Case 22: Nyctalopia

Question 1

6 signs associated with RP

Answer 1

1. waxy optic disc pallor 2. mid-peripheral pigment clumping 3. attenuated arterioles 4. hyaline bodies within the optic nerve 5. PSC cataracts 6. keratometry findings suggestive of keratoconus

Question 2

RP is characterized by progressive loss of _____ and ____ ____

Answer 2

Photoreceptor & RPE function

Question 3

In RP, ____ ____ is MC form of inheritance

Answer 3

Autosomal dominant

Question 4

What are the most common complains of pts w/ RP?

Answer 4

Night blindness & peripheral vision loss

Question 5

What is the avg age of dx for RP?

Answer 5

9-19

Question 6

___% of RP pts are symptomatic by 30 yrs

Answer 6

75

Question 7

RP Triad

Answer 7

Retinal bone-spicule pigmentation (pigment clumping in the mid-periphery), anteriolar attenuation, waxy optic disc pallor

Question 8

In the early stages of RP, the ___ ERG is reduced, while the ___ ERG is normal

Answer 8

Scotopic, photopic

Question 9

Gyrate atrophy

Answer 9

Very rare, bilateral, autosomal recessive chorioretinal degeneration due to deficiency in mitochondrial enzyme ornithine aminotransferase

Question 10

What is the classical clinical appearance of gyrate atrophy?

Answer 10

Multiple, well-defined, scalloped areas of peripheral choroioretinal atrophy. In childhood, the lesions begin in the mid-periphery & then coalesce to engulf most of the posterior pole, with the macula being spared until 40-70s

Question 11

Gyrate atrophy sx

Answer 11

Prevalent in most pts by age 10: nyctalopia, decreased vision, constricted VF. Decreased vision usually a result of posterior subcapsular cataracts, macular chorioretinal degen or CME

Question 12

Choroideremia

Answer 12

Very rare condition, characterized by diffuse & progressive atrophy of the choriocapillaris & overlaying RPE. Cause appearance of blond fundus. As atrophy worsens the deep choroidal vessels become prominent & underlying sclera becomes visible. Macula spared until later stages of disease.

Question 13

Choroidermia results from a deficiency in what?

Answer 13

Rab geranylgeranyl transferase, an enzyme utilized in membrane metabolism

Question 14

Choroidermia has what kind of genetic inheritance?

Answer 14

X-linked. Only males are affected all daughters are carriers. Most commonly presents in 1st decade of life

Question 15

Choroidermia sx

Answer 15

MC initial symptom is nyctalopia. By late childhood, pts will also report photophobia & peripheral vision loss & will have constricted VF

Question 16

In males w/ choroidermia, night blindness occurs early in life & progresses to total night blindness in ___ yrs

Answer 16

10

Question 17

In choroidermia, legal blindness occurs by age ____

Answer 17

50-60 yrs

Question 18

Fundus albipunctatus

Answer 18

Autosomal recessive congenital disorder that causes stationary (non-progressive) night blindness

Question 19

Fundus albipunctatus signs

Answer 19

Numerous, small, yellow-white dot-like lesions at the level of the RPE; the lesions are in the mid-periphery & spare the macula

Question 20

What is the difference between fundus albipunctatus & retinitis punctata albenscens?

Answer 20

Retinitis punctata albescens results in slow progression of night blindness

Question 21

What is the MC retinal dystrophy?

Answer 21

RP

Question 22

What is the MC assoc syndrome w/ RP?

Answer 22

Usher’s

Question 23

What are some additional systemic conditions assoc w/ RP?

Answer 23

Abetalipoproteinemia (lack of serum betalipoprotein), Alstrom’s disease, Cockayne’s syndrome, Kearns-Sayre syndrome, Laurence-Moon/Bardet-Biedl, Neuronal ceroid lipofuscinosis (lipopigments accumulate w/i neurons, resulting in CNS degen)

Question 24

RP Tx

Answer 24

Vit A supplementation. Adults 15,000 IU QD. Children 5,000 IU/day for 6 yr olds and 10,000 IU/day for 10 yr olds

Question 25

Do not prescribe what in high dosees to RP patients?

Answer 25

Vit E

Question 26

Ocular complications of isotretinoin

Answer 26

Dryness, blepharoconjunctivitis, eyelid edema, superficial punctate keratitis, nyctalopia, loss of color vision, pseudotumor cerebri