Simon Dean | Faculdade de Ciências Sociais e Humanas - Universidade Nova de Lisboa (original) (raw)

Papers by Simon Dean

Clinical and Experimental Ophthalmology, 2001

Keratoconus is a relatively common, bilateral, noninflammatory corneal ectasia.The aetiology of t... more Keratoconus is a relatively common, bilateral, noninflammatory corneal ectasia.The aetiology of this condition is probably multifactorial, or it represents the final common pathway for a variety of different pathological processes. Although a familial history is present only in a minority of cases, one of the major aetiological factors is certainly genetic. This is evidenced by: the condition's familial inheritance; its discordance between monozygotic and dizygotic twins; and its association with other known genetic disorders such as Down's and Marfan's syndromes. In the keratoconic cornea, a possible genetic predisposition to increased sensitivity to apoptotic mediators by keratocytes has also been hypothesized. Differences in prevalence between ethnic groups have been identified. Recent advances in computerized topographic diagnostic techniques for keratoconus, including forme fruste keratoconus, enables higher accuracy in delineating abnormal from normal, and helps define study populations for genetic linkage studies. However, genetic heterogeneity and the phenotypic diversity of keratoconus means that genetic analysis continues to be a complex process. None the less, it is foreseeable that over the next decade, improved diagnostic techniques, in combination with molecular genetics, may reveal conclusive data on the precise nature of the genetic inheritance of keratoconus in specific populations.This review considers the evidence that suggests keratoconus is primarily an inherited condition, and examines research strategies aimed at unveiling the genetic predisposition, and the enigma of environmental influences on its phenotypic expression.

Drug Safety, 2002

Corticosteroids, used prudently, are one of the most potent and effective modalities available in... more Corticosteroids, used prudently, are one of the most potent and effective modalities available in the treatment of ocular inflammation. However, they can produce a plethora of adverse ocular and systemic events. In order to optimise and target drug delivery, whilst minimising systemic adverse effects, a diverse range of local ophthalmic preparations and delivery techniques have been developed. Topical drops and ointments remain the primary methods for administration of ocular corticosteroids. However, ocular penetration of topical corticosteroid drops depends upon drug concentration, chemical formulation of corticosteroid, and composition of the vehicle, therefore, apparently small modifications in preparations can produce a more than 20-fold difference in intraocular drug concentration. Periocular injections of corticosteroids continue to have a useful, but limited, therapeutic role and longer acting, intraocular delayed-release devices are in early clinical studies. Although newer corticosteroids with lesser pressure elevating characteristics have been developed, corticosteroid-induced ocular hypertension and glaucoma continue to be significant risks of local and systemic administration. Posterior subcapsular cataract, observed following as little as 4 months topical corticosteroids use, is thought to be due to covalent binding of corticosteroid to lens protein with subsequent oxidation. Inappropriate use of topical corticosteroid in the presence of corneal infections also continues to be a cause of ocular morbidity. Other risks of locally administered ophthalmic corticosteroids include: tear-film instability, epithelial toxicity, crystalline keratopathy, decreased wound strength, orbital fat atrophy, ptosis, limitation of ocular movement, inadvertent intraocular injection, and reduction in endogenous cortisol. This extensive review assesses the therapeutic benefits of locally administered ocular corticosteroids in the context of the risks of adverse effects.

Clinical and Experimental Ophthalmology, 2004

Purpose: To analyse five cases of iridocorneal endothelial (ICE) syndrome and describe the micros... more Purpose: To analyse five cases of iridocorneal endothelial (ICE) syndrome and describe the microstructural characteristics observed by in vivo confocal microscopy.

Clinical and Experimental Ophthalmology, 2001

Keratoconus is a relatively common, bilateral, noninflammatory corneal ectasia.The aetiology of t... more Keratoconus is a relatively common, bilateral, noninflammatory corneal ectasia.The aetiology of this condition is probably multifactorial, or it represents the final common pathway for a variety of different pathological processes. Although a familial history is present only in a minority of cases, one of the major aetiological factors is certainly genetic. This is evidenced by: the condition's familial inheritance; its discordance between monozygotic and dizygotic twins; and its association with other known genetic disorders such as Down's and Marfan's syndromes. In the keratoconic cornea, a possible genetic predisposition to increased sensitivity to apoptotic mediators by keratocytes has also been hypothesized. Differences in prevalence between ethnic groups have been identified. Recent advances in computerized topographic diagnostic techniques for keratoconus, including forme fruste keratoconus, enables higher accuracy in delineating abnormal from normal, and helps define study populations for genetic linkage studies. However, genetic heterogeneity and the phenotypic diversity of keratoconus means that genetic analysis continues to be a complex process. None the less, it is foreseeable that over the next decade, improved diagnostic techniques, in combination with molecular genetics, may reveal conclusive data on the precise nature of the genetic inheritance of keratoconus in specific populations.This review considers the evidence that suggests keratoconus is primarily an inherited condition, and examines research strategies aimed at unveiling the genetic predisposition, and the enigma of environmental influences on its phenotypic expression.

Nature Geoscience, 2011

During subduction, weak, unlithified sediments are scraped off the down-going plate and accumulat... more During subduction, weak, unlithified sediments are scraped off the down-going plate and accumulate near the subduction trench axis. The weak nature of the sediments usually impedes the propagation of fault rupture during an earthquake. However, measurements of slip during the 2004 Sumatra-Andaman Mw 9.2 earthquake show that fault rupture propagatedupdip, extending unusually close to the subduction trench, in the southern part of the rupture area. Here we present seismic reflection images of the southern part of the 2004 Sumatra-Andaman earthquake rupture area. We show that sedimentary strata, greater than 4km in thickness, form coherent blocks that have been thrust onto the continental margin during subduction. The blocks form a 130-km-wide plateau overlying the seismogenic zone and the plate boundary megathrust lies near to the base of the sediments. The sediments consist of the Nicobar and Bengal Fan turbidites and exhibit strong internal cohesion. We suggest that dewatering and lithification of the sediments during burial made them unusually competent and strong, thus enabling rupture during the 2004 earthquake to propagate beneath the plateau, close to the Sunda Trench. Extending fault rupture so close to the trench, and thus further seaward, may have enhanced the tsunami hazard by displacing a greater thickness of water.

A series of linked marine and land studies have recently targeted the Sumatra subduction zone, fo... more A series of linked marine and land studies have recently targeted the Sumatra subduction zone, focusing on the 2004 and 2005 plate boundary earthquake ruptures in Indonesia. A collaborative research effort by scientists from the United Kingdom (UK Sumatra Consortium), Indonesia, United States, France, and Germany is focusing on imaging the crustal structure of the margin to examine controls on along-strike and updip earthquake rupture propagation. The fundamental science objective is to examine how margin architecture and properties control earthquake rupture location and propagation. The project collected extensive geophysical, geological, and seismological data across the offshore and onshore parts of the subduction zone of north central Sumatra (Figures 1 and 2). Offshore data collection within the project included the largest research vessel exchange program undertaken to date, involving an exchange of research vessel time between countries to maximize efficiency. The main surveys of the project spanned two segment boundaries of the subduction zone (Figure 1): between the 2004 and 2005 ruptures at Simeulue Island, and at the southern limit of the 2005 rupture, adjacent to a segment that ruptured in 1935, at the Nias and Batu islands. The extensive geological and geophysical data examine variations, at a range of scales, in seismicity, fore-arc deformation, plate boundary properties, lithospheric structure, and sedimentary properties and processes.

Geophysics, 1999

Reservoirs with thickness less than the seismic wavelength can still contain significant amounts ... more Reservoirs with thickness less than the seismic wavelength can still contain significant amounts of hydrocarbons. Such layers exhibit a tuning effect which involves the interference of reflected waves from the top and bottom of the reservoir. Natural fractures in such reservoirs can play an important role in determining fluid flow, which makes the density and orientation of fractures of great interest. In the presence of one or more sets of aligned vertical fractures, the amplitude of reflected waves at nonzero offset varies with azimuth; hence, the tuning effect will vary with azimuth. For wavelengths much greater than typical fracture spacing, equivalent medium theory allows such a vertically fractured layer to be modeled as a monoclinic layer with a plane of mirror symmetry parallel to the layer. The variation in reflection and transmission coefficients with incidence and azimuthal angle for a thin vertically fractured layer can be

Geophysical Prospecting, 2001

Geophysics, 1999

Reservoirs with thickness less than the seismic wavelength can still contain significant amounts ... more Reservoirs with thickness less than the seismic wavelength can still contain significant amounts of hydrocarbons. Such layers exhibit a tuning effect which involves the interference of reflected waves from the top and bottom of the reservoir. Natural fractures in such reservoirs can play an important role in determining fluid flow, which makes the density and orientation of fractures of great interest. In the presence of one or more sets of aligned vertical fractures, the amplitude of reflected waves at nonzero offset varies with azimuth; hence, the tuning effect will vary with azimuth. For wavelengths much greater than typical fracture spacing, equivalent medium theory allows such a vertically fractured layer to be modeled as a monoclinic layer with a plane of mirror symmetry parallel to the layer. The variation in reflection and transmission coefficients with incidence and azimuthal angle for a thin vertically fractured layer can be

Clinical and Experimental Ophthalmology, 2001

Keratoconus is a relatively common, bilateral, noninflammatory corneal ectasia.The aetiology of t... more Keratoconus is a relatively common, bilateral, noninflammatory corneal ectasia.The aetiology of this condition is probably multifactorial, or it represents the final common pathway for a variety of different pathological processes. Although a familial history is present only in a minority of cases, one of the major aetiological factors is certainly genetic. This is evidenced by: the condition's familial inheritance; its discordance between monozygotic and dizygotic twins; and its association with other known genetic disorders such as Down's and Marfan's syndromes. In the keratoconic cornea, a possible genetic predisposition to increased sensitivity to apoptotic mediators by keratocytes has also been hypothesized. Differences in prevalence between ethnic groups have been identified. Recent advances in computerized topographic diagnostic techniques for keratoconus, including forme fruste keratoconus, enables higher accuracy in delineating abnormal from normal, and helps define study populations for genetic linkage studies. However, genetic heterogeneity and the phenotypic diversity of keratoconus means that genetic analysis continues to be a complex process. None the less, it is foreseeable that over the next decade, improved diagnostic techniques, in combination with molecular genetics, may reveal conclusive data on the precise nature of the genetic inheritance of keratoconus in specific populations.This review considers the evidence that suggests keratoconus is primarily an inherited condition, and examines research strategies aimed at unveiling the genetic predisposition, and the enigma of environmental influences on its phenotypic expression.

Drug Safety, 2002

Corticosteroids, used prudently, are one of the most potent and effective modalities available in... more Corticosteroids, used prudently, are one of the most potent and effective modalities available in the treatment of ocular inflammation. However, they can produce a plethora of adverse ocular and systemic events. In order to optimise and target drug delivery, whilst minimising systemic adverse effects, a diverse range of local ophthalmic preparations and delivery techniques have been developed. Topical drops and ointments remain the primary methods for administration of ocular corticosteroids. However, ocular penetration of topical corticosteroid drops depends upon drug concentration, chemical formulation of corticosteroid, and composition of the vehicle, therefore, apparently small modifications in preparations can produce a more than 20-fold difference in intraocular drug concentration. Periocular injections of corticosteroids continue to have a useful, but limited, therapeutic role and longer acting, intraocular delayed-release devices are in early clinical studies. Although newer corticosteroids with lesser pressure elevating characteristics have been developed, corticosteroid-induced ocular hypertension and glaucoma continue to be significant risks of local and systemic administration. Posterior subcapsular cataract, observed following as little as 4 months topical corticosteroids use, is thought to be due to covalent binding of corticosteroid to lens protein with subsequent oxidation. Inappropriate use of topical corticosteroid in the presence of corneal infections also continues to be a cause of ocular morbidity. Other risks of locally administered ophthalmic corticosteroids include: tear-film instability, epithelial toxicity, crystalline keratopathy, decreased wound strength, orbital fat atrophy, ptosis, limitation of ocular movement, inadvertent intraocular injection, and reduction in endogenous cortisol. This extensive review assesses the therapeutic benefits of locally administered ocular corticosteroids in the context of the risks of adverse effects.

Clinical and Experimental Ophthalmology, 2004

Purpose: To analyse five cases of iridocorneal endothelial (ICE) syndrome and describe the micros... more Purpose: To analyse five cases of iridocorneal endothelial (ICE) syndrome and describe the microstructural characteristics observed by in vivo confocal microscopy.

Clinical and Experimental Ophthalmology, 2001

Keratoconus is a relatively common, bilateral, noninflammatory corneal ectasia.The aetiology of t... more Keratoconus is a relatively common, bilateral, noninflammatory corneal ectasia.The aetiology of this condition is probably multifactorial, or it represents the final common pathway for a variety of different pathological processes. Although a familial history is present only in a minority of cases, one of the major aetiological factors is certainly genetic. This is evidenced by: the condition's familial inheritance; its discordance between monozygotic and dizygotic twins; and its association with other known genetic disorders such as Down's and Marfan's syndromes. In the keratoconic cornea, a possible genetic predisposition to increased sensitivity to apoptotic mediators by keratocytes has also been hypothesized. Differences in prevalence between ethnic groups have been identified. Recent advances in computerized topographic diagnostic techniques for keratoconus, including forme fruste keratoconus, enables higher accuracy in delineating abnormal from normal, and helps define study populations for genetic linkage studies. However, genetic heterogeneity and the phenotypic diversity of keratoconus means that genetic analysis continues to be a complex process. None the less, it is foreseeable that over the next decade, improved diagnostic techniques, in combination with molecular genetics, may reveal conclusive data on the precise nature of the genetic inheritance of keratoconus in specific populations.This review considers the evidence that suggests keratoconus is primarily an inherited condition, and examines research strategies aimed at unveiling the genetic predisposition, and the enigma of environmental influences on its phenotypic expression.

Nature Geoscience, 2011

During subduction, weak, unlithified sediments are scraped off the down-going plate and accumulat... more During subduction, weak, unlithified sediments are scraped off the down-going plate and accumulate near the subduction trench axis. The weak nature of the sediments usually impedes the propagation of fault rupture during an earthquake. However, measurements of slip during the 2004 Sumatra-Andaman Mw 9.2 earthquake show that fault rupture propagatedupdip, extending unusually close to the subduction trench, in the southern part of the rupture area. Here we present seismic reflection images of the southern part of the 2004 Sumatra-Andaman earthquake rupture area. We show that sedimentary strata, greater than 4km in thickness, form coherent blocks that have been thrust onto the continental margin during subduction. The blocks form a 130-km-wide plateau overlying the seismogenic zone and the plate boundary megathrust lies near to the base of the sediments. The sediments consist of the Nicobar and Bengal Fan turbidites and exhibit strong internal cohesion. We suggest that dewatering and lithification of the sediments during burial made them unusually competent and strong, thus enabling rupture during the 2004 earthquake to propagate beneath the plateau, close to the Sunda Trench. Extending fault rupture so close to the trench, and thus further seaward, may have enhanced the tsunami hazard by displacing a greater thickness of water.

A series of linked marine and land studies have recently targeted the Sumatra subduction zone, fo... more A series of linked marine and land studies have recently targeted the Sumatra subduction zone, focusing on the 2004 and 2005 plate boundary earthquake ruptures in Indonesia. A collaborative research effort by scientists from the United Kingdom (UK Sumatra Consortium), Indonesia, United States, France, and Germany is focusing on imaging the crustal structure of the margin to examine controls on along-strike and updip earthquake rupture propagation. The fundamental science objective is to examine how margin architecture and properties control earthquake rupture location and propagation. The project collected extensive geophysical, geological, and seismological data across the offshore and onshore parts of the subduction zone of north central Sumatra (Figures 1 and 2). Offshore data collection within the project included the largest research vessel exchange program undertaken to date, involving an exchange of research vessel time between countries to maximize efficiency. The main surveys of the project spanned two segment boundaries of the subduction zone (Figure 1): between the 2004 and 2005 ruptures at Simeulue Island, and at the southern limit of the 2005 rupture, adjacent to a segment that ruptured in 1935, at the Nias and Batu islands. The extensive geological and geophysical data examine variations, at a range of scales, in seismicity, fore-arc deformation, plate boundary properties, lithospheric structure, and sedimentary properties and processes.

Geophysics, 1999

Reservoirs with thickness less than the seismic wavelength can still contain significant amounts ... more Reservoirs with thickness less than the seismic wavelength can still contain significant amounts of hydrocarbons. Such layers exhibit a tuning effect which involves the interference of reflected waves from the top and bottom of the reservoir. Natural fractures in such reservoirs can play an important role in determining fluid flow, which makes the density and orientation of fractures of great interest. In the presence of one or more sets of aligned vertical fractures, the amplitude of reflected waves at nonzero offset varies with azimuth; hence, the tuning effect will vary with azimuth. For wavelengths much greater than typical fracture spacing, equivalent medium theory allows such a vertically fractured layer to be modeled as a monoclinic layer with a plane of mirror symmetry parallel to the layer. The variation in reflection and transmission coefficients with incidence and azimuthal angle for a thin vertically fractured layer can be

Geophysical Prospecting, 2001

Geophysics, 1999

Reservoirs with thickness less than the seismic wavelength can still contain significant amounts ... more Reservoirs with thickness less than the seismic wavelength can still contain significant amounts of hydrocarbons. Such layers exhibit a tuning effect which involves the interference of reflected waves from the top and bottom of the reservoir. Natural fractures in such reservoirs can play an important role in determining fluid flow, which makes the density and orientation of fractures of great interest. In the presence of one or more sets of aligned vertical fractures, the amplitude of reflected waves at nonzero offset varies with azimuth; hence, the tuning effect will vary with azimuth. For wavelengths much greater than typical fracture spacing, equivalent medium theory allows such a vertically fractured layer to be modeled as a monoclinic layer with a plane of mirror symmetry parallel to the layer. The variation in reflection and transmission coefficients with incidence and azimuthal angle for a thin vertically fractured layer can be