|Year : 1982 | Volume
| Issue : 5 | Page : 451-453
Micro-surgery in cataract extraction
J Agarwal, T Agarwal, R Suryaprakash
Agarwal's Eye Institute, Madras, India
Eye Research Centre, Dr. Agarwal's Eye Institute 13, Cathedral Road, Madras- 600 086
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Agarwal J, Agarwal T, Suryaprakash R. Micro-surgery in cataract extraction. Indian J Ophthalmol 1982;30:451-3
Spectacular advances in ophthalmology are attributed mainly to the development of operating microscope.
The most important step in cataract surgery is an adequate section and accurate wound closure.
The section is made after a fornix based conjunctival flap. A partial scleral thickness groove is made about 3 mm from the limbus to an extent of about 160-180 from 3 0' clock to 9 0' clock position. A lamellar flap of sclera is dissected out towards the limbus till the blue line is seen. Anterior chamber is entered with a blade beneath the flap and the section is enlarged with corneal scissors so that corneoscleral section has a lamellar scleral flap to cover. The main advantage of this type of section is that it will not give rise to irregular astigmatism and suturing is easy.
The suturing after the lens removal is another important step of the operation. This requires delicate instruments and fine sutures.
| Instruments|| |
The needle holder should be light and short in length so as not to project above the trip of the hand when held in its most advantageous operating position. It should be used only for engaging microsurgical needles. The inner aspect of the jaws should be flat and smooth. There should be no lock or holding catch because the tip of the needle will jump when such a lock is engaged or released. This can result in misdirection of the needle. Using the finger pressure only the surgeon can grasp or release the needle more accurately without any jerk. It is necessary to shift the needle holder jaws to different positions on the needle shaft 3 or 4 times for taking the full bite. So it is advantageous to use needle holder without locking system.
The suture tying forceps should have tips with the flat surface, like smooth tipped Harms tying forceps so that no damage is done to the nylon. The tissue holding forceps should be a fine toothed forceps like Colibri type.
We prefer spatula type of needle than the reverse cutting needle. Since the reverse cutting needle which has inverted triangular cutting profile tends to cut more posteriorly than desirable and does not have the lateral directional stability inherent in the spatula design.
The suture material which has the maximum advantage is the 10/0 nylon. The advantage of nylon is that it has a smooth exterior surface that does not catch or abrade tissue as it is drawn through. It is of uniform diameter.
| Basic techniques in suturing under microscope|| |
1. Suture should be shorter than 15 c.m.
2. Magnification should be low.
3. An experienced assistant should assist.
The assistant has to place the needle and the free end of the suture within the field
of the surgeon's vision. The reason being that the surgeon field is narrow. Keeping the needle also in view reduces manipulation of both suture and needle lessening the damage to either one. The needle requires careful handling. The needle should be grasped in the centre of the shaft. If it is held too close to its shank directional stability is lost. If it is held too close to the tip leverage is lost. The curve of the needle only determines the depth of placement and point of exciting. Ideally the needle should be 5-6 mm in length with a curvature between 160-170. It is necessary to check the sharpness of the needle constantly and its performance by close observation through high magnification. A needle that does not pass well causes damage to tissues in itself and secondarily through the fixating tissue forceps damaging the tissue. The cornea is lifted with the Colibri tissue forceps with single tooth on the epithelium and double tooth on the stroma and the tissue edge is slightly everted. The needle is inserted vertically into the cornea just behind the forceps tip and then pushed horizontally till the tip is just visible. The forceps used to stabilize the opposing edge must be reversed to that the double teeth always engage in the stroma and the single tooth is engaged in the anterior sclera. Through corresponding points in the sclera the needle is passed horizontally and then the needle is rotated up so as to make a "U" turn. Damage to the tissue is avoided by not holding the sclera with forceps but giving counter pressure on the surface of the sclera close to the expected point of exit. Then the needle is grasped and taken out of the sclera. For proper wound alignment the cut ends of the vessels which cross the wound can be best utilised. Corresponding points on either side of the wound edge can be marked by making superficial surface razor cuts with the blade and then applying a dye to make it visible before applying sutures. The nylon requires delicate handling though its strength for manipulation is out of proportion to its size and its elasticity because it is a thin single thread, it is more susceptible to weakening or breaking. It should never be grasped with a needle holder or tissue forceps. Suture tying forceps alone is used to grasp the thread.
The direction of the suture should be radial to the linibus. Spacing should be of 1 mm. Usually the distance from the wound edge is equal on each side, but this is not very essential. While tying the sutures first a triple loop is drawn around the fine suture tying forceps and the long end is pulled away from the surgeon. This results in the triple loop that pulls out straight without twisting. The second single loop is made in the opposite direction and the long thread pulled towards the surgeon. As the threads are pulled up and tightened the extended triple loop is brought together like a closed spring and held snugly by the second single loop. Third single loop is made in the same direction of the first loop and tied without twisting. The tension in the knot should be just enough to appose the edges of the wound. It should never be too tight or too loose. Too tight sutures can cause irregular astigmatism as well as tissue necrosis. Too loose sutures will not serve any purpose and it will give rise to contant irritation and may interfere with smooth tissue healing. While tying the knot the keratometer ring is noted constantly and tied with adequate tension so as to maintain the round shape of the ring. If the keratometer ring is oblong the long axis of the ring is the Platte meridian and correspondingly the suture in that meridian is tightened to make the ring round. After the sutures are tied, the knots are pulled through the needle tracts to avoid irritation. Too tight knots should be cut off and another suture applied. Minimal reaction and good apposition persists only as long as the sutures remain immobile in the tissue. Therefore a suture that is fixed too loosely or that becomes loosened after it is placed will irritate the tissue and interfere with continuous smooth healing.
Vitreous loss in inevitable cases is tackled well by means of a vitrector under high magnification so that no vitreous is left in antericr chamber.
| Conclusion|| |
Surgery is an art as well as a science. Best performance from an artist comes after days of practice. To surgeons such practice is not only important for their own sake but also for the ultimate good of the patients on whom their skills will be performed. In an attempt to switch from tactile manual surgery to visually oriented surgery by practising on animal eyes or eye bank eyes, the experienced ophthalmologists will immediately be able to apply the increased benefits of microsurgery to the standard operative procedures. They can also readily learn the new microsurgical techniques as they introduced to give the maximum benefit to the patient.