Knapp Striae
𝘈𝘯𝘨𝘪𝘰𝘪𝘥 𝘚𝘵𝘳𝘦𝘢𝘬𝘴
● Bilateral
● Irregular linear breaks in the degenerated Bruch’s membrane
● Radiate from the optic disc in a cruciate pattern from an area of peripapillary pigment alteration
● Taper as they go away from the disc
● Pull of extraocular muscles create stress forces against the fixed point of the optic nerve which results in this pattern
● Colour varies from red to dark brown depending on the colour of fundus and overlying RPE atrophy
● Asymptomatic unless they involve macula
𝐀𝐬𝐬𝐨𝐜𝐢𝐚𝐭𝐞𝐝 𝐟𝐮𝐧𝐝𝐮𝐬 𝐜𝐡𝐚𝐧𝐠𝐞𝐬:
● Peau d’orange appearance - diffuse mottling of RPE representing focal defects in Bruch’s membrane and choriocapillaries
● Salmon spots - peripheral punched out focal yellowish atrophic RPE spots
● Optic disc drusen
● Fresh hemorrhages
● Cracked egg shell appearance - diffuse angioid streaks
𝐒𝐲𝐬𝐭𝐞𝐦𝐢𝐜 𝐀𝐬𝐬𝐨𝐜𝐢𝐚𝐭𝐢𝐨𝐧𝐬:
𝘗𝘌𝘗𝘚𝘐 Mnemonic:
● Pseudoxanthoma Elasticum
● Ehler- Danlos Syndrome
● Paget’s Disease
● Sickle Cell Anemia
● Idiopathic (50%)
𝐇𝐢𝐬𝐭𝐨𝐩𝐚𝐭𝐡𝐨𝐥𝐨𝐠𝐲:
● Extensive calcification and thickening of Bruch’s membrane and the intervening interstitial spaces between capillaries
● Elastic lamina affected
● Basophilic staining due to deposition of calcium seen with H&E
𝐂𝐨𝐦𝐩𝐥𝐢𝐜𝐚𝐭𝐢𝐨𝐧𝐬:
● Choroidal neovascularisation
● Macular degeneration
● Traumatic membrane rupture
● RPE tears
𝐅𝐅𝐀:
Window defect - Early hyperfluorescence with late staining
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Image from Rajan Eye Care Hospital
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