Vision2

Question 1

What happens to light when it goes from 1 medium to another

Answer 1

Velocity changes
, the path changes!

Some of the light reflects off the boundary and some of the light refracts through the boundary.

Angle of incidence = Angle of Reflection

Angle of Incidence > or < the Angle of refraction depending on the direction of the light

Question 2

What is refractive index or index of refraction

Answer 2

The denominator in this case will ALWAYS be smaller and produce a unitless value greater or equal to 1. This value is called the new medium’s INDEX OF REFRACTION, n.

Question 3

What are the two basic lens

Answer 3

Convex and concave

Question 4

What is convex lens

Answer 4

A converging lens (convex) takes light rays and brings them to a point.
has a real focal point eg (magnifying glass)

Question 5

What is a concave lens

Answer 5

A diverging lens (concave) takes light rays and spreads them outward.
Virtual focal point behind lens

Question 6

What is Emmetropia

Answer 6

Adequate correlation between axial length and refractive power

Parallel light rays fall on the retina (without accommodation)

Question 7

What is the name for refractive error

Answer 7

Ametropia (refractive error)
Mismatch between axial length and refractive power
Parallel light rays don’t fall on the retina without accomodation

Question 8

What are the different types of Ametropia

Answer 8

Near-sightedness (Myopia)
Farsightedness (Hyperopia)
Astigmatism
Presbyopia

Question 9

What happens in Myopia

Answer 9

Parallel rays converge at a focal point anterior to the retina

Question 10

What is the etiology of Myopia

Answer 10

not clear , genetic factor

Question 11

What are the causes of myopia

Answer 11

excessive long globe (axial myopia) : more common
excessive refractive power (refractive myopia)

Question 12

What are the symptoms of myopia

Answer 12

Blurred distance vision
Squint in an attempt to improve uncorrected visual acuity when gazing into the distance
Headache

Question 13

How do you correct myopia

Answer 13

. Correction with diverging lenses (negative lenses)
b. Correction with contact lens
c. Correction by removing the lens to reduce refractive power of the eye

Question 14

What is hyperopia

Answer 14

Parallel rays converge at a focal point posterior to the retina

Question 15

What is the etiology of hyperopia

Answer 15

not clear, inherited

Question 16

What are the causes of hyperopia

Answer 16

excessive short globe (axial hyperopia) : more common
insufficient refractive power (refractive hyperopia)

Question 17

How do you correct hyperopia

Answer 17

a. Correction with converging (positive lenses)
b. Correction with positive lens + cataract extraction
c. Correction with contact lens
d. Correction with intraocular lens

Question 18

What is astigmatism

Answer 18

Parallel rays come to focus in 2 focal lines rather than a single focal point

Question 19

What is the etiology of Atigmatism

Answer 19

Etiology : heredity

Question 20

What is the cause of astigmatism

Answer 20

refractive media is not spherical–>refract differently along one meridian than along meridian perpendicular to it–>2 focal points (punctiform object is represent as 2 sharply defined lines)

Question 21

Physics behind astigmatism

Answer 21

Question 22

What is the circle of least confusion and where is it seen

Answer 22

the location with the least loss of image definition. Midway between these two focal points.
Seen in astigmatism

Question 23

What are the symptoms of stigmatism

Answer 23

Asthenopic symptoms (headache , eyepain)
blurred vision
distortion of vision
head tilting and turning (to compensate)

Question 24

What is the treatment of astigmatism

Answer 24

Regular astigmatism : cylinder lenses with or without spherical lenses (convex or concave), Sx
Irregular astigmatism : rigid cylinder lenses, surgery

Question 25

What is the near response triad

Answer 25

near vision is mediated by three separate, but simultaneous pathways. This is known as the Near Response Triad

Question 26

What happens in near response triad

Answer 26

Pupillary Miosis (Sphincter Pupillae) to increase depth of field Convergence (medial recti from both eyes) to align both eyes towards a near object Accommodation (Circular Ciliary Muscle) to increase the refractive power of lens for near vision

Question 27

What happens in pupillary miosis in the near response triad

Answer 27

In Pupillary Miosis, the Pupil constricts, increasing the depth of field of the optics of the eye. This is mediated by the contraction of the circular Sphincter Pupillae Muscle within the Iris. With larger depth of field, the eye optical system is able to maintain clear focus over a certain range of viewing distances, even without relying on accommodation.

Question 28

What happens in convergence in near response triad

Answer 28

In Convergence, both eyes adduct medially at the same time, to align both eyes towards a near object. This is mediated by the simultaneous contraction of medial rectus extra-ocular muscles from both eyes.

Question 29

What happens in accomodation in near response triad

Answer 29

In accommodation, the lens accommodates, thus increasing the refractive power required to focus on a near object.

Question 30

what is prebyopia

Answer 30

Naturally occurring loss of accommodation (focus for near objects) Onset from age 40 years Distant vision intact

Question 31

How is presbyopia corrected

Answer 31

Corrected by reading glasses (convex lenses) to increase refractive power of the eye Reading glasses Bifocal glasses Trifocal glasses Progressive power glasses

Question 32

What are the different types of Optical correction

Answer 32

Spectacle lenses Monofocal lenses : spherical lenses , cylindrical lenses Multifocal lenses Contact lenses higher quality of optical image and less influence on the size of retinal image than spectacle lenses indication : cosmetic , athletic activities , occupational , irregular corneal astigmatism , high anisometropia , corneal disease Intraocular lenses Replacement of cataract crystalline lens Gives best optical correction for aphakia

Question 33

What are the disadvantages of contact lens

Answer 33

disadvantages : careful daily cleaning and disinfection , expense

Question 34

What are the complications of conjunctivites

Answer 34

infectious keratitis giant papillary conjunctivitis , corneal vascularization severe chronic conjunctivitis

Question 35

What are the advantage of intraocular lens

Answer 35

give best optical correction for aphakia , avoid significant magnification and distortion caused by spectacle lenses

Question 36

What are the disadvantages of intraocular lenses

Question 37

What are the other types of surgical corrections

Answer 37

Keratorefractive surgery :RK, AK, PRK, LASIK, ICR, thermokeratoplasty Intraocular surgery : clear lens extraction (with or without IOL), phakic IOL

Question 38

Which statement is false for Myopia? A) May be associated with large globe B) Light ray converges behind the retina C) May be associated with increased corneal curvature D) Unable to see objects clearly at distance without glasses or other optical correction

Answer 38

B) Light ray converges behind the retina

Question 39

In accommodation, which one of the following events does not take place? A) Relaxation of Circular Ciliary Muscle B) Relaxation of Zonules C) Thickening of Lens D) Increase of Lens Refractive Power

Answer 39

A) Relaxation of Circular Ciliary Muscle