[Influence of intraocular lens material and design on the development of posterior capsule opacification]

Influence of total intraocular lens diameter on efficacy and safety for in the bag cataract surgery

CONTEXT

Intraocular lenses with variable total diameter are supposed to fit better in the capsular bag and lead to fewer complications.

AIMS

This study aims to investigate the efficacy and the safety of an intraocular lens model with variable total diameter.

SETTINGS AND DESIGN

Prospective randomized intraindividual study.

SUBJECTS AND METHODS

Thirty-two eyes of sixteen patients with bilateral age-related cataract received standard cataract surgery with implantation of an intraocular lens with a standard diameter in one eye (Quatrix®, Group A) and with a variable total diameter in the fellow eye (Quatrix Evolutive®, Group B). Primary study endpoints included evaluation of refraction stability and posterior capsule opacification (PCO) over a follow-up period of 6 months.

STATISTICAL ANALYSIS USED

SPSS (Version 19.0) was used for statistical analysis.

RESULTS

Uncorrected and corrected distant visual acuity after 6 months were 0.24 and 0.1 LogMAR in Group A and 0.23 and 0.09 LogMAR in Group B, respectively. The objective and manifest spherical equivalent (OSE, MSE) 6 months postoperatively were + 0.65 D and + 0.62 D in Group A compared to + 0.33 D and + 0.33 D in Group B respectively (P = 0.665 for OSE, P = 0.208 for MSE). PCO-index increased statistically significant in both groups (P = 0.004 in Group A, P = 0.046 in Group B), but the difference of PCO-index between both groups was not statistically significant (P = 0.569).

CONCLUSIONS

An intraocular lens with a variable total diameter shows good visual outcomes and safety performance as well as same outcomes concerning postoperative refractive stability and development of PCO compared to an intraocular lens with standard total diameter.

Therapeutic potential of a dual mTORC1/2 inhibitor for the prevention of posterior capsule opacification: An in vitro study

Mammalian target of rapamycin (mTOR) serves a central role in regulating cell growth and survival, and has been demonstrated to be involved in the pathological progression of posterior capsule opacification (PCO). In the present study, the potency of PP242, a novel dual inhibitor of mTOR complex 1/2 (mTORC1/2), in the suppression of the growth of human lens epithelial cells (HLECs) was investigated. Using a Cell Counting Kit‑8 and a wound healing assay, it was demonstrated that PP242 inhibited the proliferation and migration of HLECs. In addition, western blot analysis indicated that PP242 completely inhibited mTORC1 and mTORC2 downstream signaling activities, whereas rapamycin only partially inhibited mTORC1 activity within LECs. Furthermore, PP242 treatment led to an upregulation of the expression levels of p53 and B cell lymphoma‑2 (Bcl‑2)‑associated X and downregulation of Bcl‑2. In addition, flow cytometric analysis demonstrated that PP242 induced the cell cycle arrest at the G0/G1 phase, which may have caused apoptosis and induced autophagy within the LECs. The results of the present study suggested that administration of PP242 may potentially offer a novel therapeutic approach for the prevention of PCO.

Clinical properties of a novel, glistening-free, single-piece, hydrophobic acrylic IOL

A new, single-piece, hydrophobic acrylic lens – the first constructed with a lens optic and haptics comprised of a hydroxyethyl methacrylate-polyethylene glycol phenyl ether acrylate–styrene copolymer, cross-linked with ethylene glycol dimethacrylate, and labeled as “glistening-free” – was recently introduced globally. Glistenings have been a significant source of clinical concern with previous hydrophobic lens designs. This new monofocal lens provides enhanced, clear optics for lens-based surgery. The superior optical clarity of this lens is achieved through the elimination of glistenings, enhanced surface durability, high refractive index, a high Abbe number, and an aspheric design. Additionally, the lens design reduces the risk of developing posterior capsule opacification.

Capsular adhesion to intraocular lens in highly myopic eyes evaluated in vivo using ultralong-scan-depth optical coherence tomography

PURPOSE

To evaluate the in vivo capsular apposition to the intraocular lens (IOL) in subjects with high myopia by ultralong-scan-depth optical coherence tomography (OCT).

DESIGN

Prospective observational case series.

METHODS

Forty eyes from 40 cataract patients scheduled for phacoemulsification surgery at the Affiliated Eye Hospital, Wenzhou Medical College were studied, of which 20 eyes were highly myopic (axial length >26 mm) and 20 eyes were emmetropic (22 mm < axial length <24.5 mm). All eyes were examined with a custom-built ultralong-scan-depth OCT at 4 hours, 1 day, 7 days, 14 days, and 28 days after surgery.

RESULTS

Anterior capsule contact with the IOL was significantly delayed in highly myopic eyes. Complete apposition of the posterior capsule with the IOL was significantly less common among highly myopic eyes than in emmetropic eyes (4 vs 16 eyes; P = .001). Posterior capsule adhesion to the IOL was inversely correlated with axial length (r = -0.494, P < .001, nonparametric Spearman test). The 3 types of complete adhesive capsular bend configurations observed were classified as anterior adhesion, middle adhesion, and posterior adhesion. Incomplete adhesion patterns were classified as funnel adhesion, parallel adhesion, and furcate adhesion. Five highly myopic eyes had slight posterior capsule opacification (PCO) at the last follow-up, as did 1 emmetropic eye.

CONCLUSIONS

Ultralong-scan-depth OCT revealed weak capsular adhesion and incompletely adhesive types of capsular bend in highly myopic eyes. These features presumably increase the likelihood of PCO during the early postoperative period.

[Early in-the-bag spontaneous intraocular lens dislocation of hydrophilic acryl single piece lenses following uncomplicated phacoemulsification]

BACKGROUND

As techniques for cataract surgery have evolved, spontaneous intraocular lens (IOL) dislocation in patients with no ocular pathology arises less frequently. We present seven consecutive cases of uncomplicated cataract surgery with early in-the-bag spontaneous intraocular lens dislocation for which the same type of hydrophilic single piece lens was used.

MATERIAL AND METHODS

A retrospective analysis was conducted on seven cases involving patients with IOL dislocation who underwent uncomplicated cataract surgery within a period of 4 months (October 2010 to January 2011) using the same type of single piece IOL. The median age of the 7 patients was 73 years and IOL repositioning was performed after an average of 10 weeks.

RESULTS

Sulcus repositioning could be carried out in only five of the seven patients and IOL repositioning within the capsule was achieved in one patient. A second patient exhibited IOL dislocation after yttrium aluminium garnet (YAG) laser capsulotomy. Explantation of the IOL and sulcus implantation of another IOL type (Acrysof MA50 MB) was necessary for a third patient. A fourth case presented an angled IOL haptic and dislocation of the IOL in the sulcus position.

DISCUSSION

Even after uncomplicated cataract surgery, spontaneous in-the-bag IOL dislocation in patients with no ocular pathology may occur due to a hydrophilic lens material which induces stronger anterior capsular phimosis (ACP) in comparison to alternative materials. In combination with a thin lens design this may result in angled IOL haptics and IOL dislocation.

CONCLUSIONS

Careful selection of suitable lens design and material according to individual predisposing factors is necessary. This retrospective case study demonstrates that the combination of hydrophilic lens material and a thin lens design may result in early spontaneous IOL dislocation. Furthermore, as established in one case, YAG laser capsulotomy may induce IOL dislocation if the lens design cannot withstand capsular fibrosis.

[Subluxation of hydrophilic acrylate intraocular lenses due to massive capsular fibrosis]

BACKGROUND

Compared with other biomaterials, hydrophilic acrylate provides better uveal biocompatibility, lower adhesion rates of bacteria and silicone oil, and less glare. Because of reduced capsular biocompatibility, increased fibrosis may initiate dislocation of the intraocular lens (IOL).

PATIENTS

In six eyes of four patients, enhanced fibroses led to IOL dislocation, leading to an IOL exchange an average of 40 weeks after implantation of the same hydrophilic acrylate lens type.

DISCUSSION

Predisposing factors were found in 90% of all reported cases of IOL dislocation in the literature, but not in the cases described here. The lens type that was implanted was unable to adapt to the massive fibrosis induced by its hydrophilic biomaterial.

CONCLUSIONS

The pattern of lens opacification should receive attention when one is choosing an IOL type. Eyes showing pseudoexfoliation syndrome as well as post-uveitis eyes might require a hydrophilic IOL for less cellular reaction, whereas a posterior subcapsular cataract might need a hydrophobic IOL to prevent a massive capsular fibrosis. In the case of increased capsular contraction, unreflected YAG laser capsulotomy may result in IOL subluxation when the lens design cannot handle capsule shrinkage, as demonstrated here.

Pattern of posterior capsule opacification models 2 years postoperatively with 2 single-piece acrylic intraocular lenses

PURPOSE

To compare posterior capsule opacification (PCO) in eyes with 1 of 2 models of 1-piece acrylic intraocular lenses (IOLs).

SETTING

Ambulatory surgery center.

METHODS

This paired-eye study evaluated patients who had implantation of a Tecnis AAB00 IOL with a continuous optic edge in 1 eye and an AcrySof SA60AT or SN60AT IOL with an interrupted optic edge in the fellow eye. Exclusion criteria were anterior capsule overlap onto the IOL optic of fewer than 360 degrees, neodymium:YAG laser capsulotomy, postoperative time fewer than 24 months or more than 30 months, pseudoexfoliation, glaucoma, history of iritis, and surgical complications that would affect the assessment of PCO. Posterior capsule opacification was assessed using the Evaluation of Posterior Capsular Opacification (EPCO) system on a scale of 0 (none) to 4 (severe opacity with a darkening effect).

RESULTS

In 13 of 14 patients, the eye with the interrupted-edge IOL had a higher EPCO score than the eye with the continuous-edge IOL. The mean EPCO score was 0.39 and 0.08, respectively; the difference was statistically significant (P = .012). The PCO density was greater in eyes with the interrupted-edge IOL, with 35% having an EPCO score of 3 or 4; no eye with a continuous-edge IOL had a score that high.

CONCLUSION

Eyes with an IOL with a continuous 360-degree square edge had significantly less PCO than eyes with an IOL with a square edge that was interrupted at the optic-haptic junction.

Posterior capsule opacification

Posterior Capsule Opacification (PCO) is the most common complication of cataract surgery. At present the only means of treating cataract is by surgical intervention, and this initially restores high visual quality. Unfortunately, PCO develops in a significant proportion of patients to such an extent that a secondary loss of vision occurs. A modern cataract operation generates a capsular bag, which comprises a proportion of the anterior and the entire posterior capsule. The bag remains in situ, partitions the aqueous and vitreous humours, and in the majority of cases, houses an intraocular lens. The production of a capsular bag following surgery permits a free passage of light along the visual axis through the transparent intraocular lens and thin acellular posterior capsule. However, on the remaining anterior capsule, lens epithelial cells stubbornly reside despite enduring the rigours of surgical trauma. This resilient group of cells then begin to re-colonise the denuded regions of the anterior capsule, encroach onto the intraocular lens surface, occupy regions of the outer anterior capsule and most importantly of all begin to colonise the previously cell-free posterior capsule. Cells continue to divide, begin to cover the posterior capsule and can ultimately encroach on the visual axis resulting in changes to the matrix and cell organization that can give rise to light scatter. This review will describe the biological mechanisms driving PCO progression and discuss the influence of IOL design, surgical techniques and putative drug therapies in regulating the rate and severity of PCO.

In situ ablation of lens epithelial cells in porcine eyes with the laser photolysis system

PURPOSE

To evaluate the efficacy of the laser photolysis system (LPS) (A.R.C. Laser GmbH) in removing lens epithelial cells (LECs) to prevent posterior capsule opacification (PCO) in an in situ model.

SETTING

Department of Ophthalmology, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany.

METHODS

Twelve enucleated porcine eyes fixed in a specially developed eye holder were randomly assigned to the control or treatment group. The cornea and iris were removed from all eyes, and a small paracentral capsulorhexis was performed. The lens nucleus and cortex were extracted by hydroexpression. The tip of the LPS was inserted into the capsular bag of eyes in the treatment group, and 50 pulses (10 mJ) were applied to the anterior capsule. All capsules were evaluated for remaining LECs by confocal laser scanning microscopy (HRT II with the Rostock Cornea Module, Heidelberg Engineering) and standard histology (hematoxylin-eosin and periodic acid-Schiff stains).

RESULTS

In the control group, a homogenous layer of LECs attached to the anterior capsule was seen with both evaluation methods. In the treatment group, no LECs adherent to the anterior capsule were detected, suggesting complete ablation of LECs from the capsule. Small islands of equatorial LECs were found in places in which the remaining cortical fibers protected cells from the laser shockwave. The results of the confocal laser scanning microscopy were confirmed by standard histology.

CONCLUSIONS

The LPS completely ablated LECs in an in situ model of cataract extraction. This system might prevent formation of PCO in vivo.

Prospective, non-randomised, long term clinical evaluation of a foldable hydrophilic single piece intraocular lens: results of the Centerflex FDA study

BACKGROUND

Owing to the improvement of modern intraocular lenses (IOLs) in terms of design and material, posterior capsule opacification (PCO) usually takes 2-3 years to develop. Thus, long term clinical evaluation of new implants is important.

METHODS

As part of a prospective, non-randomised FDA trial, the Rayner Centerflex, a foldable hydrophilic acrylic, single piece IOL was implanted in one eye of 83 patients (mean age 73.5 (SD 7.0) years). Over 3 years postoperatively, a standardised FDA protocol concerning IOL safety and efficacy was followed including evaluation of spherical equivalent (SE), best corrected distance visual acuity (BCDVA), endothelial cell count (ECC), flare meter values, PCO development, and anterior capsule shrinkage.

RESULTS

Postoperatively, mean SE was stable ranging between -0.3D and 0.17D. After 1-2 months, all patients achieved a BCDVA of 20/40 or better. At 3-6 months postoperatively, mean ECC decreased from 2612 (SD 346) cells/mm2 to 2380 (316) cells/mm2. Mean PCO score for the entire optic increased from 0.20 (0.20) months (3-6 months postoperatively) to 0.87 (0.57) resulting in a Nd:YAG rate of 29.41% after 3 years. No anterior capsule shrinkage was found.

CONCLUSION

The Centerflex showed excellent functional results, low values for endothelial cell loss and inflammatory signs, and no anterior capsule shrinkage. PCO formation was higher compared to other IOLs, which could be explained by the incomplete sharp edge at the optic-haptic junctions representing an "Achilles' heel" for cell ingrowth.