Manual small incision cataract surgery (MSICS) is an evolution of extracapsular cataract extraction (ECCE); the lens is removed from the eye through a self-sealing scleral tunnel wound. A well-constructed scleral tunnel is held closed by internal pressure, is watertight, and does not require suturing. The wound is relatively smaller than that in ECCE but is still markedly larger than a phacoemulsification wound. Comparative trials of MSICS against phaco in dense cataracts have found no statistically significant difference in outcomes but MSICS had shorter operating times and significantly lower costs. MSICS has become the method of choice in the developing world because it provides high-quality outcomes with less surgically induced astigmatism than ECCE, no suture-related problems, quick rehabilitation, and fewer post-operative visits. MSICS is easy and fast to learn for the surgeon, cost effective, simple, and applicable to almost all types of cataract.

MSICS is a procedure that was developed to reduce costs in comparison with phacoemulsification, which requires expensive high-tech equipment that needs skilled maintenance, and is relatively unsuited to less developed regions, and to eliminate the need for suturing the incision, by using a self-sealing incision. This reduces operating time, and for some geometries of incision, considerably reduces surgery induced astigmatism, or induces a reduction in pre-surgery astigmatism. The procedure is fast, economical, effective, and produces results statistically similar to phaco surgery. It is extensively used in less developed countries and regions, with good outcomes.

The same general contraindications for cataract surgery apply. Specific contraindications for MSICS include hard or dense cataracts where the nucleus is too large for the MSICS incision; and in cases where the nucleus is found to be deformed on a nanophthalmic (very small) eye.

Preparation may begin three-to-seven days before surgery with the preoperative application of NSAIDs and antibiotic eye drops. The pupil is dilated using drops if the IOL is to be placed behind the iris to help better visualise the cataract and for easier access.

Anaesthesia may be placed topically as eyedrops or injected next to (peribulbar) or behind (retrobulbar) the eye or sub-tenons. Local anaesthetic nerve blocking has been recommended to facilitate surgery. Topical anaesthetics may be used at the same time as an intracameral lidocaine injection to reduce pain during the operation. Oral or intravenous sedation may also be used to reduce anxiety. General anaesthesia is rarely necessary but may be used for children and adults with medical or psychiatric issues affecting their ability to remain still during the procedure.

The operation may occur on a stretcher or a reclining examination chair. The eyelids and surrounding skin are swabbed with a disinfectant, such as 10% povidone-iodine, and topical povidone-iodine is put in the eye. The face is covered with a cloth or sheet with an opening for the operative eye. The eyelid is held open with a speculum to minimize blinking during surgery. Pain is usually minimal in properly anaesthetised eyes, though a pressure sensation and discomfort from the bright operating microscope light is common. Bridle sutures may be used to help to stabilize the eyeball during sclerocorneal tunnel incision, and during extraction of the nucleus and epinucleus through the tunnel.

A defining characteristic of this technique is in the incision made for access to the cataract, which is smaller than for ECCE, and larger than for phacoemulsification, but like phaco, the wound is self sealing due to its geometry.

The small incision into the anterior chamber of the eye is made at or near the corneal limbus, where the cornea and sclera meet, either superior or temporal. Advantages of the smaller incision include use of few-or-no stitches and shortened recovery time. The "small" incision is small in comparison with the earlier ECCE incision but considerably larger than the phaco incision. The precise geometry of the incision is important as it affects the self-sealing of the wound and the amount of astigmatism caused by distortion of the cornea during healing. A sclerocorneal or scleral tunnel incision is commonly used, which reduces induced astigmatism if suitably formed. A sclerocorneal tunnel, a three-phase incision, starts with a shallow incision perpendicular to the sclera, followed by an incision through the sclera and cornea approximately parallel to the outer surface, and then a beveled incision into the anterior chamber. This structure provides the self-sealing characteristic because internal pressure presses together the faces of the incision.