Haptic Compression Research Articles

Outcome of a New Acrylic Intraocular Lens Implantation in Pediatric Cataract.

To study the outcome of Hoya Clear Preloaded intraocular lens (IOL) (PC 60AD, AF Series; Hoya, Tokyo, Japan) implantation in children. Children who underwent phacoaspiration with primary posterior capsulotomy, anterior vitrectomy, and primary IOL implantation through a 2.8-mm incision were observed prospectively. In all cases, attempts were made to implant the IOL into the capsular bag. Parameters noted were ease of implantation, synechiae formation, IOL deposits, decentration of IOL, visual axis obscuration, haptic compression, and ovalling of the rhexis. Intraoperative complications related to the IOL were also recorded. This series comprised 58 eyes of 38 patients with congenital/developmental cataract who underwent implantation of the Hoya IOL. Mean age of the patients was 3.27 ± 2.69 years (range: 3 months to 8 years) and mean follow-up was 24.5 ± 9.13 months. Visual axis obscuration occurred in 4 eyes, posterior synechiae in 5 eyes, IOL deposits in 6 eyes, haptic compression in 3 eyes, and IOL decentration in 1 eye. The data suggest that implantation of the Hoya IOL is a safe option in children undergoing cataract surgery.

RGD surface functionalization of the hydrophilic acrylic intraocular lens material to control posterior capsular opacification.

Posterior Capsular Opacification (PCO) is the capsule fibrosis developed on implanted IntraOcular Lens (IOL) by the de-differentiation of Lens Epithelial Cells (LECs) undergoing Epithelial Mesenchymal Transition (EMT). Literature has shown that the incidence of PCO is multifactorial including the patient's age or disease, surgical technique, and IOL design and material. Reports comparing hydrophilic and hydrophobic acrylic IOLs have shown that the former has more severe PCO. On the other hand, we have previously demonstrated that the adhesion of LECs is favored on hydrophobic compared to hydrophilic materials. By combining these two facts and contemporary knowledge in PCO development via the EMT pathway, we propose a biomimetically inspired strategy to promote LEC adhesion without de-differentiation to reduce the risk of PCO development. By surface grafting of a cell adhesion molecule (RGD peptide) onto the conventional hydrophilic acrylic IOL material, the surface-functionalized IOL can be used to reconstitute a capsule-LEC-IOL sandwich structure, which has been considered to prevent PCO formation in literature. Our results show that the innovative biomaterial improves LEC adhesion, while also exhibiting similar optical (light transmittance, optical bench) and mechanical (haptic compression force, IOL injection force) properties compared to the starting material. In addition, compared to the hydrophobic IOL material, our bioactive biomaterial exhibits similar abilities in LEC adhesion, morphology maintenance, and EMT biomarker expression, which is the crucial pathway to induce PCO. The in vitro assays suggest that this biomaterial has the potential to reduce the risk factor of PCO development.

Perception-based lossy haptic compression considerations for velocity-based interactions

The ability of technology to transmit multi-media is very dependent on compression techniques. In particular lossy compression has been used in image compression (jpeg) audio compression (mp3) and video compression (mpg) to allow the transmission of audio and video over broadband network connections. Recently the sense of touch or haptics is becoming more important with its addition in computer games or in cruder applications such as vibrations in a cell phone. As haptic technology improves the ability to transmit compressed force sensations becomes more critical. Most lossy audio and visual compression techniques rely on the lack of sensitivity in humans to pick up detailed information in certain scenarios. Similarly limitations in the sensitivity of human touch could be exploited to create haptic models with much less detail and thus requiring smaller bandwidth. The focus of this paper is on the force thresholds of the human haptic system that can be used in a psychophysically motivated lossy haptic (force) compression technique. Most of the research in this field has measured the just noticeable difference (JND) of the human haptic system with a human user in static interaction with a stationary rigid object. In this paper our focus involves cases where the human user or the object are in relative motion. An example of such an application would be the haptic rendering of the user's hand in contact with of a high-viscous material or interacting with a highly deformable object. Thus an approach is presented to measure the force threshold based on the velocity of the user's hand motion. Two experiments are conducted to detect the absolute force threshold (AFT) of the human haptic system using methodologies from the field of psychophysics. The AFTs are detected for three different ranges of velocity of the user's hand motion. This study implies that when a user's hand is in motion fewer haptic details are required to be stored calculated or transmitted. Finally the implications of this study on a more complete future study will be discussed.

Single-piece AcrySof intraocular lens implantation in children with congenital and developmental cataract

To evaluate surgical outcomes of 1-piece AcrySof SA30AL intraocular lens (IOL) (Alcon Laboratories) implantation in children having surgery for congenital and developmental cataracts. Iladevi Cataract & IOL Research Centre, Raghudeep Eye Clinic, Ahmedabad, India. This prospective observational study comprised 134 consecutive eyes of 84 children from 2 to 15 years old who had surgery for congenital and developmental cataract. Two groups were formed depending on the age of the child at surgery. Primary posterior continuous curvilinear capsulorhexis (PCCC) was performed in children younger than 6 years (Group 1, 66 eyes), and no PCCC was performed in children older than 6 years (Group 2, 68 eyes). Vitrectomy was not performed. An AcrySof IOL was implanted in the bag in all eyes except 1 in Group 1, which received a sulcus-fixated IOL. The study's primary outcome measures were the incidence of visual axis obscuration and the need for a secondary procedure to clear the axis. Secondary observations included the incidence of posterior synechias, cell deposits, and haptic compression. A test of proportion was applied to determine whether age was a risk factor for the development of visual axis obscuration. The mean age at surgery was 6.0 years +/- 3.2 (SD). The mean follow-up was 2.6 +/- 0.6 years. In Group 1, 20 eyes (30.3%) developed visual axis obscuration but only 6 (9.1%) required a secondary procedure. In Group 2, 20 eyes (29.4%) developed visual axis obscuration and 10 (14.7%) required secondary procedures. Posterior synechias were observed in 2 eyes (3.0%) in Group 1 and none in Group 2. Cell deposits were seen in 8 eyes (12.1%) in Group 1 and 8 eyes (11.8%) in Group 2. Haptic compression was noted in 1 eye in Group 2. Mild IOL decentration was observed in the 1 eye with a sulcus-fixated IOL. The 1-piece AcrySof IOL provided satisfactory visual axis clarity, produced an acceptable inflammatory response, and maintained centration in pediatric eyes.

Comparison of the biomechanical behavior of foldable intraocular lenses

Purpose: To compare a standardized battery of biomechanical laboratory tests to assess the performance of popular foldable intraocular lenses (IOLs). Setting: Biomedical testing facilities, Alcon Research, Ltd., Fort Worth, Texas, USA. Methods: Using industry-standard biomechanical testing techniques, 1- and 3-piece foldable IOLs (Alcon AcrySof® MA60BM, MA30BA, SA30AL, SA60AT; Allergan Sensar® AR40, PhacoFlex® II SI-40NB; Bausch & Lomb Soflex® LI61U; Pharmacia & Upjohn CeeOn® 920) and a 1-piece all-poly(methyl methacrylate) (PMMA) IOL (Alcon MZ30BD) were tested under identical conditions with regard to (1) tensile/elastic properties by comparing haptic pull strength and haptic elongation and (2) compression properties by comparing haptic compression forces, haptic compression force decay over time, and axial displacement. All tests were performed with the IOLs submersed in a controlled-temperature water bath (mean 35°C ± 2°C [SD]). Results: For all IOLs, the ultimate elongation and pull strength of the haptics before failure was highest with the Alcon SA30AL and SA60AT. Similarly, the force required to compress haptics to a prescribed 10.0 mm diameter was least with the SA30AL and the SA60AT lenses. These 1-piece lenses also showed the least decay of residual compression force as a function of time. Optic displacement along the optical axis with haptic compression to 10.0 mm was least with the Alcon 1-piece IOLs and the all-PMMA control IOL. Conclusion: AcrySof 1-piece SA30AL and SA60AT IOLs demonstrated superior biomechanical characteristics over other foldable IOL designs.