Milind V. Pande

Relationship between intraocular lens biomaterials and posterior capsule opacification

Purpose: To determine whether posterior capsule opacification (PCO) is influenced by intraocular lens (IOL) material. Setting: A British teaching hospital eye department. Methods: Ninety eyes were prospectively randomized to receive a poly(methyl methacrylate) (PMMA), silicone, or AcrySof® IOL. All lenses had 6,0 mm optics and PMMA haptics. A standardized surgical protocol was performed by a single surgeon using an extracapsular technique with capsulorhexis. Patients having surgical complications were excluded, and all patients had standardized medication and follow‐up. Posterior capsule opacification was assessed by a digital retroillumination camera using a dedicated software program based on the analysis of texture in the image and calculated as the percentage area of opacified capsule. Data were analyzed 2 years postoperatively. Results: There was a significant difference in percentage of PCO at 2 years among the three lens types (P < .0001). The AcrySof lenses were associated with less PCO (median 11.75%) than PMMA (43.65%) and silicone (33.50%) lenses (P < .001 and P = .025, respectively). The difference between PMMA and silicone lenses was not statistically significant. Conclusion: Intraocular lenses made from AcrySof were associated with a significantly reduced degree of PCO.

The effect of polymethylmethacrylate, silicone, and polyacrylic intraocular lenses on posterior capsular opacification 3 years after cataract surgery

OBJECTIVE To compare the visual outcome, neodymium:YAG (Nd:YAG) capsulotomy rates, and percentage of posterior capsular opacification (PCO) seen with polymethylmethacrylate (PMMA), silicone, and polyacrylic intraocular lens implants 3 years after surgery. DESIGN Randomized, prospective trial. PARTICIPANTS Ninety eyes of 81 patients were examined at a British teaching hospital. INTERVENTION Ninety eyes were prospectively randomized to receive a PMMA, silicone, or polyacrylic (AcrySof, Alcon, Fort Worth, TX) implant. All lenses had 6-mm disc optics with PMMA haptics. A standardized surgical protocol was performed by a single surgeon using an extracapsular technique with capsulorhexis; any surgical complications were excluded and all patients had standardized postoperative medication and follow-up. MAIN OUTCOME MEASURES Patients were seen at 6 months and 1, 2, and 3 years after surgery. At 3 years, logarithm of the minimum angle of resolution (LogMAR) visual acuity and Pelli-Robson contrast sensitivity were measured and YAG capsulotomy rates determined. Posterior capsular opacification was assessed objectively by digital retroillumination imaging using dedicated software and calculated as the percentage area of opacified capsule. RESULTS At 3 years, the overall follow-up rate was 71%: 19 patients were available for examination with polyacrylic lens implants, 22 with silicone, and 23 with PMMA. There was a significant difference in percentage PCO at 3 years among the lens types (P = 0.0001). Polyacrylic lenses were associated with less PCO (10%) than silicone (40%) and PMMA lenses (56%). The YAG capsulotomy rate was 0% for polyacrylic, 14% for silicone, and 26% for PMMA (P = 0.05). The visual acuity and contrast sensitivity were not significantly different among the three groups if patients with age-related macular degeneration and those requiring YAG capsulotomies are excluded. CONCLUSIONS Intraocular lenses made from polyacrylic are associated with a significantly reduced degree of PCO and lower YAG rates.

Biocompatibility of poly(methyl methacrylate), silicone, and AcrySof intraocular lenses: Randomized comparison of the cellular reaction on the anterior lens surface

Purpose: To determine the foreign‐body response to three intraocular lens (IOL) biomaterials (poly[methyl methacrylate] {PMMA], silicone, and AcrySof) and use this as an indicator of their comparative biocompatibility postoperatively within the eye. Setting: A British teaching hospital eye department. Methods: Ninety eyes were prospectively randomized to receive a PMMA, silicone, or AcrySof IOL. All lenses had 6.0 mm optics with PMMA haptics. A standardized surgical protocol was performed by a single surgeon using an extracapsular technique with`capsulorhexis; eyes that experienced a surgical complication were excluded. All patients had standardized postoperative medication and follow‐up. Specular microscopy of the anterior IOL surface was carried out after pupil dilation on days 1, 7, 30, 90, 180, 360, and 720 to assess small cell and giant cell reactions. Results: All three IOL types produced a mild degree’ of nonspecific foreign‐body response, which resolved over the study period without detrimental effect. The silicone group had significantly higher small cell counts than the PMMA and AcrySof groups (P = .02); the AcrySof group had significantly lower giant cell counts than the other two groups (P = .003). Conclusion: The three IOL types were sufficiently biocompatibfe to function in normal eyes with age‐related cataracts. However, AcrySof IOLs were associated with lower giant cell counts than PMMA and silicone IOLs and might produce better results in eyes with pre‐existing blood‐aqueous barrier damage.

Lens epithelial cell regression on the posterior capsule with different intraocular lens materials

BACKGROUND/AIMS Posterior capsular opacification (PCO) is caused by proliferation and migration of lens epithelial cells (LECs) across the posterior capsule and is the commonest cause of reduced vision after cataract surgery. The influence of intraocular lens (IOL) material on the process of LEC migration was studied. METHODS 90 eyes underwent standardised extracapsular surgery, with capsulorhexis and “in the bag” IOL placement. They were randomised to receive a three piece 6 mm lens of PMMA, silicone, or polyacrylic (AcrySof, Alcon, Fort Worth, TX, USA). On days 7, 30, 90, 180, and years 1 and 2 high resolution digitised retroillumination images were taken of the posterior capsule. The presence of LECs was determined at 90 days and 2 years, and their progression or regression was established by serial examination of images. RESULTS LECs were seen in 93% of silicone and 97% of PMMA IOLs at 90 days, compared with 46% of polyacrylic (p<0.001). At year 2 LECs were present in all patients with silicone or PMMA lenses, whereas 62% of patients with polyacrylic IOLs had LECs (p<0.001). Of those patients with LECs at day 90 LEC regression occurred in 8% with silicone IOLs and 15% of PMMA cases, compared with 83% of patients with polyacrylic IOLs (p<0.0001). CONCLUSION The presence of LECs on the posterior capsule was considerably lower with polyacrylic than PMMA or silicone IOLs and LEC regression occurred more frequently. The lower incidence of LECs and the higher rate of regression may explain why PCO formation appears to be reduced with polyacrylic lenses. This has important clinical implications for the prevention of PCO.

An In Vivo Investigation of the Structures Responsible for Corneal Haze after Photorefractive Keratectomy and Their Effect on Visual function

PURPOSE To make serial measurements of corneal haze and microscopic anatomy after photorefractive keratectomy (PRK) and compare the results with visual function measured at the same time points in the same single group of human subjects. METHODS Ten patients underwent -6.00-diopter, 6-mm PRK. The patients were reviewed frequently for 12 months. Corneal haze was measured objectively in two ways: (1) an opacification index was determined from the variance in digitized retroillumination images; and (2) light reflected and scattered back from the cornea was assessed by gray-scale analysis of video slit images. In vivo confocal microscopy recorded the anatomic changes occurring in the cornea, and computer analysis of the images quantified the keratocytes and subepithelial deposit. Visual performance was assessed by Snellen visual acuity, contrast sensitivity, and glare-induced visual dysfunction. RESULTS In the first week, epithelial irregularity resulted in a transient reduction in all aspects of visual function. In the first month, keratocyte disturbances reduced contrast sensitivity at high frequencies and produced glare. Over the next couple of months, the subepithelial deposit resulted in a more prolonged loss of contrast sensitivity at low frequencies and glare-induced visual dysfunction due to the scattering of light. In several patients, these visual defects persisted after 1 year. CONCLUSIONS Epithelial and keratocyte disturbances only transiently affect visual function. The subepithelial deposit is more persistent and can have a lasting effect on visual performance. Therefore, attempts to improve the visual outcome of PRK must be aimed at controlling the synthesis of subepithelial material.

Postoperative inflammatory response to phacoemulsification and extracapsular cataract surgery: Aqueous flare and cells

Purpose: To compare the postoperative blood‐aqueous barrier (BAB) breakdown induced by phacoemulsification with continuous curvilinear capsulorhexis (CCC) and by extracapsular cataract extraction (ECCE) with a linear capsulotomy. Setting: Cataract and Refractive Surgery Research Unit, Department of Ophthalmology, St. Thomas’ Hospital, London, United Kingdom. Methods: Anterior chamber flare and cells were measured preoperatively and 1 day, 1 week, and 1 and 3 months postoperatively in two parallel groups of 31 consecutive cataractous eyes. In Group 1, one surgeon performed ECCE with a linear capsulotomy; in Group 2, a second surgeon performed divide and conquer phacoemulsification with CCC. The preoperative, intraoperative, and postoperative medication regimen was the same in both groups. Results: Group 2 eyes had significantly lower anterior chamber flare and cell measurements in the first postoperative month than Group 1 eyes (.01 < P < .00001). Conclusions: Phacoemulsification with CCC induced a less severe BAB breakdown than ECCE with a linear capsulotomy. Phacoemulsification with CCC may be preferable in high‐risk eyes such as those with glaucoma, diabetes, or uveitis, which are prone to complications resulting from postoperative BAB breakdown.

Anterior capsule stability in eyes with intraocular lenses made of poly(methyl methacrylate), silicone, and AcrySof

Purpose: To ascertain whether the movement of the anterior capsule is different with intraocular lenses (IOLs) made from different materials. Setting: Department of Ophthalmology, St. Thomas’ Hospital, London, United Kingdom. Methods: Ninety patients had standardized extracapsular cataract extraction, continuous curvilinear capsulorhexis (CCC), and confirmed in‐the‐bag IOL placement performed by the same surgeon. Patients were randomized to receive a threepiece, 6.0 mm IOL made of poly(methyl methacrylate) (PMMA), silicone, or AcrySof®, all with PMMA haptics, and received standardized postoperative medication. Except for material, the IOLs were of the same design. On days 7, 30, 90, 180, and 360, digitized retroillumination images were taken of the IOL. The movement of the anterior capsule between each visit was analyzed. Results: The amount of anterior capsule movement was significantly less in the AcrySof lens group than in the PMMA or silicone lens groups in the first year after surgery (P = .0001). Conclusion: The AcrySof lens with PMMA haptics produced significantly less anterior capsule movement than PMMA or silicone lenses and thus is likely to cause less IOL decentration and capsular phimosis.

High-resolution digital retroillumination imaging of the posterior lens capsule after cataract surgery

Purpose: To develop a system for high‐resolution imaging of the posterior lens capsule after intraocular lens surgery for objective assessment of posterior capsule opacification (PCO). Setting: Department of Cataract and Refractive Surgery, St. Thomas’ Hospital, London, United Kingdom. Methods: A system was developed that uses coaxial illumination and imaging based on Zeiss components with a digital camera directly linked to a computer for online image verification and image analysis. Results: The system produced high‐resolution digital images with even background illumination of sufficient quality to demonstrate progressive lens epithelial cell changes that are amenable to computer image analysis. Conclusion: This system produced excellent images for objective documentation and quantitative measurement of PCO.

In vivo human lens epithelial cell proliferation on the anterior surface of PMMA intraocular lenses

AIMS: To study in vivo human lens epithelial cell proliferation on the anterior surface of PMMA implants and its interaction with postoperative blood-aqueous barrier breakdown in eyes undergoing cataract surgery. METHODS: A prospective study was carried out on three consecutive patient cohorts undergoing cataract surgery with intraocular lens implantation using three different surgical techniques which produce different anatomical relations between the implant and lens capsule. Specular microscopy of the anterior implant surface was used to document the natural history, topography, and density of lens epithelial cells and the laser flare and cell meter were used to measure postoperative blood-aqueous barrier breakdown. RESULTS: All groups showed lens epithelial cell proliferation onto the anterior surface of PMMA implants. This was initiated by and restricted to the region of anterior capsule-implant contact and decreased with the onset of anterior capsular opacification. Significant correlation was found in all groups between lens epithelial cell proliferation and postoperative blood-aqueous barrier breakdown. CONCLUSIONS: Human lens epithelial cell behaviour on PMMA surfaces in vivo differs from that seen in culture studies. Humoral factors in the aqueous, biomaterial properties of the implant, and its anatomical relations with the anterior and posterior lens capsule influence lens epithelial cell behaviour in vivo.

Continuous curvilinear capsulorhexis and intraocular lens biocompatibility

Purpose: To study the influence of continuous curvilinear capsulorhexis (CCC) on poly(methyl methacrylate) (PMMA) intraocular lens (IOL) biocompatibility. Methods: Biocompatibility was assessed by measuring the postoperative bloodaqueous barrier breakdown and the cellular reaction at the anterior capsule‐IOL interface. In a prospective study, 30 consecutive eyes, normal except for having extracapsular cataract extraction (ECCE) with CCC by a single surgeon, had laser flare and cell measurements and specular microscopy of the anterior IOL surface at 1 day, 1 week, and 1 and 3 months postoperatively. Results: In addition to the foreign‐body reaction previously described in eyes that had other capsulotomy types, the eyes in this study also had a lens epithelial cell (LEC) reaction. The severity of the foreign‐body reaction and postoperative aqueous flare and cells was significantly less in eyes with an intact CCC than in those with rim tears in the capsulorhexis and in those having an ECCE with a linear or can‐opener capsulotomy, as previously reported. Conclusions: Continuous curvilinear capsulorhexis improves the biocompatibility of PMMA IOLs to a degree that could be of clinical benefit. In eyes with CCC, most cells seen on the anterior IOL surface were LECs.