Peripapillary venous drainage from the choroid: a variable feature in human eyes

Incisional choroidal surgery

The choroid is a thin layer of highly vascular uveal tissue enclosed externally by sclera and internally by neurosensory retinal tissue. The choroid is a "middle layer" ocular tissue with anatomically challenging surgical access. The primary functional role of the choroid is to provide rapid, oxygenated, and nutrient-rich blood flow to both the highly metabolic retinal pigment epithelium and outer retina (i.e. photoreceptors) while simultaneously removing waste products. Historically, incisional choroidal surgery (ICS) has involved tumor biopsy or excision, removal of choroidal neovascular complex or autologous choroidal translocations; however, ICS also holds unique potential for novel and innovative approaches to address macular pathology. Using large-animal surgical studies, researchers have explored ICS with the objective of finding safer and more effective techniques to reduce surgical risks such as bleeding, tissue contraction, and scar tissue formation. We explore the relevant anatomy and embryology, existing surgical techniques, discuss the implications for retinal drug delivery, define ICS guiding principles, and offer a rationale for implementation of ICS into a vitreoretinal surgical practice. We also identify other future challenges and anticipate future innovations that will advance ICS.

The structure and function of the human choroid

In this manuscript, the structure of the human choroid is reviewed with emphasis of the macro- and microscopic anatomy including Bruch's membrane, choriocapillaris, Sattler's and Haller's layer, and the suprachoroid. We here discuss the development of the choroid, as well as the question of choroidal lymphatics, and further the neuronal control of this tissue, as well as the pathologic angiogenesis. Wherever possible, functional aspects of the various structures are included and reviewed.

Uveal vascular bed in health and disease: uveal vascular bed anatomy. Paper 1 of 2

The uveal vascular bed is the largest vascular system in the eye and has a role in supplying almost every tissue in the eyeball. This makes it the most important ocular vascular system. This is an up-to-date review of the literature of the entire uveal vascular bed in health based on detailed anatomy of the posterior ciliary arteries (PCAs), anterior ciliary arteries, cilioretinal arteries, and vortex veins. Although postmortem injection cast preparations gave us useful information on the morphology of the choroidal vascular bed; in vivo studies showed that they misled us for centuries about the in vivo situation. According to the postmortem cast studies, the uveal vascular bed has no segmental distribution, the uveal vessels anastomose freely with one another, there are inter-arterial and arteriovenous anastomoses in the choroid, and the choriocapillaris form a freely communicating and an uninterrupted vascular bed in the entire choroid.

VENOUS OVERLOAD CHOROIDOPATHY ASSOCIATED WITH IDIOPATHIC INTRACRANIAL HYPERTENSION

PURPOSE

To report a case of venous overload choroidopathy associated with idiopathic intracranial hypertension in a 41-year-old man.

METHODS

History and clinical examination, fluorescein angiography, ultra-widefield indocyanine green angiography, swept-source optical coherence tomography, and contrast-enhanced magnetic resonance imaging.

RESULTS

The patient was diagnosed as having idiopathic intracranial hypertension 2 years ago, was being managed on oral acetazolamide, and retained 20/20 visual acuity in both eyes until now when he presented with a complaint of visual loss in the right eye. Ophthalmoscopy revealed serous detachment in the fovea of the right eye. Swept-source optical coherence tomography showed the presence of subretinal fluid and detachments of the retinal pigment epithelium in both eyes. Fundus fluorescein angiography showed multiple dot leaks at the level of the retinal pigment epithelium in both eyes. Indocyanine green angiography revealed vortex vein anastomoses and choroidal vascular hyperpermeability in both eyes. Contrast-enhanced magnetic resonance imaging revealed dilated optic nerve sheath diameter and a partial empty sella and magnetic resonance venography showed bilateral stenosis of the transverse sinus.

CONCLUSION

Transverse sinus stenosis is a common finding in "idiopathic" intracranial hypertension and contributes to the intracranial pressure through intracranial venous hypertension. Increased venous back pressure seemed to have overloaded the choroid resulting in choroidal vascular congestion and hyperpermeability, leaks from the level of the retinal pigment epithelium, and accumulation of subretinal fluid.

Choroidal arteriovenous anastomoses: a hypothesis for the pathogenesis of central serous chorioretinopathy and other pachychoroid disease spectrum abnormalities

The pachychoroid disease spectrum (PDS) includes several chorioretinal diseases that share specific choroidal abnormalities. Although their pathophysiological basis is poorly understood, diseases that are part of the PDS have been hypothesized to be the result of venous congestion. Within the PDS, central serous chorioretinopathy is the most common condition associated with vision loss, due to an accumulation of subretinal fluid in the macula. Central serous chorioretinopathy is characterized by distinct risk factors, most notably a high prevalence in males and exposure to corticosteroids. Interestingly, sex differences and corticosteroids are also strongly associated with specific types of arteriovenous anastomoses in the human body, including dural arteriovenous fistula and surgically created arteriovenous shunts. In this manuscript, we assess the potential of such arteriovenous anastomoses in the choroid as a causal mechanism of the PDS. We propose how this may provide a novel unifying concept on the pathophysiological basis of the PDS, and present cases in which this mechanism may play a role.

Concurrence of peripunctal nevus and uveal melanoma with scleral pigment dispersion presenting as phthisis bulbi

This case report demostrates an unusual occurence of peripunctal nevus and uveal melanoma, in which the clinical diganosis of uveal melanoma was masked by the atypical presentation as phthisis bulbi. Nevertheless, peculiar scleral pigment hinted at a possible intraocular tumour. The importance of meticulous clinical examination in assessment of ocular and periocular pigmented lesions is demonstrated. Further, clinicopathological differentials of correlation scleral pigmentation in diffuse necrotic uveal melanoma are illustrated.

Unusual non-nanophthalmic uveal effusion syndrome with histologically normal scleral architecture: a case report

Background

To report an unusual case of non-nanophthalmic uveal effusion syndrome (UES) with histologically normal sclera but responsive to scleral resection.

Case presentation

A73-year-old man presented with a bullous retinal detachment without ciliochoroidal detachment on funduscopic examination of the right eye. The axial length of both eyes was normal. Extensive investigations for possible causes of exudative retinal detachment were performed with unremarkable results except for choroidal hyperpermeability on indocyanine green angiography (ICGA). Ultrasound biomicroscopy (UBM) revealed scleral thickening with peripheral choroidal elevation leading to the diagnosis of UES.

Partial thickness sclerectomy and sclerotomy was performed resulting in complete retinal reattachment, reduction of choroidal hyperpermeability on ICGA and improvement of visual acuity. However, histological studies of the excised sclera revealed no scleral architectural changes or abnormal deposits.

Conclusions

The diagnosis of UES in non-nanophthalmic eyes is challenging. Thorough systemic and ocular investigations are critical to rule out other etiologies. UBM can be helpful to evaluate scleral thickness and anterior choroid in equivocal cases. Our case was unique in that, although the sclera was thick, no abnormal microscopic scleral architecture could be identified. Misdiagnosis may lead to different surgical procedures such as vitrectomy resulting in unfavorable outcomes.

PERIPAPILLARY PACHYCHOROID SYNDROME

PURPOSE

To describe the features of peripapillary pachychoroid syndrome (PPS), a novel pachychoroid disease spectrum (PDS) entity.

METHODS

Medical records of 31 eyes (16 patients) with choroidal thickening associated with intraretinal and/or subretinal fluid in the nasal macula extending from the disk were reviewed (patients with PPS). Choroidal thickness was compared with 2 age-matched cohorts: typical PDS (17 eyes with central serous chorioretinopathy or pachychoroid neovasculopathy) and 19 normal eyes.

RESULTS

The patients with PPS were 81% men aged 71 ± 7 years. Peripapillary pachychoroid syndrome eyes displayed thicker nasal versus temporal macular choroids, unlike PDS eyes with thicker temporal macular choroids (P < 0.0001). Peripapillary intraretinal and/or subretinal fluid was often overlying dilated Haller layer vessels (pachyvessels). Fundus autofluorescence and fluorescein angiography illustrated peripapillary pigmentary mottling without focal leakage. Most PPS eyes (70%) exhibited other PDS findings including serous pigment epithelial detachment or gravitational tracks. Indocyanine green angiography illustrated dilated peripapillary pachyvessels and choroidal hyperpermeability. The disk was usually crowded, with edema noted in 4/31 (13%) eyes and mild late fluorescein disk leakage identified in half of the cases. Choroidal folds (77%), short axial lengths (39% less than 23 mm), and hyperopia (86%) were common.

CONCLUSION

Peripapillary pachychoroid syndrome is a distinct PDS variant, in which peripapillary choroidal thickening is associated with nasal macular intraretinal and/or subretinal fluid and occasional disk edema. Recognition of PPS is important to distinguish it from disorders with overlapping features such as posterior uveitis and neuro-ophthalmologic conditions.

Detection of posterior vortex veins in eyes with pathologic myopia by ultra-widefield indocyanine green angiography

AIMS

To analyse the characteristics of posterior vortex veins detected in highly myopic eyes by wide-field indocyanine green angiography (ICGA).

METHODS

One hundred and fifty-eight consecutive patients (302 eyes) with high myopia (myopic refractive error >8.0 dioptres (D) or axial length ≥26.5 mm) were studied. Wide-field ICGA was performed with the Spectralis HRA module.

RESULTS

Posterior vortex veins were found in 80 eyes (26%). The prevalence of posterior staphyloma was significantly higher in eyes in which posterior vortex vein was detected than in eyes without posterior vortex vein. The posterior vortex veins were classified into five types according to the site of exit from the eye; around the optic nerve in 28%, in the macular area in 17%, along the border of staphyloma in 6%, along the margin of macular atrophy or large peripapillary conus in 21%, and elsewhere in 28%. In one eye, two posterior vortex veins collected the choroidal venous blood from the entire fundus.

CONCLUSIONS

Wide-field ICGA can analyse the characteristic features of choroidal blood outflow system through posterior vortex veins in highly myopic eyes. They may play an important role as routes of choroidal outflow in highly myopic eyes.

Assessment of early-stage optic nerve invasion in retinoblastoma using high-resolution 1.5 Tesla MRI with surface coils: a multicentre, prospective accuracy study with histopathological correlation

OBJECTIVES

To assess the accuracy of high-resolution (HR) magnetic resonance imaging (MRI) in diagnosing early-stage optic nerve (ON) invasion in a retinoblastoma cohort.

METHODS

This IRB-approved, prospective multicenter study included 95 patients (55 boys, 40 girls; mean age, 29 months). 1.5-T MRI was performed using surface coils before enucleation, including spin-echo unenhanced and contrast-enhanced (CE) T1-weighted sequences (slice thickness, 2 mm; pixel size <0.3 × 0.3 mm(2)). Images were read by five neuroradiologists blinded to histopathologic findings. ROC curves were constructed with AUC assessment using a bootstrap method.

RESULTS

Histopathology identified 41 eyes without ON invasion and 25 with prelaminar, 18 with intralaminar and 12 with postlaminar invasion. All but one were postoperatively classified as stage I by the International Retinoblastoma Staging System. The accuracy of CE-T1 sequences in identifying ON invasion was limited (AUC = 0.64; 95 % CI, 0.55 - 0.72) and not confirmed for postlaminar invasion diagnosis (AUC = 0.64; 95 % CI, 0.47 - 0.82); high specificities (range, 0.64 - 1) and negative predictive values (range, 0.81 - 0.97) were confirmed.

CONCLUSION

HR-MRI with surface coils is recommended to appropriately select retinoblastoma patients eligible for primary enucleation without the risk of IRSS stage II but cannot substitute for pathology in differentiating the first degrees of ON invasion.

KEY POINTS

• HR-MRI excludes advanced optic nerve invasion with high negative predictive value. • HR-MRI accurately selects patients eligible for primary enucleation. • Diagnosis of early stages of optic nerve invasion still relies on pathology. • Several physiological MR patterns may mimic optic nerve invasion.

Cellular and physiological mechanisms underlying blood flow regulation in the retina and choroid in health and disease

We review the cellular and physiological mechanisms responsible for the regulation of blood flow in the retina and choroid in health and disease. Due to the intrinsic light sensitivity of the retina and the direct visual accessibility of fundus blood vessels, the eye offers unique opportunities for the non-invasive investigation of mechanisms of blood flow regulation. The ability of the retinal vasculature to regulate its blood flow is contrasted with the far more restricted ability of the choroidal circulation to regulate its blood flow by virtue of the absence of glial cells, the markedly reduced pericyte ensheathment of the choroidal vasculature, and the lack of intermediate filaments in choroidal pericytes. We review the cellular and molecular components of the neurovascular unit in the retina and choroid, techniques for monitoring retinal and choroidal blood flow, responses of the retinal and choroidal circulation to light stimulation, the role of capillaries, astrocytes and pericytes in regulating blood flow, putative signaling mechanisms mediating neurovascular coupling in the retina, and changes that occur in the retinal and choroidal circulation during diabetic retinopathy, age-related macular degeneration, glaucoma, and Alzheimer's disease. We close by discussing issues that remain to be explored.

The retinopial vein: a vein passing directly from the retina to the pia mater at the optic nerve head

BACKGROUND/AIMS

All blood drainage from the retina is thought to occur through the central retinal vein with rare, if any, exceptions. A chance observation of a specimen in which this pattern did not apply suggested that the subject required review.

METHODS

An optic nerve head, identified from an earlier study as possessing an unconventional venous drainage arrangement, was examined histologically using interrupted serial resin sections. 200 fundus photographs were examined to compare with the results from the sectioned optic nerve head.

RESULTS

A retinopial vein passing from the temporal retina and entering the pia mater without first joining the central retinal vein was observed. Two of the fundus photographs and possibly four others displayed a venous pattern consistent with this arrangement.

CONCLUSIONS

The retinopial vein complements the central retinal vein in blood drainage from the retina. Uncertainty in identifying the vein ophthalmoscopically prevents a reliable estimate of its incidence but it appears to be uncommon. Retinal dysfunction may be limited in cases of central retinal vein occlusion in the presence of a retinopial vein.