INJURIES OF THE CORNEA AND SCLERA

CORNEAL ABRASIONS

This extends the general method for an eye injury in Section 60.1.

The patient’s eye is red and watery and his lids tightly closed. He may have ciliary injection, but his visual acuity is normal. After looking at his eye carefully, you can find no foreign bodies on the surface of his cornea, or underneath his upper lid. Instead, you see an abrasion, which you may only find after you have stained it with fluorescein.

If an abrasion is clean, and is only visible after staining with fluorescein, and there are no signs of infection, instil chloramphenicol eye drops and shield the patient’s eye (23.1). Check it daily, and instil chloramphenicol, until it no longer stains with fluorescein.

If his cornea becomes cloudy, it is infected. He now has a corneal ulcer so see below.

\includegraphics[width=\linewidth ]{/home/kumasi/Desktop/primsurg-tex/vol-2/ch-60/fig/60-5.eps}
Figure 60.5: TWO CORNEAL LESIONS. A, a corneal abrasion. B, a corneal ulcer. If you are not careful, an ulcer can follow an abrasion.

CAUTION! To prevent infection, always instil chloramphenicol eye drops after any corneal abrasion and shield the eye.

CORNEAL ULCERS

There is a hazy white spot on the patient’s cornea; it may be hollowed out, and there may be a yellowish area, or pus in his anterior chamber. His eye is painful, photobic and red with ciliary injection.

If possible, send a pus swab from the ulcer for bacteriological and fungal examination.

Instil atropine drops, topical broad spectrum antibiotic drops (neomycin, bacitracin, or chloramphenicol) and inject subconjunctival chloramphenicol or gentamycin 500 mg once or twice daily for several days (23.1).

CORNEAL LACERATIONS

If a corneal laceration is less than 1 mm, the patient’s anterior chamber is normally deep, and there is no iris in the wound, don’t suture it.

If the normal curve of the patient’s cornea is maintained and the edges of the wound are close together, you can probably leave his laceration unsutured.

If the normal curve of his cornea is not maintained, so that his cornea is angled or tented, suture it. If you don’t, and the laceration is central, he will have a severe refractive error.

\includegraphics[width=\linewidth ]{/home/kumasi/Desktop/primsurg-tex/vol-2/ch-60/fig/60-6.eps}
Figure 60.6: SUTURING THE CORNEA AND SCLERA. A, a laceration of the patient’s sclera. B, a laceration of his cornea and his eyelid. C, try to make the suture cross his cornea in its posterior third. It is only about 1 mm thick, so this will not be easy. If the normal curve of his cornea is maintained (D), there is less need to suture it than when it is deformed or tented (E). The cut edges of the endothelium on the posterior surface of his cornea should be in contact. F, the needle entering at 90\ensuremath{^\circ } to his cornea. G, the needle about to cross the wound. H, entering the other side of the wound. I, pulling out the needle.J, this patient’s conjunctiva retracted to show a wound of his cornea and sclera with prolapse of his iris. K, his prolapsed iris has been excised, and his cornea and sclera have been sutured. L, his cornea has been closed over the wound.M, a knot for tying 9/0 mofilament. N, wind the suture three times round the forceps. O, pulling the suture tight. Partly after Galbraith, with kind permission.

If his anterior chamber is shallow or his iris has prolapsed into his corneal wound, remove the prolapsed iris and suture his cornea, as described below.

If a small amount of corneal stroma has been lost from the edge of the wound, repair it by inserting a tight horizontal mattress suture.

SUTURE If you can refer a patient to an expert within 2 days of his injury, do so.

If you have to suture his cornea yourself, use sutures of 7/0 or 8/0 atraumatic silk, or monofilament. You will find this difficult task easier if you use interrupted sutures. Experts always use continuous ones. One length of atraumatic suture material will be enough for the whole injury.

CAUTION! Don’t suture the cornea with catgut because the wound will take 6 weeks to heal, and by that time the catgut will have dissolved.

Use a small curved cutting needle. Grasp it at its mid point, so that the convexity of the jaws of the needle holder is towards the tip of the needle. This will give you more control over it.

CAUTION! Aim to bring the cut edges of the endothelium on the posterior surface of the cornea together, without actually going through it. The way to do this is to pass the needle across the wound in its posterior third. The whole thickness of the cornea is only about 1 mm, so that this will not be easy. If your sutures are too superficial they will pull out; if they are too deep, they will enter the anterior chamber and damage the endothelium on the back of the cornea. You will need a steady hand, so support your wrist on the patient’s forehead, or on a sandbag underneath the drapes beside his head. Or, support your wrist on your assistant’s fist.

Hold the edge of the wound (not the whole thickness of the cornea) obliquely with fine toothed forceps, so that one blade enters the wound as in G, Fig. 60-6.

While you are holding the edge of the wound undistorted with forceps, insert the needle at almost 90\ensuremath{^\circ } into the cornea 1.5 mm from the edge of the wound. As the needle goes through it, let the needle holder follow its curve. Aim the needle to enter the wound in the posterior one third of the cornea. It should then pass across the wound to the matching opposite edge, and come out at 90\ensuremath{^\circ } to the cornea.

If the wound is vertical, bring the stitch out 0.5 mm from its edge. If it is oblique, bring it out 1 mm from the wound edge.

Pull the suture material through the wound, until only about 1 cm remains. Tie the suture in three throws by winding the monofilament round the needle holder or the suture tying forceps. Use three turns for the first throw, then one, and then another one, (M, and N, 60-6).

CAUTION! Don’t pass sutures through a patient’s iris. If you find that a suture has gone through his iris, remove it.

Use the first throw to bring the tissues together without any tension. Leave a tiny loop between the first and second throws to make sure that no undesirable tension is transmitted to the first throw. Pull the third throw down and hold it down so that it can mould into a knot.

Pull one side of the suture, as it emerges from the cornea so that the knot just enters the needle track. This will make the patient more comfortable while his eye heals. Instil atropine drops.

CAUTION! Don’t try to reconstitute his anterior chamber by injecting air or saline. This is a highly skilled task, and you are likely to do more harm than good.

SCLERAL LACERATIONS

Suture a patient’s sclera in the same way as his cornea, but use 4/0 or 5/0 sutures of atraumatic silk or monofilament. Cover the sutures in his sclera by repairing the conjunctiva over them with fine silk (6 to 8/0), as in L, Fig. 60-6. Leave the scleral sutures in place, but remove those in his conjunctiva.

If vitreous prolapses through a wound in the sclera, excise it. Dip a swab into the wound and lift the vitreous away. If a strand of vitreous is pulled from the wound, cut it off with scissors. The proximal end of the strand will retract into the patient’s eye. Repeat this until you have removed all the vitreous that has escaped from his globe. If some still oozes out or sits on the wound, aspirate it using a wide bore needle. Then suture the sclera as described above.

CAUTION! Don’t allow vitreous to remain trapped at the edges of the wound, because the complication rate increases, and wound healing will be poor.

POSTOPERATIVE CARE FOR CORNEAL AND SCLERAL LACERATIONS

Instil atropine, pad and bandage the patient’s eye.

If the wound is near the edge of the patient’s cornea, remove the sutures at 2 weeks.

If the wound is more central in his cornea, leave the sutures in for 2 months if his eye is comfortable and quiet. To remove them, lie him flat, instil local anaesthetic and insert a speculum. Using good magnification, pull the superficial arm of the suture to the surface with a fine hook, and cut it with the tip of a No.11 scalpel blade. If necessary, make a fine hook by tapping a 6 mm needle on a metal surface so that its tip becomes burred.