Astigmatism and Presbyopia

Question 1

When parallel rays of light enter the eye (with accommodation relaxed) and do not come to a single point focus on or near the retina.

Answer 1

Astigmatism

Question 2

The sum of corneal astigmatism and residual astigmatism

Answer 2

Total Astigmatism

Question 3

When the two principal meridians are perpendicular to each other

Answer 3

Regular Astigmatism

Question 4

When the two principal meridians are not perpendicular to each other

Answer 4

Irregular Astigmatism

Question 5

When both principal meridians are focused either in front or behind the retina (with accommodation relaxed)

Answer 5

Compound Astigmatism

Question 6

The sum of the two axes of the two eyes equals approximately 180

Answer 6

Symmetrical Astigmatism

Question 7

The sum of the two axes of the two eyes does not equal approximately 180

Answer 7

Assymetrical Astigmatism

Question 8

Clinical Tests

Answer 8

Visual acuity tests – distance and near
Autorefraction
Keratometry
Retinoscopy 
Monocular subjective refraction, including Jackson cross cylinder

Question 9

in which the cornea exhibits a variation of curvature throughout different meridians.

Answer 9

Corneal Astigmatism

Question 10

in which two principal meridians exist at right angles to each other, one of the greatest and one of the least curvature.

Answer 10

Regular Astigmatism

Question 11

in which either the two principal axis are not at right angles to each other or the curvature of any one meridian is not uniform.

Answer 11

Irreggular Astigmatism

Question 12

both eyes are with-the-rule or both are against-the-rule

Answer 12

Homonymous

Question 13

one eye is with-the-rule and the other is against-the-rule

Answer 13

Heteronymous

Question 14

in which the astigmatism is due to unequal curvature of the lens surfaces or layers

Answer 14

Lenticlar Astigmatism

Question 15

How is astigmatism diagnosed?

Answer 15

Visual Acuity
Keratometry
Refraction

Question 16

Attributes all of the loss in acc. to biomechanical changes in the lens capsule & lens and none to the ciliary muscle

Answer 16

H-H-G Theory

Question 17

The amount of ciliary muscle contraction needed to produce a unit change in acc. progressively increases with age. Thus as one ages, the reduced amplitude is due to progressive weakening of the ciliary muscle itself.

Answer 17

D-D-F Theory

Question 18

Causes of sclerosis

Answer 18

Nutritional changes

Action of UV rays

Exposure to intense infrared radiation

Question 19

adult patients eventually report visual difficulties when faced with gradually declining accommodative amplitude and near task demands.

Answer 19

Functional Presbyopia

Question 20

the condition in which virtually no accommodative ability remains.

Answer 20

Absolute Presbyopia

Question 21

the earliest stage at which symptoms or clinical findings document the near vision effects of the condition

Answer 21

Incipient Presbyopia

Question 22

Condition which can still be overcome by a hard or forced ciliary effort.

Answer 22

Facltative Presbyopia

Question 23

accommodative ability becomes insufficient for the patient’s usual near vision tasks at an earlier age than expected.

Answer 23

Pre-mature Presbyopia

Question 24

the condition in which near vision difficulties result from an apparent decrease in the AA in dim light.

Answer 24

Nocturnal Presbyopia

Question 25

is the maximum increase in optical power that an eye can achieve in adjusting its focus from as far as possible (beyond infinity for a longsighted eye) to the nearest possible.

Answer 25

Amplitude of Accommodation

Question 26

Corrections for presbyopia with the use of plus lens or surgery

Answer 26

Bifocals
Reading glasses
Progressive Addition lenses (PAL)
Multifocal CL
Surgical Reversal of presbyopia with Scleral Expansion Bands
Laser Thermal Keratoplasty