Week 1.08 Near Traid 1

Question 1

What does it mean by near vision complex

Answer 1

Mitosis, convergence and accommodation & their interactions
Many be problems at near only
Changing fixation from far to near
- pupil convergence accommodation all change
- sxs at one distance indicates problem with convergence or accommodation

Question 2

Pupil response at near

Answer 2

Miosis observed
pupil constriction at near does not depend on accom or convergence
For example, mitosis still occurs at near in uncorrected myopes and in advanced presbyopia

Question 3

Near vs light pupil responses

Answer 3

Near response is slower than response which happens when retinal illumination changes
Near response is maintained as long as near fixation is maintained (unlike the light response)

If light reflex present near reflex will also be present

Question 4

Investigations of convergence and accommodation

Answer 4

Convergence - NPC & vergence amplitudes, jump convergence & vergence facility (prism flippers), fixation disparity (mallet unit), FVA blur point

Accommodation - NPA, amplitude, accom facility (lens flippers), lag or lead (dynamic ret), positive & negative relative accom

Question 5

Near point of convergence NPC

Answer 5

Closest point to which the eyes can be converged whilst retaining single vision

Measured with RAF ruler - moved towards px till break point then move back until single

Repeat 4/5 times
Normal NPC is 10cm or less

Gather objective info I.e. look for one eye flicking out or failing to converge

Question 6

Meter angle

Answer 6

The reciprocal of the distance that you can converge at

Measure the PD in cm by the meter angle to get prism diopters

Question 7

Jump convergence testing

Answer 7

Px fixates spotlight at 6m
Hold pencil at chosen viewing distance - needs to be further away from their NPC
Observe eyes as fixation changes from spot to pencil
“Smooth”, “jerky”, “RE slower to re-fixate”

Recorded qualitatively with distances used
E.g.
Jump: 6m-15cm smooth & fast

Question 8

Convergence insufficiency

Answer 8

CI may be diagnosed if:
- px has symptoms at near
- NPC breaks >10cm
- exo-deviation at N that is at least 10prism diopters more than at D
- insufficient base out FVA at N
- px has low AC/A ratio

CI treatable in most px
Use pencil to nose exercises, block string, dot cards, prism flippers

Question 9

Convergence excess

Answer 9

Px could observe diplopia at NPC due to over-convergence
Can tell by looking at the pukinje images and would therefore be associated with high AC/A ratio

Question 10

Near point of accomodation

Answer 10

The closest point that can be seen clearly
Amplitude is a dioptric distance between far point and NPA
Whenever checking amplitude of accomodation always have the px distance rx in place

Question 11

Amplitude of accomodation

Answer 11

Use RAF ruler
Easier if px wears distance rx
Push up - move word closure till first blur that can’t be cleared “tell me when the letters start to go fuzzy/blurry”
Push down - move word away when reports clear again

Don’t forget objective measurements such as moving head back or forehead straining

Amplitude of accomodation is reciprocal of NPA (if dist rx worn)

Record:
NPA: R 18cm: L 20cm; BE 16cm
AoA: R 5.5D; L 5D BE 6.5D

Question 12

Accommodative facility

Answer 12

Measure of the dynamics of the system and a test of the ability to respond over a period of time

Test using a pair of lens flippers (e.g. +2D/-2D)
Px views a word a little bigger than acuity limit
Wait for px to say clear flip and clear again
2 clears is 1 cycle

Question 13

Accommodative accuracy

Answer 13

Test the accuracy of accomodation
- px may over or under-accommodate when viewing a target
- over-acc is called “accommodative lead”
- under-acc is called “accomodative lag”
E.g. if target is 25cm away ~4D of accom is needed
- lag is present if only 3D of accom is exhibited
- lead is present if 5D is exhibited

Question 14

How do we measure accommodative accuracy?

Answer 14

Measured using dynamic retinoscopy (accomodation active)
Dynamic means accom is active
Static ret - accomodation relaxed

Question 15

What are the two main techniques for dynamic retinoscopy?

Answer 15

MEM - monocular estimation method
- accom target on ret (scqaure attached to ret that px looks at)
- any viewing distance
- neutralised with sph

NOTT
- accom target held still (separate object at near to accommodate and ret is separate)
- WD changed to find neutral
- accomodative lag is then the diopters distance between ret and target
- e.g. target held at 25cm, ret at 33cm (25cm=4D, 33cm=3D demand so accomodative lag is 1D)
Reciprocal of target distance - reciprocal of ret distance

Question 16

Which 2 of the techniques in dynamic retinoscopy need their distance rx in place?

Answer 16

BOTH TECHNIQUES REQUIRE DISTANCE RX IN PLACE

Question 17

Change in accomodation without convergence

Answer 17

You accomodate more through lenses but still converge to original extent
Can demonstrate by adding -1DS lenses as you read - this measures your excess accom and positive relative accom

Question 18

Simple definition of AC/A ratio

Answer 18

Amount of convergence per dioptre of accomodation