After-cataract and ocular growth in newborn rabbit eyes implanted with a capsule tension ring

Effect of an MG132-Sustained Drug Delivery Capsular Ring on the Inhibition of Posterior Capsule Opacification in a Rabbit Model

PURPOSE

To design an MG132-sustained drug delivery capsular ring (SDDCR) and investigate its effect on the inhibition of posterior capsule opacification (PCO) in a rabbit model.

METHODS

The SDDCRs were prepared by forming a slice of film made by the mixture of poly lactic-co-glycolic acid (PLGA) and MG132 on the surface of capsular tension rings (CTRs). The drug-loading capacity, entrapment efficiency, and in vitro release of the drug-containing film were detected. Eighteen New Zealand white rabbits were operated with phacoemulsification and MG132-SDDCRs/PLGA-CTRs/CTRs implantation in the single eye. The images of the anterior segments were acquired at certain days, and the epithelial-mesenchymal transition (EMT) markers were detected by western blot and immunofluorescence.

RESULTS

The drug-loading capacity and entrapment efficiency of MG132-SDDCRs were 1.15% ± 0.04% and 66.16% ± 0.027%, respectively, and the drug released well within a month. The PCO degree of the MG132-SDDCR group was significantly lower than the other groups. The expression of alpha-smooth muscle actin, fibronectin, vimentin, and collagen-I was lower, and the expression of E-cadherin (E-cad) was higher in the MG132-SDDCR group than the other groups.

CONCLUSIONS

MG132-SDDCRs could be established successfully. The PCO process was prevented, and the expression of EMT markers was inhibited by the implantation of MG132-SDDCRs, indicating that this could be a potential treatment against PCO.

Cionni endocapsular ring implantation in Marfan's Syndrome

OBJECTIVES

To evaluate the visual outcomes, intraoperative and postoperative complications of Cionni ring implantation in eyes with a subluxated lens associated with Marfan Syndrome.

METHODS

This case series included 15 eyes of 12 patients aged 19-56 years with a subluxated lens secondary to Marfan's syndrome operataed at the Departament of Ophtalmology, Toronto Western Hospital between 2003 and 2007. A 2-eyelet Cionni ring and an AcrySof (Alcon) foldable intraocular lens (IOL) were implanted in 13 eyes. Two eyes had trans-scleral IOL fixation in the ciliary sulcus. Best-corrected visual acuity, wavefront evaluation of eye aberration and complication rates were analysed.

RESULTS

In all eyes, capsular bag centration was excellent. Preoperative visual acuity ranged from 20/50 to counting fingers, and improved to better than 20/40 in all eyes. The mean follow-up duration was 14+/-9.49 months. The most frequent postoperative complication was posterior capsule opacification, which occurred in 3 eyes (18.7%), 2 of which required a neodymium:YAG posterior capsulotomy. No eye developed retinal detachment. Total eye aberration, tilt and high-order aberrations with a 6-mm pupil diameter decreased significantly after surgery (n = 5): Total eye aberration decreased from a mean of 14.8+/-5.5 preoperatively to 2.1+/-4.3 microns after the operation. Tilt was decreased from 4.1+/-2.5 to 0.12+/-2.1 microns, and high-order aberrations decreased from 4.37+/-3.8 microns, before the operation, to 1.47+/-3.5 after the operation.

CONCLUSION

Cionni ring implantation is an effective procedure to correct partial lens subluxation and has few complications (during 14 months of follow-up) in patients with Marfan's Syndrome.

Evaluation of the effects of hydrodissection with antimitotics using a rabbit model of Soemmering's ring formation

BACKGROUND

Regeneration/proliferation of lens material within the capsular bag still is the most frequent complication after cataract surgery. We aimed to evaluate the effects of hydrodissection with low doses of antimitotics on the overall regeneration/proliferation of lens material in rabbit eyes, using a model allowing the lens material to be confined to the equatorial region of the capsular bag, facilitating its quantification.

METHODS

Twelve albino rabbits underwent bilateral phacoemulsification. Their eyes were randomized to receive 0.4 cc of balanced salt solution, 5-fluorouracil (12.5 mg/mL) or mitomycin C (0.1 mg/mL) during hydrodissection. They were left aphakic, so the capsulorhexis would fuse with the posterior capsule postoperatively. After 4 weeks, killing/enucleation was performed. Regeneration/proliferation of lens material within the equatorial capsular bag (Soemmering's ring) was graded from the Miyake-Apple view (0-4). Its area was also calculated (microm(2)) from direct measurements performed on histological sections.

RESULTS

The capsulorhexis margin fused with the peripheral posterior capsule, so the central posterior capsule remained clear. There was no significant difference among the groups (Kruskal-Wallis test) regarding Soemmering's ring gross grading (P = 0.511), number of lens epithelial cell layers lining the inner surface of the capsular bag (P = 0.310) and Soemmering's ring microscopic cross-sectional area (P = 0.638).

CONCLUSIONS

The effect of different solutions on after-cataract should be assessed in terms of overall regeneration/proliferation of lens material within the capsular bag, in addition to posterior capsule opacification. When administered in low doses during hydrodissection, 5-fluorouracil and mitomycin C did not show a significant inhibitory effect on after-cataract formation in rabbit eyes.

Rate of axial growth after congenital cataract surgery

PURPOSE

To evaluate the rate of axial growth after congenital cataract surgery.

DESIGN

Prospective observational case series.

METHODS

Rate of axial growth of 158 eyes (79 children < 10 years) undergoing surgery was correlated with age at surgery, laterality, and visual axis obscuration. After measuring axial length (AL) at each follow-up, the mean AL was calculated, adding the AL of all eyes divided by their total number. Rate of axial growth is the percentage difference between preoperative mean AL and mean AL at last follow up. The temporal profile of RAG is the difference between two consecutive mean ALs with respect to the previous reading. The follow-up period was 58.96 +/- 2.02 months. The student' paired t test and independent sample t test were applied. The main outcome measure was RAG.

RESULTS

Rate of axial growth in children operated at < or = 1 year (23.5%) was significantly higher than in those at < or = 3 years (4.8%; P = .0001, confidence interval [CI] 1.05-3.2) and at < or = 10 years (4.3%; P = .0001, CI 1.3-3.1). In children operated at <or = 1 year, temporal profile of RAG was higher in the first 2 years after surgery. Rate of axial growth was higher in patients with unilateral pseudophakia at < or = 1 year (25.53%) than in age-matched patients with bilateral pseudophakia (18.50%; P = .001, CI -13 to -0.2). Rate of axial growth was negligible in children with visual axis obscuration in any group.

CONCLUSION

Rate of axial growth is higher in children < or = 1 year and increases until the second year after surgery. Unilateral pseudophakia revealed accelerated growth compared with bilateral pseudophakia. Visual axis obscuration does not influence rate of axial growth.

Management of a posteriorly dislocated endocapsular tension ring and a foldable acrylic intraocular lens

We report a rare case of late spontaneous extension of a posterior capsule tear from lateral traction of an endocapsular ring, resulting in dislocation of the capsular tension ring and acrylic intraocular lens (IOL) into the vitreous cavity. A 3-port pars plana vitrectomy was performed to explant the prostheses; the eye was made pseudophakic by placement of a scleral-fixated posterior chamber IOL. The combined triple procedure was safe and effective.

Intraoperative and postoperative complications of Cionni endocapsular ring implantation

PURPOSE

To analyze the intraoperative and postoperative complications of Cionni ring implantation in eyes with a subluxated lens or zonular weakness.

SETTING

Departamento de Oftalmología, Clínica Universitaria de Navarra, Universidad de Navarra, Pamplona, Spain.

METHODS

This case series comprised 7 eyes of 5 patients with a subluxated lens or zonular weakness secondary to Marfan's syndrome (n = 2), traumatic cataract (n = 2), or megalocornea (n = 1) or of unknown etiology (n = 2). An AcrySof (Alcon) foldable intraocular lens (IOL) was implanted in all eyes. A 2-eyelet Cionni ring was implanted in 1 eye and a 1-eyelet Cionni ring, in 6 eyes. The Cionni ring was secured in position with a transscleral suture knotted to the ring's hook, avoiding peripheral perforation of the capsular bag.

RESULTS

In 1 eye, corectopia was inadvertently produced by passing the suture needle through the iris root; lens subluxation temporarily increased during ring rotation and implantation. However, after the transscleral suture was tightened, capsular bag centration was excellent. In the eye with megalocornea, traction from the 2 hooks tore the edge of the anterior capsule rim. The most frequent postoperative complication was posterior capsule opacification, which occurred in 5 eyes, 2 of which required a neodymium:YAG posterior capsulotomy. After 1 year, the Cionni ring continued to provide excellent stability and capsular bag and IOL positioning in all cases.

CONCLUSIONS

Results indicate that Cionni ring implantation is an acceptable procedure to correct limited lens subluxation, preserves the capsular bag, and has few significant complications.

Effect of 3-piece AcrySof and downsized heparin-surface-modified poly(methyl methacrylate) intraocular lenses in infant rabbit eyes

PURPOSE

To evaluate after-cataract formation, ocular growth, and intraocular lens (IOL) behavior in lensectomized infant rabbit eyes implanted with a downsized heparin-surface-modified poly(methyl methacrylate) (HSM PMMA) IOL with long haptics or a 3-piece AcrySof(R) IOL (Alcon Laboratories, Inc.).

SETTING

St. Erik's Eye Hospital, Stockholm, Sweden.

METHODS

Clear lens extraction was performed in both eyes of 3-week-old rabbits. In Group 1 (n = 9), a downsized HSM PMMA IOL with long haptics was implanted in 1 eye and in Group 2 (n = 9), a 3-piece AcrySof IOL was implanted in 1 eye. The fellow eyes remained aphakic.

RESULTS

The amount of after-cataract was significantly less in the eyes with the IOLs than in the aphakic eyes. The eyes with the HSM PMMA IOL had significantly less after-cataract than those with the AcrySof IOL. No significant difference in axial length was noted between the IOL eyes and the aphakic eyes in either group. In the eyes with the 3-piece AcrySof IOL, there was anterior movement of the optic with occlusion of the pupil.

CONCLUSIONS

Eyes with the HSM PMMA IOL and the AcrySof IOL had less after-cataract than the aphakic eyes. The HSM PMMA IOL, however, inhibited after-cataract production significantly better than the AcrySof IOL. The 3-piece AcrySof IOL was seriously deformed in the infant rabbit eyes and caused occlusion of the pupil. Surgeons should be cautious in implanting this AcrySof IOL in the eyes of newborns or in eyes with severe microphthalmia.

Intracapsular ring sustained 5-fluorouracil delivery system for the prevention of posterior capsule opacification in rabbits: a histological study

PURPOSE

To evaluate the efficacy of an intracapsular ring releasing 5-fluorouracil (5-FU) in preventing posterior capsule opacification (PCO) in rabbit eyes.

SETTING

Center for Research on Ocular Therapeutics and Biodevices, Storm Eye Institute, Medical University of South Carolina, Charleston, South Carolina, USA, and Chu Morvan, Department d'Ophtalmologie, University of Brest, France.

METHODS

Seventeen rabbits were divided into 3 groups: Group 1, 6 rabbits (6 eyes), had phacoemulsification only (control group); Group 2, 6 rabbits (6 eyes), had phacoemulsification with implantation of an open-loop hydrogel intracapsular ring; Group 3, 5 rabbits (5 eyes), had phacoemulsification with implantation of a ring with sustained release of 0.25 microg/h of 5-FU for 9 days. All eyes were followed for 8 weeks before enucleation. Capsular bag shrinkage and the position of the intracapsular ring were assessed, and central and peripheral PCO was evaluated for intensity and area by stereomicroscopy from a posterior (Miyake-Apple) view. The residual equatorial lens epithelial cells (LECs) were counted by the same observer in histological sections. Transmission electron microscopy (TEM) of the cornea, capsular bag, and retina was done to evaluate the toxicity of 5-FU.

RESULTS

No significant difference was seen in the degree of capsular bag shrinkage in the 3 groups. The intracapsular ring was decentered in 2 eyes (1 each in Groups 2 and 3). There was a statistically significant difference (P <.05, Student t test) between Group 1 and Groups 2 and 3 in the area and intensity of central PCO. There was no difference between Groups 2 and 3 in the intensity of central PCO. No evidence of 5-FU toxicity to intraocular structures (cornea, capsular bag, and retina) was demonstrated on TEM analysis.

CONCLUSION

Implantation of an intracapsular ring may prevent central PCO after cataract surgery by mechanically blocking LEC migration toward the central visual axis. The potential pharmacological effect of 5-FU in PCO prevention was not demonstrated.

Intraocular lens designed for the newborn infant eye

PURPOSE

To evaluate the effects of an intraocular lens (IOL) designed for small eyes after clear lens extraction in an animal model.

SETTING

St. Erik's Eye Hospital, Karolinska Institute, Stockholm, Sweden.

METHODS

Clear lens extraction was performed in both eyes in 19 3-week-old rabbits. In 1 randomly selected eye of each rabbit, a small IOL with long haptics was implanted. Axial length, corneal thickness, corneal diameter, and intraocular pressure were measured preoperatively and every month for 6 months postoperatively. Six months after surgery, the wet mass of the after-cataract was determined.

RESULTS

The IOL remained well centered in all eyes. Four animals developed severe glaucoma in 5 eyes (3 aphakic and 2 pseudophakic) soon after surgery and were excluded. In the 15 animals completing the study, signs of glaucoma evolved in 7 animals (5 aphakic and 4 pseudophakic eyes). In aphakic eyes, significant amounts of after-cataract (median 250 mg) developed in all 15 surviving animals. In pseudophakic eyes, small amounts of after-cataract (median 30 mg) were present. During the first 2 months after surgery, ocular growth was less in pseudophakic eyes than in aphakic eyes.

CONCLUSIONS

Results indicate that implantation of a down-sized IOL with long haptics in small eyes is safe. Considerable less after-cataract was found in eyes with the IOL than in aphakic control eyes.

After-cataract and secondary glaucoma in the aphakic infant rabbit

PURPOSE

To study the association between after-cataract and secondary glaucoma after lensectomy and 5-fluorouracil treatment in an experimental infant rabbit model.

SETTING

St Erik Eye Hospital, Karolinska Institute, Stockholm, Sweden.

METHODS

Lensectomy was performed in both eyes of 16 3-week-old rabbits. One randomly selected eye in each rabbit was injected with 2.5 mg of 5-fluorouracil (5-FU) at surgery and 5.0 mg the day after surgery to reduce the formation of after-cataract. Axial length, corneal thickness, corneal diameter, and intraocular pressure were measured preoperatively and 4 times during the 6 months following surgery. Six months after surgery, the wet weight of the after-cataract was determined.

RESULTS

In 16 aphakic eyes treated with 5-FU, no or a minimal amount (<0.001 g) of after-cataract developed. None of the eyes showed signs of secondary glaucoma. Of 16 aphakic eyes not treated with 5-FU, 10 developed considerable amounts of after-cataract (>0.10 g); 8 of these developed glaucoma. The other 6 eyes had no or minimal after-cataract and did not develop secondary glaucoma. The relationship between after-cataract and secondary glaucoma was statistically significant.

CONCLUSION

A significant relationship between the amount of after-cataract and the development of secondary glaucoma was found in aphakic infant rabbit eyes.

Complications of endocapsular tension ring implantation in a child with Marfan's syndrome

A 4-year-old boy with Marfan's syndrome had severe visual impairment after subluxation of the crystalline lens with bisection of the pupil. In the first eye, a capsular tension ring and an intraocular lens (IOL) were uneventfully placed in the capsular bag after phacoemulsification. During implantation of the endocapsular tension ring in the second eye, an inadvertent tear of the anterior capsule occurred, and the posterior chamber IOL was placed in the sulcus. In both eyes, severe lens epithelial proliferation with secondary IOL decentration developed postoperatively. Several surgical revisions were necessary to keep the IOL within the optical axis. In the eye with the sulcus-implanted IOL, the endocapsular tension ring was markedly decentered.

The capsular tension ring: designs, applications, and techniques

Originally, the open poly(methyl methacrylate) (PMMA) capsular tension ring (CTR) was designed to compensate for zonular defects or to stretch the posterior capsule in highly myopic eyes not receiving an intraocular lens (IOL). We address the variety of subsequent designs, applications, and techniques that have evolved. With pre-existing or intraoperative zonular defects, a standard CTR may be inserted before or at any time during cataract removal to maintain or re-establish an extended capsular diaphragm. For profound zonular dialysis or weakness, a CTR was designed for scleral fixation. Capsular tension rings with integrated tinted sector shields have been developed to compensate for sector iris colobomas or aniridia. The CTR has also been used as a measuring gauge for in vivo quantification of capsule dimensions and postoperative capsular shrinkage. The CTR has improved control during primary posterior capsulorhexis and prevented oval distortion along the lens axis postoperatively. During combined cataract and vitreous surgery, a CTR prevents capsule damage and provides undisturbed peripheral visualization before IOL implantation. Capsular tension rings may also influence capsule opacification formation. A special band-shaped CTR with sharp edges was developed to inhibit lens epithelial cell migration and avoid capsulorhexis-optic contact.

Pediatric cataracts

There have been major changes over the past 5 to 10 years in our understanding of both the chemical basis for and the surgical treatment of cataract in infants and children. Important questions that remain to be answered include the appropriate power and design selection criteria for intraocular lens implantation, as well as management of the posterior capsule and long-term refractive sequelae. In the past 10 years, there have been radical changes in the management of visually significant cataract in the infant and child. Whereas lens removal, subtotal posterior capsulectomy, vitrectomy, and aphakia were once the standard of care, many physicians now feel that small incisions, phacoemulsification technology, and intraocular lenses (IOLs) are best for these patients. Work is continuing to accumulate a significant body of evidence to evaluate results of these changes in technique and to develop optimal IOL designs and selection criteria for these specialized cataract patients.

Intraocular lens calculator for childhood cataract

PURPOSE

To evaluate a computer program to predict the pseudophakic refraction of a child at any age.

SETTING

A pediatric ophthalmology practice.

METHODS

A computer program was written for Windows 95 that calculates the initial postoperative pseudophakic refraction of a child using Holladay's formula, given the axial length and keratometry readings. The logarithmic model was used to predict the ultimate refraction at age 20 years and chart the predicted curve of refractive error with standard deviations.

RESULTS

The program provided a graph of a child's predicted pseudophakic refraction versus age that would allow the surgeon to dynamically view the effects of changing the intraocular lens (IOL) power.

CONCLUSIONS

If pseudophakia and aphakia have the same effect on the growth of the eye, this program should accurately predict the myopic shift of a pseudophakic child. This could help guide the surgeon's choice of IOL power.

After-cataract and ocular growth in newborn rabbit eyes implanted with a capsule tension ring

PURPOSE

To examine after-cataract and eye growth in lensectomized newborn rabbits implanted with capsule tension rings of different sizes.

SETTING

S:t Eriks Eye Hospital, Karolinska Institute, Stockholm, Sweden.

METHODS

Two groups of 24-day-old rabbits were used. In Group 1 (n = 9), lensectomy was performed in both eyes. In one randomly selected eye, an open poly(methyl methacrylate) (PMMA) capsule tension ring with a 7.0 mm diameter and 0.13 mm thickness was implanted in the capsular bag. The other eye was left aphakic. In Group 2 (n = 10), an open PMMA capsule tension ring with a 10.0 mm diameter and 0.13 mm thickness was implanted in one randomly selected eye, and the other eye was left aphakic. Axial length, corneal diameter, corneal thickness, and intraocular pressure (IOP) were measured in all eyes preoperatively and 1, 2, and 3 months after surgery. The wet mass of the after-cataract was measured at 3 months. Three Group 1 eyes and four Group 2 eyes developed secondary glaucoma and were excluded from the study.

RESULTS

Axial growth did not differ significantly between the eyes implanted with the 7.0 mm ring and the aphakic eyes (mean difference 0.01 mm; F3;15 = 0.02; P > .25). Corneal diameter also did not differ (two-way analysis of variance [ANOVA]). Axial length growth was less in the eyes implanted with the 10.0 mm ring than in the aphakic eyes (mean difference 1.05 mm; F3;15 = 2.06; P < .25). The average decrease in corneal diameter growth was 1.0 mm in the implanted eyes. Growth in the eyes with the 10.0 mm ring was significantly less than in the eyes with the 7.0 mm ring (P = .05, Wilcoxon rank-sum test). Corneal thickness and IOP did not differ significantly between eyes (F3;15 = 0.6; P > .25; two-way ANOVA). Amount of after-cataract did not differ significantly between the aphakic eyes and the eyes implanted with the 7.0 mm ring. It was significantly less in the eyes with the 10.0 mm ring than in those with the 7.0 mm ring (Wilcoxon signed-rank test) and in the aphakic eyes (P < .025, Wilcoxon rank-sum test).

CONCLUSION

In the young rabbit eye, a 10.0 mm capsule ring reduced the eye growth compared with both the aphakic eye and the eye implanted with a 7.0 mm ring. The 10.0 mm ring also inhibited the production of after-cataract compared with the production in the aphakic eye and the eye implanted with the 7.0 mm ring.