Giant pars plana cysts and a diagnostic approach to peripheral retinal elevation with the assistance of multimodal imaging

Abstract

A man in his 50s was referred for a suspected superotemporal retinal tear in the right eye. Fundus examination showed multiple areas of elevated retina temporally in both eyes which were immobile and did not reappose with scleral depression. No retinal breaks were present. Ultra-widefield colour fundus photography with Optos captured these areas of elevated retina in both eyes temporally, which on fundus autofluorescence where hypoautofluorescent with no leading hyperautofluorescent edge. On ultrasound biomicroscopy, an immobile lesion with a single hyperechoic convexity towards the vitreous body was noted. The patient was diagnosed with bilateral giant pars plana cysts which were managed conservatively.

The multimodal imaging in our case is its distinguishing feature which can be used to help ensure accurate diagnosis when one is presented with an area of peripheral retina elevation.

Background

With advances in colour and widefield retinal photography, higher rates of peripheral retinal lesions are being detected by optometrists in the community and referred to ophthalmology. Pars plana cysts are a common incidental finding of the peripheral retina and its differentiation from retinal detachment and retinoschisis are important to ensure an appropriate timely referral, while avoiding unnecessary patient anxiety. Several clinical features on fundus examination, including the use of scleral depression, in addition to retinal photography and ultrasound biomicroscopy can help differentiate these pathologies and avoid unnecessary surgery/complications.

Case presentation

A healthy man in his 50s was referred with a suspected right eye superotemporal horseshoe retinal tear found incidentally on screening. The patient reported no flashes or floaters and had no ocular surgical history. On examination, best-corrected visual acuity measured 6/6 right eye and 6/6 left eye. Anterior chamber examination was unremarkable, and Shafer’s sign was negative. Fundus examination with slit lamp biomicroscopy and indirect ophthalmoscopy with scleral depression showed multiple areas of elevated immobile retina temporally in both eyes (figure 1) with adjacent peripheral cystoid degeneration. No retinal breaks were present.

Figure 1.

Slit lamp biomicroscopy photo on an area of raised retina superotemporal in the right eye.

Investigations

Ultra-widefield colour fundus photography with Optos (California, Nikon, Massachusetts, USA) captured multiple oval areas of raised retina temporally in both eyes which was more easily appreciated on steering. On fundus autofluorescence, these areas were hypoautofluorescent without a leading hyperautofluorescent edge (figure 2). On ultrasound biomicroscopy, an immobile lesion with a single hyperechoic convexity towards the vitreous body was noted (figure 3).

Figure 2.

Optos steering with red and green laser of the right and left eye showed multiple temporal pars plana cysts, respectively. On autofluorescence, the pars plana cysts were hypoautofluorescent.

Figure 3.

Ultrasound biomicroscopy showed an internal wall with a smooth profile and single regular hyperechoic convexity towards the vitreous body representing a giant pars plana cyst.

Differential diagnosis

Differential diagnosis included retinoschisis, giant pars plana cysts, horseshoe tear, rhegmatogenous or exudative retinal detachment and choroidal detachment.

Acquired retinoschisis refers to the splitting of the retinal neurosensory layer and has an incidence rate of 4%–7% in those aged 40 years or over, of which approximately 80% of cases have bilateral involvement.^{1 2} Acquired retinoschisis may be classified as typical or reticular when splitting occurs in the outer plexiform and nerve fibre layer, respectively. Retinoschisis rarely produces symptoms in the absence of retinal detachment and is typically found incidentally. It is commonly located in the inferotemporal quadrant and typically appears as a transparent smooth or bullous elevation of the retina which is relatively immobile and without corrugations. Retinoschisis is usually benign, however, complications include posterior extension, outer retinal wall breaks and in 0.05%–2.2% progression to rhegmatogenous retinal detachments (retinoschisis detachment),^{2 3} during which, outer and inner retinal breaks allow liquified vitreous to enter the subretinal space. On autofluorescence, retinoschisis is typically hypoautofluorescent and usually does not have a leading hyperautofluorescent edge unless progression to a retinoschisis detachment has occurred. Uncomplicated retinoschisis generally warrants non-urgent review in an ophthalmology outpatient clinic for assessment of retinal breaks.

Pars plana cysts are immobile and typically appear as taut, semitransparent/clear bullous elevations of the pars plana region. The contents of cysts secondary to multiple myeloma may appear cloudy. A single oral bay may be occupied by a single/multiple small cysts, while larger cysts may extend to the ora serrata and span across several oral bays.⁴ The term giant pars plana cyst was historically used to describe a cyst that extends to or beyond the equator.⁵ Intraoperative images which illustrated the relationship between pars plana cysts and the ora serrata have been previously published.⁶ On fundus examination, the retinal vessels continue under the cyst instead of inward deflection which is seen in retinoschisis and retinal detachment. Pars plana cysts found on incidental screening warrant a non-urgent referral for outpatient examination for retinal breaks.

A horseshoe or ‘U-shaped’ tear refers to a full thickness retinal break due to vitreoretinal traction, usually secondary to a posterior vitreous detachment or trauma. Risk factors include high myopia, lattice degeneration and previous ocular surgery. Horseshoe tears are commonly located in the superotemporal quadrant at the retinal equator, posterior to the vitreous base. Approximately 15% of people who present to a tertiary ophthalmology service with a symptomatic posterior vitreous detachment will have a retinal break.⁷ Scleral depression can help differentiate a horseshoe tear and an operculum of retinal tissue. A horseshoe tear warrants referral for retinopexy which takes approximately 14 days for scar tissue to develop.

Rhegmatogenous retinal detachments refer to liquified vitreous separating the neurosensory retina and the retinal pigment epithelium via a retinal break. Retinal detachments have an incidence of approximately 1 in 10 000.⁷ Symptoms include new floaters, photopsia and visual field loss (usually progressive). On examination, they usually have a corrugated edge and undulate with eye movements. A rhegmatogenous retinal detachment will reappose on scleral depression unlike pars plana cysts and retinoschisis. Pigmented cells in the anterior vitreous commonly referred to as ‘tobacco dust’ are pathognomonic of a retinal break or rhegmatogenous retinal detachment. On autofluorescence, a rhegmatogenous retinal detachment is hypoautofluorescent with a characteristic leading hyperautofluorescent edge.

An exudative retinal detachment usually occurs when damage to the retinal blood vessels or retinal pigment epithelium allows fluid to accumulate underneath the sensory retina. The prevalence of exudative retinal detachments on initial presentation in patients with uveitis was 1.2% in a retrospective cohort study.⁸ Exudative retinal detachments were commonly found in patients with Vogt-Koyanagi-Harada syndrome and sympathetic ophthalmia, less commonly in panuveitis and posterior scleritis and occasionally in neoplastic disease.⁸ Both anterior chamber cells and vitreous cell activity are clinical signs of inflammation that have a dose–response relationship with exudative retinal detachment prevalence.⁸ Clinically, exudative retinal detachments appear as fluid behind the retina that shifts with gravity and patient position and the retinal contour is smooth. Exudative retinal detachments are generally managed medically.

Choroidal detachments occur secondary to the accumulation of fluid in the suprachoroidal space. They may be classified as serous or haemorrhagic and are commonly secondary to hypotony following glaucoma surgery, however, other causes include trauma and inflammation. Serous choroidal detachments are usually asymptomatic while patients with haemorrhagic choroidal detachments usually report an abrupt onset of severe pain and reduced vision. Clinically, they appear as a dark brown coloured elevation of the retina/choroid which are immobile. The firm attachment of the choroid to the vortex veins is known to limit the extension of a choroidal effusion giving the classical four-lobed appearance. On autofluorescence imaging, they are typically hypoautofluorescent.⁹

Outcome and follow-up

The patient was diagnosed with bilateral giant pars plana cysts secondary to degeneration which was managed conservatively.

Discussion

Ciliary body cysts were first described in 1881 by Kuhnt as a sprout like excrescence sitting on the corpus ciliare extending into the vitreous humour.¹⁰ Nowadays, ciliary body cysts are anatomically categorised into those arising from the ciliary processes or the pars plana retinae.¹¹

The prevalence of pars plana cysts increases with age and has an estimated rate of 24% and 34% in those over the age of 40 and 70 years old, respectively.¹² Pars plana cysts are typically secondary to degeneration and are associated with cystoid degeneration and retinoschisis.^{5 11 13} Rarer causes of pars plana cysts include infection, trauma/globe rupture or multiple myeloma.⁴ On funduscopy, giant pars plana cysts may mimic a retinal break or a rhegmatogenous retinal detachment which was reported in a similar case by Braceros et al.¹⁴ While pars plana cysts are generally benign and of no clinical significance if outside the visual axis, complications include retinal holes, exudate retinal detachment, secondary glaucoma and detachment from the pars plana with suspension of the cyst within the vitreous cavity.¹⁵

Formation of pars plana cysts commonly result from the separation of the non-pigmented ciliary epithelium and pigmented epithelium or less frequently from the coalescence of vacuoles within the non-pigmented epithelium with adjacent cells.¹¹ Histology slides have observed traction from vitreous strands and zonular fibres extending to pars plana cysts.^{4 11} This traction is the most likely mechanism for the formation of pars plana cysts and retinal breaks/detachments,¹¹ and their predominance to be located temporally corresponds with the widest portion and strongest attachment of the vitreous base.

The relationship between pars plana cysts and retinal detachment, however, is a matter of conjecture. While it is generally accepted that pars plana cysts are not directly related to rhegmatogenous retinal detachment, retinal holes have been observed in several large pars plana cysts.^{11 12} Research by Grignolo et al observed interactions between pars plana cysts and a pre-existing retinal detachment in cases of massive vitreous retraction.⁴ During these cases, all partitions between the cysts disappeared, followed by the pigment epithelium detaching from the ora serrata which subsequently created a direct communication between the cystic cavity and an existing retinal detachment.

Ultrasound biomicroscopy of the peripheral retina and ciliary body can assist with accurate diagnosis. Mannion described three patterns of pars plana cysts: (1) isolated cysts, (2) confluent cysts and (3) cluster cysts, which were seen as a smooth single, irregular double and continuous ragged multiple convexities towards the vitreous body, respectively.¹³ Both pars plana cysts and retinoschisis are immobile on imaging, however, unlike pars plana cysts, retinoschisis images as a single thin hyper-reflective layer and may be accompanied with other characteristic findings including retinal layer split, intraretinal pillars and intraretinal cysts.⁶ Retinal detachment typically images as a mobile, bilayered hyper-reflective echo, while a horseshoe tear usually appears as a mobile hyper-reflective flap.¹⁶ Choroidal effusions usually image as a convexed dome shaped elevation of the retina/choroid protruding towards the vitreous cavity and unlike retinal detachments do not remain attached to the edges of the optic disc. Further choroidal effusions usually extend anterior to the ora serrata, unlike retinal detachments which usually remained fixed.

Learning points.

• Areas of peripheral retinal elevation found temporally in both eyes which do not have inward deflection of retinal vessels are clinically suggestive of pars plana cysts.

• Indirect ophthalmoscopy with scleral depression can help differentiate pars plana cysts from retinoschisis, horseshoe tears and retinal detachment and in doing so avoid unnecessary interventions.

• On autofluorescence, rhegmatogenous retinal detachment, retinoschisis and pars plana cysts are hypoautofluorescent, however, a leading hyperautofluorescent edge is characteristic of a rhegmatogenous retinal detachment and retinoschisis detachment.

• When pars plana cysts are found incidentally in a community setting, non-urgent referral for outpatient ophthalmology review is generally sufficient.

Ethics statements

Patient consent for publication

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