Main

Sir,

Retained intraocular foreign bodies (RIOFB) represent a subset of ocular injuries that present complex surgical challenges to remove them successfully while attempting to preserve vision as well as the ocular architecture.1

Imaging modalities available to detect RIOFB include plain film X-rays, contact B-scan ultrasonography, CT scan, and MRI scanning.2 This is the first report to the best of our knowledge describing the optical coherence tomography (OCT) findings for assessment of the depth of RIOFB on or within retina and associated macular status that may prognosticate the management.

Case report

A 30-year-old male presented with a history of injury to the right eye while hammering metal on metal 20 days back followed by a diminution of vision. On examination, he had a self-sealed corneal perforation at the 6 o'clock limbal border. Anterior chamber depth was normal, lens was clear and no relative afferent pupillary defect was present. After full dilation, fundus evaluation revealed a clear media with no vitreous haemorrhage or retinal detachment. A yellowish white glistening foreign body 2 mm × 5 mm was visualized about four disc diameters superotemporal to the macula embedded on the retina, with surrounding rusty pigmentation (Figure 1a). The best-corrected visual acuity in the affected eye was 20/30, applanation intraocular pressure was 14 mmHg, and the full-field electroretinography b-wave amplitude was slightly delayed (34 μV in right eye, 40 μV in left eye). Ultrasonography longitudinal B-scan showed RIOFB partly buried in the retina temporal to the disc (Figure 1b). OCT high-resolution scan (Stratus OCT Model 3000, Zeiss Humphrey, Dublin, CA, USA) was performed and showed an area of high reflectivity with marked posterior shadowing in the region corresponding to the foreign body (Figure 2). Attachment to RIOFB of highly reflective membranes that may correspond to posterior hyaloid face was also seen. Macular thickness map scan and retinal map analysis protocol showed increased thickness in the centre and the inner macular quadrants in the right eye. The central foveal thickness was 218 μm in the right eye and 183 μm in the left eye.

Figure 1
figure 1

(a) Fundus photograph showing the retained intraocular foreign body superotemporal to the macula. (b) Ultrasonography longitudinal B-scan depicting the foreign body buried in the retina (arrow).

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Figure 2
figure 2

Optical coherence tomography showing area of high reflectivity with marked posterior shadowing in the region corresponding to the foreign body.

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After informed consent, the patient underwent uneventful pars plana vitrectomy. A microvitreoretinal blade was used to free the RIOFB at the superior surface and the foreign body was removed completely with an intraocular magnet. Postoperative tamponade was given with C3F8 gas injection followed by prone positioning. At 6 weeks follow-up, the patient had a stabilized best-corrected visual acuity of 20/30 and attached retina. OCT revealed central foveal thickness of 190 μm in the right eye and 183 μm in the left eye with reduction in macular oedema and full-field electroretinography b-wave amplitude was slightly delayed (34 μV in the right eye, 40 μV in the left eye).

Comment

OCT is a useful diagnostic tool for performing high-resolution cross-sectional imaging of the retina in macular diseases including macular oedema, macular holes, detachments of the neurosensory retina, and pigment epithelium along with nerve fibre layer defects in glaucoma.3, 4 Besides initial visual acuity that is the most important predictive factor of visual outcome in patients with RIOFB,1 assessment of the macular thickness on OCT may play an important role in predicting the postoperative visual outcome after RIOFB removal. Along with the depth of the RIOFB, OCT detected mild macular oedema preoperatively in this case, which may have accounted for a low visual acuity of 20/30, hence may prognosticate the visual potential. Radiological assessment of RIOFB with plain film X-rays, contact B-scan ultrasonography, CT scan, and MRI scanning are usually used in cases where the ocular media is opaque or physical examination is inconclusive.2 Ultrasonography is more useful for localizing foreign bodies relative to the ocular coats than CTscan,5, 6 but is operator dependent7 and MRI is avoided in cases of magnetic RIOFB.2 Therefore, besides a direct visualization of RIOFB in clear media with ophthalmoscopy and slit-lamp biomicroscopy, OCT may emerge as a new modality for accurate localization of the depth of the foreign body on or within the retina, scanning the retina surrounding the RIOFB to assess consequent changes and postoperative assessment of the macula. However, OCT is operator dependent with a learning curve, with limited assessment of highly reflective foreign bodies due to back shadowing, allowing scanning only a limited area in the posterior pole near or within the retina. A study of varied RIOFB presentations will further clarify the role of OCT in such cases.