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PubMed2004

High-order aberrations with Hydroview H60M and AcrySof MA30BA intraocular lenses: comparative study.

PURPOSE: To compare differences in high-order aberrations between 2 intraocular lenses (IOLs), the Hydroview H60M (Bausch & Lomb) and AcrySof MA30BA (Alcon). SETTING: Department of Ophthalmology, Nara Medical University, Nara, Japan. METHOD: Twenty-four eyes of 14 patients with a Hydroview IOL and 25 eyes of 20 patients with an AcrySof IOL who had uneventful phacoemulsification and a best corrected visual acuity better than 20/16 from 6 to 12 months after surgery were evaluated. High-order aberrations were measured using a Hartmann-Shack aberrometer at 4.0 mm and 6.0 mm wavefront aperture diameters, and IOL tilt and decentration were assessed by Scheimpflug videophotography. RESULTS: There were no differences between the 2 groups in IOL tilt and decentration (P>.05, Mann-Whitney U test). In the cornea, there were no differences between the 2 groups in high-order aberrations at 4.0 mm and 6.0 mm aperture diameters (P>.05, Mann-Whitney U test). In the whole eye, there was a significant difference between Hydroview (mean 0.441 microm +/- 0.147 [SD]) and AcrySof (0.696 +/- 0.287 microm) IOLs in spherical-like aberrations at the 6.0 mm aperture diameter (P =.00008, Mann-Whitney U test); there were no differences between the 2 groups in other aberrations. CONCLUSIONS: The type of IOLs influenced spherical-like aberrations. The IOL's shape was a particularly important factor in spherical-like aberrations. The aberrations may affect night driving in certain individuals.

Acrylic Resins↗
PubMed2004

Pathological evaluation of postmortem human eyes implanted with a new single-piece hydrophobic acrylic lens.

PURPOSE: To report the pathological findings in 14 human cadaver eyes implanted with a single-piece AcrySof(Alcon Laboratories) posterior chamber intraocular lens (IOL). SETTING: David J. Apple, MD Laboratories for Ophthalmic Devices Research, John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA. METHODS: Fourteen human autopsy eyes implanted with a single-piece AcrySof (SA30AL) IOL were evaluated. The eyes were sectioned at the equatorial plane, and the anterior segment containing the IOL in the capsular bag was evaluated from a posterior perspective (Miyake-Apple view) and from an anterior perspective (surgeon's view) after removal of cornea and iris. They were then processed through paraffin, sectioned, and stained with hematoxylin-eosin, periodic acid-Schiff, and Masson's trichrome and examined under light microscopy. RESULTS: All IOLs had symmetric in-the-bag fixation. Slight decentration was measured in 1 eye, which also had an anterior capsule tear. Grade 1 anterior capsule opacification was present in 9 eyes. No central posterior capsule opacification or posterior capsule folds were observed in any eye. Soemmering's ring formation was observed in 5 eyes. Zonular stretch caused by different degrees of capsular bag contraction was present in 4 eyes without decentration of the IOL. CONCLUSIONS: Analyses of pseudophakic cadaver eyes from the posterior (Miyake-Apple) view, complemented by microscopic analyses, proved useful in the evaluation of IOL-capsular bag interaction. These studies are more important in cases of newly introduced lens designs.

Anterior Eye Segment↗
PubMed2004

Heparin in the intraocular irrigating solution in pediatric cataract surgery.

PURPOSE: To investigate the antiinflammatory effects of adding heparin sodium to the irrigating solution to prevent fibrinoid reaction and related long-term complications after pediatric cataract surgery. SETTING: Department of Ophthalmology, Inonu University, Turgut Ozal Medical Center, Malatya, Turkey. METHODS: Thirty eyes of 18 children who had cataract or other ocular surgery were included in the study. Bilateral cataract surgery was performed in 20 eyes of 10 children and bilateral secondary intraocular lens (IOL) implantation in 4 eyes of 2 children (Group 1). Four eyes of 4 children had unilateral cataract surgery and 2 eyes of 2 children with previous perforating eye injury had synechiotomy and pupilloplasty (Group 2). Heparin sodium was added to the irrigating solution during surgery in 12 left eyes of children with bilateral surgery (Group 1a) and in all eyes in Group 2. Heparin sodium was not added during surgery in 12 right eyes of children having bilateral surgery (Group 1b, control). Early and late postoperative intraocular reactions were recorded and compared. RESULTS: In Group 1a (heparin added), 6 eyes had less fibrinoid reaction and fewer related complications such as posterior synechias, pupil irregularity, and intraocular lens (IOL) decentration than the fellow right eyes. No eye in Group 1a having primary cataract surgery had hyphema or intraocular bleeding. Hyphema occurred on the first postoperative day in 1 eye in Group 1a that had secondary IOL implantation. CONCLUSIONS: Adding heparin sodium to the irrigating solution decreased postoperative inflammatory and fibrinoid reactions and related complications such as synechias, pupil irregularity, and IOL decentration in pediatric cataract surgery. However, the use of heparin during surgery can be risky in eyes with a defective blood-aqueous barrier such as after previous ocular surgery.

Adolescent↗
PubMed2005

Effect of tilt of 2 acrylic intraocular lenses on high-order aberrations.

PURPOSE: To investigate the high-order aberrations (HoAs) in pseudophakia between 2 foldable acrylic intraocular lenses (IOL) with differences in the tilt of IOL. SETTING: Department of Ophthalmology, Nara Medical University, Nara, Japan. METHOD: Sixty-four eyes that had uncomplicated phacoemulsification and IOL implantation were assigned to 1 of 2 groups: Acryfold 60BB (HOYA [n=30 eyes]) and AcrySof MA60AC (Alcon [n=34 eyes]). All patients had best corrected visual acuity better than 20/25. High-order aberrations were measured using the Hartmann-Shack aberrometer at 4.0 mm and 6.0 mm wavefront aperture diameters, and the IOL tilt and decentration were measured using Scheimpflug videophotography. RESULTS: There was a significant difference in the IOL tilt (60BB=2.22 degrees +/- 1.44 (SD), 60AC=3.18 +/- 1.84 degrees; P=.041, Mann-Whitney U test), but no difference in IOL decentration (P>.05). In the cornea, there were no differences between the 2 groups in HoAs at 4.0 mm and 6.0 mm aperture diameters (P>.05, Mann-Whitney U test). In the whole eye, there was no difference between the 2 groups in spherical-like aberrations, coma-like aberrations, and total aberrations at the 4.0 mm and 6.0 mm aperture diameters (P>.05). The compensation of the internal optics with the 60BB group was better than with the 60AC group for coma-like (P=.037) and total aberrations (P=.010) at 6.0 mm aperture diameter. CONCLUSION: The smaller tilt of the IOL induced more compensation for the coma-like and total aberrations at the 6.0 mm aperture diameter. The IOL tilt should be small, especially in a large pupil, with regard to HoAs.

Aberrometry↗
PubMed2005

Biometry of phakic intraocular lens using Scheimpflug photography.

PURPOSE: To examine lateral and axial positioning of phakic intraocular lenses (IOLs) with iris fixation in the anterior chamber and to examine short-term stability of the IOL position. SETTING: The Netherlands Opthalmic Research Institute, Amsterdam, the Netherlands. METHODS: Thirty patients participated in the study. Thirty-one eyes were implanted with the 204 type myopia IOL, 14 eyes with the 206 myopia IOL, and 8 eyes with the 203 hyperopia IOL. Scheimpflug slitlamp photographs were made through the optical axis along 4 meridians of the eyes. Ray tracing was used to obtain the lateral and axial position of the IOLs. RESULTS: Centration of the IOL with respect to the pupil's center and the tilt angle of the IOL with respect to the optical axis of the eye were measured. Standard deviation of decentration was 0.21 mm vertically and 0.16 mm horizontally. Standard deviation of tilt was 1.30 degrees vertically and 0.90 degrees horizontally. Tilt and decentration are proportional to each other. Vaulting, the distance between the crystalline lens and the IOL, was constant over a period of 24 months, ranging from 0.2 to 0.8 mm, depending primarily on the radius of curvature of the crystalline lens. A geometric model for this dependence was formulated. CONCLUSION: Phakic IOLs with iris fixation can be positioned in the eye with submillimeter precision. Axial position of iris-fixated phakic IOLs over time is excellent. Axial position and vaulting can be predicted when the radius of curvature of the crystalline lens is known. The IOL behaves as if mounted slightly above a sphere-the anterior surface of the crystalline lens.

Biometry↗
PubMed2005

Surgeon offsets and dynamic eye movements in laser refractive surgery.

PURPOSE: To determine the amount of static and dynamic pupil decentrations that occur during laser refractive surgery. SETTING: The Center of Visual Science and the Department of Ophthalmology, University of Rochester, Rochester, New York, USA. METHODS: The surgeon's accuracy in aligning the pupil center with the laser center axis was measured when engaging the eye-tracker in 17 eyes receiving conventional laser in situ keratomileusis (LASIK) procedures (Technolas 217z; Bausch & Lomb). Eye movements were measured subsequently during the treatment in 10 eyes using a pupil camera operating at 50 Hz. Temporal power spectra were calculated from the eye movement measurements. RESULTS: The mean pupil misalignment by the surgeon at the beginning of the procedure was 206.1 microm +/- 80.99 (SD) (with respect to the laser center). The laser center was typically misaligned below (inferiorly) and to the left (nasally and temporally in left and right eyes, respectively) of the pupil [corrected] center. Small amounts of cyclotorsion were observed during the ablation (<2 degrees). The mean magnitude of dynamic pupil decentration from the laser center during treatment was 227.0 +/- 44.07 microm. The mean standard deviation of eye movements was 65.7 +/- 25.64 microm. Temporal power spectra calculated from the horizontal and vertical changes in eye position during the ablation were similar. Ninety-five percent of the total power of the eye movements was contained in temporal frequencies up to 1 Hz, on average, in both directions. CONCLUSIONS: Most eye movements during LASIK are slow drifts in fixation. An eye-tracker with a 1.4 Hz closed-loop bandwidth could compensate for most eye movements in conventional or customized ablations.

Calibration↗
PubMed1995

The effect of globe fixation on ablation zone centration in photorefractive keratectomy.

PURPOSE: For optimal vision, the ablation zone in photorefractive keratectomy should be centered over the entrance pupil. During ablation, the globe can be immobilized by the surgeon, with a suction ring around the corneoscleral limbus. Alternatively, the globe can be immobilized by patient fixation on a target, unassisted by the surgeon. We investigated which method results in better centration of the ablation zone over the entrance pupil, by using an objective, mathematical method to determine the ablation zone center. METHODS: Forty-eight eyes from 48 patients who underwent photorefractive keratectomy by the two techniques were studied retrospectively. The centers of the ablation zones were objectively determined by a weighted center of mass algorithm applied to the preoperative minus postoperative difference maps. The validity of the objective method was confirmed by comparison to subjective estimates of ablation zone centers made by independent human observers. RESULTS: The 19 eyes treated by surgeon fixation had an average decentration of the ablation zone of 0.63 +/- 0.31 mm (range, 0.01 to 1.00 mm), and the 29 eyes treated by patient fixation had an average decentration of 0.41 +/- 0.23 mm (range, 0.11 to 1.18 mm) (P = .027). CONCLUSIONS: The center of the ablation zone can be determined mathematically from the topographic map, to avoid observer bias. In this study, unassisted patient fixation during photorefractive keratectomy produced more accurate centration of the ablation zone than did surgeon fixation and has the potential for maximizing the quality of vision postoperatively.

Algorithms↗
PubMed1987

Cardiac transplantation: first-year experience in a community hospital.

The issue of decentralizing heart transplant services, formerly restricted to a few large medical centers, is currently under review by federal and state governments. We present the results of the first year of cardiac transplantation at a 385-bed community hospital. Twelve patients were selected according to generally accepted criteria from a pool of 24 referrals, all from within 75 miles of our institution. All patients were in New York Heart Association Class IV preoperatively. The one-year survival rate was found to be 82%, which is equivalent to that reported by established centers. All surviving patients were fully rehabilitated. Rates of infection and rejection were lower than expected, and costs were about half the national average. This series, in all likelihood, tests the limits to which the decentralization of cardiac transplant services can be taken. We conclude that cardiac transplantation can be accomplished at a community hospital with results, even for the first patients undergoing transplantation, comparable to those obtained by established programs at major medical centers.

Adult↗
PubMed2000

Regulation of division of labour between cognitive systems controlling action.

The brain has evolved a division of labour amongst component systems which link different sorts of processing with precise actions. Debate is over centralized versus decentralized control at different processing levels, from cognitive systems to motor-control systems. With simultaneous activation of alternative expert systems which link (a) picture-processing with drawing and (b) reading with writing, decentralized modelling predicted both the averaging of action-production times and additive effects of neural noise. Such modelling has the advantage of being able to measure the cost of regulation both within and between systems, in a common metric of performance variability. That commonality strengthens the trend to regard the brain as a distributed super-system with a great deal of regulation done towards the output end.

Adult↗
PubMed2000

Auto-tuning of TITO decoupling controllers from step tests

This paper considers auto-tuning of simple lead-lag decoupler plus decentralized PI/PID controllers for effective control of two-input and two-output (TITO) processes. A new robust identification method from step tests is presented first for SISO processes and then sequentially applied to TITO processes. The resulting 1st-order plus dead-time model is used for decoupler design and the 2nd-order one is used for decentralized PID sequential tuning. The simulation is given for illustration of the proposed tuning.

Journal Article↗
PubMed2003

Trauma care systems in Spain.

Trauma care systems in Spain are provided by the Nacional Health Service in a decentralized way by the seventeen autonomous communities whose process of decentralization was completed in January 2002. Its organisation is similar in all of them. Public sector companies of sanitary emergencies look after the health of citizens in relation to medical and trauma emergencies with a wide range of up to date resources both technical and human. In the following piece there is a description of the emergency response teams divided into ground and air that are responsible for the on site care of the patients in coordination with other public services. They also elaborate the prehospital clinical history that is going to be a valuable piece of information for the teams that receive the patient in the Emergency Hospital Unit (EHU). From 1980 to 1996 the mortality rate per 10.000 vehicles and the deaths per 1.000 accidents dropped significantly: in 1980 6.4 and 96.19% and in 1996, 2.8 and 64.06% respectively. In the intrahospital organisation there are two differentiated areas to receive trauma patients the casualty department and the EHU. In the EHU the severe and multiple injured patients are treated by the emergency hospital doctors; first in the triage or resuscitation areas and after when stabilised they are passed too the observation area or to the Intensive Care Unit (ICU) and from there the EHU or ICU doctors call the appropriate specialists. There is a close collaboration and coordination between the orthopaedic surgeon the EHU doctors and the other specialists surgeons in order to comply with treatment prioritization protocols. Once the patient has been transferred an entire process of assistance continuity is developed based on interdisciplinary teams formed in the hospital from the services areas involved in trauma assistance and usually coordinated by the ICU doctors. There is also mentioned the assistance registry of trauma patients, the ICU professional training in the ATLS and the future guidelines for trauma care in the ICU based on epidemiological studies carried out in both the North Spanish Group and the Southern one to promote development and improvement in several areas.

Accidents, Traffic↗
PubMed1987

Nerve crossover techniques for urinary bladder reinnervation: animal and human cadaver studies.

Interruption of spinal pathways integrating central and peripheral bladder control mechanisms will result in neurogenic bladder dysfunction. If central pathways could be restored to the decentralized bladder through a microneural reconstructive technique a return of useful function might be achieved. This anatomical study describes the nerve crossover techniques used in human cadaver dissections for connecting intercostal nerves to sacral roots intraspinally. The techniques were modified from and compared to similar procedures used in an animal model where adjacent extradural roots were connected through a nerve graft. We have shown previously that the unilaterally decentralized bladder of the cat can be recentralized after a nerve crossover procedure. If additional laboratory studies can document return of useful bladder function we anticipate that selected patients may benefit from similar nerve crossover techniques to bypass a spinal cord lesion to recentralize the bladder.

Animals↗
PubMed1985

Bladder and urethral function and supersensitivity to subcutaneously administered bethanechol in cats with chronic cauda equina lesions.

The failure of bethanechol chloride to induce voiding in patients with neurogenic bladder, despite a positive bethanechol test, is being reported more frequently. An experimental model was designed in the cat to study the response of the bladder and urethra to subcutaneous and intraarterial bethanechol after complete and partial sacral decentralization. Complete sacral rhizotomy abolished the micturition reflex. Basal urethral perfusion pressure was not affected by complete sacral rhizotomy and a significant part of this basal urethral pressure remained sympathetically mediated. However, the urethral constriction response to bladder filling was lost in half the cats with complete lesions. Bladder and urethral supersensitivity to bethanechol chloride in cats with complete lesions was characterized by a shift to the left of the i.a. dose-response curve, and by the presence of responses to doses of s.c. bethanechol chloride which are subthreshold in normal cats. The urethra also showed exaggerated constriction responses to i.a. and s.c. bethanechol. After complete lesions a part of the bladder and urethral responses to s.c. bethanechol was adrenergically mediated and exerted through the vesicourethral short neuron system. The rest of the response was due to stimulation of urethral muscarinic receptors. Partial sacral lesions were compatible with a micturition reflex and the urethra retained its reflex response to bladder distension. After partial decentralization the bladder and urethra also showed responses to subthreshold doses of s.c. bethanechol. While the bladder response to s.c. bethanechol did not show a significant adrenergic component in cats with partial lesions, most of the urethral response was sympathetically mediated. In conclusion, complete cauda equina lesions result in an areflexic detrusor with frequent loss of the urethral responsiveness to bladder filling. Urethral supersensitivity to s.c. bethanechol might be responsible for a non-voiding outcome after bethanechol injection in patients with complete cauda equina lesions, despite a positive bethanechol test. Because the detrusor reflex is preserved and the urethra is less supersensitive to bethanechol after partial cauda equina lesions, these may represent a better indication for bethanechol therapy than do complete ones.

Animals↗
PubMed1983

Bladder and ureteral pressure relationships in nonhuman primates.

Bladder pressures during filling are precisely paralleled by ureteral resistance to perfusion. The pressure relationships are identical in normal, spinal and decentralized nonhuman primates, none of which had vesicoureteral reflux. Intravesical and thus intraureteral pressures are higher in animals with neurological lesions, particularly decentralization.

Animals↗
PubMed2006

Adaptations of peripheral vasoconstrictor pathways after spinal cord injury.

The consequences of spinal cord injury on the function of sympathetic pathways in the periphery have generally been ignored. We discuss two types of plasticity that follow disruption of sympathetic pathways in rats . The first relates to the partial denervation of sympathetic ganglia that would follow the loss of some preganglionic neurones. Sprouting of residual connections rapidly reinnervates many postganglionic neurones, restoring functional transmission within a few weeks, but other neurones may be permanently decentralized. Some of the new functional connections may generate inappropriate pathways leading to abnormal reflexes . The second type of plasticity concerns the markedly enhanced and prolonged contractile responses to nerve activity in arterial vessels to which ongoing sympathetic activity has been reduced or silenced following spinal cord transection or ganglion decentralization. In a cutaneous artery (the rat tail artery), the mechanisms underlying this arterial hyperreactivity differ from those in the splanchnic arteries (the rat mesenteric artery). In the former, hyperreactivity is mainly postjunctional but independent of changes in alpha1-adrenoceptor sensitivity, whereas the increased responsiveness in the latter vessels can be attributed to a greater responsiveness to alpha1-adrenoceptor activation. There are enough data from humans to suggest that both of these novel findings in experimental animals are likely to apply after spinal cord injury and contribute to autonomic dysreflexia .

Animals↗
PubMed2002

Progression of keratoconus assessed by fourier analysis of videokeratography data.

OBJECTIVE: To quantitatively document changes in corneal refractive parameters in relation to the progression of keratoconus over years. DESIGN: Retrospective observational case series. PARTICIPANTS: Eighty-five eyes of 64 patients with keratoconus who had undergone videokeratography examinations at least twice with an interval of 1 year or longer between each examination. METHODS: By means of Fourier series harmonic analysis, topography data were decomposed into spherical component, regular astigmatism, decentration component, and higher order irregularity. MAIN OUTCOME MEASURES: Change rate of each parameter per year was calculated by use of the least squares method. RESULTS: All four refractive parameters were significantly larger in the keratoconic eyes than in the age-matched normal controls (P < 0.001, Student's t test). The yearly rate of change was significantly positive for spherical component (P = 0.008) and higher order irregular astigmatism (P = 0.015) but not for the regular astigmatism and decentration component. In eyes that showed apparent progression on color-coded maps, spherical component showed a significantly positive change rate per year (P = 0.002), but other parameters did not. In eyes without apparent progression, the yearly change rate of higher order irregular astigmatism was significantly larger than zero (P = 0.049). CONCLUSIONS: Keratoconus progression over years was quantitatively described. It was indicated that spherical equivalent is a manifest indicator for the apparent progression of keratoconus, and irregular astigmatism increases along with the natural course of the disease.

Adolescent↗
PubMed1991

Changes in corneal topography after excimer laser photorefractive keratectomy for myopia.

Computer-assisted analysis of corneal topography was performed in 17 normally sighted human eyes during the first year after excimer laser photorefractive keratectomy (PRK) for myopia. Laser ablation of the central cornea produced an optical zone with a smooth power transition to the peripheral cornea. Decentration of the ablation was noted in some eyes (less than 0.5 mm in 3 eyes, 0.5 to 1.0 mm in 10 eyes, 1 to 1.5 mm in 3 eyes, and 2.1 mm in 1 eye), suggesting that careful alignment of the laser beam is critical. Improved methods to align the ablation within the center of the entrance pupil are needed. In 12 of 17 eyes, the topographic pattern appeared to stabilize between 3 and 7 months after PRK. In the remaining five eyes, central ablation power changed by more than 0.5 diopters (D) between the 6- and 12-month examinations. Regression was more common and more pronounced in eyes with intended corrections more than 5 D, whereas the majority of eyes with intended corrections of 5 D or less showed good correspondence between the final change in central ablation power and the attempted correction. Two eyes had a loss of at least two lines of best spectacle-corrected visual acuity that was attributable to irregular astigmatism, decentration of the ablation, and/or corneal opacification.

Adult↗
PubMed1994

Corneal topographic analysis after excimer photorefractive keratectomy.

BACKGROUND: A 2-year experience with corneal topography after photorefractive keratectomy (PRK) is reported, specifically reviewing the correlation of surface regularity index versus best spectacle-corrected visual acuity as a function of various ablation patterns. Centration and stability issues also are discussed. METHODS: Excimer laser PRK for myopia was performed on 502 consecutive eyes. Corneal topographic analysis was performed at the 1-, 3-, 6-, and 12-month postoperative follow-up visits. In all patients, PRK was performed with an argon fluoride laser, and a topographic analysis was done. RESULTS: Topographic analysis at the first postoperative month was useful for determining decentration of the optical zone. The mean decentration from the pupillary center for all eyes was 0.34 mm. Four main patterns of ablation were noted by subtraction analysis. At the 1-month postoperative examination, a "uniform" ablation was present in 44% of eyes, "keyhole" ablations were present in 12% of eyes, "semicircular" ablations were present in 18% of eyes, and an unusual "central island" was present in the remaining 26% of eyes. However, on subsequent follow-up the central islands tended to resolve with time. At 3 months postoperatively, 18% of eyes in that group showed a central island, 8% showed a central island at 6 months, and only 2% of eyes showed a central island at the 12-month postoperative visit. Correlation of central island topography with visual acuity and progressive hyperopia are discussed. CONCLUSIONS: Corneal topography is essential for evaluating surface changes after excimer PRK. The surface regularity index is a good indicator of best spectacle-corrected visual acuity and is used to evaluate irregular astigmatism after PRK. Central island topographies are correlated with poor initial visual rehabilitation. Long-term stability issues are answered with continued topographic follow-up. Understanding corneal hydration changes between the central and peripheral cornea may help us understand the etiology of central islands.

Cornea↗