Overview of Phacoemulsification
Cataract surgery, a common procedure these days, uses modern techniques to restore vision for individuals with cataracts. Cataracts can form due to various reasons and cause blurred vision. Doctors restore sight by using a technique called phacoemulsification, first introduced in 1948 by Charles D Kelman. This technique was inspired by a dental procedure that used ultrasound energy to remove tooth enamel and debris. In a similar way, Kelman used a small, hollow needle with ultrasound power to remove the affected lens of the eye.
This technique involves several steps. Firstly, a surgeon uses a system that combines water irrigation and suction to extract the cloudy lens and its fragments. There was initially some hesitation to adopt this method due to the increased risk of complications and the need for a larger incision (cut) to insert a specific type of lens. However, the technique gained popularity in 1980 thanks to several advancements that made the procedure much safer and more effective.
During phacoemulsification, the eye surgeon creates a tiny cut in the eye with a precise instrument, before staining the front layer of the lens for better visibility. The surgeon then removes the lense’s cloudy core (or nucleus) with an ultrasound-powered device. After this is done, any leftover bits of the lens are removed from the ‘bag’ that used to contain the lens, and a new, artificial lens is put in that folds to fit within the small incision.
The surgery is typically a routine procedure done under local anesthesia (numbing of the area), allowing patients to go home on the same day. Patients usually start to notice significant improvements in their vision from the very next day after the operation. The vision continues to improve over the course of four to six weeks as the eye adjusts to its new lens.
Anatomy and Physiology of Phacoemulsification
The procedure called phacoemulsification, used in cataract surgery, uses an irrigation and aspirating (suction) feature to function.
Irrigation
Irrigation in this context refers to the continuous flow of fluid that passes through a tip during the surgery. This process helps to maintain balance within the eye and helps to keep the front part of the eye, or the anterior chamber, stable during the procedure. This flow of fluid also cools down the ultrasound tip, which helps to minimize heat generation and prevent any tissue damage. The amount of fluid pressure can be adjusted by changing the height of the bottle. The force of gravity is essential in this process. In some machines, a bag filled with saline solution helps to support the irrigation pressure. To help keep the pupil wide during surgery, medications that dilate the pupil can be added in the irrigation.
Aspiration
Good understanding of the aspiration system is vital to perform this surgery effectively. Aspiration refers to the process when the cataract or the lens matter is drawn in towards the instrument’s tip. Surgeons can use the active fluid inside the eye to perform the surgery without damaging surrounding tissues such as the iris and the lens capsule. The amount of suction applied, or the vacuum, governs how tightly the lens matter is held to the instrument’s tip.
Aspiration Pumps
There are two types of aspiration pumps: peristaltic pumps and vacuum pumps. The peristaltic pump moves fluid through the machine by employing flexible tubes mounted on rollers. As the rollers move, they push the fluid through the tubing. The flow-rate can be manually controlled by pressing a foot pedal. Whereas, a vacuum pump works on the principle of venturi effect. In other words, it creates a vacuum that is proportional to the rate of the fluid flow. The suction can be manually controlled using the foot pedal.
Glossary of Terms Used in Phacoemulsification
Aspiration Flow Rate: This is the speed at which the fluid and lens matter are removed from the eye after passing through the tube.
Aspiration Port: This is an opening in front of the surgical instrument, which helps remove the solution and lens material from the eye.
Compliance: This term is used to describe how pliable the surgical tubing can become when vacuum is applied.
Followability: This term refers to how fast the lens material or fragments are attracted towards the aspiration port.
Infusion Pressure: This refers to the fluid pressure inside the tube.
Irrigation: This is amount of fluid that is being introduced inside the eye.
Occlusion: This refers to a blockage in the aspiration tube or port due to the buildup of vacuum.
Rise Time: This is the time it takes for the vacuum to build once the aspiration port is blocked.
Post-occlusion Surge: This phenomenon occurs when occlusion is broken and fluid rushes from the high-pressure zone to the low pressure area, potentially causing the front part of the eye to collapse.
Vacuum: This is the amount of opposing force created in the tube, measured in mmHg.
Ultrasound Concepts
Cavitation: This means the formation of gas bubbles in the front part of the eye due to pressure changes at the surgical tip.
Chatter: This is when the lens fragments are pushed away from the surgical tip until the vacuum level is reached again to neutralize the repulsive force.
Duty Cycle: This is the ratio of power-on time to the total time.
Why do People Need Phacoemulsification
Phacoemulsification is a procedure to deal with cataracts, which can blur your vision. This operation is required when a clouding in the eye’s lens starts to affect your daily life. If you find it hard to carry out your everyday activities, see things near or at a distance, experience light sensitivity, or double vision in one eye, you might need this procedure. It is also performed if you start seeing colored halos, have less sharp vision, or observe a white reflection in the middle of your eye.[21]
There are various types of cataracts, all of which require similar treatment. Along with common ones like nuclear, cortical, and posterior subcapsular cataracts, brown, mature, and traumatic cataracts also require surgery. Even a slight cloudiness in the lens (nuclear opalescence), or an off-center cataract supported by special devices (subluxated cataract) needs surgical attention. For some jobs, like airplane pilots, drivers, military personnel, or those operating complicated machinery, maintaining an excellent vision is an absolute necessity.[22]
Every type of cataract that disrupts your ability to see clearly is why phacoemulsification is needed. Cataracts can present as blurred or less sharp vision, insight discomfort, seeing colored light rings, double view, diminished vision function, and decrease in contrast perception. While cortical cataracts grow moderately and only slightly affect near and distant vision, nuclear ones grow slowly but significantly affect your ability to see far-off objects. The third, posterior subcapsular cataracts, grow inconsistently but can significantly affect vision up close.[21]
Before the operation, doctors will thoroughly examine you to rule out any severe conditions. They will look for underlying issues like diabetes, high blood pressure, heart disease, pulmonary disease, bleeding disorders, adrenal suppression, or neurological problems like Alzheimer’s or Parkinson’s. They will also ensure that you don’t have a history of allergies or reaction to drugs involved in this procedure. Patients taking certain medications like prazosin, terazosin, alfuzosin, which affect blood pressure, need additional attention as these can cause complications during the surgery.
Moreover, your doctor will examine the structures at the front of your eye, including your eyelids, cornea, and iris, to ensure there isn’t any inflammation or infection present. The back of your eye will also be examined to rule out conditions like diabetic retinopathy, hypertension effects on the retina, macular degeneration, or a detached retina, which may affect the outcome of the surgery.[23]
When a Person Should Avoid Phacoemulsification
There are several reasons why a person might not be able to undergo a procedure called phacoemulsification, which is a method used to remove cataracts:
For starters, if a person doesn’t want to have the surgery, it can’t be carried out. Also, if a person has many other health issues – also known as systemic comorbidities – they might not be a suitable candidate for the procedure.
If a person is happy with their vision when using glasses, they may decide not to undergo the surgery. Similarly, if the surgery won’t improve the person’s vision, it may not be necessary to have the procedure.
The person also has to freely give their consent for the surgery to go ahead. This is an important part of any medical procedure and a legal requirement. Lastly, if it’s not possible for the person to receive care after the surgery, it might not be safe or beneficial for them to have the procedure.
Equipment used for Phacoemulsification
Phacoemulsification is a modern method used to remove cataracts, which are cloudy patches in the eye that can cause blurry vision. The process uses ultrasound waves to break up the cataracts, and then a small vacuum to clean up the bits. It also uses a system of water movement to wash the eye and remove any leftover gel-like material in the eye. The main tool in this procedure is the handpiece, which performs the breaking and cleaning actions. It works a bit like a jackhammer, with a part inside moving back and forth rapidly. This part is made of special crystals that create the ultrasound energy.
These rapidly moving crystals generate the energy that’s used to break up the cataract. The amount of movement depends on how much energy the machine is set to use. This movement also creates tiny bubbles that help break the cataract apart. This is called cavitation. The tip of the handpiece can vibrate in a straight line or side-to-side, both of which help in breaking up the cataract.
During the procedure, the surgeon uses a foot pedal to control the machine. It’s like a car’s gas pedal – the amount of pressure changes the power. This foot pedal has three settings: one for water movement, one for water movement and suction, and another for suction and ultrasound energy. The machine can either have a constant energy level, or it can change based on how much the pedal is pressed.
Delivering the ultrasound energy to the eye must be done carefully. Too much energy can cause heat and damage the inside of the eye. Therefore, the surgeon must use the ultrasound energy wisely and safely. They can choose to deliver the energy in pulses, instead of a constant flow, to decrease the chance of heating the eye. Changing the size, angle, or motion of the handpiece tip can also make the process more efficient and safer.
There are lots of different handpiece tips. Each has a different angle edge, from straight to a very pointed 60 degrees. A sharper tip can hold and cut the cataract better, but it might be harder to get a full suction effect. The tip can also be shaped differently: it could be straight, round, oval or flared.
The energy can be delivered in different ways. In pulse mode, the energy is delivered in pulses when the foot pedal is at its highest setting. It also has off periods where no energy is delivered. The energy of each pulse increases as the pedal is pushed further. In burst mode, the energy is delivered in pre-set bursts separated by periods of decreasing energy. With the pedal fully down, the energy is delivered continuously, not in pulses or bursts. This mode is useful for inserting the tip in the cataract and helping to break it up.
There are also different way the handpiece can move to break up the cataract. In torsional phacoemulsification, the crystals inside the handpiece create side-to-side movements, especially when using a bent tip. This movement is efficient at cutting the cataract and helps in its removal. In elliptical phacoemulsification, the handpiece moves in both a side-to-side and straight line motion, creating an oval shape that increases the efficiency of cataract removal.
Preparing for Phacoemulsification
Testing how well you see is an important part of diagnosing eye problems. The Snellen test is a common way to do this. You may be asked to read letters, symbols, or numbers from different distances without your glasses or contact lenses, and then again with them. Sometimes, eye doctors may also use a Jaeger’s chart to test your ability to see things up close. If you have a type of cataract that affects the back of your eye lens, your eyesight might actually improve once your eyes are dilated. If your cataract is very developed or turns your eye lens brown, your doctor may check to see if light can reach your eye.
Doctors do a refraction test to measure the light your eye can bend. This helps to understand the power of Intraocular Lens (IOL) you need after the cataract surgery. Sometimes, you can get different results after surgery. The vision in both of your eyes should ideally match. But sometimes, if your good eye has vision defects, after the surgery, the vision in both your eyes may not be the same. In that case, you might need another surgery to even out your vision, or a contact lens.
Glare testing involves using a light source to check how much your vision is affected when there’s too much light. Some people may also have reduced contrast sensitivity, which means they have difficulty telling the difference between light and dark. This can be tested using special charts.
To decide the power of the IOL you need after the cataract surgery, your doctor will perform an IOL Biometry test. This involves using a formula to find out the power, size and shape of your eye and its average curvature. There are newer machines that can do this more accurately, like the IOL master 500 and 700. Various other formulas have been introduced for this over the years, and many surgeons use multiple formulas to get the most accurate result.
Surgeons use the Potential Acuity Meter to check your vision loss due to cataract changes. This test is only applicable if you can see more than a certain amount and you don’t have any other eye problems. You just have to read a brightly illuminated card through a pinhole. The test might not work properly for people with diseases like age-related macular degeneration, amblyopia, secondary glaucoma or retinal detachment.
Visual Field Testing is used to assess the field of vision i.e, how wide you can see without moving your eyes. It’s especially important for people with glaucoma – a disease that damages the optic nerve in the eye, abnormally shaped optic nerves, or retinal problems. This test can help identify any vision loss that’s not a result of cataracts. After the surgery to remove the cataract, your field of vision should improve.
Specular Microscopy is a test done to assess the cornea. Patients with certain eye conditions like Fuch dystrophy, previous trauma, or anyone who has had eye surgery before, may need to have this test done. The exam can inform the patients about the risk of excessive fluid buildup in the cornea. Cataract surgery can cause loss of corneal cells, so patients with less number of these cells should take extra precautions during surgery.
Pachymetry is a test to measure the thickness of your cornea. Patients with a thicker cornea are at a higher risk of fluid buildup in the cornea.
Macular Function Tests use Optical coherence tomography to create images of the eye. It helps to identify problems like fluid build-up, holes, pulling and sticking of the macula. The macula is a small spot in the center of the retina that controls detailed, straight-ahead vision. The test is being increasingly used these days for patients undergoing cataract surgery.
How is Phacoemulsification performed
Phacoemulsification, often known as “phaco,” is a surgical procedure to remove cataracts. These are the key stages involved in a phacoemulsification surgery. Remember, all actions will be performed by your surgeon, but this will help you understand what’s happening.
Marking the Eye and Time-Out: To ensure the correct eye is operated on, your doctor will mark the eye with a temporary pen or sticker. They will also double-check vital details like your name and age.
Globe Exposure: Once you’ve been given anesthesia and made comfortable, your doctor will use a tool called a speculum to hold your eyelids open. This allows your doctor to access your eye easily.
Side Port Incisions (Paracentesis): Next, small incisions are made around your cornea to insert specialized instruments for the surgery.
Clear Corneal Incision: A bigger incision than the previous ones is made on your cornea. This will allow your doctor to insert the phaco, a surgical tool used in the procedure.
Sclerocorneal Tunnel Incision: This type of incision is used in particular cases where a more rigid artificial lens (IOL) will be inserted.
Continuous Curvilinear Capsulorrhexis (CCC): In this step, your doctor pulls away part of the layer covering your lens (the lens capsule) to allow them to reach the cataract.
Hydrodissection: A liquid is injected into your eye to separate the cloudy lens (the cataract) from its surrounding layer. With the lens and layer separated, the cataract can be freely moved and broken down.
Hydrodelineation: In specific cases, fluid is separately inserted to distinguish the softer inner part of the cataract from the harder outer shell.
Nuclear Rotation: Your surgeon will rotate the lens (nucleus) within the capsule. This rotation facilitates the chopping up of the cataract during the procedure.
Techniques of Nucleus Break and Removal: After rotating your lens, various techniques will be used to break the cataract and then remove it. The approach selected can depend on the type of cataract and the patient.
Plane of Phacoemulsification: Finally, the emulsification (which could be thought of as the breaking down of the cataract using tiny ultrasonic waves) will be performed. The emulsification can happen in various parts of the eye depending upon what is best for you and your eye condition.
It is crucial to note that although the name suggests differently, your eye is not being emulsified. Instead, the cataract is being emulsified, allowing the cataract parts to be removed, leaving behind a clear lens.
These detailed stages may seem complex, but phacoemulsification surgery is a routine procedure performed by experienced surgeons. This step-by-step breakdown is meant to help you understand the process, not as a guide for performing the surgery.
Possible Complications of Phacoemulsification
During surgery, various issues can arise that may cause complications, including:
* Wound leak: Fluid seeps from the operated area.
* Wound dehiscence: The surgical wound opens up again.
* Wound burn: Accidental burn of the skin around the surgical site.
* Descemet membrane detachment: The thin, protective layer of the cornea (the clear front part of the eye) separates.
* Corneal burn: The cornea gets burnt.
* Iridodialysis: The colored part of your eye (iris) detaches from its surrounding tissue.
* Rhexis extension: Unexpected tear of a part in the eye during surgery.
* Zonular dialysis: The tiny fibers in your eye holding the lens in place dislocate.
* Posterior capsular tear: The bag-like tissue holding your eye’s lens gets a tear.
* Nuclear drop: The lens’ center part falls into the back of the eye.
* Retained Cortex: Not all lens material is removed during surgery.
* Vitreous prolapse: The gel-like substance inside the eye leaks into the front part of the eye.
* Choroidal detachment: The layer of blood vessels under the retina separates.
* Retinal detachment: The sensory layer at the back of the eye separates.
After surgery, you might experience the following:
* Wound leak: Same as above, fluid might leak from the surgical wound.
* Astigmatism: Your eye does not focus light evenly onto the retina, causing blurred vision.
* Striate Keratopathy: Clouding or stripes appear in the clear front part of your eye.
* Corneal edema: Swelling of the cornea.
* Pupillary block: Fluid gets trapped in the front part of your eye, causing pressure increase.
* Uveitis: Inflammation of the middle layer of your eye.
* IOL decentration: The artificial lens placed during surgery moves from its original position.
* IOL tilt: The artificial lens tilts causing the image to distort.
* IOL subluxation: The artificial lens somewhat dislocates.
* IOL dislocation: The artificial lens completely dislocates.
* Vitreous wick syndrome: Inflammation occurs as an eye’s internal fluid leaks out.
* Vitreous touch syndrome: Touching the vitreous body or gel inside the eye causes irritation or damage.
* Endophthalmitis: Inflammation of the internal part of the eye.
* Toxic anterior segment syndrome: Inflammation occurs in the eye’s front portion.
What Else Should I Know About Phacoemulsification?
Modern advancements in technology have transformed the way cataract surgeries are performed. The use of new and upgraded lenses that can be implanted into the eye during cataract surgery has made these operations the most common eye correction surgeries worldwide. As a result, there are higher expectations from patients and a greater level of expertise required from surgeons.
One key duty for all eye surgeons is to ensure every patient gets the best possible visual outcome from their cataract surgery. This means they need to explain to the patient the risks and benefits tied to the procedure. They must also educate the patient specifically about new technologies in cataract surgery, such as phacoemulsification, a modern technique that uses sound waves to break up the cataract.
Healthcare providers should assist patients in understanding the different types of foldable and upgraded lenses available, suggesting the most suitable lenses for individual patients. If any risk factors, like Fuch’s dystrophy (a condition affecting the cornea), compromised endothelium (the inner layer of the cornea), or small pupil cases are present, the doctor will discuss with the patient the need for additional instruments or products, such as iris hooks and viscoelastic devices. Similarly, if any complications arise during the operation, the doctor will explain in detail what has happened and the best way to address it, during or after the operation, to achieve the best vision possible.
It is crucial for any patient needing cataract surgery to get a detailed examination from an eye doctor. Depending on the patient’s condition, he or she may be referred to a specialized eye surgeon, especially if there are certain risk factors related to cataract surgery, such as limited pupil dilation, a history of inflamed eyes, a condition where the lens of the eye is dislocated, an opaque cornea, or secondary glaucoma. For patients who experience complications, like a capsular tear or the leakage of the gel-like vitreous substance from the back of the eye, it is important to have them assessed by a vitreoretinal surgeon who can check for other complications like the dropping of the nucleus or cortex of the lens into the vitreous cavity or separations of the retina or choroid (the vascular layer of the eye).
