An Optical Section-Assisted In Vivo Rabbit Model for Capsular Bend and Posterior Capsule Opacification Investigation

Abstract

Purpose: To establish an optical section-assisted in vivo rabbit model for capsular bend and posterior capsule opacification (PCO) investigation.

Methods: A total of 10 rabbits underwent phacoemulsification surgery and intraocular lens (IOL) implantation. On the basis of the relationship between the anterior capsule and IOL, the rabbits were divided into complete overlap and incomplete overlap groups, in which six and four rabbits were included, respectively. The capsular bend optical sections were assessed using ultra-long scan depth optical coherence tomography (UL-OCT), and posterior capsule opacification was evaluated with slit lamp on postoperative day 3, 7, 14, and 28. In addition, histopathological section was used to verify the accuracy of capsular bend type captured by OCT in three rabbits.

Results: Based on the special animal model, six capsular bend types were observed, namely, anterior (A), middle (M), posterior (P), detachment (D), funnel (Fun) and furcate adhesion (Fur). On day 3, capsular bend began to form. On 14 days, the capsular bends were comprised of A, M and D types, which were almost maintained until day 28. Histopathological section findings were consistent with optical sectioning results. In the incomplete and complete groups, the earliest PCO within the optical zone were on day 7 and 28, respectively. The incomplete group exhibited higher incidence and faster PCO on day 7 (p = 0.038) and 14 (p = 0.002).

Conclusions: This animal model not only mimics capsular bend evolution and PCO processes but also produces OCT optical section images equivalent to and more repeatable than histopathology, thereby providing a promising method for the further investigations of PCO.

Fig 1. Schematic of relationship between anterior capsule (white arrow) and IOL optic edge (white triangle) in the scan position (green lines).

N stand for nasal side, while T stand for temporal side. (A) The temporal side illustrates an undesirable overlap (the capsule overlap less on the IOL optic edge), and the right side illustrates a complete overlap (the capsule complete overlap the IOL in the scan position). (B) The temporal side capsule does not overlap the IOL optic.

Fig 2. Flow chart of the experiment.

Levofloxacin and tobramycin dexamethasone eye drop or oculentum were used for anti-infection and anti-inflammatory for at least 7 days after surgery.

Fig 3. UL-OCT images (A-C & G-I) and corresponding schematic (D-F & J-L) of capsular bend types.

Red arrows demonstrate the characteristics of different capsular bend types. In schematic images, black and gray lines represent anterior and posterior capsules, respectively. (A and D) Anterior adhesion type: the posterior and anterior capsule form a stable adhesion at the anterior surface of the IOL optic edge. (B and E) Middle adhesion type: the posterior and anterior capsule wrapped around the IOL and met at the middle of the IOL edge. (C and F) Posterior adhesion type: the anterior and posterior capsule form a stable adhesion at the posterior surface of the IOL. (G and J) Detachment type: the anterior capsule detached from the IOL optic edge. (H and K) Funnel adhesion type: the posterior and anterior capsules adhered to each other, but a space between the capsule and IOL remained and showed the appearance of a funnel. (I and L) Furcate adhesion capsule type: the inner sides of the posterior and anterior capsules adhered, whereas the peripheral side was separated.

Fig 4. Histopathological section observations on day 11 postoperatively and OCT images on day 7 postoperatively at the scan position.

(A) Unformed capsular bend configuration at temporal side (blue triangle). (B) Anterior adhesion type at nasal side (white arrow). (C) OCT image of the same rabbit showing the same capsular bend configuration at the same place. The white asterisk indicates the iris.

Fig 5. Different types of capsular bends at various times after surgery.

A = anterior adhesion type, M = middle adhesion type, P = posterior adhesion type, Fun = funnel adhesion type, Fur = furcate adhesion type, and D = detachment type.

Fig 6. Slit lamp image of a posterior capsule and an OCT image of capsular bend of an incompletely overlapped eye 7 days (A and C) and 28 days postoperatively (B and D).

(A and C) On day 7 postoperatively, the capsule was smooth, no opacity was present, and both sides formed anterior adhesion types. (B and D) On day 28 postoperatively, the temporal side (black and white asterisk) exhibited an undesirable overlap, abundant proliferation, and migration of LECs into the posterior capsule. The detachment and funnel adhesion types emerged at the temporal and nasal sides, respectively. Increased thickness of the posterior capsule (white arrow) was apparent in both slit lamp and OCT images.

Fig 7. Observation of capsular bend via slit lamp (A-D) and UL-OCT optical sections (E-H) with schematic images embedded in the center of the images.

Red lines stand for anterior capsule and yellow squares for IOLs. (A and E) On day 3 postoperatively, an incomplete overlap, anterior capsule not overlapping the IOL at 9 o’clock to 11 o’clock temporally existed, and no opacity were found in the posterior capsule. Neither nasal nor temporal side formed a capsular bend. (B and F) On day 7 postoperatively, the temporal side of the anterior capsule came close to the IOL, and the capsule partially wrapped around the optic edge because of posterior capsular contraction. LECs migrated into the center of the temporal posterior capsule. Both sides formed anterior adhesion types. (C and G) On day 14 postoperatively, the LECs elongated and integrated into a fibrous-like membrane. The anterior capsule detached from the temporal IOL optic edge (white triangle) and transformed into the detachment type, whereas the nasal side remained the anterior adhesion type. (D and H) On day 28, the entire posterior capsule was covered by LECs, and exacerbation of the posterior capsular contraction and increased thickness of the posterior capsule (white arrow) were present. The temporal and nasal sides remained the anterior detachment and anterior adhesion types, respectively.