(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_8) contains supplementary material, which is available to authorized users.
After hydrodissection, the lens nucleus is ready for removal. The whole lens, however, is too large to be expressed through the capsulorhexis opening. To avoid over-stretching and tearing the capsulorhexis, the lens must be divided into smaller sized pieces. Each fragment must be sized for safe extraction from the bag in preparation for subsequent phacoemulsification. Dexterity, of both hands and feet, is required during phacoemulsification of the lens nucleus. And continuous decision-making is necessary to decide how best to achieve lens disassembly. Although there are a plethora of phacoemulsification techniques described, the aim, simply put, is to develop the skills of the ‘lazy phaco surgeon’—that is, to learn how to do as little as possible to achieve lens extraction from the eye.
Learning how to phaco is dependent on the Trainer’s ability to instruct and the ability of the Trainee to follow instruction. Since only one person can perform surgery at any given time, it is necessary to make the learning process proceed smoothly, so that the stress of operating is minimised for all involved. Surgery needs to remain controlled and performed within the limits of the novice surgeon. The rate of progression will depend on what the Trainer feels is safe and at which point they feel intervention is needed.
Traditionally, the sequence of phaco surgery is taught starting with a whole lens in situ, with step-by-step techniques acquired to manipulate, split and remove the lens fragments. However, to improve the rate of learning a rear-ended approach to this phaco sequence can be applied, namely:
The fundamentals for each step have been broken down, starting with the small fragment removal module. In order to commence training at the small fragment removal stage of surgery, the Trainer is required to perform lens nucleus disassembly before handover to the novice.
The primary aim at this stage is for novices to gain essential phaco, fragment rotation and foot pedal skills without having to deal with whole lens disassembly or the debulking of large fragments.
Those already familiar with phaco may prefer to focus on any of the individual phaco module chapters. It is recommended, however, that all the chapters are used in conjunction with each other, so that all the principles described are understood. The principles can be applied when performing surgery, or recognised and appreciated if acting as an observer.
Assumptions made in relation to this phacoemulsification training module are shown in Box 8.1.
Box 8.1 Assumptions Made in Relation to This Training Module
- 1.
Case selected for initial phacoemulsification will be chosen by the Trainer.
- 2.
The Trainee can perform irrigation/aspiration, lens insertion, capsulorhexis, hydrodissection and can ‘palm’ an instrument.
- 3.
For the first few cases of small fragment phacoemulsification training, the Trainer will perform the initial preparation up to the fragment extraction stage.
- 4.
The Trainee may continue to perform modular aspects of capsulorhexis and hydrodissection on separate or the same case and eventually be able to perform all steps learnt in sequence.
Note: although the images chosen for this chapter are intended to aid understanding of various surgical principles, they may not have been performed during the small fragment removal stage of surgery.
8.1 Terminology
8.1.1 The Phaco Probe
A plastic sleeve covers the metal phaco probe . The sleeve has two irrigation apertures and is rotated to ensure both irrigation fluid jets exit the holes horizontally. The ‘mouth’ is the exposed phaco tip aperture that engages and removes lens material. The probe maintains this ‘primary’ position when held as described within the eye (Fig. 8.1).
Fig. 8.1
Phaco probe in primary position. Phaco tip and mouth (solid arrow), irrigation aperture (arrow head), phaco sleeve (open arrow)
In side profile, the exposed phaco tip shape is shorter in length superiorly (Fig. 8.2).
Fig. 8.2
Phaco tip—side profile in primary position. Mouth of phaco tip (arrow head), inferior length of tip (open arrow) is longer than superior aspect, sleeve irrigation aperture (solid arrow)
In the descriptions below the term phaco on refers to the application of ultrasonic phacoemulsification. Phaco off implies the ultrasonic phacoemulsification should be turned off.
8.1.2 Lens Fragment Anatomy
After division of the nucleus, lens fragments are pyramid shaped with an apex and a curvilinear base. At the widest point of the base the fragment has two shoulders (Fig. 8.3).
Fig. 8.3
Lens segment . Apex (star), shoulder (arrow), base of segment (arrow head), capsulorhexis outline (dotted line)
When a fragment lies within the capsule bag, the base and shoulders remain under the rhexis edge and will need to be freed before phacoemulsification can occur.
If the lens is divided into two halves, each hemi-nucleus will have a curved base, two shoulders but no apex. If a hemi-nucleus is chosen for phacoemulsification, it will be necessary to extract one shoulder from the capsule bag and then the other, otherwise the hemi-nucleus may not fit through the rhexis opening.
8.1.3 Lens Fragment Capture
Fragment capture refers to the situation where a fragment is firmly held by the phaco tip ready for manipulation or phacoemulsification.
8.1.4 The Safe Zone
The safe zone is the central area within the anterior chamber (Fig. 8.4). It is recommended lens fragments are manoeuvred into, and phacoemulsified within, the safe zone.
Fig. 8.4
Phacoemulsification safe zone . Capsulorhexis outline (dotted line), safe zone (solid circle), corneal section (solid line)
Pulling the phaco tip back (towards the corneal section), and keeping the fragment in the centre of the safe zone, maximises the free space surrounding the captured fragment in preparation for phacoemulsification removal. It reduces the likelihood of accidental phaco damage to the rhexis edge, iris or the endothelium.
8.2 Foot Pedal Control
Two foot pedal modes are available to control the amount of aspiration and phacoemulsification: linear and dual-linear. Linear control, akin to a car accelerator pedal, allows the surgeon to control the three variables needed to remove the nucleus; irrigation, aspiration and phacoemulsification. The programmed progressive change automatically occurs as the foot pedal is depressed (Fig. 8.5). Common pre-programmed machine settings, referred to as ‘phaco 1’ and ‘phaco 2’, are set up by the surgeon according to their aspiration and phaco power preference. Commonly, phaco 1 is used for nucleus grooving and cracking, whilst phaco 2 is for fragment capture and phacoemulsification. It is necessary to actively pause during surgery and switch from phaco 1 to phaco 2 as required.
Fig. 8.5
Linear foot pedal control. (i) Irrigation, (a) aspiration plus irrigation, (p) phacoemulsification plus irrigation and aspiration
In dual-linear mode, both the vertical and the horizontal yaw foot pedal moment is used to control the three variables. One direction is set up to control phacoemulsification whilst the other direction controls irrigation and aspiration. This allows the surgeon to toggle between the maximum aspiration and the maximum phacoemulsification, applied independently of each other. There is a learning curve when using dual-linear mode, but it is more flexible when applying aspiration and phacoemulsification. Novice surgeons usually start training on a linear setting, but this will depend on their Trainer.
The phaco machine can be set to allow continuous irrigation. This is a useful setting that ensures the anterior chamber is maintained once irrigation has been initiated. Irrigation will continue to flow and has to be consciously stopped, using the foot pedal, whenever the phaco probe is removed from the eye. Failure to remember this will result in a very wet operating area.
It is recommended that novice surgeons become familiar with the phaco machine sounds (for irrigation, aspiration and phaco) emitted by the brand of phaco machine used in their facility.
8.3 Insertion of the Phaco Probe
Insertion of the phaco tip into the eye is the first step in phacoemulsification surgery. A proficient, smooth technique is required. Technical barriers to overcome include: initial resistance of the corneal wound, accidentally catching the curved edge of the phaco sleeve irrigation ports on the lip of the corneal section, and potential anterior chamber collapse. The probe insertion technique can be broken down into steps:
8.3.1 Step 1
Ensure the irrigation is working by briefly wetting the cornea and then stop irrigating. Position the phaco probe so that it is held near the corneal incision in anticipation of the next step (Fig. 8.6).
Fig. 8.6
Phaco probe insertion step 1
8.3.2 Step 2
Hold the forceps in the non-dominant hand. Approach the corneal incision from a slight angle (so as to not obscure the view) and use one side of the forceps to gently lift the anterior lip of the corneal section. This will cause the wound to gape, ready for the next step (Fig. 8.7). If possible, avoid gripping the corneal section with the teeth of the forceps as this will induce micro-trauma.
