Electroretinographic assessment of early changes in ocular siderosis

Use of Visual Electrophysiology to Monitor Retinal and Optic Nerve Toxicity of Medications

It is important for clinicians to consider exposure to toxic substances and nutritional deficiencies when diagnosing and managing cases of vision loss. In these cases, physiologic damage can alter the function of key components of the visual pathway before morphologic changes can be detected by traditional imaging methods. Electrophysiologic tests can aid in the early detection of such functional changes to visual pathway components, including the retina or optic nerve. This review provides an overview of various electrophysiologic techniques, including multifocal electroretinogram (mfERG), full-field ERG (ffERG), electrooculogram (EOG), pattern electroretinogram (PERG), and visual evoked potential (VEP) in monitoring the retinal and optic nerve toxicities of alcohol, amiodarone, cefuroxime, cisplatin, deferoxamine, digoxin, ethambutol, hydroxychloroquine, isotretinoin, ocular siderosis, pentosane, PDE5 inhibitors, phenothiazines (chlorpromazine and thioridazine), quinine, tamoxifen, topiramate, vigabatrin, and vitamin A deficiency.

Visual electrophysiology in the assessment of toxicity and deficiency states affecting the visual system

Visual disturbance or visual failure due to toxicity of an ingested substance or a severe nutritional deficiency can present significant challenges for diagnosis and management, for instance, where an adverse reaction to a prescribed medicine is suspected. Objective assessment of visual function is important, particularly where structural changes in the retina or optic nerve have not yet occurred, as there may be a window of opportunity to mitigate or reverse visual loss. This paper reviews a number of clinical presentations where visual electrophysiological assessment has an important role in early diagnosis or management alongside clinical assessment and ocular imaging modalities. We highlight the importance of vitamin A deficiency as an easily detected marker for severe combined micronutrient deficiency.

Correlation Between Electroretinogram and Visual Prognosis in Metallic Intraocular Foreign Body Injury

Purpose: This study aims to investigate the correlation between electroretinogram (ERG) and visual outcome in eyes with metallic intraocular foreign body (IOFB) injury.

Methods: Cases with metallic IOFB injuries with preoperative ERG from January 2008 to May 2020 were reviewed retrospectively. Five ERG responses were recorded, including rod response, maximal response, oscillatory potentials, cone response, and 30-Hz flicker. The results were compared between the affected and the contralateral eyes. All patients received surgery to remove IOFBs. The correlation between amplitudes, implicit times, and grades of ERG with final best-corrected visual acuity (BCVA) was analyzed.

Results: A total of 33 eyes of 33 patients were included. The eyes with IOFB had generally delayed implicit time and reduced amplitude in all waves. The maximum change was found in oscillatory potentials S3 and N1 (0.42 ± 0.42 and 1.95 ± 1.97 of the fellow eyes, respectively, p < 0.05). All amplitudes were negatively correlated with the final BCVA (rs: −0.676 to −0.459, all p < 0.05). In contrast, all implicit times were positively correlated with final BCVA, although, some of them were not statistically significant (rs: 0.035 to 0.687). Among them, oscillatory potential P3 has the highest correlation coefficient (rs = 0.687, p < 0.001). All grades of ERG waves were statistically correlated with the final BCVA (rs: −0.596 to −0.664, all p < 0.001).

Conclusions: ERG can be used to assess visual outcome in metallic IOFB injury after surgery. Oscillatory potentials provided the most significant responses.

Ocular siderosis: a misdiagnosed cause of visual loss due to ferrous intraocular foreign bodies-epidemiology, pathogenesis, clinical signs, imaging and available treatment options

Purpose

The purpose of this paper is to provide a meaningful literature review about the epidemiology, pathogenesis, clinical signs, imaging and treatment of ocular siderosis (OS).

Methods

A computerized search from inception up to March 2020 of the online electronic database PubMed was performed using the following search strings: “ocular siderosis” and “siderosis bulbi”. The reference list in each article was analysed for additional relevant publications.

Results

OS is an uncommon cause of visual loss due to a retained ferrous intraocular foreign body (IOFB). It may develop from 18 days to years after a penetrating trauma that usually occurs during hammering. On average, patients are 22–25 years old, and the vast majority are male. The most common cause of OS development is delayed presentation by the patient or missed diagnosis of IOFB after trauma. The pathophysiology is not fully understood; nevertheless, iron deposition causes hydroxyl radical formation, which damages photoreceptors and retinal pigment epithelium. Moreover, iron damages retinal vessels with consequent inner retinal layers degeneration. The most frequent signs are iris heterochromia, pupillary mydriasis, cataract development and retinal arteriolar narrowing with pigmentary retinal degeneration. Electroretinogram signs, in particular, b-wave amplitude reduction, arise earlier than clinical signs. Orbital CT scans and ultrasonography play an essential role in detecting IOFBs. Treatment depends on the IOFB location and OS development. However, it is crucial to remove the IOFB after OS development because visual acuity and clinical signs may improve. Anterior segment IOFBs can be dislodged using an intraocular magnet (IOM) or forceps through limbal paracentesis. In contrast, posterior segment IOFBs require a pars plana vitrectomy and IOM or forceps to be removed through an enlarged sclerotomy or the limbus.

Conclusion

Recommending the usage of protective glasses and spreading knowledge about OS may further benefit patient care.

Detection and monitoring of subclinical ocular siderosis using multifocal electroretinogram

BACKGROUND

Although full-field electroretinogram (ffERG) is the gold standard test to detect physiological dysfunction in siderosis, it measures overall retinal function. This study aims to determine if multifocal electroretinogram (mfERG) can detect subclinical siderosis in eyes with an iron intraocular foreign body (IOFB).

METHODS

Twenty eyes of 20 patients with retained iron IOFB, clear ocular media and good visual acuity (≥20/120) were enroled in this prospective case-control study. The fellow eyes served as control. These were evaluated with ffERG and mfERG at baseline. Serial mfERG was done till six months after pars plana vitrectomy with IOFB removal. Primary outcomes measures were amplitude and peak time of P1 and N1 wave of mfERG.

RESULTS

The median age was 25 years (range 18-55). Most patients (n = 14/20) presented within a month of trauma. Baseline ffERG showed no difference in either 'a' or 'b' wave amplitude or peak time between cases and controls. However, on mfERG, there was a significant decrease in P1 and N1 wave amplitude and delay in P1 wave peak time in <2° retinal ring in cases as compared to controls (p = 0.001, 0.001 and 0.02 respectively) despite variability in results. At 6 months, P1 amplitude showed significant improvement from baseline in cases (p = 0.010). However, P1 peak time did not show significant recovery (p = 0.65).

CONCLUSIONS

mfERG may reveal subclinical electrophysiological retinal dysfunction in eyes with iron IOFB in cases with normal ffERG. P1 peak time may serve as an electrophysiological marker for past retinal damage.

Siderotic cataract with no signs of intraocular foreign body

BACKGROUND

Ocular siderosis is a clinical condition induced by deposition of an iron-containing intraocular foreign body. We report a unique case of histopathologically proven lens siderosis in a young woman with a preceding history of trauma but no signs of retained intraocular foreign body.

CASE PRESENTATION

A 32-year-old woman presented with an opacified lens showing brownish deposits on the anterior capsule and underwent cataract surgery. Preoperative ophthalmic examination did not show any retained intraocular foreign body. Histopathologic staining of the anterior capsule confirmed the presence of iron deposits and macrophages. Electroretinography examination performed in the postoperative period showed the changes characteristic of retinal degeneration in ocular siderosis.

CONCLUSION

This case illustrates the importance of close monitoring of patients with a history of trauma or previous penetrating injury to the eye, even if there is no intraocular foreign body, because they might develop ocular siderosis at a later stage. This case report underscores the importance of electroretinography and histopathologic analysis, in addition to ophthalmic examination, in the diagnosis of ocular siderosis.

Management of Ocular Siderosis: Visual Outcome and Electroretinographic Changes

Purpose. Ocular siderosis (OS) is a sight threatening complication of retained iron-containing Intraocular Foreign Body (IOFB). Successful localization of the IOFB and timely removal are crucial to its management. The purpose of this study was to review the presentation, management, and outcome of OS at our institution. Methods. A retrospective case series of eyes with OS that underwent IOFB removal from January 2009 to March 2015 at our institution. Results. OS was seen in 9 eyes of 9 patients during the study period. There were 8 males and 1 female with an age range of 31.6 years. An IOFB was in all the eyes. The most common features of siderosis were cataract and pigmentary retinopathy seen in 6 (67%) and 4 (44%) eyes, respectively. Electroretinogram (ERG) readings were reduced in the 9 eyes. The IOFB was removed by pars plana vitrectomy in all the cases with improvement in ERG amplitudes occurring postoperatively in 7 (78%) eyes. Conclusion. A retained iron-containing IOFB can manifest itself after several years with features of OS. A careful clinical and radiologic evaluation is imperative in patients with history suggestive of penetrating ocular injury to rule out retained or occult IOFB and thus prevent this catastrophic condition.

An animal model (guinea pig) of ocular siderosis: histopathology, pharmacology, and electrophysiology

PURPOSE

Ocular siderosis is a rare sight-threatening complication that occurs after a penetrating ocular injury by an iron-containing foreign body. The purposes of this study were to (i) investigate the histopathology, electrophysiology and iron levels/accumulation in ocular siderosis using an animal (Guinea pig) model and (ii) determine the appropriate timing for follow-up foreign body-removal surgery.

MATERIALS AND METHODS

Thirty guinea pigs were divided into five groups (n = 6 animals/group). On day-1, an iron body was inserted into the vitreous of the right eye of all animals; the left eyes were left undisturbed and were used as controls. At the end of each week during the 5-week study period, electroretinography (ERG) was performed on all animals in one of the five groups. Each animal in that group was sacrificed, after which both eyes were enucleated for histopathological and pharmacological evaluation of intraocular iron.

RESULTS

Accumulated iron levels of study eyes were significantly higher than those of control eyes (135.13 and 13.55 μg/g, respectively, p < 0.01). In addition, there was a significant decrease in electrophysiological responses of study eyes. During the first week, iron levels were higher in study eyes than control eyes, but neither histological iron accumulation nor decreased electrophysiological responses could be detected. By the end of the second week, increased iron accumulation was observed histologically in intraocular tissues, along with signs of retinal toxicity, as verified by decreased electrophysiological responses.

CONCLUSIONS

The present study indicates that the 14th day after a penetrating eye injury by an iron-containing intraocular foreign body represents a clinically critical threshold, after which structural damage to and functional alterations in ocular tissues occur.

Application of Prussian blue staining in the diagnosis of ocular siderosis

AIM

To explore the value of Prussian blue staining in the diagnosis of ocular siderosis.

METHODS

Between January 2012 and January 2013, the Prussian blue stain used in anterior lens capsule and vitreous liquid after centrifugation from patients with definitive diagnosis and suspicious diagnosed of ocular siderosis. At the same time, give a negative control.

RESULTS

Anterior lens capsule membrane and liquid of vitreous cavity from patients with definitive diagnosis and suspicious diagnosed of ocular siderosis revealed ferric ions that stained positively with Prussian blue. In the control group, there is no positive reaction.

CONCLUSION

Prussian blue staining in the diagnosis of ocular siderosis has a very significant worth, suspected cases can be definitive diagnosed.

Retinal damages in turner workers of a factory exposed to intraocular foreign bodies

Damages caused by an intraocular foreign body (IOFB) to the visual system, mainly the retina, mostly occur during certain occupational activities. Turners are among the laborers who are mostly exposed to IOFB. The aim of the present work is to survey the effect of an IOFB on the visual system, mainly the retina. Fifty laborers of a turner factory who were exposed to IOFB were selected. Electroretinography (ERG) was recorded in all the laborers. Beside these workers, 50 laborers with no incidence of IOFB were also selected. They were also tested using ERG. The results obtained in the two groups were compared together to search for the possible changes in the two groups. The ERG patterns of the case groups were found to be changed in comparison to the control group. The changes were observed in the area under the b-wave of the ERG pattern in the early stage of damage and in the late stages, the latency and amplitude of the ERG b-wave were also affected. Finally, from the result of the present study, one can conclude that ERG is a suitable technique to search for the retinal changes in the laborers exposed to IOFB.

Removal of large subretinal foreign bodies with bimanual vitrectomy and use of a suture loop

PURPOSE

To describe removal of large subretinal foreign bodies with bimanual pars plana vitrectomy and use of a suture loop.

METHODS

In a retrospective interventional case series, 2 eyes of 2 patients referred 1 month after primary wound suturation, both with posttraumatic retinal detachment and 1 with endophthalmitis, underwent pars plana vitrectomy. Intraocular foreign bodies (IOFBs) were grasped using a 6-0 polypropylene suture loop. The loop was placed around the IOFBs using an intraocular forceps, and the foreign bodies were extracted from the eyes.

RESULTS

A suture loop was placed around the IOFB bimanually, and removal was performed as described. Two large subretinal IOFBs, one metallic and one nonmetallic, were removed successfully without slippage, the first through a limbal incision and the second through an enlarged sclerotomy. The patients were observed for 3 months. One eye had retinal attachment, but the other eye had redetachment that was considered inoperable.

CONCLUSION

Large metallic and nonmetallic subretinal IOFBs of different shapes and sizes can be removed with a suture loop, but in complicated cases, bimanual placement of the loop may provide better control for IOFB removal and the ability to surround the IOFB at its desired axis, thereby decreasing the size of the incision for extraction.

Causes and treatments of traumatic secondary glaucoma

PURPOSE

To study the cause, treatment, and cure of traumatic secondary glaucoma in 103 cases (103 eyes).

METHODS

The records of 103 patients (103 eyes) were reviewed. Causes of the high intraocular pressure (IOP) were analyzed according to the time after trauma. Most patients achieved a better visual acuity and ideal IOP after positive medical, neodymium:Yttrium aluminium garnet (Nd:YAG) laser, or surgical treatment. The operations included anterior chamber irrigation, filtering operation combined with mitomycin C, lensectomy, vitrectomy, and combination surgery.

RESULTS

Clinical findings of secondary glaucoma associated with ocular trauma are complex. Causes resulting in high IOP include intraocular bleeding, lens dislocation, phacoanaphylaxis, angle recession, and siderosis. After medical, laser, or surgical treatment, the IOP of most patients could be ideally controlled. After follow-up for half a year, the IOP of 3 cases (2.91%) was below 10 mmHg and 92 (89.32%) cases between 10 and 21 mmHg; only 8 cases (7.77%) still had IOP over 21 mmHg.

CONCLUSIONS

In traumatic secondary glaucoma, antiglaucoma medication should be used at the early stage, and surgery should be carried out when medical treatment does not reduce the elevated IOP, or in difficult cases to avoid severe complications. The postoperative IOP of most injured eyes was controlled within the safe range.

Siderosis Oculi: Visual Dysfunctions Even After Iron Removal: A Role of OCT

Four males with sidersosis oculi were reviewed. Vitreous/anterior chamber angle irons (cases 1 and 3) were misdiagnosed initially and discovered later. In case 2, the retina-incarcerated iron was long ignored. Exceptionally in case 4, the iron was encapsulated by using optical coherence tomography (OCT). Preoperatively, in cases 1 and 4, the injured eye's vision, electro-oculogram, and electroretinogram were reduced compared with the other eye. In three cases, field defects were relevant to their iron locations. Postremoval, iron-impaired retinal functions didn't obviously improve. Early iron removal seems vital. OCT identified iron encapsulation, ameliorating iron toxicity. Consistently, field defect in case 4 was nonprogressive.

The negative ERG: clinical phenotypes and disease mechanisms of inner retinal dysfunction

Inner retinal dysfunction is encountered in a number of retinal disorders, either inherited or acquired, as a primary or predominant defect. Fundus examination is rarely diagnostic in these disorders, although some show characteristic features, and careful electrophysiological assessment of retinal function is needed for accurate diagnosis. The ERG in inner retinal dysfunction typically shows a negative waveform with a preserved a-wave and a selectively reduced b-wave. Advances in retinal physiology and molecular genetics have led to a greater understanding of the pathogenesis of these disorders. This review summarizes current knowledge on normal retinal physiology, the investigative techniques used and the range of clinical disorders in which there is predominantly inner retinal dysfunction.