Light and scanning electron microscopy of rabbit lens capsules with intraocular lenses

Analysis of the capsular bend in posterior capsular opacification using anterior segment optical coherence tomography

PURPOSE

To investigate the link between the capsular bend and the morphological types and characteristics of posterior capsular opacification (PCO) using anterior segment optical coherence tomography.

METHODS

Thirty eyes with PCO were examined, and three types of PCO were identified: pearl, fibrosis, and mixed. We assessed anterior capsular overlap, intraocular lens-capsule adhesion, and capsular bending. In addition to measuring the intraocular lens-posterior capsule distance and capsule bending angle (CBA), the PCO parameters (area, density, and score at 6-, 5-, and 3-mm intraocular lens optic regions) were recorded. The associations between capsular bend and PCO type and characteristics were investigated. A control group of 12 eyes without PCO was used to compare the study variables.

RESULTS

With p values greater than 0.001, there was a statistically significant difference in the mean PCO area and score at the 6-, 5-, and 3-mm optic zones in different PCO types, with the pearl type having the highest value, followed by the mixed type, and finally the fibrosis type. The PCO group had a significantly higher mean CBA than the control group (P = 0.001). CBA was positively related to intraocular lens-posterior capsule distance, PCO area, and PCO score at the 6-, 5-, and 3-mm zones (P = 0.001). The receiver operating characteristic curve's cut-off point for CBA was 96.85° when comparing PCO cases to controls. Partial overlap and incomplete adhesion were statistically more common in the PCO eyes than in the control (P = 0.001, 0.003, respectively).

CONCLUSION

PCO types and CBA have a strong relationship with PCO score and intraocular lens-posterior capsule space. In PCO's eyes, CBA has a cut-off value of 96.85°.

Resident immune cells of the avascular lens: Mediators of the injury and fibrotic response of the lens

Tissues typically harbor subpopulations of resident immune cells that function as rapid responders to injury and whose activation leads to induction of an adaptive immune response, playing important roles in repair and protection. Since the lens is an avascular tissue, it was presumed that it was absent of resident immune cells. Our studies now show that resident immune cells are a shared feature of the human, mouse, and chicken lens epithelium. These resident immune cells function as immediate responders to injury and rapidly populate the wound edge following mock cataract surgery to function as leader cells. Many of these resident immune cells also express MHCII providing them with antigen presenting ability to engage an adaptive immune response. We provide evidence that during development immune cells migrate on the ciliary zonules and localize among the equatorial epithelial cells of the lens adjacent to where the ciliary zonules associate with the lens capsule. These findings suggest that the vasculature‐rich ciliary body is a source of lens resident immune cells. We identified a major role for these cells as rapid responders to wounding, quickly populating each wound were they can function as leaders of lens tissue repair. Our findings also show that lens resident immune cells are progenitors of myofibroblasts, which characteristically appear in response to lens cataract surgery injury, and therefore, are likely agents of lens pathologies to impair vision like fibrosis.

Time Course of Lens Epithelial Cell Behavior in Rabbit Eyes following Lens Extraction and Implantation of Intraocular Lens

Background

After cataract surgery, some lens epithelial cells (LECs) transdifferentiate into myofibroblast-like cells, which causes fibric posterior capsule opacification (PCO). Residual LECs differentiate into lens fiber cells, forming Elschnig pearls with PCO. This study was carried out to identify the time course of both types of LEC behavior in rabbit eyes following lens extraction and implantation of an intraocular lens (IOL).

Methods

Phacoemulsification and implantation of posterior chamber IOLs were performed in rabbit eyes. Following enucleation, immunohistochemical methods were used to detect α-smooth muscle actin (α-SMA), a marker for myofibroblast-like cells, in the pseudophakic rabbit eyes. A mouse monoclonal antibody against α-SMA was used.

Results

Soon after the operation, the LECs migrated and covered the lens capsule. Thereafter, the LECs around the anterior capsular margin were always positive for α-SMA. However, the distributions of these cells were not consistent. In some specimens, α-SMA-positive LECs were present around the IOL optic early after surgery, but most of them had disappeared several weeks after the surgery. The residual cells induced fibrotic PCO. In the other specimens, most LECs around the IOL optic except the anterior capsular margin were negative for α-SMA. In the peripheral region covered by the peripheral anterior and posterior capsules, LECs on the posterior capsule always differentiated into lens fiber cells and formed a Soemmering ring. Thereafter, migration of lens fiber cells from the Soemmering ring and differentiation of LECs in situ on the central posterior capsule consisted of Elschnig pearls type of PCO.

Conclusions

Although postoperative LEC behavior is not consistent, residual α-SMA-positive LECs induced fibrotic PCO. The lens fiber cells that migrated from the peripheral capsular bag or that were differentiated in situ covered the central posterior capsule, forming Elschnig pearls with PCO.

[Posterior capsule opacification after phacoemulsification in patients with rheumatoid arthritis]

PURPOSE

To assess the posterior capsule opacification (PCO) rate after phacoemulsification with polyacrylic intraocular lens (IOL) implantation in patients with rheumatoid arthritis (RA) compared with the controls, and to assess whether preoperative activity of RA is associated with a higher incidence of PCO.

METHODS

24 eyes of 20 RA patients operated in a period of 4 years were included in our study. A control group of 20 eyes from 20 health subjects were also included in our study. All procedures were performed by a single surgeon with the same surgical technique and postoperative medication.

RESULTS

One year postoperatively in two eyes (8.3%) of RA-patients lens epithelial cells (LEC) migration of grade 1 was observed, in controls also in two eyes (10%). No correlation was observed between age, duration of RA or preoperative activity of RA and the PCO rate.

CONCLUSION

Following acrylic IOL implantation, the PCO rate one year after surgery was 8.3% in RA patients and 10% in controls. RA patients present no higher risk for PCO development than controls.

Effect of anterior capsule polishing on fibrotic capsule opacification: three-year results

PURPOSE

To evaluate the long-term effect of anterior capsule polishing on anterior capsule opacification (ACO) and peripheral fibrotic posterior capsule opacification (PCO).

SETTING

Department of Ophthalmology, Medical University of Vienna, Vienna, Austria.

METHODS

This randomized double-blind study comprised 104 eyes of 52 patients with bilateral age-related cataract. All patients received round-edged intraocular lenses (IOLs); 26 received an SI-40 IOL (Advanced Medical Optics Inc.) in both eyes, and 26 received a Silens6 IOL (Domilens) in both eyes. Both IOLs consist of different silicone material and have different haptic angulation. The SI-40 IOL has 13.0 mm open-loop poly(methyl methacrylate) (PMMA) haptics angulated by 10 degrees. The Silens6 IOL has 12.5 mm open-loop PMMA haptics with no angulation. In 1 eye, the anterior capsule was extensively polished. The anterior capsule was left unpolished in the contralateral eye, which acted as a control. Digital slitlamp photographs of the ACO and fibrotic PCO were taken with a standardized technique for 3 years postoperatively. The intensity of ACO was measured objectively (score 0% to 100%) using Adobe Photoshop software. Fibrotic PCO was graded subjectively (score 0 to 4).

RESULTS

The mean ACO was 17% in the polished eyes and 26% in the control eyes (P = .0001). The mean fibrotic PCO score was 0.5 and 1.0, respectively (P = .0007). The mean ACO was 15% in the polished SI-40 eyes and 26% in the control SI-40 eyes (P = .01). It was 19% in the polished Silens6 eyes and 26% in the control Silens6 eyes (P = .003). The mean fibrotic PCO score was 0.4 in the polished SI-40 eyes and 1.1 in the control SI-40 eyes (P = .0006). It was 0.6 in the polished Silens6 eyes and 0.9 in the control Silens6 eyes (P = .08).

CONCLUSIONS

Three years after surgery, eyes in which the anterior capsule was extensively polished had less ACO and fibrotic PCO with both round-edged silicone IOLs. In eyes with Silens6 IOLs, however, the reduction in fibrotic PCO was not significant.

Expression of cyclooxygenase-2 in corneal cells after photorefractive keratectomy and laser in situ keratomileusis in rabbits

PURPOSE

To compare the expression pattern of cyclooxygenase-2 (COX-2) in rabbit corneal cells after photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) with the same refractive correction.

SETTING

Department of Ophthalmology, Wakayama Medical University, Wakayama, Japan.

METHODS

Thirty adult albino rabbits were used in the study. Photorefractive keratectomy or LASIK was performed in 1 eye of each animal for the same refractive correction. Each animal was killed after healing intervals up to 6 months. Paraffin sections of the cornea were processed for immunohistochemistry for COX-2 and NFkappaB (p65).

RESULTS

After PRK, the central and peripheral corneal epithelia up-regulated COX-2 at 3 days; the central epithelium was positive at 4 weeks. Central and peripheral epithelia returned to negative 3 months later. After LASIK, the central epithelium on the corneal flap up-regulated COX-2 at 1 and 2 weeks; it returned to negative at 4 weeks. The peripheral epithelium was labeled with the antibody. Keratocytes around the stromal incision between the flap and the stromal bed up-regulated COX-2 and returned to negative at 3 months. COX-1 was not detected immunohistochemically in corneal tissue during the healing intervals after both procedures. Nuclear factor kappaB was detected in the cytoplasm and nuclei of migrating corneal epithelial cells 1 day after PRK, was positive in the cytoplasm at 3 days and negative in cytoplasm and nuclei at week and later.

CONCLUSIONS

Migrating injured epithelium expressed COX-2 until week 4 during post-PRK healing. Central uninjured epithelium as well as stromal keratocytes expressed COX-2 from 3 days to 2 weeks after LASIK. Uninjured peripheral epithelium also expressed COX-2 at 4 weeks. Activation of stromal keratocytes may induce expression of COX-2 in overlying uninjured epithelium via the inflammatory cytokine(s)/NFkappaB pathway.

Effect of intraocular lens optic edge design and material on fibrotic capsule opacification and capsulorhexis contraction

PURPOSE

To examine the influence of intraocular lens (IOL) optic edge design and optic material on fibrosis of the anterior and peripheral posterior capsules and on capsulorhexis contraction.

SETTING

Department of Ophthalmology, Medical University of Vienna, Vienna, Austria.

METHODS

This randomized controlled patient- and examiner-masked study comprised 210 eyes of 105 patients with bilateral age-related cataract. In Group 1 (n = 53), the Sensar OptiEdge AR40e hydrophobic acrylic IOL with a sharp posterior optic edge was compared with the AR40 acrylic IOL with a round edge. In Group 2 (n = 52), the ClariFlex OptiEdge silicone IOL with a sharp posterior optic edge was compared with the PhacoFlex SI-40 silicone IOL with a round edge All IOLs were manufactured by Advanced Medical Optics, Inc. Standardized digital slitlamp images of anterior capsule opacification (ACO) and fibrotic posterior capsule opacification (PCO) were taken 1 year postoperatively, and digital retroillumination images were taken at 1 week and 1 year. The intensity of fibrotic PCO was graded subjectively (score 0 to 4), ACO was graded objectively (score 0% to 100%), and the capsulorhexis area (mm(2)) was determined objectively.

RESULTS

One year after surgery, the mean ACO score was 32% in eyes with the sharp-edged acrylic IOL and 29% in eyes with the round-edged acrylic IOL (P<.05). In the silicone group, the mean was 31% and 26%, respectively (P<.05). The mean fibrotic PCO score was lower in eyes with a sharp-edged acrylic IOL than in eyes with a round-edged acrylic IOL (0.26 and 0.93, respectively; P<.05) and in eyes with a sharp-edged silicone IOL than in eyes with a round-edged silicone IOL (0.24 and 0.82, respectively; P<.001). At 1 year, the mean capsulorhexis area was statistically significantly smaller in eyes with a sharp-edged silicone IOL than in eyes with a round-edged silicone IOL (P<.05).

CONCLUSIONS

Acrylic and silicone IOLs with the sharp OptiEdge design led to significantly less fibrotic PCO but more ACO than round-edged acrylic and silicone IOLs. The sharp-edged silicone IOL caused significantly more capsulorhexis contraction than the round-edged silicone IOL and both acrylic IOLs.

Deposition of silicone oil droplets in the residual anterior lens capsule after vitrectomy and lensectomy in rabbits

AIM

To examine the histology of preserved anterior lens capsule in vitrectomised and lensectomised rabbit eyes with and without silicone oil tamponade.

METHODS

Forty adult Japanese albino rabbits received two port vitrectomy and lensectomy with or without silicone oil tamponade in one eye under both general and topical anaesthesia. Anterior lens capsule was preserved during operation. After healing intervals residual anterior capsule was histologically observed under light or electron microscopy.

RESULTS

Immediately after operation, cuboidal lens epithelial cells were observed on the posterior surface of the preserved anterior capsule. During healing intervals in eyes with or without silicone oil tamponade, regenerated lens structure of Sommerring's ring and fibrous tissue formed in the peripheral and central areas of the residual capsule, respectively. Ultrastructural observation revealed the presence of many vacuoles amid matrix accumulation on the posterior capsular surface, suggesting the deposition of emulsified silicone oil droplets.

CONCLUSION

Lens epithelial cells produce regenerated lenticular structure and fibrous tissue on the residual capsule following vitrectomy and lensectomy in rabbits. Silicone oil droplets formed by its emulsification deposit in extracellular matrix accumulated on the posterior surface of the anterior capsule. Emulsified silicone may potentially enhance opacification of residual anterior capsule following pars plana vitrectomy by silicone oil deposition and subsequent activation of lens epithelial cells.

Analysis of cytoskeletal proteins in posterior capsule opacification after implantation of acrylic and hydrogel intraocular lenses

PURPOSE

To analyze selected lens cytoskeletal proteins in posterior capsule opacification (PCO) 2 weeks after intraocular lens (IOL) implantation in rabbits.

SETTING

Department of Ophthalmology, Dokkyo University School of Medicine, Tochigi, Japan.

METHOD

Eight 10-week-old albino rabbits were prepared and anesthetized for phacoemulsification and aspiration of the crystalline lens and implantation of an acrylic or a hydrogel IOL. Two weeks postoperatively, the rabbits were killed and the IOLs removed for immunohistochemistry. Deparaffinized tissue sections were processed with antibodies against alpha-smooth muscle actin (alpha-SMA) and beta-crystallin to observe the types of PCO with the 2 IOL types. The proteins in the PCO tissue and the normal lens were homogenized, centrifuged, and analyzed using SDS-polyacrylamide gel electrophoresis (SDS-PAGE) densitometric analysis and Western immunoblotting for actin and vimentin.

RESULTS

Immunohistochemistry demonstrated a fibroblastic cell type expressing alpha-SMA and partial regeneration of epithelial cells, resulting in a lenticular structure that stained irregularly for beta-crystallin. The immunoreactivity of fibroblast-like cells to beta-crystallin appeared weaker than that of the regenerated lenticular structure. SDS-PAGE showed variability in the content of cytoskeletal proteins in the insoluble fractions of the PCO. Degradation of the cytoskeletal components was greater with the acrylic IOL than with the hydrogel IOL.

CONCLUSION

Cytoskeletal proteins expressed during the formation of PCO and IOL implantation may have potential as therapeutic target proteins to improve the biocompatibility of IOLs.

Wound healing in rabbit corneas after photorefractive keratectomy and laser in situ keratomileusis

PURPOSE

To compare the wound-healing process in the rabbit cornea after photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) with the same refractive correction.

SETTING

Department of Ophthalmology, Wakayama Medical University, Wakayama, Japan.

METHODS

Adult albino rabbits (N = 24) were used. One eye of each animal had PRK or LASIK with the same refractive correction. Each animal was killed after an interval of up to 6 months. The expression pattern of corneal stromal injury-related molecules with the 2 treatments were compared. Paraffin sections of the cornea were processed immunohistochemically for alpha-smooth muscle actin (alpha-SMA), collagen type IV [alpha1(IV)](2),alpha2(IV), and heat shock protein (HSP) 47 as well as other HSPs. Sections were also examined after hematoxylin and eosin or periodic acid-Schiff staining.

RESULTS

Hematoxylin and eosin staining showed the central epithelium to be thick in PRK-treated corneas. The thick epithelium was restricted to the area around the corneal flap edge adhesion in LASIK-treated corneas at 3 months. Periodic acid-Schiff staining showed an absence of or interruption in the epithelial basement membrane in PRK-treated corneas for up to 6 months. Heat shock protein 47 was detected in keratocytes on day 3 but not after that in PRK-treated corneas. There was no difference in the expression of other HSPs. Alpha-smooth muscle actin was expressed in keratocytes repopulated in the central anterior cornea of PRK-treated corneas at 28 days. Keratocytes with immunoreactivity for these 2 proteins were not seen in LASIK-treated corneas. Collagen IV [alpha1(IV)](2),alpha2(IV) was not detected in either group of corneas. The central epithelium became transiently thicker in PRK-treated corneas.

CONCLUSION

Keratocyte responses to laser stromal ablation were more marked in corneas treated with PRK than in those treated with LASIK.

Comparison of Scheimpflug images of posterior capsule opacification and histological findings in rabbits and humans

PURPOSE

To compare the posterior capsule opacification in Scheimpflug photographic images produced by an electronic anterior eye segment analysis system with the histopathological findings in rabbits and humans.

SETTING

Department of Ophthalmology, Wakayama Medical College, Japan.

METHODS

Opacified posterior capsules were photographed using the EAS-1000 system (Nidek) and were then extracted during vitreous surgery for proliferative diabetic retinopathy or proliferative vitreoretinopathy in 2 patients. In rabbits, phacoemulsification and aspiration (PEA) with intraocular lens (IOL) implantation was performed. The IOL was implanted in the bag or in the sulcus. After intervals of healing, the posterior capsule was photographed with the EAS-1000 and the animals were then killed. In both clinical and experimental specimens, the posterior capsule was processed for light microscopic histology and immunohistochemistry.

RESULTS

Opacified human capsules were well imaged by the EAS-1000. Histology showed that lens epithelial cells proliferated with and without an accumulation of extracellular matrix. Details such as rolling of the capsulotomy edge were seen well. Regenerated lens fibers of Soemmering's ring were seen as a mass within the capsule. In the rabbit model, Scheimpflug images accurately represented the capsules as they appeared histologically.

CONCLUSION

The EAS-1000 system provided faithful, relatively high-resolution images that corresponded to the histologic findings in the posterior capsules after PEA-IOL surgery in humans and rabbits.

Lens epithelial cell regeneration of a capsule-like structure during postoperative healing in rabbits

PURPOSE

To determine whether lens epithelial cells (LECs) can regenerate the lens capsule during healing after lens extraction and intraocular lens (IOL) implantation.

SETTING

Department of Ophthalmology, Wakayama Medical College, Japan.

METHODS

Extracapsular lens extraction and IOL implantation were performed in 5 adult albino rabbits. Lens capsules were examined histologically and immunohistochemically 3 and 5 months later.

RESULTS

Lens epithelial cells proliferated and regenerated lens fibers within the capsular bag. A multilayered homogenous capsule-like structure was present in the equatorial region. The structures contained type IV collagen but not type I collagen.

CONCLUSION

Lens epithelial cells can regenerate lens capsule-like structures during healing after lens extraction. Postoperative LECs without phenotypic conversion to a fibroblastic type may produce this structure.

Shape of lens epithelial cells after intraocular lens implantation

PURPOSE

To evaluate the morphological behavior of lens epithelial cells (LECs) after human cataract surgery with implantation of a poly(methyl methacrylate) (PMMA) or silicone intraocular lens (IOL).

SETTING

Department of Ophthalmology, Fujita Health University, Banbuntane Hotokukai Hospital, Nagoya, Aichi, Japan.

METHODS

Morphological observations of LECs in the patients with IOLs were made by light and transmission electron microscopy. The LECs were from 4 areas: (1) the region below the anterior capsule, touching the IOL; (2) the area between region 1 and the equatorial region; (3) the equatorial region; and (4) the central equatorial region and of the posterior capsule not touching the IOL. Case 1 had implantation of a single-piece IOL with a PMMA optic and haptics. Case 2 had a 3-piece IOL with a PMMA optic and polypropylene haptics. Case 3 had a 3-piece IOL with a silicone optic and polypropylene haptics. Areas 1 and 4 could not be observed in Case 2.

RESULTS

The major difference between the patient with a PMMA IOL (Case 1) and the patient with a silicone IOL (Case 3) was that among the 4 areas observed, collagen fibers were present only in area 1 in Case 1 but in areas 2 or 3 as well in Case 3.

CONCLUSIONS

Fibrous collagen fibers appeared in regions in which LECs adhered and there was capsule contact with the IOL optic. In addition fibrous collagen fibers appeared in more areas in the eye with the silicone IOL than in that with the PMMA IOL, perhaps because IOLs with silicone optics move slightly while in the capsular bag.

Effect of a capsular tension ring on the shape of the capsular bag and opening and the intraocular lens

PURPOSE

To evaluate the effect of a capsular tension ring (CTR) on the shape of the capsular bag, the extent of the capsular opening, and the shape of intraocular lenses (IOLs).

SETTING

Department of Ophthalmology, College of Medicine, The Catholic University of Korea, Seoul, Korea.

METHODS

The corneal button was removed from porcine eyes in vitro. After phacoemulsification was performed, an IOL alone or an IOL and CTR were inserted in the capsular bag in 6 groups of 5 eyes each. The eyes were examined from the posterior aspect using a Miyake technique to assess capsular bag shape and the capsular opening. To evaluate effects of the CTR on IOL shape, rabbit eyes had phacoemulsification and IOL implantation with and without placement of a CTR in vivo. The IOLs were removed from enucleated eyes 3 months postoperatively and compared with unused control IOLs.

RESULTS

The differences between the maximum and minimum diameters of the capsular bags and capsular openings were significantly less in groups with a CTR. Intraocular lens size (difference from haptic to haptic) decreased significantly in eyes with only an IOL compared with normal controls or eyes with both an IOL and CTR.

CONCLUSIONS

The CTR preserved the integrity of the capsular bag diameter, capsular opening, and IOL shape. It is likely that CTR implantation can avert contracture of the capsular bag and capsular opening, preventing IOL decentration.

Intraocular lens bioactivity tested using rabbit corneal tissue cultures

PURPOSE

To evaluate the effects of different intraocular lens (IOL) materials on epithelial cell growth to test the sandwich theory; i.e., a bioactivity-based explanation of posterior capsule opacification (PCO) after cataract surgery.

SETTING

Central Hospital, Vaasa, and Institute of Dentistry and Turku Center for Biomaterials, University of Turku, Finland.

METHODS

Rabbit corneal tissue cultures were set up on poly(methyl methacrylate) (PMMA), heparin-surface-modified (HSM) PMMA, silicone, acrylate, and hydrogel IOLs for 1 week. The tissue consisted of intact epithelium and half the thickness of the corneal stroma, which was placed against the IOL. The growth of the epithelium was examined by light microscopy to evaluate the attachment of the corneal explant to the IOL surface.

RESULTS

All tissue samples grew well under the culture conditions. When grown on PMMA, HSM PMMA, silicone, and hydrogel, the tissue did not attach to the IOL or the epithelium grew around the explant, suggesting that the attachment of the stroma to the IOL was poor or nonexistent. Some explants on acrylate IOLs attached directly to the IOL surface with no epithelial ingrowth between the stroma and the IOL.

CONCLUSIONS

This tissue culture method can be used to examine the behavior of corneal tissue in contact with different IOL materials. The results suggest that the acrylate IOL may have bioactive properties. This, with the lens optic's square edge, may hinder lens epithelial cell proliferation and thus prevent PCO.

Ocular biocompatibility testing of intraocular lenses: a 1 year study in pseudophakic rabbit eyes

PURPOSE

To evaluate the appropriate duration for conducting ocular biocompatibility studies with an intraocular lens (IOL) in the pseudophakic rabbit model.

SETTING

Alcon Laboratories, Inc., Fort Worth, Texas, USA.

METHODS

A single-piece biconvex poly(methyl methacrylate) (PMMA) IOL was implanted in the capsular bag of 18 eyes of New Zealand white rabbits; 8 eyes received sham surgeries. Rabbits were monitored clinically and then sacrificed 6 or 12 months after surgery for histopathological examination of ocular tissues.

RESULTS

Biomicroscopic examination revealed mild ocular changes in all surgical eyes during the first 3 months postoperatively. After that, there was a high incidence of posterior synechias, flare, and posterior capsule opacification (PCO) in eyes with PMMA IOLs. Posterior synechias and flare scores remained mild to moderate throughout the study, whereas PCO severity increased over time. Similar findings were observed in sham eyes. In addition, several eyes with PMMA IOLs developed IOL dislocation, hyphema, iris bombe, and a fibrous membrane covering the IOL. No discernible differences in biomicroscopic scores were observed in eyes at 6 or 12 months. Intraocular pressures and morphology of the corneal endothelium were normal in both groups. Results from histopathological analysis of the ocular tissues were consistent with observations from the biomicroscopic examinations.

CONCLUSION

The results suggest that IOL implantation studies in the pseudophakic rabbit eye should be conducted for 3 or fewer months. Regulatory guidelines requiring longer ocular implantation studies should be revised to reflect the inherently rapid and extensive ocular response in the rabbit model.