2020–2021 BCSC Basic and Clinical Science Course™
11 Lens and Cataract
Chapter 12: Preparing for Cataract Surgery in Special Situations
Conditions Associated With Extremes in Axial Length
High Hyperopia and Nanophthalmos
An eye with cataract and high hyperopia often has a shallow AC and is prone to uveal prolapse, iris damage, and excessive corneal endothelial trauma during cataract surgery. Deepening of the AC and protection of intraocular tissue can be achieved with a high-viscosity OVD, a low aspiration rate, and elevation of the irrigation bottle prior to insertion of the phaco tip. Mannitol may be administered preoperatively to dehydrate the vitreous volume in a patient with no systemic contraindications. Iris prolapse is avoided by entering through an anterior corneal incision and by taking care not to overfill the eye with OVDs. If all these measures fail to provide sufficient AC volume for cataract removal, a small amount of liquid vitreous can be withdrawn using a 25-gauge needle or a vitrectomy handpiece through a pars plana puncture.
Nanophthalmos is a rare condition in which the eye is extremely short and the ratio of lens volume to eye volume is larger than normal. Diagnostic criteria vary, but these eyes generally have shallow anterior chambers, narrow angles, and thickened sclerae, with little room for the surgeon to maneuver. Axial length is shortened by at least 2 standard deviations below age-matched controls—usually to 20 mm or less. Small-incision bimanual surgery may be considered for these eyes. Because nanophthalmic eyes are at high risk of uveal effusion, precautions include the following measures:
Maintaining positive pressure in the AC and limiting the length of the procedure help prevent intraoperative uveal effusion.
Scleral windows can be considered as a prophylactic measure.
Suturing the wound helps prevent hypotony and consequent uveal effusion postoperatively.
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.