Hard Lenses Research Articles

A novel approach to remove retained lens material: Suction-assisted elevation and anterior chamber phacoemulsification.

To describe and evaluate the feasibility of a novel pars plana vitrectomy (PPV) technique for the removal of retained lens material (RLM), which obviates the need for either 20-gauge intravitreal fragmentation or perfluorocarbon-assisted elevation. Interventional case series. After thorough 23-gauge PPV, the hard lens material is engaged and held adherent to the vitreous cutter using aspiration, then raised into the anterior chamber. There, a standard phacoemulsification probe, inserted through a corneal incision, is used to fragment and remove the material. Three eyes of 3 patients were operated on. In all eyes, RLM could be removed completely. Postoperatively, 2 of 3 eyes (67%) achieved 20/20 best-corrected visual acuity. No complications such as glaucoma, cystoid macular edema, corneal edema, or retinal detachments were recorded. Intraoperatively, retinal tears were detected in 2 of 3 (67%) eyes and treated with endolaser retinopexy and fluid-air exchange. One eye subsequently developed macular hole requiring further surgery. Suction-assisted lens elevation may be a viable and convenient technique to remove RLM during PPV. Although the comparison with other methods is beyond the scope of this preliminary study, visual outcomes and complication rates were encouraging and should be validated in a larger group of patients.

The optical possibilities of gelatin

Contact lenses have traditionally been manufactured using a variety of plastics: polymers for soft lenses and acrylic or polymethyl methacrylate for hard lenses. There is emerging interest in the use of gelatin for lenses to increase malleability, water solubility, and sustainability as a non-plastic. A predicted difficulty in the use of gelatin is the reduced refractive index (RI). We looked at how acrylic or gelatin changes the RI and focal length in order to see how gelatin lenses would have to be altered for more severe prescriptions. We tested the refractive rays of gelatin and acrylic with both convex and concave lens types to investigate which produced smaller angles of refraction and correspondingly greater focal length. The average RI of the biconvex and biconcave acrylic without Pam, acrylic with Pam, and gelatin were 1.47, 1.496 and 1.36, respectively. Gelatin’s lesser angles of refraction produced a longer focal length. The lower RI of the gelatin (0.11–0.136 less than acrylic) directly correlated with its lesser angles of refraction, which produced an overall greater focal length (3.51– 4.38 more than acrylic). Gelatin needs to be thickened, increased in curvature, or mixed with crosslinkers to strengthen the lens. Lens makers will face similar challenges with the switch to gelatin lenses, so they may need to incorporate a larger percentage of solid gelatin concentrate or a plastic alloy in the gelatin to increase the RI, decrease the focal length, and improve the stability of the gelatin.

Equationof state of hard lenses: A combined virial series and simulation approach.

We provide highly accurate equation-of-state data for the isotropic phase of hard lenses obtained by means of cluster Monte Carlo simulations. This data is analyzed using a virial approach considering coefficients up to the order eight and Carnahan-Starling type closure relations for the virial series. The comparison with previously investigated systems consisting of hard, oblate ellipsoids of revolution allows insights into the detailed influence of the particle geometry. We propose a generalized Carnahan-Starling approach as a heuristic equationof state for the isotropic phase of hard lenses that in first approximation shows the same dependence on the excess part of the excluded volume as identified for oblate, hard lenses of revolution.

EphA2 Affects Development of the Eye Lens Nucleus and the Gradient of Refractive Index.

PurposeOur studies in mouse eye lenses demonstrate that ephrin-A5 and EphA2 are needed for normal epithelial cells and lens transparency. We sought to determine whether EphA2 and ephrin-A5 are important for lens morphometrics, nucleus formation, and refractive index.MethodsWe performed tissue morphometric measurements, electron microscopy, Western blots, and interferometric measurements using an X-ray synchrotron beam source to measure the gradient of refractive index (GRIN) to compare mouse lenses with genetic disruption of EphA2 or ephrin-A5.ResultsMorphometric analysis revealed that although there is no change in the overall lens volume, there is a change in lens shape in both EphA2−/− lenses and ephrin-A5−/− lenses. Surprisingly, EphA2−/− lenses had small and soft lens nuclei different from hard lens nuclei of control lenses. SEM images revealed changes in cell morphology of EphA2−/− fiber cells close to the center of the lens. Inner EphA2−/− lens fibers had more pronounced tongue-and-groove interdigitations and formed globular membrane morphology only in the deepest layers of the lens nucleus. We did not observe nuclear defects in ephrin-A5−/− lenses. There was an overall decrease in magnitude of refractive index across EphA2−/− lenses, which is most pronounced in the nucleus.ConclusionsThis work reveals that Eph-ephrin signaling plays a role in fiber cell maturation, nuclear compaction, and lens shape. Loss of EphA2 disrupts the nuclear compaction resulting in a small lens nucleus. Our data suggest that Eph-ephrin signaling may be required for fiber cell membrane reorganization and compaction and for establishing a normal GRIN.

Metamorphosis of Contact Lenses

In 1971, soft contact lenses were a striking addition to the ophthalmic field that related functionally to the existing hard contact lenses by correctingrefractive error, but their properties and description were different so as to confound ophthalmic professionals in their introduction. Their inventor Otto Wichterle, a Czechoslovakian chemist and anticommunist dissident, developed the soft lens in the 1950-60s with little knowledge of the hard lens, but its potential was broad enough to break through the communist barriers and to spark international consumer interest and development.Challenges in manufacturing and developing soft contact lenses created a complex discipline around the cornea and lid physiology, and optics. This expanded greatly the scientific knowledge of the eye and adnexa to allow a soft, hydrophilic lens to remain symbiotic with the eye. Challenges were met over the past 50 years with a change in nomenclature and in automated manufacturing closer to hard lenses, optical advancements, new materials and surface treatments, and lens disinfection methods. The science developing from the diminutive soft lens led to the incorporation of related biomedical and polymer science within the broader ophthalmic field that inordinately influenced optical advancements, instrumentation,and ocular pathology.

Calculation of third to eighth virial coefficients of hard lenses and hard, oblate ellipsoids of revolution employing an efficient algorithm.

We provide third to eighth virial coefficients of oblate, hard ellipsoids of revolution and hard lenses in dependence on their aspect ratio ν. Employing an algorithm optimized for hard anisotropic shapes, highly accurate data are accessible with comparatively small numerical effort. For both geometries, reduced virial coefficients B[over ̃]_{i}(ν)=B_{i}(ν)/B_{2}^{i-1}(ν) are in first approximation proportional to the inverse excess contribution α^{-1} of their excluded volume. The latter quantity is directly accessible from second virial coefficients and analytically known for convex bodies.

A vanishing brown lens: Interesting case findings!

Lens absorption has been reported to be associated with uveitis, downs syndrome, morgagnian cataract and trauma. However, spontaneous absorption of hard brown lens is a rare entity. The exact mechanism by which a lens undergoes spontaneous absorption despite an intact capsular bag is still unknown. Here we present a case of elderly female who presented to us with right eye hard brown cataract with ongoing process of getting absorbed and intact capsular bag.

Therapeutic Images of CT Image Analysis Based on 3D Visualization Technology in Patients with Hepatobiliary Stones

Objective: Paper for CT imaging in three-dimensional visualization technology for laparoscopy combined with biliary hard lens therapeutic clinical effect of extrahepatic bile duct stones were evaluated. Methods: Abdominal medical image 3D visualization software for our hospital CT imaging diagnosis and treatment of bile duct stones in 45 patients of bile duct stones three-dimensional visualization of clinical analysis and preoperative planning, and brought it into the operating room three-dimensional visualization model, guiding the implementation of the joint 3D laparoscopic biliary lithotripsy targeted hard lens. At the same time, as well as consistency with the actual hepatolithiasis distribution calculation operative 3D model visualization display; The operative time, bleeding, blood transfusion, stone clearance rate, morbidity and mortality perioperative after review stone recurrence rate was observed. Results: reproducing a three-dimensional patient model visualization liver, intrahepatic vascular anatomy of the liver bile duct stones distributed, real intraoperative and preoperative displayed three-dimensional visualization model consistent, pre-operative manner consistent with preoperative planning. Operation time (125.9±21.2) minutes, blood loss (38.8±8.5) ml, no massive hemorrhage and blood transfusion; MRCP examination by stone clearance rate was 100%; 2 biliary injury, bile leakage 1 complication the rate was 6.7%; There were no perioperative deaths. Stone recurrence two cases, the recurrence rate of 4.4%. Conclusion: The three-dimensional visualization techniques may be implemented hepatolithiasis accurate assessment of preoperative, intraoperative guidance of laparoscopic, endoscopic biliary hard gravel, stone liver resection operation, help to improve stone clearance rate, guarantee operation safety.

Topical anaesthesia plus intracameral lidocaine versus topical anaesthesia alone for phacoemulsification cataract surgery in adults.

Topical anaesthesia plus intracameral lidocaine versus topical anaesthesia alone for phacoemulsification cataract surgery in adults.

Bite Out Your Tongue

Bite Out Your Tongue

Managing dislocated hard lens nuclei: 23-gauge vitrectomy and lens extraction via a corneoscleral limbal incision versus 23-gauge vitrectomy and phacofragmentation

To compare 23-gauge vitrectomy and lens extraction viaa corneoscleral limbal incision (CSLI) with 23-gauge vitrectomy and phacofragmentation to treat dislocation of hard lens nuclei. Ningbo Eye Hospital, Zhejiang, China. Retrospective case series. The study included consecutive patients with complete posterior dislocation of a hard nucleus (grade≥IV) into the vitreous cavity. All patients received 23-gauge 3-channel vitrectomy. Some patients also had phacofragmentation and others had lens extraction through a CSLI. The CSLI group comprised 21 eyes of 21 patients and the phacofragmentation group, 22 eyes of 22 patients. The median follow-up was 10.8 months (range 6 to 24months)and 11.3months (range 5 to 18months), respectively. Demographic characteristics, reason for lens dislocation, preoperative corrected distance visual acuity (CDVA), preoperative intraocular pressure (IOP), lens nucleus grade, and comorbidities were similar between groups. The CSLI group had a shorter meansurgical time than thephacofragmentation group (42.5±7.2minutes versus 68.2±16.5minutes); less frequent use of perfluorocarbon liquid, octafluoropropane, or air tamponade; lower incidence of retinal tears (9.5% versus 31.8%); and better CDVA but worse astigmatism 1day and 1week postoperatively (P<.05). The postoperative IOP did not differ between groups. Corneal edema and recurrent retinal detachment were less common in the CSLI group than in the phacofragmentation group. The 23-gauge vitrectomy with lens extraction through a CSLI might have advantages over 23-gauge vitrectomy with phacofragmentation for management of dislocated hard lensnuclei.

Endothelial parameters in central and peripheral cornea in patients wearing contact lenses.

To measure the parameters of endothelium in the central and peripheral parts of the cornea and evaluate the influence of wearing the hard and soft contact lenses on the mentioned parameters. A specular microscope was used to measure the corneal endothelium parameters in both eyes of 139 Caucasians (a total of 278). All participants were divided into three groups: soft lens wearers, hard lens wearers and a control group. Factors, such as age, smoking, types of lens material, duration of lens wear and lens air permeability were assessed to determine their impact on the morphometric parameters of the endothelium. A lower percentage of hexagon-like cells and higher cell variation than in other groups were determined in hard contact lens wearers. The difference in density of endotheliocytes between the groups was not observed. The measurements of the morphometric parameters in soft contact lens wearers did not depend neither on the duration of lens wear, nor on air permeability. The relation between the patients' age and the variation of endothelium parameters was determined in the group of hard contact lens wearers. Wearing hard contact lenses provokes pleomorphism and polymegethism of the corneal endothelium, while soft contact lenses do not impact any parameters of the endothelium, most likely due to higher air permeability.

Nitinol basket-assisted pars plana vitrectomy for retained lens material removal.

To evaluate the usefulness of different types of nitinol baskets to capture, lift and hold the lens material, dropped during a complicated phacoemulsification, as an adjunctive surgical tool in vitreoretinal surgery and to evaluate the outcomes and complication of this new surgical technique in a small series of patients. Patients who underwent pars plana vitrectomy (PPV) for retained lens fragments operated during December 2014 and March 2015 at the Academic Medical Center (AMC), Amsterdam, were included in this study. The PPV was performed using different settings and types of nitinol stone extractors (NSE). Three different stone extractors were used for the above-mentioned purpose. Preoperative (pre-op) and postoperative (post-op) data including best corrected visual acuity at 6months follow-up visit, intra- and postoperative complications were recorded. Seven eyes of seven patients with a follow-up of 6months were included in this study. All the vitrectomies were performed the same day of the complicated cataract extraction. Mean pre-op Snellen visual acuity was 20/160; mean post-op visual acuity was 20/32. No complications were encountered due to the use of the NSE intraocularly. No retinal breaks were observed due to traction of the catheter at the site of insertion or due to his movement in and out the vitreous cavity. The use of the nitinol lens cage seemed feasible and showed no complications in our small group of patients. It made easier the management of dropped nucleus without the need for a larger scleral opening also in case of very hard lens.

Case study: An embedded contact lens

A recent story attracting widespread media attention reminded Dr Narendra Kumar of another case of a patient whose hard lens could not be removed

Cure kinetic study of methacrylate-POSS copolymers for ocular lens

The physical, mechanical and biological properties of multicomponent acrylate-based hard lenses are directly influenced by degree of conversion achieved during copolymerization. In this research, polyhedral oligomeric silsesquioxane (POSS) acrylate is introduced into the polymer backbone in combination with hydroxyethyl methacrylate, dimethyl itaconate, methyl methacrylate, 3-(trimethoxysilyl) propyl methacrylate and triethylene glycol dimethacrylate in free-radical bulk polymerization. Kinetics of curing process was investigated by two techniques: differential scanning calorimetry and FTIR spectroscopy. Reaction kinetics in free-radical bulk polymerization of the system was studied by isothermal DSC performed at 65, 75, 85, and 95 °C using different quantities of initiator. Three compounds were prepared in different concentrations (0.2, 0.4 and 0.6 mol%) of 2,2′-azobisisobutyronitrile as initiator. Conversion rate was calculated as a function of time using data obtained from DSC measurements. The kinetic parameters of the reaction such as reaction constants, reaction orders and activation energies were obtained from the isothermal DSC data according to the autocatalytic model developed by Kamal and Sourour. The results showed that the experimental values were in good agreement with theoretically estimated values and our results may suggest that the polymerization reaction of this system is well described by Kamal’s model. Cytotoxicity results, performed on extracts 28 days after PBS incubation, showed no toxicity of the materials extracted from the lenses indicating that they can be considered as safe materials in ocular lens applications. The viability and proliferation of L929 fibroblast cells in extracting media were followed by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) and they may have a great potential as ideal supporting lens in people who suffer from keratoconus disease.Graphical abstract

Folded bandage contact lens retention in a patient with bilateral dry eye symptoms: a case report

BackgroundBandage contact lenses are commonly used by ophthalmic practitioners to protect the patient’s cornea. We report a case of folded bandage contact lens retained for six and a half years in the upper subtarsal space. To our knowledge, no other cases of retained bandage contact lens have previously been reported in the literature.Case presentationA patient was applied a pair of bandage contact lenses due to persistent ocular pain secondary to dry eye symptoms. At her subsequent visit, bandage contact lens was removed from her left eye, but none was found in the right eye. Documentation from further visit stated that the bandage contact lenses were no longer in situ. 6.5 years since the lens insertion, lid eversion revealed a ‘foreign body’ retained beneath her right upper eyelid, which was noted to be a folded, discoloured bandage contact lens.ConclusionsThe ‘upper fornix trap’, where the contact lens may be retained by the upper tarsal edge, presents an anatomical hazard for contact lens users. Moreover, soft contact lenses may be more likely to retain asymptomatically and to fold onto itself compared to hard lenses. Our case report highlights the importance of performing a thorough eye examination, which includes double eversion of the upper eyelids and sweeping of the fornices with cotton buds, and maintaining clinical suspicion of contact lens retention.

Improvement of Phaco Tip Geometry During Torsional Phacoemulsification

Advanced cataract with hard lens nuclei frequently challenge the ophthalmologic surgeon when doing phacoemulsification. In the present study, we examined the effect of a new phaco tip design during cataract surgery. 100 patients were assigned to two groups. In group 1 (50 patients), the Kelman® tip design (Alcon) was used during phacoemulsification, while in group 2 (50 patients), the Intrepid® Balanced Tip was applied. Trypan blue was used in both groups, if necessary, to stain the anterior lens capsule prior to capsulorhexis. Preoperative visual acuity was 0.11 ± 0,16 (decimal equivalent; means ± standard deviation) in the Kelman tip group and 0.10 ± 0.14 in the Intrepid Balanced Tip group (p > 0,05). Applied cumulative displaced energy was 43.38 ± 21.84 s% in the Kelman tip group and 21.55 ± 13.25 s% in the Intrepid Balanced Tip group (p < 0,001). No intraoperative or postoperative complications occurred. The improved Intrepid Balanced phaco tip design has led to a significant reduction in ultrasound energy required to successfully perform phacoemulsification in medium to hard lenses.

Bacterial and Fungal Biofilm formation on Contact Lenses and their Susceptibility to Lens Care Solutions

Background: Microbial biofilm formation on contact lenses and lens storage cases may be a risk factor for contact lens-associated corneal infections. Various types of contact lens care solutions are used to reduce microbial growths on lenses. Objectives: The present study aimed at comparing the growths of biofilms on the different contact lenses and lens cases. The study also aimed at determining the effect of lens care solutions and bacteriophage on these biofilms. Materialsand Methods: One type of hard lens and two types of soft lenses were used for the study. The organisms used were Staphylococcus aureus ATCC 25923, Pseudomonas aeruginosa ATCC 27853, Candida albicans ATCC 60193 and Escherichia coli ATCC 25922. Biofilm production was performed by modified O’Toole and Kolter method and effect of lens cleaning solutions and a crude coliphage on biofilms was also studied. Results were visualised using scanning electron microscopy and quantitated by colony counting method and spectrophotometric measurement of optical density (OD). Statistical analysis was done by SPSS 11.5, Kruskal–Wallis test and Chi-square test. Results: Soft lens cleaning solutions had a significant inhibitory effect (P = 0.020) on biofilm formation on soft lenses and also lens cases (P < 0.001). Soft lens cleaning solution 2 was more efficient than solution 1. However, no such inhibitory effect was observed with regard to hard lens cleaning solution, but for a significant reduction in the OD values (P < 0.001). There was no significant inhibitory effect by bacteriophages. Conclusion: This study showed the importance of selecting the appropriate lens cleaning solution to prevent biofilm production on contact lenses.

聚甲基丙烯酸甲酯材质硬X射线组合Kinoform透镜的制作

聚甲基丙烯酸甲酯材质硬X射线组合Kinoform透镜的制作

Injection molded polymeric hard X-ray lenses

A novel and economical approach for fabricating compound refractive lenses for the purpose of focusing hard X-rays is described. A silicon master was manufactured by UV-lithography and deep reactive ion etching (DRIE). Sacrificial structures were utilized, which enabled accurate control of the etching profile and were removed after DRIE. By electroplating, an inverse nickel sample was obtained, which was used as a mold insert in a commercial polymer injection molding machine. A prototype lens made of polyethylene with a focal length of 350 mm was tested using synchrotron radiation at photon energies of 17 keV. A 55 µm long line focus with a minimal waist of 770 nm (FWHM) and a total lens transmittance of 32% were measured. Due to its suitability for cheap mass production, this highly efficient optics may find widespread use in hard X-ray instruments.