Optical coherence tomography assessment of retinal nerve fiber layer thickness changes after glaucoma surgery

Abstract

Purpose-To assess changes in retinal nerve fiber layer (NFL) thickness in glaucoma patients after filtration surgery by using optical coherence tomography (OCT). Design-Retrospective observational case series.Participants-Thirty-eight eyes of 31 glaucoma patients who underwent trabeculectomy or a combined procedure of cataract extraction and trabeculectomy were evaluated retrospectively.Methods-Eyes were imaged with OCT before surgery (1 week to 6 months before surgery; mean ± standard deviation [SD], 71.3 ± 61.2 days) and after surgery (6-12 months after surgery; 247.2 ± 63.5 days) to measure peripapillary NFL thickness.Main Outcome Measures-Changes in mean and segmental NFL thickness with respect to age, postoperative change in intraocular pressure (IOP), preoperative visual field test global indices, and change in visual field global indices.Results-A significant increase in the overall mean NFL thickness was present after surgery (P < 0.0001). Segmental analysis found a significant increase in NFL thickness in the nasal, superior, and temporal quadrants. IOP decreased after surgery from 22.0 ± 6.4 mmHg to 11.4 ± 4.7 mmHg (mean ± SD). Twenty-eight (73.7%) of 38 eyes had an IOP reduction >30%. The mean NFL thickness increase (0.5-μm/mmHg decrease of IOP) was significantly correlated with the IOP reduction (r = −0.41; P = 0.03). No correlation was found between NFL thickness changes and age, preoperative visual field global indices, or change in visual field global indices.Conclusions-A significant increase of the mean NFL thickness, which was related to IOP reduction, was detected after glaucoma filtration surgery.Reversal of glaucomatous damage to the optic nerve head (ONH) and the retinal nerve fiber layer (NFL) after intraocular pressure (IOP)-decreasing treatments has been documented in congenital and infantile glaucoma and in chronic open-angle glaucoma in adults. 1-10 Studies investigating reversal of ONH cupping in experimental models and in human subjects after IOP reduction by medical and surgical treatments have been performed by evaluating In this study, we retrospectively assessed changes in NFL thickness after filtration surgery by using optical coherence tomography (OCT), which is a noninvasive and reproducible technique that permits high-resolution cross-sectional imaging of the retina. 12,13 Previous studies assessing the retinal and macular thickness changes as determined by OCT after cataract extraction surgery did not find any significant change. 14,15 Assuming that NFL thickness also does not change after cataract surgery, we combined the data obtained from trabeculectomy or combined cataract extraction and trabeculectomy groups for this study. Materials and MethodsSubjects enrolled in the study were consecutive glaucoma patients who underwent trabeculectomy or combined surgery of phacoemulsification and trabeculectomy at the New England Eye Center, Boston, Massachusetts, from November 1994 to October 1999. Informed consent approved by the New England Medical Center Human Investigat...

Optical coherence tomography, frequency-doubling technology, and colour Doppler imaging in ocular hypertension

“…Recent studies suggest that the variations in RNFL thickness are correlated with variations in IOP, that is, for each reduction of 1 mmHg in IOP, there is an increase in RNFL of 0.5 mm. 42 These data are, however, much debated since, although they are confirmed by some experimental studies, 43,44 frequently in single sectors, 45 in others no optic nerve modifications related to pressure variations have been found. 46,47 It is still not clear what causes an improvement in the RNFL following a reduction in IOP.…”

Change of foveal and perifoveal thickness measured by OCT after phacoemulsification and IOL implantation

“…16 A major increase in the retinal nerve fibre thickness (Po0.0001) was found as the IOP decreased from 22.0 to 11.4 mmHg. Although the exact pathomechanism is not known, it is assumed that the lamina cribrosa moves forward as the consequence of decrease of the IOP and so the nerve fibre layer may regain its original shape and thickness, until the glaucomatous changes are not irreversible.…”

Rates of retinal nerve fibre layer thickness change in glaucoma patients and control subjects

“…Previous studies have reported that cataract surgery results in an increase in measured RNFL retardance and thus SLP-measured RNFLT. [21][22][23] Reports on the systematic differences of measured RNFLT pre-and post trabeculectomy are conflicting for OCT, 24,25 and have been shown not to be significant for SLP. 26 In light of these findings, data from eyes with glaucoma surgery during follow-up were analysed, whereas those from eyes with cataract surgery were not.…”