Cone Dystrophies

Question 1

cone dystrophies - ERG

Answer 1

photopic responses are subnormal or non-recordable and flicker fusion frequency is reduced, but rod responses are preserved until late

Question 2

cone dystrophies - EOG

Answer 2

normal to subnormal

Question 3

cone dystrophies - DA

Answer 3

the cone segment is abnormal; the rod segment is initially normal, but may become subnormal later

Question 4

cone dystrophies - Colour vision

Answer 4

severe deuteron–tritan defect out of proportion to visual acuity

Question 5

cone dystrophies - Fluorescein angiography

Answer 5

round hyperfluorescent window defect with a hypofluorescent centre

Question 6

most common macular dystrophy

Answer 6

Stargardt disease

Question 7

Stargardt disease - genetics

Answer 7

AR ABCA4

Question 8

Stargardt disease - appearance

Answer 8

The macula may initially be normal or show non-specific mottling, progressing to an oval ‘snail slime’ or ‘beaten-bronze’ appearance and subsequently to geographic atrophy that may tend to a bull’s-eye configuration. A small proportion CNV. ○ Numerous yellow–white round, oval or pisciform (fish-shaped) lesions at the level of the RPE; these may be confined to the posterior pole or extend to the mid-periphery

Question 9

Stargardt disease - FAF

Answer 9

hyperautofluorescent flecks and macular hypoautofluorescence

Question 10

Stargardt disease - FA

Answer 10

The classic feature is a ‘dark choroid’ due to masking of background choroidal fluorescence by diffuse RPE abnormality; the macula shows mixed hyper- and hypofluorescence. Fresh flecks show early hypofluorescence due to blockage, and late hyperfluorescence due to staining; old flecks show RPE window defects

Question 11

Stargardt disease - ICGA

Answer 11

hypofluorescent spots, often more numerous than seen clinically

Question 12

Bietti crystalline corneoretinal dystrophy - genetics

Answer 12

AR

Question 13

Bietti crystalline corneoretinal dystrophy - appearance

Answer 13

Numerous fine yellow–white crystals scattered throughout the posterior fundus are followed by localized atrophy of the RPE and choriocapillaris at the macula, expand to periphery

Question 14

Bietti crystalline corneoretinal dystrophy - FA

Answer 14

characteristic large hypofluorescent patches corresponding to choriocapillaris loss, with intact overlying retinal vessels; the patches become confluent over time

Question 15

Alport syndrome - genetics

Answer 15

XLR, IV collagen

Question 16

Alport syndrome - features

Answer 16

chronic renal failure, sensorineural deafness, yellowish punctate flecks in the perimacular area. Anterior lenticonus and posterior polymorphous corneal dystrophy. prognosis good

Question 17

Alport syndrome - ERG

Answer 17

normal

Question 18

Congenital stationary night blindness - With an abnormal fundus appearance

Answer 18

Oguchi disease, Fundus albipunctatus

Question 19

Fundus albipunctatus - features

Answer 19

multitude of subtle, tiny yellow– white spots at the posterior pole, sparing the fovea. In contrast to retinitis punctata albescens, the retinal blood vessels, optic disc, peripheral fields and visual acuity are believed to remain normal

Question 20

Rod monochromatism - other name + genetics

Answer 20

complete achromatopsia AR

Question 21

complete achromatopsia - other name + genetics

Answer 21

Rod monochromatism AR

Question 22

Blue cone monochromatism - other name + genetics

Answer 22

incomplete achromatopsia XLR

Question 23

incomplete achromatopsia - other name + genetics

Answer 23

Blue cone monochromatism XLR

Question 24

Rod monochromatism (complete achromatopsia) - AR

Answer 24

visual acuity is poor, typically 6/60; there is congenital nystagmus and photophobia. The photopic (cone) ERG is abnormal and the scotopic may also be subnormal.

Question 25

Blue cone monochromatism (incomplete achromatopsia) - XLR

Answer 25

Only slightly subnormal acuity at 6/6–6/9, but colour vision is completely absent. No nystagmus and photophobia. There is a normal macula. The ERG is normal except for the absence of cone responses to red and white light.

Question 26

second most common macular dystrophy

Answer 26

Best vitelliform macular dystrophy