Figure 5 shows typical patterns of RNFL reflectance spectra in retinas with different degrees of cytoskeletal distortion. The bundles in
Figure 5 were selected near the ONH. For the bundle with normal-looking cytoskeletons (
Fig. 5A), the reflectance spectrum had a similar pattern as in the control; however, the slope of the reflectance spectrum in the short wavelength range (400–480 nm) was shallower than in the control. For the bundle with F-actin distortion (
Fig. 5B), the reflectance spectrum was flatter in the short wavelength range compared with the control and
Figure 5A. In the bundle with distortion of all cytoskeletal components (
Fig. 5C), the entire spectrum flattened across all wavelengths. It is important to note, however, that bundles with distortion of all components were still visible in reflectance images and their reflectance was still directional (data not shown).
Changes in RNFL reflectance spectra were different along bundles in glaucomatous retinas.
Figure 6 demonstrates the reflectance spectra at different areas along the same bundle, which had no apparent distortion of the cytoskeleton. For the peripheral bundle area (
rc ), the spectrum was similar to the control with an apparent decline of reflectance as the short and long wavelengths increased. However, as the bundle area approached the ONH, the decline of reflectance with increasing wavelength became less steep. The entire spectrum gradually became flat from
rc to
ra . Such spectral change was often found in the bundles with normal-looking and slightly distorted cytoskeletons.
To quantitatively compare reflectance spectra of different groups, reflectance ratios at the short and long wavelengths (
ρS and
ρL ) were calculated for each measured spectrum and
ρS and
ρL averages were summarized in
Figure 7A. The values of
ρS and
ρL of the control, also listed in
Table 1, are discussed above. For bundles with normal-looking cytoskeletons,
ρS and
ρL of the peripheral regions (
rb and
rc ) were not statistically different than the control (
P > 0.2); however, both
ρ S and
ρL of the bundle regions near the ONH (
ra ) were significantly different than that of the control with lower
ρS (
P < 0.01) and higher
ρL (
P < 0.04). For bundles with early and apparent cytoskeletal distortion,
ρS and
ρL were significantly changed at all radii compared with the control (
P < 0.004 for
ρS and
P < 0.02 for
ρL ), except for
ρL at
rb . The bar graph in
Figure 7A shows overall changes of
ρS and
ρL with increasing cytostructural damage—that is,
ρS decreased with increased cytoskeletal damage while
ρL gradually increased with increased axonal damage. For the bundles near the ONH,
ρS of G2 and G3 decreased significantly compared with G1 (
P < 0.03).