Effect of cataract surgery and pupil dilation on iris pattern recognition for personal authentication.

PURPOSE: The purpose of this study was to investigate the effect of cataract surgery and pupil dilation on iris pattern recognition for personal authentication. METHODS: Prospective non-comparative cohort study. Images of 15 subjects were captured before (enrolment), and 5, 10, and 15 min after instillation of mydriatics before routine cataract surgery. After cataract surgery, images were captured 2 weeks thereafter. Enrolled and test images (after pupillary dilation and after cataract surgery) were segmented to extract the iris. This was then unwrapped onto a rectangular format for normalization and a novel method using the Discrete Cosine Transform was applied to encode the image into binary bits. The numerical difference between two iris codes (Hamming distance, HD) was calculated. The HD between identification and enrolment codes was used as a score and was compared with a confidence threshold for specific equipment, giving a match or non-match result. The Correct Recognition Rate (CRR) and Equal Error Rates (EERs) were calculated to analyse overall system performance. RESULTS: After cataract surgery, perfect identification and verification was achieved, with zero false acceptance rate, zero false rejection rate, and zero EER. After pupillary dilation, non-elastic deformation occurs and a CRR of 86.67% and EER of 9.33% were obtained. CONCLUSIONS: Conventional circle-based localization methods are inadequate. Matching reliability decreases considerably with increase in pupillary dilation. Cataract surgery has no effect on iris pattern recognition, whereas pupil dilation may be used to defeat an iris-based authentication system.

Efficacy and safety of sedation with propofol in peribulbar anaesthesia.

PURPOSE: To evaluate the efficacy and safety of a sub-anaesthetic dose of propofol for reducing patient recall of peribulbar block in eye surgery. METHODS: A retrospective analysis of patients scheduled for elective cataract extraction or trabeculectomy using peribulbar anaesthesia with an intravenous bolus of propofol to provide sedation during the administration of the block. The dose of propofol was based on age and body weight. Patients' vital signs were monitored with continuous pulse oximetry and blood pressure measurements. Efficacy of sedation was assessed by recording patient's recall of the anaesthetic block after 8-10 min. RESULTS: Data from 2043 patients were analysed. The dose of propofol used ranged from 15-75 mg. Propofol was effective in abolishing recall in 87.5% of the patients studied. Only four patients required airway support but no major systemic side effects were encountered. CONCLUSIONS: A single sub-anaesthetic dose of propofol prior to administering peribulbar block is effective in reducing recall of the injection and safe without major systemic side effects.

Late surface opacification of Hydroview intraocular lenses.

PURPOSE: To describe clinical and pathological features of Hydroview intraocular lenses undergoing delayed surface opacification resulting in visual deterioration. METHODS: Twenty one eyes which underwent uncomplicated phacoemulsification and Hydroview lens implantation with good visual recovery, presenting at 46-146 weeks post-surgery with visual deterioration and glare symptoms resulting from opacification of the implants, were included in the study. Twelve eyes had severe opacification, of which nine underwent intraocular lens exchange and three more are still awaiting surgery. The method of explantation is described. The explanted intraocular lenses were examined using light microscopy, scanning electron microscopy and x-ray microanalysis using a light element detector. RESULTS: Light microscopy and scanning electron microscopy revealed diffuse granular deposits of approximately 5 microm diameter covering the optic surfaces but sparing the lens haptics. Light microscopic staining techniques and x-ray microanalysis confirm the major component of the deposits to be calcium phosphate salts. CONCLUSIONS: Late opacification of Hydroview intraocular lens implants is uncommon and aetiology seems to be multifactorial. Implant exchange is necessary to restore sight in some cases. As new materials are increasingly used it is important to highlight such unusual occurrences.

Clinical and pathologic findings in human keratolimbal allograft rejection.

OBJECTIVE: To characterize the clinical and pathologic features of cadaveric keratolimbal allograft (KLAL) rejection. DESIGN: The study design is descriptive. PARTICIPANTS: Four patients (five eyes) with KLAL rejection are reported. INTERVENTION: All patients were subjected to slit-lamp biomicroscopy, treatment of rejection, and ultimately required repeat KLAL surgery. In three patients (four eyes), specimens obtained at the time of repeat surgery were subjected to immunohistochemical staining against the following immune and surface human antigens: CD4, CD8, CD19, CD3, DR, CK19, CK3, and vimentin. RESULTS: Signs of allograft rejection included intense sectoral injection, diffuse or perilimbal conjunctival injection, edema, and infiltration of the KLAL grafts, leading to punctate epithelial erosions, epithelial defects, and surface keratinization. Rejected specimens revealed T-lymphocyte infiltration (CD4:CD8, 2:1) with strong HLA-DR (MHC class II) expression. The epithelium stain results were positive for cytokeratin 19 and weakly positive to absent for cytokeratin 3. The epithelial stain results were weakly positive for vimentin in only one specimen. CONCLUSIONS: KLAL rejection is a newly recognized entity. Pathologic findings of rejected specimens indicate that this is a T-cell mediated rejection phenomenon. The pattern of cytokeratin staining provided little evidence that the epithelium covering KLALs had a corneal phenotype. The scarcity of vimentin-positive epithelial cells suggests that the stem-cell/transient-cell pool was probably depleted. Early recognition of clinical rejection is important, as treatment with immunosuppressive therapy may reverse the process.

Photorefractive keratectomy for hyperopia: six months results in 45 eyes.

OBJECTIVE: To evaluate the safety and efficacy of photorefractive and photoastigmatic keratectomy for hyperopia. METHODS: The Chiron Keracor 116 excimer laser (Chiron Technolas, Munich, Germany) was used to create a peripheral annular ablation profile for the correction of hyperopia and a prior cylindrical ablation in the negative axis for correction of the astigmatic component in 45 consecutive eyes with up to +6.50 diopters (D). All patients were followed for a minimum of 6 months. RESULTS: At 6 months, mean subjective refraction was +0.12 D (standard deviation, 0.70), with 87% within 1 D of emmetropia. Ninety-three percent achieved uncorrected visual acuity of 20/40 or better. Three eyes (6.7%) lost 2 lines of best spectacle-corrected visual acuity and six eyes (13.3%) gained 2 lines or more. CONCLUSIONS: Photorefractive and photoastigmatic keratectomy effectively and predictably reduced hyperopia, improving uncorrected visual acuity in all patients at 6 months. Longer follow-up is required to be certain that refractive changes are stable.

Blow-out fracture of the orbit associated with inflation of an airbag: a case report.

We report a case of blow-out fracture of the orbit in a 37-year-old woman which was caused by deployment of an airbag following collision with a stationary vehicle whilst travelling at 30 m.p.h. The fracture did not become evident until she blew her nose some hours later. She was treated with antibiotics orally and made a full and complete recovery. Therefore, refinements in the design of airbags are warranted.

Long-term results and complications after trabeculectomy with a single per-operative application of 5-fluorouracil.

We retrospectively evaluated a consecutive series of 45 patients (45 eyes) who underwent trabeculectomy augmented with a single intra-operative 5 minute application of 5-fluorouracil (5-FU; 25 mg/ml). All patients were at an increased risk of subconjunctival fibrosis and surgical failure. The mean follow-up period was 24 months (range 12-42, SD 6.9). The mean pre-operative intraocular pressure (IOP) was 29.1 mmHg (SD 6.1) and the mean IOP at the last post-operative visit was 16.6 mmHg (SD 6.4) (p < 0.0001) with a mean IOP reduction of 42%. The number of medications reduced from a mean of 2.3 (SD 0.7) pre-operatively, to 0.8 (SD 0.7) post-operatively (p < 0.0001) and 22 eyes (49%) required no topical treatment for IOP control. An IOP of 21 mmHg or less with or without medications was achieved in 80% of cases. There was no significant difference in final IOP or success rate over time between low- and high-risk patients, although the low-risk patients did better in the first 12-18 months. Complications included hypotony maculopathy in 2 cases (4%), leaking bleb in 5 cases (11%) and giant bleb in 1 case (2%), giving a total of 8 cases (18%) with bleb-related sequelae. In the short to medium term, a single per-operative application of 5-FU is a useful adjunctive treatment during glaucoma filtering surgery for low- to moderate-risk cases, although a steady increase in the failure rate was associated with increasing length of follow-up.

Cracked cartridges during foldable intraocular lens implantation.

We describe five routine phacoemulsification procedures in which a longitudinal split in the injector cartridge occurred during foldable intraocular lens (IOL) implantation. In some cases, this was associated with a broken lens. All lenses (STAAR AA-4203VF) were folded, and implantation was attempted through a 3.5 mm corneal or scleral incision. Visual outcome was not adversely affected in any case. The systems for introducing foldable IOLs have not been perfected, and further refinements in materials and techniques are required.

Subconjunctival bupivacaine versus topical amethocaine in strabismus surgery.

A prospective study was performed to evaluate and compare the effect of subconjunctival bupivacaine and topical amethocaine on pain relief after strabismus surgery. A total of 40 children scheduled for elective operation were randomly allocated to receive either subconjunctival bupivacaine or topical amethocaine at the end of surgery. Post-operative pain was evaluated using a four-point assessment score. We show that both techniques provide good post-operative pain relief. We advocate that either could be used routinely in strabismus surgery although topical amethocaine is easier to administer.

Subconjunctival bupivacaine in strabismus surgery.

A prospective study was performed to assess the effect of subconjunctival bupivacaine on pain relief following strabismus surgery. A total of 36 children were randomly allocated to receive either subconjunctival infiltration of bupivacaine or normal saline at the conclusion of surgery. Post-operative pain was evaluated using a 4-point assessment score. Subconjunctival bupivacaine provided significantly better post-operative pain relief (P < 0.001). We suggest that it could be used routinely in strabismus surgery, as it improves post-operative comfort thereby facilitating day case surgery.