Cataract Surgery, 3rd Edition

PART III – Extracapsular Cataract Extraction

Chapter 11 – Small Incision Cataract Surgery in Underdeveloped Countries

Geoffrey Tabin, MA, MD

Contents

Evolution of the optimal surgical approach to cataracts in the developing world

Cataracts are currently the leading cause of blindness worldwide with the majority of cases in developing nations. Of the 38 million cases of blindness (visual acuity less than 20/400), an estimated 16 million are caused by age-related cataracts. In Nepal alone the percentage of curable blindness resulting from cataracts is more than 80%, and in India 3.8 million people develop cataract blindness yearly. As the world's population ages the incidence of cataract in developing nations will continue to rise and with no improvement in current practices, the World Health Organization estimates a doubling of blindness rates by 2020. Projections show that to eliminate the rapidly growing backlog within the next 25 years, the global number of cataracts operated on annually would have to increase from 7 to 32 million by the year 2020. There is clearly a pressing need for faster, less-expensive, and more effective delivery of high-quality cataract surgery.

New surgical techniques have minimized the use of expensive consumables and optimized efficiency, while preserving the highest level of quality in visual outcomes and minimizing complications.^[1] Three steps have dramatically improved the speed and efficiency with which we are able to deliver high-quality sutureless, small-incision, cataract surgery (SICS). The first is a well-constructed scleral tunnel with a larger internal opening than the external scleral incision, which relies upon intraocular pressure to close the internal lip of the wound, thereby creating a self-sealing wound and eliminating postoperative suture-induced astigmatism. The second is a triangular capsulotomy technique, which eliminates the need for capsular staining with even the most mature cataracts. Finally, our lens-delivery technique relies on use of fluidics and eye positioning to irrigate the nucleus through our funnel-shaped wound and out of the eye. Finally, the once cost-prohibitive intraocular lenses (IOLs) and other consumables such as viscoelastic, have become affordable due to high-quality production in developing countries including Nepal and India. It has become increasingly clear that the modified version of extracapsular cataract extraction (ECCE) with posterior chamber (PC) IOL placement described in this chapter is the preferred approach to cataract surgery in the developing world.

Preoperative management

Preoperative management begins with the surgeon examining patients who have been pre-screened for vision and relative afferent pupillary defects by ophthalmic assistants. As the majority of our patients have mature cataracts with no view to the posterior segment, the patients undergo B-scan ultrasound, when available, at the time of their biometry measurements.

The evening before surgery the patients' faces are vigorously washed and antibiotic drops and ointment are instilled at this time. Prior to surgery the eyelashes are closely cropped and fluoroquinolone eye drops are instilled at the time of dilation. The eye is then prepped with Betadine and a retrobulbar anesthetic is administered by an anesthetic technician, after which a Betadine soaked gauze is held over the eye. At the start of the case the surgeon performs a final Betadine prep with instillation of a small amount of 5% Betadine into the fornix of the eye. This preoperative cleaning and sterilization regimen leads to a low infection rate. The efficiency of patient turnover is maximized: as the surgeon is prepping and draping the eye, the scrub nurse is arranging a new instrument set, and surgery proceeds with a typical delay of less than 3 min between cases.

Surgical technique

Surgeon Positioning and Maximizing Surgical Field Exposure

We generally advocate that in the beginning surgeons learn SICS from a superior approach; however, many SICS surgeons operate from a temporal approach.

Temporal vs. Superior Surgical Approach

While a superior approach has long been the standard of care when performing ECCE, we routinely perform (98% of cases) ECCE using a temporal surgical approach as there is a significant difference between the amount of postoperative astigmatism induced by the two techniques. The mean induced astigmatic change is 1.75 diopters (D) following a superior surgical approach due to the effects of gravity and motion of the eyelids on the wound, while 0.75 D of astigmatism is induced following a temporal surgical approach.

A superior approach has remained the mainstream technique of choice given the following advantages: first, the upper eyelid covers the external wound following the operation when a superior approach is used, providing good wound protection. Second, surgeon positioning at the head of the operating table provides for a more streamlined flow of patients through the operating suite. Microscope heads, chair positions, and instrument tables need not be repositioned between cases.

Fortunately, most of these limitations have been overcome. The rate of postoperative infection is equivalent when using either a superior or a temporal approach; however, it is critical to close the conjunctiva over the external scleral wound with cauterization at the completion of the temporal approach surgery. We have also developed an operating table which facilitates patient flow when operating temporally. It allows the surgeon to be seated at one side; patients are then positioned with their feet perpendicular to the surgeon's line of sight, facing in either direction depending on the eye to be operated upon (Figure 11-1).

Access the Anterior Chamber by Creating a Sclerocorneal Tunnel

A superior rectus traction suture may be used if operating superiorly to enhance exposure. A fornix-based conjunctival peritomy to sclera is performed superiorly from 10 to 2 o'clock to bare sclera. Light cauterization is used to control bleeding and blanch episcleral vessels over the incision site. A straight to slightly frown-shaped incision centered at 12 o'clock is carried to 30–50% scleral depth tangential to the limbus for 6–7 mm and approximately 1.5–2 mm from the limbus. This incision can be made with a razor blade fragment or crescent blade, the former helping with cost containment. The crescent blade is then used to create a lamellar scleral corneal tunnel from the initial incision in a single plane approximately 1–1.5 mm into the clear cornea and parallel to the ocular surface. The dissected pocket should extend nasally and temporally to the limbus so that the transverse extent is much greater in the cornea than in the sclera (Figure 11-2).

Triangular Capsulotomy vs. Continuous Curvilinear Capsulorrhexis

Triangular Capsulotomy

In the developing world mature, hypermature and Morgagnian cataracts are common; the anterior capsules associated with such dense cataracts are often tough and leathery, and there are frequently adhesions between the anterior capsule and the lens nucleus. Furthermore, poor surgical visibility is common due to corneal scars, pterygium, climatic keratopathy, and sub-optimal surgical microscopes. Under these circumstances, capsulorrhexis types of capsulotomies are difficult to complete and can lead to incomplete or inadequate capsular openings or tears in unexpected directions, increasing the risk of posterior capsular rupture.

Triangular capsulotomy has many advantages that make it a superb option in such sub-optimal surgical settings. First, it utilizes a straight needle, which facilitates entry into the AC and allows easy control of AC depth because the sclerocorneal tunnel has not yet been completed. Second, visibility is optimized as opaque lens material can be readily removed from the AC by aspiration or irrigation. Third, the capsulotomy is cut, not torn, creating a reliably triangular shape, minimizing the number of capsular tags. Fourth, a triangular capsular flap provides clear visibility of the boundaries of the capsular bag, facilitating IOL placement.

Continuous Curvilinear Capsulorrhexis

We often employ a continuous curvilinear capsulorrhexis (CCC) for less advanced cataracts by using a 27-gauge needle introduced into the AC through a separate puncture site immediately adjacent to the external wound of the sclerocorneal tunnel. Viscoelastic is instilled prior to insertion of the needle into the anterior chamber. This capsular opening needs to be approximately 5–6 mm in diameter, substantially larger than that utilized during phacoemulsification, as the entire lens must be expressed through this capsular window.

Triangular Capsulotomy

The triangular capsulotomy is performed before the sclerocorneal tunnel is completed so that the depth of the AC is maintained. A straight 26-guage needle attached to a 1-mL syringe filled with balance saline solution is passed through the scleral tunnel with the entry point into the AC in sclera, not the more rigid corneal tissue. Using the beveled tip of the needle, the linear cut in the capsule is made from 4 o'clock to 12 o'clock and then from 8 o'clock to 12 o'clock so the two incisions meet at 12 o'clock. Thus, a triangular or V-shaped flap of anterior lens capsule still attached at its base is created (Figure 11-3). Each point of the triangular flap should be approximately 3 mm from the center of the pupil. The apex of the capsulotomy is then lifted with the needle tip and peeled towards 6 o'clock to ensure the capsular cuts are complete. If the chamber shallows, a small amount of fluid may be irrigated through the needle to re-deepen the chamber.

Following capsulotomy, the sclerocorneal tunnel is then completed using a keratome blade to enter the anterior chamber. The sides of the blade are used to open the cornea from the temporal to the nasal aspects of the wound. The wound should be internally flared to encourage the nucleus to engage the tunnel at the time of expression. Viscoelastic may be placed in the AC to facilitate wound creation.

Nucleus Delivery into the Anterior Chamber

The lens nucleus is displaced from the capsular bag into the AC using both hydrostatic and gentle mechanical pressure. Irrigating under the displaced triangular anterior capsule flap, as well as under the temporal and nasal edges of the flap, with a flowing Simcoe cannula, will mobilize the lens nucleus and delaminate the lens components by hydrodissection. The nucleus is then gently directed inferiorly within the capsular bag while intermittently directing irrigation posterior to the nucleus, until the superior nuclear pole emerges from the capsular bag into the AC, forming a new cleavage plane between the nucleus and the iris. This newly formed cleavage between the nucleus and the iris is then accentuated by directing flow between the iris and the nucleus with the Simcoe cannula until the lens is entirely delivered into the AC. It is important not to force the nucleus in any one direction too strongly as this will strain and possibly compromise the zonules.

Extraction of the Nucleus from the Anterior Chamber

The lens nucleus is now removed from the eye. While several potential protocols are available for nucleus removal we recommend avoiding procedures that require sectioning or fragmentation of the nucleus, as these may traumatize the corneal endothelium. We recommend the following technique:

The vigorously flowing Simcoe cannula is passed posterior to the nucleus until the tip is fully visible beyond the distal pole of the nucleus. The eye is then gently rotated downward with toothed forceps held in the other hand. The accumulating irrigation fluid from the cannula will engage the nucleus into the internal mouth of the sclerocorneal tunnel. Hydrostatic pressure plus gentle lifting and retraction with the tip of the Simcoe cannula will force the nucleus further into the tunnel. Open the external foramen of the tunnel with gentle downward pressure using the heel of the Simcoe cannula and deliver the entire nucleus (Figure 11-4).

Posterior Chamber Intraocular Lens Placement

The Simcoe canula is then used in the standard fashion to remove all nuclear and cortical debris from the AC and capsular bag. Next, air is injected into the anterior chamber using the Rycroft cannula and a PMMA (polymethylmethacrylate) PC IOL is inserted into the capsular bag. Alternatively, the IOL can be inserted after filling the AC and expanding the capsular bag with viscoelastic. The apex of the V-shaped capsulotomy tear should also be folded backwards during this maneuver so that the flap lies on top of the anterior capsule. During insertion of the leading haptic, the anterior lip of the cornea is folded inward which protects the corneal endothelium during lens implantation. The leading haptic is then passed into the capsular bag inferiorly, behind the base of the triangular capsulotomy (Figure 11-5). The folded anterior capsule flap at the base of the triangular capsulotomy serves as an easily identifiable landmark and facilitates correct PC IOL placement.

The trailing haptic is then passed into the capsular bag and correct placement of the PC IOL within the capsular bag is confirmed by observing the posterior capsule stretch lines that form perpendicular to the contacts between the IOL haptics and the capsule.

Capsulectomy

If a triangular capsulotomy was performed, the anterior capsular flap is removed to prevent any obscuring of the visual axis. A small incision is made in the anterior capsule at the edge of the base of the triangular flap with fine Vannas scissors while maintaining the AC depth with an irrigating Simcoe cannula. The capsular flap is engaged with aspiration using the Simcoe cannula (using low flow irrigation) and used to gently tear the flap entirely across its base which then should be removed from the AC (Figure 11-6).

Closure

The Simcoe cannula is used to irrigate and aspirate residual air or viscoelastic in the AC and intraocular pressure is restored. The 3-planed sclerocorneal tunnel will self-seal, which is confirmed by applying gentle pressure to the globe with an instrument and observing for wound leakage. Less than 1% of our wounds require suture placement for adequate closure. A subconjunctival injection of antibiotic and steroid is given just superior to the conjunctival wound, which balloons the conjunctiva and moves it over the limbus to cover the scleral wound. In the instance of a temporal surgical approach the conjunctiva is closed over the scleral wound with cauterization at the wound edges.

After removing the sterile drapes, antibiotic ointment is applied to the eye, which is then patched and shielded. Steroid and antibiotic drops are instilled every 2 h for the first postoperative day and then four times per day for 3 weeks.

Surgical outcomes

Utilizing intraocular lenses manufactured in India or Nepal and local pharmaceuticals the cost per surgery is less than $20 per case. Moreover, experienced surgeons routinely perform more than 50 cases per day with an average operating time of 5 min per surgery.^[2] The results of a prospective, randomized clinical trial in Nepal comparing our manual sutureless extracapsular surgical technique with phacoemulsification were published in the American Journal of Ophthalmology.^[3] It was an “Expert Trial” with Professor David Chang operating with a phaco-chop (phaco) technique and Dr. Sanduk Ruit carrying out the temporal approach small incision ECCE (SICS). Both techniques achieved excellent and equivalent results. At 6 months 89% of the SICS patients had an uncorrected visual acuity (UCVA) of 20/60 or better and 98% had a best-corrected acuity (BCVA) of 20/60 or better; this outcome was equivalent to the visual acuity outcomes of the phaco patients (Figure 11-7). Furthermore, SICS is significantly faster, less expensive and less technology dependent than phacoemulsification and may be the more appropriate surgical procedure for the treatment of advanced cataracts in the developing world.

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References

[1]. Ruit S., Paudyal G., Gurung R., Tabin G., Moran D., Brian G.: An innovation in developing world cataract surgery: sutureless extracapsular cataract extraction with intraocular lens implantation. Clin Exper Ophthalmol 2000; 28:274-279.

[2]. Ruit S., Tabin G.C., Nissman S.A., Paudyal G., Gurung R.: Low-cost high-volume extracapsular cataract extraction with posterior chamber intraocular lens implantation in Nepal. Ophthalmology 1999; 106:1887-1892.

[3]. Ruit S., Tabin G., Chang D.: A prospective randomized clinical trial of phacoemulsification vs. manual sutureless small-incision extracapsular cataract surgery in Nepal. Am J Ophthalmol 2007; 143(1):32-38.

Copyright © 2010 Elsevier Inc. All rights reserved. Read our Terms and Conditions of Use and our Privacy Policy.
For problems or suggestions concerning this service, please contact: online.help@elsevier.com

Bibliography

In: Brilliant G.E., ed. The epidemiology of blindness in Nepal: report of the 1981 Nepal Blindness Survey, Chelsea, Michegan: Seva Foundation; 1988:115-241.

Ruit S., Robin A.L., Pokhrel R.P., Sharma A., Defaller J., Maguire P.T.: Long-term results of extracapsular cataract extraction and posterior chamber intraocular lens insertion in Nepal. Tr Am Ophthalmol Soc 1991; LXXXIX:59-76.