Pachychoroid Spectrum

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Original article contributed by: Javier Galván Molina, MD
All contributors: Javier Galván Molina, MD
Assigned editor:
Review: Assigned status Update Pending by Javier Galván Molina, MD on January 14, 2017.


Pachychoroid Spectrum refers to a group of clinical entities that have a common characteristic: a pachychoroid. This term derives from greek παχύ, pachy, thick. It refers to a anatomic choroidal characteristic, in which we found a thick choroid. This could be inferred by some specific and common clinical characteristics between this entities as fundus tessellation, it´s studied and visualized with Enhanced Deep Imaging optical coherence tomography (EDI - OCT) or Swept Source OCT (SS - OCT).

Pachychoroid Spectrum

Choroid Anatomy

First we must understand and define its normal anatomical characteristics. The choroid is responsible for the 1/3 external vascular support of the retina, its functional and structural integrity is essential for retinal function, a compromised volume or flow in its circulation could result in photoreceptor and retinal pigment epitelium (RPE) dysfunction and death. It´s blood supply derives from branches of the anterior and posterior ciliary arteries.

It has a 5 layer histological composition from inner (retinal side) to outer (scleral side):

  1. Bruch Membrane
  2. Ruysch Layer (Choriocapillar)
  3. Sattler Layer (Layer of medium diameter blood vessels)
  4. Haller´s Layer (Layer of large diameter blood vessels)
  5. Suprachoroidea (Transitional zone between choroid and sclera)


The choriocapillaris has large diameter capillaries (20-25 Mm), also it has fenestrations of 700-800 nm diameter, wich allows more rapid transport and of bigger molecules.

Choroid OCT Anatomy

With EDI – OCT and SS OCT, we could define some important anatomical characteristics. Choroid is thickest in subfoveal region, thinner in nasal region and has a progressive thinning through temporal region. It´s defined by different studies that a subfoveal choroidal thickness (SFCT) is approximate 300 microns, and the medium choroidal thickness is approximate 260, but with this we must be carefull cause there could be come variations cause of specific patients characteristics as age, gender, ethnicity and other factors that are equipment dependent and the different anatomical boundaries taken and the specific equipment wich we measure. There is a normal choroidal thickness reduction about 10-15 microns / decade. Among its different choroidal layers we could find a submacular central thickness in Sattler layer 87 +/- 56 microns and Hallers layer of 141 +/- 50 microns.

Disease

Pachychoroid Spectrum refers to a group of clinical entities that have a common characteristic: a pachychoroid. Also share an underlying mechanism. This entities are pachychoroid pigment epitheliopathy, central serous chorioretinopathy, pachycoroid neovasculpathy and polypoidal choroidal vasculopathy. There have been described some other entities that are associated whit a pachychoroid are Vogt-Koyanagi-Harada disease, multiple evanescent white dot syndrome and multifocal choroiditis.

Etiology

In this spectrum are described some specific and common characteristics. Among its common characteristics there are a thick choroid with dilated and hyperpermeable vessels, this will cause focal Bruch membrane and RPE disruption that could lead to serous retinal detachment.

Risk Factors

In its common risk factors are described: Tipe A Personality, emotional stress, pregnancy, tobacco use, corticosteroids, other sympathomimetics.

Specific Pathologies

Pachychoroid Pigment Epitheliopathy

Clinical Findings

Silent Disease. Normal visual acuity. Orange-Redish, absence of fundus tessellation, RPE lessions that could cause drusenoid fundus without subretinal fluid. Also called formae frustrae of central serous chorioretinopathy

Ancillary Testing

OCT: Thick choroid and large choroidal vessels beneath elevations on RPE and sub-RPE drusen like deposits. ICGA (Indocyanine Green Angiography): Choroidal Hyperpermability and hyperpermeability co-existent with areas of RPE change. FAF (Fundus Autofluorescence): Granular and mixed stippled hyper-hypoautofluorescence.

Central Serous Chorioretinopathy

Clinical Findings

It´s commonly presented at 20-50 age, gender male 6:1 female, has an incidence about 5-6/100000, best corrected visual acuity 20/20 – 20/200 with a median 20/30, the characteristic symptom is the presence of metamorphopsia, also could present blurred vision, micropsia, relative scotoma, commonly could solve < 6 months, if this continue its classified as chronic CSC.

Physical Examination

Can present as a bullous, inferior nonrhegmatogenous peripheral retinal detachment, also could find an abscent foveal reflex, yellow-gray elevation and speckled or grouped RPE (this finding may suggest chronicity)

Ancillary Testing

OCT: Pachychoroid + RPE detachment + subretinal fluid. ICGA: Choroidal congestion and hyperpermeability with multifocal hypofluorescent areas. FA (Fluorangiography): RPE detachment with focal leak that ends in pooling in less than a disk diameter from foveal region. FAF: Speckeld Hyperautofluorescence and eventually gravitational zones.

Risk Factors

Type A personality, Emotional stress, Systemic hypertension, Gastroesophageal reflux disease, Pregnancy, Organ transplantation, Systemic lupus erythematosus, Tobacco, Alcohol, Membranoproliferative glomerulonephritis type II, Helicobacter pylori infection, Autoimmune disorders. Medications: Corticosteroids, Psychopharmacologic medications, 3, 4-methlyenedioxymethamphetamine, Antacids and antireflux medications, Over-the-counter sympathomimetics, Antibiotics, Antihistamines, Sidenafl citrate.

Differential Diagnosis

Choroid neovasculopathy, Optic Disc pit, Choroidal polypoidal vaculopathy, choroid melanoma, choroid methastasis, peripheral retinal brake, Choroidal hemangioma, Uveitis, Harada disease, optic neuritis, Papiledema, vitreal traction, Macular hole, Systemic Hipertension.

Treatment

The initial treatment of choice is observation cause the majority of cases solve spontaneously, if fail to improve in 3-6 moths, it shoud be considered treatment with laser photocoagulation (if leakage zone is > 200 microns of foveal region) or photodynamic therapy.

Prognosis

Almost always the patient will have visual acuity 20/40 or above, but could persist metamorphopsia.

Pachycoroid Neovasculpathy/ Polypoidal Choroidal Vasculopaty

Clinical Findings

Blurred vision. (Visual acuity near 20/50). Reduced fundus tessellation without serous retinal detachment.

Ancillary Testing

OCT: Pachychoroid with neovascularization type 1 (sub RPE), large choroidal vessels obblitering choriocapillar and Sattler layaer. Choroidal vessels between Bruch membrane and RPE, also the “double layer sign”. All this changes could progress to polypoidal vascular lesions (Polypoidal Choroidal vasculopathy) ICGA: Choroidal hyperpermeability with hyperfluorescent early dots and vascular network with dilated choroidal vessels. This vessels could progress to polypoidal vasculopaty.

Treatment

It should be considered with anti VEGF and/or photodynamic therapy.


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