Following ab-externo fornix based conjunctival flap (Fig.1), a frown tunnel incision is given with B.P.blade no.15. We never use diamond knife for scleral incision and tunnel dissection, as it is very costly to maintain. The size of incision, the distance between the ends, mostly varies from 6.00 to 7.00mm, however if it is nuclear, rock hard cataract incision may be bigger up to 7.50mm. It is to be noted that the incision can be extended at any point of time. The anterior extent of the incision is always more than 2mm behind the limbus and two ends can be 4 to 5 mm behind the limbus. The tunnel was dissected (Fig.2) with the help of sharp edge tunnel (crescent) blade angled bevel up no 582620/582623.The incision depth is usually up to 2/3rd thickness of sclera. One should be extremely careful not to be very superficial or too deep to avoid complications like buttonhole or cyclodialysis. Further the thin flap has always the tendencies to tear. The internal incision, which is entry to anterior chamber, was made with the help of sharp edge sharp tip keratome, angled bevel upno.552620, 552820 and latter extended after capsulorhexis.
|Fig. 1: Conjunctival flap reflected, hyper mature cataract||Fig.2: showing sclerocorneal tunnel dissection with crescent blade.|
Continuous curvilinear capsulorhexis, which was originally described, by both Gimbel (Canada) and Neuhann (Germany) has revolutionized the modern cataract surgery. This was performed with either 26G bent needle or with the help of Masket Capsulorrhexis forceps. Forceps is very useful in paediatric cases, because the capsule is very elastic in children. A rhexis of 6 to 7.0mm diameter is essential, how-ever if it is nuclear cataract, one or two relaxing incision are made at 2 0’clock and 10 0’clock meridians with the help of 26G bent needle. Whenever there is no red reflex, rhexis was easily performed by using trypan blue.
This step is very essential before nucleus delivery. It is carried out with 2 ml syringe using curve 24G west lacrimal canula; the fluid was injected beneath the anterior capsule in one or two places, however large volume is avoided. Fluid wave or Golden ring reflex are observed to ensure complete hydro dissection and hydro delineation.
There are different techniques available for nucleus management in SICS, namely hydro-expression, phaco-sandwich, phaco-fracture, irrigating vectis etc. We restrict the discussion to microvectis technique only, as this is our preferred method of nucleus delivery in all types of cataract.
After reforming the anterior chamber with viscoelastic the superior pole of the nucleus was engaged, lifted up and rotated with the help of an I.O.L. dialer or 26G needle and subsequently prolapsed into the anterior chamber. Once the superior pole lifts up, viscoelastic may be injected underneath to make nucleus rotation easy. The nucleus rotation is done either clockwise, anti clockwise or both to luxate the nucleus completely into anterior chamber. Sometimes it is difficult to luxate the nucleus into anterior chamber in immature cataract. It is due to too much hypotony or incomplete hydrodissection , one has to reform the a/c with viscoelastic and do the hydrodelineation to overcome this difficulty. Similarly this problem may be encountered in nuclear cataract when the rhexis is small, where relaxing incision is given over the anterior capsule. Once the nucleus in anterior chamber, viscoelastic is placed both anterior and posterior to the nucleus. This step is essential to avoid endothelial damage. A microvectis or lens loop, 3-4 mm in size is introduced underneath the nucleus and the nucleus was expressed by gently applying forward pressure. This step is done in a more controlled fashion under direct visualization to avoid trauma to cornea and iris. Sometimes the epinucleus or portion of the cortex will be sheared off by the anterior lip of the incision. The remaining portion of cortex and epinucleus can be easily rotated and extracted by either by viscoexpression or aspirated by simcoe I/A canula. Visco-expression is carried out by injecting viscoelastic into a/c while depressing the posterior scleral lip. For easier removal of nucleus in nuclear cataract we recommend incision of 7-7.5mm to avoid intra operative complications, as stated earlier, some times two relaxing incisions over the anterior capsule, required in rock hard cataract to avoid complication like capsular tear or zonular dialysis. We never use anterior chamber maintainer nor irrigating vectis in this technique as we believe that viscoelastic protects the endothelium in a better way than BSS.