Qun Peng

Surgical prevention of posterior capsule opacification. Part 1: Progress in eliminating this complication of cataract surgery.

PURPOSE To evaluate over almost 2 decades the success of a component of cataract surgery that represents a critical step in reducing the incidence of posterior capsule opacification (PCO); namely, the efficacy of cortical cleanup. SETTING Center for Research on Ocular Therapeutics and Biodevices, Storm Eye Institute, Department of Ophthalmology, Medical University of South Carolina, Charleston, South Carolina, USA. METHODS Accessioned from the early 1980s to 1997, 3320 eyes obtained postmortem with posterior chamber intraocular lenses were analyzed with respect to formation of a postoperative Soemmerings ring. This anatomic lesion, the precursor of clinical PCO, represents an important and measurable indication of the quality of cortical cleanup. Its formation was documented using Miyake-Apple posterior photographic analysis. RESULTS The quality and thoroughness of cortical cleanup and overall effectiveness in eliminating retained and/or regenerating cortical cells, as measured by scoring of Soemmerings rings, showed virtually no net change since the early 1980s. The intensity of Soemmerings ring was higher in the most recent specimens than in those in the early 1980s. CONCLUSION The results indicate that renewed attention to cortical cleanup in cataract surgery is warranted for significant reduction in incidence or the elimination of PCO. More attention to the hydrodissection (cortical cleaving hydrodissection) step of the procedure is likely a practical, immediately implementable, and inexpensive remedy.

Surgical prevention of posterior capsule opacification. Part 3: Intraocular lens optic barrier effect as a second line of defense.

PURPOSE To emphasize an important aspect of preventing posterior capsule opacification (PCO), the barrier effect established by the optic of a posterior chamber intraocular lens (PC IOL), and present a new classification regarding capsular bag status after extra-capsular cataract extraction, including phacoemulsification. SETTING Center for Research on Ocular Therapeutics and Biodevices, Storm Eye Institute, Medical University of South Carolina, Charleston, South Carolina, USA. METHODS This analysis included 150 consecutive eyes obtained postmortem with United States-manufactured PC IOLs including (1) poly(methyl methacrylate), (2) silicone, and (3) hydrophobic acrylic designs that were accessioned in the Center from September 1995 to January 1, 1998. Gross photographs from behind (Miyake-Apple views) were taken and serial histologic sections prepared. RESULTS Microscopic analysis of the 150 eyes showed that the morphologic appearance of the capsular bag could be grouped into 2 categories: (1) those with little or no evidence of retained cortical material and cells, and (2) those with retained cortical material and cells in which a Soemmerings ring formed. With the latter, when a distinct barricade to cellular migration created by the IOL optic was noted, 2 discrete configurations occurred, depending on the different geometries of the optic components. With a classic biconvex optic with a curved and tapered edge, in many instances some ingrowth of cells proceeded posteriorly around the edge of the IOL optic in the direction of the central axis. With a lens optic that had a squared, truncated, and relatively thick edge, there was often abrupt termination of cells at the peripheral edge of the optic. The posterior capsule subtending the entire optic zone was therefore relatively or totally cell free. CONCLUSIONS The barrier effect of the IOL optic appears to be of critical importance in retarding ingrowth of cells, functioning as a second line of defense when cortical cleanup is incomplete. Analysis of PC IOLs obtained postmortem showed that a square, truncated optic edge seemed to provide the maximum impediment to cell growth behind the IOL optic.

Anterior capsule opacification: a histopathological study comparing different IOL styles.

OBJECTIVE To compare the degree of anterior capsule opacification (ACO) in human eyes obtained post-mortem containing various rigid and foldable posterior chamber intraocular lens (PC-IOL) designs. DESIGN Comparative autopsy tissue study with clinicopathologic correlations. MATERIALS Four hundred sixty human globes containing the following PC-IOL styles were analyzed: (1) one-piece polymethylmethacrylate (PMMA) optic-PMMA haptic (n = 50), (2) one-piece silicone-plate IOL, large hole (n = 40), (3) one-piece silicone-plate IOL, small hole (n = 67), (4) three-piece PMMA optic-PMMA/Prolene haptic (n = 51), (5) three-piece acrylic optic-PMMA haptic (n = 96), (6) three-piece silicone optic-PMMA haptic (n = 24), (7) three-piece silicone optic-polyimide haptic (n = 40), and (8) three-piece silicone optic-prolene haptic (n = 92). TESTING The globes were sectioned in the equatorial plane for gross examination and then processed through paraffin; sectioned, and stained with hematoxylin-eosin, periodic acid-Schiff, and Massons trichrome stains; and examined by light microscopy. MAIN OUTCOME MEASURES Anterior capsule opacification was scored in each eye by grading the histologic sections from 0 to III, according to the amount (thickness) of proliferative tissue and cells measured in sagittal sections on the inner surface of the anterior capsule at the capsulorhexis margin. RESULTS The difference among the eight groups was significant (P < 0.0001). Mean ACO scores were highest with the large and small hole one-piece silicone-plate lenses (1.77 +/- 0.86 and 1.28 +/- 0.77, respectively). The lowest mean score was observed in the group of three-piece acrylic optic-PMMA haptics lenses (0.51 +/- 0.52). CONCLUSIONS Our results confirm previous clinical observations that the rate of ACO is relatively high with plate-haptic silicone IOLs. The lowest rate was noted with the three-piece acrylic optic-PMMA haptic IOL. The IOL design and IOL material are significant factors in the development of ACO.

Interlenticular opacification: clinicopathological correlation of a complication of posterior chamber piggyback intraocular lenses.

PURPOSE To present a clinicopathological correlation of 2 pairs of piggyback posterior chamber intraocular lenses (PC IOLs) explanted because of opacification between the lens optics. SETTING Gayton Health Center, Eyesight Associates of Middle Georgia, Warner Robins, Georgia, and Center for Research on Ocular Therapeutics and Biodevices, Storm Eye Institute, Medical University of South Carolina, Charleston, South Carolina, USA. METHODS Two pairs of piggyback AcrySof lenses were explanted from 2 patients with significant visual loss related to opacification between the optics. They were submitted for pathological analysis. Gross and histopathological examinations were performed, and photomicroscopy was used to document the results. RESULTS Gross examination showed accumulation of a membrane-like white material between the lenses. Histopathological examination revealed that the tissue consisted of retained/proliferative lens epithelial cells (bladder cells or pearls) mixed with lens cortical material. CONCLUSION Piggyback PC IOLs were explanted in 2 cases because of a newly described complication, interlenticular opacification. Three surgical means may help prevent this complication: meticulous cortical cleanup, especially in the equatorial region; creation of a relatively large continuous curvilinear capsulorhexis to sequester retained cells peripheral to the IOL optic within the equatorial fornix; insertion of the posterior IOL in the capsular bag and the anterior IOL in the ciliary sulcus to isolate retained cells from the interlenticular space.

Update on fixation of rigid and foldable posterior chamber intraocular lenses. part II: choosing the correct haptic fixation and intraocular lens design to help eradicate posterior capsule opacification

PURPOSE Posterior capsule opacification (PCO) is one of the most common complications of cataract surgery, and there is an urgent need to reduce its incidence. Its main treatment, neodymium:YAG (Nd:YAG) laser posterior capsulotomy, may be associated with significant morbidity and is expensive. In this study, the authors ascertain the effect of posterior chamber intraocular lens (PC-IOL) fixation and various IOL designs (rigid polymethyl methacrylate [PMMA] optic and small-incision foldable designs) on the pathogenesis of PCO. DESIGN Prospective analysis of pseudophakic eyes obtained postmortem. PARTICIPANTS A total of 3493 eyes with PC-IOLs obtained postmortem and received between 1984 and 1998. METHODS Miyake-Apple posterior photographic technique. MAIN OUTCOME MEASURES Peripheral Soemmerings ring, central PCO in the visual axis, and eyes that have had Nd:YAG laser posterior capsulotomy were analyzed and scored, and these findings were correlated with the type of fixation and IOL design. RESULTS The degree of formation of peripheral Soemmerings ring was not influenced by IOL fixation. The acrylic design revealed relatively low Soemmerings ring scores. In contrast, central PCO and Nd:YAG laser capsulotomy scores were consistently influenced by fixation. The scores were significantly lower in eyes with in-the-bag fixation. The bag-bag fixated acrylic-PMMA design and the three modern silicone IOL designs analyzed in this study had less central PCO and lower posterior capsulotomy scores than did the PMMA IOLs. CONCLUSIONS The formation of peripheral PCO (the Soemmerings ring), the precursor of clinically significant, vision-threatening PCO, is not significantly influenced by the haptic fixation pattern. It is much more dependent on the quality and thoroughness of surgical cortical cleanup. Reduction of Soemmerings ring is an important goal because the retained regenerative cortical cells within this lesion are the cells of origin of PCO. The acrylic IOL design was associated with a lessor amount of peripheral Soemmerings ring as compared with all other designs. In sharp contrast to peripheral PCO, fixation of the IOL was a highly significant factor affecting the formation and quantity of central PCO-the clinically significant opacity behind the IOL optic, measured in this series either by scoring an intact retro-optical membrane or by documenting the presence of a Nd:YAG laser posterior capsulotomy orifice. The quantity of central PCO was consistently much lower in eyes with in-the-bag fixated IOLs compared with lenses with one or both haptics out of the bag. This is best explained by the fact that secure in-the-bag fixation positions the IOL optic in the best possible position to create a barrier effect. The lowest PCO rates were generally noted with the acrylic and modern silicone IOL designs.

Silicone oil adhesion to intraocular lenses: An experimental study comparing various biomaterials

Purpose: To perform an in vitro experimental study comparing the degree of adherence of silicone oil to various rigid and foldable intraocular lens (IOL) designs and to the human lens capsule. Setting: Center for Research on Ocular Therapeutics and Biodevices, Department of Ophthalmology, Storm Eye Institute, Medical University of South Carolina, Charleston, South Carolina, USA. Methods: Seven IOL styles comprising various biomaterials were studied: fluorinetreated (FIuoriens™), heparin‐surface‐modified (HSM™), hydrogel, Memory‐Lens™, poly(methyl methacrylate) (PMMA), soft acrylic, and silicone lenses; the human crystalline lens was also studied. Each lens was immersed in silicone oil for 12 hours, then photographed, studied by scanning electron microscopy (except the crystalline lens), and subjected to computer‐generated image analysis to determine the silicone oil coverage. Results: Silicone oil coverage of dry silicone lenses was 100% and of lenses immersed in normal saline, 82.5%. The least coverage was on the heparin‐surfacemodified lens (mean score 9.4%). Coverage of the other four lenses ranged from approximately 15.1% to 33.7%. Mean coverage of the human lens capsule was 10.9%. Conclusion: Although a silicone IOL shows maximal adherence to silicone oil, other lens biomaterials are not immune to this complication. Silicone oil coverage was related to the dispersive energy component of the surface charge of the IOL biomaterial. Low dispersive energy materials had less silicone oil coverage, while those with higher dispersive energy had more oil coverage.

Update on fixation of rigid and foldable posterior chamber intraocular lenses. Part I: Elimination of fixation-induced decentration to achieve precise optical correction and visual rehabilitation.

PURPOSE Realizing that precise posterior chamber intraocular lens (PC-IOL) centration is needed to consistently achieve good optical results and visual rehabilitation after modern cataract surgery, the authors assessed the status and success rate of lens haptic fixation and its correlation with lens optic centration-decentration in a large series of eyes with PC-IOLs obtained postmortem. DESIGN Prospective analysis of pseudophakic eyes obtained postmortem. PARTICIPANTS A total of 3493 human eyes obtained postmortem, the largest database of such specimens available to date. METHODS Miyake-Apple posterior photographic technique. MAIN OUTCOME MEASURES The amount of decentration of rigid PC-IOLs and small-incision foldable PC-IOLs was analyzed, and the results were correlated with the type of fixation that had been achieved in each case. RESULTS Determination of mean values revealed that capsular bag fixation was achieved in 52.05% of eyes, asymmetric bag-sulcus fixation in 34.21 % of eyes, and sulcus-sulcus fixation in 13.74% of eyes. Asymmetrically fixed lenses consistently showed significant decentration. During the past 5 years (1993-98), the overall rate of in-the-bag fixation increased to 59.2%; by 1998 it had increased to 64%. Most significantly, success in achieving bag-bag fixation of foldable IOLs implanted in association with modern capsular surgery with small incisions has surged to 90% over the past 4 years. CONCLUSIONS The authors found a direct correlation of decentration in eyes with asymmetric fixation, and the results underscore the need for careful in-the-bag haptic placement. Although few surgeons today would dispute the goal to implanting haptics in the capsular bag, these findings show that the overall success rate over the years has, while improving, remained surprisingly low. The overall success rate of about 60% seen with all lens designs is probably as good as can be expected with classic large-incision extracapsular techniques. However, and most important and encouraging, the success rate of haptic fixation in cases with foldable lenses has improved dramatically during the past 4 years (up to the 90% range). This coincides with the present emphasis on modern capsular surgery and small-incision techniques used to insert these lenses.

Evaluation of neodymium:yttrium-aluminum-garnet capsulotomies in eyes implanted with AcrySof intraocular lenses

PURPOSE As of December 31, 2000, the neodymium:yttrium-aluminum-garnet (Nd:YAG) laser posterior capsulotomy rate for the Alcon AcrySof intraocular lens (IOL) as measured in our database was 3.3%. This was the lowest of any IOL model used in the United States. Only 12 of 361 cases required treatment. We analyzed possible surgical reasons that may have been responsible for the posterior capsule opacification (PCO) in this small group. Special attention was given to the three surgical factors that we had previously identified as being important for PCO reduction: (1) quality of cortical clean up, (2) type of haptic fixation, and (3) continuous curvilinear capsulorhexis (CCC) size and shape. DESIGN Comparative autopsy tissue analysis. PARTICIPANTS Three hundred sixty-one human eyes obtained postmortem with Alcon AcrySof IOLs, accessioned between January 1995 and December 2000 from Lions Eye Banks. METHODS The eyes were evaluated by the Miyake-Apple posterior photographic technique. MAIN OUTCOME MEASURES The area and intensity of Soemmerings ring and type of fixation were studied in 361 eyes. The size and shape of the CCC and relation of the CCC edge to the IOLs optic rim were analyzed in 168 eyes. RESULTS The amount of Soemmerings ring formation was significantly larger in the group of IOLs requiring Nd:YAG capsulotomy (Nd:YAG group). The not in-the-bag fixated IOLs required more Nd:YAG capsulotomies. Although the trend was clear, the number of specimens was not large enough to acquire statistical significance. The Nd:YAG group showed a highly significant difference compared with the No Nd:YAG group with regard to the amount of clock hours of the CCC edge on the optic rims surface (P < 0.001). Mean CCC diameters were significantly larger in the Nd:YAG group (P < 0.05). CONCLUSIONS The amount of Soemmerings ring correlates with the quality of cortical clean up. Cells within the Soemmerings ring are the direct precursors of PCO. This study confirms our previous laboratory studies and the clinical assumption that the incidence of PCO and thus the need for Nd:YAG capsulotomy is correlated with the cortical clean up. A second clinical assumption, that poor IOL fixation increases the risk of PCO, is also strongly suggested in this study. This study also verifies the relation of the CCC to PCO and the Nd:YAG laser, namely that a relatively small CCC without tears is best to prevent this complication. Use of a high-quality IOL combined with diligent attention to these three surgical factors should lower further the incidence of PCO.

Snowflake degeneration of polymethyl methacrylate posterior chamber intraocular lens optic material: A newly described clinical condition caused by unexpected late opacification of polymethyl methacrylate

OBJECTIVE To report 25 cases of gradual, but sometimes progressive, late-postoperative degeneration of polymethyl methacrylate (PMMA) optics of posterior chamber (PC) intraocular lens (IOL) implants, often resulting in a clinically significant visual decrease long after the implantation, sometimes to a severity that required IOL explantation/exchange. DESIGN Analysis of explanted PC IOLs, clinical histories, and photographs. PARTICIPANTS We analyzed 25 case histories/photographs and/or explants from 18 patients implanted in the 1980s to mid-1990s with three-piece PC IOLs with PMMA optics and with polypropylene or PMMA haptics. The IOL optic from each case had characteristic snowflake or crystalline opacifications. This condition occurred with more than one manufacturer and in some cases was restricted to certain lot numbers. METHODS The explanted IOLs (n = 10) were studied by gross inspection and by light and scanning electron microscopy, as well as confocal and energy dispersive spectroscopy. MAIN OUTCOME MEASURES The snowflake lesions were noted within the IOL optics. The nature of these lesions was investigated. RESULTS Assimilation of clinical information with pathologic and morphologic profiles of all cases suggested that the snowflake opacification was a small spherical lesion surrounded by an outer pseudocapsule composed of compressed, degenerated PMMA, with a central core containing convoluted fragments of PMMA. The lesions were classified into four clinical and pathologic grades according to their density and severity. CONCLUSIONS This is the first clinicopathologic correlative report on this complication. We postulate that manufacturing variations in some IOL models fabricated in the 1980s and early 1990s are responsible. The snowflake lesions seem to represent a destruction of the PMMA material. The cluster of lesions in implanted lenses manufactured by Surgidev was less progressive than some other models, including lenses made by IOPTEX Research Corporation. This identification of a condition previously unreported is important to alert clinicians regarding these perplexing lesions that may otherwise be considered idiopathic, with no obvious clinical hint as to their origin. The prevalence noted thus far is still too low to in any way suggest that this condition would occur in 100% of PMMA IOLs from these manufacturers. However, these late-occurring lesions, present in lens models that were implanted in hundreds of thousands of patients in the last decade or so, could have constituted a true epidemic, except that many of the patients are now deceased.

Effect of surface photorefractive keratectomy and laser in situ keratomileusis on the corneal endothelium

Purpose: To investigate endothelial cell loss in pairs of fresh human autopsy globes following high‐diopter myopic photorefractive keratectomy (PRK) or laser in situ keratomileusis (LASIK). Setting: Center for Research on Ocular Therapeutics and Biodevices and Magill Laser Center for Vision Correction, Storm Eye Institute, Charleston, South Carolina, USA. Methods: In the first part of the study, 12 globes had either ‐10 diopter (D) multizone surface PRK or ‐10 D single‐zone LASIK. In the second part, three groups of 5 globes each had ‐15 D, ‐20 D, or ‐25 D multizone‐blend LASIK procedures. Fellow globes in both groups were used as untreated controls. Comeoscleral buttons were excised from all globes. Following 7 days in corneal organ culture, the endothelial surface was stained with two vital dyes: calcein‐AM and ethidium homodimer. Fluorescence microscopy was used to obtain endothelial cell counts. Results: The mean dead cells per square millimeter (cells/mm2) were 0.94 in the ‐10 D PRK treated corneas compared with 0.91 in the fellow untreated eyes (P = 0.06). The mean dead cells/mm2 in the ‐10 D single‐zone LASIK‐treated corneas and in the fellow untreated eyes were 0.61 (P = 0.88). The mean dead cells/mm2 in the ‐15 D, ‐20 D, and ‐25 D multizone‐blend LASIK‐treated corneas were 3.08, 2.33, and 5.55, respectively, compared with 3.49, 1.92, and 5.01 in the fellow untreated eyes (P = 0.276, P = 0.339, and P = 0.427, respectively). Dead cell counts for treated and control paired corneas were highly correlated in all treatment groups. Conclusions: No significant endothelial cell loss occurred after ‐10 D PRK or LASIK corrections up to ‐25 D. Although this study has limitations that prevent direct extrapolation to the clinical situation, it does afford a comparable clinical correlate for endothelial cell toxicity following typical excimer laser ablations.