Overview of Manual Small Incision Cataract Surgery
Cataracts, a condition that makes your vision blurry, are one of the most common reasons people lose their sight in a way that can be fixed. The main way to restore sight for these people is through cataract surgery, and it happens to be one of the most commonly performed eye surgeries around the world. How well people can see after the surgery and how it improves their quality of life are key factors in determining if the surgery was successful.
As time has passed, cataract surgery has seen many advancements. Improved surgical techniques, better surgical instruments, and the introduction of new drugs have all contributed to make cataract surgery less risky and more effective.
A tremendous leap forward in cataract surgery came with the introduction of a procedure called phacoemulsification in 1967, forever changing the way doctors approached these surgeries. Since the 1980s, a manual version of this surgical technique (MSICS) has been popular, especially in developing countries. This is because it maintains the great outcomes of phacoemulsification while being less expensive, taking less time, and having fewer complications in complex cases.
Over time, cataract surgery has evolved from a technique called ECCE to MSICS, and finally to phacoemulsification. The biggest benefit of MSICS over ECCE is that no stitches are needed because the incision is self-sealing.
Performed by a surgeon with lots of experience, an average SICS can take between 7 to 10 minutes. This article will also discuss the indications and contraindications for this surgery, the step-by-step process of the operation, and potential complications during and after surgery. Even though there are many forms of cataract surgery, MSICS is often chosen for high-demand situations, in developing and undeveloped countries, and for complex cataract cases. There have been many adaptations of this surgery over time, but the basic technique remains the same.
Anatomy and Physiology of Manual Small Incision Cataract Surgery
The anatomical limbus is a boundary area in your eye that serves as a transition point between the conjunctiva and cornea, and the cornea and sclera. The conjunctiva is the clear surface of your eye, while the cornea is the outermost lens that helps your eye focus, and the sclera is the white part of your eye.
At these junctions, the conjunctiva and the cornea merge, meaning they become one continuous structure. The limbus area plays an important role in changing from one structure to another, like a border between countries.
The limbus itself has different parts or boundaries:
The anterior limbal border is a ridge that forms the start of the surgical limbus zone, which is about 2 mm wide.
The blue limbal zone is a clear area that lies between the anterior and posterior borders of the limbus. Past this zone, you find the white part of your eye, the sclera.
The mid limbal line is a significant mark at the junction of the blue zone and the white sclera.
The posterior limbal border forms the end of the surgical limbus zone and is located 1 mm behind the mid-limbal line.
The white limbal zone is a 1 mm wide area located between the mid-limbal line and posterior limbal border.
The limbus plays a crucial role when doctors perform eye surgeries, as knowing precisely where these borders are on the limbus can prevent complications. For example, clear corneal incisions are made in front of the anterior limbal border, and can sometimes cause vision distortions.
On the other hand, the preferred site for eye incisions is the mid limbal line, where it is least likely to cause other issues.
Other types of incisions, like the scleral incision behind the posterior limbal border, may result in bleeding.
Why do People Need Manual Small Incision Cataract Surgery
The decision to use a surgical technique known as Manual Small Incision Cataract Surgery (MSICS) largely depends on the surgeon’s skills and the amount of experience they have in managing specific cases.
For beginner-level surgeons, MSICS is used in cases with:
– Nuclear sclerosis grade 2-3, which simply means the lens of the person’s eye is mildly to moderately clouded.
– Posterior subcapsular cataract, a type of cataract located at the back of the lens’ capsule.
– Cortical cataracts, another type of cataract that develops on the outermost edge of the lens.
On the other hand, experienced surgeons might use MSICS in a variety of more complex cases, such as:
– Severe nuclear sclerosis (grades 4 and 5), where the lens is severely clouded.
– Hard mature, brown, intumescent, or Morgagnian cataracts, which are different types of advanced cataracts.
– Traumatic cataracts, caused by an injury to the eye.
– Complicated cataracts with additional issues.
– Pseudoexfoliation, when a flaky, dandruff-like material peels off the outer layer of the lens.
– Subluxated or dislocated cataracts, when the lens has moved from its normal position.
– Cases involving small pupils, or various types of glaucoma, an eye condition that damages the optic nerve.
– High myopia (near-sightedness) or high axial length, when the eyeball is unusually long.
– Deep socket or nanophthalmos, conditions related to the size and position of the eye in the skull.
– Pediatric cataracts, which occur in children.
– IOL (intraocular lens) exchange or secondary IOL cases, where an artificial lens placed inside the eye to replace the natural lens needs to be changed or added.
– Post vitrectomy, a surgery to remove some or all of the vitreous humor from the eye.
When a Person Should Avoid Manual Small Incision Cataract Surgery
In some cases, surgery might not be a good option, mostly because it depends on the surgeon’s skills and experience. So, there are also a few specific reasons why someone cannot proceed with surgery, including:
If a person’s cataract is very loose or out of place and the surrounding tissue (the capsule) is weak, surgery might not be recommended. This condition is known as subluxated or dislocated cataract with weak capsular support.
People with a very small cornea, the front, clear part of the eye, might not be eligible for surgery. This condition is called microcornea.
If the white outer layer of the eye, known as the sclera, is too thin, or if the clear front part of the eye (cornea) is thinning on the edges, surgery might be too risky.
Low endothelial cell count cases, when the inner layer cell count of the cornea is much reduced, might not be suitable for surgery.
Ciliary staphyloma is a condition in which the back part of the eye bulges out. This might make surgery too risky.
Patients with scleral ectasia, where the eye’s white outer layer is stretched or thin, might not be suitable for surgery.
If a person has scarring on the conjunctiva, the clear tissue covering the white part of the eye and the inside of the eyelids, surgery might not be advisable.
If a person has a condition called bleeding diathesis, which makes it hard for their blood to clot and stop bleeding, surgery can be too risky.
Equipment used for Manual Small Incision Cataract Surgery
Creating the Tunnel for Surgery
A bridle suture is used to secure the eye during surgery. McPherson-Westcott scissors and Bonaccolto forceps, which are special tools used in eye surgery, help to cut and hold the conjunctiva, the clear skin covering the eye. A calliper is used to make precise measurements. The surgeon applies heat using a conjunctival bipolar or unipolar cautery to prevent bleeding. A razorblade or 15-degree blade, crescent knife, and 3.2 mm keratome are used for precise cutting.
Making Side Port
A small hole, called a paracentesis, is created for surgical maneuvers using a 15 degrees side port blade.
Opening Lens Capsule
A capsulotomy is a process that opens up the capsule that holds the lens. Special tools such as a 26-30 G disposable needle or cystitome, and capsulorhexis forceps are used for this.
Separating the Nucleus
Water is used to separate the lens nucleus from its capsule by using a 25 G hydro dissection cannula.
Moving the Nucleus
The lens nucleus is moved into a position where it can be removed. Tools used for this are the hydrodissection cannula, a Sinskey hook, and a special tool called a Cyclodialysis spatula or Kuglen’s hook.
Breaking down the Nucleus
The lens nucleus is then broken into smaller pieces using special tools called nucleus dissection, nucleus bi-sector, nucleus tri-sector, and Miloop.
Extracting the Nucleus
A tool known as Sinskey hook and the irrigating wire vectis are used to remove these pieces of the nuclear lens.
Removing Leftover Material
Any remaining material of the cataract lens is removed by methods including the usage of Simcoe cannula, J-shaped and hydrodissection cannula.
Inserting the New Lens
An artificial lens, or Intraocular Lens (IOL), is placed into the capsule using a Sinskey hook and lens holding forceps.
Closing up
The surgeon holds the eye tissue with Bonaccolto conjunctival forceps and applies heat using a unipolar or bipolar cautery to prevent bleeding for closing the surgery.
Who is needed to perform Manual Small Incision Cataract Surgery?
Having a successful small incision cataract operation is a team effort. This team includes several skilled healthcare professionals. The eye specialist, called an Ophthalmologist, leads the way. There are also mid-level eye care staff in the outpatient department who assist with measuring the pressure in your eye (IOP). In addition, you’ll find nursing staff in the eye operation room, as well as other nursing staff who perform a test called the A-scan. This test helps to measure the length of your eye so the correct artificial lens (IOL) can be chosen. Lastly, there are counseling staff who help you make the best choice about your new lens (IOL). Everyone works together to make sure your cataract operation goes as smoothly as possible.
Preparing for Manual Small Incision Cataract Surgery
Before eye surgery, patients are usually prepared by using a type of medicine called NSAIDS and antibiotic eye drops for 3-7 days. This process helps reduce swelling, discomfort, and possible infection. To ensure a smooth and safe surgery, the eye needs to be numbed, which is referred to as blocking. This numbing can be accomplished through different methods, including peribulbar, retrobulbar, and sub tenons anesthesia. Using a local anesthetic to numb the eye area, referred to as topical anesthesia, has also been tried but has had limited success.
After the anesthesia is given, the patient is then taken to the operating room. Once the patient is lying flat on their back on the surgical table, the surgeon will make sure they have identified the correct eye for surgery. The eye is then cleaned using a solution containing 10% povidone-iodine, a type of antiseptic used to kill bacteria and other microorganisms. This same solution is then applied directly into the eye. To prepare for the surgery, a special device called a speculum is used to keep the eye open. This allows the surgeon to perform the surgery more safely and effectively.
How is Manual Small Incision Cataract Surgery performed
A “Bridle Suture” is a technique used in a specific kind of eye surgery called superior tunnel MSICS. In this procedure, special medical thread, known as 4-0 prolene suture, is passed through two muscles in the eye: the superior rectus and the lateral rectus. The purpose of this is to keep the eye steady during the procedure. The “bridle suture” is placed by holding the muscle and tilting the eye downward to expose it. The doctors need to be careful throughout this process to avoid damaging the eye.
“Conjunctival Peritomy” is the next step in the surgery where the eye tissue, called conjunctiva, is opened by using a pair of forceps to hold it and making a small cut (incision) with a sharp scissor. This is done around the outer edge of the eye. Then, the blood vessels in the area are cauterized (which means they use heat to stop any bleeding).
Next is the construction of the “Sclerocorneal Tunnel”. This involves making three separate cuts in the eye. Firstly, a cut is made in the white part of the eye (the sclera), then a cut is made through both the sclera and the transparent part of the eye (the cornea), followed by a final cut inside the eye in the anterior chamber. This technique is beneficial as it has a low risk of potential complications, it allows patients to quickly resume their daily activities and it doesn’t require stitches.
If needed, an incision can also be made on either the right or left side of the cornea (paracentesis). This step is useful for different purposes such as widening the pupil, staining the capsule that holds the lens, preparing the anterior eye chamber, and assisting in the procedure of delivering the new lens.
The entry into the anterior chamber, or the front part of the eye, is done with a special instrument. This is done carefully by making sure the instrument is aligned correctly with the incision, then turned 90 degrees, and pushed gently into the anterior chamber of the eye.
Once inside the eye, the clouded lens (cataract) is removed using a method called Capsulotomy. Here, the doctor makes an opening in the lens capsule which is the part of your eye that holds your lens in place. The size of the opening depends on the technique used.
A specific kind of Capsulotomy known as “Can Opener Capsulotomy” can be used in certain challenging cases such as a mature cataract, a small pupil, or a fibrosed and calcified lens. This technique involves making multiple small incisions in the lens capsule to take out the cataract.
In some other cases, a technique known as Continuous Curvilinear Capsulorhexis (CCC) is used. This approach offers many benefits, such as making the cataract removal easier and safer, allowing the artificial lens to be placed correctly, and making the removal of the remaining lens cortex easier with minimal risks.
Before performing a Capsulorhexis, there are several things that need to be taken into account like having a clear cornea, well-dilated pupil, and a good depth in the front part of the eye.
Lastly, the doctors might use a special dye to stain the lens capsule to make it easier to see. The dye is injected after an air bubble is introduced inside the eye, which acts as a barrier preventing the dye from diluting and staining other parts of the eye. The most commonly used dye is 0.1% trypan blue.
Possible Complications of Manual Small Incision Cataract Surgery
During eye surgery, different types of problems can occur related to the positioning, length, and depth of the incision. If the cut is placed at the front of the eye, it can result in a weak seal and potential leakage. This is treated by placing small, thin stitches (nylon tunnel sutures). If the cut is placed at the back of the eye, it leads to wider tunneling and may cause complications like bleeding, difficulty in removing the eye’s lens through the tunnel, and premature entry into the eye, which are also managed by placing stitches.
The length of the incision also matters. Smaller incisions less than 6mm can cause issues like difficulties in lens delivery, while larger incisions can lead to potential leakage and vision changes (astigmatism), both of which can be managed with stitches. An ideal incision depth should be about one-third of the sclera’s (the white part of the eye) depth, although achieving this can be difficult in certain situations.
Other complications include unwanted separation of the upper sclera from the lower sclera, superficial dissection of the sclera flap, premature entry into the eye, detachment of the Descemet membrane (the thin layer that forms the inner part of the cornea), and conjunctival ballooning where fluid may accumulate under the thin skin covering the front of the eye leading to vision problems.
The surgery also includes delicate procedures like creating a hole in the capsule that contains the lens (capsulorhexis), which can involve complications like unintended extension of the tear and challenges in removing the lens. Other problems that can arise include fluid misdirection syndrome, nucleus drop, difficulty in delivering the nucleus, and hyphema (blood in the front part of the eye).
Post-surgery, issues can include wound leakage, swelling or clouding of the cornea, inflammation inside the eye, increase in eye pressure (glaucoma), and complications related to the intraocular lens (IOL). Unique complications to a particular eye surgery known as manual small incision cataract surgery (MSICS) can include issues related to tunneling and the cornea, as well as incorrectly placed stitches.
What Else Should I Know About Manual Small Incision Cataract Surgery?
Manual Small Incision Cataract Surgery (MSICS) has drastically changed how we approach cataract surgery in the modern world, particularly in low-income and developing countries. Large studies have found that the long-term outcomes of MSICS, like vision clarity and distortion (called astigmatism), are similar to another common type of cataract surgery called phacoemulsification.
MSICS can be particularly beneficial for challenging cases as it can produce excellent results with few complications. The process of MSICS has also acted as a learning tool for surgeons performing phacoemulsification, as most steps in the two procedures are very similar. The primary difference lies in the phacoemulsification method which includes two additional steps: trenching and emulsification. MSICS is particularly valuable because it hones a surgeon’s skill in handling delicate body tissues.