Cataract extraction has undergone great evolution in the last few decades.
As recently as the 1970s, the state of the art was cryoextraction through a large wound under retrobulbar or general anesthesia. Pre operatively the vitreous might have been dehydrated with Diamox and compression. If vitreous was lost, it was cleaned up with Westcott scissors and cotton applicators. Aphakic spectacles or a rigid contact lens was necessary for emmetropia. The complication rate was relatively high and consequently patients were more fearful of poor results and less willing to undergo surgery. A hospital stay of a week or more was common.
Now, a cataract can be removed under topical anesthesia through a small incision in an outpatient setting. Implantation of a foldable intraocular lens can allow the patient to be back to normal activities in a day. The preservation of the posterior capsule maintains the natural compartments of the eye and prevents forward movement of the vitreous. The complication rate is much lower and patient expectations are very high. Additionally, it is a refractive procedure as the residual refractive error can be, at least partially, compensated for by the proper selection of the intraocular lens. Astigmatism may also be corrected with a toric intraocular lens (STAAR Surgical), astigmatic keratotomies or laser corneal ablation.
As cataract surgery has evolved, so has the instrumentation necessary to perform this highly successful procedure. The cryoprobe or erysiphake is replaced by the phaco machine and manual anterior vitrectomy is now done with a vitreous cutter. The cataract surgeon must now understand phacodynamics and fluidics as he operates in a closed system similar to the posterior segment surgeons.
When an anterior vitrectomy is performed as part of cataract removal, the surgeon will probably be handed an anterior vitrectomy cutter, including an irrigating sleeve. The instrument will be introduced through the phaco incision and passed through the pupil to the central, anterior vitreous. The irrigating solution will flow into the eye from the sleeve surrounding the vitreous cutter. The cataract surgeon should remember that the bottle height and aspiration setting of the phaco machine must be changed.
In passing the probe through the pupil, it will be difficult to remove all the vitreous behind the iris which may be adherent to the lens, zonula or posterior iris surface. The likelihood of inadvertently removing iris tissue is increased, especially if the fluidics are not properly handled or if the eye is not closed. There is a significant risk of completing the anterior vitrectomy and implanting the intraocular lens only to find the next day that vitreous is adherent to the intraocular lens or incarcerated in the wound. A peaked pupil may be present as well as unwanted visual phenomena related to haptic or optic edge glare. This raises the possibility of further complications such as CME or retinal tears.
An alternative posterior approach to managing vitreous loss is recommended here for the anterior segment surgeon to consider. It is recognized that the fluid infused through the irrigating sleeve of an anterior vitrectomy probe which is passed through the pupil, will hydrate the vitreous and cause it to expand forward. This is particularly true if the bottle height is not lowered from that used during cataract removal. It should be now set to about 30 cm.
At the time of vitreous loss, the phaco probe should remain in the eye and the side port instrument be removed. The viscoelastic cannula may be introduced and the bag filled to prevent further vitreous prolapse. Both instruments may then be removed. Too much viscoelastic can weight down the posterior capsule and cause extension of the tear. Too little will not tamponade the vitreous. At this stage, it may be possible to create a posterior capsulorrhexis which may permit the placement of an IOL in the bag after vitreous cleanup.