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C. Y. Mardin, R. Lämmer, D. Baleanu, A. Juenemann, R. Tornow, F. Horn; 3-D Optic Disc Morphometry and Retinal Nerve Fibre Layer Thickness With Spectral-Domain OCT in Ocular Hypertensives and Preperimetric Glaucomas. Invest. Ophthalmol. Vis. Sci. 2010;51(13):215. doi: https://doi.org/.
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To investigate the relationship between RNFL thickness measurements and disc morphology in corresponding eyes obtained with laser-scanning-tomography (LST) and spectral-domain-OCT (sd) in ocular hypertensives (OHT) and preperimetric glaucomas (pPOAG).
The study included 586 eyes of 295 patients and controls. 115 controls (N), 149 OHT, 132 pPOAG and 174 advanced glaucoma (POAG) patients were recruited from the Erlangen Glaucoma Registry.Methods: Controls and patients underwent a standard ophthalmic examination including slit-lamp inspection, funduscopy, gonioscopy, perimetry and papillometry. In addition, a 24-hour intraocular pressure phasing (applanation tonometry) was performed in all patients. Optic disk evaluations were based on 15° color photographs and disc appearance (rim notching, vertical elongation of cup, RNFL loss) determined the diagnostic groups. The participants were scanned with the HRT I, II , III device and a commercially available sd-OCT (Spectralis HRA+OCT; both Heidelberg Engineering, Germany). 25 consecutive circular B-scans (3.4 mm diameter, 768 A-scans) centered at the optic disc were automatically averaged. HRT III’s rim area and volume (ra/rv), retinal thickness (r/t) and the GPS score were chosen to describe the 3-D disc morphology. Parametric and non-parametric tests were applied as appropriate for comparison between groups.
There was no significant difference in disc area between the four diagnostic groups (N 2.3 ± 0.7mm², OHT 2.3 ± 0.5mm², pPOAG 2.5 ± 0.6mm², POAG 2.4 ± 0.5mm²). Mean RFNL thickness with sd-OCT was in N 96.2±8.7µm, OHT 92.9±11.6µm (p=0.007), pPOAG 81.6±12.9µm (p=0.0001) and in POAG 63.56±14.5µm (p<0.0001). There was no significant difference for HRT’s ra, rv, rt or gps-classification between N (1.5±0.3mm², 0.4±0.2mm³, 0.3±0.07mm, 0.4±0.3) and OHT (1.5±0.4mm², 0.4±0.2mm³, 0.3±0.06mm, 0.4±0.3). PPOAG discs showed significantly different values (1.4±0.4mm² (p=0.05); 0.3±0.2mm³, 0.2±0.07mm, 0.6±0.3 (p<0.0001). Mean RNFL loss of -16% in pPOAG was correlated to a -7% loss of ra and -25% of rv respectively. OHT discs with a healthy appearance showed a mean RNFL loss of 4%.
OHT eyes tend to show a RNFL loss, although disc appearance and stereometric parameters of the disc seem to be unchanged to normals. Glaucoma discs without perimetric defects already show a significant loss of RNFL and rim volume in correlation to disc appearance on photographs. These findings may support early glaucoma detection.
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