If you are a sales professional or a doctor starting phacoemulsification newly, this article will help you to understand the importance of each step to cataract surgery, that is phacoemulsification (phaco surgery).
Incision
Cataract surgery or phaco surgery, starts with incision. Proper wound construction is of utmost importance as it has a direct impact on fluidic balance, post operative wound healing, and astigmatism. All these together lead to a good visual outcome after surgery.
Fluidic Balance - A rugged incision with poor wound apposition could lead to higher overflow than inflow that result in chamber imbalance during nucleus removal or I/A. Across the phaco surgery, the goal is to maintain a stable chamber. Chamber stability is lost due to a leaky incision that results from microscopic tears. Thus, the anterior chamber may be severely under-pressurized leading to shallowing of chamber, forward movement of iris, lens and posterior capsule. The forward movement of posterior capsule may lead to a rupture.
How will you notice fluidic imbalance during surgery? How can you pick up the signs that suggest chamber instability?
Fluidic imbalance can be recognized by noticing the fluctuation or bouncing movement of iris.
Apart from intraoperative complication, a poorly constructed incision also leads to a post operative leaking incision, as such incisions are not self-sealing. This increases the risk of infection and drop of IOP resulting in ocular hypotony, corneal folds and poor vision.
What would you watch during the incision construction?
Position, location and architecture of the incision is important to observe. Incisions can be positioned in the clear cornea, limbus or sclera. Most surgeons today perform clear corneal or near clear corneal incision. According to Dr Uday Devgan, an ideal incision will intersect the limbal vessels and be of an appropriate tunnel length. A tunnel that just knicks the limbus helps to be self sealing due to the wound healing nature of blood vessels.
What should be the ideal tunnel length of the incision?
An appropriate tunnel length is one which achieves a square shaped incision. The width of the incision is determined by the slit knife. But to achieve the appropriate tunnel length, the blade should advance in a way that it should have an equal thickness of roof and floor of the incision. That is the blade should travel parallel to the iris, before it finally pierces through the Descemet membrane to appear in the anterior chamber. A square shaped incision helps the surgeon to access the nuclues pieces easily, without significantly stretching the incision. A too short tunnel length may lead to outflow of BSS easily through the incision.
What should you observe in the incision architecture?
The internal architecture of the incision is crucial to achieve a self sealing incision. Incisions can be a single plane, two plane, or a three plane incision. While a single plane incision is easy to achieve, it may not be the most effective to prevent outflow of fluid through incision during the phaco process. Therefore, a two or three plane incision that provides better resistance against escape of fluid during surgery may be more efficient. Several studies have shown that a three plane stepped incision may provide a better wound integrity and resist leakage (1)
Viscoelastic injection:
What are the major functions of viscoelastics? Why do you see surgeons injecting viscoelastics before capsulorhexis?
OVD protect the corneal endothelium and other ocular tissue from mechanical trauma, like trauma from manipulation of instruments. Another major function of OVD is to form the anterior chamber and create space. You will see that the surgeon injects viscoelastic just before the rhexis, to form the anterior chamber and create a tamponade effect on the lens so that the lens is flat. This ensures that the human lens (that has a convex shape) is stable enough for the surgeon to create the rhexis and avoid rhexis spiral or run out.
Is there a specific way in injecting viscoelastic in the capsular bag prior to the rhexis?
Viscoelastic is often injected by going to the opposite end of the incision (12-o-clock) and slowly injecting viscoelastic while regressing the cannula from the eye through the incision. This technique often helps in removing any air bubble that is left trapped in the anterior chamber. Failure to remove air bubble prior to rhexis may lead to chamber instability and rhexis complication. This technique is also helpful in case the surgeon has used a blue dye to coat the anterior capsule prior to the rhexis.
Capsulorhexis:
Why is capsulorhexis considered as one of the most important step of cataract surgery?
Size and centration of the capsulorhexis determines not only the lens centration, and effective lens position after the surgery, but also determines the post operative opacification rates after surgery. Sir David Apple spelt out six factors influencing the migration of lens epithelial cells. Remember how capsulorhexis is one of the most important surgical factor to reduce PCO.
What is the ideal rhexis size according to Sir David Apple’s research?
The ideal rhexis size is .5 mm to 1mm short of the optic size of the IOL. This is important to have a shrink wrap effect of the capsule on the anterior optic of the IOL to reduce epithelial cell proliferation.
Basic Steps:
1. Puncture and tear the capsule (use 27 or 30 ga needle)
2. Spiral out to desired diameter / tear tangentially, not radially.
3. Finish up by connecting the end to the beginning.
Hydrodissection:
What is hydrodissection? What is the goal of hydrodissection?
Hydrodissection is the separation of the nuclues from the cortex to facilitate mobilisation and easy removal of the nuclues pieces. Hydrodissection enhances followability of the nuclues pieces.
You will find a 26g or 27g cannula being most commonly used to perform this step. This cannula is mounted on a 1ml or 2ml of plastic syringe. Howard Fine in 1991, described the hydrodissection procesdure that is almost universally followed worldwide. The cannula is passed into the fornix area ( the junction between the anterior and posterior capsule leaflet) after tenting the anteior capsule. A small amount of fluid is then passed slowly and gently and the lens is tapped to let the fluid pass through the posterior lens and capsule. A fluid wave passing across will be seen and this will result in the anterior chamber shallowing.
This process is repeated several times at the 2 o clock and 10 o clock positions, ideally.
The two cardinal sign of hydrodissectin are:
a) Fluid wave behind the nucleus.
b) A small lift or proloapse of nuclues.
What is the proof of an adequate hydrodissection? That is how shall the surgeon ensure that the lens and the cortex are adequately separated?
As the surgeon rotates the nucleus it should rotate freely. This indicates that the hydrodissection has been achieved adequately.
In which cases will the surgeon not do a hydrodissection?
Posterior polar cataract, as a fluid wave can rupture the weak posterior capsule.that in posterior polar cataracts, hydrodissection is contraindicated. Instead of hydrodissection, hydrodelineation is practiced. With hydrodelineation, a separation between endonucleus and epinucleus is achieved. As the separation of the two is achieved, a golden ring may appear signifying a complete separation of endonucleus from the epinucleus.
Phacoemulsification:
Understand that the three basic objectives that phacoemulsification process must satisfy.
a. It must not produce wound burn or thermal injury to the incision site
b. It must not lead to chamber imbalance or anterior chamber shallowing
c. It must not be associated with chattering and turbulence.
What are the signs of wound burn during phaco? How will you identify this complication in the OR?
A warning sign is a white milky appearance around the phaco tip at the incision site. Wound gaping may be another additional sign of thermal injury, though wound gaping is often associated with a poor wound construction. This can be associated with a delayed wound healing, and post operative incision leakage. Suturing in such cases may be essential.
How will you recognize chamber instability and fluctuation during phaco?
Bouncing of the iris may be a clear indication of chamber shallowing and fluidic imbalance. Intraoperative AC instablility has been shown to increase surgery induced inflammation(2) and lead to post operative complications such as PVD, retinal detachment and macula edema.
What could be some of the reasons for chamber shallowing?
Chamber shallowing could be due to a variety of reasons from air bubble in the phaco tubing to very high vacuum and aspiration flow rate, from a large incision size to an over sized bore of the phaco tip (smaller gauge phaco tip provides better chambe stability but is associated with more tip blockage and reduced holding capability while during chopping).
Irigation and Aspiration:
What is the importance of I/A in phacoemulsification?
I/A is one of the three surgical related factors to reduce PCO as pointed out by Sir David Apple. Failure to do a complete and comprehensive cortical clean up may result in an early and rapid ongrowth of lens epithelial cell proliferation after cataract surgery.
Other than the straight or bent shaped I/A tip, what are the other types of I/A?
Bimanual I/A and Simcoe. Some surgeons prefer to use bimanual I/A as it is easier to remove sub incisional cortex and may be associated with less wound distortion. Regardless of the type of I/A used, it is critical that the surgeon enters the anterior chamber with the aspiration port facing up. The surgeon usually engage the cortical material going near to the capsule with low vacuum. As he has engaged the cortical material, he pulls it to the center of the bag and gently steps up the vacuum.
Lens Insertion:
Safe, controlled and predictable insertion of IOL in the capsular bag is the goal. Surgeons are increasingly demanding a pre loaded delivery system that can help avoid scratch marks and address sterility issues. However, not all preloaded delivery systems behave in a safe, predictable and controlled manner. One of the situations that we commonly observe is – the leading haptic coming out in different shapes and forms other than being tucked on the IOL optic. This results in the surgeon performing additional maneuvering and manipulation techniques resulting sometimes trauma to other intra ocular structures, like the iris. This is particularly true in case of a constricted pupil.
Other than the above situation, leading haptics with competition lenses are often tucked between the plunger and the nozzle. This is a potentially hazardous situation that can lead to haptic damage, or even breakage.
Still another situation is when often the plunger misses the IOL while advancing leaving the IOL behind in the process.
What are some challenges related to manual loading of lens?
Manual loading of lens and handling with forceps can lead to scratch marks as shown in the picture here. Above intraoperative pictures show large scratch marks from the forcep. The below retroillumination image of the same lens postoperatively.
What are some additional observations related to IOL implantation?
IOL centration after implantation is important, especially with presbyopia correcting IOLs. Surgeon may center the lens in the center of pupil, or limbal center, or on the purkinje reflex.
In case of TORIC IOL, gross and final alignment is important. Gross alignment is achieved when the surgeon stops 150 to 200 short of the final alignment axis to remove viscoelastic from underneath the IOL. Final alignment is then done after rotating the IOL clockwise for a C-loop haptic.
Wound Closure:
What are some of the additional steps that the surgeon may perform before stromal hydration?
A. Ensuring no retained viscoelastic in the bag, and underneath the IOL.
B. Retained lens fragments are often left under the iris, and are a source of post operative inflammation.
Stromal hydration is sufficient in majority of cases to close the incision and prevent post operative leakage. Stromal hydration swells the corneal lamellae and force the incision to close.
It is done by injecting BSS with a 27g cannula in the corners of the incision and the internal roof of the incision. Stromal hydration involves the following –
Hydrating the side edges of the incision. This ensures that the fluid stream is near perpendicular to the edge of the incision. The fluid is then pushed into the mid anterior stroma. This would ensure that the hydration and resultant whitening is confined to the incisional area.
Hydrating the incisional roof of the anterior to mid stroma with the cannula pointing towards the roof. Care should be taken not to advance the cannula too much so that a Descemet detachment does not appear.
In cases of Toric IOLs, care should be taken not to over inflate the stroma with a lot of infusion of BSS as this may lead to lens rotation. A large infusion of BSS into the stroma may also cause a prolonged large degree of astigmatism post operatively.
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1. May W, Castro-Combs J, Camacho W, Wittmann P, Behrens A. Analysis of clear corneal incision integrity in an ex vivo model. J Cataract Refract Surg. 2008;34(6):1013–1018.
2. Effect of Anterior Chamber Instability during Phacoemulsification Combined with Intraocular Lens Implantation; https://doi.org/10.1155/2022/2848565
3. Influence of Intra Ocular Lens Material and Design on Postoperative Intracapsular Cellular Reactivity, David Apple; https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1298231/pdf/taos00001-0257.pdf
