Abstract
Purpose: :
To characterize, quantitatively, the nerve fiber layer (NFL) of tilted discs in non-glaucomatous eyes with optical coherence tomography (OCT).
Methods: :
The optic disc photographs of 9,435 subjects were screened for tilted discs (either temporally or inferiorly tilted). Patients with a diagnosis of glaucoma or glaucoma suspect, visual field defects considered glaucomatous, intraocular pressure >21 mmHg, intraocular surgery, history of steroid use, ocular trauma or any ocular diseases were excluded. Subjects with OCT NFL images of acceptable quality (score >5/10) were enrolled. The NFL OCT measurements in eyes with temporally and inferiorly tilted discs were compared with measurements in normal individuals.
Results: :
When compared to the normal group (mean refractive error: -0.77±1.50 D, mean deviation (MD): -0.17±1.50 dB, pattern standard deviation (PSD): 1.64±0.44 dB), the temporally (33 eyes) and inferiorly (11 eyes) tilted disc groups were significantly more myopic (-7.67±3.81 D, p<0.001; -5.25±3.86, p=0.005, respectively), with worse MD (-2.69±2.21 dB, p<0.001; -4.01±1.69, p<0.001, respectively), and PSD (2.66±1.63 dB, p<0.001; 3.35±2.71, p<0.001, respectively). The average total NFL thickness of the temporally (90.7±16.4 microns) and inferiorly (92.4±15.7) tilted disc groups was significantly lower than the control group, statistically (102.6±9.6, p<0.001 and 0.005, respectively). The superior peak of the temporally tilted group was located more temporally than that of the normal group (55°±19° vs. 75°±16°, respectively, p<0.001). The inferior peak of the temporally tilted disc group also was located more temporally, but the difference was statistically insignificant (p=0.079). There was a statistically significant blunting of the superior peak in the inferiorly tilted disc group (p<0.001) with mean thicknesses of temporal, superior, and nasal quadrants from 84.22±18.96 to 85.36±34.53 microns.
Conclusions: :
The NFL thickness is distributed differently in eyes with tilted discs compared to normal eyes. The thick superior region of NFL is shifted temporally in temporally tilted discs, while the usual superior peak is blunted in inferiorly tilted discs. These findings should be considered when interpreting the OCT printout against the currently available normative database in eyes with tilted discs.
Keywords: optic disc • imaging/image analysis: clinical