Clinics, Refraction

Question 1

What are the 3 levels that make up binocular vision?

Answer 1

-simultaneous perception
-fusion
-stereopsis

Question 2

what are the advantages of binocular vision?

Answer 2

-increases FOV
-compensates for physiological blind spot
-binocular summation
-stereopsis

Question 3

where is the physiological blindspot?

Answer 3

the optic disk

Question 4

when does BV start developing in babies

Answer 4

not present at birth, starts developing mainly during first 2/3 years and stops after 8/9 years

Question 5

what is the definition of binocular vision?

Answer 5

Condition in which both eyes contribute
towards producing a percept which may or
may not be fused into a single impression

Question 6

what makes up the near vision triad?

Answer 6

-conversion
-accommodation
-miosis = pupil constriction

Question 7

what is near point of accommodation?

Answer 7

the distance at which the eyes see when fully accommodated

Question 8

how does near point of accommodation change with age?

Answer 8

it increases (i.e. the point the object becomes clear)

Question 9

name 5 causes of accommodative dysfunction

Answer 9

• Systemic and ocular medication
• Ocular trauma
• Inflammatory disease
• Metabolic disorders e.g. diabetes
• Down’s syndrome and Cerebral palsy (reduced amplitude)
• Idiopathic

Question 10

name 5 symptoms of accommodative dysfunction

Answer 10

• Headache
• Asthenopia (eyestrain)
• Near vision blur
• Difficulty in reading
• Difficulty in changing focus

Question 11

why is it important to know dynamic ret?

Answer 11

it may be the only way to assess accommodation in children

Question 12

what are the two methods of dynamic ret?

Answer 12

-(monocular estimation method) MEM
-Nott

Question 13

what shows lag and what shows lead in dynamic ret?

Answer 13

-lag = with movement so add positive lens
-lead= against movement so negative lens

Question 14

when reading, why is it normal for us to use less than required AoA? What does this mean?

Answer 14

as we dont focus exactly on the target but instead somewhere behind it due to depth of focus. this means the accommodative response is less than the accommodative stimulus meaning there is accommodative lag

Question 15

what is normal accommodative lag?

Answer 15

between +0.25DS- +0.75DS

Question 16

where do eyes focus in relation to the near target in accommodative lag and lead?

Answer 16

-in lag they focus behind the target as response is smaller than the stimulus
-in lead they focus in front of the target as the response is greater than the stimulus

Question 17

what could it mean if dynamic ret results are >+1.00DS? (accommodative lag)

Answer 17

• near esophoria because convergence system tries to compensate for the insufficient accommodation
• accommodative dysfunction (paresis, fatigue)
• under-corrected hyperope or over-corrected myope
• Higher + diopters (e.g., +2.00DS) shows presbyopia signs

Question 18

what could it mean if dynamic ret results are < +0.25DS? (accommodative lead)

Answer 18

• Near exophoria
• Spasm of accommodation
• Under-corrected myope
• Latent hyperopia

Question 19

how can you modify how you do dynamic ret for children?

Answer 19

to maintain appropriate fixation and accommodation, you can ask children to read some of the letters out aloud or to name/describe details in the picture

Question 20

what are the most common errors when assessing accommodation with dynamic ret?

Answer 20

1. Not realising that a small lag of accommodation is normal.
2. Taking too long to make a judgement as to whether the reflex is moving ‘with’ or ‘against.’
3. Nott method: inaccurate measurement of the distance of the target to the patient and the retinoscope distance from the patient that gives reversal.
4. MEM method: leaving the lens in place for too long. The lens can alter the accommodation of the eye.

Question 21

when might you do Nott dynamic ret instead of MEM?

Answer 21

if you dont have trial lenses to hand

Question 22

when does presbyopia start becoming clinically significant? what can cause it to occur earlier?

Answer 22

-clinically significant in the fifth decade of life
-occurs earlier in people living in hot climates, people with short arms, short working distances & hyperopes

Question 23

what happens to the comfortable near point with age?

Answer 23

it increases because accommodation reduces but the percentage of accommodation stays the same as before aging

Question 24

when determining working distance, what do reading and computer screen distances range from?

Answer 24

-reading : 33-40cm
-computer screens: 50-60cm

Question 25

what are the common errors when assessing reading addition?

Answer 25

• Assessing the near ADD without the distance correction in place
• Not insisting on the patient to read the lower line they can identify clearly
• Presenting the positive slide of the flippers when refining final add instead of the negative
• Not considering the hobbies of the patient i.e., knitting, sewing, crafting , modelling
• Not considering the occupation of the patient i.e. a contrabass player may benefit from an intermediate add alone for the distance he reads his music

Question 26

when determining the range of vision:
-how do you find the closest point of near vision?
-how do you find the furthest point of near vision?

Answer 26

-closest point = 1/(near add + AoA)
-furthest point = 1/(near add)

Question 27

what are the closest and furthest points of near vision in the range of clear vision

Answer 27

-closest point is where px uses total accommodative amplitude through near add
-farthest point is where px relaxes their accom through near add

Question 28

give 3 tips when assessing near reading addition

Answer 28

-stimulate the workstation environment
-keep referring back to h+s checking the needs of your patient
-check the range of your near add