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Junior Opthamology > Errors Of Refraction > Flashcards

Errors Of Refraction Flashcards

1
Q

Refraction is the ___________ that light rays undergo as they pass through _____ of varying _______.

A

change in direction

media

densities

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2
Q

Refraction in the eye takes place mainly at the ________ and the _______.

A

cornea

Lens

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3
Q

The aim of refraction in the eye is to ____________________ so that a clear image ,of the object of regard ,can be formed on the ________.

A

focus light rays entering the eye

retina

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4
Q

A eye with normal refraction is said to be _______________.

A

emmetropic

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5
Q

Eyes with refractive errors are said to be ____________.

A

ammetropic

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6
Q

_________ is a leading cause of low vision and a cause of blindness.

A

Refractive error

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7
Q

Dimensions of an adult eyeball

Anteroposterior diameter ________ mm Horizontal diameter ________ mm
Vertical diameter ________ mm
Circumference ________ mm
Volume ________ ml
Weight ________ gm

A

Anteroposterior diameter 23- 25 mm Horizontal diameter 23.5 mm
Vertical diameter 23 mm
Circumference 73.5 mm
Volume 6.5 ml
Weight 7 gm

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8
Q

Refractive index (R.I) of the lens: _____

Refractive index (R.I) of the cornea : ______

A

1.42

1.36

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9
Q

The total dioptric power of the human eye is __________.

The cornea and lens are the major refracting surfaces in the eye.
Cornea contributes ________ of these(_____D)

A

60D

two thirds

40

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10
Q

The Cornea ,with refractive index of ~ ______, has the dual purpose of ________ the eye and ____________ as it enters the eye.

After light passes through the cornea, a portion of it passes through the _______ and from there enters the ___________.

A

1.38

protecting

refracting light ; pupil; crystalline lens

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11
Q

The crystalline lens, which has a refractive index of ~_______ , is able to change its ______ and thus serves to ________ the vision process.

The lens is attached to the _________ which relax and contract in order to change the shape of the lens.

By carefully adjusting the lens shape, the ciliary muscles assist the eye in producing an image on the retina.

A

1.40; shape

fine-tune

ciliary muscles

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12
Q

The retina contains the ________ that serve the task of detecting the _______ and the ___________ of the incoming light.
These send nerve impulses to the ___________ , the ________ cranial nerve, which convey the message to the brain for interpretation.

A

photoreceptors; intensity

frequency; optic nerve

second

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13
Q

There are three main types of ametropia;

_________,__________,__________

A

Myopia. Hypermetropia. Astigmatism.

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14
Q

MYOPIA

Common error of refraction, also known as __________ or ___________ in which parallel rays of light coming from infinity are focused _____________ when accommodation is at rest. ______ objects are seen clearly, but objects _________ are blurry.

A

short sightedness or near sightedness

in front of the retina

Near

farther away

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15
Q

Most common refractive error is???

A

Myopia

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16
Q

Myopia: epidemiology

About 70-90% in some ______ countries and about 10-20% in _______ countries.

A

Asian

African

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17
Q

Aetiology and Risk factors for MYOPIA

Risk factors include a positive family history , frequent _____ work.

_____eased axial length (_____ eyeball). Increased ____________

A

near

Incr; Long

corneal curvature

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18
Q

Aetiology and Risk factors for MYOPIA

Risk factors include a positive family history , frequent _____ work.

_____eased axial length (_____ eyeball). Increased ____________

A

near

Incr; Long

corneal curvature

19
Q

Classification of MYOPIA

Based on Aetiology:
Axial- due to _____ease in ___________ of the eye in relation to its refractive components e.g physiological _____ eyeball, ____________ , ________________ surgery

A

incr; antero-posterior diameter

large; buphthalmos

post-scleral buckle

20
Q

Classification of MYOPIA

Based on Aetiology

Curvature- due to an ______ease in the curvature of the ______ or one or both surfaces of the ______ e. g _________,_________, or _____________

Index- due to an ____ease in the ________ of the lens e.g ___________ or ___________

A

incr; cornea

lens

keratoconus, anterior lenticonus, or posterior lenticonus

incr; refractivity

nuclear sclerosis or poorly controlled DM

21
Q

Classification of MYOPIA

Based on clinical appearance:
Simple – normal overshooting of eye development, usually below ____D, onset usually after ________, normal visual acuity after __________ and __________________ changes

Pathological ( progressive, degenerative)- definite pathological entity, usually above -6D, onset usually before 4years, visual acuity not normal after correction and fundal degenerative changes present

A

-6; 4years

correction; no degenerative fundal

22
Q

Classification of MYOPIA
Based on degree:
Low : ______________
Moderate : ______________
High : ______________

Based on age at onset:______,________,______

A

Low : less than -3.00D
Moderate :-3.00D to -6.00D
High : >-6.00D

Infantile, Youth,Adult

23
Q

Signs and symptoms of MYOPIA

_______ distance vision
_________
__________ retina
Sub-retinal ___________
_______ spot
Choroidal _____________

A

Blurry; Floaters

Thin pale

haemorrhages; Fuchs

neovascularization

24
Q

COMPLICATIONS of MYOPIA

Posterior _______________
________ _____________
Primary _______________
Staphyloma
__________

A

Vitreous detachment
Retinal detachment

open angle glaucoma

Visual loss

25
Q

Hypermetropia (hyperopia) or ________ -sightedness is the refractive state of the eye wherein parallel rays of light coming from infinity are focused ______________ with accommodation being at rest.
________ Objects appear blurry and those ________ clear.

A

long

behind the retina

Near

at a distance

26
Q

HYPEROPIA: Epidemiology

Family history.
Most ____________ are mildly hyperopic but it gets better with increasing age.
Infants with moderate to high hyperopia develop __________ if not corrected by age ____.

A

full term neonates

strabismus; 4

27
Q

HYPEROPIA: Aetiology

_______eased axial length is the most common cause.
_____eased corneal curvature

A

Decreased

Decreased

28
Q

Classification of hyperopia

Based on Aetiology:
Axial: due to __________ in AP diameter
Curvatural: _______eased curvature of the cornea reducing its power
Index: _________ in RI of the lens

A

shortening

decr

reduction

29
Q

Classification of Hyperopia

Based on degree:

________
_______
__________

A

Low
Moderate
High

30
Q

Classification of HYPEROPIA

Based on clinical appearance:

Simple or developmental hypermetropia : the commonest form that results from _______________________

____________ hypermetropia

Functional : due to __________________ functions.

A

normal biological variations.

Pathological

loss of accomodative

31
Q

Clinical features of HYPEROPIA

_______ near vision
___________
_____________

A

Blurry near vision
Asthenopia
Headaches

32
Q

Complications of HYPEROPIA

__________
____________

A

Amblyopia
Strabismus

33
Q

Astigmatism

Astigmatism is an imperfection in the ___________________ leading to blurred vision because light rays are not _______________ or have _____________ on the retina.
It often co exists with the other types of refractive errors.

A

curvature of the cornea

properly focused

multiple focal points

34
Q

Risk factors for astigmatism

Positive __________
____________

A

Positive family history

keratoconus

35
Q

Aetiology of Astigmatism

Idiopathic
__________________ cornea (idiopathic)
______
Corneal ________- and _______________

A

Irregularly shaped

Trauma

surgeries

anterior segment surgeries

36
Q

Classification of ASTIGMATISM

Based on axis of the principal meridians
Regular :principal meridians are _________
Irregular : principal meridians are _________

Based on focus of the principal meridians
_________,___________,__________

A

perpendicular; not

Simple Compound mixed

37
Q

Clinical features of ASTIGMATISM

Small amounts of astigmatism may ______________

Significant astigmatism would produce _________________

____________
______________

A

not have any symptoms.

blurred vision at any distance.

Headaches

Asthenopia

38
Q

Presbyopia

This is an ______-related inability to focus at ______ distances

It is a (physiological or pathological?) change occurring in adult eye causing ______ vision impairment with advancing age

A

age; near

physiological; near

39
Q

Presbyopia is strictly considered to be a refractive error

T/F

A

F

It’s not

40
Q

Management of Refractive Error

History: to include bio-data, presenting complaints, _________.
Examination:________ using Snellen’s chart, ____________ for IOP, _______ examination for structures of the anterior segment and ___________ to examine the retina

Investigations: Refraction (________ and ____________ ) , keratometry , corneal ________

A

spectacle use

Visual acuity; Tonometry

Slit-lamp; Fundoscopy

objective and subjective

topography

41
Q

General Treatment for Refractive Error

Good ___________
Good ___________ for close work
Career choice/ modification
Adequate follow -up

A

Nutrition

Illumination

42
Q

Treatment

Several options are available ,however, the doctor and patient would determine that which is best suited for each patient.
They include;
Corrective lenses : _______ lens , _______ lens , _________ lens

A

concave

Convex

cylindrical

43
Q

Treatment

_______ lens

Refractive surgeries: these are aimed at ______________ are also available

A

Contact

reshaping the cornea

Junior Opthamology (12 decks)

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