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Biomedical subjects

Nick Mamalis

Publications and source records attributed to Nick Mamalis.

At least 37 records · Page 2Linked to original sources
PubMed2006

Hydrophilic acrylic intraocular lens as a drug-delivery system for fourth-generation fluoroquinolones.

PURPOSE: To evaluate the ability and safety of a hydrophilic acrylic intraocular lens (IOL) as a drug-delivery system for commercially available gatifloxacin and moxifloxacin. SETTING: David J. Apple, MD, Laboratories for Ophthalmic Research, John A. Moran Eye Center, Department of Ophthalmology and Visual Sciences, University of Utah, Salt Lake City, Utah, USA. METHODS: Thirty rabbits were divided into 2 similar groups. In Group A (15 rabbits, 30 eyes), hydrophilic acrylic IOLs (C-flex, Rayner Intraocular Lenses, Ltd.) presoaked for 24 hours in commercially available solutions of gatifloxacin 3 mg/mL or moxifloxacin 5 mg/mL were implanted after evacuation of the crystalline lens. Group B (15 rabbits, 30 eyes) had topical preoperative and postoperative cataract prophylaxis with gatifloxacin 3 mg/mL or moxifloxacin 5 mg/mL; IOLs that were not presoaked were also implanted after evacuation of the crystalline lenses. In both groups, aqueous humor samples were taken 4, 8, or 12 hours after IOL implantation (5 eyes at each time point) to determine the antibiotic concentrations. Clinical examinations were performed 24 hours postoperatively. RESULTS: The antibiotic concentrations in Group A (presoaked IOLs) were statistically significantly higher than those in Group B (topical) for both antibiotics in all postoperative samples except moxifloxacin at 12 hours. In both groups, there was no statistically significant difference between the concentrations of the 2 antibiotics. No eye showed signs of clinical toxicity. CONCLUSION: Results show the C-flex IOL is a safe and effective drug-delivery system for fourth-generation fluoroquinolones.

Acrylic Resins↗
PubMed2006

Postoperative surface deposits on intraocular lenses in children.

PURPOSE: To report the clinicopathologic features of 4 intraocular lenses (IOLs) composed of 3 different hydrophilic biomaterials explanted from children who had postoperative opacification of the IOL optic. SETTING: David J Apple, MD, Laboratories for Ophthalmic Devices Research, John A. Moran Eye Center, Department of Ophthalmology and Visual Sciences, University of Utah, Salt Lake City, Utah, USA. METHODS: The IOLs were explanted 20, 11, 22, and 25 months postoperatively from children aged 10, 3, 36, and 20 months old, respectively, at IOL implantation. Clinical data were obtained to correlate the findings with possible associated risk factors. The explanted IOLs were examined by gross and light microscopy. They were further analyzed with a stain for calcium, alizarin red 1%. Scanning electron microscopy and energy dispersive X-ray spectroscopy (EDS) were also performed. RESULTS: The primary reason for cataract surgery in Case 1 and Case 2 was persistent hyperplastic primary vitreous (PHPV); 1 patient received a B-Lens IOL (Hanita) and the other a Centerflex IOL (Rayner). The primary reason in Case 3 was familial bilateral congenital cataract and in Case 4, rubella cataract; both patients received a Hydroview IOL (Bausch & Lomb). All 4 IOLs had surface deposits on the optic, but the morphology of the deposits on the B-Lens and Centerflex IOLs was different than that in previously reported cases. The deposits in all four cases stained positive with alizarin red and consisted of calcium and phosphorus when imaged with EDS. CONCLUSIONS: Calcified deposits on 2 Hydroview IOLs explanted from children were similar to those seen in adults with the same IOL. The deposits on the B-Lens and Centerflex IOLs were probably secondary to a breakdown of the blood-aqueous barrier caused by preexisting PHPV.

Anthraquinones↗
PubMed2006

A light adjustable lens with injectable optics.

The light adjustable lens (LAL) is an innovative intraocular lens optic composed of partially polymerized macromers with an appropriately bonded photosensitizer. The injectable technology and multifocality associated with the LAL can produce precise refractive correction and, it is hoped, the type of accommodative range that is taken for granted during youth. Combining these technologies with a lens material that behaves like the crystalline lens of 25-year-old could precisely return near and distance vision to older adults.

Accommodation, Ocular↗
PubMed2006

New technology IOL optics.

There has been a rapid evolution in the field of intraocular lens (IOL) manufacture, much of it influenced by the development of microincision surgical techniques and wavefront aberrometry.Thi article discusses new technology that has been applied to modern IOL optics, including multifocal, toric, blue-blocker, accommodative, and aspheric IOLs; lenses designed to be inserted through sub 2-mm incisions; and an implantable telescope for macular degeneration.

Humans↗
PubMed2006

New endoscopic technique to analyze various modern specialized intraocular lenses in research eyes and human eyes obtained postmortem.

PURPOSE: To describe a new modification of the Miyake-Apple posterior video photographic technique and its 2 variations. We have developed a new endoscopic technique that is especially amenable for observation of modern specialized intraocular lenses (IOLs). DESIGN: Laboratory study. PARTICIPANT: Three cadaver eyes obtained postmortem. METHODS: Human eyes obtained postmortem were prepared according to our modified preparation technique used for analyses of whole globes. An intraocular endoscope was utilized to demonstrate all aspects of the interior of an experimentally implanted IOL, with specialized reference to anterior segment structures, obtaining posterior, oblique, and side view images. MAIN OUTCOME MEASURES: Different interior dynamic views of the anterior segment structures before and after implantation of an IOL. RESULTS: High-magnification images of different intraocular structures both before and after device insertion as well as the device itself were obtained. Oblique and side view images from different locations were also available and informative. These images helped to create a 3-dimensional view of these objects and their relations to the surrounding structures. CONCLUSION: The combination of the intraocular endoscope with the closed-system technique is a useful addition to our 3 previously described techniques: (1) the original Miyake-Apple posterior video/photograph technique and the (2) closed system and (3) side/oblique view (keyhole technique) modifications.

Anterior Eye Segment↗
PubMed2006

Intraocular concentrations of gatifloxacin and moxifloxacin in the anterior chamber via diffusion through the cornea using collagen shields.

PURPOSE: To evaluate the penetration of gatifloxacin and moxifloxacin into the anterior chamber, and any adverse reaction to the cornea, using collagen shields presoaked in oversaturated solutions of the antibiotics. METHODS: Collagen shields, presoaked for 10 minutes in an oversaturated solution of gatifloxacin or moxifloxacin, were placed on the surface of each of the corneas of 15 rabbits for a total of 30 eyes (15 in each group). The antibiotics were prepared by dissolving the powder form of the antibiotics in a solution until no further particulate could be further dissolved. Aqueous humor samples were taken 3.5 and 6 hours later. RESULTS: The initial concentrations of gatifloxacin and moxifloxacin were 5.43 +/- 0.16 mg/mL and 3.14 +/- 0.22 mg/mL, respectively. The average concentration of gatifloxacin in the anterior chamber was higher than that of moxifloxacin at the 3.5-hour sample (6.32 +/- 2.67 microg/mL versus 3.55 +/- 3.5 microg/mL, P = 0.0034). The concentrations of both antibiotics, although decreased, remained relatively high at the 6-hour sample (1.39 +/- 1.13 microg/mL versus 0.816 +/- 0.6 microg/mL at 6 hours, respectively, P = 0.22). No obvious clinical or histologic signs of toxicity were noticed in either group. CONCLUSION: Gatifloxacin and moxifloxacin showed good penetration into the anterior chamber with no obvious adverse reaction to the cornea. The concentrations in the anterior chamber exceeded the minimal inhibitory concentration (MIC) 90 of most organisms responsible for postoperative endophthalmitis (POE).

Animals↗
PubMed2006

Histology of posterior lamellar keratoplasty.

PURPOSE: To report histology of a posterior lamellar graft performed to treat clinically significant endothelial disease in a patient with Fuchs dystrophy. METHODS: A 78-year-old patient with Fuchs dystrophy underwent posterior lamellar keratoplasty (PLK), the original form of endothelial keratoplasty performed with manual lamellar dissection of the recipient and donor corneas. Eighteen months later, the patient had herpes simplex virus keratitis and graft rejection episodes. One year after the infection resolved (2.5 years after PLK), penetrating keratoplasty was performed, and the excised corneal button was examined. RESULTS: Histopathologic evaluation of the corneal button showed no discernible interface, opacity, or gapping between the anterior host stromal tissue and PLK donor tissue or any signs of significant migration of donor endothelial cells onto recipient tissue. CONCLUSION: This PLK histology showed firm attachment with no visible interface between the posterior donor and anterior host stromal tissue. Surprisingly, no significant donor endothelial cell migration was detected on adjacent recipient tissue where Descemet membrane had been excised or where endothelial cells were lost as a result of the procedure.

Aged↗
PubMed2006

Donor descemet membrane detachment after endothelial keratoplasty.

PURPOSE: To describe histopathologic characteristics of an endothelial keratoplasty (EK) that was performed to treat a previously failed penetrating keratoplasty (PK) and in which the cornea failed to clear after partial detachment of Descemet membrane from the EK donor button. The Descemet membrane and endothelium from the PK were intentionally retained during the EK procedure. METHODS: After EK, the cornea failed to fully clear in 5 months, and a PK was performed. The removed corneal button was grossly described and routinely processed for hematoxylin-eosin (H&E) and periodic acid-Schiff (PAS) staining, with photographs taken of any pertinent findings. RESULTS: Grossly on the endothelial side, there was some adherent iris pigment delineating an off-center fold in the EK Descemet membrane, consistent with intraoperative observation of a fold across the width of the donor button and postoperative slit-lamp images showing partial detachment of Descemet membrane. Microscopic examination revealed a recipient corneal button from a prior PK centrally and EK donor button attached posteriorly. Descemet membrane was not stripped from the prior PK during EK and was intact. No endothelial cells were detected on the PK Descemet membrane. The anterior stromal surface of the EK was well apposed to the prior PK Descemet membrane, with no pseudoanterior chamber or cleft of any type noted between them. The EK Descemet membrane had a central fold, and the endothelium was markedly attenuated. CONCLUSION: The EK graft was well apposed with apparent good adherence to the recipient's prior failed PK, and early endothelial failure was attributable to partial Descemet membrane detachment.

Adult↗
PubMed2006

A light adjustable lens with injectable optics.

PURPOSE OF REVIEW: Technology exists today that could permit refractive precision unheard of at the present time plus the correction of higher-order aberrations and restoration of accommodation in presbyopic adults. RECENT FINDINGS: With the light adjustable lens, after surgery, the shape of the lens can be customized to treat spherical, cylindrical and other higher-order aberrations. The posterior surface of the lens can be adjusted to create both refractive multifocality and diffractive bifocality. It can be made out of a variety of materials, some of which can be injected into the capsule, filling it, thus replicating the original shape of a crystalline lens. While the current technique of bag filling does permit the less viscous materials to leak out of the bag this is a solvable problem. For example, a disc can fill an ordinary-sized capsulorrhexis opening, allowing removal of the cataract using standard techniques and filling behind this disc. Also the material, once injected, could be polymerized. Posterior capsule opacification is also potentially solvable with devices that completely destroy lens epithelial cells or through a polymerization process of the new lens material in which the reaction destroys the capsular cells and actually binds to the capsule. SUMMARY: It is apparent that light adjustable lenses plus injectable technology, and multifocality can produce precise refractive correction and, hopefully, the type of accommodative range that we take for granted when we are young. Combining these technologies with a lens material that behaves like a crystalline lens of a 25 year old could precisely return near and distance vision to older adults.

Accommodation, Ocular↗
PubMed2006

Evaluation of the effects of hydrodissection with antimitotics using a rabbit model of Soemmering's ring formation.

BACKGROUND: Regeneration/proliferation of lens material within the capsular bag still is the most frequent complication after cataract surgery. We aimed to evaluate the effects of hydrodissection with low doses of antimitotics on the overall regeneration/proliferation of lens material in rabbit eyes, using a model allowing the lens material to be confined to the equatorial region of the capsular bag, facilitating its quantification. METHODS: Twelve albino rabbits underwent bilateral phacoemulsification. Their eyes were randomized to receive 0.4 cc of balanced salt solution, 5-fluorouracil (12.5 mg/mL) or mitomycin C (0.1 mg/mL) during hydrodissection. They were left aphakic, so the capsulorhexis would fuse with the posterior capsule postoperatively. After 4 weeks, killing/enucleation was performed. Regeneration/proliferation of lens material within the equatorial capsular bag (Soemmering's ring) was graded from the Miyake-Apple view (0-4). Its area was also calculated (microm(2)) from direct measurements performed on histological sections. RESULTS: The capsulorhexis margin fused with the peripheral posterior capsule, so the central posterior capsule remained clear. There was no significant difference among the groups (Kruskal-Wallis test) regarding Soemmering's ring gross grading (P = 0.511), number of lens epithelial cell layers lining the inner surface of the capsular bag (P = 0.310) and Soemmering's ring microscopic cross-sectional area (P = 0.638). CONCLUSIONS: The effect of different solutions on after-cataract should be assessed in terms of overall regeneration/proliferation of lens material within the capsular bag, in addition to posterior capsule opacification. When administered in low doses during hydrodissection, 5-fluorouracil and mitomycin C did not show a significant inhibitory effect on after-cataract formation in rabbit eyes.

Acetates↗
PubMed2005

New intraocular lens technology.

PURPOSE: To review the current status of phakic intraocular lenses (IOLs), intraocular treatment of presbyopia, and IOLs that filter some blue light. DESIGN: Review of current information on the subject from numerous sources. METHODS: Medline search and Internet search engines on the topics of phakic IOLs, presbyopia or multifocal IOLs, and blue light and macular degeneration. RESULTS: An iris fixated phakic IOLs is now approved in the United States (US). There are concerns for corneal endothelial stability and late dislocation. Other approaches include anterior chamber fixation with concerns of corneal endothelial stability and pupil elongation, and posterior chamber fixation with concerns of cataract formation, IOL dislocation, and pigment dispersion. Intraocular treatment of presbyopia includes monovision, multifocal, and accommodative IOLs. Which approach is superior today is still not clear. There are IOLs designed to block some blue light to potentially lessen the risk of age-related macular degeneration (ARMD). While there is presumptive evidence of this, no definitive study shows such a correlation. Color perception issues are unlikely to be a problem. While decreased scotopic vision has been proposed, there is no study that proves this is an issue of clinical significance. CONCLUSIONS: The IOL field is dynamic with many new choices. Phakic IOLs and treatment of presbyopia will be an increasingly important part of ophthalmology; however, there are important unresolved issues. With better evidence that blue light is an important variable in ARMD, such an approach could rapidly become the standard.

Biomedical Technology↗
PubMed2005

Posterior capsule opacification in rabbit eyes implanted with 1-piece and 3-piece hydrophobic acrylic intraocular lenses.

PURPOSE: To evaluate the outcome of posterior capsule opacification (PCO) after implantation in rabbit eyes of currently available 3-piece and 1-piece hydrophobic acrylic intraocular lenses (IOLs) with square optic edges. SETTING: John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA. METHODS: The 3-piece designs evaluated were the AR40e (Advanced Medical Optics Inc.) and the MA60AC (Alcon, Inc.); the 1-piece designs were the SA60AT and the SA30AT (Alcon, Inc.). Nine lenses of each type were implanted in a randomized manner by the same surgeon in 18 Dutch Belted pigmented rabbits. After a follow-up of 3 weeks, the rabbits were killed and analyses of the enucleated eyes were performed from the posterior or Miyake-Apple view. The intensity of central PCO, peripheral PCO, and Soemmering's ring formation was scored from 0 to 4. The area of Soemmering's ring formation was also scored from 0 to 4 based on the number of quadrants involved. Other parameters analyzed were capsulorhexis coverage of the IOL anterior surface, IOL centration, fixation, and presence of striae. Results from the posterior view were complemented by histopathologic evaluation of the eyes. RESULTS: No statistically significant difference was found between the 4 groups of IOLs in the parameters analyzed from the posterior view. When cell ingrowth occurred with the 1-piece designs, causing peripheral and central PCO formation, it was more likely to start at the optic-haptic junctions, as observed during the clinical follow-up with slitlamp examination and confirmed by gross and histopathologic analyses of the enucleated eyes. CONCLUSIONS: The square, truncated optic edge is the most important IOL design feature for PCO prevention. The optic-haptic junctions of the 1-piece designs appear to be sites where the barrier effect of the truncated optic edge is less effective.

Acrylic Resins↗
PubMed2005

Evaluation of the cataractogenic effect of viscoanesthetic solutions on the rabbit crystalline lens.

PURPOSE: To evaluate the toxicity and cataractogenic effect of solutions combining sodium (Na) hyaluronate 1.0% and 1.5% with lidocaine 1.0% on the rabbit crystalline lens. The amount of pupil dilation provided by the addition of lidocaine to the Na hyaluronate solutions was also assessed. SETTING: John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA. METHODS: Five solutions were injected into the anterior chamber of 18 pigmented rabbits in a randomized manner by the same surgeon, the intraocular component of VisThesia (Na hyaluronate 1.5%/lidocaine 1.0%), the intraocular component of VisThesia Light (Na hyaluronate 1.0%/lidocaine 1.0%), Ophthalin Plus (Na hyaluronate 1.5%), and a balanced salt solution; and both eyes of 2 other rabbits were injected with nonpreserved aqueous lidocaine 1.0%. The pupil diameter of each eye was measured before injection, immediately after, and 1 and 5 minutes after injection. After a follow-up of 3 months with slitlamp examinations, the rabbits were killed, and their eyes were enucleated. The crystalline lenses were evaluated from a posterior or Miyake-Apple view, and the eyes were fixated in 10% formalin for histopathologic analyses. RESULTS: Pupil diameter was significantly larger 1 and 5 minutes after injection in the VisThesia (P = .01 and P = .007) and VisThesia Light (P = .008 and P = .007) groups, whereas the differences were not significant in the Ophthalin Plus (P = .317 and P = .102) and balanced salt solution groups (P = .317 and P = .180). Fast and large pupillary dilation was observed in the aqueous lidocaine group, starting during the injection. No differences in the transparency of the natural lens and the red fundus reflex were noted during slitlamp examinations. Postmortem analyses from a posterior view also showed no differences in the transparency of the crystalline lens. The histopathologic appearance of the lens capsule, anterior and equatorial lens epithelial cells, and epithelial lens bow was comparable in the eyes, without signs of cell vacuolization or disruption. CONCLUSIONS: Intracameral injection of the solutions used in this study caused no localized opacity or overall change in the transparency of the crystalline lenses as observed during clinical and postmortem examinations as well as histopathologic analyses of the enucleated rabbit eyes. Viscoanesthesia may have application in phakic intraocular lens implantation.

Anesthetics, Local↗
PubMed2005

Experimental evaluation of the Corneal Concept 360 intraocular lens with the Miyake-Apple view.

PURPOSE: To evaluate a new single-piece, hydrophilic acrylic intraocular lens (IOL) designed to keep the anterior capsule away from the IOL optic, create the effect of a capsular tension ring, and prevent posterior capsule opacification (PCO). SETTING: John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA. MATERIALS AND METHODS: Four Concept 360 IOLs (Corneal Laboratoire) were implanted in 4 human cadaver eyes of various sizes (Miyake-Apple technique). Lens centration, ovalization of the capsular bag and capsulorhexis opening, distance between the anterior optic surface and the anterior capsule and between the posterior optic surface and the posterior capsule, as well as presence of capsular striae were evaluated. The capsular bag was stained with trypan blue, and the ophthalmic viscosurgical device (OVD) was stained with fluorescein to enhance visualization. RESULTS: In each eye, the lens conformed to the capsular bag with precise centration. No ovalization or distortion of the capsular bag or the capsulorhexis and no posterior capsule striae were observed. Measurements of the capsulorhexis diameter before and after IOL implantation were the same. The anterior capsule remained at distance from the anterior optic surface for 360 degrees, and tight contact between the posterior optic edge and the posterior capsule was observed. CONCLUSIONS: Use of the Miyake-Apple technique is useful in the evaluation of new IOL designs in experimental studies. Design features of the Concept 360 IOL are likely to decrease the outcome of postoperative capsular bag opacification. Long-term clinical studies are necessary to confirm these findings.

Acrylic Resins↗
PubMed2005

Acute haptic-induced ciliary sulcus irritation associated with single-piece AcrySof intraocular lenses.

We report an analysis of 3 single-piece hydrophobic acrylic intraocular lenses (IOLs) that were explanted because of complications related to the presence of their haptics in the ciliary sulcus. In 2 cases, the IOL was primarily implanted in the ciliary sulcus because of inadequate posterior capsule support. In the third case, postoperative displacement of 1 haptic in the sulcus was associated with hyphema and vitreous hemorrhage. Ultrasound biomicroscopy confirmed the contact between the haptic and iris. Areas of iris atrophy were observed in all cases. Light microscopy and scanning electron microscopy of the explanted lenses revealed the presence of pigmentary dispersion on the anterior surfaces. In Case 3, the pigments were concentrated on the surface of the haptic that was displaced from the capsular bag and on the corresponding optic-haptic junction. Scanning electron microscopy also showed the IOL's squared edges and unpolished side walls. The flexibility and thickness of the single-piece hydrophobic acrylic haptics, as well as the square optic and haptic edges, may increase the risk for iris chafing when the haptics are in the sulcus. Therefore, sulcus fixation of this IOL design is not recommended.

Acrylic Resins↗
PubMed2005

Late dislocation of scleral-sutured posterior chamber intraocular lenses.

PURPOSE: To examine a recent series of late scleral-sutured posterior chamber intraocular lens (PCIOL) dislocations to identify possible causes and preventive measures. SETTING: Price Vision Group, Indianapolis, Indiana, USA. METHODS: In this retrospective non-comparative interventional case series, 5 consecutive patients received treatment for dislocated scleral-sutured PCIOLs between July 2002 and March 2004. Dislocated lenses were resutured or replaced with another scleral-sutured PCIOL. RESULTS: Dislocation of scleral-sutured PCIOLs occurred 7 to 14 years after implantation. Four dislocations were spontaneous, and 1 was precipitated by trauma. In each case, the suture affixing 1 or both haptics failed. There was no evidence that the suture had eroded through the tissue or that the knot had untied. Microscopic analysis of an explanted IOL with remnants of the suture attached showed localized degradation and cracking of the polypropylene suture material where it had been embedded in the scleral tissue. CONCLUSION: Suture-fixated PCIOLs can dislocate due to degradation of the suture material over time. The use of larger diameter (9-0 instead of 10-0) polypropylene suture material and placement of the haptic and sutures in the ciliary sulcus to promote attachment of scar tissue may enhance the long-term stability of scleral-fixated PCIOLs.

Adult↗