. Author manuscript; available in PMC: 2015 Jan 1.

Published in final edited form as: J Glaucoma. 2014 Jan;23(1):10.1097/IJG.0b013e31829ea2a7. doi: 10.1097/IJG.0b013e31829ea2a7

Table 4.

The calculation of average values of RNFLT(r,θ) and NRI(r,θ) in seven RNFL locations.

RNFL
location

Equation

Instrument-specific RNFL properties

All rings

P_{ALL} = \frac{\sum_{r = r_{in}}^{r_{out}} \sum_{θ = 0 °}^{360 °} P (r, θ)}{N_{a}}

P(rθ) – RNFL properties including RNFLT(rθ) or NRI(rθ).
r_in – the radius of the innermost scanning ring.
r_out – the radius of the outermost scanning ring.
N_a – total number of A-scans in one measurement.
N_INNER – number of A-scans in inner rings.
N_OUTER – number of A-scans in outer rings.
N_S – number of A-scans in superior quadrant.
N_I – number of A-scans in inferior quadrant.
N_N – number of A-scans in nasal quadrant.
N_T – number of A-scans in temporal quadrant.

PS-OCT-EIA:
r_in = 1 mm
r_out = 2.5 mm
N_a = 36000
(100 A-scan/cluster × 36 clusters/ring × 10 rings)

PS-OCT-DEC:
r_in = 0.75 mm
r_out = 2.5 mm
N_a = 36000
(100 A-scan/cluster × 36 clusters/ring × 10 rings)

RTVue OCT:
r_in = 0.65 mm
r_out = 2.45 mm
N_a = 8681
(425 A-scan/ring × 4 rings + 587 A-scan/ring × 3 rings + 775 A-scan/ring × 3 rings + 965 A-scan/ring × 3 rings)

Inner rings

P_{INNER} = \frac{\sum_{r = r_{in}}^{(r_{out} + r_{in}) / 2} \sum_{θ = 0 °}^{360 °} P (r, θ)}{N_{INNER}}

Outer rings

P_{OUTER} = \frac{\sum_{r = (r_{out} + r_{in}) / 2}^{r_{out}} \sum_{θ = 0 °}^{360 °} P (r, θ)}{N_{OUTER}}

Superior

P_{S} = \frac{\sum_{r = r_{in}}^{r_{out}} \sum_{θ = 45 °}^{135 °} P (r, θ)}{N_{S}}

Inferior

P_{I} = \frac{\sum_{r = r_{in}}^{r_{out}} \sum_{θ = 225 °}^{315 °} P (r, θ)}{N_{I}}

Nasal

OS:

P_{N} = \frac{\sum_{r = r_{in}}^{r_{out}} \sum_{θ = 135 °}^{225 °} P (r, θ)}{N_{N}}

OD:

P_{N} = \frac{\sum_{r = r_{in}}^{r_{out}} (\sum_{θ = 315 °}^{360 °} P (r, θ) + \sum_{θ = 0 °}^{45 °} P (r, θ))}{N_{N}}

Temporal

OS:

P_{T} = \frac{\sum_{r = r_{in}}^{r_{out}} (\sum_{θ = 315 °}^{360 °} P (r, θ) + \sum_{θ = 0 °}^{45 °} P (r, θ))}{N_{T}}

OD:

P_{T} = \frac{\sum_{r = r_{in}}^{r_{out}} \sum_{θ = 135 °}^{225 °} P (r, θ)}{N_{T}}