Lens extraction for cataracts

Lens extraction is the mainstay of modern cataract surgery. It can be intracapsular or extracapsular extraction (1).

Modern day preference is for an extracapsular method since it allows for a posterior chamber intraocular lens to be inserted and has a lower incidence of post - operative complications such as retinal detachment and cystoid macular oedema. The main complication is the development of a posterior capsule opacification.

In an extracapsular extraction, the anterior capsule is cut and removed, the hard nucleus extracted, and the lens cortex removed (this is either via a large incision at the limbus, or after phacoemulsification (emulsifying the lens via ultrasound) via a smaller incision). The posterior capsule is left behind to support the implanted artificial lens. This procedure is generally undertaken under local anaesthesia.

In comparison of standard extracapsular surgery and extracapsular extraction with phacoemulsification (1):

• visual recovery is slower after standard extracapsular surgery than following phacoemulsification
• extracapsular surgery with phacoemulsification results in less induced astigmatism
• the numbers of patients who achieve a corrected visual acuity of better than 6/12 after 3 months is similar for the two procedures

In an intracapsular extraction, alpha chymotrypsin is injected into the posterior chamber to digest the suspensory ligament and then the lens is removed in it's entirety with the aid of a forceps or a cryoprobe.

• although commonly used in the developing world, it is no longer used in the developed world (except for rare occasions) (1)

Previously patients were left "aphakic" (from the Greek, meaning 'with no lens') after cataract surgery and would have to wear thick spectacle lenses postoperatively, as they still do in the third world.

Reference:

• (1) Allen D, Vasavada A. Cataract and surgery for cataract. BMJ. 2006;333(7559):128-32