Complete circumvention of central retinal artery and venous cilioretinal shunts in optic disc drusen

Volumetric Measurement of Optic Nerve Head Drusen Using Swept-Source Optical Coherence Tomography

PURPOSE

To describe new software tools for quantifying optic nerve head drusen volume using 3-dimensional (3D) swept-source optical coherence tomography (SS-OCT) volumetric scans.

MATERIALS AND METHODS

SS-OCT was used to acquire raster volume scans of 8 eyes of 4 patients with bilateral optic nerve head drusen. The scans were manually segmented by 3 graders to identify the drusen borders, and thereafter total drusen volumes were calculated. Linear regression was performed to study the relationships between drusen volume, retinal nerve fiber layer thickness, and Humphrey visual field mean deviation.

RESULTS

In the 8 study eyes, drusen volumes ranged between 0.24 to 1.05 mm. Visual field mean deviation decreased by ∼20 dB per cubic millimeter increase in drusen volume, and the coefficient of correlation of the linear regression was 0.92. In this small patient series, visual field defects were detected when drusen volume was larger than about 0.2 mm.

CONCLUSIONS

Software tools have been developed to quantify the size of OHND using SS-OCT volume scans.

Visual field loss in optic disc drusen patients correlates with central retinal artery blood velocity patterns

PURPOSE

(1) To characterize the retrobulbar circulation in patients with optic disc drusen (ODD) using colour Doppler imaging; (2) to explore the differences in retrobulbar hemodynamics in patients with primary open-angle glaucoma (POAG).

METHODS

Retrospective analysis using three diagnostic groups: patients with ODD, age-matched healthy controls and age- and visual defect-matched patients with POAG. Subjects with history of ocular trauma or ocular diseases including vascular-related diseases were excluded. Kruskal-Wallis and Spearman's correlation tests were performed to compare and explore the correlations between the hemodynamic parameters and visual field damage.

RESULTS

Sixty patients were included and equally divided between the three groups. Patients with ODD had lower systolic and diastolic flow velocities in the central retinal artery (CRA) when compared to healthy individuals, but no difference was found with the glaucoma group (p < 0.005 versus healthy; p range 0.30-0.37 versus POAG). The systolic shift in flow patterns correlated with the extent of visual field defect in ODD patients (p < 0.001, r = -0.78, confidence interval: -0.43 to -0.92), but not in POAG (p = 0.73). Short ciliary arteries from ODD patients had lower mean systolic flow velocities when compared to both healthy individuals and patients with POAG (p < 0.01 versus healthy; p ≤ 0.04 versus POAG). The ophthalmic artery in ODD group had significantly higher mean blood velocities than in the POAG (p = 0.04), while showing a significant overlap in Doppler waveform variables to the control group (p range 0.08-0.97).

CONCLUSIONS

Similar to patients with glaucoma, individuals with ODD have low blood flow velocities in the vessels around the optic nerve head. Unlike patients with glaucoma, however, their CRA's blood flow velocity patterns correlate with the extent of the visual field defects.

Snapshot hyperspectral retinal camera with the Image Mapping Spectrometer (IMS)

We present a snapshot hyperspectral retinal camera with the Image Mapping Spectrometer (IMS) for eye imaging applications. The resulting system is capable of simultaneously acquiring 48 spectral channel images in the range 470 nm-650 nm with frame rate at 5.2 fps. The spatial sampling of each measured spectral scene is 350 × 350 pixels. The advantages of this snapshot device are elimination of the eye motion artifacts and pixel misregistration problems in traditional scanning-based hyperspectral retinal cameras, and real-time imaging of oxygen saturation dynamics with sub-second temporal resolution. The spectral imaging performance is demonstrated in a human retinal imaging experiment in vivo. The absorption spectral signatures of oxy-hemoglobin and macular pigments were successfully acquired by using this device.

Cilioretinal arteries in diabetic eyes are associated with increased retinal blood flow velocity and occurrence of diabetic macular edema

PURPOSE

The main purpose was to investigate the relationship between occurrence of cilioretinal arteries and macular edema in diabetic eyes in terms of retinal blood flow characteristics revealed by the Retinal Function Imager (RFI). Other standard imaging techniques such as fundus photography, fluorescein angiography, and spectral-domain optical coherence tomography/scanning laser ophthalmoscopy were also used along with the RFI. The additional purpose was to look for the evidence of cilioretinal-retinal collaterals using the RFI.

METHODS

Patients with a diagnosis of diabetic retinopathy were included. All patients underwent fundus photography, fluorescein angiography, spectral-domain optical coherence tomography, and imaging using RFI. The presence of cilioretinal artery (CilRA) was recognized using color/red-free fundus photographs, fluorescein angiography, and RFI. There were two groups according to the presence (CilRA group) or absence (NoCilRA group) of cilioretinal artery or arteries in the study eye.

RESULTS

Thirty-nine eyes with diabetic retinopathy were included. Cilioretinal artery was identified in 15 eyes (38%). In the CilRA group, spectral-domain optical coherence tomography evidence of macular edema was observed in 13 of 15 eyes (87%), whereas in the NoCilRA group, macular edema was observed on spectral-domain optical coherence tomography in 7 of 24 eyes (29%). Mean blood flow velocities in retinal arteries and veins were significantly higher in diabetic eyes with cilioretinal artery (P = 0.04 and P = 0.005, respectively). Mean blood velocity in cilioretinal arteries was significantly higher in comparison with the mean arterial blood velocity (P = 0.03). In the CilRA group, cilioretinal-retinal collaterals, assessed by RFI, were detected in 4 of 15 eyes (27%) with cilioretinal arteries. In the NoCilRA group, mean blood velocity in retinal veins was significantly higher in eyes with macular edema in comparison with those without macular edema (P = 0.03).

CONCLUSION

Using the RFI in conjunction with standard fundus imaging techniques, the presence of cilioretinal artery in diabetic eyes was found to be associated with increased retinal blood flow velocity and increased occurrence of diabetic macular edema. The occurrence of cilioretinal-retinal collaterals was also noted; however, the pathophysiologic significance of this finding requires further investigation.

Imaging of optic nerve head drusen: improvements with spectral domain optical coherence tomography

OBJECTIVE

To demonstrate a new algorithm that can determine the shape, location, and volume of optic nerve head drusen (ONHD), which were imaged with spectral domain optical coherence tomography (SDOCT).

METHODS

One exenteration patient and 4 glaucoma patients with bilateral ONHD were recruited from the Massachusetts Eye and Ear Infirmary and from a private practice office. Images were obtained using an experimental SDOCT system developed at the Wellman Center for Photomedicine, Massachusetts General Hospital. With axial resolutions of about 6 mum, SDOCT can obtain 2-dimensional images in 1/29 of a second, compared with commercially available time domain OCT instruments with 10 mum resolution images in 1.28 seconds. The volumes of ONHD were calculated with a new algorithm and were then correlated with visual field mean deviation.

RESULTS

SDOCT can display 2-dimensional images comparable with histology and 3-dimensional videos of ONHD. ONHD are signal-poor regions with high-signaled borders. Larger ONHD volumes are directly correlated with larger mean deviation absolute values on Humphrey visual field testing.

CONCLUSIONS

SDOCT is a potentially better technique for ONHD imaging and may improve the diagnosis and management of patients with both OHND and glaucoma.

Advanced visual field loss secondary to optic nerve head drusen: case report and literature review

BACKGROUND

Optic nerve head drusen (ONHD) is a relatively uncommon condition that results from calcific degeneration of axons within the optic nerve. The abnormal drusen bodies can enlarge, compressing normal nerve structures, and ultimately may result in vision loss. Drusen often are discovered through clinical evaluation with a dilated funduscopic examination. Ancillary testing, including computed tomographic (CT) imaging, B-scan ultrasonography, autofluorescence imaging, nerve fiber layer imaging, and threshold visual field evaluation are helpful to confirm the existence of ONHD and to evaluate for progression of this condition.

CASE REPORT

This case report discusses the clinical presentation of a patient with advanced visual field loss from ONHD and the ancillary testing used to confirm the diagnosis. A complete review of literature on ONHD is discussed.

CONCLUSIONS

Currently, there is no cure or direct treatment for progressive vision loss or complications that may develop from ONHD. Useful diagnostic tools include serial automated threshold visual fields, nerve fiber layer analysis, and fundus photography. It is suggested that ocular hypotensive agents be used to lower intraocular pressure prophylactically to prevent further nerve fiber layer and optic nerve damage.

The rate of visual field loss in optic nerve head drusen

PURPOSE

To define the rate of visual field loss in patients with optic nerve head drusen (ONHD).

DESIGN

Retrospective chart review.

METHODS

Goldmann visual field (GVF) testing from initial visit and last follow-up examination were quantified using the modified Esterman grid technique. The rate of visual field loss was calculated by comparing the initial GVF to the last follow-up GVF. A comparative analysis of GVF and age at initial evaluation was performed on all patients with an initial GVF only.

SETTING

Tertiary academic care center.

PARTICIPANTS

Inclusion criteria for the rate analysis: (1) diagnosis of ONHD and (2) at least 36 months of follow-up with serial GVF testing.

EXCLUSION CRITERIA

(1) patients with glaucoma or glaucoma-suspect; (2) history or examination evidence for other ocular disease; and (3) drusen-related macular causes of visual loss.

RESULTS

Thirty-two of 292 charts were included in the rate analysis. The rate of visual field loss was 1.58%. There was no statistically significant difference between men and women (P = .74). One hundred eighty patients were included in the initial visual field analysis. There was a significant negative correlation between age and GVF, with older patients having lower GVF scores with a Spearman correlation of -0.42 (P < 0.0001); 73% of these 180 patients had mild, minimal, or no visual field loss.

CONCLUSIONS

The rate of visual field loss for ONHD over a 36-month interval of time was 1.6% per year. Patients with minimal or no visual field loss were younger, and patients with moderate or severe visual loss were older.

Optic disk drusen

Optic disk drusen occur in 3.4 to 24 per 1,000 population and are bilateral in approximately 75%. Disturbance in the axonal metabolism in the presence of a small scleral canal--regardless of eyelength--is considered responsible for the development. The drusen increase in size, becoming more visible with age due to continuing calcium apposition, and they are associated with visual field defects in a considerable number of patients. Patients do not usually notice these defects, despite their progressive nature over the years, and this indicates an insidious course. A correct diagnosis of optic disk drusen is mandatory, although effective treatment is not yet available. It is most important to differentiate optic disk drusen from papilledema in order to avoid unnecessary neurological examinations, but also to avoid overlooking genuine neurologic disorders. Because optic disk drusen can cause severe visual field defects, patients require individual consultation regarding work issues and whether or not to drive. Optic disk drusen can be accompanied by vascular complications as well. In some cases these vascular changes--for example, choroidal neovascularization--are treatable. Patients with optic disk drusen should undergo regular visual field, IOP, and nerve fiber layer examinations. In patients with deteriorating visual field and borderline IOP, we recommend antiglaucomatous therapy.