Photopsia as a manifestation of digitalis toxicity

Spectrum of digoxin-induced ocular toxicity: a case report and literature review

Background

Digoxin intoxication results in predominantly digestive, cardiac and neurological symptoms. This case is outstanding in that the intoxication occurred in a nonagenarian and induced severe, extensively documented visual symptoms as well as dysphagia and proprioceptive illusions. Moreover, it went undiagnosed for a whole month despite close medical follow-up, illustrating the difficulty in recognizing drug-induced effects in a polymorbid patient.

Case presentation

Digoxin 0.25 mg qd for atrial fibrillation was prescribed to a 91-year-old woman with an estimated creatinine clearance of 18 ml/min. Over the following 2–3 weeks she developed nausea, vomiting and dysphagia, snowy and blurry vision, photopsia, dyschromatopsia, aggravated pre-existing formed visual hallucinations and proprioceptive illusions. She saw her family doctor twice and visited the eye clinic once until, 1 month after starting digoxin, she was admitted to the emergency room. Intoxication was confirmed by a serum digoxin level of 5.7 ng/ml (reference range 0.8–2 ng/ml). After stopping digoxin, general symptoms resolved in a few days, but visual complaints persisted. Examination by the ophthalmologist revealed decreased visual acuity in both eyes, 4/10 in the right eye (OD) and 5/10 in the left eye (OS), decreased color vision as demonstrated by a score of 1/13 in both eyes (OU) on Ishihara pseudoisochromatic plates, OS cataract, and dry age-related macular degeneration (ARMD). Computerized static perimetry showed non-specific diffuse alterations suggestive of either bilateral retinopathy or optic neuropathy. Full-field electroretinography (ERG) disclosed moderate diffuse rod and cone dysfunction and multifocal ERG revealed central loss of function OU. Visual symptoms progressively improved over the next 2 months, but multifocal ERG did not. The patient was finally discharged home after a 5 week hospital stay.

Conclusion

This case is a reminder of a complication of digoxin treatment to be considered by any treating physician. If digoxin is prescribed in a vulnerable patient, close monitoring is mandatory. In general, when facing a new health problem in a polymorbid patient, it is crucial to elicit a complete history, with all recent drug changes and detailed complaints, and to include a drug adverse reaction in the differential diagnosis.

fMRI of retina-originated phosphenes experienced by patients with Leber congenital amaurosis

A phenomenon characterized by the experience of seeing light without any light actually entering the eye is called phosphenes or photopsias. Phosphenes can occur spontaneously or via induction by external stimuli. Previous reports regarding phosphenes have primarily focused on externally induced phosphenes such as by applying alternating or direct current to the cortex. A few of these reports used functional magnetic resonance (fMRI) to study activations induced by cortical phosphenes. However, there are no fMRI reports on spontaneous phosphenes originating from the retina and the resulting pattern of cortical activations. We performed fMRI during a reversing checkerboard paradigm in three LCA patients who underwent unilateral gene therapy and reported experiencing frequent phosphene on a daily basis. We observed bilateral cortical activation covering the entire visual cortices when patients reported experiencing phosphenes. In contrast, in the absence of phosphenes, activation was regulated by patient's visual ability and demonstrated improved cortical activation due to gene therapy. These fMRI results illustrate the potential impact of phosphene perception on visual function and they may explain some of the variability that clinicians find in visual function testing in retinal degeneration. Although we did not perform correlations between visual function and phosphenes, we hope data presented here raises awareness of this phenomenon and its potential effect on visual function and the implications for clinical testing. We recommend a thorough history for phosphene experiences be taken in patients with retinal disease who are candidates for gene or molecular therapy. Lastly, these data illustrate the potential power of fMRI as an outcome measure of gene therapy and the negative impact phosphenes may have on vision testing. fMRI has proven to be a sensitive, non-invasive, and reproducible test paradigm for these purposes and can complement standard visual function testing.

Iatrogenic neurology

Iatrogenic disease is one of the most frequent causes of hospital admissions and constitutes a growing public health problem. The most common type of iatrogenic neurologic disease is pharmacologic, and the central and peripheral nervous systems are particularly vulnerable. Despite this, iatrogenic disease is generally overlooked as a differential diagnosis among neurologic patients. The clinical picture of pharmacologically mediated iatrogenic neurologic disease can range from mild to fatal. Common and uncommon forms of drug toxicity are comprehensively addressed in this chapter. While the majority of neurologic adverse effects are listed and referenced in the tables, the most relevant issues are further discussed in the text.

Flashes, floaters and fuzz

Flashing lights (photopsia) and floaters are common visual phenomena and patients frequently present to hospital with these symptoms. This article provides a guide for the non-specialist to the different pathologies that may result in photopsia and floaters.

Clinical manifestations of elderly patients with digitalis intoxication in the emergency department

This study aimed to determine the clinical characteristics of elderly patients diagnosed with digitalis intoxication, on the Emergency Department, University Hospital Complex, A Coruña, Spain. During the study period (January-September 2008) cases were included in which digitalis intoxication was confirmed by plasma digoxin levels. We collected data on age, gender, base-line diseases, therapeutic indications for digoxin, functional classification, ejection fraction, plasma digoxin levels, creatinine clearance, ions, gasometry, electrocardiogram, concomitant medication, symptomatology and treatment. The results were: mean age 82.0 ± 6.6 years, predominantly female subjects (83.7%). The most prevalent pathologies were cardiac valvulopathy (81.0%), hypertension (68.3%) and ischemic cardiopathy (46.3%), 95.1% had a background of cardiac insufficiency, and 52.6% were in functional grade III. The mean digoxin level was 2.7 ± 0.69 ng/ml, 23.1% of the patients had a creatinine clearance of less than 60 ml/min/1.73 m(2) and 2.6% had a severely reduced glomerular filtration rate (GFR) (clearance<30 ml/min/1.73 m(2)). A negative correlation was found between digoxin levels and clearance (r = -0.22; p = 0.18) and between the levels and cardiac frequency (r = -0.35; p = 0.026). Of the patients, 47.5% presented bradycardia and 87.8% arrhythmias, most frequently auricular fibrillation. The most frequent symptoms were nausea (54.8%), fatigue (42.9%), vomiting (33.3%) and anorexia (28.6%). We conclude that clinical digestive symptoms in elderly women who are taking digitalis, with bradycardia and impaired renal functioning, should lead us to suspect digitalis intoxication.

A survey of photopsias in self-reported retinitis pigmentosa: location of photopsias is related to disease severity

PURPOSE

To characterize photopsias or light shows in patients self-reporting retinitis pigmentosa and determine associations between their location and patient-reported visual function.

METHODS

One hundred and twenty-seven self-reported patients with retinitis pigmentosa with varying levels of vision completed an anonymous survey on an Internet web site.

RESULTS

One hundred and eighteen (93%) of the respondents reported photopsias. The majority (60%) who experience photopsias have them daily, 48% already had them before being diagnosed with retinitis pigmentosa, and 69% report interference with vision. The proportions noting photopsias mostly peripherally versus centrally were 53% of those reading normal or small print versus 35% requiring magnification (odds ratio, 2.3; 95% confidence interval, 1.0-5.5; P = 0.05); 61% of current drivers versus 41% who stopped or never drove (odds ratio, 2.6; 95% confidence interval, 1.0-6.7; P = 0.04); and 54% of individuals who easily navigate or have only minor difficulty in unfamiliar areas versus 29% of those with great difficulty or needing assistance with mobility (odds ratio, 3.0; 95% confidence interval, 1.2-6.7; P = 0.02).

CONCLUSION

Contrary to common belief that photopsias are associated with end-stage retinal degeneration, they are also commonly reported in earlier stages. The location of photopsias appears to be related to residual photoreceptor function assessed by self-reported performance of daily activities. Clinicians and researchers should be aware of their frequent occurrence and offer reassurance to patients.