Long-term observation of the in vivo safety of a new design of phakic refractive lens

Abstract

Background: To evaluate the biosafety, reduction in anterior capsule opacification, and fluctuation in intraocular pressure (IOP) of a new phakic refractive lens (PRL) with a sinusoidal drainage groove design.

Methods: This self-controlled experiment was performed on eight eyes of four rabbits. Each rabbit was implanted with a sinusoidal PRL (PRL-S5) in the right eye and a conventional posterior chamber PRL (PC-PRL) in the left eye. Slit-lamp examinations, optical coherence tomography, and IOP evaluation were performed before surgery and at 1 day, 1 week, 3 months, 6 months, and 1 year postoperatively in each eye. Gross examination, histopathology, and electron microscopy of the capsule and PRL were performed 1 year postoperatively.

Results: On slit-lamp examination, the inflammatory reactions recovered one week after surgery. The PC-PRL group developed anterior subcapsular cataracts at 3 months postoperatively and diffuse and dense opacification of the cortex at 1 year. PRL-S5 showed mild local opacification in the optical zone 6 months postoperatively, which did not progress significantly. At 1 year, PC-PRLs had greater opacification (27.37-72.17%) than PRL S5 (6.63-66.96%). Three months after surgery, one eye in the PC-PRL group had scleral staphyloma, one eye had corneal edema, and one eye experienced nasal hepatic prolapse into the anterior chamber. One eye in the PRL-S5 group had papillary membranes but recovered 6 months postoperatively. Histopathological examination revealed liquefaction and necrosis of the opacified area in the center of the subcapsular membrane in both groups. Numerous granular bodies and fibrous precipitates were observed in epithelial cells in the opaque area. Electron microscopy showed that epithelial cells proliferated on the surface of all anterior capsule membranes, with no significant differences between the two groups. The capsular PC-PRL group showed anterior cortical proliferation and fibrosis. An IOP elevation was noted on the first postoperative day (18.8 to 37.9 mmHg). However, both the PC-PRL and PRL-S5 groups exhibited relatively stable IOP levels 1 week, 3 months, 6 months, and 1 year postoperatively.

Conclusions: The new PRL exhibited robust long-term biocompatibility. The sinusoidal groove design facilitated the maintenance of IOP stability without necessitating iridectomy and effectively mitigated the onset and progression of cataracts.

Keywords: Cataract; Complications; Intraocular pressure; Phakic Intraocular Lens; Phakic Refractive Lens; Refractive surgery.

Fig. 1

Slit-lamp and AS-OCT examination at 1 week, 3 months, 6 months, and 12 months postoperatively. Representative photographs of the ocular surface (columns 1 and 5), anterior chambers (columns 2 and 6), and posterior chambers (columns 3 and 7) observed using a slit lamp, and the crystalline lens observed using AS-OCT (columns 4 and 8) during the experimental period are shown. Photographs were captured from both eyes of the same rabbit

Fig. 2

Gross examination and histopathology findings at 1 year postoperatively. A and B show diffuse anterior subcapsular cataracts in the PC-PRL and PRL-S5 groups; however, the PC-PRL group exhibited more severe posterior adhesions between the proliferative mass in front of the crystalline lens. C-F show hematoxylin and eosin-stained histopathological results of the specimens in A and B. Liquefaction and necrosis of the opacified area in the center of the subcapsular membrane in both groups

Fig. 3

Inflammation and necrosis in the opacity area in PRL S5 and PC PRL. A was from PC-PRL. B-C were from PRL S5. Numerous granular bodies and fibrous precipitates were observed in the epithelial cells in both groups

Fig. 4

Scanning electron microscopy (SEM) observation of PRL-S5 and PC-PRL group at 1 year postoperatively. Panels A and B show gross photographs of the PRL-S5 and PC-PRL groups, respectively. Panels C, E, and G show SEM results for the PRL S5 group (from the same specimen as in A). Panels D, F, and H show the SEM images of the PC-PRL group (from the same specimen as in B), with panels F and H highlighting typical anterior cortical proliferation and fibrosis, respectively

Fig. 5

Intraocular pressure fluctuation of PRL-S5 and PC-PRL at different follow-up times. Blue line represents the PRL S5 group. The red line indicates the PC-PRL group. The symbols and error bars represent the mean and standard deviation of IOP at each time point