Abstract
Purpose: :
To compare the configuration of the optic disc and lamina cribrosa before and after glaucoma surgery by using swept-source optical coherence tomography (SS-OCT).
Methods: :
We assessed 28 eyes of 26 consecutive glaucoma patients (11 men and 15 women; mean age, 61.6 ± 12.7 years; range, 23-80 years) who underwent glaucoma surgery at Kyoto University Hospital, between June and September 2011.Using the SS-OCT prototype system developed by TOPCON, which uses a tunable laser as a light source operated at 100,000 Hz A scan repetition rate in the 1-μm wavelength region, 7 serial vertical scans were acquired before and 3 months after the surgery, and scans at identical locations were compared. Bruch’s membrane opening (BMO) was defined as the reference line, and sclera, anterior lamina cribrosa boundary, and internal limiting membrane (ILM) were delineated with dotted lines. The largest distances from the BMO reference line to the anterior lamina cribrosa boundary, the areas enclosed by these 2 lines, and the thicknesses of the prelaminar neural tissue were measured. Correlations between the changes in lamina cribrosa depth, prelaminar neural tissue thickness, and IOP reduction were assessed for statistical significance.
Results: :
SS-OCT allowed improved visualization of deep structures of the optic disc. The IOP reduced from 21.9 ± 5.0 mmHg (before surgery) to 12.0 ± 5.1 mmHg (after surgery). The depth of the lamina cribrosa decreased from 632.1 ± 142.8 µm (before surgery) to 596.9 ± 115.5 µm (p = 0.03, paired-t test) (after surgery), which correlated with the rate of IOP reduction after surgery (ρ = –0.372; p = 0.07). The area enclosed by the BMO reference line and the anterior lamina cribrosa boundary decreased from 12.12 ± 3.50 µm2 (before surgery) to 11.07 ± 2.46 µm2 (p = 0.01) (after surgery), which significantly correlated with the rate of IOP reduction after surgery (ρ = –0.456; p = 0.02, Spearman rank correlation). The thickness of prelaminar neural tissues increased from 166.9 ± 66.4 µm (before surgery) to 189.2 ± 79.0 µm (p = 0.01) (after surgery), which also significantly correlated with the rate of IOP reduction after surgery (ρ = –0.559; p = 0.04).
Conclusions: :
SS-OCT enables clear visualization of deep structures of the optic disc. Decrease in the depth of the lamina cribrosa and thickening of prelaminar neural tissue were observed after IOP reduction by glaucoma surgery.
Keywords: lamina cribrosa • intraocular pressure • imaging/image analysis: clinical