Emmetropia, Ametropia and reduced eye

Question 1

Emmetropia

Answer 1

An eye which forms a point image of a distant object on the retina.
The eyes far point is at infinity.

Question 2

Ametropia

Answer 2

A refractive condition where a distance object does not focus on the retina in an unaccommodated eye

Question 3

Ocular correction/ocular refraction

Answer 3

K (K’ - Fe)

Question 4

Dioptric length

Answer 4

K’ (4/3/k’ x1000)

Question 5

Far point

Answer 5

k (1/K x1000)

Question 6

Second focal length

Answer 6

fsp (k+d)

Question 7

Spectacle refraction

Answer 7

Fsp (1/fsp x1000)

Question 8

Spectacle magnification

Answer 8

SM = K/Fsp

SM = height of corrected retinal
image size/height of
uncorrected retinal image
size = hc’/hu’

Question 9

Uncorrected (RIS) retinal image size

Answer 9

hu’ = - 1000 tan w/K’

Question 10

Corrected (RIS) retinal image size

Answer 10

hc’ = SM X hu’

Question 11

Near point

Answer 11

A point conjugate with the macula in the uncorrected and fully accommodated eye

Question 12

Amplitude of accommodation

Answer 12

The maximum amount an eye can accommodate

Amp = K - B

Question 13

Near point vergence

Answer 13

B = 1/b x100

Question 14

Range of clear vision

Answer 14

Range = the far point distance to the near point distance

Question 15

Reduced eye has ocular ametropia of
+6.00DS/-4.50DC X 5. State the classification of astigmatism of this eye according to the focal lines relative to the retina.

Answer 15

It is a Compound hypermetropia astigmatism with-the-rule

Question 16

Rapidly progressive myopia (Juvenille Stress)

Answer 16

Condition in which myopia is progressing/increasing rapidly, due to an increase in axial length. Could be due to prolonged accommodation.