QuizWise 23

  1. Which of the following can reduce the precision of RNFL thickness measurements?
    a. Optic disc (size and area)
    b. Disc-Fovea angle 
    c. Retinal vessel position
    d. Presence of Gamma zone 
    e. Tilted disc
    f. All of the above
  1. Which of the following is better to measure progression of structural glaucomatous loss?
    a. Peripapillary RNFL thickness 
    b. Minimum Rim width
    c. Macular GCL thickness
    d. Visual fields testing
  1. The rate of RNFL thinning per 5-year increase in age, ranges from?
    a. 1.3-1.7 µm 
    b. 1.5-2.5 µm
    c. 2.5-3.5 µm
    d. 3.5-4.5 µm
  1. The double hump pattern of RNFL is mainly due to?
    a. Superotemporal vessels
    b. Inferonasal vessels
    c. Superonasal vessels
    d. Inferotemporal vessels
    e. a and d
    f. b and c
  1. RNFL thinning is seen on OCT in all of the following except?
    a. Traumatic optic neuropathy
    b. Ischaemic optic neuropathy
    c. Alzheimer’s disease
    d. Parkinson’s disease
    e. Vitreo papillary traction
  1. RNFL splaying is?
    a. Decrease in temporal RNFL Thickness(RNFLT) with increase in superonasal and inferonasal RNFL T
    b. Decrease in nasal RNFLT with increase in superotemporal and inferotemporal RNFLT
    c. Increase in temporal RNFLT with decrease in superonasal and inferonasal RNFL T
    d. Increase in nasal RNFLT with decrease in superotemporal and inferotemporal RNFLT

QuizWise responses

  1. f.

Optic disc (size and area) and disc-fovea angle, retinal vessel position, refractive error and axial length, which can reduce the precision of RNFL thickness measurement. Retinal arteries coming from, and veins going to, the optic disc travel in the RNFL and contribute to it’s thickness. Arrangement of blood vessels influence the RNFL thickness measured with OCT. 

References:
Chua J, et al. Compensation of retinal nerve fibre layer thickness as assessed using optical coherence tomography based on anatomical confounders, Br J Ophthalmol 2020;104:282–290. Doi: 10.1136/bjophthalmol-2019-314086

Hood et al. Blood Vessel Contributions to Retinal Nerve Fiber Layer Thickness Profiles Measured With Optical Coherence Tomography. J glaucoma. 2008, Volume 17doi: 10.1097/IJG. 0b013e3181629a02

Bae SH, et al. Influence of myopia on size of optic nerve head and retinal nerve fiber layer thickness measured by spectral domain optical coherence tomography. Korean J Ophthalmol. 2016 Oct; 30(5):335-343. Doi: 10.3341/kjo.2016.30.5.335.

More recent evidence with OCT imaging indicates that the rate of structural change in glaucoma, as measured by the ONH (Optic Nerve Head) minimum neuroretinal rim width (MRW) and retinal nerve fiber layer (RNFL) has a significant aging component. Indeed, progression of these parameters, previously typically attributed only to glaucoma, can be explained in large part by aging because there was a lack of a statistical difference among patients with treated glaucoma and healthy controls in the rates of MRW or RNFL thickness change. The stronger relationship between aging and GCL thickness compared with the rim or peripapillary RNFL may indicate that GCL thickness could be better suited to measure progression of structural glaucomatous loss.

Chauhan et al. Differential Effects of Aging in the Macular Retinal Layers, Neuroretinal Rim, and Peripapillary Retinal Nerve Fiber Layer. American Academy of Ophthalmology, February 2020, Volume 127, https://doi.org/10.1016/j.ophtha.2019.09.013

The analysis of RNFL thickness with age suggested that the rate of RNFL thinning per 5-year increase in age ranged between 1.3 and 1.7 µm. Ho et al. 

Retinal Nerve Fiber Layer Thickness in a Multiethnic Normal Asian Population. American Academy of Ophthalmology May 2019, Volume 126, https://doi.org/10.1016/j.ophtha.2018.11.031 

  1. e  

Retinal arteries coming from, and veins going to, the optic disc travel in the RNFL and contribute to it’s thickness. Arrangement of blood vessels influence the RNFL thickness measured with OCT. The double hump pattern was identified in the RNFL profile, where the humps fall on, or just adjacent to, major temporal blood vessels. So, the location of the major temporal blood vessels is a good predictor of the variation in the RNFL thickness profile. There are 2 factors contributing to this correspondence. First, the blood vessels make a direct contribution to the OCT RNFL thickness. Second, the arcuate fiber bundles, providing the major contribution to the hump, tend to travel with the major temporal blood vessels.

Hood et al. Blood Vessel Contributions to Retinal Nerve Fiber Layer Thickness Profiles Measured With Optical Coherence Tomography. J glaucoma. 2008, Volume 17doi: 10.1097/IJG. 0b013e3181629a02

RNFL thickness measurement is not limited to glaucoma, but has also been useful in diseases such as non-arteritic ischaemic optic neuropathy, Parkinson’s disease, Alzheimer’s disease and multiple sclerosis. 

Chua J, et al. Compensation of retinal nerve fibre layer thickness as assessed using optical coherence tomography based on anatomical confounders, Br J Ophthalmol 2020;104:282–290. Doi: 10.1136/bjophthalmol-2019-314086

The location of the blood vessels may help predict the variations in the profiles of OCT RNFL thickness. Splaying may occur due to widening of the angle between the major vascular arcades which in turn drag the RNFL along, leading to thinning in the macular area and thickening in the vertical quadrants.

Hood et al. Blood Vessel Contributions to Retinal Nerve Fiber Layer Thickness Profiles Measured With Optical Coherence Tomography. J glaucoma. 2008, Volume 17doi: 10.1097/IJG. 0b013e3181629a02

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