1-If a convex lens has a focal length of 1 cm, what is the refractive power of this lens in diopters:
0.01.
0.10.
100.*
10.
=[the power of a lens in diopters equals the reciprocal of its focal length in meters 1/F= 1/.001=100]
#[Special senses]
2-A convex lens having a focal length of 0.5 cm will have a power of:
2 Diopters.
20 Diopters.
10 diopters.
200 Diopters.*
=[ the power of a lens in diopters equals the reciprocal of its focal length in meters 1/F=1/.0005=200]
#[Special senses]
3-Concerning the eye all the following is correct, except:
The fovea lies on the visual axis.
Aqueous humour is secreted into the anterior chamber.*
Light reflexly activates the parasympathetic nerves supplying smooth muscle in the iris.
Most of the focusing power is due to the cornea.
=[The aqueous humor enters the posterior chamber flowing between the fibers of ligaments of the lens]
#[Special senses]
4-Regarding the Eye, all are true EXCEPT:
Eye ball is formed of 3 layers, the outermost contain photoreceptor.*
Receives electromagnetic waves from distant object.
Is protected by bony orbit.
Anterior and posterior chambers contain aqueous humor.
=[formed of 3 layers but inner most layer contain photoreceptor]
#[Special senses]
5-Light rays:
Of 300-700 run are seen.
Are bent toward a perpendicular line if passing from water into air.
Are bent away from a perpendicular line if passing from water into air.*
Ultra violet rays cause darkening of the skin while the infra-red rays cause heating.*
=[This change of direction is caused by a change in speed When light travels from water into air, it speed
up, causing it to change direction slightly. ]
#[Special senses]
6-Aqueous humor:
Is passively secreted by ciliary processes.
Contains glucose and amino acids as nutrients for retina.
Is the main regulator of intra-ocular pressure.*
All of the above.
=[it is actively secreted by ciliary processes, due to presence of blood aqueous barrier it contains less
glucose & protein and it is main regulator of intraocular pressure as improper drainage produces
glaucoma.]
#[Special senses]
, 7-The intra-ocular pressure:
Is the pressure of vitreous humor.
Increases the power of lens.
If increased produces cataract.
If increased prevents near vision.*
If decreased produces glaucoma.
=[is dependent mainly on aqueous humor, is important for normal focusing mechanism of eyes, if
increased, suspensory ligaments is stretched & accommodation to near vision not occur, if increased
produces glaucoma and cataract related to loss of lens transparency.]
#[Special senses]
8-Glaucoma:
Is a disease which causes opacity of lens.
Is a disease which affects far vision.
Is a disease which produces ischemia of lens.
Results from increased resistance to fluid outflow through spaces of Fontana.*
=[ loss of lens transparency and opacity of lens is termed as cataract, glaucoma causes failure of
accommodation of near vision and results from improper drainage of aqueous humor.]
#[Special senses]
9-Glaucoma:
Of the open angle type is due to forward movement of iris.
Is a disease which affects far vision.
Is a disease which produces ischemia of lens.
Can be treated by parasympathomimetic drugs.*
Occurs as a result of increased intraocular pressure above 10 mmHg.
=[Glaucoma of the closed angle type is due to forward movement of iris and IOP become above
21mmHg, affect near vision, treated by parasympathomimetics drugs which cause pupilloconstriction and
opening iridocornel angle &spaces of Fontana.]
#[Special senses]
10-Closed angle Glaucoma is characterized by all EXCEPT:
Severe headache and blurred near vision.
The canal of Shlemm is closed.*
Increased the intra-ocular pressure.
Pupil dilatation.
=[closed angle glaucoma caused by forward movement of the iris resulting in obstruction of the angle.]
#[Special senses]
11-The human Eye:
Contains a lens system of 45 Diopters.
The middle choroid coat is poor in pigments and vessels.
The innermost layer contains photoreceptors.*
The outermost layer is opaque and white.*
=[lens has a refractive power about 20D during rest and maximum of 34D during accommodation,
choroid rich in melanin pigments and vessels, innermost layer (retina) contains photoreceptors and
outermost layer composed of transparent cornea and opaque sclera.]
#[Special senses]
12-The Lens system of the human eye:
Is formed of biconvex lens and cornea.
0.01.
0.10.
100.*
10.
=[the power of a lens in diopters equals the reciprocal of its focal length in meters 1/F= 1/.001=100]
#[Special senses]
2-A convex lens having a focal length of 0.5 cm will have a power of:
2 Diopters.
20 Diopters.
10 diopters.
200 Diopters.*
=[ the power of a lens in diopters equals the reciprocal of its focal length in meters 1/F=1/.0005=200]
#[Special senses]
3-Concerning the eye all the following is correct, except:
The fovea lies on the visual axis.
Aqueous humour is secreted into the anterior chamber.*
Light reflexly activates the parasympathetic nerves supplying smooth muscle in the iris.
Most of the focusing power is due to the cornea.
=[The aqueous humor enters the posterior chamber flowing between the fibers of ligaments of the lens]
#[Special senses]
4-Regarding the Eye, all are true EXCEPT:
Eye ball is formed of 3 layers, the outermost contain photoreceptor.*
Receives electromagnetic waves from distant object.
Is protected by bony orbit.
Anterior and posterior chambers contain aqueous humor.
=[formed of 3 layers but inner most layer contain photoreceptor]
#[Special senses]
5-Light rays:
Of 300-700 run are seen.
Are bent toward a perpendicular line if passing from water into air.
Are bent away from a perpendicular line if passing from water into air.*
Ultra violet rays cause darkening of the skin while the infra-red rays cause heating.*
=[This change of direction is caused by a change in speed When light travels from water into air, it speed
up, causing it to change direction slightly. ]
#[Special senses]
6-Aqueous humor:
Is passively secreted by ciliary processes.
Contains glucose and amino acids as nutrients for retina.
Is the main regulator of intra-ocular pressure.*
All of the above.
=[it is actively secreted by ciliary processes, due to presence of blood aqueous barrier it contains less
glucose & protein and it is main regulator of intraocular pressure as improper drainage produces
glaucoma.]
#[Special senses]
, 7-The intra-ocular pressure:
Is the pressure of vitreous humor.
Increases the power of lens.
If increased produces cataract.
If increased prevents near vision.*
If decreased produces glaucoma.
=[is dependent mainly on aqueous humor, is important for normal focusing mechanism of eyes, if
increased, suspensory ligaments is stretched & accommodation to near vision not occur, if increased
produces glaucoma and cataract related to loss of lens transparency.]
#[Special senses]
8-Glaucoma:
Is a disease which causes opacity of lens.
Is a disease which affects far vision.
Is a disease which produces ischemia of lens.
Results from increased resistance to fluid outflow through spaces of Fontana.*
=[ loss of lens transparency and opacity of lens is termed as cataract, glaucoma causes failure of
accommodation of near vision and results from improper drainage of aqueous humor.]
#[Special senses]
9-Glaucoma:
Of the open angle type is due to forward movement of iris.
Is a disease which affects far vision.
Is a disease which produces ischemia of lens.
Can be treated by parasympathomimetic drugs.*
Occurs as a result of increased intraocular pressure above 10 mmHg.
=[Glaucoma of the closed angle type is due to forward movement of iris and IOP become above
21mmHg, affect near vision, treated by parasympathomimetics drugs which cause pupilloconstriction and
opening iridocornel angle &spaces of Fontana.]
#[Special senses]
10-Closed angle Glaucoma is characterized by all EXCEPT:
Severe headache and blurred near vision.
The canal of Shlemm is closed.*
Increased the intra-ocular pressure.
Pupil dilatation.
=[closed angle glaucoma caused by forward movement of the iris resulting in obstruction of the angle.]
#[Special senses]
11-The human Eye:
Contains a lens system of 45 Diopters.
The middle choroid coat is poor in pigments and vessels.
The innermost layer contains photoreceptors.*
The outermost layer is opaque and white.*
=[lens has a refractive power about 20D during rest and maximum of 34D during accommodation,
choroid rich in melanin pigments and vessels, innermost layer (retina) contains photoreceptors and
outermost layer composed of transparent cornea and opaque sclera.]
#[Special senses]
12-The Lens system of the human eye:
Is formed of biconvex lens and cornea.
