Ultrahigh resolution optical coherence tomography in macular dystrophy

Histology and Clinical Lifecycle of Acquired Vitelliform Lesion, a Pathway to Advanced Age-Related Macular Degeneration

PURPOSE

To evaluate hypotheses about the role of acquired vitelliform lesion (AVL) in age-related macular degeneration pathophysiology.

DESIGN

Laboratory histology study; retrospective, observational case series.

METHODS

Two donor eyes in a research archive with AVL and age-related macular degeneration were analyzed with light and electron microscopy for AVL content at locations matched to ex vivo B-scans. A retrospective, observational clinical cohort study of 42 eyes of 30 patients at 2 referral clinics determined the frequency of optical coherence tomography features stratified by AVL fate.

RESULTS

Histologic and clinical cases showed subretinal drusenoid deposit and drusen. Ultrastructural AVL components in 2 donor eyes included retinal pigment epithelium (RPE) organelles (3%-22% of volume), outer segments (2%-10%), lipid droplets (0.2%-12%), and a flocculent material (57%-59%). Of 48 AVLs (mean follow-up 46 ± 39 months), 50% collapsed to complete RPE and outer retinal atrophy, 38% were stable, 10% resorbed, and 2% developed neovascularization. The Early Treatment Diabetic Retinopathy Study grid central subfield contained 77% of AVLs. Hyperreflective foci, ellipsoid zone disruption, and hyperreflective thickening of the RPE-basal lamina-Bruch membrane band were common at maximum AVL expansion. Collapsing and noncollapsing AVLs had different growth rates (rapid vs slow, respectively).

CONCLUSIONS

AVL deposits contain unexpectedly low levels of RPE organelles and outer segments. Subfoveal predilection, reflectivity on optical coherence tomography, hyperautofluorescence, yellow color, and growth-regression phases suggest dysregulation of lipid transfer pathways specific to cone photoreceptors and supporting cells in formation of AVL deposit, analogous to drusen and subretinal drusenoid deposit. Prediction of AVL outcomes via growth rates should be confirmed in larger clinical studies.

Retinal and circumpapillary nerve fiber layer thickness and associated factors in children

OBJECTIVE

To evaluate the distribution of macula and circumpapillary retina nerve fiber layer (cpRNFL) thickness and other associated factors among grade-1 primary school children in Lhasa using spectral-domain optical coherence tomography (SD-OCT).

METHODOLOGY

OCT assessment was conducted on 1856 grade-1 students from 7 primary schools in Lhasa, Tibet following a successful random stratified sampling of the students. Each child underwent comprehensive general and ocular examinations as well as an SD-OCT detection (12 × 9 mm, 3D wide scan mode, Topcon 3D OCT-1) to assess the thickness of the macula, ganglion cell-inner plexiform layer (GCIPL), ganglion cell complex (GCC), and cpRNFL. Multivariate and correlation analyses were performed to evaluate the association of the demographic and ocular variables.

RESULTS

The average age of the 1762 (94.43%) students who underwent OCT assessment was 6.83 ± 0.46 years. Among them, 984 (53.02%) were boys. The number of students who had macular, cpRNFL, and optic disc scans completed and with adequate image quality were 1412 (82.2%), 1277 (74.4%), and 1243 (72.4%), respectively. The average macula full retinal thickness (FRT), GCIPL, GCC, and cpRNFL thickness of the students was 279.19 ± 10.61 μm, 76.41 ± 4.70 μm, 108.15 ± 6.15  μm, and 112.33 ± 13.5 μm, respectively. Multivariate regression and correlation analysis further revealed that boys and girls had significant differences in their average cpRNFL thickness. Moreover, GCC and GCIPL thickness was negatively correlated with IOP but positively correlated with the body mass index. The thickness of all the layers of the macula and cpRNFL were positively correlated with spherical equivalent. Further to this, the average macular FRT, GCIPL, and GCC thicknesses were positively correlated with cpRNFL global thickness.

CONCLUSION

This study describes the normal distribution of macular retina, cpRNFL, and optic disc parameters in grade-1 Tibetan children in Lhasa. It contributes to the establishment of a normative ophthalmology database of Tibetan children, and advances the ability of OCT in ophthalmic disorder diagnosis during long-term monitoring in plateau.

Intravitreal Use of a Bone Marrow Mononuclear Fraction (BMMF) Containing CD34+ Cells in Patients with Stargardt Type Macular Dystrophy

To assess the therapeutic potential and the safety of intravitreous use of a bone marrow mononuclear fraction (BMMF) containing CD34+ cells in patients with Stargardt type macular dystrophy. The study was conducted on 10 patients with Stargardt dystrophy with worse eye visual acuity ≤ 20/125. A bone marrow aspirate was obtained from all patients, and after processing in the cell therapy center (CTC), 0.1 ml of the intravitreous BMMF suspension was injected into the eye with worse visual acuity. A sham injection was performed in the contralateral eye. The patients were evaluated at baseline and one, three, and six months after the injection. All of them were submitted to measurement of best corrected visual acuity (BCVA), microperimetry, multifocal electroretinography (mfERG) and full field electroretinography (ffERG), autofluorescence (AF), and optical coherence tomography (OCT). Fluorescein angiography was also performed before and six months after the injection. All patients completed the six-month period of evaluation. Mean visual acuity of the treated eye was 1.1 logMAR (20/250) before intravitreous (IV) injection, 0.96 logMAR (20/200+2) one month after injection, and 0.92 logMAR (20/160-1) 3 months after injection. In the untreated eye, mean VA was 1.0 logMAR (20/200) at baseline and 0.96 logMAR (20/200+2) and 0.94 logMAR (20/160-2) one and three months after injection, respectively. In the treated group, VA at baseline ranged from best acuity of 20/125-1 to worst acuity of 20/640+2, going through 20/100+2 and 20/400 during the first month. In the untreated group, BCVA ranged from 20/100+2 to 20/400 at baseline and from 20/100 to 20/400 after one month. The results for the treated group differed significantly at all follow-up times, whereas no significant difference was observed in the untreated group. Regarding the mean sensitivity of microperimetry, although there was improvement throughout all months, a significant difference occurred only during the first month. In the untreated eye, there was no significant difference in any analysis. Angiofluoresceinography did not reveal neovessel formation or tumor growth. The remaining exams were used in order to aid the diagnosis. The results indicate that the use of intravitreous BMMF in patients with Stargardt dystrophy is safe and is associated with a discrete improvement of BCVA and microperimetry in the treated eye compared to the untreated one.

Macular and choroidal thicknesses in a healthy Hispanic population evaluated by high-definition spectral-domain optical coherence tomography (SD-OCT)

Purpose

To report normal values of macular and choroidal thickness obtained from a healthy Hispanic population using Optovue (Optovue Inc, Freemont CA, USA) spectral domain optical coherence tomography (SD-OCT).

Design

Observational, cross-sectional, correlation study.

Methods

A total of 290 eyes (145 healthy subjects) were included; 69% of subjects were female. The median age was 39 ± 29 years (IQR), with a range between 18 and 89 years. The study sample was stratified into three age groups: Group 1, 18–40 years (50.3%), Group 2, 41–60 years (30.7%), and Group 3, older than 61 years (19%). Central macular, perifoveal (inner quadrants), and parafoveal (outer quadrants) thicknesses were estimated. In addition, central and peripheral choroidal thicknesses were estimated. Data analysis was performed to calculate the standardized mean difference according to the variance (Student’s t-test) and its differences with Epidat 4.1.

Results

Median macular central thickness was 250 ±30 µm (IQR) with Optovue. Median central choroidal thickness was 263 ± 48 µm (IQR). Median central choroidal thickness was greater than mean peripheral thickness. Macular evaluation showed a statistically significant difference in central, perifoveal, and parafoveal thicknesses, with lower values being recorded for the study sample compared with the manufacturer’s data.

Conclusions

SD-OCT has become a useful tool to obtain high-resolution images of the macula and choroid. This method allows precise assessment of the retinal and choroidal layers to diagnose and follow up posterior segment diseases. We are reporting normal cut-off values of macular and choroidal thicknesses in healthy Hispanic subjects evaluated with Optovue SD-OCT as new diagnostic normal parameters for research and clinical activities.

ELLIPSOID ZONE MAPPING AND OUTER RETINAL ASSESSMENT IN STARGARDT DISEASE

PURPOSE

To quantify and correlate ellipsoid zone and photoreceptor outer segment changes with visual acuity in Stargardt disease.

METHODS

An institutional review board-approved study of 32 eyes with Stargardt disease was performed. After spectral domain optical coherence tomography, the macular cube was exported into a novel analysis tool and volumetric assessment from the ellipsoid zone to the retinal pigment epithelium was performed. Using this information, mapping was completed with en face representation of the height between the ellipsoid zone and retinal pigment epithelium. This analysis provided quantification of ellipsoid zone and photoreceptor outer segments, including atrophy (ellipsoid zone to retinal pigment epithelium thickness = 0 μm) and attenuation (ellipsoid zone to retinal pigment epithelium thickness <20 μm). These parameters were compared with visual acuity and controls (n = 12 eyes).

RESULTS

Visual acuity ranged from 20/30 to 20/250. The central foveal B-scan area of ellipsoid and photoreceptor outer segments was significantly less than controls (0.13 ± 0.05 mm vs. 0.17 ± 0.03 mm, respectively, P = 0.0074). The central foveal B-scan mean thickness measured 22.52 ± 9.0 μm in Stargardt versus 30.0 ± 5.08 μm (P = 0.0096). Atrophy and attenuation were significantly higher in Stargardt patients (22% vs. 1%, P = 0.005 and 43% vs. 1%, P = 0.0002). Visual acuity directly correlated with ellipsoid zone/outer segment volume (R = 0.57, P < 0.005) and inversely correlated with attenuation and atrophy (R = -0.53 and -0.57; P < 0.005 for all).

CONCLUSION

Eyes with Stargardt disease frequently have significant disruption of the ellipsoid zone and outer segments. This degenerative change was successfully quantified with a novel assessment platform and identified correlates with visual function. This software provides the opportunity for quantitative assessment and possible longitudinal surveillance.

Focal foveal atrophy of unknown etiology: clinical pictures and possible underlying causes

BACKGROUND/PURPOSE

Focal foveal atrophy is defined as the presence of a small, focal, ill-defined, hypopigmented foveal or juxtafoveal lesion, with the remaining retina unaffected. The purpose of this study was to report the clinical characteristics and optical coherence tomography (OCT) in patients with focal foveal atrophy of unknown etiology.

METHODS

The study was a retrospective observational case series. Data collected included complete ocular examination results for best corrected visual acuity (BCVA), ophthalmoscopy, fundus photography, fluorescein angiography, color sense discrimination tests, visual field tests, and OCT examinations.

RESULTS

Twenty-three eyes in 21 patients were examined. The mean patient age was 49.2 ± 15.4 years. The mean BCVA was 20/25. The 21 patients were divided into three groups according to OCT results. Group 1 eyes (n = 10) had intact inner and outer hyperreflective layers (HRLs), with the signal of the inner HRL corresponding to the junction between the inner and outer photoreceptor segments and the outer HRL corresponding to the retinal pigment epithelium (RPE). Group 2 eyes (n = 9) had small hyporeflective defects with defects in the inner HRL at the fovea but an intact outer HRL. Group 3 eyes (n = 4) had small hyporeflective defects in both the inner and outer HRLs at the fovea. Groups 3 eyes had significantly lower visual acuity compared to Group 1 eyes and Group 2 eyes. There was no significant difference in visual acuity between Group 1 and Group 2 eyes. There were no significant differences among the groups with respect to color vision or foveal thickness.

CONCLUSION

This is the first report of clinical presentations for patients with focal foveal atrophy of unknown etiology. OCT aided in the diagnosis and assessment of the degree of retinal structural abnormalities, but the real etiology of foveal atrophy remains unclear.

Optical coherence tomography in progressive cone dystrophy

AIM

The aim of the study was to analyse different clinical pictures in patients with progressive cone dystrophy (PCD), to compare these with the results of optical coherence tomography (OCT) and to evaluate the benefits of this method for diagnosis.

METHODS

The group consisted of 16 patients (32 eyes) with PCD. All patients were examined for visual acuity, colour sense and visual field. We performed biomicroscopic examination, photo-documentation, fluorescein angiography, electrophysiological tests and OCT.

RESULTS

Using biomicroscopy and fluorescein angiography, we found changes in the retinal pigment epithelium ranging from barely detectable changes up to the typical bull's eye appearance. In all the eyes, OCT established statistically significant reduction in the thickness and structural changes in the neuroretina of the macula. Atrophy was evident especially in the outer nuclear layer, in the photoreceptor inner segment/outer segment junction and in the retinal pigment epithelium. Visual acuity was mainly dependent on the degree to which the continuity of the photoreceptor inner segment/outer segment junction layer was maintained. Eyes with better preserved neuroretinal structure in the fovea centralis had generally less reduced thickness of the retina and a better visual acuity.

CONCLUSION

OCT specifies the quantitative and qualitative changes in the macula and may contribute significantly to the diagnosis of the progressive cone dystrophy, particularly in the early stages of the disease which is difficult to diagnose.

Clinical characteristics and visual function tests with retinal tomographic correlation in patients with Stargardt's disease in Taiwan

BACKGROUND/PURPOSE

Stargardt's disease is the most common form of juvenile macular dystrophy. The purpose of this study is to report the clinical characteristics, visual function, and retinal tomography of patients diagnosed with Stargardt's disease in Taiwan.

METHODS

Retrospective case series; data collected include results of complete ophthalmic examinations: best-corrected visual acuity (BCVA), slit-lamp biomicroscopy, indirect ophthalmoscopy, fundus photography, fluorescein angiography, color sense discrimination test, electroculography (EOG), electroretinography (ERG), dark adaptation, visual field test, and optical coherence tomography (OCT) examinations focused on the macular area.

RESULTS

Twenty patients were enrolled in this study. The mean age of the patients was 32.1 years. The mean logMAR-converted visual acuity of all patients was 0.96. Maculopathy with or without flecks was evident in all patients. Fluorescein angiography revealed hyperfluorescence in the macula of all cases. Varying degrees of color sense discrimination dysfunction were noted. Electrophysiologic studies showed subnormal to abnormal responses in most patients. Decreased foveal thickness was evident on OCT and foveal thickness was inversely associated with logMAR visual acuity. Also, logMAR visual acuity was associated with total error scores on the color sense discrimination test and the Arden ratio of EOG. The Arden ratio of EOG correlated with the thickness of the outer ring of the macula.

CONCLUSION

Typical clinical presentations of Stargardt's disease were demonstrated in our case series. OCT findings showed a correlation between foveal thickness and visual acuity, making OCT a useful predictor for other visual function tests. Our results indicate that OCT is helpful in the evaluation of visual acuity and the progression of maculopathy in patients with Stargardt's disease.

Do you know this syndrome?

Congenital hypotrichosis and Stargardt macular dystrophy are rare autosomal recessive disorder of unknown etiology respectively characterized by hair loss, macular degeneration and severe progressive vision reduction. There are few reports in the literature with this association. Studies show that the defective gene is on the chromosome I6q22.1 and involve cadherin molecule in the pathogenesis. Early recognition of these disorders often starts with hair changes and should alert the dermatologist for an eye examination thereby avoiding more severe ocular defect.

Retro-mode imaging and fundus autofluorescence with scanning laser ophthalmoscope of retinal dystrophies

Background

Retinal dystrophies display a considerably wide range of phenotypic variability, which can make diagnosis and clinical staging difficult. The aim of the study is to analyze the contribution of retro-mode imaging (RMI) and fundus autofluorescence (FAF) to the characterization of retinal dystrophies.

Methods

Eighteen consecutive patients affected by retinal dystrophies underwent a complete ophthalmological examination, including best corrected visual acuity with ETDRS charts, blue-light fundus autofluorescence, (BL-FAF), near-infrared fundus autofluorescence (NIR-FAF), and RMI. The primary outcome was the identification of abnormal patterns on RMI. The secondary outcome was the correlation with the findings on BL-FAF and NIR-FAF.

Results

Overall, the main feature of RMI is represented by a pseudo-3D pattern of all the lesions at the posterior pole. More specifically, any accumulation of material within the retina appears as an area of elevation of different shape and size, displaying irregular and darker borders. No precise correlations between RMI, BL-AF, and NIR-AF imaging was found.

Conclusions

RMI and FAF appear to be useful tools for characterizing retinal dystrophies. Non-invasive diagnostic tools may yield additional information on the clinical setting and the monitoring of the patients.

Infrared scanning laser ophthalmoscope imaging of the macula and its correlation with functional loss and structural changes in patients with stargardt disease

PURPOSE

To correlate the degree of functional loss with structural changes in patients with Stargardt disease.

METHODS

Eighteen eyes of 10 patients with Stargardt disease were studied. Scanning laser ophthalmoscope infrared images were compared with corresponding spectral-domain optical coherence tomography scans. Additionally, scanning laser ophthalmoscope microperimetry was performed, and results were superimposed on scanning laser ophthalmoscope infrared images and in selected cases on fundus autofluorescence images.

RESULTS

Seventeen of 18 eyes showed a distinct hyporeflective foveal and/or perifoveal area with distinct borders on scanning laser ophthalmoscope infrared images, which was less evident on funduscopy and incompletely depicted in fundus autofluorescence images. This hyporeflective zone corresponded to areas of significantly elevated psychophysical thresholds on microperimetry testing, in addition to thinning of the retinal pigment epithelium and disorganization or loss of the photoreceptor cell inner segment-outer segment junction and external-limiting membrane on spectral-domain optical coherence tomography.

CONCLUSION

Scanning laser ophthalmoscope infrared fundus images are useful for depicting retinal structural changes in patients with Stargardt disease. A spectral-domain optical coherence tomography/scanning laser ophthalmoscope microperimetry device allows for a direct correlation of structural abnormalities with functional defects that will likely be applicable for the determination of retinal areas for potential improvement of retinal function in these patients during future clinical trials and for the monitoring of the diseases' natural history.

Disruption in Bruch membrane in patients with Stargardt disease

PURPOSE

To describe the spectral domain-optical coherence tomography (SD-OCT) findings of two patients with complete defects in the retinal pigment epithelium (RPE) with disruptions in Bruch membrane in Stargardt disease (STGD1).

METHODS

Two patients with STGD1 were referred to our clinic for further evaluation. Fundus autofluorescence (FAF), spectral domain optical coherence tomography (SD-OCT), electroretinography (ERG) and Microperimetry (MP-1) were performed to assess the retinal anatomy and function. Screening for mutations in the ABCA4 gene was carried out and detected mutations were confirmed by direct sequencing.

RESULTS

Both patients had bilateral macular geographic atrophy (GA) and yellowish subretinal pisciform flecks and mutations were detected in the ABCA4 gene by chip screening. SD-OCT revealed marked atrophy of the retina in the central macula, with focal defects in the RPE with disruptions in Bruch membrane and herniation of the retina through the defect in three of four eyes.

CONCLUSION

This case report highlights the necessity for a detailed ophthalmic examination including SD-OCT of patients with STGD1.

The use of SD-OCT in the differential diagnosis of dots, spots and other white retinal lesions

PURPOSE

To demonstrate the utility of a retinal imaging technique using spectral domain optical coherence tomography (SD-OCT) for creating a B-scan layer-by-layer analysis to aid in the differential diagnosis of various retinal dots, spots, and other white lesions.

DESIGN

Review.

METHODS

A retrospective review of imaging studies performed with SD-OCT (Topcon, 3DOCT-2000, Oakland, NJ) at SUNY State College of Optometry.

RESULTS

B-scan layer-by-layer analysis and unique SD-OCT reflectivity patterns of the following retinal white lesions are reviewed in the order of their retinal layer localization: myelinated nerve fiber layer, cotton wool spot, exudates, edema residues, drusen, fundus albipunctatus, Stargardt disease, Bietti crystalline dystrophy, punctate inner choroidopathy (PIC), presumed ocular histoplasmosis syndrome (POHS), post-photocoagulation chorioretinal scarring, and osseous choristoma.

CONCLUSION

The reviewed images demonstrate the utility of SD-OCT in the identification of the unique characteristics of the presented retinal pathologies. SD-OCT is ideal for retinal layer localization of lesions, thus enhancing the differential diagnosis of retinal dots, spots, and other white lesions. Even though true pathognomonic patterns are rare, highly suggestive findings of certain retinal abnormalities often facilitate immediate recognition and diagnosis.

Choroidal imaging in inherited retinal disease using the technique of enhanced depth imaging optical coherence tomography

PURPOSE

The aim of this study is to image and describe the in vivo choroidal changes in various retinal dystrophies using the technique of enhanced depth imaging (EDI) optical coherence tomography (OCT) and to correlate these findings with the clinical appearance. Associations between choroidal change and genotype, visual acuity and results of retinal electrophysiology are also explored.

DESIGN

Retrospective observational case series.

METHODS

Twenty patients attending the medical retina clinics at Moorfields Eye Hospital underwent EDI OCT choroidal scans as part of the scanning protocol when they underwent OCT imaging with the Spectralis HRA and OCT. The choroidal images were obtained by moving the Spectralis camera close enough to obtain an inverted image of the retina. The scans were read by two experienced OCT readers assessing the choroidal thickness as well as the choroidal contour for focal areas of choroidal thinning corresponding to the areas of RPE/outer retinal atrophy. The spectrum of patients included those with Stargardt macular dystrophy, macular dystrophies secondary to known mutations such as peripherin/RDS, uncharacterised macular dystrophies, Best disease, bifocal chorioretinal atrophy, Bietti crystalline retinal dystrophy and choroideraemia.

RESULTS

The choroidal appearance was symmetrical in all patients who had both eyes scanned. Ten patients showed no choroidal thinning, five had focal mild to moderate choroidal thinning, three had focal severe choroidal thinning, and two patients had diffuse severe choroidal thinning. There was no association between choroidal thinning and visual acuity [Fisher's exact test, p = 0.350 (right eye), p = 1.000 (left eye)], or extent of retinal dysfunction on electrophysiology (Fisher's exact test, p = 1.000).

CONCLUSION

Enhanced depth imaging using spectral domain OCT can be used to identify choroidal changes in inherited retinal disease. The pattern of choroidal change correlates well with the clinical appearance. It appears that the extent and pattern of choroidal thinning is dependent on the stage of the disease in some cases, and in others the causative gene defect.

A comparison of multifocal ERG and frequency domain OCT changes in patients with abnormalities of the retina

To compare the ability of the multifocal electroretinogram (mfERG) and frequency domain optical coherence tomography (fdOCT) to detect retinal abnormalities. A total of 198 eyes (100 patients) were referred by neuro-ophthalmologists to rule out a retinal etiology of visual impairment. All patients were evaluated with static automated perimetry (SAP) (Humphrey Visual Field Analyzer; Zeiss Meditec), mfERG (Veris, EDI) and fdOCT (3D-OCT 1000, Topcon). The mfERG was performed with 103 scaled hexagons and procedures conforming to ISCEV standards (Hood DC et al. (2008) Doc Ophthalmol 116(1):1-11). The fdOCT imaging included horizontal and vertical line scans through the fovea. Local mfERG and fdOCT abnormalities were compared to local regions of visual field sensitivity loss measured with SAP and categorized as normal/inconclusive or abnormal. 146 eyes were categorized as normal retina on both fdOCT and mfERG. The retina of 52 eyes (36 patients) was categorized as abnormal based upon mfERG and/or fdOCT. Of this group, 25 eyes (20 patients) were abnormal on both tests. However, 20 eyes (13 patients) were abnormal on mfERG, while the fdOCT was normal/inconclusive; and 7 eyes (7 patients) had normal or inconclusive mfERG, but abnormal fdOCT. Considerable disagreement exists between these two methods for detection of retinal abnormalities. The mfERG tends to miss small local abnormalities that are detectable on the fdOCT. On the other hand, the fdOCT can appear normal in the face of clearly abnormal mfERG and SAP results. While improved imaging and analysis may show fdOCT abnormalities in some cases, in others early damage may not appear on structural tests.

Optical coherence tomography - development, principles, applications

This paper presents a review of the development of optical coherence tomography (OCT), its principles and important applications. Basic OCT systems are described and the physical foundations of OCT signal properties and signal recording systems are reviewed. Recent examples of OCT applications in ophthalmology, cardiology, gastroenterology and dermatology outline the relevance of this advanced imaging modality in the medical field.

Depth-resolved measurement of ocular fundus pulsations by low-coherence tissue interferometry

A device that allows for the measurement of ocular fundus pulsations at preselected axial positions of a subject's eye is presented. Unlike previously presented systems, which only allow for observation of the strongest reflecting retinal layer, our system enables the measurement of fundus pulsations at a preselected ocular layer. For this purpose the sample is illuminated by light of low temporal coherence. The layer is then selected by positioning one mirror of a Michelson interferometer according to the depth of the layer. The device contains a length measurement system based on partial coherence interferometry and a line scan charge-coupled device camera for recording and online inspection of the fringe system. In-vivo measurements in healthy humans are performed as proof of principle. The algorithms used for enhancing the recorded images are briefly introduced. The contrast of the observed interference pattern is evaluated for different positions of the measurement mirror and at various distances from the front surface of the cornea. The applications of such a system may be wide, including assessment of eye elongation during myopia development and blood-flow-related changes in intraocular volume.

A comparison of fundus autofluorescence and retinal structure in patients with Stargardt disease

PURPOSE

To improve the understanding of Stargardt disease by comparing structural changes seen on spectral domain optical coherence tomography (SD-OCT) to those visible on fundus autofluorescence (FAF).

METHODS

FAF and SD-OCT were performed on 22 eyes of 11 patients with Stargardt disease. SD-OCT images were obtained at the fovea and at the eccentric preferred retinal locus (PRL). The diameters of absent (hypoautofluorescence) and abnormal FAF areas were measured. The extent of the transverse defect of the junction between the inner and outer segments of the photoreceptors (IS-OS) was measured in the foveal area. The PRL was evaluated with fundus photography and microperimetry.

RESULTS

Twenty-one of 22 eyes showed defective FAF. In 17 eyes, FAF was absent in the fovea and in four eyes, FAF was abnormal. All eyes showed disorganization and/or loss of the IS-OS junction in the foveal area on SD-OCT. The diameter of the absent FAF area was smaller than the measurement of the IS-OS junction loss; the latter was closer to the diameter of the abnormal FAF area. Seventeen eyes had an eccentric PRL associated with a retinal area with no defects on FAF.

CONCLUSIONS

In the majority of eyes, changes shown by SD-OCT correlated well with changes in FAF. However, in three patients, photoreceptor abnormalities were seen in the fovea on SD-OCT without an equivalent abnormality on FAF. This result suggests that in these patients, the structural integrity of the photoreceptors may be affected earlier than changes in the RPE at least as detected by FAF.

Comparison of clinically relevant findings from high-speed fourier-domain and conventional time-domain optical coherence tomography

PURPOSE

To compare the sensitivities of high-speed Fourier-domain optical coherence tomography (FD-OCT) and conventional time-domain (TD) OCT for the detection of clinical findings important in the management of common vitreoretinal disorders.

DESIGN

Prospective, observational study.

METHODS

FD-OCT scans (128 B scans x 512 A scans) were obtained using a prototype instrument (3 D-OCT; Topcon, Tokyo, Japan) in 50 eyes of 28 consecutive patients undergoing conventional high-resolution (6 B scans x 512 A scans) TD-OCT imaging (Stratus OCT; Carl Zeiss Meditec, Dublin, California, USA). Each image set was reviewed independently for the presence of clinical findings of interest, and device sensitivities were calculated.

RESULTS

The average sensitivity for detection of all features in this study was 94% for FD-OCT and 60% for TD-OCT. Clinical findings were identical between devices in 18% (9/50) of cases. FD-OCT detected features that were not visible on conventional OCT scans in 78% (39/50) of cases. FD-OCT was more sensitive than TD-OCT for the detection of multiple findings, including diffuse intraretinal edema (87% vs 60.9%), subretinal fluid (100% vs 46.2%), large pigment epithelium detachments (100% vs 81%), and subretinal tissue (100% vs 61.5%).

CONCLUSIONS

FD-OCT seems to be superior to TD-OCT for the detection of many clinically relevant features of vitreoretinal disease. The greater sensitivity of FD-OCT systems for the detection of intraretinal and subretinal fluid may be of particular importance for the treatment of patients with neovascular age-related macular edema. FD-OCT is likely to supplant TD-OCT as the standard of care for retinal specialists in the near future.

Imaging of titanium:sapphire laser retinal injury by adaptive optics fundus imaging and Fourier-domain optical coherence tomography

PURPOSE

To examine and observe the subtle retinal injuries caused by a titanium:sapphire laser with a high-resolution adaptive optics (AO) fundus camera and with Fourier-domain optical coherence tomography (FD-OCT).

DESIGN

Observational case series.

METHODS

Four eyes of 2 individuals who experienced an accidental exposure to reflected light from a titanium:sapphire laser were examined. High-resolution retinal images were obtained with the AO fundus camera and by FD-OCT, and the images were compared with the findings obtained by standard clinical tests, including the Amsler test and fluorescein angiography (FA).

RESULTS

The photoreceptor mosaic was absent in a localized area of the fovea in the images obtained by the AO fundus camera, and the photoreceptor outer segments (OS) were disrupted at the corresponding area in the FD-OCT images. The changes were detected not only in the symptomatic eye but also in the asymptomatic fellow eye in both patients. In 3 eyes, the geographic dark area in the AO image decreased during the follow-up examinations.

CONCLUSIONS

Very small, localized photoreceptor disruptions can be detected in patients with minimal titanium:sapphire laser injury by cross-sectional imaging using OCT, but their extent was delineated more precisely by en face AO imaging. Because the area of the photoreceptor disruption is very small, especially in the nonsymptomatic fellow eye, it is strongly recommended that laser workers--even those without visual symptoms--be examined by FD-OCT, an AO camera, or both if they have not worn protective goggles while using a laser.

Three-dimensional ultrahigh resolution optical coherence tomography imaging of age-related macular degeneration

Ultrahigh resolution optical coherence tomography (OCT) enhances the ability to visualize different intra retinal layers. In age-related macular degeneration (AMD), pathological changes in individual retinal layers, including photoreceptor inner and outer segments and retinal pigment epithelium, can be detected. OCT using spectral / Fourier domain detection enables high speed, volumetric imaging of the macula, which provides comprehensive three-dimensional tomographic and morphologic information. We present a case series of AMD patients, from mild drusen to more advanced geographic atrophy and exudative AMD. Patients were imaged with a research prototype, ultrahigh resolution spectral / Fourier domain OCT instrument with 3.5 microm axial image resolution operating at 25,000 axial scans per second. These cases provide representative volumetric datasets of well-documented AMD pathologies which could be used for the development of visualization and imaging processing methods and algorithms.

Ultrahigh-resolution versus speckle noise-reduction in spectral-domain optical coherence tomography

Ultrahigh-resolution (UHR) spectral-domain optical coherence tomography (SD-OCT) and speckle noise-reduced SD-OCT instruments were compared with regard to their ability to visualize retinal microstructures and detect micropathologies in the same series of eyes in this hospital-based study. Both the instruments identically visualized normal retinal structures, except for the retinal ganglion cell layer, which was better delineated by the speckle noise-reduced SD-OCT instrument. Retinal pigment epithelium (RPE) and Bruch's membrane were better delineated by UHR SD-OCT. Retinal and sub-RPE pathologies were also identically visualized by both the instruments. Layer differentiation for locating each pathology was better visualized by speckle noise-reduced SD-OCT.

Comparison of reflectivity maps and outer retinal topography in retinal disease by 3-D Fourier domain optical coherence tomography

We demonstrate and compare two image processing methods for visualization and analysis of three-dimensional optical coherence tomography (OCT) data acquired in eyes with different retinal pathologies. A method of retinal layer segmentation based on a multiple intensity thresholding algorithm was implemented in order to generate simultaneously outer retinal topography maps and reflectivity maps. We compare the applicability of the two methods to the diagnosis of retinal diseases and their progression. The data presented in this contribution were acquired with a high speed (25,000 A-scans/s), high resolution (4.5 microm) spectral OCT prototype instrument operating in the ophthalmology clinic.

Evaluation of macular abnormalities in Stargardt's disease using optical coherence tomography and scanning laser ophthalmoscope microperimetry

BACKGROUND

The purpose of this study is to evaluate the diagnostic value of optical coherence tomography (Stratus OCT) and scanning laser ophthalmoscope (SLO) microperimetry in patients with Stargardt's disease (STGD), and the correlation between macular morphology and visual function in these patients.

METHODS

Twenty-two patients with STGD (mean age 44 years, range 11 to 71 years) and 20 age-matched healthy control subjects were included in the study. OCT imaging was performed using six radial line scans manually centered on the fovea. SLO microperimetry was used to assess central scotoma and fixation behavior in patients with STGD.

RESULTS

Mean best corrected Snellen visual acuity (BCVA) was 20/80, range 20/25 to 20/300 (log MAR 0.6, range 0.1 to 1.2) in the STGD group and 20/20 (log MAR 0.0) in the control group. Foveal thickness was significantly reduced in patients with STGD (119.0 +/- 19.6 microm) compared to controls (210.7 +/- 19.6 microm, P < 0.0001). A significant correlation between foveal thickness and BCVA was observed within the STGD group (R(2) = 0.62, P < 0.0001). Photoreceptor loss in the macular area and a corresponding central scotoma were observed in all STGD patients.

CONCLUSIONS

OCT findings, particularly reduced foveomacular thickness and photoreceptor loss in the macular area may be useful in the diagnosis of STGD. Furthermore, a strong correlation between foveal thickness and visual function was observed in our patients. Assessment of central visual function using SLO microperimetry provides additional useful information, important in the management of STGD.

The spectrum of retinal dystrophies caused by mutations in the peripherin/RDS gene

Peripherin/rds is an integral membrane glycoprotein, mainly located in the rod and cone outer segments. The relevance of this protein to photoreceptor outer segment morphology was first demonstrated in retinal degeneration slow (rds) mice. Thus far, over 90 human peripherin/RDS gene mutations have been identified. These mutations have been associated with a variety of retinal dystrophies, in which there is a remarkable inter- and intrafamilial variation of the retinal phenotype. In this paper, we discuss the characteristics of the peripherin/RDS gene and its protein product. An overview is presented of the broad spectrum of clinical phenotypes caused by human peripherin/RDS gene mutations, ranging from various macular dystrophies to widespread forms of retinal dystrophy such as retinitis pigmentosa. Finally, we review the proposed genotype-phenotype correlation and the pathophysiologic mechanisms underlying this group of retinal dystrophies.

Spectral-domain optical coherence tomography with multiple B-scan averaging for enhanced imaging of retinal diseases

OBJECTIVE

To determine whether multiple B-scan averaging improves the quality of spectral-domain optical coherence tomography (SD OCT) images of the retina.

DESIGN

Prospective cross-sectional study.

PARTICIPANTS

One hundred one eyes of 84 patients with various retinal diseases.

METHODS

A prototype SD OCT system was used with a sensitivity of 98 decibels, air axial resolution of 6.1 mum, and acquisition rate of approximately 18 700 axial scans per second. To evaluate multiple B-scan averaging, a set of 12 B-scan images was obtained at the identical retinal location and the multiple scans were averaged using custom software; some images containing lateral eye motion were rejected. Objective differences in image quality were measured by comparing the contrast-to-noise ratios (CNRs) for key retinal structures in unenhanced and enhanced images using non-repeated-measures analysis of variance and the Dennett post hoc test. Subjective differences in image quality were evaluated by asking trained ophthalmologists independently to rank pairs of unenhanced and enhanced SD OCT images on a 5-point scale (upper or lower image definitely better, slightly better, or equal) and analyzing results using the Scheffe method for paired comparisons.

MAIN OUTCOME MEASURES

Contrast-to-noise ratio in enhanced versus unenhanced SD OCT images, expert comparison of image quality, and retinal pathologic features in enhanced versus unenhanced SD OCT images.

RESULTS

Averaging >4 SD OCT scans achieved significant improvement in CNR and also improved ophthalmologists' ability to distinguish retinal structures. More than 4 scans could be averaged for 100 (99%) of the 101 eyes with retinal diseases in this study. Averaging >4 SD OCT scans improved visualization of structures, such as abnormalities in the photoreceptor layer and sub-retinal pigment epithelium (RPE) lesions, that could not be identified clearly in single-scan SD OCT images because of various retinal pathologic features. These included intraretinal lesions that mask the underlying structures, such as cystoid macular edema and retinal hemorrhage, and inward shifting of the sensory retina because of pigment epithelial detachment and lesions beneath the RPE.

CONCLUSIONS

Multiple B-scan averaging is an easy and practical method to improve the quality of retinal images obtained by SD OCT and thereby to improve the diagnosis and management of retinal diseases.

Three-dimensional imaging of the foveal photoreceptor layer in central serous chorioretinopathy using high-speed optical coherence tomography

OBJECTIVE

To describe the 3-dimensional (3-D) imaging of the pathologic changes in the foveal photoreceptor layer in eyes with central serous chorioretinopathy (CSC) using high-speed optical coherence tomography (OCT).

DESIGN

Prospective observational case series.

PARTICIPANTS

Twenty-seven eyes of 27 consecutive patients with various stages of CSC.

METHODS

A prototype high-speed OCT system was fabricated for patient examinations based on Fourier domain OCT. The system had a sensitivity of 98 dB, a tissue axial resolution of 4.3 mum, and an acquisition rate of approximately 18700 axial scans per second. Three-dimensional imaging was performed based on a raster-scan protocol.

MAIN OUTCOME MEASURES

Anatomic features of CSC distinguished by 3-D OCT.

RESULTS

A line corresponding to backreflection from the external limiting membrane (ELM) was visible in images from eyes with all stages of CSC, including 6 in the acute, 5 in the chronic, and 9 in the recurrent phase of retinal detachment and 11 examined in the quiescent phase (including 4 reexamined after reattachment). Backreflection from the photoreceptor inner and outer segment junction (IS/OS) was missing before but present after reattachment. The ELM line bordered the photoreceptor nuclear and inner segment layers, clearly showing that CSC primarily alters the outer segment (OS) layer. Punctate areas of intense reflectivity were observed more frequently in the OS layer of detached retinas in cases of chronic or recurrent versus acute CSC (P<0.05, chi-square test). Of 11 eyes with reattached macula, 3 eyes with large defects in the subfoveal IS/OS had poor visual acuity (VA), and 8 eyes with small or no defects had good VA (P<0.05 and P<0.001, chi-square test). Decreases in foveal full and outer thickness were associated with VA loss (P<0.05 and P<0.001, Spearman rank correlation test).

CONCLUSIONS

Three-dimensional OCT imaging delineates the microstructural changes that occur within the photoreceptor layers and demonstrates the spatial relationship between the laterally spreading or scattering microstructures and the fovea in eyes with CSC. Visualization of the 3-D relationship between the ELM and each photoreceptor layer before and after macular reattachment facilitates understanding of anatomic and vision changes that result from CSC.

Recent developments in optical coherence tomography for imaging the retina

Optical coherence tomography (OCT) was introduced in ophthalmology a decade ago. Within a few years in vivo imaging of the healthy retina and optic nerve head and of retinal diseases was a fact. In particular the ease with which these images can be acquired considerably changed the diagnostic strategy used by ophthalmologists. The OCT technique currently available in clinical practice is referred to as time-domain OCT, because the depth information of the retina is acquired as a sequence of samples, over time. This can be done either in longitudinal cross-sections perpendicular to, or in the coronal plane parallel to the retinal surface. Only recently, major advances have been made as to image resolution with the introduction of ultrahigh resolution OCT and in imaging speed, signal-to-noise ratio and sensitivity with the introduction of spectral-domain OCT. Functional OCT is the next frontier in OCT imaging. For example, polarization-sensitive OCT uses the birefringent characteristics of the retinal nerve fibre layer to better assess its thickness. Blood flow information from retinal vessels as well as the oxygenation state of retinal tissue can be extracted from the OCT signal. Very promising are the developments in contrast-enhanced molecular optical imaging, for example with the use of scattering tuneable nanoparticles targeted at specific tissue or cell structures. This review will provide an overview of these most recent developments in the field of OCT imaging focussing on applications for the retina.