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James Boyce

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Charles University, Prague

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Papers by James Boyce

Mathematical modeling of the forces between an intraocular lens and the capsule

Journal of Cataract and Refractive Surgery, 2002

To model the pressure relationship between an intraocular lens (IOL) and the capsular bag.Departm... more To model the pressure relationship between an intraocular lens (IOL) and the capsular bag.Department of Physics, Kings’ College, London University, London, United Kingdom.A mathematical model was made of the forces between the capsule and IOL showing that the pressure related to the local radius of curvature of the IOL at any given point. The local radius of curvature for round-edged and square-edged IOLs was measured from electron micrographs of the IOL profiles, and the corresponding pressure profiles were calculated and compared.The pressure between an IOL and the capsular bag was proportional to the quotient of the tension in the capsule divided by the local radius of curvature of the IOL, with a constant of proportionality that depended on the coefficient of friction between the capsule and IOL. Measuring the local radius of curvature of the 2 IOL types suggested a pressure increase of at least 69% ± 6% at the optic edge with the square-edged IOL.The mathematical model predicted that IOLs with square-edged optic profiles exerts higher pressure on the posterior capsule than IOLs with round-edged optic profiles. The higher pressure may form a physical barrier to lens epithelial cell migration onto the posterior capsule.

The Philippines: The Political Economy of Growth and Impoverishment in the Marcos Era

Journal of Asian Studies, 1994

... Louis Emmerij. The study of the Philippines by James Boyce is of more than usual interest. fo... more

A Preliminary Study of the Optimal Anesthesia Positioning for the Morbidly Obese Patient

Obesity Surgery, 2003

Background: Hypoxemia during the induction of general anesthesia for the morbidly obese patient i... more Background: Hypoxemia during the induction of general anesthesia for the morbidly obese patient is a major concern of anesthesiologists. The etiology of this pathophysiological problem is multifactorial, and patient positioning may be a contributing factor. The present study was designed to identify optimal patient positioning for the induction of general anesthesia that minimizes the risk of hypoxemia in these patients. Methods: 26 morbidly obese patients (body mass index - BMI 56±3) were randomly assigned to one of three positions for induction of anesthesia: 1) 30° Reverse Trendelenburg; 2) Supine-Horizontal; 3) 30° Back Up Fowler. Mask ventilation, full neuromuscular paralysis and direct laryngoscopy were performed. Any airway difficulties were noted. After endotracheal tube placement, subjects were ventilated for 5 minutes with 1% isoflurane in a mixture of 50% oxygen / 50% air and then disconnected from the ventilation circuit.The time required for capillary oxygen saturation (SaO2), as measured by pulse oximeter, to decline from 100% to 92% was noted and identified as the safe apnea period (SAP). Ventilation was then immediately re-established.The lowest SaO2 after resuming ventilation and the time from that nadir to an SaO2 of 97% were also recorded. Results: BMI and hip-waist ratios of patients in groups 1, 2 and 3 did not significantly differ. There were no differences in airway difficulties between the different groups. The SAP in groups 1, 2 and 3 was 178±55, 123±24 and 153±63 seconds, respectively. The SaO2 of patients in the reverse Trendelenburg position dropped the least and took the shortest time to recover to 97%. Conclusions: In morbidly obese patients, the 30° Reverse Trendelenburg position provided the longest SAP when compared to the 30° Back Up Fowler and Horizontal-Supine positions. Since on induction of general anesthesia morbidly obese patients may be difficult to mask ventilate and/or intubate, this extra time may preclude adverse sequelae resulting from hypoxemia. Therefore, Reverse Trendelenburg is recommended as the optimal position for induction.

External assistance and the peace process in El Salvador

World Development, 1995

External assistance has played a critical role in the Salvadoran peace process. Yet the prioritie... more External assistance has played a critical role in the Salvadoran peace process. Yet the priorities of the donors have often diverged from those of the Peace Accords. Moreover, several major external assistance actors -notably the international financial institutions -have failed to exercise "peace conditionality": they have not used formal performance criteria or informal policy dialogue to encourage the timely implementation of high-priority peace. programs and the mobilization of greater domestic resources for this purpose. These institutions have recently broadened their mandates to encompass military expenditure reduction and good "governance." While these concerns are particularly germane in countries emerging from civil war, the case of El Salvador demonstrates that they have yet to be fully incorporated into actual practice.

High-resolution direct-detection x-ray imagers

We report on a-Si direct detection x-ray image sensors with polycrystalline PbI2, and more recent... more We report on a-Si direct detection x-ray image sensors with polycrystalline PbI2, and more recently with HgI2. The arrays have 100 micron pixel size and, we study those aspects of the detectors that mainly determine the DQE, such as sensitivity, effective fill factor, dark current noise, noise power spectrum, and x-ray absorption. Line spread function data show that in the PbI2 arrays, most of the signal in the gap between pixels is collected, which is important for high,DQE. The leakage current noise agrees with the expected shot noise value with only a small enhancement at high bias voltages. The noise power spectrum under x-ray exposure is reported and compared to the spatial resolution information. The MTF is close to the ideal sinc function, but is reduced by the contribution of K-fluorescence in the PbI2 film for which we provide new experimental evidence. The role of noise power aliasing in the DQE and the effect of slight image spreading are discussed. Initial studies of HgI2 as the photoconductor material show very promising results with high x-ray sensitivity and low leakage current.

High Power Lasing in the IR Upgrade FEL at Jefferson Lab

We report on progress in commissioning the IR Upgrade facility at Jefferson Lab. Operation at hig... more We report on progress in commissioning the IR Upgrade facility at Jefferson Lab. Operation at high power has been demonstrated at 5.7 microns with over 8.5 kW of continuous power output, 10 kW for 1 second long pulses, and CW recirculated electron beam power of over 1.1 MW. We report on the features and limitations of the present design and report on the path to getting even higher powers.

Segmentation of MR images using neural nets

Image and Vision Computing, 1992

A two tier system for MR image segmentation is proposed. The first stage involves probabilistical... more A two tier system for MR image segmentation is proposed. The first stage involves probabilistically classifying the pixels of the input image based on second order grey level statistics obtained from the co-occurrence matrix. These probabilities then form the input to a multi-layer perceptron, allowing contextual constraints to be applied to local areas of the image thereby improving the spatial coherence of the classification.

Double-masked prospective ocular safety study of a lens epithelial cell antibody to prevent posterior capsule opacification

Journal of Cataract and Refractive Surgery, 2000

Purpose: To evaluate the intraocular safety of an immunoconjugate (MDX-RA) developed to prevent p... more

Public Debts and Private Assets: Explaining Capital Flight from Sub-Saharan African Countries

We investigate the determinants of capital flight from 30 sub-Saharan African countries, includin... more We investigate the determinants of capital flight from 30 sub-Saharan African countries, including 24 countries classified as severely indebted low-income countries, for the period 1970-1996. The econometric analysis reveals that external borrowing is positively and significantly related to capital flight, suggesting that to a large extent capital flight is debt-fueled. We estimate that for every dollar of external borrowing in the region, roughly 80 cents flowed back as capital flight in the same year. Capital flight also exhibits a high degree of persistence in the sense that past capital flight is correlated with current and future capital flight. The growth rate differential between the African country and its OECD trading partners is negatively related to capital flight. We also explore the effects of several other factors -inflation, fiscal policy indicators, the interest rate differential, exchange rate appreciation, financial development, and indicators of the political environment and governance. We discuss the implications of the results for debt relief and for policies aimed at preventing capital flight and attracting private capital held abroad.

Edge profile of commercially available square-edged intraocular lenses

Journal of Cataract and Refractive Surgery, 2008

PURPOSE: To analyze the sharpness of the posterior optic edge profile and edge thickness of intra... more

Comparison of posterior capsule opacification rates between hydrophilic and hydrophobic single-piece acrylic intraocular lenses

Journal of Cataract and Refractive Surgery, 2005

Purpose: To determine the effect of intraocular lens (IOL) material on the development of posteri... more

Effect of 1-piece and 3-piece AcrySof intraocular lenses on the development of posterior capsule opacification after cataract surgery

Journal of Cataract and Refractive Surgery, 2004

To evaluate the effect of 1-piece and 3-piece hydrophobic acrylic intraocular lenses (IOLs) on po... more

Edge profile of commercially available square-edged intraocular lenses

Journal of Cataract and Refractive Surgery, 2008

PURPOSE: To analyze the sharpness of the posterior optic edge profile and edge thickness of intra... more

The Effect of Posterior Capsule Opacification on Visual Function

To investigate how posterior capsule opacification (PCO) affects visual function in pseudophakic ... more To investigate how posterior capsule opacification (PCO) affects visual function in pseudophakic eyes. METHODS. One hundred and six eyes that had undergone uncomplicated phacoemulsification were recruited sequentially. Patients with surgical complications or other ocular disease were excluded. PCO was assessed by a digital retroillumination camera using a software program based on the analysis of texture in the image, and the percentage area within the central 3-mm zone of the posterior capsule was calculated. Visual function assessment included Early Treatment Diabetic Retinopathy Study (ETDRS) high-and low-contrast visual acuity, contrast sensitivity with the Pelli-Robson and CSV-1000 grating charts, and forward light-scatter by the direct-compensation method (van den Berg). RESULTS. The percentage PCO required for decline in highcontrast ETDRS was 78%; for low-contrast acuity and Pelli-Robson, 46%; for CSV-1000 contrast sensitivity, 38% to 51%; and for forward light-scatter, less than 1% PCO. CONCLUSIONS. Central PCO affects psychophysical test results with differing degrees of sensitivity. Forward light-scatter is the most sensitive, followed by contrast sensitivity and visual acuity. (Invest Ophthalmol Vis Sci. 2003;44:4665-4669)

POCOman: New system for quantifying posterior capsule opacification

To describe a new method of measuring posterior capsule opacification (PCO) and intraocular lens ... more

Comparison of posterior capsule opacification rates between hydrophilic and hydrophobic single-piece acrylic intraocular lenses

Journal of Cataract and Refractive Surgery, 2005

Purpose: To determine the effect of intraocular lens (IOL) material on the development of posteri... more

Effect of 1-piece and 3-piece AcrySof intraocular lenses on the development of posterior capsule opacification after cataract surgery

Journal of Cataract and Refractive Surgery, 2004

To evaluate the effect of 1-piece and 3-piece hydrophobic acrylic intraocular lenses (IOLs) on po... more

The Effect of Posterior Capsule Opacification on Visual Function

To investigate how posterior capsule opacification (PCO) affects visual function in pseudophakic ... more To investigate how posterior capsule opacification (PCO) affects visual function in pseudophakic eyes. METHODS. One hundred and six eyes that had undergone uncomplicated phacoemulsification were recruited sequentially. Patients with surgical complications or other ocular disease were excluded. PCO was assessed by a digital retroillumination camera using a software program based on the analysis of texture in the image, and the percentage area within the central 3-mm zone of the posterior capsule was calculated. Visual function assessment included Early Treatment Diabetic Retinopathy Study (ETDRS) high-and low-contrast visual acuity, contrast sensitivity with the Pelli-Robson and CSV-1000 grating charts, and forward light-scatter by the direct-compensation method (van den Berg). RESULTS. The percentage PCO required for decline in highcontrast ETDRS was 78%; for low-contrast acuity and Pelli-Robson, 46%; for CSV-1000 contrast sensitivity, 38% to 51%; and for forward light-scatter, less than 1% PCO. CONCLUSIONS. Central PCO affects psychophysical test results with differing degrees of sensitivity. Forward light-scatter is the most sensitive, followed by contrast sensitivity and visual acuity. (Invest Ophthalmol Vis Sci. 2003;44:4665-4669)

POCOman: New system for quantifying posterior capsule opacification

To describe a new method of measuring posterior capsule opacification (PCO) and intraocular lens ... more

Edge profile of commercially available square-edged intraocular lenses

Journal of Cataract and Refractive Surgery, 2008

To analyze the sharpness of the posterior optic edge profile and edge thickness of intraocular le... more To analyze the sharpness of the posterior optic edge profile and edge thickness of intraocular lenses (IOLs) marketed with a square-edged profile.Department of Ophthalmology, St. Thomas' Hospital, London, United Kingdom.Seventeen square-edged 20.0 diopter IOLs of different manufacture, design, and material were selected. After the environmental scanning electron microscopy technique was standardized, repeatability of the technique was tested. Posterior optic edges of all IOLs were scanned at a magnification of ×500. Local radii of curvature of the posterior optic edges were measured by purpose-designed software. Optic edge thickness was also measured from the electron micrographs.The repeatability of the scanning technique was excellent (±0.10 μm). The radius of curvature of posterior optic edges ranged from 7.6 to 23.1 μm. Hydrophilic acrylic IOLs (except the HumanOptics MC Microlens 611 MI-B and 1CU) had radii of curvatures more than 10.0 μm of the posterior optic edge compared with hydrophobic acrylic and silicone IOLs (<10.0 μm) except the Hoya AF-1 (19.9 μm). Alcon AcrySof single-piece (SN60WF), HumanOptics 1CU, and AMO Clariflex CLRFLXC IOLs had the thinnest optic edges in the hydrophobic, hydrophilic, and silicone groups, respectively.Commercially marketed square-edged IOLs differed in the sharpness of the posterior optic edge. Hydrophobic acrylic and silicone IOLs have sharper posterior optic square edge than most hydrophilic acrylic IOLs. This probably reflects difference in manufacturing techniques. Differences in posterior optic edge profile may explain variation in posterior capsule opacification performance with different IOLs and materials.

Mathematical modeling of the forces between an intraocular lens and the capsule

Journal of Cataract and Refractive Surgery, 2002

To model the pressure relationship between an intraocular lens (IOL) and the capsular bag.Departm... more To model the pressure relationship between an intraocular lens (IOL) and the capsular bag.Department of Physics, Kings’ College, London University, London, United Kingdom.A mathematical model was made of the forces between the capsule and IOL showing that the pressure related to the local radius of curvature of the IOL at any given point. The local radius of curvature for round-edged and square-edged IOLs was measured from electron micrographs of the IOL profiles, and the corresponding pressure profiles were calculated and compared.The pressure between an IOL and the capsular bag was proportional to the quotient of the tension in the capsule divided by the local radius of curvature of the IOL, with a constant of proportionality that depended on the coefficient of friction between the capsule and IOL. Measuring the local radius of curvature of the 2 IOL types suggested a pressure increase of at least 69% ± 6% at the optic edge with the square-edged IOL.The mathematical model predicted that IOLs with square-edged optic profiles exerts higher pressure on the posterior capsule than IOLs with round-edged optic profiles. The higher pressure may form a physical barrier to lens epithelial cell migration onto the posterior capsule.

The Philippines: The Political Economy of Growth and Impoverishment in the Marcos Era

Journal of Asian Studies, 1994

... Louis Emmerij. The study of the Philippines by James Boyce is of more than usual interest. fo... more

A Preliminary Study of the Optimal Anesthesia Positioning for the Morbidly Obese Patient

Obesity Surgery, 2003

Background: Hypoxemia during the induction of general anesthesia for the morbidly obese patient i... more Background: Hypoxemia during the induction of general anesthesia for the morbidly obese patient is a major concern of anesthesiologists. The etiology of this pathophysiological problem is multifactorial, and patient positioning may be a contributing factor. The present study was designed to identify optimal patient positioning for the induction of general anesthesia that minimizes the risk of hypoxemia in these patients. Methods: 26 morbidly obese patients (body mass index - BMI 56±3) were randomly assigned to one of three positions for induction of anesthesia: 1) 30° Reverse Trendelenburg; 2) Supine-Horizontal; 3) 30° Back Up Fowler. Mask ventilation, full neuromuscular paralysis and direct laryngoscopy were performed. Any airway difficulties were noted. After endotracheal tube placement, subjects were ventilated for 5 minutes with 1% isoflurane in a mixture of 50% oxygen / 50% air and then disconnected from the ventilation circuit.The time required for capillary oxygen saturation (SaO2), as measured by pulse oximeter, to decline from 100% to 92% was noted and identified as the safe apnea period (SAP). Ventilation was then immediately re-established.The lowest SaO2 after resuming ventilation and the time from that nadir to an SaO2 of 97% were also recorded. Results: BMI and hip-waist ratios of patients in groups 1, 2 and 3 did not significantly differ. There were no differences in airway difficulties between the different groups. The SAP in groups 1, 2 and 3 was 178±55, 123±24 and 153±63 seconds, respectively. The SaO2 of patients in the reverse Trendelenburg position dropped the least and took the shortest time to recover to 97%. Conclusions: In morbidly obese patients, the 30° Reverse Trendelenburg position provided the longest SAP when compared to the 30° Back Up Fowler and Horizontal-Supine positions. Since on induction of general anesthesia morbidly obese patients may be difficult to mask ventilate and/or intubate, this extra time may preclude adverse sequelae resulting from hypoxemia. Therefore, Reverse Trendelenburg is recommended as the optimal position for induction.

External assistance and the peace process in El Salvador

World Development, 1995

External assistance has played a critical role in the Salvadoran peace process. Yet the prioritie... more External assistance has played a critical role in the Salvadoran peace process. Yet the priorities of the donors have often diverged from those of the Peace Accords. Moreover, several major external assistance actors -notably the international financial institutions -have failed to exercise "peace conditionality": they have not used formal performance criteria or informal policy dialogue to encourage the timely implementation of high-priority peace. programs and the mobilization of greater domestic resources for this purpose. These institutions have recently broadened their mandates to encompass military expenditure reduction and good "governance." While these concerns are particularly germane in countries emerging from civil war, the case of El Salvador demonstrates that they have yet to be fully incorporated into actual practice.

High-resolution direct-detection x-ray imagers

We report on a-Si direct detection x-ray image sensors with polycrystalline PbI2, and more recent... more We report on a-Si direct detection x-ray image sensors with polycrystalline PbI2, and more recently with HgI2. The arrays have 100 micron pixel size and, we study those aspects of the detectors that mainly determine the DQE, such as sensitivity, effective fill factor, dark current noise, noise power spectrum, and x-ray absorption. Line spread function data show that in the PbI2 arrays, most of the signal in the gap between pixels is collected, which is important for high,DQE. The leakage current noise agrees with the expected shot noise value with only a small enhancement at high bias voltages. The noise power spectrum under x-ray exposure is reported and compared to the spatial resolution information. The MTF is close to the ideal sinc function, but is reduced by the contribution of K-fluorescence in the PbI2 film for which we provide new experimental evidence. The role of noise power aliasing in the DQE and the effect of slight image spreading are discussed. Initial studies of HgI2 as the photoconductor material show very promising results with high x-ray sensitivity and low leakage current.

High Power Lasing in the IR Upgrade FEL at Jefferson Lab

We report on progress in commissioning the IR Upgrade facility at Jefferson Lab. Operation at hig... more We report on progress in commissioning the IR Upgrade facility at Jefferson Lab. Operation at high power has been demonstrated at 5.7 microns with over 8.5 kW of continuous power output, 10 kW for 1 second long pulses, and CW recirculated electron beam power of over 1.1 MW. We report on the features and limitations of the present design and report on the path to getting even higher powers.

Segmentation of MR images using neural nets

Image and Vision Computing, 1992

A two tier system for MR image segmentation is proposed. The first stage involves probabilistical... more A two tier system for MR image segmentation is proposed. The first stage involves probabilistically classifying the pixels of the input image based on second order grey level statistics obtained from the co-occurrence matrix. These probabilities then form the input to a multi-layer perceptron, allowing contextual constraints to be applied to local areas of the image thereby improving the spatial coherence of the classification.

Double-masked prospective ocular safety study of a lens epithelial cell antibody to prevent posterior capsule opacification

Journal of Cataract and Refractive Surgery, 2000

Purpose: To evaluate the intraocular safety of an immunoconjugate (MDX-RA) developed to prevent p... more

Public Debts and Private Assets: Explaining Capital Flight from Sub-Saharan African Countries

We investigate the determinants of capital flight from 30 sub-Saharan African countries, includin... more We investigate the determinants of capital flight from 30 sub-Saharan African countries, including 24 countries classified as severely indebted low-income countries, for the period 1970-1996. The econometric analysis reveals that external borrowing is positively and significantly related to capital flight, suggesting that to a large extent capital flight is debt-fueled. We estimate that for every dollar of external borrowing in the region, roughly 80 cents flowed back as capital flight in the same year. Capital flight also exhibits a high degree of persistence in the sense that past capital flight is correlated with current and future capital flight. The growth rate differential between the African country and its OECD trading partners is negatively related to capital flight. We also explore the effects of several other factors -inflation, fiscal policy indicators, the interest rate differential, exchange rate appreciation, financial development, and indicators of the political environment and governance. We discuss the implications of the results for debt relief and for policies aimed at preventing capital flight and attracting private capital held abroad.

Edge profile of commercially available square-edged intraocular lenses

Journal of Cataract and Refractive Surgery, 2008

PURPOSE: To analyze the sharpness of the posterior optic edge profile and edge thickness of intra... more

Comparison of posterior capsule opacification rates between hydrophilic and hydrophobic single-piece acrylic intraocular lenses

Journal of Cataract and Refractive Surgery, 2005

Purpose: To determine the effect of intraocular lens (IOL) material on the development of posteri... more

Effect of 1-piece and 3-piece AcrySof intraocular lenses on the development of posterior capsule opacification after cataract surgery

Journal of Cataract and Refractive Surgery, 2004

To evaluate the effect of 1-piece and 3-piece hydrophobic acrylic intraocular lenses (IOLs) on po... more

Edge profile of commercially available square-edged intraocular lenses

Journal of Cataract and Refractive Surgery, 2008

PURPOSE: To analyze the sharpness of the posterior optic edge profile and edge thickness of intra... more

The Effect of Posterior Capsule Opacification on Visual Function

To investigate how posterior capsule opacification (PCO) affects visual function in pseudophakic ... more To investigate how posterior capsule opacification (PCO) affects visual function in pseudophakic eyes. METHODS. One hundred and six eyes that had undergone uncomplicated phacoemulsification were recruited sequentially. Patients with surgical complications or other ocular disease were excluded. PCO was assessed by a digital retroillumination camera using a software program based on the analysis of texture in the image, and the percentage area within the central 3-mm zone of the posterior capsule was calculated. Visual function assessment included Early Treatment Diabetic Retinopathy Study (ETDRS) high-and low-contrast visual acuity, contrast sensitivity with the Pelli-Robson and CSV-1000 grating charts, and forward light-scatter by the direct-compensation method (van den Berg). RESULTS. The percentage PCO required for decline in highcontrast ETDRS was 78%; for low-contrast acuity and Pelli-Robson, 46%; for CSV-1000 contrast sensitivity, 38% to 51%; and for forward light-scatter, less than 1% PCO. CONCLUSIONS. Central PCO affects psychophysical test results with differing degrees of sensitivity. Forward light-scatter is the most sensitive, followed by contrast sensitivity and visual acuity. (Invest Ophthalmol Vis Sci. 2003;44:4665-4669)

POCOman: New system for quantifying posterior capsule opacification

To describe a new method of measuring posterior capsule opacification (PCO) and intraocular lens ... more

Comparison of posterior capsule opacification rates between hydrophilic and hydrophobic single-piece acrylic intraocular lenses

Journal of Cataract and Refractive Surgery, 2005

Purpose: To determine the effect of intraocular lens (IOL) material on the development of posteri... more

Effect of 1-piece and 3-piece AcrySof intraocular lenses on the development of posterior capsule opacification after cataract surgery

Journal of Cataract and Refractive Surgery, 2004

To evaluate the effect of 1-piece and 3-piece hydrophobic acrylic intraocular lenses (IOLs) on po... more

The Effect of Posterior Capsule Opacification on Visual Function

To investigate how posterior capsule opacification (PCO) affects visual function in pseudophakic ... more To investigate how posterior capsule opacification (PCO) affects visual function in pseudophakic eyes. METHODS. One hundred and six eyes that had undergone uncomplicated phacoemulsification were recruited sequentially. Patients with surgical complications or other ocular disease were excluded. PCO was assessed by a digital retroillumination camera using a software program based on the analysis of texture in the image, and the percentage area within the central 3-mm zone of the posterior capsule was calculated. Visual function assessment included Early Treatment Diabetic Retinopathy Study (ETDRS) high-and low-contrast visual acuity, contrast sensitivity with the Pelli-Robson and CSV-1000 grating charts, and forward light-scatter by the direct-compensation method (van den Berg). RESULTS. The percentage PCO required for decline in highcontrast ETDRS was 78%; for low-contrast acuity and Pelli-Robson, 46%; for CSV-1000 contrast sensitivity, 38% to 51%; and for forward light-scatter, less than 1% PCO. CONCLUSIONS. Central PCO affects psychophysical test results with differing degrees of sensitivity. Forward light-scatter is the most sensitive, followed by contrast sensitivity and visual acuity. (Invest Ophthalmol Vis Sci. 2003;44:4665-4669)

POCOman: New system for quantifying posterior capsule opacification

To describe a new method of measuring posterior capsule opacification (PCO) and intraocular lens ... more

Edge profile of commercially available square-edged intraocular lenses

Journal of Cataract and Refractive Surgery, 2008

To analyze the sharpness of the posterior optic edge profile and edge thickness of intraocular le... more To analyze the sharpness of the posterior optic edge profile and edge thickness of intraocular lenses (IOLs) marketed with a square-edged profile.Department of Ophthalmology, St. Thomas' Hospital, London, United Kingdom.Seventeen square-edged 20.0 diopter IOLs of different manufacture, design, and material were selected. After the environmental scanning electron microscopy technique was standardized, repeatability of the technique was tested. Posterior optic edges of all IOLs were scanned at a magnification of ×500. Local radii of curvature of the posterior optic edges were measured by purpose-designed software. Optic edge thickness was also measured from the electron micrographs.The repeatability of the scanning technique was excellent (±0.10 μm). The radius of curvature of posterior optic edges ranged from 7.6 to 23.1 μm. Hydrophilic acrylic IOLs (except the HumanOptics MC Microlens 611 MI-B and 1CU) had radii of curvatures more than 10.0 μm of the posterior optic edge compared with hydrophobic acrylic and silicone IOLs (<10.0 μm) except the Hoya AF-1 (19.9 μm). Alcon AcrySof single-piece (SN60WF), HumanOptics 1CU, and AMO Clariflex CLRFLXC IOLs had the thinnest optic edges in the hydrophobic, hydrophilic, and silicone groups, respectively.Commercially marketed square-edged IOLs differed in the sharpness of the posterior optic edge. Hydrophobic acrylic and silicone IOLs have sharper posterior optic square edge than most hydrophilic acrylic IOLs. This probably reflects difference in manufacturing techniques. Differences in posterior optic edge profile may explain variation in posterior capsule opacification performance with different IOLs and materials.