Mohamed Aly

University of Miami Miller School of Medicine, Miami, Florida, United States

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Publications (5)13.21 Total impact

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    ABSTRACT: To assess the biocompatibility and intraocular pressure (IOP) lowering effect of a novel glaucoma drainage implant in rabbits. Sixteen New Zealand white rabbits received one of three glaucoma drainage implants fabricated from poly-(styrene-b-isobutylene-b-styrene [SIBS]) with an internal diameter of the lumen of either 70 (6 eyes), 100 (6 eyes), or 150 (4 eyes) μm. Clinical follow-up examinations were performed during 6 months and postmortem eyes were studied with light microscopy. Smaller internal diameter implants were associated with fewer complications. IOP levels were not statistically different among the groups. No eyes developed serious complications. Mild chronic inflammation was observed around the tube using light microscopy. SIBS glaucoma drainage implants did not produce clinically detectable intraocular inflammation in a rabbit model. The 70- and 100-μm SIBS drainage devices demonstrated fewer postoperative complications. IOP levels were not statistically different from control eyes in all groups.
    Ophthalmic Surgery Lasers and Imaging 01/2011; 42(4):338-45. · 1.46 Impact Factor
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    ABSTRACT: The aged eye's ability to change focus (accommodation) may be restored by replacing the hardened natural lens with a soft gel. Functionalised polysiloxane macromonomers, designed for application as an injectable, in situ curable accommodating intraocular lens (A-IOL), were prepared via a two-step synthesis. Prepolymers were synthesised via ring opening polymerisation (ROP) of octamethylcyclotetrasiloxane (D(4)) and 2,4,6,8-tetramethylcyclotetrasiloxane (D(4)(H)) in toluene using trifluoromethanesulfonic acid (TfOH) as catalyst. Hexaethyldisiloxane (HEDS) was used as the end group to control the molecular weight of the prepolymers, which were then converted to macromonomers by hydrosilylation of the SiH groups with allyl methacrylate (AM) to introduce polymerisable groups. The resulting macromonomers had an injectable consistency and thus, were able to be injected into and refill the empty lens capsular bag. The macromonomers also contained a low ratio of polymerisable groups so that they may be cured on demand, in situ, under irradiation of blue light, in the presence of a photo-initiator, to form a soft polysiloxane gel (an intraocular lens) in the eye. The pre-cure viscosity and post-cure modulus of the polysiloxanes, which are crucial factors for an injectable, in situ curable A-IOL application, were controlled by adjusting the end group and D(4)(H) concentrations, respectively, in the ROP. The macromonomers were fully cured within 5 min under light irradiation, as shown by the rapid change in modulus monitored by photo-rheology. Ex vivo primate lens stretching experiments on an Ex Vivo Accommodation Simulator (EVAS) showed that the polysiloxane gel refilled lenses achieved over 60% of the accommodation amplitude of the natural lens. An in vivo biocompatibility study in rabbits using the lens refilling (Phaco-Ersatz) procedure demonstrated that the soft gels had good biocompatibility with the ocular tissue. The polysiloxane macromonomers meet the targeted optical and mechanical properties of a young natural crystalline lens and show promise as candidate materials for use as injectable, in situ curable A-IOLs for lens refilling procedures.
    Biomaterials 11/2010; 31(32):8153-63. · 8.31 Impact Factor
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    ABSTRACT: To determine whether changes in elastic properties of the lens capsule ex vivo with age contribute to the forces necessary for accommodation. Postmortem human (n = 22; age average: 41 +/- 17 years; range: 6-7) and cynomolgus monkey (n = 19; age average: 7.7 +/- 1.8 years, range: 4.2-10) tissues including the lens, capsule, zonules, ciliary body, and sclera were mounted in an optomechanical lens-stretching system. Starting at 0 load, the sclera was symmetrically stretched to 2 mm in 0.25-mm steps at a speed of 0.1 mm x s(-1). The load and lens diameter were measured at each step. The lens contents were removed through a mini-capsulorhexis. The stretching cycles were repeated on the empty capsular bag. The forces necessary to stretch the natural lens and empty bag were quantified as a function of age and compared. The force needed to stretch the empty lens capsule was independent of age (human, 2.6-34.9 g/mm [25.2-342.7 mN/mm]; monkey, 8.2-21.3 g/mm [80.3-208.6 mN/mm]). The ratio of the force necessary to stretch the empty lens capsule to the force necessary to stretch the natural lens decreased with age in the human and monkey lenses (P = 0.003, P = 0.72, respectively). The mechanical properties of the empty lens capsule assessed ex vivo in a lens stretcher remain constant with age, suggesting that the changes in elasticity of the lens capsule do not play a significant role in presbyopia. In young eyes, the lens capsule determines the force necessary to stretch the whole lens. The age-related increase in force needed to stretch the lens is due to changes in the lens contents.
    Investigative ophthalmology & visual science 06/2008; 49(10):4490-6. · 3.43 Impact Factor
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    ABSTRACT: Purpose: To demonstrate the biocompatibility of SIBS implants as compared to PDMS implants in the treatment of retinal detachment in New Zealand White (NZW) rabbit model.1,2 Introduction: Scleral encircling bands, fixation rings and buckles are utilized for closure of retinal breaks and retina reattachment. The FDA approved PDMS-implant is associated with several post-operative complications, involving thick-fibrotic encapsulations. SIBS, an elastomeric triblock copolymer, was recently FDA approved for use in a cardiovascular drug eluting stent (TAXUSTM, Boston Scientific Corp., MA) and showed excellent biocompatibility and slow drug release capability. Materials and Methods: SIBS (9-mol%-styrene) implants were fabricated (InnFocus LLC, USA) to match PDMS implants (Labtician, Inc, Canada) dimensions. 5 NZW rabbits received SIBS and 4, PDMS-implants. Post-operative exam sequence: day 1 and 2, week 1, 2, 3, 4 and 6, and monthly thereafter for up to 1 year. Anatomohistopathology exams sequence: one SIBS animal at 6 weeks and one animal of each treatment group at 3 and 6-months, and two at 12-months. Results: SIBS compared to PDMS animals exhibited less inflammation and a better buckling effect during the first 6 weeks. At POD 9 months, the conjunctival injection in the SIBS rabbit was none as opposed to the PDMS value and the buckling effect for both groups were equal. There were no visible signs of encapsulation with SIBS. There were no infections in the 9 animals and none of the implants extruded thus far (
    Proc SPIE 03/2006;
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    ABSTRACT: Purpose: To design and test the Miami-InnFocus Drainage Implant (MiDi) as a glaucoma shunt that is biocompatible, flexible, and significantly smaller than existing commercial implants in order to prevent postoperative hypotony, inflammation, scarring, erosion, and extrusion. Methods: A new biomaterial composed of styrene-b-isobutylene-b-styrene (SIBS) was used in a novel design for a glaucoma drainage implant. The implant consists of a tube 11mm long with an inner diameter of 70, 100, and 150 mum and outer diameter of 250 mum with a 1mm2 tab located 4.5mm from the proximal tip to prevent migration. The device was implanted in 15 New Zealand White rabbits for biocompatibility and efficacy testing. A similarly designed implant made of polydimethylsiloxane was implanted in 6 other animals as a pseudo-control. Typical GDI implantation technique was modified for this device. The proximal end of the new SIBS implant was inserted 2mm into the anterior chamber and the distal end placed in a subconjunctival space created by the surgeon. Biocompatibility of the device was studied by slit-lamp follow-up and intraocular pressure (IOP) measurements recorded periodically. Results: Biocompatibility of the MiDi was excellent. A low and diffuse bleb was observed with these devices. All SIBS tubes were patent 9 months after insertion. Immunostaining demonstrated non-continuous deposition of collagen with virtually no encapsulation. No macrophages or myofibroblast were visible around the SIBS polymer which was found more bioinert than the control PDMS. Conclusion: This newly designed glaucoma implant is clinically biocompatible in the rabbit model and maintained 100% patency at 9 months.
    Proc SPIE 01/2006;