Dr Diya Baker1 , Dr Hisham Hamze1 and Dr Abhijit Mohite2
1Birmingham Midland Eye Centre – City Hospital Dudley Road Birmingham West Midlands B18 7QH
2Wolverhampton Eye Infirmary – New Cross Hospital Wolverhampton Road Wolverhampton WV10 0QP
Case Presentation:
An 87-year old African-Caribbean lady presented with a two week history of severe right ocular pain, worse in the evenings. The patient had previously been diagnosed to have asymptomatic iridoschisis in 2007 and attended the diabetic retinopathy screening service annually. There was no known family history of eye disease.
Snellen best corrected visual acuity (BCVA) was 6/12 and 6/9 in the right and left eye, respectively, with intraocular pressures (IOPs) of 18 mmHg and 14 mmHg respectively. Slit-lamp examination revealed shallow anterior chambers (AC) with asymptomatic early cataracts in both eyes and bilateral inferior iridoschisis, more notable in the right eye. Indentation gonioscopy showed ‘occludable’ narrow AC angles with only the non-pigmented trabecular meshwork visible in each eye through more than 180 degrees circumferentially. There were no irido-corneal adhesions or peripheral anterior synechiae present, although inferior angle pigmentation was noted in the right eye.
A clinical diagnosis of appositional primary angle closure suspect (PACS) was provisionally made, with subacute attacks of symptomatic intermittent acute angle closure in the right eye presumed to have been exacerbated by the more marked iridoschisis in this eye. The patient was treated with Neodymium-doped yttrium aluminium garnet (Nd:YAG) laser peripheral iridotomy to the right eye to reduce the future risk of an attack of acute angle closure. Post-procedure topical treatment consisted of dexamethasone 0.1% eye drops every four hours for two weeks. Cataract surgery was offered but this was declined by the patient as she was asymptomatic of visual loss.
At the two-month review IOPs were normal at 16 mmHg in each eye, with no change in BCVA. However repeat gonioscopy revealed persistent occludable AC angles bilaterally, even in the eye with a patent peripheral iridotomy. A subsequent ultrasound biomicroscopy (UBM) scan confirmed marked iridoschisis in the right eye alongside bilateral high iris insertions and anteriorly located ciliary sulci giving steeply rising angles consistent with an underlying plateau iris configuration. The vertical angles were closed in both eyes together with significant irido-trabecular contact in the dark more marked in the right eye. The AC depth, lens thickness (LT) and axial length (AL) in the right eye were measured to be 1.50 mm, 5.10 mm and 21.67 mm respectively, with a high LT: AL ratio of 0.24, confirming a significant phacomorphic component to the angle closure. The AC widths were found to be narrow using anterior segment optical coherent tomography (AS-OCT), measuring 9.7 mm and 10.4 mm in the right and left eyes, respectively.
Despite remaining asymptomatic of angle closure, a routine review three months later revealed localised inferior endothelial decompensation of the right cornea, with Descemet’s membrane folds and iris stromal fibres from the iridoschisis now noted to be in contact with the endothelium. As the BCVA, IOP, and gonioscopy findings remained stable at this point, a watchful waiting approach was adopted.
One month later (6 months post-laser) the BCVA deteriorated to 6/36 in the right eye, with worsening corneal oedema as evidenced by a raised central corneal thickness of 615 microns (compared with 532 microns in the fellow eye), despite a normal IOP of 13 mmHg. The patient was started on hypertonic saline (sodium chloride 5%) and ketoroloac tromethamine 0.5% drops in an attempt to treat the corneal decompensation. However, at the most recent review two years after the laser iridotomy, the BCVA remained poor at 6/36 due to chronic corneal decompensation. Fortunately, the fellow eye continues to maintain good visual acuity with no symptoms of angle closure and the patient has therefore elected not to have any further intervention to her right eye.
Discussion:
Our case highlights the risk of corneal endothelial decompensation following laser peripheral iridotomy in eyes with small anterior chambers and iridoschisis. Iridoschisis has previously been associated with angle closure, and thought to occur in eyes with smaller ALs than angle closure eyes without iridoschisis (Salmon & Murray, 1992). There have been a few previous reports of endothelial decompensation in iridoschisis caused by spontaneous irido-corneal touch. Our patient was therefore at risk of this even without any treatment, although the contralateral eye remained stable with such complications without any treatment. The contralateral eye was at a relatively lower risk of endothelial decompensation given the slightly deeper AC depth, and less pronounced iridoschisis. However, to the best of the authors knowledge, this is the first reported case of endothelial decompensation being exacerbated by laser iridotomy-induced irido-corneal touch in an anatomically small eye with iridoschisis.
The small AC widths in this patient indicate even smaller horizontal corneal diameters in each eye, confirming an underlying diagnosis of microcornea. Rather than an underlying anatomical diagnosis of nanophthalmos, this patient fitted the diagnostic criteria of relative anterior microphthalmos (RAM), given the shallow AC depths (< 2.0 mm in each eye) in the context of ALs greater than 20mm and a normal scleral thickness.
Eyes with RAM have been demonstrated to have higher incidences of angle closure disease. It may be prudent to have a low threshold for early lens extraction surgery in angle closure with an underlying diagnosis of RAM, rather than laser PI, to manage such cases in the future. The co-existence of iridoschisis, as in the reported case, should prompt an earlier consideration for lens extraction surgery as an alternative to LPI in order to manage the angle closure. The authors believe that the risk of corneal endothelial decompensation following LPI in the case reported may have been higher than the risk of potential complications following early lens extraction surgery. Another option may have been to observe the patient without performing any intervention, given the IOP was never measured to be very high. Recent studies have demonstrated a low risk of acute angle closure in asymptomatic PACS eyes over a 5-year period in an oriental population (Jiang et al, 2014). Our case, however, had symptoms of intermittent angle closure attacks and therefore taking such approach may not have been appropriate. The authors of this study have recently reported no significant adverse effect of LPI performed in PACS eyes on the corneal endothelial cell density over six years (Liao et al, 2020), This is in stark contrast to our case or PACS, which suffered chronic corneal endothelial decompensation following LPI due the additional risk factors of iridoschisis and RAM.
Our case therefore highlights the importance of identifying iridoschisis and measuring the AC width (or horizontal corneal diameter) and AL, in eyes presenting with PACS or before considering LPI. As a learning point, LPI should be avoided if there are multiple risk factors for post-LPI corneal decompensation as in this case. We advocate performing specular microscopy to measure endothelial cell density at presentation in such eyes in order to better inform clinical decision-making. Finally, patients should be made aware of these risks when consenting for laser iridotomy in such eyes.
1. Causes, pathophysiology, associations
In this case report we have presented a rare case of bilateral iridoschisis. Iridoschisis is a degenerative pathology of the iris, whereby the anterior iris stroma splits. In 1922 Schmitt et al. first described the manifestation of a “split iris”. which later became known as iridoschisis by Lowenstein et al in 1945. (1,2) This rare condition is as a result of the partial cleavage and hence separation of the anterior layer of the iris stroma from the remainder. This cleaved portion becomes arched, and floats liberally in the aqueous humour. The posterior layer often atrophies, and presents with an appearance described as “shredded wheat” by Lee et al. (3)
Despite over 100 cases reported of iridoschisis in literature there is no one causative agent identified. Lowenstein et al. theorised the potential atrophic effects of lytic substances within the aqueous humour that shears the iris.(4) The lytic substances could be induced by intraocular pressure peaks, trauma, or age. Further theory indicates potentially sclerosis of the blood vessels to the iris cause sphincter tears due to shearing action when pupillary dilation and constriction takes place.(5)
An important facet of iridoschisis is the association with angle-closure glaucoma where over 50% of iridoschisis cases have associated angle closure glaucoma.(6) Other less common associations reported include congenital syphilis, antecedent trauma, congenital abnormalities, keratoconus and nanopthalmos (7).
2. Case-Control, management of cataract, laser peripheral iridotomy (PI) and complications of Laser PI
On consideration of both eyes having iridoschisis manifestations, the management in this case could be equivalated to a case-control study within the patient; whereby intervention of the right eye took place with iridotomy and the left eye remains as the control.This novel case report highlights new challenges to the management of SAACG in patients with iridoschisis. Following the peripheral laser iridotomy, the patient gradually developed corneal decompensation that was not present before. This could have been a direct consequence of the Laser PI or as part of multiple factors that contributed to further endothelial cell damage such as rubbing of the iris on the posterior surface of the cornea and initially having a low endothelial cell count (left eye endothelial cell count was 1469 cell/mm²). Chen et al concluded that patients with concurrent cataracts should receive phacoemulsification as soon as feasible in order to achieve better visual outcomes and reduced complications, which in this case the patient refused. We can report a novel finding in literature for iridoschisis complicated with corneal decompensation and SAACG. This highlights future consideration in the management of iridoschisis with cataracts in order to avoid and prevent possible long-term complications (8.9)
References
1. Schmitt A. Ablosung des vorderen irisblattes. Augenh Klin Mbl. 1922;68:214–215. Loewenstein A, Foster J. Iridoschisis with multiple rupture of stromal threads. Br J Ophthalmol. 1945; 29:277–282
2. Loewenstein A, Foster J. Iridoschisis with multiple rupture of stromal threads. Br J Ophthalmol 1945; 29: 277-282
3. Lee EJ, Lee JH, Hyon JY, Kim MK, Wee WR. A case of cataract surgery without pupillary device in the eye with iridoschisis. Kor J Ophthalmol. 2008;22:58–62. PMID: 18323708.
4. Gogaki E, Tsolaki F, Tigania S, Skatharoudi, C, and Balatsoukas, D. Iridoschisis: case report and review of the literature. Clin Ophthalmol. 2011; 5: 381–384.
5. Albers EC, Klien BA. Iridoschisis: A clinical and histopathologic study. Am J Ophthalmol. 1958;46:794–802
6, Mills PV: Iridoschisis. Br J Ophthalmoll967, 51: 158-64.
7. Duncan EN and Rieser JC: Iridoschisis. Arch Ophthalmol 1976,94: 2004-5.
8. Golan S, Levkovitch-Verbin H, Shemesh G, Kurtz S. Anterior chamber bleeding after laser peripheral iridotomy. JAMA Ophthalmol. 2013;131:626–629.
9. Wang PX, Koh VT, Loon SC. Laser iridotomy and the corneal endothelium: A systemic review. Acta Ophthalmol. 2014;92:604–616.