A 32-year-old Chinese woman presented to the outpatient department on May 13, 2016 complaining of a 6-month history of progressive blurring of vision in her right eye. She has no past medical history of note, but gave an uncertain history of a foreign body made of iron hitting her right eye 1 year earlier. After being given eyedrops by a doctor at a local hospital, she did not seek further medical care until she noticed further worsening of her vision.
The patient’s visual acuity was 6/20 in the right eye (OD) and 20/20 in the left eye (OS); intraocular pressures were normal (16.9 mmHg OD and 17.2 mmHg OS, by non-contact tonometry). Both pupils were round and there was no relative afferent pupillary defect. Examination of the anterior and posterior segments of the left eye was normal. However, in the right eye, slit-lamp biomicroscopy revealed a corneal macula inferiorly, indicating a possible perforating wound previously. Lens opacification was also observed in the right eye, with clumps of brownish pigment on the anterior lens capsule clinically suggestive of siderotic cataract (Fig. 1). There was no evidence of any breach in the anterior lens capsule. The anterior chamber was clear and of medium depth. As the cataract did not entirely obscured the fundus, it is possible for us to perform the detailed fundus examination with a three-mirror lens, which showed no retinal detachment or signs of foreign body. Using slit-lamp examination and gonioscopy, no intraocular foreign body was visualized in the anterior segment of the injured eye before and after mydriasis. Optical coherence tomography vaguely indicated no retinal detachment in the posterior pole region (Additional file 1: Figure S1). An ultrasound B-scan (10 MHz) showed moderately dense, mobile, vitreous opacities with posterior vitreous detachment and no retinal tear or detachment. No intralenticular foreign body was seen on low gain (Figs. 2a and b). An orbital X-ray (Fig. 2c) and a 3.0-mm thin-sliced computed tomography scan (Fig. 2d) did not show any retained intraocular foreign body.
On the basis of the above findings, the patient was diagnosed with siderotic cataract and underwent an uneventful cataract phacoemulsification with implantation of a posterior chamber intraocular lens (IOL) and capsular tension ring under regional anesthesia in her right eye on May 23, 2016. Dilated fundus examination was also performed intraoperatively to determine if there were any siderotic changes on the retina. However, no retained intraocular foreign body, retinal detachment, retinal tear, or vitreous hemorrhage was seen. The anterior lens capsule was obtained during continuous curvilinear capsulorhexis and sent for histopathology. The patient was treated with Cravit Eye Drops (Alcon Laboratories, Inc., Fort Worth, TX, USA) QID OD, Pred Forte Eye Drops (Allergan Pharmaceuticals, Inc., Dublin, Ireland) QID OD, and Diclofenac Sodium Eye Drops (Shenyang Xingqi Pharmaceutical Co. Ltd, Shenyang, China) QID OD. One week after the surgery, her best uncorrected visual acuity improved to 16/20, and her best corrected visual acuity improved to 20/20 with a corneal macula inferiorly, a clear anterior chamber of medium depth, and a well-centered IOL (Fig. 3).
Electroretinography (ERG) examination performed in the postoperative period revealed the changes characteristic of retinal degeneration with reduced A-wave and B-wave amplitudes (Fig. 4). It also showed implicit time delayed and decreased B:A ratio in both rod and cone system. ERG was normal in the left eye for combined, scotopic, and photopic responses, as well as a normal flicker response. However, these responses were decreased in the right eye.
Histopathologic examination using hematoxylin and eosinstain and special stains like Prussian blue and CD18, a classic macrophage marker, were also conducted. Hematoxylin and eosin staining showed scattered hemosiderin deposits in the anterior capsule (Fig. 5a and b). Prussian blue staining confirmed the presence of iron pigments in the anterior capsule (Fig. 5c and d). The cells in the anterior capsule were strongly stained for macrophages, as indicated in Fig. 5e and f.
During the first 3 months of follow-up at our medical center, the patient was satisfied with the surgical outcomes as she obtained a best uncorrected visual acuity of 12/20 and a best corrected visual acuity of 20/20, with an IOL in situ and a stable retina. Six months after the cataract surgery, her best uncorrected visual acuity was still 12/20 and best corrected visual acuity was 20/20. As computed tomography scan cannot detect this tiny foreign body in our case, we conducted serial follow-up examinations 6 months after surgery, including electrophysiology tests, ultrasound biomicroscopy and detailed fundus examination with a three-mirror lens, to check the presence of any intraocular foreign body in this patient. According to the follow-up tests (Figs. 6, 7, and 8), there was no evidence of intraocular foreign body during 6-month postoperative follow-up. At present we recommended the patient to routinely follow up fundus examination and ERG every 3 months.