Fluctuating hypermetropia due to intraocular lens displacement caused by iris pigment epithelial cyst

Purpose To report a case of hyperopic shift following lens replacement surgery due to an enlarging iris pigment epithelial (IPE) cyst. Observations A gentleman presented with reduced visual acuity (Snellen unaided 20/25) 12 months followed lens replacement surgery. Examination revealed a retro-pupillary iris lesion that appeared to be displacing the posterior chamber intraocular lens (IOL) and was causing a hyperopic shift (refraction +2.00). Anterior segment optical coherence tomography imaging confirmed this to be an IPE cyst with a posteriorly displaced IOL body. After observation over 30 months, the IPE cyst spontaneously reduced in size and the IOL returned to a more physiological position. Unaided visual acuity improved to Snellen 20/16 and refraction improved to +0.50. Conclusions and Importance To our knowledge, an IPE cyst that shows growth following intraocular surgery has not previously been reported. This growth resulted in a hyperopic shift due to posterior displacement of the IOL. This case demonstrates spontaneous regression of the cyst, and suggests that over time these cysts can change in size.


Introduction
Primary iris pigment epithelial (IPE) cysts commonly are asymptomatic and are stationary or very slow-growing. 1Secondary iris cysts are less common but are more prone to causing complications including reduced vision, glaucoma and uveitis. 2 We report a unique case of a gentleman who presented with posterior intraocular lens (IOL) displacement due to a large IPE cyst behind the iris.

Case report
A 66-year-old male presented to the outpatient department due to blurred vision in his left eye following lens replacement surgery with a standard monofocal intraocular lens.He had a past ocular history of bilateral LASIK (laser-assisted in situ keratomileusis) for hypermetropia and more recent bilateral lens replacement surgery.On examination, the Snellen unaided visual acuity was 20/20 and 20/40, respectively on the right and left eyes.Left eye vision improved to 20/20 with pinhole.Autorefraction was +0.25/-1.00× 35 on the right eye and +2.00/0.00× 180 on the left eye.Intraocular pressures were normal in both eyes.The right eye anterior and posterior examination was unremarkable.
However, the left examination revealed a clear cornea, quiet anterior chamber with a retro-pupillary iris mass lesion from 2 to 9 o clock (Fig. 1 A, B and C).Posterior segment examination of the left eye was normal.
High-resolution anterior segment optical coherent tomography (AS-OCT) imaging of the left eye further demonstrated this lesion.It measured 1.78mm in thickness with internal lucency and was seen protruding from the posterior iris and causing posterior displacement of the posterior chamber IOL (Fig. 2).
A diagnosis of left midzonal IPE cyst was made.This was causing a hyperopic shift from posterior displacement of the posterior chamber IOL.On further questioning, the patient did recollect being told at the time of his left lens replacement surgery that there was a small iris cyst, but this did not affect surgery in any way.
With regards to treatment options, the patient enquired about further laser refractive surgery to correct the hypermetropia.Due to the seemingly sudden increase in size of the iris cysts post lens replacement surgery, we recommended spectacle/contact lens to correct the hypermetropia in the first instance and arranged a further review in the clinic to monitor the cyst.
Four months later, the patient attended for a follow-up appointment.Unaided vision in the left eye had spontaneously improved to Snellen 20/25 and refraction had improved to +1.25/0.00× 180.On examination, the left iris pigment epithelial cyst had become visibly smaller.As the cyst had become spontaneously smaller and unaided vision and refraction had improved, we decided on surveillance monitoring over any intervention to remove the cyst.
The patient was reviewed again twelve months following the initial presentation.The iris cyst had decreased in size.Vision in the left eye had further improved to Snellen 20/16 unaided and refraction had improved to +0.75/-0.50× 144.
Humphrey visual fields remained full in both eyes with normal intraocular pressures and healthy optic nerves.Over 2.5 years later following initial presentation, his visual acuity remains Snellen 20/16 unaided with plano refraction.

Discussion
Iris cysts are uncommon and can be classified as primary or secondary according to aetiology, and then further divided into subgroups based on their tissue or origin, with primary IPE cysts representing 86 % of all iris cysts. 4rimary IPE cysts are thought to be remnants of the marginal sinus that have not been obliterated and represent developmental anomalies resulting from the cystic expansion of the potential space between the pigmental epithelial layers of the posterior iris. 3Histopathology of primary IPE cysts is composed of nonkeratinized squamous epithelial-lined structures that arise from the posterior iris layer. 5rimary IPE cysts are usually an incidental finding.Primary IPE cysts can be classified based on their location: pupillary, midzone, peripheral and free-floating/dislodged. 6 In terms of incidence, peripheral IPE cysts are most common (64 %), followed by midzone (28 %), pupillary (7 %) and dislodged (1 %). 7he clinical course of primary IPE cysts is dependent on their location. 1Peripheral, midzone and dislodged IPE cysts tend to remain stable, regress in size or completely resolve.However, pupillary IPE cysts are more likely to enlarge over time (84 %), with the remainder tending to remain stable in size (8 %) or completely resolve (8 %). 7Interestingly,  our patient had a midzone IPE cyst that did show initial enlargement, followed by regression.
Despite this, in the largest primary IPE surveillance study conducted, no complications were detected with pupillary IPE cysts. 7Instead, complications were more seen with midzone and peripheral IPE cysts and these included corneal touch, focal cataract, lens subluxation, iritis and glaucoma. 7maging modalities such as ultrasound biomicroscopy and AS-OCT are essential in differentiating iris cysts from ocular tumours.IPE cysts appear as thin-walled and homogeneous lesions with hypoechoic internal content and regular borders on UBM and AS-OCT, 8 whilst tumours present with a solid inner structure 9 and show increase in lesion size. 10Based on the history, examination and AS-OCT, our patient had a left midzonal primary IPE cyst.
It seems that there was transient enlargement of the IPE cyst in our patient following lens replacement surgery, and this caused the IOL body to displace posteriorly and produce a hyperopic shift (he was emmetropic after his lens extraction).The lack of astigmatism change is somewhat peculiar as the asymmetrical pressure on the IOL body from the transient IPE cyst enlargement would be expected to produce some change in astigmatism.On examination, the IOL was well-centred.There was evidence of posterior displacement, but no evidence of decentration or tilt.This would explain the change in spherical refractive error, but no induction of cylindrical error.
There is clear evidence that trauma, 2 inflammation 1 and even certain glaucoma medication such as latanoprost 11 can stimulate the formation of secondary iris cysts.However, the possible pathogenic mechanism underlying enlargement of primary IPE cysts is still unclear and there are no reports of enlargement/reduction in size of primary IPE cysts being linked to intraocular surgery. 12Furthermore, the two largest IPE surveillance studies 7,8 did not identify intraocular surgery as a risk factor for cyst enlargement.][15] There is very limited literature to show that primary iris cysts have any effect on posterior chamber "in-the-bag" IOLs as our case showed.However, there is some data on how iris cysts affect the position of implantable collamer lenses (ICLs).One study reported a case series of 218 eyes with iris cysts and found no abnormal effects on ICL position, vault or astigmatism over 12 months. 16Another study showed no difference in the ICL position, central vault of ICL and refractive error following ICL implantation between eyes with and without primary iris cysts. 17Similar to what occurred in our case, both these studies found that most cysts regress in size or resolve within 12 months of ICL surgery.In our patient, the IPE cyst spontaneously decreased in size, allowing the IOL to return to a more physiological position, thus reducing the hypermetropic refractive error and improving the unaided distance visual acuity over the 2.5 year period.
Our case report suggests that refractive surgery would not be a suitable option because of the changing iris cyst size.Non-permanent methods such as spectacles or contact lenses may be preferred.If a more permanent treatment is sought, then treatment of the IPE cyst rather than refractive surgery may be advisable.

Conclusion
We report a case of a patient who developed a hyperopic shift following lens replacement surgery due to an IPE cyst.The IPE cyst caused a hyperopic shift due to a substantial increase in size (following lens replacement surgery) that led to displacement of the IOL posteriorly.Over the following months and years, the iris cyst shrunk spontaneously and the unaided visual acuity and refraction improved without any intervention.

Patient consent
Consent to publish the care report was obtained.This report does not contain any personal information that could lead to the identification of the patient.

Fig. 1 .
Fig. 1. (A): Slit lamp photograph (low magnification) of the left eye showing a retro-pupillary iris lesion through dilated pupil.(B): Slit lamp photograph (high magnification) of same lesion through dilated pupil (C): Slit lamp photograph showing iris lesion protruding posterior to pupillary plane.

Fig. 2 .
Fig. 2. Anterior segment optical coherence tomography images of the left eye showing a typical retro-pupillary iris cyst (1.78mm thickness).