When examining the lens, the clinician notes its appearance both before and after dilation of the pupil. The impact of “oil droplet” nuclear cataracts and small PSCs is most closely correlated with visual symptoms before pupil dilation. After dilation, nuclear density can be evaluated, pseudoexfoliation syndrome can be detected, and opacities and distortion of the retinoscopic reflex can be visualized more easily.
To assess the lenticular contribution to the visual deficit, the clarity of the media in the visual axis is evaluated with the slit lamp. Dense, brunescent nuclear sclerotic cataracts may permit remarkably good vision, especially at near distances, whereas vacuolar cataracts, which may be detected by red reflex examination, can cause surprisingly severe vision loss. When dense cortical opacification is present, the intraoperative use of capsular dye to enhance visualization of the capsulorrhexis may be considered. The presence of a congenital posterior polar opacity is associated with a significant risk of capsule rupture and should be identified before surgery.
The position of the lens and the integrity of the zonular fibers are also evaluated. Lens coloboma, lens decentration, phacodonesis, or excessive distance between the lens and the pupillary margin indicates zonular disruption due to conditions such as lens subluxation as a result of previous trauma, metabolic disorders, or hypermature cataract. An indentation or flattening of the lens periphery may indicate focal loss of zonular support. For patients with these types of zonular disruption, the surgeon can alter surgical technique, including the use of capsular tension rings or other capsular or iris support devices intra-operatively (see Chapter 12).
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.