William R. Meacock

Double-masked prospective ocular safety study of a lens epithelial cell antibody to prevent posterior capsule opacification

PURPOSE To evaluate the intraocular safety of an immunoconjugate (MDX-RA) developed to prevent posterior capsule opacification (PCO) in human eyes. SETTING St. Thomass Hospital Eye Department, London, United Kingdom. METHODS Twenty-six patients had phacoemulsification and implantation of an intraocular lens (IOL). All were randomly allocated at the end of surgery to receive a 0.1 mL placebo or 0.1 mL of the immunotoxin MDX-RA intracamerally. Two doses of the drug were tested: 8 patients with a low dose (50 units), 9 patients with a high dose (100 units), and 9 with placebo. Follow-up at days 1, 14, 30, 60, 90, and 180 consisted of visual acuity measured by the Early Treatment of Diabetic Retinopathy Study test, contrast sensitivity, aqueous flare, specular microscopy of the IOLs anterior surface, and corneal endothelial counts. The percentage area of PCO was measured from retroillumination images of the posterior capsule. RESULTS There was no decrease in corneal endothelial cell count in toxin-treated patients. Early postoperative flare, anterior chamber cell count, and corneal pachymetry were higher in toxin-treated patients. The median percentage area of PCO at 1 year was 32.0 in the placebo group, 3.8 in the low-dose group, and 7.4 in the high-dose group (P = .06). CONCLUSION This prospective, randomized, placebo-controlled trial confirmed that MDX-RA is safe for intraocular use and is of potential value for further clinical trials of the prevention of PCO.

Effect of 1-piece and 3-piece AcrySof intraocular lenses on the development of posterior capsule opacification after cataract surgery

Purpose: To evaluate the effect of 1‐piece and 3‐piece hydrophobic acrylic intraocular lenses (IOLs) on posterior capsule opacification (PCO) after cataract surgery. Setting: Ophthalmology departments of 3 hospitals in the United Kingdom and Germany and the Department of Physics at a United Kingdom university. Methods: A series of 131 patients having cataract surgery had implantation of an acrylic 1‐piece (SA30AL) or an acrylic 3‐piece (MA30BA) IOL (AcrySof®, Alcon). Surgery was performed according to standardized protocol by a single surgeon at each hospital. Posterior capsule opacification was assessed using digital retroillumination photography. All images were analyzed at a single center according to a standard protocol. Data were analyzed 6 months and 1 year after surgery. Results: There was no statistically significant difference in the percentage area of PCO between the 1‐piece (mean 16.0% ± 15.7% [SD]) and 3‐piece (mean 13.6% ± 19.8%) cohorts 6 months and 1 year after surgery (P = .0664). Conclusion: There was no evidence of a difference in the area of PCO after cataract surgery between 1‐piece and 3‐piece IOLs, which were otherwise matched for material and lens geometry.

The Effect of Polymethylmethacrylate and AcrySof Intraocular Lenses on the Posterior Capsule in Patients with a Large Capsulorrhexis

PURPOSE We have previously shown that patients who have a capsulorrhexis larger than the diameter of a polymethylmethacrylate (PMMA) intraocular lens (IOL) rapidly develop increased posterior capsule opacification (PCO), in effect, producing an example of enhanced PCO. This study focuses on the influence of AcrySof IOLs on this process. METHODS Phacoemulsification was performed on two groups of patients. The first consisted of 38 patients with a large capsulorrhexis of 6-7 mm who received a 5.5-mm PMMA IOL. The second group of 32 patients had identical surgery and a 5.5-mm MA30 AcrySof IOL was implanted. On days 1,14, 28, 90, 180, and 360, high resolution digitized retroillumination images were taken of the posterior capsule. The PCO area was measured by image analysis at 90, 180, and 360 days. Wrinkling of the posterior capsule was determined at 90 days, and the progression or regression of lens epithelial cell (LEC) proliferation was established by examination of serial images at 28 and 180 days. RESULTS At 90 days, 79% of the patients with PMMA IOLs had moderate to severe wrinkling of the posterior capsule, whereas the patients with AcrySof IOLs had none (P <.001). The percentage of PCO area was 69% for the PMMA IOLs and 24% for the AcrySof IOL group at 360 days (P <.0001). In the PMMA group, LEC progression occurred in 77%, LEC growth was stable in 15%, and LEC regression occurred in only 8%, compared to 69% of patients with AcrySof IOLs (P <.0001). CONCLUSIONS In patients with a rhexis larger than the IOL, AcrySof IOLs potentially can prevent capsular wrinkling and cause less PCO than a PMMA IOL with a similar rhexis size. The LEC regression occurs with AcrySof between 28 and 180 days. The reasons for this are discussed.

Effect of intraocular lens haptic compressibility on the posterior lens capsule after cataract surgery.

Purpose: To evaluate the effect of intraocular lens (IOL) haptic compressibility on the posterior capsule after cataract surgery. Setting: Teaching hospital, London, United Kingdom. Methods: In this randomized prospective study, 60 patients had standardized phacoemulsification with in‐the‐bag placement of a poly(methyl methacrylate) (PMMA) (Storz P497UV) or hydrogel (Storz Hydroview H60M) IOL. Both IOLs had PMMA haptics of identical configuration and length. The IOL haptic compressibility was measured in air and then during incubation in saline at 37°C over 1 month. Digital retroillumination imaging was performed 1, 7, 28, 90, 180, 360, and 720 days postoperatively. The presence and duration of postoperative capsule folds were recorded and correlated with the haptic compressibility measurements, lens epithelial cell (LEC) growth patterns on the posterior capsule at 6 months, and the extent of posterior capsule opacification. Results: On the first postoperative day, 21 patients (88%) in the Hydroview group had posterior capsule folds that persisted in 12 patients (50%) for 2 years. Nineteen patients (68%) in the PMMA group had folds at day 1 (P = .01), with 1 patient (3%) still having folds at 1 month (P = .0002) and no patient having folds at 3 months. At 6 months, 11 patients (46%) in the Hydroview group and no patient in the PMMA group had LEC growth in the direction of the folds. The PMMA IOLs showed a greater decrease in haptic compressibility during incubation. Conclusions: Haptic compressibility should be an important consideration in IOL design. The results suggest that to avoid posterior capsule folds, the compressibility should be less than 2.5 mN.

Automatic quantification of posterior capsule opacification

After Cataract surgery where a plastic implant lens is implanted into the eye to replace the natural lens, many patients suffer from cell growth across a membrane situated at the back of the lens which degrades their vision. The cell growth is known as Posterior Capsule Opacification (or PCO). It is important to be able to quantify PCO so that the effect of different implant lens types and surgical techniques may be evaluated. Initial results obtained using a neural network to detect PCO from implant lenses are compared to an established but less automated method of detection, which segments the images using texture segmentation in conjunction with co- occurrence matrices. Tests show that the established method performs well in clinical validation and repeatability trials. The requirement to use a neural network to analyze the implant lens images evolved from the analysis of over 1000 images using the established co-occurrence matrix segmentation method. The work shows that a method based on neural networks is a promising tool to automate the procedure of calculating PCO.