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Biomedical subjects

Nick Mamalis

Publications and source records attributed to Nick Mamalis.

At least 19 recordsLinked to original sources
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↗
PubMed2005

Salzmann's-like nodular degeneration following laser in situ keratomileusis.

We report the development of bilateral Salzmann's-like corneal lesions located at the site of laser in situ keratomileusis (LASIK) flap margins in 2 patients. These lesions resulted in ocular surface irritation as well as induction of irregular astigmatism and associated loss of best corrected visual acuity. Both patients had bilateral LASIK before the occurrence of the corneal lesions. A biopsy was performed on 1 nodule. The epithelium overlying this raised bluish-white corneal lesion appeared irregular in thickness, with replacement of Bowman's layer by periodic acid-Schiff positive thickened basement membrane-like material. Underlying this basement membrane was a layer of relatively regular, hypocellular, collagenlike connective tissue, which demonstrated hyalinization on trichrome staining. Based on these 2 cases, it seems possible that the hyposecretion of tears, decreased blink rate, and Dellen effect that often occur following LASIK could produce the corneal irritation needed to induce Salzmann's nodular degeneration.

Adult↗
PubMed2005

Postoperative localized opacification of the new MemoryLens design: analyses of an explant.

We describe a different form of opacification of the new MemoryLens intraocular lens model CV232, leading to a decrease in visual acuity and requiring explantation. A well-circumscribed, centrally/paracentrally located opacification of the optic was observed, with the aspect of a small "lens inside the lens." Histochemical and surface analyses revealed the presence of calcified deposits within a void in the optic substance. This void was seen as a linear optic breach in analysis of an optic cylindrical block cut through the area of opacification, from a sagittal view. The origins of the optic void are unclear.

Aged↗
PubMed2005

Surface calcification of a 3-piece silicone intraocular lens in a patient with asteroid hyalosis: a clinicopathologic case report.

OBJECTIVE: To illustrate the laboratory findings in a patient with bilateral asteroid hyalosis who presented with calcified deposits on a 3-piece silicone intraocular lens (IOL). DESIGN: Observational case report. METHODS: A 76-year-old diabetic woman underwent uneventful cataract surgery in 1994 with implantation of a silicone-optic polypropylene-haptic IOL in the left eye. A neodymium:yttrium-aluminum-garnet (Nd:YAG) laser posterior capsulotomy was performed 2 years after cataract surgery, but persistent whitish deposits were observed on the posterior optic surface of the lens. Over the next 3 years, the opacification increased in the region corresponding to the capsulotomy. The IOL was explanted/exchanged. The right eye had cataract surgery in 1995. The acrylic lens implanted in this eye developed no opacities after 6 years. MAIN OUTCOME MEASURES: Gross, microscopic, and surface analyses of the explanted IOL. RESULTS: Gross and light microscopic analyses revealed the presence of confluent crustlike deposits on the central area of the posterior optic surface, as well as Nd:YAG pits. Individual spherules exhibiting a Maltese-cross pattern under polarizing light were also observed. Energy dispersive x-ray spectroscopic analyses demonstrated the composition of the confluent deposits to be similar to hydroxyapatite. CONCLUSIONS: An association between asteroid hyalosis and dystrophic calcification of IOLs has been reported only with silicone plate haptic designs. The material opacifying the 3-piece silicone lens probably was derived from the asteroid bodies or from the process that results in this vitreous condition. Clinical evaluation of other pseudophakic patients with asteroid hyalosis will confirm if this phenomenon is restricted to silicone IOLs.

Aged↗
PubMed2004

Surface calcification of silicone plate intraocular lenses in patients with asteroid hyalosis.

PURPOSE: To report three cases in which a silicone-plate lens was explanted because of whitish deposits on the posterior optic surface. DESIGN: Observational case series with clinicopathological correlation. PATIENTS AND METHODS: In the three instances, the deposits were observed at least 2 years after uneventful cataract surgery. All of the patients had unilateral mild asteroid hyalosis in the concerned eye. After explantation of the lenses, gross and light microscopic analyses were performed. The posterior optic surfaces of the lenses also underwent scanning electron microscopy coupled with energy dispersive x-ray spectroscopy for analysis of the elemental composition of the deposits. RESULTS: Gross and light microscopic analyses revealed well-demarcated areas of whitish deposits on the posterior optic surface of the lenses, as well as multiple pits caused by Neodymium:yttrium aluminum garnet laser treatments. The deposits formed an amorphous layer with a "crustlike" appearance, which was confirmed by scanning electron microscopy. X-ray spectroscopy analyses demonstrated the composition of the deposits to be similar to hydroxyapatite. CONCLUSIONS: The material opacifying the lenses was probably derived from the asteroid bodies or from a similar process that results in this vitreous condition. We were unaware of this association between asteroid hyalosis and late postoperative dystrophic calcification of silicone lenses.

Aged↗
PubMed2004

Capsular bag opacification after experimental implantation of a new accommodating intraocular lens in rabbit eyes.

PURPOSE: To evaluate the development of capsular bag opacification in rabbit eyes after implantation of an intraocular lens (IOL) designed to minimize contact between the anterior capsule and the IOL and ensure expansion of the capsular bag. SETTING: David J. Apple, MD Laboratories for Ophthalmic Devices Research, John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA. METHODS: Ten New Zealand white rabbits had a study IOL (new accommodating silicone IOL [Synchrony, Visiogen, Inc.]) implanted in 1 eye and a control IOL (1-piece plate silicone IOL with large fixation holes) implanted in the other eye. Intraocular lens position, anterior capsule opacification (ACO), and posterior capsule opacification (PCO) were qualitatively assessed using slitlamp retroillumination photographs of the dilated eyes. Anterior capsule opacification and PCO were graded on a 0 to 4 scale after the eyes were enucleated (Miyake-Apple posterior and anterior views after excision of the cornea and iris). The eyes were also evaluated histopathologically. RESULTS: The rate of ACO and PCO was significantly higher in the control group. Fibrosis and ACO were almost absent in the study group; the control group exhibited extensive capsulorhexis contraction, including capsulorhexis occlusion. Postoperative IOL dislocation into the anterior chamber and pupillary block syndrome were observed in some eyes in the study group. CONCLUSIONS: The special design features associated with the study IOL appeared to help prevent PCO. Complications in the study group were probably caused by the increased posterior vitreous pressure in rabbit eyes compared to human eyes and the relatively large size of the study IOL relative to the anterior segment of rabbit eyes.

Animals↗
PubMed2004

Posterior capsule opacification in rabbit eyes implanted with hydrophilic acrylic intraocular lenses with enhanced square edge.

PURPOSE: To evaluate the development of posterior capsule opacification (PCO) after implantation of single-piece hydrophilic acrylic intraocular lenses (IOLs) with an enhanced square edge. SETTING: John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA. METHODS: The standard 570H Centerflex (Rayner Ltd.) design was compared to 2 new designs with enhanced square edges: the 570E and the 570C. Ten IOLs of each type were implanted in a randomized manner by the same surgeon in 15 pigmented rabbits. After a follow-up of 3 weeks, the rabbits were killed and the eyes were analyzed from the posterior view. The intensity of central PCO, peripheral PCO, and Soemmering's ring formation was graded from 0 to 4. The area of Soemmering's ring was graded from 0 to 4 based on the number of quadrants involved. Other parameters analyzed were capsulorhexis coverage of the IOL edge and IOL centration and fixation. Results from the posterior view were complemented by histopathological evaluation. RESULTS: Posterior capsule opacification was lowest in the 570C group, highest in the 570H group, and intermediate in the 570E group. There was a statistically significant difference between the 3 groups in peripheral PCO (P = .039). No significant difference was found between the groups in the other parameters analyzed. When cell ingrowth occurred with the 570H, it started at the optic-haptic junctions, as observed during the clinical follow-up and confirmed by gross and histopathological analyses. CONCLUSIONS: The square optic edge is the most important IOL design feature for PCO prevention. However, it should be present for 360 degrees around the IOL optic to provide an effective barrier effect.

Acrylic Resins↗
PubMed2004

Complications of foldable intraocular lenses requiring explantation or secondary intervention--2003 survey update.

The sixth annual survey of complications associated with foldable intraocular lenses (IOLs) requiring explantation or secondary intervention was sent to members of the American Society of Cataract and Refractive Surgery and the European Society of Cataract and Refractive Surgeons. Preoperative data about visual acuity, patient signs and symptoms, and complications requiring IOL removal were evaluated. Complications were then tabulated for each of the following major foldable IOL groups: 3-piece monofocal silicone, 3-piece hydrophobic acrylic, 1-piece hydrophobic acrylic with haptics, 3-piece hydrophilic acrylic (hydrogel), 1-piece hydrophilic acrylic (hydrogel), 1-piece plate-type silicone, 3-piece multifocal silicone, and Collamer. Two hundred seventy-three surveys were returned for evaluation. Dislocation/decentration, incorrect lens power, IOL calcification, and glare/optical aberrations were the most common reasons for removing foldable IOLs. Good surgical technique, accurate IOL power measurements, and high manufacturing standards for foldable IOL materials and designs are the most important factors in avoiding complications with foldable IOLs.

Acrylic Resins↗
PubMed2004

Wavefront corrections of intraocular lenses.

This article describes two currently available intraocular lenses (IOLs) that have special design features allowing for correction of optical aberrations other than spherical refractive errors. Although they are not yet fully "customized" lenses, their development has involved average aberrations measured with wavefront technology. An experimental IOL manufactured with a special technology is also described that, when used in conjunction with wavefront sensing, has the potential for full customization.

Animals↗