Correlating Structural and Functional Damage in Glaucoma.

Structural and functional tests are essential for detecting and monitoring glaucomatous damage. However, the correlations between structural and functional tests in glaucoma are complex and faulty, with the combination of both modalities being recommended for better assessment of glaucoma. The objective of this review is to explore investigations from the last 5 years in the field of structure-function correlation in glaucoma that contributed to increment in the understanding of this correlation and have the potential to improve the diagnosis and detection of glaucoma progression.

Influence of Bruch's Membrane Opening Area in Diagnosing Glaucoma With Neuroretinal Parameters From Optical Coherence Tomography.

PURPOSE: To determine whether the glaucoma diagnostic accuracy of age- and Bruch membrane opening area (BMOA)-adjusted normative classifications of minimum rim width (MRW) and retinal nerve fiber layer thickness (RNFLT) is dependent on BMOA, in a European descent population. DESIGN: Retrospective, cross-sectional study. METHODS: We included 182 glaucoma patients and 166 healthy controls for the primary study, and 105 glaucoma patients in a second sample used for a replication study. Optical coherence tomography (Spectralis) measurements of BMOA, global MRW, and RNFLT and normative classifications from the device software were exported for analysis. Sensitivity and specificity were calculated for a conservative criterion (abnormal = "outside normal limits" classification) and a liberal criterion (abnormal = "outside normal limits" or "borderline" classifications). The dependence of sensitivity and specificity on BMOA was analyzed with comparison among subgroups divided by tertiles of BMOA, and with logistic regression. RESULTS: For the conservative criterion, MRW sensitivity was independent of BMOA (P ≥ .76), while RNFLT sensitivity increased in the large BMOA subgroup (P = .04, odds ratio: 1.2 per mm2 [P = .02]). For the liberal criterion, MRW and RNFLT sensitivities were independent of BMOA (P ≥ .53). Specificities were independent of BMOA (P ≥ .07). For the replication sample, which included younger patients with larger BMOA and worse visual field damage than the primary sample, sensitivities were independent of BMOA for both criteria (P ≥ .10). CONCLUSIONS: RNFLT sensitivity was higher in eyes with larger BMOA; however, age and visual field damage may influence that association. MRW diagnostic accuracy was not dependent on BMOA.

Clinical relevance of protruded retinal layers in minimum rim width measurement of the optic nerve head.

BACKGROUND/AIMS: Optical coherence tomography (OCT) imaging of the optic nerve head minimum rim width (MRW) has recently been shown to sometimes contain components besides extended retinal nerve fibre layer (RNFL). This study was conducted to determine whether excluding these components, termed protruded retinal layers (PRLs), from MRW increases diagnostic accuracy for detecting glaucoma. METHODS: In this cross-sectional study, we included 123 patients with glaucoma and 123 normal age-similar controls with OCT imaging of the optic nerve head (24 radial scans) and RNFL (circle scan). When present, PRLs were manually segmented, and adjusted MRW measurements were computed. We compared diagnostic accuracy of adjusted versus unadjusted MRW measurement. We also determined whether adjusted MRW correlates better with RNFL thickness compared with unadjusted MRW. RESULTS: The median (IQR) visual field mean deviation of patients and controls was -4.4 (-10.3 to -2.1) dB and 0.0 (-0.6 to 0.8) dB, respectively. In the 5904 individual B-scans, PRLs were identified less frequently in patients (448, 7.6%) compared with controls (728, 12.3%; p<0.01) and were present most frequently in the temporal sector of both groups. Areas under the receiver operating characteristic curves and sensitivity values at 95% specificity indicated that PRL adjustment did not improve diagnostic accuracy of MRW, globally or temporally. Furthermore, adjusting MRW for PRL did not improve its correlation with RNFL thickness in either group. CONCLUSION: While layers besides the RNFL are sometimes included in OCT measurements of MRW, subtracting these layers does not impact clinical utility.

Outer retinal layer thickness in patients with glaucoma with horizontal hemifield visual field defects.

BACKGROUND/AIMS: To determine the effect of glaucoma on outer retinal layer thickness in eyes with horizontal hemifield visual field (VF) defects. METHODS: We conducted a cross-sectional study in glaucomatous eyes with repeatable (in three or examinations) horizontal hemifield VF (programme 24-2) defect defined as: all five nasal VF locations immediately either above or below the horizontal midline abnormal in the pattern deviation plot with p<0.5%; no mirror-image adjacent 5 VF locations abnormal in the pattern deviation plot and no non-edge VF locations in the non-affected hemifield abnormal in the pattern deviation plot with p<1%. We used optical coherence tomography to measure thickness of each retinal layer in the temporal macula (12° horizontally and 24° vertically) and computed the absolute (µm) and relative (%) intraindividual asymmetry between the perimetrically normal and abnormal hemimacula. RESULTS: We included 10 eyes of 8 patients with median age of 67 years and median VF mean deviation of -8.85 dB. The nerve fibre, ganglion cell and inner plexiform layers were significantly thinner in the perimetrically abnormal hemimacula (median asymmetry of -6.4, -11.5 and -3.8 µm, (corresponding to -27.7, -40.5 and -15.7 %), respectively, all p≤0.01). The inner nuclear layer was slightly thicker in the perimetrically abnormal hemimacula (median asymmetry of 1.3 µm (5.0 %), p=0.01). The outer plexiform, outer nuclear and photoreceptor layers asymmetry values were negligible. CONCLUSION: Our study showed no evidence that glaucoma has an effect on the outer retinal layer thickness. In contrast, a large impact was observed in inner layer thickness.

Impact of Head Tilt on Optical Coherence Tomography Image Orientation.

PURPOSE: Head tilt can have an impact on the orientation of posterior pole images. We conducted this study to determine the effect of head tilt on image orientation measured by the fovea-Bruch's membrane opening (FoBMO) angle with optical coherence tomography (OCT) imaging. METHODS: The study included 56 healthy subjects with mean (range) age of 33 (18 to 61) years. The dominant eye was first determined. To measure head tilt, a smartphone with a built-in gyroscope was affixed to the subject's head with adjustable straps. OCT imaging was performed in both eyes (in randomized order) at 0, 5, and 10 degrees of head tilt in the direction of the imaged eye (ipsilateral head tilt), and then in the opposite direction (contralateral head tilt). For each image, the device software determined Bruch's membrane opening center and the foveal pit from which the FoBMO angle was derived. RESULTS: Thirty-eight (68%) subjects were right eye dominant and 18 (32%) were left eye dominant. Each 1 degree head tilt resulted in a mean change of 0.76 degree in the FoBMO angle (P<0.01), with no significant difference in effect between the 2 eyes (P=0.72). The magnitude of the effect increased from 5 to 10 degrees, and was similar for both ipsilateral and contralateral head tilt. Ocular dominance did not modulate the effect of head tilt (P=0.42). CONCLUSIONS: Head tilt significantly affects OCT image orientation as measured by the FoBMO angle, presumably because cyclotorsion is not fully compensatory. The magnitude and direction of the effect does not depend on the dominant eye.

Protruded retinal layers within the optic nerve head neuroretinal rim.

PURPOSE: To determine the frequency with which retinal tissues other than the nerve fibre layer, hereafter referred to as protruded retinal layers (PRL), are a component of optical coherence tomography (OCT) neuroretinal rim measurements. METHODS: Ninety healthy (30 White, Black and Japanese, respectively) subjects were included in the study. A radial scan pattern (24 B-scans centred on Bruch's membrane opening [BMO]) was used. For each of the 48 minimum rim width (MRW) measurement points, we determined whether PRL were present, absent or indeterminate. When present, the proportion of PRL within the MRW was quantified. RESULTS: Protruded retinal layers were present in 503 (11.6%), absent in 3805 (88.1%) and indeterminate in 12 (0.3%) measurement points. Overall, 69 (76.6%) subjects had ≥1 points with PRL, with White subjects having the highest frequency and Japanese the lowest (29 [97%] and 18 [60%], respectively; p < 0.01). PRL were present in one-third of points in the temporal sector, but ≤5% in other sectors. When present, the median PRL thickness was 53.0 (interquartile range [IQR]: 33.0 to 78.5) µm, representing 20.6 (IQR: 13.0 to 28.5)% of MRW. Globally, the median PRL thickness comprised 1.3 (IQR: 0.2 to 3.5)% of the MRW; however, in the temporal sector, it exceeded 30% of MRW in some subjects. CONCLUSIONS: Protruded retinal layers are a component of MRW measurements in most normal subjects, occurring in almost 12% of all measurement points analysed. There were racial variations in the presence of PRL and a significantly higher frequency of PRL in the temporal sector.

Long-term Outcome of Surgical Treatment for Late Intraocular Lens Dislocation Associated With High Intraocular Pressure: A Case Series.

PURPOSE: To demonstrate the long-term safety and efficacy of transscleral intraocular lens (IOL) fixation combined with an Ahmed glaucoma drainage device implantation for patients with late IOL dislocation and high intraocular pressure (IOP). METHODS: This is a retrospective report of a series of patients who underwent this combined surgery. The main outcome variables studied were change in visual acuity (VA), IOP, and number of medications compared with preoperative levels. Surgical failure was defined as a decrease in VA of at least 3 Snellen lines, IOP above 20 mm Hg or IOP reduction <25% from preoperative levels at ≥2 consecutive visits, at least 2 months apart. RESULTS: Eleven patients with median age of 83 years (range, 77 to 92 y) were included in the study. All patients had a previous diagnosis of pseudoexfoliation. After a median follow-up time of 1.75 years (range, 0.83 to 2.5 y), the median IOP decreased from 33 mm Hg (range, 24 to 47 mm Hg) to 13 mm Hg (range, 5 to 16 mm Hg; P<0.01). The number of glaucoma medications also decreased from 3 (range, 1 to 4) to 2 (range, 0 to 4; P=0.03). The median log MAR VA improved from 0.77 (range, 0.3 to 2) preoperatively to 0.44 (range, 0 to 3) postoperatively (P=0.27).Four patients had postoperatory surgical complications: choroidal effusion (2), vitreous hemorrhage and hyphema (1), vertical diplopia (1). The survival probability over 2.5 years was 90.9% (confidence interval, 75.4%-100%). CONCLUSION: Transscleral IOL fixation associated with Ahmed glaucoma drainage device implantation is a safe and effective surgical option for patients with late IOL dislocation and elevated IOP.