Abstract
Purpose :
To measure the deformation of the lamina cribrosa (LC) 1 week after starting glaucoma medication to lower intraocular pressure (IOP).
Methods :
The lamina cribrosa (LC) of 23 eyes (15 patients, 62.1±12.4 years) were imaged by optical coherence tomography (OCT) before and at a follow-up appointment 7.3±1.4 days after starting glaucoma medication to lower IOP. Digital volume correlation (DVC) was used to correlate the pre- and post-treatment images to estimate the LC strains and anterior LC border displacement (ALD, Czerpak et al. 2022). We analyzed relationships between LC strains, ALD, IOP decrease (ΔIOP), and degree of visual field damage by linear regression.
Results :
Seventeen eyes of 12 patients, (group 1) had ΔIOP > 4 mmHg (5.8±1.5 mmHg, iCare tonometry), and 6 eyes of 5 patients (group 2) had ΔIOP < 2 mmHg (0.3±0.8 mmHg). IOP lowering in group 1 produced significant posterior ALD, tensile anterior-posterior strain Ezz, compressive radial strain Err, maximum principal strain Emax, and maximum shear strain γmax (all p≤0.012, Table 1). Both Ezz (p=0.005) and Err (p=0.023) were significantly larger than baseline DVC errors. The magnitude of Emax, γmax, and Err were significantly correlated to %ΔIOP in group 1 (p<0.04). Strain levels were not associated with ALD. Larger LC strain compliances (strain/ΔIOP) for Err, Emax, and γmax were associated with worse mean deviation and worse visual field index. In group 2, only γmax was significant (p=0.04). Ezz was borderline significant (p=0.053), but was 2.6 times smaller than in group 1.
Conclusions :
DVC analysis of OCT-based images reliably measures significant LC strains and ALD one week after starting glaucoma medication, as previously reported for IOP decrease after post-trabeculectomy suturelysis (Czerpak et al. 2022). A more compliant LC strain response was associated with greater glaucoma damage, as we previously reported. This method represents a practical approach to estimate LC biomechanical behavior in general ophthalmic practice as a biomarker for glaucoma susceptibility.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.