Ординатура / Офтальмология / Английские материалы / Master's Guide to Manual Small Incision Cataract Surgery (MSICS)_Garg_2009

Advantages

i.Easy approach in all directions in AC and PC.

ii.Sub-incisional cortex removal becomes easy.

iii.Side port incision facilitates minimal use of tunnel.

Disadvantage

i. One more incision over the eyeball.

STEP 4: TUNNEL

Material Required

i.300 micron precision depth knife.

ii.Crescent knife.

iii.Keratome-3.2 mm.

Procedure

i.Straight external incision 1 mm behind the limbus, 300 micron deep and 5.5 mm long (depending upon type of cataract).

ii.Crescent knife is used to create a tunnel in the layer across the limbus and 1.5 mm in the clear cornea.

It is not only a tunnel, it is pocket and tunnel, it is tunnel and pocket.

Tunnel is partly in the sclera, partly in the limbus and partly in the clear cornea.

Pocket is mainly in the sclera, pocket is essential to engage the nucleus which is bigger than 4.5 to 5.5 mm size.

iii.Internal incision is made with 3.2 mm keratome. Movement of the keratome anterior and laterally, no strokes, never zigzag, do not cut the tissue while retrieving the knife. Internal incision should be parallel to the limbus. Do it very carefully and knowing that you are doing it parallel. Without knowing the incision you are doing, you may get leakage and astigmatism.

Clear cornea is a better tissue for self-sealing activity than the limbal tissue or scleral tissue.

Advantages

i.Self-sealing wound.

ii.Less disturbing to IO contents.

iii.Regulates IO forces.

Disadvantages

i.May bleed in AC sometime.

ii.Difficult in thin sclera and diseased cornea.

STEP 5: HYDROPROCEDURE

Material Required

i.25 G curved cannula.

ii.2 cc syringe

iii.BSS.

Procedure

i.25 G curved canula attached to 2 cc syringe is introduced through side port underneath the C.C.C. rim.

ii.Small amount of BSS is injected to separate the capsule (0.2 cc).

iii.Exactly opposite to the first site 0.5 cc of BSS is injected under the anterior capsule.

iv.Nucleus is rotated and brought in to the AC.

Advantages

i.Controlled procedure.

ii.Less handling.

iii.ACM keeps the AC well maintained.

STEP 6: NUCLEUS DELIVERY AND

CORTICAL CLEAN UP

Material Required

i.Sheets glide.

ii.Irrigating vectis.

iii.Aspiration cannula with 5 cc plastic syringe.

iv.Hydro cannula with 1 cc syringe.

Procedure (I)

i.Sheet’s glide is introduced behind the nucleus up to 6 o’ clock position.

ii.Pressure is given on the posterior lip of external incision.

iii.Nucleus glides over and comes in the tunnel and engages in the pockets.

iv.More pressure and removal of glide together brings the nucleus out.

Procedure (II)

a.Irrigating vectis can be used in place of sheet’s glide, nucleus engaged in the vectis.

b.Positive pressure created.

c.Vectis is withdrawn along with nucleus.

Cortical Clean up

i. Through side port only.

ii.5 cc syringe with cannula aspirates almost all cortex in the bag.

iii.Water jet is produced with 1 cc syringe with hydrodissection cannula in the bag in all directions, which separates all the cells attached to the pc.

Advantages

i.Close chamber manoeuvre.

ii.Mirror reflex pc.

Disadvantages

i.Extra stress on zonules may lead to zonulysis and bag displacement.

ii.Forceful hydro procedures may tear posterior capsule.

STEP 7: IOL IMPLANTATION

Material Required

i.Regid PMMA or foldable IOL (5.5 mm, 6.00 mm, 6.5 mm optic size)

ii.IOL forceps

iii.Dialer.

Procedure

i.IO lens is held in the forceps.

ii.Leading haptic is placed in the bag.

iii.Optics is inserted in the bag.

iv.Through side port, dialer is used to put the trailing haptic in the bag.

v.IOL rotated to the proper position.

Advantage

i.Tunnel used only for extracting cataract and putting back IOL hence less handling - ensures proper integrity of the tunnel.

Disadvantage

i.Leaking of A C while inserting IOL through tunnel sometimes makes the implantation difficult.

STEP 8: STROMAL–HYDRATION

Material Required

26 G cannula attached to 2 cc syringe with fluid.

Procedure

i.Side port incision and ACM incision both are hydrated properly.

Advantages

i.Self sealing incision

ii.No suture required.

Disadvantage

i.More pressure during stromal hydration may lead to Descemate’s membrane separation.

STEP 9: CONJUCTIVAL CLOSURE

Material Required

i.Cautery

ii.Forceps.

Procedure

i.Conjunctiva is cauterized to it’s original site holding in the forceps and applying thermal or electric cautery.

Advantages

i.Protection to the external tunnel incision.

ii.No suture required.

Disadvantage

i.More cautery leads to contraction of the conjunctival tissue.

STEP 10: SPECULUM REMOVAL

At most care is taken not to pressurize the posterior lip of the external incision of the tunnel while removing the lid clamps.

INTRODUCTION

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. Moreover, in Nepal alone the percentage of curable blindness resulting from cataracts is more than 80%. Estimates for Tibet suggest that the problem is just as critical there. A 1987 Tibet Eye Study revealed that debilitating cataracts were present in 11.8% of the population older than 40 years of age and in more than 50% older than 70 years of age.

Because of increasing population age, the incidence of cataract blindness in developing nations is on the rise. In India, 3.8 million people become blind each year from cataracts. With no improvement in current practices, the World Health Organization estimates a doubling of the world’s blindness by the year 2020. Most underserved countries today are simply unable to cope with new cases, let alone the rapidly growing backlog. Projections show that to eliminate the backlog within the next 25 years, the recent number of 7 million cataracts operated on would have to be increased to 32 million by the year 2020. There is a pressing need for faster, less expensive, and more effective ways to deliver high quality cataract surgery. This chapter will explain our method of delivering high quality, low cost, high volume, cataract surgery as well as our surgical technique. We will take a stepwise approach starting with our sutured, large incision extracapsular cataract surgery with a posterior chamber intraocular lens implant technique and progress to how we currently perform small incision, sutureless, temporal extracapsular cataract surgery.

Prior to embarking on our small incision cataract surgery technique, it is important to master the steps involved in our technique while using a large incision. Our method of cataract surgery uses only fluidics to remove the lens from the eye. A modified capsulotomy technique allows smooth nucleus delivery and facilitates placement of the posterior chamber intraocular lens into the capsular bag. Our delivery technique relies on a team approach that involves nurses and ophthalmic assistants, as well as the operating surgeon. It is an efficient team approach that allows us to perform high volume surgery in a minimum of time and ensure excellent results.

In remote areas, we involve the entire community, performing first a complete epidemiologic survey of the region. We arrange for village organizers to ensure that every person in a region with ocular problems is brought to a central screening area. We then have our patients initially screened by well-trained ophthalmic technicians. These technicians are able to prescribe glasses to patients with refractive errors, antibiotics and other medications for common infections and take care of most minor ocular problems. They screen the patients in need of cataract surgery or more sophisticated ophthalmic care. The ophthalmologist then only examines the patients that have been pre-screened to have pathology.

Once the patients have been selected for cataract surgery we have a systematic approach to reduce the chance of infection and deliver high-quality, highvolume care. This is an integral part of our cataract surgery, and will be discussed prior to the details of our actual surgical technique. We will then take a step-wise approach to how we perform our small incision surgery.

Our cataract technique has been developed to be one that is applicable for all types of cataracts. It is extremely safe for even most difficult cases with the hardest and largest nucleus, as well as traumatic, pediatric, and uveitic and virtually all other cataract cases. The nucleus delivery involves only fluidics and water pressure to remove the lens from the eye. It is very safe both for preserving the posterior capsule, and the corneal endothelium. Finally, it is a technique that is easily replicable and can be performed with a minimum amount of time without any expensive extra equipment.

PREOPERATIVE MANAGEMENT

As stated above, our preoperative management begins with the surgeon examining the patients who have been pre-screened by ophthalmic assistants. A large majority of our cases have mature cataracts with no view of the posterior segment, even with indirect ophthalmoscopy. The ophthalmic assistants carefully check for a relative afferent pupillary defect to obtain a gross assessment of the retinal and optic nerve function. At our larger eye centers, all patients undergo analysis with a B-scan ultrasound at the time of their biometry where axial length is measured by A-scan ultrasound and keratometry is performed.

The evening before surgery, the patients have their faces washed vigorously with soap and clean water. Antibiotic drops and ointment are instilled the night before surgery. Prior to surgery the ophthalmic assistants cut the eyelashes closely, apply antibiotic ointment over the eyelashes and instill fluoroquinolone eyedrops into the eye. The patients receive another dose of fluoroquinolone antibiotic and at the time of instillation of dilating drops. The ophthalmic assistants now place a local anesthetic in the fornix, and the eye is washed and prepped with Betadine. Trained ophthalmic technicians then perform a peribulbar and a 7th nerve block. After the anesthesia, the eyes again receive a full prep with Betadine scrub and pressure is held over the eye with a Betadine soaked gauze. This pre-operative cleaning and sterilization regimen allows a rapid turnover time between cases while maintaining a very low infection rate.

At the conclusion of one case, a new patient is brought onto the operating table from one side as the operated patient is helped off the table from the other side. The surgeon performs a final Betadine prep and then instills a small amount of 5% povidone iodine into the fornix of the eye prior to surgery. While the surgeon

is prepping and draping the eye, the scrub nurse will have completed arranging a new instrument set which has been brought out for the new patient. Surgery is able to continue with a typical delay between cases of less than 3 minutes.

SURGICAL TECHNIQUE FOR CONVENTIONAL CATARACT SURGERY

Our standard surgical technique begins with the eye being opened with a lid speculum. A 4-0 silk suture placed in the superior rectus muscle tendon for traction. Next, a superior limbal peritomy is performed followed by gentle electrocautery to the limbal vasculature. A blade breaker is used to create a sharp razor blade, which then makes a 10 mm half-scleral thickness limbal groove parallel to the limbus. A straight 26-gauge needle is next inserted through the groove and turned so that it is beveled to the side. A V-shaped cut is made in the anterior capsule with the side of the needle so that the apex of the V is connected at the 12 o’clock position. This capsular incision is possible to complete easily and completely even with a hypermature lens or difficult capsular visualization on a white or black capsule. The needle is attached to a syringe with balanced salt solution. If liquid cortex obscures the view, this can be easily irrigated away using a small amount of pressure through the syringe.

Once the V-shaped incision is completed in the anterior capsule, the anterior chamber is entered with a razor blade and a 10 mm incision is completed in a twoplane fashion along the limbus with corneal scissors. Next, a manual irrigation aspiration Simcoe cannula is used to hydrodissect and irrigate under the capsular flap. A fluid wave circles around the lens and the capsular opening fishmouths superiorly. Irrigation floats the lens gently out of the capsular bag and into the anterior chamber. The lens is then easily irrigated out of the eye. No vitreous pressure is used to express the lens. There are no extracapsular tags. The expression of the lens from the eye is always atraumatic with no stress on either the capsular bag posteriorly or the corneal endothelium superiorly.

Once the nucleus has been irrigated from the eye, any residual cortex is removed with the Simcoe cannula. When all of the cortex has been removed an air bubble is instilled to re-form the anterior chamber. A posterior chamber intraocular lens is then inserted into the capsular bag under air. The edge of the corneal incision flips inward as the lens is inserted to trap the air bubble and protect the corneal endothelium during placement

of the lens. The anterior flap of the capsulotomy floats upward with the air insuring that the leading haptic of the intraocular lens automatically goes under this capsular flap. The trailing haptic is then easily placed or dialed into the capsular bag.

Once this has been completed, the Simcoe cannula is used to irrigate the air from the eye and the anterior chamber is re-formed with balanced salt solution.

Keeping the anterior chamber inflated with fluids from the Simcoe cannula, a curved Vannas scissors is brought in with the other hand and slid over the top of the implant to the edge of the anterior triangular capsular flap. A small cutis then made at the base of the V-flap. This torn edge is grasped with suction from the Simcoe cannula and a smooth capsular tear is made, completing a capsulorrhexis with the V superiorly and a smooth curved capsular tear at the base. The lens now sits completely within the capsular bag with a V- opening toward the apex and a smooth tear to the 6 o’clock position, completing what we call the Himalayan capsulorhexis.

A new air bubble is then instilled into the anterior chamber. The limbal incision is closed with a running 10-0 nylon suture starting within the wound and running to the far end of the wound and back again to tie securely with the knot buried within the wound. At the conclusion of the operation the anterior chamber is refilled with balanced salt solution. The superior conjunctiva is injected with dexamethasone and gentamicin that balloons it up over the corneoscleral wound. The eye is then dressed with ciprofloxacin and dexamethasone and patched. Postoperatively, the patient’s receive combined steroid and antibiotic drops every 2 hours for the first 3 postoperative days, then 4 times per day for the next 2 weeks, with steroid and antibiotic ointment at bedtime.

This extracapsular technique is highly reproducible with a minimal amount of intraoperative and/or postoperative complications. The operative time for the technique decreases with the increasing experience of the surgeon. Experienced doctors typically complete four uncomplicated cases per hour. It is essential to master this large incision extracapsular technique prior to attempting our small incision surgery. The critical steps to be mastered that are unique to our method include; irrigating the lens out of the capsular bag and into the anterior chamber, completing the Himalayan capsulorhexis by cutting the base of the triangle and creating a smooth tear holding the capsule with the Simcoe cannula, and placing the intraocular lens easily into the capsular bag. Once this has been accomplished,

we then slowly transition to our small incision sutureless technique.

SMALL INCISION SUTURELESS

CATARACT SURGERY

Our sutureless, small incision, cataract surgery relies on the same use of fluidics that we use for our conventional extracapsular surgery, except that the lens is delivered through a small, self-sealing tunnel incision. We do not require any expensive viscoelastics or complex maneuvers to break the nucleus within the anterior chamber. The key steps to this surgery are mastering the gentle irrigation of the nucleus into the anterior chamber through the use of fluidics, and irrigating the lens out of the eye through a well-constructed, selfsealing tunnel incision. Our technique involves a selfsealing scleral tunnel. We construct a wound that has a larger internal opening than the external scleral incision. The section must have a properly constructed architecture so that intraocular pressure seals the internal wound. We then gently irrigate the lens into the anterior chamber as with our large incision surgery. We then use the same fluid dynamics that were originally described by Dr. Michael Blumenthal to help the lens flow into the funnel of our incision and irrigate the nucleus out of the eye. However, we differ from Dr. Blumenthal in that we do not require an anterior chamber maintainer to provide fluid pressure behind the lens. We rely on the Simcoe cannula and positioning of the eye to irrigate the lens from the eye.

It is best to begin learning our small incision sutureless surgery with the approach the surgeon is most familiar. We generally advocate beginning surgeons start with a superior approach, utilizing a superior rectus bridle suture. This allows easy positioning of the eye throughout the case. Moreover, this superior approach is preferred for the novice because of the occasional need to convert to a sutured extracapsular cataract extraction. It is also easier to perform high volume superior approach surgery on one standard operating table. As will be discussed later we modify our table for temporal surgery.

A fornix based conjunctival flap is created utilizing a peritomy from approximately the 10 o’clock to the 2 o’clock position down to bare sclera. Light cautery is used to blanche the scleral incision area. Next, an initial partial-thickness 30-50% scleral depth 6-7 mm scleral incision is made tangential to the limbus. At its midpoint, the incision should be approximately 1.5-2 mm posterior to the limbus. This incision can be

made with a razor blade fragment or commercial sharp rounded blade. The former helps with cost containment. Next, a scleral corneal tunnel is fashioned with an angled beveled up crescent blade or similar. From the initial incision, the tissue is dissected in a single plane forward through sclera and limbus approximately 1-1.5 mm into the clear cornea. The plane should be parallel with the ocular surface. The dissected pocket should extend nasally and temporally to the limbus so that its transverse extent is much greater in the cornea than at the scleral opening. This results in a purse or funnel shape to the yet-to-be completed tunnel. It is important to exaggerate this internal flaring of the tunnel, particularly during the initial transition stage.

Next, the same triangular capsulotomy used in our large incision surgery is performed with the apex at 12 o’clock. Again this is made using a straight 26-gauge needle attached to a 1 ml syringe filled with anterior chamber irrigation fluid. The needle is passed into the anterior chamber through the recess of the scleral corneal pocket at about its midpoint. Using a beveled tip of the needle, the linear cut in the capsule is again made from the 4 o’clock to the 12 o’clock position and another then cut from 8 o’clock to 12 o’clock so that the two join at 12 o’clock. The apex of the capsulotomy can then be lifted with the tip of the needle and peeled towards 6 o’clock. This confirms that the capsular cuts are complete and frees any anterior capsule cortex adhesions. If the anterior capsular chamber shallows during these maneuvers or if the view is obscured by liquefied lens material, a small amount of anterior chamber irrigation fluid can be injected through the needle to deepen the chamber or clear the view.

With this accomplished, a sharp pointed keratome or slit knife is used to open the inner aspect of the scleral corneal tunnel into the anterior chamber. The sides of the blade are then used to open the corneal end of the tunnel along its full extent to the limbus nasally and temporally. The purpose of this internal flaring of the tunnel is to allow and encourage the nucleus to engage in the tunnel at the time of expression. It is essential that the internal opening to the tunnel is widely opened. The eventual size of the internal and external openings of the tunnel can and should be varied according to the anticipated size and hardness of the nucleus.

The next step may be varied, depending on the maturity of the cataract. For the less advanced cataract, a Rycroft cannula is used to inject anterior chamber irrigation fluid into the lens to delaminate the lens components and separate the nucleus and epinucleus from the cortex. The whole of the nucleus or one of its

poles may prolapse from the capsular bag into the anterior chamber. Hydrodissection is not required with the more advanced cataracts. In these cases, and where the less mature cataract has been mobilized with hydrodissection, the process of subluxating the lens nucleus into the anterior chamber can be initiated or completed by using a flowing Simcoe irrigationaspiration cannula. The nucleus is gently rotated and tilted. In-flowing fluid is directed behind the nucleus and irrigation is performed under the capsular flap. The nucleus is delivered into the anterior chamber using fluidics and hydrostatic forces to gently rise into the anterior chamber. This maneuver takes a small amount of practice to master. Because the anterior chamber is closed, if difficulty occurs while hydro-expressing the nucleus into the anterior chamber it is wise to convert at this stage to a large incision extracapsular cataract extraction to be certain not to traumatize the cornea or posterior capsule. During the learning curve it is important to remain slow and gentle and convert when needed. Soon it will be very natural to bring the lens above the iris using only fluid dynamics.

At this point, a combination of mechanical and hydrostatic forces can be used to deliver the nucleus from the anterior chamber into the tunnel incision, and then irrigate the lens out of the eye. Once the nucleus has been irrigated above the iris into the anterior chamber, there are several ways one can remove the nucleus. We do not suggest sectioning or fragmentation of the nucleus in the anterior chamber. However, whichever method is chosen it is important to confirm the adequacy of wound size for the observed size and consistency of the nucleus.

One method of nucleus delivery begins by rotating the eye downward. We use toothed forceps to grasp the lip of the incision at one end and rotate the eye downward slightly. Next, we pass a vigorously flowing Simcoe cannula into the anterior chamber around the side of the nucleus then gently underneath it until the tip is beyond the 6 o’clock pole of the nucleus and clearly visible. The accumulating irrigational fluid from the cannula in this position tends to push the nucleus so that it engages the internal mouth of the corneoscleral tunnel. A combination of hydrostatic pressure and a gentle lifting action with the tip of the Simcoe, rather like the action of a spoon, forces the nucleus further into the tunnel. The external foramen of the tunnel can be opened using downward pressure of the heel of the Simcoe. As the nucleus moves into the tunnel, epinucleus may strip off or the nucleus may fragment. However, the whole nucleus should usually be

delivered from the eye in one motion. This is our standard and preferred method of nucleus delivery and yields clear corneas postoperative day one.

A second method utilizes an irrigating vectis that is passed into the anterior chamber and under the dislocated nucleus. The bulk of the nucleus can then be lifted and drawn into and through the corneoscleral tunnel using irrigation to add a hydrostatic push to the pull of the vectis. This technique allows rapid delivery of the nucleus and may allow an inexperienced surgeon to more easily deliver the nucleus until full comfort with simple hydrostatic forces has been acquired through experience. It must be cautioned not to lift up too vigorously on the nucleus as this may engage the corneal endothelium and result in an edematous cornea on postoperative day one.

The Simcoe cannula is then used as usual to remove epinuclear and cortical debris from the anterior chamber, posterior capsule, and recesses of the capsular bag. Next, the Rycroft cannula is used to inject air into the anterior chamber. Finally, a polymethylmethacrylate intraocular lens is passed into the eye. The wound construction is such that the air is usually retained in the anterior chamber during this maneuver. However, if this is not the case, the leading haptic intraocular lens can be used to then fold the anterior lip of the incision to prevent escape of the air. The leading haptic is passed into the capsular bag behind the triangular flap of anterior capsule, indicating correct placement within the bag. Using straight or angled tying forceps, the upper loop is placed into the bag behind the straight cut edge of the anterior capsule. Fine positioning is done with a Simcoe cannula or a lens-positioning hook if required. With a Simcoe cannula in moderate flow, the anterior chamber air is removed and replaced with irrigation fluid. The flowing Simcoe cannula continues to maintain the anterior chamber as a fine blade Vannas scissors is introduced. The scissors are used to make a small cut at either the nasal or temporal base of the triangular capsular flap. Next we again use the Simcoe cannula to engage with the edge of the triangular flap on the apical side of the cut in the same manner as with our large incision technique. The capsular flap is gently torn away from the base with a circumferential motion. Care must be taken to ensure the tear does not extend radially toward the equator. With continuing single cannulation aspiration, the freed anterior capsular triangle remains engaged in the cannula port and both the cannula and capsule are removed from the anterior chamber. The Simcoe cannula is used to ensure the anterior chamber is reformed to a satisfactory depth and

ocular tension. Avoid the temptation to over-pressurize the eye.

The wound, being a 3-planed shelled incision, should self-seal. This may be confirmed by pressing on the globe with an instrument while observing the wound for leakage. If there is leakage, we recommend suturing the wound. With experience, we find that less than 1% of our small incision cataract surgeries require any sutures. Subconjunctival injection of antibiotic and steroid is then given just above the cut edge of the conjunctiva. This will balloon the conjunctiva and move it toward the limbus, covering the scleral wound. Caution should be taken to ensure there is not so much pressure on the posterior portion of the wound that there is a wound leak. The lids are closed and a dressing is applied in the usual way. The postoperative course is similar to that for our standard extracapsular technique.

Our results have shown in both the hospital and eye camp settings, a very low complication rate and excellent visual recovery for both our sutured and sutureless techniques. However, the sutured technique leads to considerably more postoperative astigmatism and a lower level of uncorrected visual acuity. 92% of our patients obtained 20/40 or better corrected visual acuity with the sutured technique, however, only approximately 50% obtained 20/40 or better visual acuity uncorrected. For our sutureless technique, 65% of the patients had uncorrected visual acuity of 20/40 or better at 8 weeks postoperatively. The mean corneal astigmatism induced was 0.93 diopters. The sutureless small incision surgery also has advantages with regards to speed and cost savings. Sutureless surgery also has less late postoperative wound or suture complications.

TEMPORAL SMALL INCISION EXTRACAPSULAR SURGERY WITH POSTERIOR CHAMBER INTRAOCULAR LENS

Although the results of our superior small incision sutureless cataract surgery are very good, the superior incision does induce a small amount of with the rule astigmatism that can affect uncorrected visual acuity. We found approximately 0.61 Diopters of induced astigamatism at three months that drifts to approximately 0.93 Diopters at one year. Postoperative astigmatism is a concern in extracapsular cataract extraction and one of the most significant contributors to postoperative visual acuity. Minimizing postoperative astigmatism in order to provide the best possible visual outcomes is essential, particularly in developing nations where limited postoperative eye care is available.

Numerous factors have been hypothesized to affect postoperative astigmatism in cataract surgery. Intraoperative factors such as the length and location of incision and the type and placement of suture have received the most attention in the literature. The majority of studies have examined phacoemulsification surgery, which showed that smaller scleral incisions and sutureless incisions tend to induce less astigmatism. The use of temporal incisions in phacoemulsification has also been investigated.

Only a few studies have directly addressed the astigmatic effects of alternate incisional meridia in extracapsular surgery. The results of one series found, that a lateral approach produced significantly less astigmatism with prolonged astigmatic stabilization when compared to a superior incision. The visual outcomes of the temporal incision surgery in this study were not statistically different from phacoemulsification surgery. These results were not supported by an Australian series that used Holladay-Cravy-Koch’s method to measure the magnitude and direction of astigmatic change. In this study, the temporal incision group had high astigmatism while the superior incision group had low astigmatism, however visual acuities were the same in the two groups. Another study found that a lateral incision technique was useful in reducing astigmatism.

We find less induced astigmatism when the same small incision extracapsular surgery is performed from a temporal approach, yielding improved uncorrected visual acuity. We have now switched our standard procedure to a temporal incision in all cases except where a high level of existing with-the-rule astigmatism is present preoperatively. When we perform a highvolume of small incision cataract surgery from a temporal approach, we utilize a long table with the surgeon seated in the middle with easy access to his foot control pedals. Patients are brought to the operating table such that patients with left eye cataracts will have their feet extended to the surgeon’s left, and those who will have surgery on their right eye have their feet extended to the surgeon’s right. In this manner, we are able to perform high-volume surgery with the same rapid turnaround time as with our superior incision technique.

The surgeon must be experienced and comfortable with small incision cataract surgery before switching to the temporal approach, as it is more difficult to extend the wound and convert to a sutured surgery if a complication arises. Otherwise, the surgical technique is exactly the same. A tunnel incision beginning with a

half-thickness scleral groove approximately 1.5 mm behind the limbus that flares out to create a funnel with a wider opening into the anterior chamber. The V- capsulotomy is again performed with the apex towards the surgeon at either the 3 of 9 o’clock position. The lens is hydrodissected and fluid gently moves the lens to the anterior chamber. The eye is then rotated nasally with Simcoe cannula placed beneath the lens such that fluidics brings the lens into the tunnel incision and the nucleus is hydroexpressed. Completion of the case is then exactly the same as for ours superior incision cataract surgery with the one of exception that a single absorbable suture is used to close the conjunctiva over a scleral wound, as we found that some cases left the wound exposed. This added step of a single suture to close the conjunctiva does not significantly alter the surgical time or cause problems for the patient.

In order to quantify the advantages of the temporal approach we conducted a prospective randomized trial where 100 consecutive patients had one eye receive a superior incision and the fellow eye a temporal small incision, sutureless, extracapsular cataract surgery. We conducted this study to examine whether a temporal incision in conjunction with a sutureless closure will decrease postoperative astigmatism in extracapsular cataract extraction, thereby maximizing uncorrected postoperative visual acuity. The temporal approach does produce less induced post-operative astigmatism and improved uncorrected acuity over the superior incision

Methods

A randomized prospective clinical trial was conducted in which 100 bilateral cataract patients (53 F/47 M, Mean age 61.9 + 10.6 years) had one eye assigned to a superior incision extracapsular cataract extraction with posterior chamber intraocular lens implantation and the other eye assigned to an identical surgery with a temporal incision approach. Both the temporal and superior incision approach surgeries were performed by the same two surgeons at Tilganga Eye Center (Kathmandu, Nepal) in December 2002.

The extracapsular cataract extraction with posterior chamber intraocular lens surgery was performed as described previously. In brief, with the patient under retrobulbar anesthesia, a 6-7 mm limbal half-scleral thickness limbal groove was made, followed by a scleral tunnel extending to 10 mm at the corneal entrance, and a V-shaped capsulotomy created using a straight 26 G needle. The vertex of the “V” is at 12 o’clock in the

superior incision cases and at 3 o’clock (OS) or 9 o’clock (OD) in the temporal incision cases. The internal width of the scleral tunnel was then enlarged. After manual irrigation with a Simcoe cannula, the lens was floated out of the capsular bag and fluid pressure was used to bring the nucleus into and through the tunnel, residual cortex was aspirated, and a posterior chamber intraocular lens was inserted. The power of the IOL was determined preoperatively based on keratometry measurements and axial length. After creating a cut with a curved Vannas scissors, the capsulorrhexis was completed. Air and viscoelastic were removed from the anterior chamber, which was reformed with a balanced salt solution. Dexamethasone and gentamicin were injected into the conjunctiva, and the eye was patched overnight.

OUTCOMES

Keratometry measurements were made at 1 day, 1 week, 1 month, and 3 months postoperatively. At each of these points, the absolute value of the simple subtracted astigmatism [k1-k2], absolute value of the simple subtracted change in astigmatism from preoperative values [(Post-op k1-k2) - (Pre-op k1-k2)], and the astigmatic change were recorded. Refraction and corrected visual acuity were measured at 1 and 3 months postoperatively. To assess corneal astigmatism, the Holladay-Cravy-Koch spherocylinder method of Surgically Induced Refractive Change (SIRC) was used at 1 and 3 months.

Astigmatic Change

Preoperatively, there was no significant difference in mean absolute astigmatism between the temporal incision (0.581 + 0.50 D) and superior incision (0.718 +0.65 D, p = 0.06) eyes. One week postoperatively, the patients in the superior incision group had a higher absolute astigmatism (1.67 + 1.3 D) than the temporal incision group (0.79 + 0.7 D). Eyes that underwent the superior incision surgery also showed a larger absolute astigmatic change from preoperative measurements (1.60 + 1.3 D) than those that underwent the temporal incision surgery (0.8 + 0.8 D, p = 0.006) (Figures 19.1 and 19.2).

A comparison of the Surgically Induced Refractive Change (SIRC) as measured by Holladay-Cravy-Koch’s method at 1 month showed greater magnitude of induced cylindrical change among the superior incision group (1.437 + 0.9 D, n = 57) when compared to the temporal incision group (0.892 + 0.84, n = 58) (p = 0.001).

In addition, the superior section showed greater against- the-rule (ATR) change (0.662 + 1.57 D) when compared to the temporal incision group, which manifested a smaller degree of with-the-rule (WTR) change (–0.163 + 0.81 D, n = 58, p = 0.002). At 3 months postoperatively, these results persisted, with the superior incision showing a larger ATR astigmatic change (0.61 + 1.65 D, n = 68) while the temporal incision showed a smaller WTR change (-0.23 + 0.95 D, n = 47) (p = 5.9E-5).

At 1 month postoperatively, there was a significantly higher percentage of superior incision patients (75%) who had ATR astigmatism, as opposed to temporal incision patients (38%: Z = 4.36). This difference also held true for ATR astigmatic change (65% among SS vs. 38% among TS: Z = -3.09). Conversely, a significantly higher percentage of temporal section patients manifested WTR astigmatism when compared to superior section patients (58% vs. 19%: Z = 4.53) and also WTR astigmatic change (55% vs. 23%: Z = 3.69). An identical pattern was also found at 3 months after surgery.

Refraction and Visual Acuity

At 1 month postoperatively, patients in the temporal incision group required a lower cylindrical correction (–0.91 + 0.71 D) than the patients in the superior incision group (–1.47 + 1.09 D) (p<0.001). This pattern persisted at 3 months after surgery (temporal incision -0.99 + 0.76 D, superior incision –1.68 + 0.88 D). There was no difference in corrected visual acuity between the two groups at 1 month after surgery (p=0.52, 0.07). 91.4% (n=93) of temporal section patients and 92.0% (n=88) of superior section patients had acuities of 20/40 or better one month postoperatively. Only one patient (1.1%) in the temporal section group and two patients (2.3%) in the superior section group had corrected visual acuities of 20/80 or worse. These patients had preexisting macular problems that were not picked up by B scan ultrasonography and were hidden behind mature cataracts. There was no difference in the magnitude of spherical correction between the two groups.

COMPLICATIONS

There were no cases of posterior capsular rupture and no cases of vitreous loss.

There were no other visually significant complications in this study. Ten percent of patients in both groups developed transient corneal edema, which resolved by one week postoperatively.

DO’S AND DON’TS

In many developing nations, extracapsular cataract extraction is still the most widely used and available cataract surgery. In rural areas and in eye camp settings, phacoemulsification is too expensive and bulky to be an effective surgical option. Therefore, given the reality of extracapsular surgery with intraocular lens implantation in these settings, minimizing postoperative refraction is of paramount importance.

Our results clearly suggest that sutureless temporal incisions produce less postoperative corneal astigmatism than superior incisions in extracapsular cataract extraction with posterior chamber intraocular lens implantation. The degree of astigmatic change induced by the temporal incision ECCE/PCIOL surgery compares favorably with published data on extracapsular cataract surgery and scleral tunnel approach phacoemulsification. Our results support the claim that a superior incision induces a higher magnitude ATR astigmatism while the temporal incision induces a lower magnitude WTR astigmatism. While the exact difference in cylindrical power between the two groups varies based on the method of analysis, most of our measures show a difference of 0.5-0.7 D of cylindrical refraction at 1 and 3 months after surgery. While definitive studies are yet to be done, there is general consensus that this amount of astigmatic change is likely to be visually significant. ATR astigmatism is thought to be more visually significant than WTR astigmatism, and the surgically induced astigmatic change might be compounded over time by the ATR change that many people develop with age.7

All of the patients in this study were operated on at Tilganga Eye Centre in Kathmandu where excellent refractive services are available. This could explain the fact that the corrected visual acuities in the temporal and superior incision groups were identical despite the difference in astigmatic cylinder. However, the vast majority of people blind from cataracts in Nepal live in rural areas. For many of them, cataract extraction surgeries done at ‘eye camps’ may be the only eye care they receive. Such patients are often unlikely to seek regular refraction after surgery due to financial barriers and a dearth of optical shops. The optical shops these patients may have access to often lack a wide range of cylindrical corrective lenses. Rigid contact lenses are rarely available outside of the large cities and impractical for use in most rural settings.

The excellent visual outcomes and the low complication rates confirm those of the initial studies introducing this sutureless extracapsular cataract

Figure 19.1

Figure 19.2: Quality is the best driver of demand

Figure 19.3: Trained ophthalmic technicians give peribulbar anesthesia