Preoperative Retinal Nerve Fiber Layer Research Articles

Use of optical coherence tomography to predict visual outcome in parachiasmal meningioma.

The authors investigated the value of retinal nerve fiber layer (RNFL) thickness in predicting visual outcome after surgery for parachiasmal meningioma. Forty-nine eyes of 25 patients who underwent craniotomy and resection of a parachiasmal meningioma were analyzed retrospectively. Visual parameters including visual field (VF) (recorded as the mean deviation [MD]), visual acuity (VA), and RNFL thickness (via optical coherence tomography) were measured before and 1 week, 6 months, and 1 year after surgery. Postoperative visual outcome was compared among the patients with a thin or normal RNFL. A separate analysis of data pertaining to 22 eyes of 13 patients with severe VF defects (MD ≤ -10 dB) was performed to compare visual outcome for those with a thin or normal RNFL. Of the 23 eyes that showed VF improvement, 22 (95.7%) had normal RNFL thickness. The positive predictive value of normal RNFL thickness for VF improvement was 78.6%. The VF of patients with normal RNFL thickness improved in 6 months and continued improving 1 year after surgery (MD -5.9 dB before surgery, -5.5 dB 1 week after surgery, -2.8 dB 6 months after surgery [p < 0.01], and -1.1 dB 1 year after surgery [p < 0.01]). In contrast, those with a thin preoperative RNFL showed deterioration at first and then slower, worse visual recovery after surgery (MD -18.1 dB before surgery, -22.4 dB 1 week after surgery, -21.2 dB 6 months after surgery, and -19.1 dB 1 year after surgery). VA also showed significant progress 6 months after surgery in patients with normal RNFL thickness (0.6 before surgery, 0.7 one week after surgery, 0.9 six months after surgery [p = 0.025], and 0.9 one year after surgery [p = 0.050]) compared to those with a thin RNFL (0.3 before surgery, 0.2 one week after surgery, 0.3 six months after surgery, and 0.4 one year after surgery). Preoperative differences in VF MD and VA were noted between the 2 groups (p < 0.01). Even patients with severe VF defects and normal RNFL thickness improved by 11.1 dB by 1 year after surgery compared with patients with a thin RNFL (-0.01 dB) (p < 0.01). Patients with normal RNFL thickness also did better in VA improvement (from 0.7 to 1.1) than those with a thin RNFL (from 0.2 to 0.3), but these results were not statistically significant. RNFL thickness measured by optical coherence tomography has significant value as a prognostic factor of postoperative visual recovery for parachiasmal meningioma. Patients with normal RNFL thickness before surgery are more likely to have visual improvement after surgery than patients with a thin RNFL.

Resolution of papilledema after endoscopic third ventriculostomy versus cerebrospinal fluid shunting in hydrocephalus: a comparative study

In this study the authors compare the efficacy of endoscopic third ventriculostomy (ETV) versus CSF shunting for resolution of papilledema in hydrocephalus. This comparative case series study recruited 12 patients (24 eyes) with hydrocephalus who underwent either an ETV (Group 1, 6 patients [12 eyes]) or CSF shunt treatment (Group 2, 6 patients [12 eyes]). A complete ophthalmological examination including retinal nerve fiber layer (RNFL) evaluation by optical coherence tomography was provided for all patients before surgery and in the 1st week, 1st month, and 3rd month postoperatively. The 2 groups were compared for quantitative changes in RNFL thickness and, thereby, resolution of papilledema. Statistical evaluation was performed using the Mann-Whitney U-test with the aid of SPSS version 16.0. The mean preoperative RNFL thickness was 259.7 ± 35.8 μm in Group 1 and 244.5 ± 53.4 μm in Group 2 (p = 0.798). The mean decrease in RNFL thickness was 101.3 ± 38.8 μm, 141.2 ± 34.6 μm, and 162.0 ± 35.9 μm in Group 1 versus 97.0 ± 44.6 μm, 143 ± 45.6 μm, and 130.0 ± 59.8 μm in Group 2 for the postoperative 1st week, 1st month, and 3rd month, respectively. There was no significant difference between the two groups with respect to decrease in RNFL thickness during the 1st week, 1st month, and 3rd month (p = 0.563, p = 0.753, and p = 0.528, respectively). This is the first study to quantitatively evaluate papilledema in assessing the success of ETV and CSF shunting. The authors' results indicated that ETV is as effective as CSF shunting with respect to decreasing intracranial pressure and resolution of papilledema.

Comparisons of cone electroretinograms after indocyanine green-, brilliant blue G-, or triamcinolone acetonide-assisted macular hole surgery

To compare the function of retinal ganglion cells (RGCs) using the photopic negative response (PhNR) in patients who had undergone indocyaine green (ICG)-assisted, brilliant blue G (BBG)-assisted, or triamcinolone acetonide (TA)-assisted internal limiting membrane (ILM) peeling during macular hole (MH) surgery. Forty-eight eyes of 48 patients with a macular hole were randomly divided into those undergoing ICG-assisted, BBG-assisted, or TA-assisted vitrectomy (n = 16 for each group). Full-field cone ERGs were recorded before and 1, 3, 6, 9, and 12months postoperatively. The amplitudes and implicit times of the a-waves and b-waves and the amplitudes of the oscillatory potentials (OPs) and PhNRs were measured. The mean deviations (MDs) of standard automated perimetry and the best-corrected visual acuity (BCVA) were measured. The circumferential retinal nerve fiber layer (RNFL) thickness was evaluated by SD-OCT. All macular holes were closed with a significant improvement of the BCVA and MD without differences among the groups. There was no significant difference between the preoperative and postoperative RNFL thickness. The implicit times of the a-waves and b-waves were significantly prolonged, and the ΣOPs amplitude was significantly decreased postoperatively in all groups. These ERG changes were not significantly different among the groups. The postoperative PhNR amplitudes were significantly lower in the ICG group than in the BBG or TA group. The results indicate that the PhNR may detect subclinical impairments of RGCs caused by the possible toxic effect of ICG. This finding adds to the data that BBG and TA may be safer than ICG for use during MH surgery.

CHANGES OF PARAFOVEAL RETINAL NERVE FIBER LAYER THICKNESS ANALYZED BY SPECTRAL-DOMAIN OPTICAL COHERENCE TOMOGRAPHY AFTER PARS PLANA VITRECTOMY

To use spectral-domain optical coherence tomography to evaluate the postoperative retinal nerve fiber layer (RNFL) thickness changes in eyes undergoing vitrectomy. This is a retrospective study of 44 patients (44 eyes) who underwent monocular vitrectomy for an epiretinal membrane (19 eyes), macular hole (12 eyes), or vitreous hemorrhage (13 eyes). Quantitative analysis of the peripapillary RNFL by spectral-domain optical coherence tomography was performed before surgery and for 6 months postoperatively on both eyes. Mean patient age was 62.72 ± 9.11 years. Mean preoperative RNFL thickness did not differ significantly between vitrectomized eyes (88.33 ± 13.23 μm) and nonvitrectomized fellow eyes (87.49 ± 13.18 μm; P > 0.05). In vitrectomized eyes, the preoperative mean RNFL thickness in the superior quadrant was significantly different from that at 6 months after surgery (P = 0.02). Vitrectomized eyes with a macular hole showed significant changes in the mean RNFL thickness in the inferior quadrant (P = 0.04). Retinal nerve fiber layer thickness was reduced in some of the quadrants of the vitrectomized eye during the 6-month postoperative follow-up period. Spectral-domain optical coherence tomography can be clinically useful for detection of localized RNFL defects in patients who underwent vitrectomy. Future prospective studies with more patients and longer follow-up duration are required.

Changes in retinal nerve fiber layer thickness following mechanical microkeratome-assisted versus femtosecond laser-assisted LASIK

PurposeTo study the influence of the transient elevation of intraocular pressure during suction in laser-assisted in situ keratomileusis (LASIK) on the retinal nerve fiber layer (RNFL) thickness both in microkeratome assisted and femotsecond (FS) LASIK.Patients and methodsAn interventional case series that included 40 eyes suffering from myopia who were candidates for LASIK. All underwent Wave Front Guided LASIK by the same surgeon using the VisX CustomVue platform. A corneal flap was created in 20 eyes using a mechanical microkeratome Moria M2 (MMK), while the IFS IntraLase™ was used in the remaining 20 eyes. Mean suction time was recorded from “Suction ON” to “Suction OFF” time. Optic cube and RNFL thickness analysis using Spectral Domain Optical Coherence Tomography (SD-OCT) Cirrus-HD was completed before, and 1 month after LASIK.ResultsThe study included 40 eyes of 20 patients. All were females with mean age 33.5 ± 6.4 years. Mean preoperative spherical equivalent was −3.62 ± 2.31D. Average preoperative RNFL thickness was 94.6 ± 12.1μm in MMK group while the postoperative average thickness was 95.1 ± 11.9 um with no statistically significant difference (P-value: 0.37). Average preoperative RNFL thickness was 108.28 ± 8.4 μm in FS group compared to 108.38 ± 11.2 μm in the postoperative average with no statistically significant difference (P-value: 0.94). Mean “Suction ON” to “Suction OFF” time was 22 seconds in the MMK group compared to 41 seconds in the FS group.ConclusionThe rise of intraocular pressure during application of suction ring in LASIK surgery does not affect the RNFL thickness as measured by SD-OCT, whether the flap is created by MMK or FS.

Analysis of Retinal Ganglion Cell Complex Thickness After Brilliant Blue-Assisted Vitrectomy for Idiopathic Macular Holes

Purpose: The purpose of this study was to evaluate retinal ganglion cell complex (GCC) thickness changes in eyes undergoing Brilliant Blue-assisted macular hole surgery (MHS) using Fourier-domain optical coherence tomography (FD-OCT).Materials and Methods: This is a prospective, comparative, and observational case series of 70 eyes in 70 consecutive patients with idiopathic macular holes who underwent vitrectomy between December 2010 and October 2011. The study group consisted of 44 eyes in 44 patients, who underwent MHS with Brilliant Blue-assisted internal limiting membrane (ILM) peeling; 26 eyes in 26 patients, who underwent MHS without ILM peeling, constituted the control group. In both groups, complete ophthalmologic examinations and quantitative analysis of the GCC and retinal nerve fiber layer (RNFL) thicknesses were performed before and after the procedures using OCT. The findings from both groups were compared.Results: Six months after surgery, the rate of closure of macular holes evaluated by OCT was 80.7% in the control group and 97% in the study group. There was no significant difference between preoperative and postoperative GCC and RNFL thickness values in both groups.Conclusions: No significant decrease was observed in the thickness values of the retinal GCC and RNFL after Brilliant Blue-assisted ILM peeling for MHS. Therefore, this surgical procedure can be performed safely for the treatment of macular holes.

Effect of Cataract and its Removal on Signal Strength and Peripapillary Retinal Nerve Fiber Layer Optical Coherence Tomography Measurements

To assess the effect of cataract on optical coherence tomography (OCT), signal strength (SS), and peripapillary retinal nerve fiber layer (RNFL) thickness measurements. Peripapillary RNFL thickness measurements were obtained by Stratus OCT scans using the Fast RNFL thickness (3.4) acquisition protocol before and after cataract extraction in 45 patients with cataract, including 23 glaucoma patients. Cataracts were graded according to the Lens Opacities Classification System III. The postoperative RNFL thickness and SS were 9.3% (P=0.001) and 24.1% (P<0.001) higher than before surgery, respectively. There was greater postoperative change in RNFL thickness measurements in patients with lower preoperative RNFL measurements (r=-0.63, P<0.001) and SS (r=-0.59, P<0.001). Eyes with preoperative SS more than 6 had no significant difference between precataract and postcataract surgery RNFL thickness (P=0.14). There was no significant difference in RNFL thickness change between eyes with cataract only (10.9±20.8 μm) and those with cataract and glaucoma (7.0±14.7 μm; P=0.81). Cataracts may decrease peripapillary RNFL thickness measurements and the SS on OCT scans. Thinning of the peripapillary RNFL suggestive of glaucomatous progression may be the result of artifact from advancing cataract rather than actual structural changes in the peripapillary RNFL. Peripapillary RNFL thickness measurements should be interpreted with caution in glaucomatous eyes with significant cataract, particularly if the SS is attenuated.

Influence of Cataract on Time Domain and Spectral Domain Optical Coherence Tomography Retinal Nerve Fiber Layer Measurements

To assess and compare the influence of cataract on measurements of retinal nerve fiber layer (RNFL) thickness by time domain (TD) optical coherence tomography (OCT) and spectral domain (SD) OCT. Patients who underwent uncomplicated cataract surgery were consecutively enrolled in this study. The peripapillary RNFL thickness was measured before and 8 weeks after cataract surgery using TD-OCT and SD-OCT during the same visit. Changes in the RNFL thickness measurement and signal strength (SS) after cataract surgery were evaluated. A total of 54 patients (54 eyes) were included. After excluding 19 eyes owing to poor imaging or low SS (<5), scans of 35 eyes were included in the final analysis. A significant difference was identified between the preoperative and postoperative SS values using SD-OCT, but not TD-OCT (P=0.002 and 0.789, respectively). The changes in RNFL thickness after cataract surgery were more prominent and frequent for SD-OCT than TD-OCT. There was a significant correlation between change in preoperative RNFL thickness and SS changes for both TD-OCT (r=0.410, P<0.001) and SD-OCT (r=0.246, P=0.002). The presence of cataract significantly affects RNFL thickness measurements by SD-OCT and TD-OCT. SD-OCT, which demonstrated more consistent change of RNFL measurements after cataract extraction, is not necessarily associated with lower RNFL thickness measurement performance in cataract cases, as more participants with cataract were excluded because of poor image quality or low SS, which was more associated with TD-OCT than SD-OCT.

Evaluation of the retinal nerve fiber layer measurements, after photorefractive keratectomy and laser in situ keratomileusis, using scanning laser polarimetry (GDX VCC)

To evaluate the impact of photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK), on retinal nerve fiber layer (RNFL) measurements, by means of scanning laser polarimetry (SLP) GDx VCC (with variable corneal compensation). Two groups of 119 myopic patients each were treated by PRK and LASIK respectively; one eye of each patient was randomly selected for the study. RNFL measurements (around the entire calculation circle) was performed in all eyes 1 day before and 1, 3, 6 and 12 months after treatment by using SLP GDx VCC. Corneal compensation was performed in all eyes preoperatively, and in every examination step postoperatively, in order to neutralize the new corneal birefringence. No statistical differences were found between the PRK and LASIK groups, in all preoperative and postoperative RNFL measurements. Only the p values for CCT and mean K-readings preoperatively were statistically significant. PRK and LASIK do not seem to influence the RNFL measurements at 1st, 3rd, 6th and 12th postoperative months when measured with SLP GDx VCC. The corneal compensation reset is necessary in every step of the examination in order to have reproducible results.

In Vivo Retinal Nerve Fiber Layer Thickness Measured by Optical Coherence Tomography Predicts Visual Recovery after Surgery for Parachiasmal Tumors

Restoration of visual function after neurosurgery for parachiasmal tumors is variable and unpredictable. The current study was conducted to determine whether in vivo retinal nerve fiber layer (RNFL) thickness measurements predict the visual recovery of such patients. Forty patients undergoing surgical resection of parachiasmal lesions were prospectively assessed before surgery with a neuro-ophthalmic examination, involving standard automated visual field (VF) testing and optical coherence tomography (OCT) measurements of RNFL thickness, which was the prespecified marker for axonal loss. Tests were repeated within 6 weeks after surgery. Thinner preoperative RNFL thickness was associated with worse visual acuity (VA) and VF mean deviation (MD). Patients with normal preoperative RNFL had significant improvement in mean VA after surgery, from 20/40 to 20/25 (P = 0.028), whereas patients with thin RNFL did not improve (20/80 to 20/60, P = 0.177). Eyes with normal RNFL showed improvement in MD (-7.0 dB before surgery, -3.5 dB after surgery, P = 0.0007) unlike eyes with thin RNFLs, which had no significant improvement after surgery (-15.3 dB before and -13.3 dB after surgery, P = 0.191). RNFL thickness increased by 1% after surgery among all eyes (P = 0.04). Eyes with severe VF defects (MD </= -10 dB) but normal preoperative RNFL thickness showed a postoperative improvement in MD of 14.6 dB compared with 1.6 dB (P < 0.0001) in eyes with thin RNFL before surgery, despite no difference in MD before surgery (normal RNFL MD, -22.3 dB; thin RNFL MD, -20.8 dB; P = 0.7). Patients who have objectively measurable RNFL loss at the time of surgery for chiasmal compressive lesions are less likely to have return of VA or VF after surgery.

The Effect of Phacoemulsification Cataract Surgery on the Measurement of Retinal Nerve Fiber Layer Thickness Using Optical Coherence Tomography

Purpose: To evaluate whether the measurement of retinal nerve fiber layer (RNFL) thickness using optical coherence tomography (OCT) changes after cataract surgery. Methods: This prospective, randomized, observational, cross-sectional clinical study included 24 eyes of 24 patients who underwent phacoemusification with implant. All patients had no preexisting retinal or optic nerve pathology or other media opacities that might influence the RNFL thickness. The classification and the grading of cataract were based on the Lens Opacities Classification System III (LOCS III). All eyes were scanned immediately before cataract surgery with OCT using Fast RNFL program. All eyes had circular scans around the optic disk with a diameter of 3.4 mm. The OCT was repeated 4 weeks after surgery when the patients returned for postoperative check using the same programme. Results: The mean preoperative RNFL thickness was 84.9 ± 16.5. The postoperative mean RNFL thickness was 93.0 ± 17.6. The pre-and postoperative values of the mean RNFL and signal/noise ratio (SNR) are statistically significant (P < 0.05). Conclusions: Lens opacities may affect the image quality of OCT scans used to measure RNFL thickness as indicated by preoperative low SNR. Cataract extraction results in an apparent increase of the RNFL thickness.