- Which of the following are considered to be layers of the choroid.
- Haller’s Layer
- Sattler’s Layer
- Ellipsoid Zone
- Interdigitation zone
2. About the Bruch’s membrane one or more of the following are true
- Bruch’s membrane is rich in collagen.
- It’s thickness may vary from 2-4 microns
- Bruch’s membrane loss is associated with development of CNVM
- It is never thrown into folds.
- It is always located 360 degrees at the margins of the clinical optic nerve.
Q 1 Answer: 1,2 and 3.
The choriocapillaris, Hallers and Sattler’s layers are part of the choroid. The choriocapillaris is generally the innermost layer next to the Bruch’s membrane, the Sattler’s layer is next and consists of larger vessels. The outmost is the Haller’s layer of larger vessels. These are formed by the short posterior and the long posterior ciliary arteries. The ellipsoid and interdigitation zones are photoreceptor layers located just anterior to the pigment epithelium.
Q 2 Answer- 1,2 and 3.
While histologically the thickness has been found to be 2-4 microns, measurements on the OCT may be more, because of debris of cells on the Bruch’s membrane. Also the thickness may differ in the foveal area compared to the parapapillary area. The Bruch’s membrane loss or break is associated with the development of choroidal neovascularisation in the retinal layers, since the vessels may grow from the choriocapillaris into the outer retina. Bruch’s membrane is seen to be thrown into folds following hypotony and what we see clinically as choroidal folds are also Bruch’s membrane folds. The Bruch’s membrane surrounds the optic nerve and in the emmetropic eye the Bruch’s membrane opening surrounds the clinical optic nerve. However in myopia the tempral Bruchs membrane may often move away from the margin of the optic nerve resulting in the formation of the Gamma zone, which is the space between the margin of the optic disc and the Bruch’s membrane.