Histopathological analysis of residual lens cells in capsular opacities after cataract surgery using objective software

Abstract

Purpose: Remnant lens epithelial cells (LECs) within the capsular bag (CB) undergo epithelial-to-mesenchymal transition (EMT) and acquire a myofibroblast phenotype, depositing extracellular matrix (ECM) components, leading to posterior capsular opacification (PCO). This study histopathologically analyzes the LEC-to-myofibroblast transition and de novo ECM component deposition (i.e., smooth muscle actin (SMA) and fibronectin (FN) expression) and determines the intraocular lens (IOL) and patient factors associated with these changes.

Methods: In total, 190 CBs with IOLs were removed from donor eyes. Digital images were obtained, and PCO was graded using published software (ADOS, Medical Parachute). Automated immunohistochemistry was performed using anti-SMA to detect EMT and anti-FN to document ECM remodeling. Slides were digitized and analyzed using the Positive Pixel Count v9 algorithm. Linear regression and Poisson regression were performed (P < 0.05).

Results: SMA positive expression decreased as the time of IOL implantation increased (P < 0.0001). Positivity of SMA and FN demonstrated a positive correlation (P = 0.0002). Controlling for confounding factors in Poisson regression, hydrophobic and hydrophilic materials showed higher FN and SMA expression when compared to silicone material lenses (FN; P = 0.018; P < 0.0001, SMA; P = 0.001; P = 0.003, respectively). The square optic design had 29% higher SMA positivity compared to the opti-edge design (P = 0.042). One-piece haptic lenses had higher SMA expression compared to three-piece haptic (P = 0.042). A higher risk of expression of SMA and FN was seen in patients with a history of smoking, hypertension, and glaucoma (P < 0.05).

Conclusion: This study demonstrated that SMA and FN expression is different according to IOL design and patient factors, thus indicating that LEC changes depend on lens biocompatibility. Therefore, by analyzing the histopathological composition of PCO by using LECs, further insight into the characteristics of IOLs that are important for biocompatibility can be ascertained.

Keywords: Capsular opacification; immunohistochemistry; intraocular lens; objective software; post-mortem eyes.

Figure 1

Histological sections of capsular bag tissue. a) Hematoxylin and eosin stain demonstrated the anterior (bottom basement member) and posterior capsule (top basement membrane). Soemmering’s Ring opacities are located in the bulk, indicated with the star. Placement of the optic edge of the intraocular lens is indicated with the arrow. b) Magnification of the intraocular lens placement between the anterior and posterior capsule. c) Immunohistochemistry of a-smooth alpha-actin on the capsular bag tissue. d) Immunohistochemistry of fibronectin on the capsular bag tissue

Figure 2

Digital slide of the capsular bag with quantification algorithm. a) Capsular bag stain smooth alpha-actin (SMA). b) Positive Pixel Count v9 algorithm quantification on the Aperio ImageScope. Blue indicates negative staining, orange indicates positivity, and red indicates strong positive staining. c) Magnification of the edge of the intraocular lens placement. d) Positive Pixel Count data output for SMA expression