Wednesday, January 18, 2006

TECHNIQUE FOR EYE BISECTION




Opening of the eye for internal examination is performed with a broad razor blade beginning posteriorly slightly above the optic nerve and cutting anteriorly in the horizontal (transverse) plane. The fixed adult lens is too hard to cut through without dislocating it and injuring adjacent structures in the anterior segment. Accordingly, the incision anteriorly must continue in the same plane but extend around the lens, leaving it in situ in the inferior calotte when the superior calotte (cap) is removed. For the right-handed person, this best accomplished as follows:

(1) The eye is held with the cornea down (against the table surface) and with the 12 o'clock position to the right; beginning slightly to the right of (i.e. above) the optic nerve, the incision is made with broad heel-to-toe strokes of the razor blade parallel to the 3 and 6 o'clock meridians (using the long posterior ciliary artery and nerves as a guide) to the level of the lens.
(2) Leaving the blade in position, the eye is repositioned with the incisional plane now parallel to the table surface and with the cornea facing to your right; the blade is then regrasped with the thumb and index finger at either end, and is slightly withdrawn to continue the incision around the lens.

(3) The incision is continued in the same plane by rotating the eye around a vertical axis in a counter-clockwise direction, while making oscillating strokes with the blade against the lens surface and maintaining the plane of the incision to pass precisely through the upper margin of the pupil.

(4) When the encircling incision is complete, the eye is repositioned with the 12 o'clock meridian facing up and the cornea facing away from the operator; with thumb forceps in the left hand, the episcleral tissue of the small calotte is grasped near the edge of the posterior incision and the calotte is slowly elevated.

(5) While raising the posterior aspect of the small calotte, the lens is held in place with the razor blade in the right hand by making a shallow bite into its posterior capsule; if the incision has been properly made, only the zonular attachments to the superior aspect of the lens with remain. These zonular attachments will rupture without incident as the small calotte is separated and at this time any uncut vitreous (especially within vitreous base) can be severed with a sweeping stroke of the blade.

The positions of the blade are shown as it cuts arounds the eyes using the step described above.

0 Comments:

Post a Comment

Links to this post:

Create a Link

<< Home