Manual small-incision cataract surgery (MSICS), also called small-incision cataract surgery or sutureless extracapsular cataract extraction (SECCE), is a type of cataract surgery. It is a form of extracapsular cataract extraction (ECCE), and its most distinctive feature is a self-sealing, sutureless corneoscleral tunnel incision.
According to a 2004 WHO report, cataracts account for 47.8% of blindness worldwide, and over 90% of disability-adjusted life years (DALYs) are concentrated in developing countries. Against this background, MSICS has been adopted mainly in developing countries as a means to achieve high-volume, low-cost cataract surgery.
The modern MSICS technique is based on a method reported in 1999, which itself is founded on a manual extracapsular cataract extraction technique reported in 1992.
QWhy is MSICS the mainstream in developing countries?
A
Phacoemulsification requires expensive equipment, consumables, and maintenance costs, and the training period for surgeons is long. MSICS costs about $15 per case in surgical materials (compared to about $70 for phacoemulsification), the surgery time is about 9 minutes (compared to about 15.5 minutes for phacoemulsification), and it is less dependent on expensive equipment. It has become widespread as a surgical method that can treat large numbers of cataracts even in resource-limited settings.
The first reported manual extracapsular cataract extraction described a method of nucleus removal through a 5–7 mm scleral or limbal incision. After anterior chamber puncture and capsulotomy, the cortex and epinucleus are aspirated, and the nucleus is freed by hydrodissection. With an anterior chamber maintainer in place, the nucleus is delivered by hydroexpression (hydraulic nucleus expulsion) using a glide.
Reported based on the experience of the Tilganga Eye Center in Nepal, this has become the standard technique for modern manual small-incision cataract surgery. The main steps are as follows.
Anesthesia, disinfection, and eye opening: Peribulbar anesthesia, iodine-based disinfection, insertion of a lid speculum
Conjunctival flap creation: Create a fornix-based conjunctival flap from the 10 to 2 o’clock position to expose the sclera
Diathermy hemostasis: Hemostasis at the planned scleral incision site
Sclerocorneal tunnel creation: Create a tunnel from the sclera through the limbus to 1–1.5 mm into clear cornea. The inner opening of the tunnel is widened on the corneal side (flaring) to facilitate nucleus capture.
Capsulotomy: Triangular capsulotomy using a 26G needle
Hydrodissection: Performed to free the nucleus in immature cataracts. Not necessary in mature cataracts.
Nucleus prolapse into the anterior chamber: Rotate and tilt the nucleus using a Simcoe irrigation/aspiration cannula to prolapse it into the anterior chamber.
Nucleus removal: Performed by one of the following two methods:
Method 1 (Hydrostatic method): Pass a Simcoe cannula under the nucleus and use hydrostatic pressure and gentle lifting to push it into the tunnel.
Method 2 (Vectis method): Pass an irrigating vectis under the nucleus, lift it, and withdraw it through the tunnel.
Cortex removal: Remove residual cortex and epinucleus with a Simcoe cannula
Intraocular lens insertion: Insert a polymethyl methacrylate (PMMA) intraocular lens
Wound closure check: Press the eyeball to confirm no leakage from the wound (self-sealing confirmation)
Subconjunctival injection and eye patch: After subconjunctival injection of antibiotics and steroids, apply an eye patch
In a modified technique reported by Dr. Sudhir Singh in 2012, the lens nucleus is divided and removed within a sclerocorneal tunnel incision less than 6 mm. While other nucleofracture techniques manipulate within the anterior chamber, this technique completes nucleus removal within the tunnel, reducing incision size and induced astigmatism.
Combined glaucoma surgery: Can be combined with trabeculectomy using a superior conjunctival flap
QWhere is the sclerocorneal tunnel created?
A
Typically, a tunnel is created in the superior (12 o’clock) sclera. A conjunctival flap is created at the fornix base to expose the sclera. The tunnel extends from the sclera across the limbus into the clear cornea for 1-1.5 mm, and is widened (flared) on the inner (corneal) side. This shape provides self-sealing.
3. Indications and Selection of Surgical Technique
When Manual Small-Incision Cataract Surgery is Advantageous
Mature or very hard nucleus: The nucleus can be removed using hydraulic and mechanical manipulation alone, without the need for ultrasound energy.
Weak zonules (zonular weakness): Nuclear manipulation is gentle, placing less stress on the zonules.
Corneal endothelial risk: Mechanical damage to the corneal endothelium is avoided because there is no ultrasound vibration.
Resource-limited settings: Expensive ultrasound equipment is not required. Training time is shorter, and it can accommodate high-volume surgery.
When Phacoemulsification is Advantageous
Early postoperative uncorrected visual acuity: The incision is small, inducing less astigmatism, resulting in better early postoperative uncorrected visual acuity.
Astigmatism management: Fine adjustment of incision location and size is possible, and it can also be used to correct pre-existing astigmatism.
Special intraocular lenses: Small incisions are essential for inserting foldable intraocular lenses, making phacoemulsification suitable.
Complex cases: It offers greater flexibility in complex cases such as uveitic eyes, high myopia, and small pupils.
Randomized clinical trials have shown that phacoemulsification provides better postoperative uncorrected distance visual acuity and lower rates of surgical complications such as iris prolapse and posterior capsule rupture compared to manual extracapsular cataract extraction and manual small-incision cataract surgery1). On the other hand, in resource-poor settings, some randomized clinical trials have shown that sutureless extracapsular cataract extraction yields good results comparable to phacoemulsification1).
The decision to perform cataract surgery is made by comprehensively considering the degree of visual impairment, impact on daily life, general health, surgeon’s experience, equipment, and cost.
Corneal endothelial cell density: When endothelial cell count is low, manual small-incision cataract surgery is considered to avoid ultrasonic vibration.
Orbital anatomy and eye depth: A temporal approach may be necessary.
Glaucoma comorbidity: Whether to preserve the superior sclera or perform simultaneous surgery.
207 cases, 50% with preoperative index finger or worse
Tilganga 2007
98% (best corrected visual acuity)
85% with uncorrected visual acuity 20/60 or better
Aravind Hospital
Complication rate 1.11%
Manual small incision cataract surgery among 127,644 cases
A Cochrane review pooled data from a total of 1,708 participants (8 trials) and confirmed that best corrected visual acuity was equivalent between manual small incision cataract surgery and phacoemulsification. However, uncorrected visual acuity in the short term after surgery was better after phacoemulsification. Additionally, the surgical cost of phacoemulsification was approximately four times that of manual small incision cataract surgery.
In a prospective randomized trial (Tilganga, 2007), no significant differences were found between the two techniques in uncorrected visual acuity, best corrected visual acuity, or corneal astigmatism. Operative time was significantly shorter for manual small incision cataract surgery (9.0 min vs. 15.5 min, p < 0.001). Surgical material costs were $15 for manual small incision cataract surgery vs. $70 for phacoemulsification.
Chang reported that in a prospective comparison by two experienced surgeons, there was no significant difference in outcomes between phacoemulsification and manual small incision cataract surgery1).
In a large study from Aravind Hospital (127,644 cases), complication rates were 1.01% for phacoemulsification, 1.11% for manual small incision cataract surgery, and 2.6% for extracapsular cataract extraction. In a subgroup analysis of resident surgeons, the complication rate was higher in the phacoemulsification group compared to the manual small incision cataract surgery group. The incidence of endophthalmitis did not differ by surgical technique.
The reason the sclerocorneal tunnel is self-sealing lies in its biomechanical properties based on its shape and location.
The external incision (scleral side) is narrower than the internal incision (corneal side): When intraocular pressure rises, a valve mechanism closes the outer part of the tunnel.
Wide flaring on the corneal side: The inner widening guides the nucleus and allows intraocular pressure to act toward closing the wound.
Ensuring tunnel length: A 1–1.5 mm intracorneal extension reinforces wound closure.
Due to these structural characteristics, manual small-incision cataract surgery achieves watertightness without sutures. Small-incision surgery is generally easier to construct with self-sealing, offers greater safety in case of sudden patient movement or intraoperative suprachoroidal hemorrhage, imposes fewer postoperative activity restrictions, and results in less initial inflammatory response and induced astigmatism change 1).
Mechanism of Advantage Compared to Phacoemulsification
In cases with mature nuclei, weak zonules, or fragile corneal endothelium, manual small-incision cataract surgery or manual extracapsular cataract extraction may be preferred 1). The reasons are as follows.
Mature nucleus: A very hard nucleus increases ultrasonic energy during phacoemulsification, raising the risk of thermal burn and corneal endothelial damage. Manual small-incision cataract surgery avoids this risk.
Weak zonules: Ultrasonic vibration causes lens movement that increases stress on the zonules. The mechanical manipulation in manual small-incision cataract surgery is gentler.
Corneal endothelial risk: The ultrasonic energy and irrigation fluid during phacoemulsification cause endothelial cell loss, which can be avoided.
7. Latest Research and Future Prospects (Research Stage Reports)
Surgical methods using femtosecond lasers for corneal incision, capsulotomy, and nuclear fragmentation and softening are being studied. Nuclear fragmentation and softening may facilitate nucleus delivery in manual small-incision cataract surgery, and the application of femtosecond laser-assisted cataract surgery techniques to manual small-incision cataract surgery is being explored. However, the cost of femtosecond laser equipment remains a major barrier to adoption in developing countries.
Development of Ultra-Small Incision Manual Small-Incision Cataract Surgery
As an evolution of the tunnel nuclear fragmentation technique (Singh method) using incisions smaller than 6 mm, attempts are being made to further reduce incision size while using foldable intraocular lenses other than polymethyl methacrylate. The goals are to reduce induced astigmatism and improve postoperative uncorrected visual acuity.
Quality Improvement Programs in Developing Countries
In the high-volume cataract surgery models of the Aravind Eye System and international non-governmental organizations, research is progressing on quality management and training programs to further reduce complication rates of manual small-incision cataract surgery.
