Best Diagnostic Tools to Uncover Snake-Like Lesion in The Retina

Rohan Mandal, D.Optom.

Fellow Optometrist in Retina and Posterior segment, Dr. Shroffs Charity Eye Hospital, New Delhi, India

 

Choroid is the part of uvea which lies between the retina and sclera. Choroiditis is a type of uveitis which mainly affects the posterior segment of the eye. Most used diagnostic tools are Fundus Fluorescence Angiography (FFA), Optical Coherence Tomography (OCT), Fundus Autofluorescence (FAF), Indocyanine Green Angiography (ICGA), Ultrasonography (USG) etc.

Serpiginous Choroiditis (SC) is a rare type of Choroiditis, mostly affects the middle-aged individuals. ⁽¹⁾ It is usually bilateral, chronic, and progressive choriocapillaropathies mostly characterized by the presence of-white lesions spreading centrifugally from the Peripapillary region. The Retinal Pigment Epithelium (RPE) layer of retina, underneath choriocapillaris and the Choroid is affected. In the year 1932 this disease was first reported by Junius who termed it then as ‘Peripapillary Retinochoroiditis’. After that in 1987 Gass coined this disease as Serpiginous Choroiditis.

The word Serpiginous meaning wavy, snake like lesion, mainly causing posterior Uveitis. Serpiginous Choroiditis basically extending from the juxta papillary area. In this disease greyish yellow colour lesions are seen in the choroid at the margins of healed scars. ⁽²⁾  Serpiginous Choroiditis usually symptomatic, but patients initially may complain of blurring of vision, Central or paracentral scotoma, metamorphopsia and may difficulties in reading or detecting something. After being affected by this disease the patient’s visual acuity typically decreases to 20/40 or less. In worst cases however it may range from 20/20 to finger counting at 1 to 3 feet. In slit lamp examination there must be a shallow interior chamber depth (ACD). There is no effect in intraocular pressure (IOP).

With SC some other ocular complications also can be happened like Choroidal Neovascularization (CNV), which case may occur up to 20 percent of patients, Cystoid Macular Edema (CME), ⁽³⁾ Retinal vein occlusion and Macular Hole.

Figure 1: Colour fundus photograph shows white active lesions

     There are mainly two types of Serpiginous Choroiditis:

1. Classic SC: This is the most common type of SC founds 80 percent of the cases. They are bilateral asymptomatic Serpiginous (Snake like) or geographic yellow-grey like chorioretinal lesions which basically start at the Peripapillary region and can extend up to the macula.
2. Macular SC: This variant involves the macula spreading Peripapillary region. Sometimes we can get confused with geographic atrophy as we can see in macular degeneration and other macular diseases.

To have proper confirmation of the disease and to monitor the progression of the disease, several retinal diagnostic tools are available.

Primarily we used Fundus Autofluorescence (FAF), Fundus Fluorescence Angiography (FFA) and Optical coherence tomography (OCT).

FAF – Using FAF we can easily differentiate the active lesions from inactive. In SC the new active lesions occur at the wavy border of old lesions. In FAF we can easily differentiate into hyper and hypo lesion. Active lesions show hyper autofluorescence, whereas old lesions are hypo autofluorescence In FAF the Red/Green wavelength ultra-widefield imaging method can easily detect them.

Figure 2: In FAF Hyper areas shows show old patches and hypo area show new active lesion

FFA – In FFA the active acute lesions show irregularity, and their borders cannot visible clearly as they appear hypo fluorescence. Occurring because of the blocked fluorescence presents at RPE and outer retina. And after the early phase in the late phase the hyperfluorescent borders are visible. ⁽⁴⁾

Figure 3: In FFA the active lesions border is not clear as the hypo fluorescence

OCT – The active acute lesions mainly affect the outer layer of Retina and choriocapillaris. In OCT we can see that the atrophy of outer layers and disruption of RPE. By using OCT imaging method, we cannot diagnose any active or inactive lesion.

Figure 4: In OCT shows outer retinal layers affected with choriocapillaris

So, these three diagnostic procedures are typically used to diagnose any Retinal disease. In the case of Serpiginous Choroiditis to differentiate it from conventional Choroiditis it is important to identify the pattern of the inflammations.

Throughout we can see that for serpiginous choroiditis to differentiate it and proper diagnosis of the active lesions throughout the retina is important to manage it properly.

Comparing to FFA, FAF can easily detect the activity of the lesion without doing any invasive procedure which clearly shows hyper fluorescence surrounded by old inactive lesion surrounded by hypo fluorescence, also OCT shows only changes in the RPE.

Although every diagnostic tool has its own significance or importance but in the case of serpiginous choroiditis, we can conclude that FAF is a highly beneficial tool for diagnosing the activity of this disease and to plan for further management.

 

References:

1. Lim WK, Buggage RR, Nussenblatt RB. Serpiginous choroiditis. Survey of ophthalmology. 2005 May 1;50(3):231-44.
2. Weiter JJ, Delori FC, Wing GL, Fitch KA. Retinal pigment epithelial lipofuscin and melanin and choroidal melanin in human eyes. Investigative ophthalmology & visual science. 1986 Feb 1;27(2):145-52.
3. El-Asrar AM. Serpiginous (geographical) choroiditis. International ophthalmology clinics. 1995 Apr 1;35(2):87-91.
4. Cardillo Piccolino F, Grosso A, Savini E. Fundus autofluorescence in serpiginous choroiditis. Graefe’s Archive for Clinical and Experimental Ophthalmology. 2009 Feb;247:179-85.

(All photos were collected from Dr. Shroffs Charity Eye Hospital)