QuizWise 15

1. What is delta zone of eye?
   a. Central part of gamma zone in which blood vessels of at least 50 micron diameter were not detected and which had a minimal length of 300 micron
   b. The distance between the end of bruch’s membrane and the outer margin of the optic nerve (covered by pia mater)
   c. The distance between the end of bruch’s membrane and the beginning of RPE
   d. None of the above
   
2. What layers are absent in a gamma zone?
   a. Bruch’s membrane
   b. Retinal pigment epithelium
   c. Deep retinal layers
   d. Choriocapillaris
   e. Sattler’s layer of medium-sized choroidal vessels
   f. a, b, d
   g. All the above
   
3. Which of the following factors explain the increased susceptibility of glaucoma in myopic eyes?
   a. Thinning and elongation of the peripapillary scleral flange in delta zone
   b. The paucity of larger vessels in delta zone
   c. The increased distance between the peripapillary arterial circle of zinn-haller and the optic disc border in highly myopic eyes  
   d. All of the above
   
4. What effect does gamma zone have on sub-foveal choroidal thickness?
   a. It increases
   b. It decreases
   c. No correlation
   d. b and c
   
5. Wider parapapillary gamma zone was associated with-
   a. A longer axial length
   b. A smaller disc-fovea distance
   c. A thinner subfoveal choroidal thickness
   d. A higher degree of fundus tessellation
   e. a and b
   f. a and d
   g. a, d, e

Answers:-

1. a

Delta zone was a central part of gamma zone in which blood vessels of at least 50 mm diameter were not detected and which had a minimal length of 300 mm.

Gamma zone- the distance between the end of Bruch’s membrane and the outer margin of the optic nerve (covered by pia mater)

Beta zone- the distance between the end of Bruch’s membrane and the beginning of RPE

Reference: Jonas JB, Jonas SB, Jonas RA, et al. Parapapillary atrophy: histological gamma zone and delta zone. PLoS One. 2012;7(10):e47237. DOI: 10.1371/journal.pone.0047237

2. g

The parapapillary gamma zone has recently been described as the region located at the optic disc border. It is characterized by the absence of Bruch’s membrane, retinal pigment epithelium, deep retinal layers, choriocapillaris, and Sattler’s layer of medium-sized choroidal vessels.

Reference: Guo Y, Liu LJ, Tang P, et al. Parapapillary Gamma Zone and Progression of Myopia in School Children: The Beijing Children Eye Study. Invest Ophthalmol Vis Sci. 2018;59(3):1609‐1616. DOI: 10.1167/iovs.17-21665

3. d

The marked thinning and elongation of the peripapillary scleral flange in delta zone may be associated with the increased glaucoma susceptibility in highly myopic eyes as shown clinically, since the peripapillary scleral flange acts as the biomechanical anchor of the lamina cribrosa. In addition to the thinning of the peripapillary scleral flange, the paucity of larger vessels in delta zone and the increased distance between the peripapillary arterial circle of Zinn-Haller and the optic disc border in highly myopic eyes may be an additional factor for the increased glaucoma susceptibility in highly myopic eyes.

Reference: Jonas JB, Jonas SB, Jonas RA, et al. Parapapillary atrophy: histological gamma zone and delta zone. PLoS One. 2012;7(10):e47237. DOI: 10.1371/journal.pone.0047237

4. b

Both Beta zone and gamma zone widths correlates negatively with subfoveal choroidal thickness.

Macular thickness increases in the central region, but is stable in the pericentral region and decreased in the peripheral region with a more obvious change in the eyes with longer axial lengths.

Reference: Piao H, Guo Y, Ha JY, Sung MS, Park SW. Association of macular thickness with parapapillary atrophy in myopic eyes. BMC Ophthalmol. 2020;20(1):93. Published 2020 Mar 6. DOI: 10.1186/s12886-020-01362-8

5. h

Wider parapapillary gamma zone was associated with a marked vertical optic disc rotation after adjusting for a marked horizontal optic disc rotation, a longer axial length, a longer disc-fovea distance, a higher degree of fundus tessellation, and a thinner subfoveal choroidal thickness.

Reference: Guo Y, Liu LJ, Tang P, et al. Parapapillary Gamma Zone and Progression of Myopia in School Children: The Beijing Children Eye Study. Invest Ophthalmol Vis Sci.2018;59(3):1609‐1616. DOI: 10.1167/iovs.17-21665