.
Paracentesis is too wide.
This allows excessive fluid to escape from the anterior chamber during phaco surgery. It can also promote iris prolapse, anterior chamber shallowing and lens fragment trapping in the incision or the iridocorneal angle.
- 2.
Paracentesis is too narrow.
This can hinder complete insertion of the second instrument, or cause distortion of the corneal tissue during insertion.
- 3.
Paracentesis is too long.
A long side-port tunnel runs the risk of second instrument insertion difficulty into the anterior chamber and possible corneal distortion as the instrument is manipulated.
- 4.
Paracentesis is too short.
This can prevent self-sealing and increase the risk of pathogenic organisms gaining entry into the eye.
13.2 Instrumentation
Various blades can be chosen to make the side-port incision. These include: a diamond blade, a microvitreoretinal (MVR) blade , a 30-degree blade or even the disposable keratome used to construct the main incision. The choice of instrument depends on surgeon preference and will be dictated by the Trainer. In order to illustrate the basic principles, a 30-degree tapered blade is used in the examples outlined in this chapter.
The tip of the blade has both cutting and non-cutting edges (Fig. 13.2). When creating the side port, the applied pressure should be directed towards the cutting edge. If the non-cutting surface is inadvertently used, the blade will cause rotation of the eye and require a lot of counter traction to keep the eye steady. As more force is applied, the direction of the applied pressure will eventually alter towards the cutting-edge surface. At this point the blade may rapidly cut through the cornea. Uncontrolled entry into the eye in this manner can cause an unintentional large, leaky wound. The blade may also damage the iris or lens capsule.
