Manual Small-incision Cataract Surgery

Cataract surgeries performed at the Gambella eye camp:  276
Highest number of surgeries performed in one day of the camp:  49
Cost of each cataract surgery:  $50 US dollars (cost to patient is free)
Average duration of a single cataract surgery at the eye camp:  < 15 minutes

 Dr. Samuel's notes explaining manual small-incision cataract surgery

The manual small incision cataract surgery (MSICS) procedure which Dr. Samuel regularly uses reflects the incredible resilience of the human body.  To perform the operation, the surgeon essentially cuts open the eyeball, replaces the lens, and patches the eye- without sewing or suturing the cut in the eyeball!  After one day, the eye actually heals itself and the patient has his or her vision restored.

Of course, the details of the procedure add additional layers of complexity.  A step-by-step guide to MSICS-

Prep- Dilation, Sterilization, and Anesthesia

Before the operation can begin, the patient's pupil must be dilated in order to give the eye surgeon the largest possible area in which to work.  Because the lens lies behind the iris, the further the pupil is dilated, the less the iris will obstruct the exit of the lens.  We used a mixture of tropicamide, cyclopentolate, and phenylephrine to achieve dilation.

As with any other surgery, the surgical field must be sterilized prior to operation- at the eye camps, Dr. Samuel uses a povidone-iodine mixture.

Finally, the eye must be numbed and rendered immobile.  This was accomplished with a lidocaine-adrenaline injection.  The adrenaline works by delaying the absorption of lidocaine, the anesthetic, into the body so that the numbing effect can continue throughout the duration of the surgery.

Step 1- Conjunctival Dissection

eye as seen from the side

Once the patient is lying on the operating table, under the eye of the ophthalmologist's microscope, the real fun begins.  The ophthalmologist grabs hold of the outer layer of the white of the eye (the conjunctiva) and makes a careful horizontal cut a few millimeters above the iris.  Though this step is referred to as the conjunctival dissection, it is technically a dissection of two layers- the conjunctiva and the layer of the eye below it, called Tenon's capsule.  In dark-skinned people, such as those in Gambella, Tenon's capsule is much thicker, and sometimes the ophthalmologist must make a second cut to dissect Tenon's capsule instead of taking the two layers out with one blow.

After pulling away an area of the conjunctiva and Tenon's capsule, the surgeon then seals (or "cauterizes") the blood vessels he or she has exposed.

Step 2- Linear Incision

eye seen face on

Next, the ophthalmologist makes a careful horizontal cut in the sclera, the layer underneath the conjunctiva and Tenon's capsule.  Some surgeons prefer the "smiley face" cut or the "frowning face" cut, but Dr. Samuel's incision of choice was linear.

Step 3- Scleral Tunnel

eye facing up as seen from the side

Thirdly, the eye surgeon creates an upward sloping tunnel from the incision he has just created all the way to the area in front of the iris (the anterior chamber).

Step 4- Capsulorrhexis

Now that the ophthalmologist can reach the lens, he can peel off a circular area of the front part of the "bag" (or capsule) holding the lens.  In other methods of MSICS, doctors peel off the front of the bag in other ways, such as in a "V" shape.

Step 5- Hydrodissection

 eye as seen from above

Once the front of the capsule is removed and the nucleus (or center) of the lens is exposed, the ophthalmologist shoots a stream of water at the nucleus, rotating it about 180 degrees to completely detach it from the rest of the lens.  


Step 6- Nuclear Extraction

 eye as seen from above- pulling the nucleus through the scleral tunnel

Next, the surgeon can reach into the capsule and pull out the nucleus of the lens.  Dr. Samuel's preferred technique was to use a fishhook, which he created by reforming the needle of a syringe into a hook shape.  Not all nuclei are created equal, and there was a huge amount of variability in the consistency of lens nuclei at the eye camp.  Dr. Samuel deemed the fairly mature cataracts "delicious," as they were solid, hard, and dense, and relatively easy to extract.  Hypermature cataracts, on the other hand, have progressed further than mature cataracts and are also known as Morgagnian.  In Morgagnian cataracts, the outer part of the lens (the cortex) actually turns from solid to liquid though the inner part of the lens (the nucleus) remains solid.

According to Dr. Samuel, the nuclear extraction step is the hardest part of the operation, as the lens is in danger of falling further back into the eye.  To me, this seemed like the most exciting part of the surgery, as the removal of the lens from the eyeball was almost like the delivery of a baby (albeit a tiny baby that you throw away immediately after the surgery).


Step 7- Aspiration

Since the lens is composed of both the center portion (nucleus) and the outer portion (cortex), even after the nucleus has been extracted, the less rigid peripheral portion of the lens remains.  Typically, the surgeon aspirates or suctions out the cortex using a device called a Simcoe cannula, essentially vacuuming behind the iris to pull out the strands of lens remaining.  Sometimes, fragments of cortex remain behind the iris on the same side of the eye that the incision was made.  In this case, it is impossible to reach the last pieces of cortex, so an additional incision must be made about 120 degrees counter-clockwise from the initial incision.  From there, the ophthalmologist has the perfect angle from which to suction out the last of the lens.


Step 8- Inject Viscoelastic

Normally, the space behind the cornea (the anterior chamber) contains a water-like liquid called aqueous humor which, among other things, helps to maintain a sort of pressure equilibrium in the eye.  During MSICS, this equilibrium is disrupted and thus the ophthalmologist injects a similar (but synthetic) material called viscoelastic to help restore the appropriate pressures.  The surgeon can choose between dispersive and cohesive viscoelastic.

Cohesive viscoelastic, as its name suggests, tends to clump together, making it easier to remove.

Molecules of dispersive viscoelastic, on the other hand, separate from each other making removal more difficult.  The benefit of dispersive viscoelastic is that it coats the inside of the cornea (endothelium), providing a nice protective coat.


Step 9- Lens Implantation

 inserting the new lens through the tunnel and under the iris

Finally, the ophthalmologist inserts the new lens into the spot where the old lens used to sit- behind the iris and within the "bag" (capsule).  Two curved prongs on either side of the new lens called haptics ensure that the lens hooks snugly into the capsule.  To my understanding, the viscoelastic helps create the right pressure in the front of the eye so that the surgeon has an easier time placing the new lens.

artifical lens with hooks (or "haptics") on either side

Step 10- Removal of Viscoelastic


When the surgeon removes the viscoelastic using the vacuum-like tool called a Simcoe cannula, he can also use the opportunity to "polish" the newly inserted lens along the patient's visual axis.  This helps to lessen any blurriness the patient might otherwise experience.


Step 11- Closing the Wound

applying water pressure to the incision to seal it

Finally, the ophthalmologist fills the space behind the cornea with water to restore the pressure lost after the removal of viscoelastic, then shoots water along the linear incision he made in Step 2.  If all has gone according to plan, when the surgeon lightly taps the patient's cornea, no water leaks out of the incision because a flap of eye is holding it shut.

Throughout the surgery, the ophthalmologist must make numerous decisions as he goes.  If the surgeon senses the patient is tense, he will typically make his initial dissections further from the intersection of the white of the eye and the cornea (the limbus), thereby creating a longer scleral tunnel.  Tense patients are at greater risk of their irises leaking out through the incision, so creating a longer tunnel helps prevent this.  Patients who have a condition called pseudoexfoliation, in which protein deposits appear in the iris and/or lens present as riskier surgical cases because the strands encircling the lens and holding it in place (zonule fibers) are more fragile.  Thus, the ophthalmologist must be especially delicate in his surgical actions.


After drying the eye and injecting an antibiotic mixed with a medication to reduce inflammation, the patient's eye is patched up and he or she is sent home to rest until the next morning, when- if all has gone well- the patient will regain sight.