Techniques in cataract surgery

Cataract surgery has changed dramatically during the past twenty years. The use of operation microscopes and intra-ocular lenses, and progress in instrumental micromechanics, have resulted in new surgical techniques which minimise the trauma and maximise the visual results.
Until the 1970s the cataractous lens was completely removed by means of a cryode, a probe specially equipped to freeze surrounding tissues (intracapsular cataract extraction), through a large incision of up to 13 mms without insertion of an implant lens. Several sutures were needed. After surgery the patient’s vision had to be corrected by the use either of thick “aphakic” glasses or permanent contact lenses. The glasses were heavy to wear, were impractical because of their magnifying effect and they restricted the patient’s visual field. Moreover, they could not be prescribed if only one eye had been operated on. Contact lenses offered a great improvement but fitting them was difficult and they carried the risk of both inflammation and infection.
Since the early 1970s implant lenses, designed to replace the natural lens, have been inserted in the anterior chamber of the eye between the iris and the cornea. In some cases they have caused oedema of the cornea or chronic glaucoma (excessive eye pressure).

In extracapsular cataract extraction only the core of the cataractous lens is removed: this is done manually through an incision in the lens capsula, the outer part of the lens, leaving in place an “envelope” in which an implant lens can be inserted. The implant lens is then placed in the posterior chamber behind the iris where the natural lens was positioned.

The outer incision in the eye is only 8 to 10 mms long but still needs sutures. For this technique an operation microscope is required, complications are few if the surgery is properly performed, and thus it has become the preferred technique since the early 1980s.
In one third of patients the lens capsula may become opaque months or years after surgery: this is called secondary cataract or posterior capsular opacification. Treatment consists of making an opening in the cloudy lens capsula (capsulotomy) by means of a YAG-laser, which will achieve recovery of vision from the following day.

Phako-emulsification. No-stitch surgery and foldable lenses.

In 1962 Charles Kelman (USA) developed ultrasonic phako-emulsification which enables the core of the cataractous lens to be fragmented and extracted through a 3 mm incision. It took thirty years and several technical improvements before his invention was applied worldwide. Implants with a smaller optical zone were used but still needed enlargement of the incision up to 5 mm and one or two sutures to close the wound.
The advent of foldable implant lenses that can be inserted through a small 3 mm incision has brought us to “no-stitch cataract surgery”. The advantages of small incisions without sutures are that they do not produce corneal deformation and they thus avoid astigmatism, visual recovery is faster and the refractive result remains stable.

Topical anaesthesia or anaesthesia by drops

The next revolution came in the mid-90s. Up to that time all cataract surgery was performed under local or - less frequently – general anaesthesia. Local anaesthesia was administered by “retrobulbar” injection, i.e. a painful or disagreeable injection behind the eye, which was potentially dangerous because it could cause orbital hematoma (bleeding behind the eye), perforation of the eyeball, damage to the optic nerve or post-operative ptosis (lowering of the eyelid).

Anaesthetic drops prevent all pain, even though the patient is still able to move his/her eye and see with it. An experienced surgeon can perform the cataract operation using this type of anaesthesia, so long as he instructs the patient to look at the bright light of the microscope and guides him/her through the procedure.

However, there are circumstances in which drops cannot be used and an injection has to be administered. This applies to very dense or hard cataracts, to eyes presenting very small pupils or to cases where cataract surgery is combined with other procedures such as glaucoma surgery or corneal graft.

More about Phako-emulsification

The operation
Preparing for an operation

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