When the surgeon introduces the phaco tip into the anterior chamber of a highly myopic eye, the chamber may deepen dramatically, making lens manipulation difficult. To avoid extensive deepening of the anterior chamber, the surgeon is advised to lower the irrigation bottle and increase the flow rate before entering the eye with the phaco tip. Placing a second instrument between the iris and the anterior capsule prior to turning on infusion may prevent excess deepening. Despite this maneuver, high-myopic eyes are susceptible to lens–iris diaphragm retropulsion syndrome (LIDRS), wherein 360° of iridocapsular contact occurs, causing reverse pupillary block, pupillary dilation, and pain. A defect or laxity in the zonular fibers predisposes myopic eyes to LIDRS. Manual separation of the iris from the anterior capsule rim using a sideport instrument corrects the situation (see Chapter 10).
It is important to calculate IOL power preoperatively for myopic eyes to determine whether a special-order IOL, such as a plano-power or minus-power implant, is required. It is preferable that the patient receive an IOL when possible; the lens implant serves as a barrier to movement of the vitreous base and associated traction on the retina. Because myopic eyes are at increased risk of retinal detachment postoperatively, acrylic lens implants are favored when there is a strong possibility that the patient will later undergo a vitreoretinal surgery. During vitreoretinal surgery involving an open posterior capsule, silicone IOLs develop condensation that compromises visualization into the eye. Silicone lenses have also been observed to migrate through the capsular opening into the vitreous.
To avoid unexpected difficulty with glasses postoperatively, it is helpful to discuss anisometropia with patients who have high myopia and do not wear a contact lens in the other eye.
Excerpted from BCSC 2020-2021 series: Section 11 - Lens and Cataract. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.