Foveal Shape and Structure in a Normal Population

Characteristic deviations of the optic disc and macula in optic nerve hypoplasia based on OCT

PURPOSE

The purpose of this study was to evaluate the optic disc and macula in a large cohort of patients with different severity of optic nerve hypoplasia (ONH) using high-resolution spectral domain optical coherence tomography (SD-OCT).

METHODS

In total, 36 patients (52 ONH eyes and 17 fellow eyes in unilateral cases) and 45 healthy right eyes from 45 controls were evaluated. All patients underwent an examination to confirm the diagnosis. SD-OCT images of the disc and macula were obtained and analysed both quantitatively and qualitatively.

RESULTS

OCT in ONH eyes demonstrated a shorter disc diameter (1061 ± 375 μm vs. 1751 ± 221 μm, p < 0.001), shallower mean cup depth (427 ± 171 μm vs. 551 ± 152 μm, p = 0.01), thinner ganglion cell complex (GCC) perifoveally (47.3 ± 13.0 μm, 60.8 ± 6.0 μm, p < 0.001) and reduced foveal depth (61 ± 36 μm, 119 ± 19 μm, p < 0.001) compared to control eyes. Qualitative analysis showed that 1/3rd of ONH eyes lacked signs of an optic cup, and 2/3rd had reduced or no sign of a foveal pit. Fellow eyes had shorter disc diameter (1446 ± 404 μm vs. 1751 ± 221 μm, p = 0.004) and reduced foveal depth (93 ± 27 μm vs. 119 ± 19 μm, p < 0.001) but similar GCC thickness (60.8 ± 7.1 μm vs. 60.8 ± 6.0 μm, p = 0.738) compared to controls. Disc diameter showed the best correlation with visual acuity in ONH eyes (ρ = 0.517, p < 0.001).

CONCLUSION

ONH eyes have reduced GCC thickness and reduced or no foveal pit. Fellow eyes in presumed unilateral cases have a smaller disc diameter and reduced foveal depth compared to controls, suggesting the possibility of subclinical/mild disease. However, GCC thickness was normal. The correlation between structure and visual function is not always straightforward.

Optical coherence tomography angiography in birdshot chorioretinopathy

PURPOSE

To describe the retinal vascular changes in birdshot chorioretinopathy (BSCR) using optical coherence tomography angiography (OCTA) and to compare them with changes in macular thickness.

METHODS

In this multicenter study, patients with a diagnosis of BSCR and a positive HLA-A29 underwent fluorescein angiography, spectral domain optical coherence tomography (SD-OCT), and OCTA. The foveal avascular zone (FAZ) and the area of capillary non-perfusion were manually measured by two examiners in fluorescein angiography (FA) and 3 × 3-mm OCTA images of the superficial retinal layer. These measurements were compared to central retinal thickness. To calculate normal capillary density, we collected data from 22 controls who had OCTA performed on one visit only.

RESULTS

A total of 44 eyes with BSCR were enrolled. The mean automated parafoveal superficial capillary density in BSCR eyes was 0.47 ± 0.03. The differences between the foveal capillary density of BSCR patients and healthy subjects were statistically significant (P < 0.001). The mean area of FAZ manually measured on the 3 × 3 mm unsegmented OCTA images was larger in eyes with BSCR (1.34 ± 0.41 mm2; P < 0.0001). Measurement of FAZ area showed good interobserver (κ 0.88) and intraobserver repeatability (κ 0.79) on OCTA images. The intraclass correlation coefficient for FAZ measurements on FA between the two observers was 0.48. The OCT retinal thickness maps of all BSCR eyes demonstrated statistically significant thinning compared to those of control subjects (P < 0.01).

CONCLUSION

Our study demonstrates the potential contribution of OCTA as a new non-invasive imaging technology that monitors disease activity in BSCR patients.

Foveal thickness and vascular variables in adolescents born moderate-to-late preterm

PURPOSE

It is well established that children born very preterm are at increased risk for ocular abnormalities including altered foveal morphology. However, little is known about how children born moderate-to-late preterm (MLP), gestational age 32 + 0-36 + 6 weeks, are affected later in life. This study investigates foveal avascular zone (FAZ) area, vascular density (VD), central foveal thickness (CFT) and ganglion cell layer thickness (GCL++) of adolescents born MLP without history of retinopathy of prematurity and compare the results with full-term controls.

METHODS

In a prospective population-based cohort study, 50 adolescents (26 girls; mean age 16.5 years) born MLP were examined with optical coherence tomography (OCT) and OCT angiography (OCT-A). FAZ and VD were obtained from OCT-A scans and adjusted for ocular magnification. CFT and GCL++ were obtained from the OCT scans. The results from the MLP individuals were compared with the results from 49 healthy full-term controls (29 girls; mean age 16.7 years).

RESULTS

The results showed statistically significant differences in FAZ area (0.22 vs 0.28 mm2; p = 0.0032) and CFT (198.1 vs 187.1 μm; p = 0.0010) between the MLP group and controls. Strong correlations between FAZ area and CFT (r = -0.773, p < 0.0001) and GCL++ (r = -0.924, p < 0.0001) were found in the MLP group. There were no differences in VD.

CONCLUSIONS

Our results show that adolescents born MLP have a smaller FAZ area and an increased CFT compared with full-term controls. These results indicate that adolescents born MLP have similar parafoveal changes as children born extreme or very preterm.

Optical coherence tomography angiography findings in Williams-Beuren syndrome

PURPOSE

Williams-Beuren syndrome (WBS) is a rare genetic disease characterized by psychomotor delay, cardiovascular, musculoskeletal, and endocrine problems. Retinal involvement, which is not well characterized, has also been described. The purpose of this cross-sectional study is to describe the characteristics in optical coherence tomography (OCT) and OCT-angiography (OCTA) of patients with WBS.

METHODS

We included patients with WBS confirmed by genetic analysis. The patients underwent OCT (30° × 25°, 61 B-scans) and OCTA (10° × 10° and 20° × 20°) examinations, all centered on the. Data on retinal thickness (total, inner and outer layers) and foveal morphology on OCT and vessel and perfusion density in OCTA (VD and PD, respectively) were collected. These data were compared with an age-matched control group.

RESULTS

22 eyes of 22 patients with WBS (10 females, mean age 31.5 years) were included. Retinal thickness (and specifically inner retinal layers) in OCT was significantly reduced in all sectors (central, parafoveal, and perifoveal) compared to the control group (p < 0.001 in all sectors). Fovea in WBS eyes was broader and shallower than controls. The PD and VD in both 10 and 20 degrees of fields in OCTA was significantly reduced in patients with WBS, in all vascular plexa (all p < 0.001).

CONCLUSIONS

This study is the first to quantify and demonstrate retinal structural and microvascular alterations in patients with WBS. Further studies with longitudinal data will reveal the potential clinical relevance of these alterations.

Relationship between long-term visual function and the ratio of foveal avascular zone area in eyes with macular hole and healthy fellow eyes

PURPOSE

This study is to investigate the relationship between long-term changes in the foveal avascular zone (FAZ) and visual function of eyes with macular hole (MH) and compare the relationship between the FAZ of MH eyes and fellow eyes.

METHODS

This study included 31 patients with unilateral MH who underwent vitrectomy and their fellow eyes. Best-corrected visual acuity (BCVA) and metamorphopsia were measured preoperatively and at 1, 3, 6, and 12 months postoperatively. We evaluated retinal parameters using optical coherence tomography (OCT) and the superficial FAZ using OCT angiography. The FAZ ratio was defined as follows: (preoperative FAZ area of the MH eye)/(FAZ area of the fellow eye).

RESULTS

The preoperative FAZ area of MH eyes was 0.42 ± 0.08 mm2, which decreased to 0.24 ± 0.07 mm2 1 month postoperatively (p < 0.001) and slightly increased to 0.25 ± 0.06 mm2 12 months postoperatively (p = 1.000). The FAZ area did not differ significantly from that of fellow eyes (0.39 ± 0.06 mm2, p = 0.281). The FAZ area of MH eyes was not associated with visual function at any time point. The FAZ ratio showed a correlation with the preoperative, 6-month, and 12-month BCVA (r = 0.604, p < 0.001; r = 0.510, p = 0.003; and r = 0.475, p = 0.007, respectively).

CONCLUSIONS

A larger FAZ in the MH eye than that in the fellow eye is associated with poorer long-term visual acuity. The preoperative comparison of the FAZ of the MH eye with that of the fellow eye may be a biomarker for predicting long-term visual acuity.

Peak Cone Density Predicted from Outer Segment Length Measured on Optical Coherence Tomography

PURPOSE

To compare peak cone density predicted from outer segment length measured on optical coherence tomography with direct measures of peak cone density from adaptive optics scanning light ophthalmoscopy.

METHODS

Data from 42 healthy participants with direct peak cone density measures and optical coherence tomography line scans available were used in this study. Longitudinal reflectivity profiles were analyzed using two methods of identifying the boundaries of the ellipsoid and interdigitation zones to estimate maximum outer segment length: peak-to-peak and the slope method. These maximum outer segment length values were then used to predict peak cone density using a previously described geometrical model. A comparison between predicted and direct peak cone density measures was then performed.

RESULTS

The mean bias between observers for estimating maximum outer segment length across methods was less than 2 µm. Cone density predicted from the peak-to-peak method against direct cone density measures showed a mean bias of 6,812 cones/mm2 with 50% of participants displaying a 10% difference or less between predicted and direct cone density values. Cone density derived from the slope method showed a mean bias of -17,929 cones/mm2 relative to direct cone density measures, with only 41% of participants demonstrating less than a 10% difference between direct and predicted cone density values.

CONCLUSION

Predicted foveal cone density derived from peak-to-peak outer segment length measurements using commercial optical coherence tomography show modest agreement with direct measures of peak cone density from adaptive optics scanning light ophthalmoscopy. The methods used here are imperfect predictors of cone density, however, further exploration of this relationship could reveal a clinically relevant marker of cone structure.

Mean Ocular Perfusion Pressure Effect During Pars Plana Vitrectomy on the Foveal Avascular Zone: A Pilot Study

Purpose: To evaluate the effect of mean ocular perfusion pressure on the foveal avascular zone (FAZ) area in eyes with successful retinal detachment (RD) surgery. Methods: This prospective pilot fellow eye-controlled study measured the intraoperative mean ocular perfusion pressure in eyes having surgery for rhegmatogenous RD (RRD). Postoperatively, the FAZ area was measured; the change was calculated as the difference in the FAZ area between the operated eye and the contralateral control eye. Results: The study comprised 8 patients with a mean age (±SD) of 53.38 ± 13.92 years. The mean superficial FAZ area was not different between operated eyes and control eyes, while the deep FAZ area was significantly larger in operated eyes. There was a strong negative correlation between the mean ocular perfusion pressure and the change in the deep FAZ area (Spearman ρ, -0.73; P = .04); the correlation between the mean ocular perfusion pressure and the change in the superficial FAZ area was not significant (Spearman ρ, -0.24; P = .57). A significant linear regression was found between the mean ocular perfusion pressure and the change in the deep FAZ area (R2 = 0.388). The predicted enlargement of the deep FAZ area was 0.03 mm with every 1 mm Hg decrease in the mean ocular perfusion pressure. Conclusions: Lower intraoperative mean ocular perfusion pressure is associated with enlargement of the deep FAZ area in eyes having successful RRD surgery.

Characterizing differences in retinal and choroidal microvasculature and structure in individuals with Huntington's Disease compared to healthy controls: A cross-sectional prospective study

OBJECTIVE

To characterize retinal and choroidal microvascular and structural changes in patients who are gene positive for mutant huntingtin protein (mHtt) with symptoms of Huntington's Disease (HD).

METHODS

This study is a cross-sectional comparison of patients who are gene positive for mHtt and exhibit symptoms of HD, either motor manifest or prodromal (HD group), and cognitively normal individuals without a family history of HD (control group). HD patients were diagnosed by Duke movement disorder neurologists based on the Unified Huntington's Disease Rating Scale (UHDRS). Fovea and optic nerve centered OCT and OCTA images were captured using Zeiss Cirrus HD-5000 with AngioPlex. Outcome metrics included central subfield thickness (CST), peripapillary retinal nerve fiber layer (pRNFL) thickness, ganglion cell-inner plexiform layer (GCIPL) thickness, and choroidal vascularity index (CVI) on OCT, and foveal avascular zone (FAZ) area, vessel density (VD), perfusion density (PD), capillary perfusion density (CPD), and capillary flux index (CFI) on OCTA. Generalized estimating equation (GEE) models were used to account for inter-eye correlation.

RESULTS

Forty-four eyes of 23 patients in the HD group and 77 eyes of 39 patients in the control group were analyzed. Average GCIPL thickness and FAZ area were decreased in the HD group compared to controls (p = 0.001, p < 0.001). No other imaging metrics were significantly different between groups.

CONCLUSIONS

Patients in the HD group had decreased GCIPL thickness and smaller FAZ area, highlighting the potential use of retinal biomarkers in detecting neurodegenerative changes in HD.

Gender- and age-related differences in foveal pit morphology

AIMS

To measure the foveal pit morphology parameters and evaluate their correlations with age and sex.

SETTINGS AND DESIGN

A retrospective cross-sectional matched comparison study in a tertiary center.

METHODS AND MATERIALS

Forty men and 40 age-matched women who had normal macular structures and foveal contours were enrolled. Foveal pit parameters including top width, base width, nasal width, temporal width, minimal thickness, nasal thickness, temporal thickness, nasal height, temporal height, nasal slope, and temporal slope were measured on horizontal B-scan macular optical coherence tomography and compared between men and women.

STATISTICAL ANALYSIS USED

Paired t-tests and Pearson's correlation analysis.

RESULTS

The average patient age was 51.4 ± 17.5 (21-84) years. Women had a wider base width (313.1 ± 68.0 μm vs 266.8 ± 70.9 μm, P = 0.006), wider temporal width (1043.1 ± 245.6 μm vs 968.9 ± 261.0 μm, P = 0.006), thinner nasal thickness (345.6 ± 36.2 μm vs 359.7 ± 35.8 μm, P = 0.048), and flatter temporal slope (11.60 ± 2.52° vs 12.98 ± 2.68°, P = 0.016) than men. With age, the base width (r = 0.35, P = 0.025) and temporal width (r = 0.54, P = 0.0003) tended to be wider and the temporal slope was flatter (r = -0.45, P = 0.003) in women but not men. The minimal thickness tended to be thinner in the elderly group (r = 0.038, P = 0.015).

CONCLUSIONS

Women had a significantly wider base width, wider temporal width, thinner nasal thickness, and flatter temporal slope of the foveal pit than age-matched men. The base width and temporal width were wider and the temporal slope was flatter with age in women but not men.

Novel ophthalmic findings and deep phenotyping in Williams-Beuren syndrome

BACKGROUND/AIMS

To characterise the ocular manifestations of Williams-Beuren syndrome (WBS) and compare these to patients with isolated elastin mediated supravalvular aortic stenosis (SVAS).

METHODS

Fifty-seven patients with a diagnosis of WBS and five with SVAS underwent comprehensive ophthalmic evaluation at the National Institutes of Health from 2017 to 2020, including best-corrected visual acuity, slit-lamp biomicroscopy, optical biometry, dilated fundus examination, optical coherence tomography and colour fundus imaging.

RESULTS

Mean age of the 57 WBS patients was 20.3 years (range 3-60 years). Best-corrected visual acuity ranged from 20/20 to 20/400 with mean spherical equivalent near plano OU. Twenty-four eyes (21.8%) had an axial length (AL) less than 20.5 mm and 38 eyes (34.5%) had an AL measuring 20.5-22.0 mm. Stellate iris and retinal arteriolar tortuosity were noted in 30 (52.6%) and 51 (89.5%) WBS patients, respectively. Novel retinal findings in WBS included small hypopigmented retinal deposits (OD 29/57, OS 27/57) and broad foveal pit contour (OD 44/55, OS 42/51). Of the five patients with SVAS, none had stellate iris or broad foveal pit contour while 2/5 had retinal arteriolar tortuosity.

CONCLUSION

WBS is a complex multisystem genetic disorder with diverse ophthalmic findings that differ from those seen in isolated elastin mediated SVAS. These results suggest other genes within the WBS critical region, aside from ELN, may be involved in observed ocular phenotypes and perhaps broader ocular development. Furthermore, retinal arteriolar tortuosity may provide future insight into systemic vascular findings in WBS.

Retina and microvascular alterations in migraine: a systemic review and meta-analysis

Objective

This study aimed to evaluate the retina and microvascular alterations with optical coherence tomography (OCT) or optical coherence tomography angiography (OCTA) in patients with migraine with aura (MA) and migraine without aura (MO).

Methods

PubMed, Embase, and Cochrane Library databases were searched to find relevant literature on patients with MA or MO using OCT/OCTA devices. The eligible data were analyzed by Stata Software (version 15.0).

Results

There were 16 studies identified, involving 379 eyes with MA, 583 eyes with MO, and 658 eyes of healthy controls. The thickness of the peripapillary retinal nerve fiber layer (pRNFL) of patients with MA decreased significantly in most regions. The foveal avascular zone (FAZ) area and perimeter in MA patients significantly enlarged, while the perfusion density (PD) in the macular deep capillary plexus (mDCP) significantly decreased in the whole image and its subregions except for the fovea, with the PD in radial peripapillary capillary (RPC) decreasing inside the disk. Patients with MO demonstrated a significantly decreased thickness of pRNFL in most regions, and the FAZ parameters were significantly enlarged. No statistical significance was observed in the retina and microvascular features of patients with MA and MO.

Conclusion

The eyes affected by MA and MO demonstrated significantly reduced thickness of pRNFL and enlarged FAZ. Patients with MA showed retinal microvascular impairments, including a decreased PD in mDCP. The OCT and OCTA could detect membrane morphology and circulation status in migraine and might provide the basis for the diagnosis and follow-up of patients with migraine.

Systematic review registration

https://www.crd.york.ac.uk/prospero/, CRD42023397653.

A Photodynamic Therapy Index for Central Serous Chorioretinopathy to Predict Visual Prognosis Using Pretreatment Factors

PURPOSE

This study aimed to establish a treatment index based on functional outcomes of photodynamic therapy (PDT) for central serous chorioretinopathy (CSC).

DESIGN

A retrospective clinical case-control study.

METHODS

This was a single-institute study. Eighty (80) eyes with CSC, who were treated by PDT and whose subretinal fluid resolves within 6 months were divided into two groups: those with poor visual outcome (PVO) (best-corrected visual acuity [BCVA] ≤ 0.5 6 months post-PDT), and the remaining eyes (better visual outcome [BVO]). The areas under the curve (AUC) and cutoff values from receiver operating characteristic curves were examined. These was used to predict the groups using pretreatment BCVA and the thickness of each retinochoroidal layer.

RESULT

Twenty-one (21) eyes were in the PVO group and 59 eyes in the BVO group were included. The AUCs were 0.959 for BCVA, 0.959 for the thickness from the internal limiting membrane to the external limiting membrane (IET), 0.820 for the thickness from the external limiting membrane to the photoreceptor outer segment layer, 0.715 for the subfoveal retinal thickness, and 0.515 for the subfoveal choroidal thickness. The BCVA and IET cut-off values were 0.267 logMAR and 71.5 µm, respectively. Using the combination of the cutoff values of BCVA and IET, the highest values for the sensitivity, specificity, positive predictive value, and negative predictive value were 95.2%, 94.9%, 85.0%, and 98.0%, respectively.

CONCLUSION

The combination of pre-PDT BCVA and IET in CSC can accurately predict the post-treatment visual prognosis. These values could be used as a treatment index of PDT for CSC.

[Clinical and pathophysiological contribution of OCT-angiography to epiretinal membranes]

Epiretinal membranes may lead to centripetal contraction forces on the retina and its vessels. OCT-Angiography (OCT-A) is a recent tool which permits a non-invasive understanding of these vascular changes. This review focuses on the OCT-A findings in idiopathic epiretinal membranes, before and after surgery, and the role of internal limiting membrane peeling. It appears that contraction of the epiretinal membrane is associated with both a reduction in the area and perimeter of the foveal avascular zone and alterations in the superficial and deep capillary plexuses. These changes mainly reflect a vascular shift from the perifoveal to the foveal region, increasing with retinal deformation, but also probable dynamic changes in vascular flow. Membrane peeling allows at least partial improvement of these microvascular parameters. Nevertheless, some limitations of OCT-A, such as segmentation errors on a retina with highly modified architecture, can lead to a selection bias in the studies and should call for caution in the interpretation of the results. Finally, internal limiting membrane peeling contributes to changes in the retinal architecture after surgery, in particular by causing a centripetal movement of the macular capillaries and a displacement of the fovea toward the optic nerve head. This role should be clarified in future studies.

Study of Foveal Avascular Zone Growth in Individuals With Mild Diabetic Retinopathy by Optical Coherence Tomography

Purpose

The purpose of this study was to investigate the association between foveal vessels and retinal thickness in individuals with diabetic retinopathy (DR) and control subjects, and to reveal foveal avascular zone (FAZ) growth in early individuals with DR.

Methods

The regions with a thickness less than 60 µm were marked from the intima thickness maps and named FAZThic. The avascular zones extracted from the deep vascular plexus were designated as FAZAngi. The boundary of the two FAZ forms a ring region, which we called FAZRing. The FAZ growth rate was defined as the ratio of the FAZRing area to the FAZThic area. Thirty healthy controls and 30 individuals with mild nonproliferative DR were recruited for this study.

Results

The FAZThic area in individuals with mild DR and control subjects showed similar distribution. The FAZAngi area in individuals with mild DR are higher than that in control subjects on the whole, but there was no significant difference (P > 0.05). The FAZRing area in individuals with mild DR was significantly higher than that in control subjects (P < 0.001). However, there is still a small amount of overlap data between the two groups. For the FAZ growth rate, the individuals with mild DR were also significantly larger than the control subjects (P < 0.001). But there were no overlapping data between the two groups.

Conclusions

The growth of FAZ in individuals with mild DR can be inferred by comparing FAZAngi with FAZThic. This method minimizes the impact of individual variations and helps researchers to understand the progression mechanism of DR more deeply.

A variation of foveal morphology in a group of children with hypermetropia

PURPOSE

During routine eye examinations, we noticed widened and flattened foveal pits with loss of normal V-shaped foveal profile and a pseudohole-like appearance in some otherwise healthy hypermetropic children. Our purpose was to describe clinical significance and multimodal imaging features of this incidental finding.

METHODS

Prospectively, 25 eyes of 13 hypermetropic children with these foveal changes and 36 eyes of 19 hypermetropic children with normal foveal appearance were enrolled. The macular thickness measurements and foveal parameters including pit diameter, depth, base, and area obtained by optical coherence tomography (OCT) (Heidelberg Spectralis, Heidelberg Engineering, Heidelberg, Germany), macular superficial and deep vessel density (VD) and foveal avascular zone values obtained by optical coherence tomography angiography (Avanti RTVue‑XR; Optovue, Fremont, CA, USA) were noted. The correlations of these parameters with visual function were evaluated.

RESULTS

In the study group, significantly widened and flattened pit contours with decreased central foveal thickness (p = 0.01), and increased distance between foveal edges (p < 0.001) were observed. While the whole image superficial macular VD was similar between the groups (p = 0.74), a significant decrease in deep macular VD was observed in the study group (p = 0.01). None of these changes were correlated with visual acuity.

CONCLUSION

Wider and flattened foveal pits described here represent a newly defined variation in healthy hypermetropic children. Although a correlation with visual acuity was not evident, these changes in foveal profile are shown to be related with macular microvascular changes in deep capillary plexus. Awareness of these morphologic changes will help clinicians in the differential diagnosis of macular pseudohole.

Ophthalmic characteristics and retinal vasculature changes in Williams syndrome, and its association with systemic diseases

BACKGROUND

We aim to characterise the ophthalmic findings and retinal vasculature changes in patients with WS, and to analyse the correlation between ophthalmic manifestations and the associated systemic diseases.

METHODS

This retrospective case-control study included 27 WS patients and 28 age-matched healthy participants. Stellate pattern of iris, central macular thickness (CMT), foveal width, retinal vessel diameter, superficial vascular density (SVD) of macula and foveal avascular zone (FAZ) were compared between WS patients and healthy participants.

RESULTS

Twenty-five patients (93%) had the classic stellate iris presentation. Compared with healthy controls, WS patients had decreased CMT, increased foveal width and a lower SVD of macula (all P < 0.001). Significantly decreased mean retinal arterial (117.9 ± 9.9 µm vs. 133.0 ± 6.7 µm in WS and controls, respectively; p < 0.001) and venous (158.9 ± 11.2 µm vs. 174.0 ± 8.0 µm in WS and controls, respectively; p < 0.001) outer diameters, as well as mean arterial wall thickness (11.2 ± 1.3 µm vs. 12.2 ± 0.8 µm in WS and controls, respectively; p < 0.01) were found in WS. Stellate iris grading was significantly associated with CMT, foveal width, retinal vessel diameter (all p < 0.05), and a significant increase in the odds of having hypertension (Odds ratio (OR), 5.63; P < 0.05). The severity of stellate iris in WS seemed to have the trend of increasing risk of having pulmonary stenosis, tricuspid regurgitation and mitral regurgitation.

CONCLUSIONS

This study provides the first in vivo evidence reflecting current knowledge on vessel morphology in WS patients that deficient circumferential growth is the predominant pathophysiologic changes resulting from elastin deficiency. The ophthalmic characteristics may serve as a complementary tool to diagnose and follow-up patients suffering from WS.

In Vivo Longitudinal Measurement of Cone Photoreceptor Density in Intermediate Age-Related Macular Degeneration

PURPOSE

To evaluate cone photoreceptor density in clinically unremarkable retinal regions in patients with age-related macular degeneration (AMD) using adaptive optics scanning laser ophthalmoscopy (AOSLO).

DESIGN

Prospective case series with normal comparison group.

METHODS

Ten eyes of 7 patients with intermediate AMD were studied, including 4 with predominantly subretinal drusenoid deposits (SDD) and 3 without SDD. Macular regions with a clinical absence of AMD-associated lesions were identified by cone packing structure on AOSLO and optical coherence tomography. Cone density was measured in 1174 clinically unremarkable regions within the central subfield (CSF), the inner (IR), and outer rings (OR) of the Early Treatment Diabetic Retinopathy Study grid over 39.6 ± 3.3 months and compared with age-matched normal values obtained in 17 participants.

RESULTS

Cone density decreased at 98.3% of the examined locations over time in the eyes with AMD. In the CSF, IR, and OR, cones declined by -255 ± 135, -133 ± 45, and -59 ± 24 cones/degree2/year, respectively, in eyes with SDD, and by -212 ± 89, -83 ± 37, and -27 ± 18 cones/degree2/year, respectively, in eyes without SDD. The percentage of retinal loci with cone density lower than normal (Z score < -2) increased over the follow-up: from 42% at the baseline to 80% at the last visit in eyes with SDD and from 31% to 70% in eyes without SDD.

CONCLUSIONS

AOSLO revealed cone photoreceptor loss in regions that appear otherwise unremarkable clinically. These findings may help explain the loss of mesopic sensitivity reported in these areas in eyes with intermediate AMD.

Sub-cellular level resolution of common genetic variation in the photoreceptor layer identifies continuum between rare disease and common variation

Photoreceptor cells (PRCs) are the light-detecting cells of the retina. Such cells can be non-invasively imaged using optical coherence tomography (OCT) which is used in clinical settings to diagnose and monitor ocular diseases. Here we present the largest genome-wide association study of PRC morphology to date utilising quantitative phenotypes extracted from OCT images within the UK Biobank. We discovered 111 loci associated with the thickness of one or more of the PRC layers, many of which had prior associations to ocular phenotypes and pathologies, and 27 with no prior associations. We further identified 10 genes associated with PRC thickness through gene burden testing using exome data. In both cases there was a significant enrichment for genes involved in rare eye pathologies, in particular retinitis pigmentosa. There was evidence for an interaction effect between common genetic variants, VSX2 involved in eye development and PRPH2 known to be involved in retinal dystrophies. We further identified a number of genetic variants with a differential effect across the macular spatial field. Our results suggest a continuum between common and rare variation which impacts retinal structure, sometimes leading to disease.

Central macular OCTA parameters in glaucoma

BACKGROUND/AIMS

To investigate the relationship between the foveal avascular zone (FAZ) parameters assessed by optical coherence tomography angiography (OCTA) and central visual field parameters in glaucoma and healthy subjects.

METHODS

One hundred and eighty-eight subjects (248 eyes), including 24 healthy (38 eyes), 37 glaucoma suspect (42 eyes, and 127 primary open angle glaucoma (POAG) patients (168 eyes), underwent imaging using OCTA and standard automated perimetry using the 24-2 and 10-2 Swedish Interactive Thresholding Algorithm. OCTA-based and OCT-based FAZ parameters (superficial FAZ area, FAZ circumference), foveal vessel density (FD300) and foveal thickness were measured. The correlation between FAZ parameters and visual field parameters was assessed using linear mixed model.

RESULTS

Axial length adjusted-FAZ area was not different among the three groups (mean (95% CI)): in healthy 0.31 (0.27 to 0.36) mm², glaucoma suspect 0.29 (0.26 to 0.31) mm² and POAG eyes 0.28 (0.27 to 0.30) mm² (p=0.578). FD300 was lower in glaucoma suspect 49.1% (47.9% to 50.4%) and POAG eyes 48.7% (48.1% to 49.4%) than healthy eyes 50.5% (49.3% to 51.7%) though the difference was not statistically significant (p=0.071). Lower FD300 was associated with worse 24-2 and 10-2 visual field mean deviation and foveal threshold in multivariable linear mixed models (all p<0.05). In addition, a smaller FAZ area was associated with lower intraocular pressure (IOP) (p=0.026).

CONCLUSIONS

The FD300, but not the FAZ area was correlated with 10° central visual field mean deviation and foveal threshold in healthy, glaucoma suspect and POAG eyes. In contrast, a smaller FAZ area was associated with lower IOP.

Spatial characterization of the effect of age and sex on macular layer thicknesses and foveal pit morphology

Characterizing the effect of age and sex on macular retinal layer thicknesses and foveal pit morphology is crucial to differentiating between natural and disease-related changes. We applied advanced image analysis techniques to optical coherence tomography (OCT) to: 1) enhance the spatial description of age and sex effects, and 2) create a detailed open database of normative retinal layer thickness maps and foveal pit shapes. The maculae of 444 healthy subjects (age range 21-88) were imaged with OCT. Using computational spatial data analysis, thickness maps were obtained for retinal layers and averaged into 400 (20 x 20) sectors. Additionally, the geometry of the foveal pit was radially analyzed by computing the central foveal thickness, rim height, rim radius, and mean slope. The effect of age and sex on these parameters was analyzed with multiple regression mixed-effects models. We observed that the overall age-related decrease of the total retinal thickness (TRT) (-1.1% per 10 years) was mainly driven by the ganglion cell-inner plexiform layer (GCIPL) (-2.4% per 10 years). Both TRT and GCIPL thinning patterns were homogeneous across the macula when using percentual measurements. Although the male retina was 4.1 μm thicker on average, the greatest differences were mainly present for the inner retinal layers in the inner macular ring (up to 4% higher TRT than in the central macula). There was an age-related decrease in the rim height (1.0% per 10 years) and males had a higher rim height, shorter rim radius, and steeper mean slope. Importantly, the radial analysis revealed that these changes are present and relatively uniform across angular directions. These findings demonstrate the capacity of advanced analysis of OCT images to enhance the description of the macula. This, together with the created dataset, could aid the development of more accurate diagnosis models for macular pathologies.

Structural impact of arrested foveal development in children born extremely preterm without ROP at 6.5 years of age

Objectives

To characterize changes of foveal topography and microstructure of persisting foveal immaturity at 6.5 years of age in children born extremely preterm without retinopathy of prematurity (EPT-NoROP).

Methods

Images from previous optical coherence tomography examinations of 37 EPT-NoROP and 92 control eyes were selected from a regional cohort of the EXPRESS (Extremely Preterm Infants in Sweden) study. Thickness of ganglion cell + inner plexiform layer (GCL+), outer nuclear layer (ONL), retinal thickness (RT) at the foveal centre (FC), foveal depth (FD) and RT at the foveal rim were evaluated.

Results

Layer thickness of GCL+, ONL and RT was increased at FC in the EPT-NoROP group. More than two-thirds had thickness values above the control limit (control mean +2 SD) at FC (GCL + 68%, ONL 76%, and RT 68%), and 50% had reduced FD compared to controls. All parameters showed a high correlation within the EPT-NoROP group, whereas no or weaker correlation was seen in control eyes. The EPT-NoROP sub-groups, divided based on the control limit, did not differ in terms of associated factors such as gestational age, birth weight, visual acuity, and refraction.

Conclusions

Extreme prematurity without impact of ROP is associated with increased GCL + , ONL, and RT thickness at FC as well as reduced FD compared to full-term controls at age 6.5. This indicates that prematurity per se may have a profound effect on foveal anatomical maturation during the first months after birth. Our results suggest RT at FC to be a simple and useful measure of foveal anatomical immaturity.

Optical coherence tomography reveals retinal thinning in schizophrenia spectrum disorders

BACKGROUND

Schizophrenia spectrum disorders (SSDs) are presumed to be associated with retinal thinning. However, evidence is lacking as to whether these retinal alterations reflect a disease-specific process or are rather a consequence of comorbid diseases or concomitant microvascular impairment.

METHODS

The study included 126 eyes of 65 patients with SSDs and 143 eyes of 72 healthy controls. We examined macula and optic disc measures by optical coherence tomography (OCT) and OCT angiography (OCT-A). Additive mixed models were used to assess the impact of SSDs on retinal thickness and perfusion and to explore the association of retinal and clinical disease-related parameters by controlling for several ocular and systemic covariates (age, sex, spherical equivalent, intraocular pressure, body mass index, diabetes, hypertension, smoking status, and OCT signal strength).

RESULTS

OCT revealed significantly lower parafoveal macular, macular ganglion cell-inner plexiform layer (GCIPL), and macular retinal nerve fiber layer (RNFL) thickness and thinner mean and superior peripapillary RNFL in SSDs. In contrast, the applied OCT-A investigations, which included macular and peripapillary perfusion density, macular vessel density, and size of the foveal avascular zone, did not reveal any significant between-group differences. Finally, a longer duration of illness and higher chlorpromazine equivalent doses were associated with lower parafoveal macular and macular RNFL thickness.

CONCLUSIONS

This study strengthens the evidence for disease-related retinal thinning in SSDs.

Foveal Curvature and Its Associations in UK Biobank Participants

Purpose

To examine whether sociodemographic, and ocular factors relate to optical coherence tomography (OCT)-derived foveal curvature (FC) in healthy individuals.

Methods

We developed a deep learning model to quantify OCT-derived FC from 63,939 participants (age range, 39-70 years). Associations of FC with sociodemographic, and ocular factors were obtained using multilevel regression analysis (to allow for right and left eyes) adjusting for age, sex, ethnicity, height (model 1), visual acuity, spherical equivalent, corneal astigmatism, center point retinal thickness (CPRT), intraocular pressure (model 2), deprivation (Townsend index), higher education, annual income, and birth order (model 3). Fovea curvature was modeled as a z-score.

Results

Males had on average steeper FC (0.077; 95% confidence interval [CI] 0.077-0.078) than females (0.068; 95% CI 0.068-0.069). Compared with whites, non-white individuals showed flatter FC, particularly those of black ethnicity. In black males, -0.80 standard deviation (SD) change when compared with whites (95% CI -0.89, -0.71; P 5.2e10-68). In black females, -0.70 SD change when compared with whites (95% CI -0.77, -0.63; p 2.3e10-93). Ocular factors (visual acuity, refractive status, and CPRT) showed a graded inverse association with FC that persisted after adjustment. Macular curvature showed a positive association with FC. Income showed a linear trend increase in males (P for linear trend = 0.005).

Conclusions

We demonstrate marked differences in FC with ethnicity on the largest cohort studied for this purpose to date. Ocular factors showed a graded association with FC. Implementation of FC quantification in research and on the clinical setting can enhance the understanding of clinical macular phenotypes in health and disease.

Visual acuity after cataract surgery in Macular Telangiectasia Type 2 Stage 3 to 5

BACKGROUND

The purpose of this study was to evaluate visual acuity after cataract surgery in eyes with Macular Telangiectasia (MacTel) Type 2.

METHODS

Single-center retrospective cohort study of patients with MacTel Type 2 who underwent cataract surgery and were managed at the same institution. Patients underwent pre-operative assessment by a retinal specialist with examination and optical coherence tomography (OCT) at the same institution. The main outcome measure was the post-operative change in best corrected visual acuity (BCVA). Secondary study outcomes were achieving post-operative BCVA better than Snellen acuity of 20/40 and time to BCVA loss by two lines or more (10 or more ETDRS letters).

RESULTS

A total of 20 eyes (11 patients) underwent cataract surgery and were followed for a median of 25.5 months (IQR 17.5-44.2 months). The median post-operative BCVA improvement was 10.5 letters (IQR 3.50-20.25). Nuclear sclerosis severity [β = 8.99 (95% CI 3.35, 14.6), p = 0.00177] was associated with post-operative change in BCVA and central foveal ellipsoid zone (EZ) breaks [OR 1.33 × 10^-9 (95% CI 5.12 × 10^-10-3.43 × 10^-9), p < 0.001] on OCT was inversely correlated with post-operative BCVA > 20/40 using a multivariate generalized linear model. Central foveal EZ breaks [HR 1.77 × 10⁹ (95% CI 3.86 × 10⁸, 8.11 × 10⁹), p < 0.001] and MacTel Type 2 disease stage [HR 2.83, (95% CI 1.12, 7.12), p = 0.027] were independently associated with shorter time to vision loss of two lines or more in a multivariate Cox regression model.

CONCLUSIONS

Visual acuity significant improved after cataract surgery in eyes with MacTel Type 2 regardless of disease severity. The presence of central foveal EZ breaks may predict poorer post-operative visual acuity and subsequent vision loss from disease progression.

Macular Vessel Density Measurement in Pediatric Renal and Liver Transplant

OBJECTIVES

Microcirculatory dysfunction is known to be associated with organ failure and increased mortality in transplant patients. Noninvasive monitorization of retinal structures of the eye could be a predictor for systemic microvasculature in these patients. Therefore, in this study we aimed to evaluate the retinal microvascular changes in pediatric patients who had undergone liver or renal transplant surgery, using optical coherence tomography angiography.

MATERIALS AND METHODS

The medical records of pediatric patients who had liver or renal transplant in the past 10 years were reviewed. The macular vessel density parameters were obtained by optical coherence tomography angiography (Avanti RTVue XR). The results were compared with the age-matched, sex-matched, and spherical equivalent-matched healthy participants (control group). The IBM SPSS (version 25.0) statistics program was used for data analysis.

RESULTS

We included 32 eyes of 16 liver transplant patients, 20 eyes of 10 renal transplant patients, and 64 eyes of 32 healthy participants (control group). Superficial macular whole image, superficial perifoveal, and deep foveal vessel densities were found to be lower in the liver transplant group compared with the healthy control group (P = .02, P = .01, and P = .01, respectively). Superficial foveal, deep macular whole image, deep foveal, and deep perifoveal vessel densities were found to be lower in the renal transplant group compared with the healthy control group (P = .03, P = .04, P = .01, and P = .02, respectively).

CONCLUSIONS

Macular vessel density measurements are affected in pediatric renal and liver transplant patients. In those patients, retinal optical coherence tomography and optical coherence tomography angiography measurements may provide a noninvasive window to the microcirculation.

Optical Coherence Tomography Anatomic and Temporal Biomarkers in Uveitic Macular Edema

PURPOSE

To assess the relationship between best-corrected visual acuity (BCVA) and optical coherence tomography (OCT) features in noninfectious uveitis (NIU)-related macular edema.

DESIGN

Clinical cohort study from post hoc analysis of 2 phase 3 clinical trials.

METHODS

Correlation and longitudinal treatment analyses were performed. Of 198 patients with NIU, 134 received suprachoroidal CLS-TA (proprietary formulation of a triamcinolone acetonide injectable suspension), and 64 received sham, with 12.9% and 72%, respectively, receiving rescue therapy.

RESULTS

At baseline, mean BCVA progressively worsened with each ordinal drop in central subfield ellipsoid zone (EZ) integrity. Eyes with normal baseline EZ experienced greater 24-week change in BCVA versus those with some degree of baseline EZ disruption (11.9 vs 9.4 letters, P = .006). In contrast, eyes with baseline central subfield cystoid spaces and/or subretinal fluid showed more improvement (13.7 or 17.2 letters, respectively) at 24 weeks, versus those without such findings (5.5 [P = .012] or 9.5 letters [P < .001], respectively). Longitudinal modeling for CLS-TA-treated eyes showed that central subfield thickness (CST) reached 90% of maximal improvement by week 3, whereas 90% maximal response in BCVA was not reached until week 9. CLS-TA-treated eyes that showed CST reduction of ≥50 µm at 4 weeks experienced a greater 24-week improvement in BCVA versus those without such an early response (14.6 vs 6.5 letters, P = .006 for difference).

CONCLUSIONS

Pretreatment EZ integrity and the presence of central subfield cystoid spaces or subretinal fluid each predict improved therapeutic response to treatment in eyes with NIU. In CLS-TA treated eyes, longitudinal modeling shows CST improvement preceding BCVA improvement.

Morphology of foveal hypoplasia: Hyporeflective zones in the Henle fiber layer of eyes with high-grade foveal hypoplasia

Background

Foveal hypoplasia is characterized by the persistance of inner retinal layers at the macular center. We evaluated using spectral-domain optical coherence tomography (SD-OCT) morphological parameters of the macular center of eyes with foveal hypoplasia and describe the presence of hyporeflective zones in the Henle fiber layer (HFL) of eyes with high-grade foveal hypoplasia.

Methods

Eyes with foveal hypoplasia were classified into two groups: high-grade foveal hypoplasia with thick inner retinal layers at the macular center (thickness above 100 μm; 16 eyes of 9 subjects) and low-grade foveal hypoplasia with thinner inner retinal layers at the macular center (thickness below 100 μm; 25 eyes of 13 subjects). As comparison, SD-OCT images of normal control eyes (n = 75) were investigated.

Results

Eyes with foveal hypoplasia displayed shorter central photoreceptor outer segments (POS), a thinner central myoid zone, and a thicker central HFL compared to control eyes. Eyes with high-grade foveal hypoplasia also displayed a thinner central outer nuclear layer (ONL) compared to eyes with low-grade foveal hypoplasia and control eyes. There was a negative correlation between the thicknesses of the central ONL and HFL in eyes with foveal hypoplasia; however, the total thickness of both ONL and HFL was similar in all eye populations investigated. Visual acuity of subjects with foveal hypoplasia was negatively correlated to the thickness of the central inner retinal layers and positively correlated to the length of central POS. In contrast to central POS, the length of paracentral POS (0.5 and 1.0 mm nasal from the macular center) was not different between the three eye populations investigated. The paracentral ONL was thickest in eyes with high-grade foveal hypoplasia and thinnest in control eyes. Hyporeflective zones in the HFL were observed on SD-OCT images of eyes with high-grade foveal hypoplasia, but not of eyes with low-grade foveal hypoplasia and control eyes. OCT angiography images recorded at the level of the HFL of eyes with high-grade foveal hypoplasia showed concentric rings of different reflectivity around the macular center; such rings were not observed on images of eyes with low-grade foveal hypoplasia and control eyes.

Conclusions

It is suggested that the hyporeflective zones in the HFL of eyes with high-grade foveal hypoplasia represent cystoid spaces which are surrounded by Henle fiber bundles. Cystoid spaces are likely formed because there are fewer Henle fibers and a thinner central ONL despite an unchanged thickness of both ONL and HFL. Cystoid spaces may cause the concentric rings of different reflectivity around the macular center in the HFL of eyes with high-grade foveal hypoplasia.

Foveal morphology of normal fellow eyes of patients with unilateral macular hole

PURPOSE

To determine the morphology of the fovea in the ophthalmoscopically and tomographically normal fellow eyes of patients with unilateral idiopathic macular hole (MH) and to determine the association between the foveal morphological parameters and the foveal outer nuclear layer (ONL) thickness.

DESIGN

Retrospective observational study.

PARTICIPANTS

Two hundred three normal fellow eyes of patients with unilateral MH and 216 normal eyes of 216 healthy subjects.

METHODS

All eyes were examined by swept source optical coherence tomography (OCT). The built-in software measured the average retinal and choroidal thickness in the center and in the inner four subfields defined in the Early Treatment Diabetic Retinopathy Study. The total retinal thickness and the three retinal layers at the fovea and parafovea (0.25- and 0.5-mm nasal and temporal from fovea) and foveal floor width (FFW) were measured in the image of a horizontal scan passing through the center of the fovea. We defined the thickness between the internal limiting membrane and outer plexiform layer as the inner retinal thickness, and the thickness between the external limiting membrane and retinal pigment epithelium as the outer retinal thickness. Multiple regression analyses were performed with the age, sex, axial length, and the presence of a posterior vitreous detachment as the dependent variables.

MAIN OUTCOME MEASURES

OCT measurements and correlations between the foveal parameters and foveal ONL thickness.

RESULTS

The fellow eyes had a thinner central retinal subfield, thinner fovea, thinner ONL at all points except 0.5 mm nasal, significantly thicker outer retina at all points, and a wider FFW (P=.040 to P<.0001). The foveal ONL thickness was significantly and positively correlated with the central subfield retinal thickness and foveal thickness and negatively with the FFW (all P< .0001).

CONCLUSIONS

The thinner and deeper fovea and the thinner ONL of the fellow eyes of patients with a unilateral MH makes these eyes more susceptible to forming MH.

Assessing Foveal Structure in Individuals with TYR R402Q and S192Y Hypomorphic Alleles

Purpose

Design

Participants

Methods

Main Outcome Measures

Results

Conclusions

Analysis of Microvasculature in Nonhuman Primate Macula With Acute Elevated Intraocular Pressure Using Optical Coherence Tomography Angiography

Purpose

To investigate responses of macular capillary vessel area density (VAD) of superficial and deep retinal vascular plexuses to elevations in intraocular pressure (IOP) in cynomolgus macaque monkeys using optical coherence tomography angiography (OCTA).

Methods

In five general anesthetized male cynomolgus monkeys, the IOP was increased incrementally by 10 mmHg from baseline (10 mmHg) to 70 mmHg and then decreased back to 10 mmHg (recovery state). Structural OCT (30° × 30°) and OCTA (20° × 15°) centered on the macula were obtained at each IOP and 3, 15, and 30 minutes after recovery. En face images of the superficial vascular complex (SVC) and deep vascular complex (DVC) were extracted, and VAD (%) compared with that at baseline was calculated.

Results

The VADs in the SVC and DVC at baseline and at 30 mmHg IOP were 34.96%, 34.15%, 35.38%, and 30.12%, respectively. The VAD plateaued until 30 mmHg; however, the VAD was affected more in the DVC than in the SVC (P = 0.008) at 30 mmHg. It showed a significant reduction at 40 mmHg (16.52% SVC, P = 0.006; 18.59% DVC, P = 0.012). In the recovery state, the SVC showed full retention of baseline VAD, but the DVC maintained VAD approximately 70% of that at baseline. Structural OCT showed hyperreflectivity in the nuclear layer, retinal swelling, and an undifferentiated ellipsoid zone from 50 mmHg.

Conclusions

Despite physiological autoregulation, perifoveal microcirculation was affected at high IOP ≥ 40 mmHg, especially in the DVC, which explains the pathological mechanism of macular vulnerability in ischemic diseases.

Measuring the foveal avascular zone in diabetes: A study using optical coherence tomography angiography

Aims/Introduction

Diabetes is a global issue that currently affects 425 million people worldwide. One observable microvascular complication of this condition is a change in the foveal avascular zone (FAZ). In this study, we used optical coherence tomography angiography to investigate the effect of diabetes on the FAZ.

Materials and Methods

A total of 11 participants with diabetes and 11 participants without diabetes took part in this study. Participants in both groups were matched for age (P = 0.217) and sex (P = 0.338), and had no history of ocular disease. Macular optical coherence tomography angiography (OCT‐A) scans of participants’ right and left eyes were taken. Glycosylated hemoglobin (HbA_1c) and blood glucose levels were also measured. The FAZ area was manually segmented at the levels of the superficial capillary plexus (FAZ_SCP) and deep capillary plexus (FAZ_DCP).

Results

There was a strong relationship between the FAZ area of participants’ right and left eyes (P ≤ 0.001) in both diabetes and non‐diabetes groups. In the diabetes group, the FAZ_SCP (P = 0.047) and FAZ_DCP (P = 0.011) areas was significantly larger than in the non‐diabetes group. Moreover, multiple linear regression analysis predicted a 0.07‐mm² increase in the FAZ_SCP and FAZ_DCP areas of individuals with diabetes for every 1% increase in their HbA_1c level.

Conclusions

Our findings show that there is enlargement of the FAZ in individuals with diabetes compared with individuals without diabetes. In the diabetes group, this enlargement appears to be correlated with HbA_1c level. OCT‐A imaging could, therefore, be a useful tool to monitor the FAZ and identify potential early microvasculopathy in diabetes.

The effect of treatment on retinal microvasculature in children with unilateral amblyopia

PURPOSE

To assess whether the abnormal retinal microvasculature in unilateral amblyopia changes following amblyopia treatment.

METHODS

A total of 70 patients with unilateral amblyopia (4-12 years of age) were initially recruited. Of these, 33 completed follow-up assessments after 6 months of amblyopia treatment. The retinal thickness and microvascular metrics were measured at baseline and after treatment. The interocular differences and longitudinal changes after treatment were analyzed. Partial correlation analysis was performed to explore the associations between best-corrected visual acuity improvements and changes in retinal metrics after treatment.

RESULTS

The central retinal thickness, thickness of the ganglion cell-inner plexiform layer, and vessel density index were greater in amblyopic eyes (P < 0.001, P < 0.001, P < 0.001, resp.), whereas the area and circularity of the foveal avascular zone were smaller in amblyopic eyes (P = 0.014, P < 0.001, resp.). Better (lower logMAR) visual acuity was associated with greater circularity of the foveal avascular zone in amblyopic eyes (r = -0.326; P = 0.007). The circularity significantly increased after amblyopia treatment in both eyes (P < 0.001, P = 0.027), and the changes in circularity in amblyopic eyes were associated with visual acuity improvements (r = -0.476; P = 0.008).

CONCLUSIONS

Patients with unilateral amblyopia showed interocular differences in retinal microstructure. Foveal avascular zone shape was more irregular in amblyopic eyes and associated with the severity of amblyopia, which tended to improve and become more regular with visual acuity improvements after amblyopia treatment.

ALTERATION OF OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY IN A PATIENT WITH OCULAR ISCHEMIC SYNDROME

PURPOSE

To analyze optical coherence tomography angiography images in ocular ischemic syndrome (OIS) before and after carotid artery stenting.

METHODS

We report the case of an 80-year-old man with a history of hypertension and diabetes mellitus who developed OIS in the right eye due to right internal carotid artery stenosis 2 years earlier. After visual acuity declined in the left eye 2 years later, a neurosurgeon discovered left internal carotid artery stenosis, which led to the diagnosis of OIS in the left eye as well. After carotid artery stenting, improvements were observed in both visual acuity and blood flow as assessed by laser speckle flowgraphy. The area of the foveal avascular zone and density of the retinal vessel at the level of the superficial and deep retinal layers were analyzed using optical coherence tomography angiography before and after treatment.

RESULTS

Mean superficial foveal avascular zone area was 0.29 mm2 before treatment, decreasing by 29.97% to 0.20 mm2 after treatment. Mean deep foveal avascular zone area was 1.72 mm2 before treatment, decreasing by 20.35% to 1.37 mm2 after treatment. Superficial or deep vessel density increased by 33.4% and 34.3% after treatment, respectively.

CONCLUSION

Optical coherence tomography angiography confirmed foveal avascular zone area reduction and increased vessel density in all retinal layers after carotid artery stenting for OIS. These findings suggest that optical coherence tomography angiography may be useful for evaluating blood flow and treatment efficacy in OIS.

Spatial positional relationship between macular superficial vessel density and ganglion cell-inner plexiform layer thickness in primary angle closure glaucoma

Purpose

To evaluate the spatial relationship between macular superficial vessel density (SVD) and macular ganglion cell-inner plexiform layer (GCIPL) thickness in primary angle closure glaucoma (PACG), and to investigate diagnostic abilities of macular SVD and foveal avascular zone (FAZ) parameters.

Methods

This was a cross-sectional study on 38 PACG patients (38 eyes) and 25 healthy subjects (25 eyes). Macular region was imaged using a 1050-nm-wavelength swept-source optical coherence tomography (OCT) angiography (OCTA) system (DRI OCT Triton, TOPCON). Vessel density of the macular region was quantified by ImageJ software. The peripapillary retinal nerve fiber layer (pRNFL) thicknesses and macular GCIPL thickness were obtained by swept-source OCT. Pearson correlation analysis was used to evaluate the spatial positional relationship between macular SVD and macular GCIPL thickness. At the same time, the correlation between macular SVD and pRNFL thickness was evaluated. Areas under the receiver operating characteristics curves (AUCs) of OCT, OCTA and FAZ measurement metrics were calculated to assess the diagnostic ability for glaucoma.

Results

Macular GCIPL thickness had a moderate correlation with the macular SVD in the inferonasal sector (r = 0.426, P = 0.008). In addition, there was a strong correlation between inferonasal sector of macular vessel density and 5,6,7,8 clock-hour regions of the pRNFL thicknesses (all r > 0.5). Inferoinferior sector of macular SVD and 6,7 clock-hour regions of pRNFL thicknesses also had strong correlation (all r > 0.5). The AUCs of macular SVD ranged between 0.61 (superonasal sector) and 0.76 (inferoinferior sector). The FAZ circularity index showed the highest diagnostic power (AUC = 0.94;95% CI, 0.85–0.99), followed by superotemporal sector of macular GCIPL thicknesses (0.93;95% CI,0.83–0.98).

Conclusions

Sector of macular SVD not only had a spatial positional correlation with corresponding macular GCIPL thickness, but also with clock-hour regional pRNFL thicknesses in PACG eyes. FAZ circulation index might be a useful diagnostic parameter.

Determinants of vitreomacular traction width: associations with foveal floor width and vitreoretinal interface changes

To investigate the relationship between vitreomacular traction (VMT) width, foveal floor width (FFW) and other anatomical characteristics between eyes of patients with VMT. Retrospective observational study of unilateral and bilateral VMT cases from two specialist ophthalmic centres in the United Kingdom (UK) between 2016 and 2018. For unilateral VMT cases: VMT width in the affected eye and FFW in the non-affected fellow eye were measured. In bilateral VMT cases: VMT width in both eyes was measured. In all cases, the presence of any associated inner or outer retinal, and vitreoretinal interface (VRI) changes, including epiretinal membrane, was also documented. 88 patients fulfilled the study criteria: 57 having unilateral and 31 bilateral VMT. For unilateral VMT cases, log (VMT) width was significantly correlated with FFW (r = 0.347, p = 0.008). Using stepwise linear regression, FFW (p = 0.004) and VRI changes (p = 0.03) were both significantly associated with VMT width with a R² of 0.21. In bilateral VMT cases, there was strong positive correlation between log (VMT) width (r = 0.88, p < 0.001), and the presence of any VRI (r = 0.90, p < 0.001) or outer retinal changes (r = 0.50, p < 0.001) between the two eyes. These findings suggest that individual variations in foveal morphology as measured by the FFW, along with the presence of vitreoretinal interface changes, are associated with the extent of VMT width. VMT width, VRI and outer retinal changes were also highly correlated between eyes in bilateral VMT, suggesting that individual patient factors, which may be genetic or acquired, determine their presence and extent.

Quantitative analysis of retinal and choroidal vasculature in patients with chorioretinal folds secondary to hyperopia

INTRODUCTION

There is a lack of information on quantitative parameters of optical coherence tomography angiography (OCTA) in cases of chorioretinal folds (CRF). The aim of this study was to compare OCTA retinal and choriocapillary vessel density (VD) between normal subjects and patients with CRF.

METHODS

We conducted an observational retrospective study. A total of 16 eyes of eight patients were recruited (eight eyes with CRF and eight control eyes). Data on best-corrected visual acuity (BCVA), refractive error, central macular thickness (CMT), central subfoveal thickness (CST), and OCTA findings (VD and foveal avascular zone (FAZ) area in superficial capillary plexus (SCP), middle capillary plexus (MCP), and deep capillary plexus (DCP), and VD in choriocapillaris (CC)) were recorded in each eye.

RESULTS

Compared with control group, CRF group showed decreased VD in the foveal region of SCP and MCP (p value 0.003 and 0.001), and increased VD in nasal region of SCP and MCP (p value 0.02 and 0.001), and in parafoveal area of MCP (p value 0.005). No differences were found in DCP and CC layers. Furthermore, we observed an enlargement of FAZ in CRF group at SCP and MCP slabs (p value <0.001 and 0.015). Respect to optical coherence tomography parameters, we demonstrated a thicker choroid in the CRF group (p value 0.002).

CONCLUSION

To the best of our knowledge, this is the first study reported in the literature quantifying VD of retinal capillary plexus and CC in a group of patients with a diagnosis of CRF secondary to hyperopia.

The Impact of Chronic Heart Failure on Retinal Vessel Density Assessed by Optical Coherence Tomography Angiography in Children with Dilated Cardiomyopathy

(1) Introduction: The aim of this study is to assess retinal vessel density (VD) in the superficial capillary plexus layer (SP) and deep capillary plexus layer (DP) in children with chronic heart failure (CHF) in the course of dilated cardiomyopathy (DCM) using optical coherence tomography angiography (OCTA). (2) Methods: Thirty children with CHF due to DCM lasting more than six months, with an enlarged left ventricle and impaired left ventricular systolic function (left ventricular ejection fraction (LVEF) ≤ 55%), were enrolled to have both their eyes assessed for this study. Mean age of the children was 9.9 ± 3.57 years. The control group consisted of an additional 30 children without CHF (mean age 11.27 ± 3.33 years) matched for age and gender against the study group. All participants underwent transthoracic echocardiography to measure LVEF using Simpson method. Blood serum was tested for N-terminal-pro-brain natriuretic peptide (NT-proBNP) marker value. All children underwent OCTA with evaluation of the foveal avascular zone (FAZ), whole superficial vessel density (wsVD), foveal superficial vessel density (fsVD), parafoveal superficial vessel density (psVD), whole deep vessel density (wdVD), foveal deep vessel density (fdVD), parafoveal deep vessel density (pdVD), whole thickness (WT), foveal thickness (FT), and parafoveal thickness (PFT). (3) Results: Retinal VD in SP was significantly lower in children with CHF as compared to the controls. The following SP parameters in the study group were statistically significantly lower than these same measurements for the control group. Details, with study group findings quantified first, include wsVD (46.2% vs. 49.83%, p < 0.05), fsVD (18.07% vs. 24.15%, p < 0.05), and psVD (49.24% vs. 52.51%, p < 0.05). The WT (311.03 micrometers (μm) vs. 323.55 μm, p < 0.05), FT (244.57 μm vs. 256.98 μm, p < 0.05), and PFT (320.63 μm vs. 332.02 μm, p < 0.05). No significant differences in DP retinal VD were found between the two groups. No statistically significant differences in the FAZ were found. The fsVD and FT were correlated with biometry and the age of the study participants. There was a correlation between FAZ and FT (p < 0.001). There were no correlations between retinal VD in both plexuses and refractive error, sex, NT-proBNP, and LVEF. (4) Conclusions: In children with CHF in the course of DCM as compared to the control group, significantly decreased retinal VD in SP was observed. The results of our study indicate that measurements of the OCTA may be a useful diagnostic method in children with chronic heart failure, but it is necessary to conduct further studies in larger groups of participants and long-term observation of these patients.

Müller cells and astrocytes in tractional macular disorders

Tractional deformations of the fovea mainly arise from an anomalous posterior vitreous detachment and contraction of epiretinal membranes, and also occur in eyes with cystoid macular edema or high myopia. Traction to the fovea may cause partial- and full-thickness macular defects. Partial-thickness defects are foveal pseudocysts, macular pseudoholes, and tractional, degenerative, and outer lamellar holes. The morphology of the foveal defects can be partly explained by the shape of Müller cells and the location of tissue layer interfaces of low mechanical stability. Because Müller cells and astrocytes provide the structural scaffold of the fovea, they are active players in mediating tractional alterations of the fovea, in protecting the fovea from such alterations, and in the regeneration of the foveal structure. Tractional and degenerative lamellar holes are characterized by a disruption of the Müller cell cone in the foveola. After detachment or disruption of the cone, Müller cells of the foveal walls support the structural stability of the foveal center. After tractional elevation of the inner layers of the foveal walls, possibly resulting in foveoschisis, Müller cells transmit tractional forces from the inner to the outer retina leading to central photoreceptor layer defects and a detachment of the neuroretina from the retinal pigment epithelium. This mechanism plays a role in the widening of outer lameller and full-thickness macular holes, and contributes to visual impairment in eyes with macular disorders caused by conractile epiretinal membranes. Müller cells of the foveal walls may seal holes in the outer fovea and mediate the regeneration of the fovea after closure of full-thickness holes. The latter is mediated by the formation of temporary glial scars whereas persistent glial scars impede regular foveal regeneration. Further research is required to improve our understanding of the roles of glial cells in the pathogenesis and healing of tractional macular disorders.

What Is Left After Resolution of Neonatal Retinal Hemorrhage: The Longitudinal Long-term Outcome in Foveal Structure and Visual Function

PURPOSE

Neonatal retinal hemorrhage (NRH) is one of the most common neonatal fundus conditions. Hemorrhage resolves spontaneously; however, its long-term outcome is unknown yet. The current study explores the long-term role of NRH in foveal structure and visual function.

DESIGN

Cohort study (a prospective longitudinal study, in which the participants were followed up for 4-6 years).

METHODS

A total of 125 healthy newborns during 2013-2015, including 50 newborns with NRH and 75 newborns without NRH, were enrolled. The eyes with NRH were further categorized into the foveal hemorrhage (FH) group and non-FH group. A comprehensive ophthalmic examination including best-corrected visual acuity (BCVA) measurement, slit-lamp examination, refractive error measurement, scanning laser ophthalmoscopy, and spectral-domain OCT was performed. Total retinal thickness (TRT) and the inner and outer retinal layers in the fovea were measured and compared.

RESULTS

The NRH was absorbed within 2.1 ± 0.98 weeks (median: 3 weeks). No difference was noted in the demographic characteristics between the groups; there was no significant difference in the logMAR BCVA (P = .83) or in the TRT. Subgroup analysis showed that TRT at the fovea in the FH group was significantly thicker (P = .005). Segmentation analysis showed a significantly thicker foveal outer nuclear layer (ONL) in the FH group (P = .017).

CONCLUSIONS

Birth-related retinal hemorrhage, even FH, might not lead to obvious visual abnormalities at the age of 4 years, at least according to this study with relatively small sample size. However, a thicker fovea, mainly attributed to a wider ONL and a shallower foveal pit, is noted in our study.

Foveal Pit Morphology Characterization: A Quantitative Analysis of the Key Methodological Steps

Disentangling the cellular anatomy that gives rise to human visual perception is one of the main challenges of ophthalmology. Of particular interest is the foveal pit, a concave depression located at the center of the retina that captures light from the gaze center. In recent years, there has been a growing interest in studying the morphology of the foveal pit by extracting geometrical features from optical coherence tomography (OCT) images. Despite this, research has devoted little attention to comparing existing approaches for two key methodological steps: the location of the foveal center and the mathematical modelling of the foveal pit. Building upon a dataset of 185 healthy subjects imaged twice, in the present paper the image alignment accuracy of four different foveal center location methods is studied in the first place. Secondly, state-of-the-art foveal pit mathematical models are compared in terms of fitting error, repeatability, and bias. The results indicate the importance of using a robust foveal center location method to align images. Moreover, we show that foveal pit models can improve the agreement between different acquisition protocols. Nevertheless, they can also introduce important biases in the parameter estimates that should be considered.

Microvascular and functional changes according to the fundus location of the affected arteriovenous crossing in patients with branch retinal vein occlusion

Purpose:

The aim of this study was to evaluate the structural and functional changes occurring in patients with branch retinal vein occlusion (BRVO) according to the distance of the affected arteriovenous (AV) crossing to the centers of the fovea and optic disc by optic coherence tomography angiography (OCTA).

Methods:

Forty-five patients with unilateral BRVO and 45 age- and sex-matched healthy controls were included in this retrospective observational study. Images of the macula (3 mm × 3 mm) and affected AV crossing sites were obtained by OCTA. The fovea-AV crossing distance (FAVD), optic disc-AV crossing distance (DAVD), and optic disc-fovea distance (DFD) were measured.

Results:

The FAVD/DFD ratio was positively correlated with the vessel density in the superficial and deep affected hemifields (r = 0.430, P < 0.05 and r = 0.308, P < 0.05, respectively) and negatively correlated with the superficial foveal avascular zone and logarithm of the minimum angle of resolution (logMAR) visual acuity (r = –0.412, P < 0.05 and r = –0.356, P < 0.05, respectively). The DAVD/DFD ratio was not correlated with the logMAR visual acuity, superficial FAZ area or vessel densities in the affected hemifield (all P > 0.05).

Conclusion:

The affected AV crossing site that was further away from the fovea had better visual acuity and quantitative microvascular parameters in the affected hemifields. However, this correlation was not observed for the distance between the affected AV crossing site and the optic disc.

Assessing Interocular Symmetry of the Foveal Cone Mosaic

Purpose

To test the hypothesis that foveal cone topography is symmetrical between contralateral eyes.

Methods

We used adaptive optics scanning light ophthalmoscopy to acquire images of the foveal cone mosaic in each eye of 58 subjects with normal vision (35 female, 23 male). Cones were semiautomatically identified over a 300 × 300-µm foveal area. From these cone coordinates, maps of cone density were derived, and we extracted estimates of peak cone density from each map. Mosaic regularity was assessed using Voronoi cell area regularity (VCAR). Average roundness and average area of the 70%, 75%, 80%, 85%, and 90% of peak density isodensity contours were evaluated.

Results

The average peak cone density for right eyes was 180,286 cones/mm² (n = 49) and for left eyes was 182,397 cones/mm² (n = 45), with a mean absolute difference of 6363 cones/mm² (n = 43). Peak density, cone spacing, VCAR, and average area within the isodensity contours of fellow eyes were not significantly different (P = 0.60, P = 0.83, P = 0.30, and P = 0.39, respectively). However, the average roundness of the isodensity contours was 2% more circular in the right eyes than in the left eyes (P = 0.02).

Conclusions

There is interocular symmetry of peak foveal cone density, mosaic regularity, and area encompassing the most densely packed cells in subjects with normal vision. The origin and significance of the observed interocular difference in average roundness of the isodensity contours are unclear.

Genetic variation affects morphological retinal phenotypes extracted from UK Biobank optical coherence tomography images

Optical Coherence Tomography (OCT) enables non-invasive imaging of the retina and is used to diagnose and manage ophthalmic diseases including glaucoma. We present the first large-scale genome-wide association study of inner retinal morphology using phenotypes derived from OCT images of 31,434 UK Biobank participants. We identify 46 loci associated with thickness of the retinal nerve fibre layer or ganglion cell inner plexiform layer. Only one of these loci has been associated with glaucoma, and despite its clear role as a biomarker for the disease, Mendelian randomisation does not support inner retinal thickness being on the same genetic causal pathway as glaucoma. We extracted overall retinal thickness at the fovea, representative of foveal hypoplasia, with which three of the 46 SNPs were associated. We additionally associate these three loci with visual acuity. In contrast to the Mendelian causes of severe foveal hypoplasia, our results suggest a spectrum of foveal hypoplasia, in part genetically determined, with consequences on visual function.

FOVEAL AVASCULAR ZONE VOLUME: A New Index Based on Optical Coherence Tomography Angiography Images

PURPOSE

To propose a new clinical evaluation index, foveal avascular zone (FAZ) volume, and analyze its statistical significance.

METHODS

A semiautomatic method is proposed to measure the FAZ volume in optical coherence tomography angiography images as follows: The region of interest was flattened and annotated axially. The labeled pixels in the restored region of interest were counted as the FAZ volume. Linear regression and the independent samples t-test were performed for the statistical analysis.

RESULTS

Sixty-one normal, 64 high myopia, and 42 diabetic retinopathy eyes were imaged using optical coherence tomography angiography. For normal eyes, the FAZ volume correlates inversely with central macular thickness (superficial: P = 0.004; deep: P < 0.001) and positively with area (P < 0.001). For high myopia eyes, the deep plexus FAZ (P = 0.34) and total FAZ (P = 0.38) volumes show no significant difference, whereas the superficial plexus FAZ volume is significantly larger than control (P < 0.001). For diabetic retinopathy eyes, the superficial plexus FAZ (P = 0.001), deep plexus FAZ (P = 0.014), and total volumes (P = 0.002) are significantly larger than control.

CONCLUSION

The FAZ volume is proposed for depicting the 3D structure of the FAZ. It shows greater sensitivity for vascular alteration that makes it meaningful for clinical analysis.

Reduced Superficial Capillary Density in Cerebral Infarction Is Inversely Correlated With the NIHSS Score

Purpose: The retina and the brain share similar neuronal and microvascular features, therein we aimed to assess the structural and microvascular changes in the macula and choriocapillaris (CC) in patients with cerebral infarction when compared with healthy controls using optical coherence tomography angiography (OCTA).

Methods: OCTA was used to image and measure the capillary density in the radial peripapillary capillaries (RPC), superficial capillary plexus (SCP), deep capillary plexus (DCP), choriocapillaris (CC), and mean area of the foveal avascular zone (FAZ) in all participants. Twenty-two cerebral infarction patients based on their magnetic resonance imaging (MRI) and 25 healthy controls were included in our study.

Results: Density of the RPC (P < 0.001), SCP (P = 0.001), DCP (P < 0.001) and CC (P < 0.001) were significantly reduced in cerebral infarction patients when compared with healthy controls, respectively. Retinal thickness measurements (P < 0.05) were significantly reduced in cerebral infarction patients when compared with healthy controls. The mean FAZ area was significantly larger (P = 0.012) in cerebral infarction patients when compared with healthy controls. National Institute of HealthStroke Scale (NIHSS) inversely correlated with SCP density in cerebral infarction patients (Rho = −0.409, P = 0.001). Receiver operating characteristics curve analysis showed that the blood flow of the choriocapillaris had the highest index [area under the receiver operatingcharacteristic (AUROC) = 0.964] to discriminate cerebral infarction patients from the healthy controls.

Conclusions: Our study suggests that cerebral microcirculation dysfunction which occurs in cerebral infarction is mirrored in the macula and choroidal microcirculation. OCTA has the potential to non-invasively characterize the macula and choroidal changes in cerebral infarction in vivo.

Early Detection of Microvascular Impairments With Optical Coherence Tomography Angiography in Diabetic Patients Without Clinical Retinopathy: A Meta-analysis

PURPOSE

To evaluate microvascular impairments with optical coherence tomography angiography (OCTA) in the eyes of diabetic patients with no diabetic retinopathy (NDR).

DESIGN

Systematic review and meta-analysis.

METHODS

The PubMed and Embase databases were comprehensively searched to identify studies comparing the microvascular changes between diabetic eyes without clinical retinopathy and healthy controls using OCTA. Data of interest were extracted and analyzed by Review Manager V.5.3 and Stata V.14.0. The weighted mean differences and their 95% confidence intervals were used to assess the strength of the association.

RESULTS

Forty-five cross-sectional studies involving 2241 diabetic and 1861 healthy eyes were ultimately included. OCTA unambiguously revealed that compared with the healthy control group, the NDR group manifested enlarged areas and increased perimeters of the foveal avascular zone, with decreased perfusion density (PD) in both superficial and deep capillary plexus of the macula (except parafoveal PD of the inner retina and foveal PD) and reduced radial peripapillary capillary PD. In addition, subgroup analyses according to the type of diabetes mellitus indicated that most of those differences became nonsignificant (except parafoveal PD in the deep capillary plexus) in type 1 diabetes mellitus, while in type 2 diabetes mellitus they remained statistically significant.

CONCLUSION

Our results suggested that retinal microvascular impairments might have occurred antecedent to clinically visible diabetic retinopathy and could be detected early by OCTA. However, those manifestations could be inconsistent according to the types of diabetes mellitus.

Preservation of the Foveal Avascular Zone in Achromatopsia Despite the Absence of a Fully Formed Pit

Purpose

To examine the foveal avascular zone (FAZ) in patients with congenital achromatopsia (ACHM).

Methods

Forty-two patients with genetically confirmed ACHM were imaged either with Optovue's AngioVue system or Zeiss's Plex Elite 9000, and the presence or absence of a FAZ was determined. For images where a FAZ was present and could be confidently segmented, FAZ area, circularity index, and roundness were measured and compared with previously published normative values. Structural optical coherence tomography images were acquired to assess the degree of foveal hypoplasia (number and thickness of inner retinal layers present at the fovea).

Results

A FAZ was present in 31 of 42 patients imaged (74%), although no determination could be made for 11 patients due to poor image quality (26%). The mean ± SD FAZ area for the ACHM retina was 0.281 ± 0.112 mm², which was not significantly different from the previously published normative values (P = 0.94). However, their FAZs had decreased circularity (P < 0.0001) and decreased roundness (P < 0.0001) compared to the normative cohort. In the patients with ACHM examined here, the FAZ area decreased as the number and thickness of the retained inner retinal layers increased.

Conclusions

Our data demonstrate that despite the presence of foveal hypoplasia, patients with ACHM can have a FAZ. This is distinct from other conditions associated with foveal hypoplasia, which generally show an absence of the FAZ. In ACHM, FAZ formation does not appear to be sufficient for complete pit formation, contrary to some models of foveal development.

The Influence of Axial Length Upon the Retinal Ganglion Cell Layer of the Human Eye

Purpose

Variation in retinal thickness with eye size complicates efforts to estimate retinal ganglion cell number from optical coherence tomography (OCT) measures. We examined the relationship among axial length, the thickness and volume of the ganglion cell layer (GCL), and the size of the optic chiasm.

Methods

We used OCT to measure GCL thickness over 50 degrees of the horizontal meridian in 50 healthy participants with a wide range of axial lengths. Using a model eye informed by individual biometry, we converted GCL thickness to tissue volume per square degree. We also measured the volume of the optic chiasm for 40 participants using magnetic resonance imaging (MRI).

Results

There is a positive relationship between GCL tissue volume and axial length. Given prior psychophysical results, we conclude that increased axial length is associated with increased retinal ganglion cell size, decreased cell packing, or both. We characterize how retinal ganglion cell tissue varies systematically in volume and spatial distribution as a function of axial length. This model allows us to remove the effect of axial length from individual difference measures of GCL volume. We find that variation in this adjusted GCL volume correlates well with the size of the optic chiasm.

Conclusions

Our results provide the volume of ganglion cell tissue in the retina, adjusted for the presumed effects of axial length upon ganglion cell size and/or packing. The resulting volume measure accounts for individual differences in the size of the optic chiasm, supporting its use to characterize the post-retinal visual pathway.

Translational Relevance

Variations in ametropia can confound clinical measures of retinal features. We present a framework within which the thickness and volume of retinal structures can be measured and corrected for the effects of axial length.