Lens Flashcards
The Lens is specialized __epithelial/endothelial__ tissue that is responsible for fine-tuning the image that is projected on the __cornea/retina_____.
epithelial, retina
T/F Intraocular lens can be compared to a camera lens.
T
The lens must be transparent, have a higher refractive index than the medium in which it is suspended, and have refractive surfaces with the proper curvature to allow what to occur?
for the lens to fine-tune an image that is projected onto the retina
T/F The curvature of surfaces must not be variable to permit the optical system to focus on objects that are far or near.
False, curvature of surfaces must be variable
Disruption of the precise organization of the lens _fiber/protein__ cells or damage to the fiber/protein within them can destroy the _opaqueness/transparency__ of the lens, a process known as _cataract/pterygium__ formation.
fiber, proteins, transparency, cataract
The lens is formed from __two/three populations of specialized epithelial cells.
two
- cuboidal cells
- elongated fiber cells
On the anterior/posterior surface of the lens closest to the __cornea/iris__ is a sheet of __cuboidal/fiber__ cells, the lens epithelium.
anterior, cornea, cuboidal
The bulk of the lens consists of elongated _cuboidal/fiber__ cells.
fiber
T/F The lens capsule, an elastic extracellular matrix that surrounds the entire lens is secreted by the epithelial and superficial fiber cells.
True
Most epithelial cells __do/do not__ divide.
DO NOT
In the germanitive zone __near/away__ the equatorial margin of the lens epithelium/endothelium cells do/do not proliferate and do so slowly/quickly
near, epithelium, DO, slowly
T/F The junctions between the apical and basal ends of cells from the opposite sides of the lens are called the common junction.
False, they are called sutures.
Fiber cells __stop/start__ elongating when they reach the sutures and their basal ends __detach/attach__ from the capsule.
stop, detach
Mature/Young fiber cells are gradually buried deeper in the lens as successive generations of fibers elongate/shorten and differentiate
mature, elongate
Lens increases/decreases in size; synthesis ceases/continues just before organelle degradation.
increases, ceases
The components of mature fiber cells in the lens, must be much less stable than those in cells found in other parts of the body.
False, much more stable
The lens is suspended in the posterior/anterior of the eye by a band of inelastic/elastic microfibrils, the Zonules/Iris, which insert into the lens capsule near the equator.
anterior, inelastic, zonules
The zonule fibrils originate in the pigmented/nonpigmented layer of the ciliary/corneal epithelium, a tissue that is located just posterior to the iris.
non-pigmented, ciliary
T/F Changes in the tension applied to the zonules are responsible for the alterations in lens curvature during accommodation.
True
The refractive properties of the lens are the result of the high/low concentration of crystallins in the cytoplasm/nucleus of the lens fiber cells/wing cells and the curvature of the lens surfaces.
high, cytoplasm, fiber cells
Lens crystallins accumulate to concentrations that are ________higher than in typical cells.
a. 1x
b. 2x
c. 3x
d. 4x
c. 3x
The lower/higher concentration of crystallins give lens fiber cells a significantly lower/higher refractive index than the fluids around the lens.
higher, higher
T/F In younger individuals, refractive error is often caused by defects in the curvature or refractive index of the lens.
False, In younger individuals, refractive error is often caused by abnormalities in corneal curvature or the length of the globe, RARELY by defects in the curvature or refractive index of the lens.
Transparency depends on maximizing/minimizing light scattering and absorption.
minimizing
Pick the best answer, may pick more than one answer.
Light passes smoothly through the lens as a result of:
1. the regular structure of lens fibers
2. the absence of membrane-bound organelles
3. the small and uniform extracellular space between the fiber cells.
All three statements are correct
1. the regular structure of lens fibers 2. the absence of membrane-bound organelles 3. the small and uniform extracellular space between the fiber cells.
In young/older individuals, the human lens is nearly colorful/colorless.
young, colorless
The human lens absorbs _increasing/decreasing _ amounts of short/long wavelengths as it ages.
increasing, short
T/F Pseudophakia is the absence of the natural crystalline lens, either from natural causes or because it has been removed.
False, Aphakia
T/F Aphakia is the substitution of the natural crystalline lens with a synthetic lens.
False, Pseudophakia
Pseudophakic IOLs are used in cataract surgery/cornea surgery.
Cataract surgery
Congenital aphakia can be caused by a Hepatitis/Rubella infection in first 4/8/10 weeks of pregnancy.
Rubella, 4
can also be caused by a mutation in the PAX-6 gene
T/F Lens fiber differentiation depends on synthesis and accumulation of large amounts of crystallins.
True
As much as ____of the wet weight of the lens fiber cell can be accounted for by crystallins, a protein concentration that is approximately ___ higher than that in the cytoplasm of typical cells
a. 25%, 3x
b. 40%, 2x
c. 50%, 2x
d. 40%, 3x
d. 40%, 3x
Crystallins are classified into 2 categories:
1. Classical and Taxon-specific 2. Classical and Non-classical 3. Taxon-specific and Taxon-nonspecific 4. Type1 and Type 2
- Classical and Taxon-specific
T/F All vertebrae lenses accumulate the Classical crystallins, which consist of α-crystallin family and β/γ-crystallin superfamily.
True
Taxon-specific crystallins are functional/non-functional enzymes or proteins that are structurally similar/dissimilar to enzymes but that lack/contain enzymatic activity.
functional, similar, lack
T/F Adult human lenses DO produce taxon-specific crystallins,
False Adult human lenses DO NOT produce taxon-specific crystallins,
T/F The enzyme betaine-homocysteine methyltransferase is present at high levels in the embryonic nucleus, indicating that this enzyme serves as a taxon-specific crystallin during the early development of the human lens.
True because Adult human lenses DO NOT produce taxon-specific crystallins,
Human lenses express ___ α-crystallin genes.
a. 1
b. 2
c. 3
d. 4
b. 2, αA and αB.
The role of the α-crystallins in promoting/preventing protein aggregation and precipitation has been demonstrated in experiments performed in vivo/in vitro.
preventing, in vitro
Analysis of αA knockout mice: protein aggregates show large/small amounts of αB-crystallin and larger/smaller amounts of other proteins.
Resulted in Lens smaller/larger than normal-structurally similar though and formation of cataract in first one/few weeks.
large, smaller
smaller, few
(αB-crystallin/αA-cryastallin) is present in a variety of cells throughout the body, especially in heart and skeletal muscle.
αB-crystallin
T/F In vitro tests showed that the mutant form of the protein αB-crystallin had chaperone activity and did not enhanced the aggregation of test proteins.
False, In vitro tests showed that the mutant form of the protein αB-crystallin had NO chaperone activity and even ENHANCED the aggregation of test proteins.
T/F Studies suggest that αB-crystallin has important chaperone functions in the lens and in other cells of the body.
True
The β/γ-crystallin superfamily is less/more diverse than the α-crystallins, and the function of its members in the lens is less/more evident.
more, less
___ β-crystallin polypeptides and ____ γ-crystallins are expressed in the human lens.
a. 3, 6
b. 3, 3
c. 6, 3
d. 6, 6
c. 6, 3
Classical crystallins have a composition of ____ water and ____ organic matter (of which ____ is structural proteins).
a. 35%, 65%, 33%
b. 33%, 35%, 65%
c. 65%, 35%, 33%
d. 65%, 33%, 35%
c. 65%, 35%, 33%
Microtubules are abundant/sparse beneath the plasma membranes of lens fiber cells.
abundant
Microtubules play Important roles in:
1. stabilizing the fiber cell membrane
2. transporting vesicles to the apical and basal ends of elongating fiber cells
3. gives lens its birefringent property
4. all of the above
- all of the above
The membranes of mature lens fiber cells have an usual/unsusal lipid composition
unusual
Human lens fiber cells have the lowest/highest proportion of _glucose/cholesterol and sphingomyelin of any plasma membrane in the body, and the amount of glucose/cholesterol increases/decreases as the fiber cells mature.
highest, cholesterol, cholesterol, increases
The cholesterol/phospholipid ratio is nearly ___ ___ greater in nuclear than in cortical fiber cells.
a. 2 fold
b. 3 fold
c. 4 fold
d. 5 fold
b. 3 fold
T/F The presence of high concentrations of cholesterol and sphingomyelin is likely to cause lens fiber cell membranes to be flexible.
False, cause lens fiber cell membranes to be rigid,
T/F The human lens grows rapidly in the embryo and during the first postnatal year
True
The rate of lens growth slows between ages ___ and ____years, then continues at a much slower, nearly linear rate throughout life.
a. 2 and 10
b. 1 and 5
c. 1 and 10
d. 2 and 5
c. 1 and 10
In the anterior/posterior of the lens, this network, the tunica vasculosa lentis, arises from the iris stroma/hyaloid artery.
posterior, hyaloid artery
T/F The capillaries at the anterior/posterior of the lens arise from blood vessels of the developing iris stroma to form the anterior/posterior papillary membrane.
anterior, anterior
During the _____ trimester of human development, the capillaries of the tunica vasculosa lentis and the anterior papillary membrane regress.
a. first
b. second
c. third
b. second
Absence of the lens at an early stage of embryogenesis leads to
1. the absence of the corneal endothelium
2. abnormal differentiation of the corneal stroma
3. absence of the iris, ciliary body, and anterior chamber.
4. all of the above
- all of the above
T/F The lens derives much of its energy from glycolysis.
True
The start/end product of glycolysis is lactic acid.
end
As a result of lactate accumulation, intracellular pH raises/drops significantly from peripheral/central to deeper fiber cells.
drops, peripheral
T/F If cells could survive in an atmosphere free of oxygen, most oxidative damage could be avoided.
True
Molecular oxygen/nitrogen is, directly or indirectly, the source of least/most oxidative damage.
oxygen, most
The oxygen tension around the lens in the living eye is low, approximately ____ mm Hg
a. 10
b. 15
c. 20
d. 25
b. 15
The low/high oxygen tension around and within the lens probably damages/protects lens proteins and lipids from oxidative damage.
low, protects
Despite the low/high oxygen level, the lens derives a substantial proportion of its ATP form glycolysis/oxidative phosphorylation- a process that generates free radicals.
low, oxidative phosphorylation
T/F The lens is not exposed to solar irradiation throughout its life.
False. it IS exposed
Much of the solar irradiation that reaches the eye is absorbed by the cornea/retina, but the remaining UV light _could have/could not have _ harmful effects on the lens
cornea, could have
T/F If light is not absorbed, it produces no damage.
true
T/F DNA, proteins, nucleoside-containing metabolites, flavonoids, and pigments all absorb UV light and thus are not potential sources of free radicals
False, DNA, proteins, nucleoside-containing metabolites, flavonoids, and pigments ARE all potential sources of free radicals.
T/F Glutathione a tripeptide of the amino acids glutamine, cysteine, and glycine, provides most of the protection against oxidative damage in the lens.
True
When glutathione levels have been raised/lowered in lens epithelial cells or whole lenses, cell damage and cataract formation follow rapidly/slowly.
lowered, rapidly
T/F Ascorbic acid also provides protection to the lens from oxidative damage.
True
Ascorbic acid is actively/passively transported from the blood to the aqueous humor by a Na-_dependent/independent_ transporter in the ciliary epithelium/endothelium.
actively, dependent, epithelium
Ascorbic acid reaches concentrations in the aqueous humor that are up to _____ higher than levels in the blood.
a. 5x
b. 15x
c. 20x
d. 50x
c. 20x
As a result of the abundance/lack of blood supply, the oxygen concentration within and around the lens is much lower/higher than that in most other parts of the body.
lack, lower
T/F The lens does not depend on glycolytic metabolism to produce much of the ATP and the reducing equivalents required for its metabolic activities
the lens DOES depend on glycolytic metabolism
The glucose required for glycolytic metabolism is derived from the vitreous humor/aqueous humor.
aqueous humor
T/F Aqueous humor glucose levels are maintained by facilitated diffusion across the ciliary epithelium.
True
T/F Lens epithelial and superficial fiber cells do not contain mitochondria.
False. Lens epithelial and superficial fiber cells also HAVE NUMEROUS mitochondria
Cells near the surface of the lens may use/cannot use both glycolytic and oxidative pathways to derive energy from glucose.
may use
Lens should maintain: _low/high_ K+, _low/high_ Na+ _low/high_ Cl- _low/high_ water
High K+,
low Na+
low Cl-
low water
If sodium moved into lens increases in solutes, water content will increase/decrease (osmotically)
increase
In water electrolyte balance of the lens, the concentration gradient of aqueous has more/less Na+, low/high K+.
more Na+, low K+
The electrical gradient inside the lens is electropositive/electronegative.
electronegative
The water electrolyte balance is maintained by _________ pump.
1. Na+/Cl-
2. Na+/Na+
3. Cl-/K+
4. Na+/K+
- Na+/K+
Sodium -Potassium pump operates in the lens endothelium/epithelium, which has/does not have mitochondria
epithelium, has mitochondria
Sodium -Potassium pump requires energy and
\_\_\_ Na+ removed \_\_\_K+ is allowed.
a. 2 Na+, 3 K+
b. 2 Na+, 2 K+
c. 3 Na+, 2 K+
d. 3 Na+, 3 K+c. 3 Na+, 2 K+
The human lens is opaque/transparent to most wavelengths of visible light, it produces and accumulates chromophores/chromosomes that absorb the shortest/longest wavelengths of the visible spectrum.
transparent, chromophores, shortest
At birth, the human lens is _____ to _______.
1. clear and pale pink
2. pink and pale yellow
3. clear and pale brown
4. clear and pale yellow
- clear and pale yellow
T/F With increasing age, the amount of yellow pigmentation in the lens decreases.
T/F This pigmentation absorbs the shorter, more energetic wavelengths of light, preventing them from reaching the retina.
False. increases
True
With a low/high concentration of the chromophores, they can increase/reduce visual acuity by increasing/decreasing light absorbance, leading to the formation of what is termed a brunescent or nigrescent cataract.
high concentration, reduce visual acuity, increasing light absorbance
Brunescent cataract is less/more common in developing countries, which suggests that environmental or nutritional factors may be/may not be important.
more, may be
T/F Pterygium is an opacification of the lens.
False, Cataract
T/F A clinically significant cataract interferes with visual function.
True
A cataract is a loss of lens transparency with increased light scattering caused by:
1. Disruption of lens fiber cell structure 2. Increased protein aggregation 3. Phase separation lens cell cytoplasm. 4. 1 and 2 5. 1 and 3 6. 1, 2 and 3
- 1, 2 and 3
1. Disruption of lens fiber cell structure
2. Increased protein aggregation
3. Phase separation lens cell cytoplasm
T/F Cataract formation general effect is change in amount of soluble and insoluble lens protein.
True
Lens grows with age hence the protein content also decreases/increases with age.
increases
T/F In cornea formation, the process of change of soluble to insoluble lens protein is by cross linking.
False, cataract formation
The most common types of age-related cataracts are:
1. nuclear
2. cortical
3. posterior subcapsular.
4. 1 and 2
5. 1, 2 and 3
- 1, 2 and 3
- nuclear
- cortical
- posterior subcapsular
Nuclear cataracts occur in the youngest/oldest fiber cells, those formed during embryonic and fetal life.
oldest
Cortical cataracts occur in cells formed earlier/later in life.
later
T/F Posterior subcapsular cataracts (PSCs) result from light scattering by a plaque of swollen cells at the posterior pole of the lens.
True
Abundant evidence shows that nuclear cataracts are associated with increased/decreased oxidative damage to lens proteins and lipids.
increased
Nuclear cataracts are age-dependent and are more/less susceptible to oxidative damage.
more
T/F Any decrease in oxidative load or further decrease in the ability of the lens nucleus to cope with the normal level of oxidation is likely to lead to nuclear cataract formation.
False. increase in oxidative load
T/F Studies show association between oxidation, age, and cataract formation was provided by studies of patients treated with hyperbaric oxygen to alleviate the complications of peripheral vascular disease.
True
These individuals were exposed to ____ to ____ atmospheres of pure oxygen for ___ hour each day for up to 3 years. Of the 25 patients treated in this study, all but one had increased light scatter in the lens nucleus and seven developed frank nuclear cataracts.
a. 1.0 to 1.5, 1 hour
b. 2.0 to 2.5, 1 hour
c. 3.0 to 3.5, 2, hours
d. 2.0 to 2.5, 2 hours
b. 2.0 to 2.5, 1 hour
T/F The onset of nuclear cataract formation is often associated with an increase in the refractive power of the lens.
True
T/F For patients with myopia, this myopic shift temporarily causes an improvement in their near visual acuity, a phenomenon often called second sight.
False, for patients with hyperopia
Patients treated with hyperbaric oxygen also experienced significant hyperopic/myopic shift, like that seen just before the formation of a nuclear sclerotic cataract.
myopic shift
Nuclear cataracts commonly occur in younger/older patients within 6 months to 3 years after vitrectomy.
older
Anterior vitreous oxygen tension: low/high
Posterior vitreous oxygen tension: low/high
Anterior vitreous oxygen tension: LOW
Posterior vitreous oxygen tension: HIGH
With a removed vitreous the lens is exposed to decreased/increased oxygen which can lead to oxidative stress.
increased
T/F The high incidence of nuclear cataracts after this procedure is probably a result of changes in the environment around the lens, rather than a direct effect of the procedure on the lens.
True
The oxygen tension in the anterior vitreous is normally low, approximately \_\_\_\_ mm Hg.
a 14
b.15
c,16
d.17c. 16
The oxygen tension in the posterior vitreous near the retinal vessels is low/high, decreasing in a sharp gradient within the first 1/3/5 mm of the vitreous body.
high, 1
It is not/It is possible that when the vitreous is removed and the fluid in the eye can circulate freely the lens is exposed to decreased/increased oxygen from the retina.
It IS possible, increased
T/F Changes in protein organization leading to cataract are not subtle.
False, are subtle
In cataract formation, a small/large change in protein aggregation leads to a large amount of light scattering.
small
This makes it difficult to identify the changes that lead to opacification among the many alterations of lens proteins that occur with aging.
T/F The lens fiber cell are still well organized and intact despite a cataract is formed.
True
T/F In the senile cataract hypothesis, the higher molecular fractions do not grow in the cell cytoplasm.
False. HM fractions DO grow in to the cell cytoplasm.
In the ssenile cataract hypothesis, growing HM aggregates may cause the cell membrane to rupture/generate causing cellular debries.
rupture.
The HM fractions pull and break cytoplasm. This leads to fragmenting of cells. These fragments may become like debris and scatter light.
Cortical cataracts occur in the young/mature fiber cells lying close to the lens surface.
mature
Cortical cataracts most often occur in the superior/inferior half of the lens, with a tendency for these cataracts to occur in the superior/inferior nasal quadrant.
inferior, inferior
T/F Examination of the affected regions of lens fiber cells in a cortical cataract reveals almost complete disruption of cell structure.
True
Early-stage cortical cataracts usually are/are not clinically significant because the opacity is limited to the lens center/periphery and does not impinge on the visual axis.
are not, periphery
T/F As the cortical cataract progresses, the peripheral opacity may spread toward the visual axis, eventually interfering with vision. .
True
However, an individual may have a cortical opacity for years without experiencing a diminution of visual function
Extension of the opacity along the lengths of a small cluster of fiber cells leads to the formation of the “cortical spokes” that are often described in what type of cataracts?
Cortical cataract
Posterior subcapsular cataracts (PSC) are caused by light scattering in a cluster of swollen cells at the anterior/posterior pole of the lens, just beneath/above the capsule.
posterior, beneath
PSCs are particularly disabling. why?
Because the opacity produced by these cells is in the optical axis..
PSCs result from the normal/abnormal migration of lens epithelial cells or the aberrant differentiation of lens wing/fiber cells.
abnormal, fiber
“Pure” PSCs typically account for less than ___ of cataracts in humans. However, PSCs commonly occur in conjunction with _____ or _______ opacities.
a. 10%, nuclear, cortical
b. 20% nuclear, cortical
c. 10% nuclear, congenital
d. 20% traumatic, cortical
a. 10%, nuclear, cortical
T/F PSC cataracts affect near vision more when compared to distance vision in theory.
True
Patients with cataracts often have a combination of what type of cataracts?
a. nuclear and cortical
b. nuclear and posterior subcapsular
c. posterior subcapsular and cortical
d. nuclear, cortical and/or subcapsular
d. nuclear, cortical and/or subcapsular
In less/more developed countries, cataracts are removed as soon as they become visually disabling.
more
T/F If a cataract is removed, it may progress to a total or “morgagnian” cataract.
False, if cataract NOT removed
Is there a specific cause for total cataracts?
There is NO specific cause for total cataracts.
They are simply the result of the progression of a more localized cataract to the point at which it affects the entire lens.
T/F The most common approach taken to remove cataracts in developed countries is to
- remove a portion of the anterior lens epithelium
- capsule to expose the underlying fiber mass;
- extract the nuclear and cortical fiber cells, often using instruments for “photoemulsification”;
- implant a plastic intraocular lens (IOL) in the capsular bag.
True
T/F The phacoemulsification method of cataract removal is a form of intracapsular cataract extraction.
False. extracapsular cataract extraction
What is a common complication of extracapsular cataract extraction?
1. formation of secondary cataracts
2. formation of nuclear cataract
3. none
- formation of secondary cataracts also called after cataracts or posterior capsular opacification (PCO).
T/F Before IOLs were available, the entire lens was removed to remove the cataract.
True, this method is known as Intracapuslar Cataract Extraction:
What is/are true statements about intracapsular cataract extraction?
1. more common in developing countries
2. Rare in most places-
3. Older technique
4. entire lens is removed to remove cataract
5. all of the above
- ALL OF THE ABOVE
1. more common in developing countries
2. Rare in most places-
3. Older technique
4. entire lens is removed to remove cataract
5. all of the above
Lens epithelial cells near/away from the lens equator persist after cataract surgery and can migrate beneath/above the IOL onto the denuded posterior capsule.
near, beneath
T/F If the epithelial cells migrate further onto the posterior capsule, they may differentiate into small “lentoid bodies”, also called Elschnig’s pearls.
True
Congenital cataracts are cataracts that are present at?
1. death
2. after a traumatic injury
3. birth or appear soon after birth.
- birth or appear soon after birth
T/F One infectious cause of congenital cataracts is rubella infection in early pregnancy.
True
The rubella virus has been isolated from the lenses of affected individuals, and experimental infection of early-stage human lens tissue with the rubella virus has been demonstrated.
Anterior Polar Cataracts is another early/late-onset cataract and is an opaque plaque is formed near the periphery/center of the lens epithelium.
early, center
Which of the following are hereditary syndromes with associated cataract formation? (more than 1 answer is correct)
1. Oculocerebrorenal syndrome of Lowe
2. Neurofibromatosis type 2
3. Hyperferritinemia
4. Werner syndrome
5. Myotonic dystrophy
6. Galactokinase deficiency and galactosemia
7. Fabrys disease
8. none of the above
9. all of the above, except for #8
- all of the above, except for #8
1. Oculocerebrorenal syndrome of Lowe
2. Neurofibromatosis type 2
3. Hyperferritinemia
4. Werner syndrome
5. Myotonic dystrophy
6. Galactokinase deficiency and galactosemia
7. Fabrys disease
T/F In galactosemia and galactokinase deficiency, sugar or galactose accumulates to low levels in the body.
False accumulates to HIGH levels in the body.
In the Diabetic and Galactosemic cataract, the following statements are true except:
1 Conversion of glucose or galactose to respective sugar alcohols occurs via sorbitol pathway.
2. Sorbitol cannot readily diffuse out of intracellular compartment.
3. Osmotic gradient favors influx of H2O
4. process is exclusive to women
5. Sugar alcohols and sugar itself will lead to protein aggregation
- process is exclusive to women.
pathways can occur in both men and wowen
T/F Studies show a high lifetime exposure to UV light has not been linked to the formation of cataracts.
False HAS BEEN LINKED
Epidemiologic studies have linked high lifetime exposure to UV light with the formation of cortical cataracts in humans
T/F The mechanism by which UV exposure leads to cataract formation in humans has not been identified.
True
Although these studies have suggested that UV-generated free radicals can damage/repair components of the lens in a similar manner to that seen in cataract formation, these studies often do not/do fully take into account the biology of the human lens.
damage,do not
T/F Long-term exposure to infrared light and focused,high-energy microwaves can also cause cataracts.
True
Evidence that infrared light can cause cataracts comes mostly from epidemiologic studies in individuals exposed as a result of their occupation. This type of cataract is also called glass-blowers cataract.
T/F Glass-blowers cataract is congenital.
False.
Cataract formed after exposure due to their occupation, not born with
Long-term exposure to low/high-dose steroids is a significant risk factor of PSC formation in humans.
High
T/F Increased intracellular calcium can induce formation of cataracts.
True. Increased intracellular calcium affects -glucose metabolism, -inhibition of protein synthesis, -induction of HM aggregates -direct loss of transparency -Inhibit sodium pump
T/F Hypocalcemia is related to the dependency of the membrane permeability to levels of calcium and marked electrolyte and water imbalance in low calcium environment.
True
People with diabetes are at decreased/increased risk for early-onset cataracts.
increased
The lens provides a useful/useless system with which to study diabetic complications.
useful
Damage to the lens seems to be entirely a result of the low/high glucose level in diabetic patients.
high
In the Diabetes and lens osmotic hypothesis the following is the sequence of events leading to cataract formation:
1) Lens toxic levels of glucose
2) Aldose reductase activated
3) Glucose converted to sorbitol
4) Sorbitol cannot escape the lens now
5) Polyol dehydrogenase tries to get rid of sorbitol be converting it to fructose (reaction slow)
6) High intracellular osmotic pressure
7) Cells burst debris becomes manifestation of cataract
Know that people with diabetes are at decreased/increased risk for early-onset cataracts
Osmotic hypothesis has good experimental support in formation of cataract due to diabetes
T/F Osmotic hypothesis has good experimental support in formation of cataract due to diabetes
True
T/F Cataract formation due to denaturing of proteins due to glycation and oxidative stress is a supported theory.
False not a well supported theory
What is the primary risk factor for the most common kinds of cataract?
Age
One risk factor common to most kinds of cataracts is lower/higher socioeconomic status or higher/lower education level.
lower, lower
Lower/Higher socioeconomic status may predispose patients to nutritional deficiencies, increased exposure to diseases, poor general health status, and increased occupation exposure to cataractogenic agents.
Lower
T/F Women are at decreased risk for most kinds of cataract.
False, increased
Smoking and low/high alcohol consumption have been identified in several studies as dose-dependent/dose-independent_ risk factors for nuclear and in some cases cortical cataracts.
high alcohol, dose-dependent
Dark iris color is associated with lower/higher incidence of all types of lens opacities.
higher
Dark Iris color may also be related to lower/higher levels of cortical cataract in African-Americans than in Caucasians.
higher
T/F Studying the genetics of cataracts will provide information about the cataract formation.
True
Moderate caloric restriction, which reduces/increases cataract incidence and slows/speeds cataract progression in animals, also slows/speeds or prevents a variety of other age-related conditions.
reduces, slows, slows,
T/F Numerous epidemiologic studies suggest that nutrition does not play an important role in cataract formation.
DOES play an important role
T/F Information from the Age-Related Eye Disease Study may provide useful guidelines for the effects of a few components of the diet on cataract formation.
True
Age-Related Eye Disease Study is a large-scale clinical trial of the effects of selected vitamin and nutrient supplementation on the progression of eye diseases.
