2. Congenital Defects

Question 1

What is the simplest meaning of congenital defects?

Answer 1

Inherited colour vision defects. Most common cause of CV defects.

Question 2

When are congenital defects onset?

Answer 2

At birth

Question 3

How are 2 eyes affected in congenital defects?

Answer 3

Both eyes are affected equally

Question 4

Does congenital defects affect VA and visual fields?

Answer 4

No, expect monochromats- because the cause of congenital defects is in the photoreceptor affecting visual pigments

Question 5

What does Dichromat mean?

Answer 5

Cone absent or not functioning.
people with this condition will even Confuse bright, fully saturated colours.

Question 6

What does anomalous trichromat mean?

Answer 6

All 3 cones are present, but the sensitivity of 1 of the 3 cones is altered.

Question 7

What are the defects called that affect L,M,S Cones

Answer 7

Protan: Affect L cone
Deuteran: Affect M cones
Tritan: Affect S cones

Question 8

What is protanopia?

Answer 8

L cone is absent
Patients unable to distinguish between red-yellow-green.
Patients can only distinguish between the colours based on brightness only.
Reds may be confused with black or dark grey.

Question 9

What is deuteranopia?

Answer 9

M cone is absent
Patients unable to distinguish between red-yellow-green.

Question 10

Deuteranopia has what advantage over Protanopia?

Answer 10

No dimming problems because they have sensitivity across the whole spectrum because they have S and L cones.

Question 11

What is tritanopia?

Answer 11

S cone is absent
Patients unable to distinguish between blue-green-yellow.

Question 12

How is tritanopia carried genetically?

Answer 12

Not carried on the X chromosomes but on autosomes.

Question 13

What is anomalous trichomats?

Answer 13

Patients have all 3 cones, but 1 has abnormal sensitivity. This is the most common defect seen in practice.

Question 14

What will anomalous trichomats confuse?

Answer 14

Confuse pale desaturated colours, but not bright and saturated ones

Question 15

What is the main congenital colour defect? - (which colours?)

Answer 15

Mainly red- green

Question 16

Male vs females, who has a higher percentage of congenital defects?

Answer 16

Males

Question 17

Final colour vision analysis occurs in what part in the cortex?

Answer 17

V4

Question 18

What problems would someone with protanopia face when driving?

Answer 18

May not be able to see red traffic light

Question 19

Which cones are present in the fovea (in the retina)

Answer 19

M and L cones

Question 20

What is monochromacy?

Answer 20

When only 1 type of photoreceptor is present.

Question 21

What is Rod (typical) monochromats?

Answer 21

No cones present

Question 22

What is cone (atypical) monochromats?

Answer 22

Only one cone present

Question 23

Are cone (atypical) patients monochromats?

Answer 23

Yes

Question 24

Which patients have better VA- Typical or Atypical?

Answer 24

Atypical- because they have 1 type of cone present.

Question 25

Typical or Atypical, which patients are likely to have photophobia and nystagmus?

Answer 25

Typical

Question 26

What causes anomalous trichomats?

Answer 26

1 out of the 3 cones have altered sensitivity compared to normal. The sensitivity of the abnormal curve is shifted closer to the other curves- the closer the curves are the more serious the defect is.

Question 27

Describe the type and severity of congenital CV defects?

Answer 27

Constant

Question 28

What are the 3 types of congenital defects?

Answer 28

1. Monochromat
2. Dichromat
3. Anomalous trichromat

Question 29

Protan and deutan defects are also known as?

Answer 29

Red- green defects