MIDTERMS

Question 1

Classification of Functional Vision Deficits

Answer 1

1. Cloudy media
2. Central Field Deficit
3. Peripheral Field Deficit

Question 2

no field deficit (overall blur)

Answer 2

Cloudy media

Question 3

Any condition that alters the clarity of several clear structures may result in overall blurred
or hazy vision, impaired detail vision or significant glare without a field deficit

Answer 3

Cloudy Media

Question 4

Functional Implications of Symptoms:

Answer 4

o Generalized hazy or blurred vision
o Lost of ability to perceive sharp details
o Printed materials appeared faded, as do colors
o Focal opacities sometimes cause monocular diplopia
o Sunlight and direct lighting tend to cause glare
o Contrast is usually reduced causing poor border detection of both small and large
objects

Question 5

directly related to the extent of disorder, often 20/200 or worse

Answer 5

Visual Acuity

Question 6

blurred

Answer 6

Amsler Grid

Question 7

strong positive

Answer 7

Glare Test

Question 8

loss at all frequencies

Answer 8

Contrast Sensitivity

Question 9

Functional Tests Results

Answer 9

Visual Acuity –
Amsler Grid
Glare Test –
Contrast Sensitivity

Question 10

Management of Cloudy Media

Answer 10

Careful refraction which may involve automated refraction and keratometry. Visual
acuity with pinhole and/or refraction over a bandage contact lens can neutralize tear
film abnormalities, focal, opacities or irregular corneal surface.
- Moderate increase light can help patients with reduced contrast to perform better,
especially with proper positioning to avoid glare

Question 11

use of the following is advisable:

Answer 11

o Sun visor or hat
o Typoscope
o CCTV
o Sunglasses
o UV filters
o Polarizing filters
o Anti-reflective coating

Question 12

General measures to improve contrast are helpful like:

Answer 12

o Yellow filters or amber glasses
o CCTV with variable contrast
o Large print books
o Felt-tipped markers

Question 13

Improving contrast almost always helps. Measures include enhancing print contrast
through large print and with dark, felt-tipped markers, along with yellow filters indoors and
plum (light or medium) outdoors. CCTV provides a range of magnification along with
improved contrast

Answer 13

Central Field Deficit

Question 14

Certain diseases preferentially affect the peripheral retina or nerve pathways that carry
information from the peripheral visual field. The functional implications indicate mobility
and night vision affections.
- Peripheral field defects causing functional deficits generally fall into two categories: the
general constriction and the sector or hemianopic field defect.

Answer 14

Peripheral Field Deficit

Question 15

Functional Implication of Symptoms Peripheral Field Deficit

Answer 15

o Performance of the peripheral retina worsens at night or under poor illumination
o Patients may be unable to perceive people or objects in the surroundings unless the
object appears in their remaining visual field
o Difficulty ambulating in unfamiliar environment and anxiety about bumping into
peripheral objects.
o Difficulty in locating objects

Question 16

– usually good if there is no macular disease or cataract, may be 20/20

Answer 16

Visual Acuity

Question 17

normal if there is no macular disease, periphery is missing if field
constriction is advanced

Answer 17

Amsler Grid

Question 18

negative unless media pathology co-exists

Answer 18

Glare Test

Question 19

usually normal (except glaucoma) but may be difficult to test if
the central field is less than 5 degrees.

Answer 19

Contrast Sensitivity

Question 20

reduced

Answer 20

Visual Field

Question 21

allows you to predict the add from the best corrected distance acuity

Answer 21

Kestenbaum’s Rule

Question 22

allows you to read the predicted add directly from the near visual acuity chart.

Answer 22

Lighthouse Method

Question 23

predicts an add based on both the patient’s best-corrected distance
acuity level and the actual desired near acuity level.

Answer 23

Reciprocal Vision

Question 24

Consider the primary goal of the patient particularly the tasks and history

Answer 24

Deciding on Style

Question 25

adapt by looking slightly off center so the healthy part of the
retina is pointing straight ahead to receive the image.

Answer 25

Eccentric viewing

Question 26

defined as the optical power needed to focus parallel rays of light at 1 meter. As the
distance is shortened, the power needed to focus an image increase on inverse
proportion.

Answer 26

Diopters

Question 27

the distance at which a lens focuses parallel rays of light. Focal length is determined by
dividing 1m by the dioptric power of the lens.

Answer 27

Focal Length

Question 28

An object of a given size “projects” an image on the retina of the viewing eye. This retinal
image is also of a given size, usually measure in seconds, minutes, or degrees of an arc

Answer 28

X notation

Question 29

The purpose of low vision aids is to magnify the retinal image of an object. By enlarging the size
of the image that is projected onto the retinal surface, it is more likely that the image will be seen
by the remaining healthy tissue surrounding the compromised areas

Answer 29

Magnification

Question 30

• Also known as Linear Magnification
• The object is actually made larger while the working distance remains the same. There is
  a direct relationship between increased object in size and increased retinal image size.
• By just doubling the size of the actual object, the retinal image size is also double and
  easier to see.

Answer 30

Relative Size Magnification

Question 31

Also known as Approach Magnification
- As objects are brought closer to the eye, the retinal image size is again enlarged
proportionally. A closer object takes up a larger portion of the visual field and the image
will be larger on the retina. It is still necessary to focus image by means of accommodation
or lenses.

Answer 31

Relative Distance Magnification

Question 32

Optical Magnification
- It is a complicated type of magnification that occurs from a system of lenses, such as
telescopes and binoculars, wherein it increases the angular subtense of the object.
- Divergent light rays leaving the system cause images to appear to be coming from a closer
distance than the actual location of the object. The image seen is virtual. Our brain is
aware that objects appear smaller as they get further away, so when distant object appear
larger, our brain interprets them as being closer.
- It uses 2 or more lenses to create magnification.

Answer 32

Angular Magnification

Question 33

• An optical instrument designed to make objects appear nearer, containing an arrangement
  of lenses by which rays of light are collected and focused and the resulting image
  magnified.
• It can help people with low vision to improve distance vision

Answer 33

Telescope

Question 34

The two specifications that differentiate telescopes from one another are the:

Answer 34

o Magnification power
o Field of view

Question 35

• A Galilean telescope consists of a convex objective lens separated from a concave
  ocular lens by the sum of their focal lengths.
• Magnification (M) is derived by dividing the dioptric value of the ocular lens (Fe) by
  the dioptric value of objective lens (Fo).

Answer 35

Galilean Telescope (Terrestrial)

Question 36

consists of convex objective lens separated from a convex
ocular lens by the sum of their focal lengths.
- Magnification (M) is derived by dividing the dioptric value of the ocular lens (Fe) by
the dioptric value of objective lens (Fo)

Answer 36

Keplerian Telescope System (Astronomical)

Question 37

Print or images may be enlarged by projection.
- In Low Vision, closed circuit televisions (CCTVs) and other electronic magnifying
devices use this type of magnification very successfully.

Answer 37

Projection Magnification

Question 38

M = F/4
For the purposes of classification and ordering, magnifiers tend to be calibrated in terms
of magnification. This relies on some formulation allowing a magnification value to be derived
from knowing the dioptric value of the lens in the aid. However, this does not really represent how
an aid might be used.

Answer 38

Nominal Magnification Formula