Reproducibility and repeatability of ganglion cell-inner plexiform layer thickness measurements in healthy subjects

Human Amniotic Membrane Plug to Restore Age-Related Macular Degeneration Photoreceptor Damage

PURPOSE

Age-related macular degeneration (AMD) is the leading cause of legal blindness in adults 65 years of age and older. Choroidal neovascularization (CNV) can complicate AMD and lead to severe visual acuity reduction. Despite the several treatments available, if the retinal pigment epithelium is damaged, we have to cope with the impossibility of restoring acceptable visual acuity using only medical treatments.

DESIGN

Prospective, consecutive, interventional study.

PARTICIPANTS

Eleven patients affected by AMD, 6 patients affected by CNV, and 5 patients affected by geographic atrophy.

METHODS

All patients underwent a pars plana vitrectomy with subretinal implantation of human amniotic membrane (hAM) to induce photoreceptor regeneration and partial visual acuity restoration.

MAIN OUTCOME MEASURES

Primary study outcome was visual acuity improvement. Secondary outcomes were multimodal imaging results.

RESULTS

Mean preoperative best-corrected visual acuity (BCVA) was 20/2000 (2 logarithm of the minimum angle of resolution [logMAR]), and all the patients showed a BCVA of counting fingers or less. Mean final BCVA was 20/400 (1.31 logMAR), ranging from 20/2000 to 20/100 (2-0.7 logMAR). OCT angiography was used to measure retinal vascularization in the treated eye compared with the fellow eye. A high correlation between BCVA and deep vascular density was evidenced. Adaptive optics findings, obtained over the retinal area where the highest functionality was observed, were evaluated using microperimetry. The images showed possible photoreceptor presence over the hAM membrane.

CONCLUSIONS

This work supports the feasibility and safety of the hAM to promote partial retinal function restoration 6 months after surgery with visual acuity improvement. The advanced diagnostics help to understand the interaction between the hAM and photoreceptors and suggest that photoreceptor regeneration may occur.

Foveal avascular zone area and parafoveal vessel density measurements in different stages of diabetic retinopathy by optical coherence tomography angiography

AIM

To investigate foveal avascular zone (FAZ) and parafoveal vessel densities (PRVD) by means of optical coherence tomography angiography (OCTA) in diabetic patients with or without diabetic retinopathy (DR) and to assess the reproducibility of FAZ and PRVD measurements.

METHODS

Sixty diabetic patients (60 eyes) with different stage of DR (graded according to the International Clinical Severity Scale for DR) and 20 healthy subjects underwent FAZ area and PRVD measurements using OCTA by two experienced examiners. FAZ area in all patients was also assessed using fluorescein angiography (FA).

RESULTS

In subject with proliferative DR and with moderate-severe non proliferative DR, FAZ area was significantly increased compared to healthy controls (P=0.025 and P=0.050 respectively measured with OCTA and P=0.025 and P=0.048 respectively measured with FA). OCTA showed significantly less inter-observer variability compared to FA. Concordance correlation coefficient (CCC) for FAZ area measurements was 0.829 (95%CI: 0.736-0.891) P<0.001 with FA and 1.000 (95%CI: 0.999-1.000) P<0.001 with OCTA. CCC was 0.834 (95%CI: 0.746-0.893) P<0.001 and 0.890 (95%CI: 0.828-0.930) P<0.001 for parafoveal superficial and deep vessel density measurements, respectively.

CONCLUSION

OCTA shows progressive increase of FAZ area and reduction of PRVD in both superficial and deep plexus at increasing DR severity. FAZ area and PRVD measurements using OCTA are highly reproducible.

Postreceptor Neuronal Loss in Intermediate Age-related Macular Degeneration

PURPOSE

To investigate the relationship between ganglion cell complex (GCC) thickness and photoreceptor alterations in eyes with intermediate age-related macular degeneration (AMD).

DESIGN

Retrospective case-control study.

METHODS

We collected data from 68 eyes with intermediate AMD from 68 patients with spectral-domain optical coherence tomography (SDOCT) imaging. A control group of 50 eyes from 50 healthy subjects was included for comparison. Our main outcome measures for comparison between groups were (1) the average and minimum GCC thickness and (2) the "normalized" reflectivity of the ellipsoid zone (EZ) en face image.

RESULTS

The average and minimum GCC thicknesses were thinner in AMD patients (69.54 ± 9.30 μm and 63.22 ± 14.11 μm, respectively) than in healthy controls (78.57 ± 6.28 μm and 76.28 ± 6.85 μm, P < .0001 and P < .0001, respectively). Agreement was found to be excellent in the "normalized" EZ reflectivity assessment (intraclass correlation coefficient = 0.986, coefficient of variation = 1.11). The EZ "normalized" reflectivity was 0.67 ± 0.11 in controls and 0.61 ± 0.09 in the AMD group (P = .006). In univariate analysis, EZ "normalized" reflectivity was found to have a significant direct relationship with average (P < .0001) and minimum (P < .0001) GCC thickness in AMD patients, but not in controls (P = .852 and P = .892, respectively).

CONCLUSIONS

Eyes with intermediate AMD exhibit GCC thinning, as well as a reduced EZ "normalized" reflectivity, and these parameters are correlated. This study supports the concept of postreceptor retinal neuronal loss as a contributor to retinal thinning in intermediate AMD.

Repeatability and Reproducibility of Retinal Neuronal and Axonal Measures on Spectral-Domain Optical Coherence Tomography in Patients with Cognitive Impairment

Background

With increasing interest in determining if measurement of retinal neuronal structure with spectral-domain optical coherence tomography (SD-OCT) is useful in accessing neurodegenerative process in cognitive decline and development of dementia, it is important to evaluate whether the SD-OCT measurements are repeatable and reproducible in these patients.

Methods

This is a retrospective cohort study. Patients with Alzheimer’s disease (AD) or mild cognitive impairment (MCI) with no change in global clinical dementia rating (CDR) score at 1-year follow-up were eligible to be included. Ganglion cell-inner plexiform layer (GC-IPL) and retinal nerve fiber layer (RNFL) parameters were measured with SD-OCT at baseline, 6-month, and 1-year follow-up visits. At baseline, SD-OCT scans were repeated to access intra-visit repeatability of the SD-OCT measurement. SD-OCT measurement over three visits was used to access inter-visit reproducibility. We calculated intraclass correlation coefficients (ICC) and coefficients of variation (CoVs).

Results

We included 32 patients with stable AD and 29 patients with stable MCI in the final analysis. For GC-IPL measures, the average intra-visit ICC was 0.969 (range: 0.948–0.985), and CoV was 1.81% (range: 1.14–2.40); while the average inter-visit ICC was 0.968 (0.941–0.985), and CoV was 1.91% (range: 1.24–2.32). The average ICC and CoV of intra-visit RNFL measured were 0.965 (range: 0.937–0.986) and 2.32% (range: 1.34–2.90%), respectively. The average ICC and CoV of inter-visit RNFL measures were 0.927 (range: 0.845–0.961) and 3.83% (range: 2.71–5.25%), respectively.

Conclusion

Both GC-IPL and RNFL measurements had good intra-visit repeatability and inter-visit reproducibility over 1 year in elderly patients with no decline in cognitive function, suggesting that SD-OCT is a reliable tool to assess neurodegenerative process over time.

Macular Ganglion Cell Layer Assessment to Detect Glaucomatous Central Visual Field Progression

Purpose

To investigate the use of ganglion cell inner plexiform layer (GC-IPL) thickness, as measured by spectral domain optical coherence tomography, to detect central visual field (VF) progression.

Methods

This study included 384 eyes from 384 patients (219 preperimetric and 165 perimetric glaucomatous eyes; average follow-up, 4.3 years). Photographic assessment of retinal nerve fiber layer (RNFL) and serial VF analysis were performed to detect glaucoma progression in the central (within 10°) area. Study inclusion required at least five serial spectral domain optical coherence tomography exams at different visits. The long-term test-retest variability of average GC-IPL thicknesses was calculated in 110 stable preperimetric glaucomatous eyes. The sensitivity and specificity of GC-IPL measurements for the detection of central VF progression were calculated in an event-based analysis using the calculated variability as a cut-off and were compared with those of central RNFL photographic assessment.

Results

The intersession test-retest variability, defined as the 95% confidence interval, was 1.76 µm for average GC-IPL thickness. The sensitivity and specificity of the average GC-IPL thickness for detecting central VF progression were 60.7% and 78.9%, respectively. Among six sectors, the inferonasal GC-IPL sector showed the highest sensitivity (53.6%). The sensitivity of the ≥1 sector GC-IPL to detect central VF progression was significantly higher than that of central RNFL photographic progression (p = 0.013). Other GC-IPL parameters showed comparable sensitivity and specificity to detect central VF progression compared with RNFL photographic progression.

Conclusions

Serial GC-IPL measurements show comparable performance in the detection of central glaucomatous VF progression to RNFL photographic assessment.

Local Variability of Macular Thickness Measurements With SD-OCT and Influencing Factors

Purpose

To compare the intrasession variability of spectral-domain optical coherence tomography (SD-OCT)-derived local macular thickness measures and explore influencing factors.

Methods

One hundred two glaucomatous eyes (102 patients) and 21 healthy eyes (21 subjects) with three good quality macular images during the same session were enrolled. Thickness measurements were calculated for 3° superpixels for the inner plexiform (IPL), ganglion cell (GCL), or retinal nerve fiber layers (mRNFL), GC/IPL, ganglion cell complex, and full macular thickness. Spatial distribution and magnitude of measurement errors (ME; differences between the 3 individual superpixel values and their mean) and association between MEs and thickness, age, axial length, and image quality were explored.

Results

MEs had a normal distribution with mostly random noise along with a small fraction of outliers (1.2%–6.6%; highest variability in mRNFL and on the nasal border) based on M-estimation. Boundaries of 95% prediction intervals for variability reached a maximum of 3 μm for all layers and diagnostic groups after exclusion of outliers. Correlation between proportion of outliers and thickness measures varied among various parameters. Age, axial length, or image quality did not influence MEs (P > 0.05 for both groups).

Conclusions

Local variability of macular SD-OCT measurements is low and uniform across the macula. The relationship between superpixel thickness and outlier proportion varied as a function of the parameter of interest.

Translational Relevance

Given the low and uniform variability within and across eyes, definition of an individualized ‘variability space' seems unnecessary. The variability measurements from this study could be used for designing algorithms for detection of glaucoma progression.