Q. 1 – Which of the following about the optic disc in myopia is correct.
- All optic discs in myopes are larger than normal
- The optic disc in myopia is always different from a normal optic disc.
- Gamma one is frequently found in myopia
- Beta zone is found more commonly in myopia
Q. 2 – Which of the following is false for the retinal nerve fiber layer in myopia.
- The RNFL may show macular thickening.
- The RNFL may show nasal thinning.
- The RNFL thinning is always associated with glaucoma in myopia
- When the RNFL circle passes over the area of gamma zone the RNFL measurement may not be accurate
Answer 1: 3
3. Gamma Zone is frequently found in myopia is the correct answer. The prevalence of gamma zone which is the distance of the Bruch’s membrane opening from the clinical margin of the optic disc increases with increasing axial length. All optic discs in myopia are nor large. On several occasions one may find optic discs that are smaller than normal. The Beta zone is found adjacent to the gamma zone more often but not always in patients of myopia with glaucoma. It is less likely to be seen in association with a non glaucomatous myopic disc
Answer 2: 3
3: The RNFL thinning is not always associated with glaucoma and one must look at the clinical picture before making a definitive diagnosis, specially with regard to the optic disc appearance, axial length and tilt of the disc. When the RNFL circle passes over the gamma zone/parapapillary atrophy one may be cautious in interpreting the results, because of the changes in the histology in this area. It may be good to take a RNFL scan around the Bruchs membrane opening which may help to get more accurate scans, specially if the machine marks the BMO accurately.