Category: Ophthalmology

It’s a Stroke – of the Eye?

As we are well aware, a brain globally deprived of oxygen, for even the briefest moments, suffers irreversible damage. Cerebrovascular events, those depriving a smaller distribution of the brain of oxygen, do so likewise – excepting the potential for recovery provided by the so-called “ischemic penumbra”. There is great heterogeneity between stroke syndromes and potential for recovery, but perfusion- and tissue-based treatments quite clearly demonstrate some protective effect of collateral circulation.

Does the eye work like that? That is the working theory – or, at least, working wishes and hopes of the neurology and neuro-ophthalmology community.

There is typically only one blood vessel supplying the inner retina – the central retinal artery. If this vessel becomes occluded, widespread ischemia is inevitable. The outer retina is supplied by the choriocapilaris, derived from separate branches of the ophthalmic artery. A further, non-trivial percentage of individuals have a cilioretinal artery, supplying a part of the macula. These other vessels may provide some additional perfusion to parts of the eye, with intact survival approaching 90 minutes in animal studies. Widespread, irreversible damage seems complete by four hours.

So, is there a window of opportunity for early thrombolysis? The American Heart Association thinks so: “The current literature suggests that treatment with intravenous tissue plasminogen activator may be effective.”

This “current literature” of which they speak is primarily a citation from last year’s Stroke, a single-center cohort study and updated patient-level meta-analysis. In the “cohort” portion, this site treated 16 patients with CRAO with alteplase within 4.5 hours, and compared them with 87 others who received “Standard of Care”. Patients in this treatment cohort did better than those who were not – hardly surprising, considering those treated had fewer signs of damage to the retina on initial fundoscopic examination.

The “patient-level meta-analysis” includes 238 patients from studies dating back to the 1980s. The 9 patients for whom treatment was provided within 90 minutes displayed better outcomes than those treated in later time windows, as well as those patients whose outcomes describe the “natural history” of the disease. The guideline authors’ interpretation of these data: “An updated meta-analysis including these modern cohorts again demonstrated a strong effect with treatment within 4.5 hours.”

Little heed is paid to the 5 patients within their meta-analysis reported as having intracranial hemorrhage, 1 with angioedema, and 1 with extracranial hemorrhage.

CRAO is devastating, and there is no known effective treatment. Thrombolysis may be beneficial, but treatment is associated with well-established harms. Along with all the stroke mimics and low-NIHSS patients currently being treated, it’s not surprising these authors contort themselves into recommendations overstating the strength of the evidence. Clinical trials are underway – wait and see.

“Management of Central Retinal Artery Occlusion”
https://www.ahajournals.org/doi/pdf/10.1161/STR.0000000000000366

“Intravenous Fibrinolysis for Central Retinal Artery Occlusion”
https://www.ahajournals.org/doi/10.1161/STROKEAHA.119.028743

Counterpoint: Topical Anesthetics for Corneal Abrasions

We’ve seen a few articles recently discussing the potential utility of topical anesthetics for analgesia for corneal abrasions. The general point: there’s no consistent, modern evidence of harm, so why should we cling to older ways?

Counterpoint from the corneal specialist community: cling to old ways.

In this long correspondence, the authors detail the physiologic basis for their opposition to topical anesthetics as it relates to stimulation of endothelial growth. They follow this up with a three question survey regarding the practice, distributed to “an international community of cornea trained specialists”.

The clear winner in each of their three questions: “strongly disagree” with provision of topical anesthetics for acute corneal abrasions.

Interestingly, they also conflate these results with lack of justification for a clinical trial to further explore the safety and efficacy of such use:

“Often when there is a difference in clinical practice or clinical equipoise, there is an opportunity for a clinical trial. However, it is our hypothesis that within the ophthalmology community, there is not equipoise with respect to our practice of not prescribing topical anesthetics after traumatic corneal abrasions.”

I think it’s clear these specialists are making valid points regarding the potential for topical anesthetic abuse, but their citations hardly support their practice stance. I do agree, at least, regarding the lack of utility of clinical trials – but not because their use is so dangerous it cannot be tested. Rather, any clinical trial simply would be of low value as adverse events would be so rare it would be unlikely to reliably detect a difference between management strategies. It is clear topical anesthetic use will not be safe in all clinical situations, but it is rather more appropriate to provide guidance on the proper use of topic anesthetics than to simply ban them completely while continuing to cite the same anachronistic, limited evidence.

“Cornea Specialists Do Not Recommend Routine Usage of Topical Anesthetics for Corneal Abrasions”
https://www.ncbi.nlm.nih.gov/pubmed/31445551

Just Use the Slit Lamp

One is an unwieldy, medieval torture device. The other is a magnifying glass attached to a purple flashlight. In a busy Emergency Department, adapting to space requirements and patient flow needs, which one are you going to reach for?

Unfortunately – and rather obviously – the easy option is not equally effective. This small study pulled a convenience sample of anterior chamber-type eye complaints presenting to an eye urgent clinic, and evaluated them first with the Wood’s lamp, and then the slit lamp. Of the 73 patients included in the study, the overall sensitivity of the Wood’s lamp was 52% – missing, as the sensitivity might imply, about half of corneal abrasions, half of corneal ulcers, half of corneal foreign bodies, and most all of the keratitis or rust rings. Most of the provisional diagnoses given with the Wood’s lamp examination were different enough from the final diagnoses that the misses were clinically important.

Take a few minutes to re-familiarize yourself with the dials and widgets on your slit lamp – and use it. These data are hardly conclusive the slit lamp is, in fact, a “gold standard”, or that the Wood’s lamp is non-inferior in a general ED setting when used by emergency physicians. However, I’d rather put the onus on the evidence to demonstrate the effectiveness of the less-intensive diagnostic method, rather than base my practice on the assumption.

“Prospective study of the sensitivity of the Wood’s lamp for common eye abnormalities”
https://www.ncbi.nlm.nih.gov/pubmed/30630841

Bonus link: “What Really Glows” with the Wood’s lamp.

Conjunctivitis: No Antibiotics, Please!

It’s the sad state of modern medicine – choose a common ambulatory condition, and you can find widespread avoidable overuse and waste. There is a spectrum of acceptability to this practice variation, of course, depending on the severity of consequences for missed or delayed diagnoses – but, for the most part, we’re just setting our professional respectability aflame.

This is a simple retrospective review of prescriptions associated with diagnoses of acute conjunctivitis. These authors reviewed records from a large managed care network and identified 340,372 patients with a clinical visit coded for acute conjunctivitis. Within 14 days of this visit, 58% of patients filled prescriptions for topical ophthalmologic medications. Considering most conjunctivitis encountered in the clinical setting is viral or allergic, obviously, the vast majority of these are wholly unnecessary. Then, frankly, while topical antibiotics mildly hasten the improvement of bacterial conjunctivitis, it is still a generally self-limited condition.

Ophthalmologists and optometrist visits were the least likely to have an antibiotic prescription associated with a visit for acute conjunctivitis, but 36% and 44%, respectively. Urgent Care Physicians and “Other Provider” – probably inclusive of Emergency Medicine – were at 68% and 64%, respectively. Fluoroquinolones accounted for 33% of antibiotic prescriptions – which is fabulous, because they are typically the most costly, and result in both increased risk for antimicrobial resistance and S. aureus endophthalmitis. Then, one in five prescriptions were for combination corticosteroid-antibiotic combination products – which are contraindicated, as they can prolong viral infections or worsen an underlying herpes simplex infection.

The American Academy of Ophthalmology contribution to Choosing Wisely recommends avoiding antibiotic prescriptions for viral conjunctivitis, and deferring immediate antibiotic therapy when the cause of conjunctivitis is unknown. Stop the madness! Everyone!

“Antibiotic Prescription Fills for Acute Conjunctivitis among Enrollees in a Large United States Managed Care Network”

https://www.ncbi.nlm.nih.gov/pubmed/28624168

Retinal Photography to Diagnose TIAs?

Our diagnostic approach to suspected cerebrovascular disease is quite simple.  Concerning neurologic findings or history?  Magnetic resonance imaging.

However, this approach is grossly inefficient – and, thus, the rise of various clinical scores such as the ABCD2 variants.  And, now, ocular fundus photography.  It generally makes sense – the retinal vessels travel through the optic nerve sheath.  They are, then, a unique window into the cerebrovascular circulation – and, accordingly, the degenerative diseases within.

It sort of works.

Looking at patients presenting to the ED with a report of focal neurologic deficits, the multivariate regression OR for cerebrovascular disease in patients with arterial narrowing in 2 segments is reported as 8.1 for stroke and 5.1 for TIA.  However, this finding was only present in 4 of 22 (18%) stroke patients and 6 of 59 (10%) TIA patients – compared with 5 of 176 (3%) patients who did not receive a diagnosis of cerebrovascular disease.

So, yes – it is probably true, as the authors claim, that finding arterial focal narrowing in the retinal vessels increases the likelihood of cerebrovascular disease (stroke and TIA).  But, clearly, the positive predictive value is still quite low, and the number of patients for whom this ocular photography adds substantially to the diagnosis is quite small.  At ~$25,000 a pop for the camera system, and the need for a specialist to screen the images for abnormalities, I do not share these authors’ enthusiasm for its eventual adoption into clinical practice.

“Ocular fundus photography of patients with focal neurologic deficits in an emergency department”
http://www.ncbi.nlm.nih.gov/pubmed/26109710

Foam, Actually

I chastise JAMA on occasion, but, any article that starts like this is the mark of a truly great academic publisher:

“The lights are low and the music volume is high.  As arms and legs sway on a packed dance floor, streams of soapy suds blow down from the ceiling….”

No, it’s not a ‘tween reviewing an illegal high during a rave, it’s a actually CDC surveillance of a spike in eye injuries resulting from “foam parties”.  This write-up details an investigation in Collier County, Florida, in which more than 40 patients sought care for eye irritation and pain in a single night.  These patients all received ocular inoculation with foam during the course of revelry, and over half were ultimately diagnosed with corneal abrasions.  The cause – the highly concentrated chemicals such as sodium lauryl sulfate and other proprietary mixtures similar to those found in soaps and shampoos.

So, beware the foam! (but not the FOAM).

“Party Alert: Here’s Foam in Your Eye”
http://www.ncbi.nlm.nih.gov/pubmed/24129456

“Notes from the Field: Eye Injuries Sustained at a Foam Party — Collier County, Florida 2012”
http://1.usa.gov/1d69xek

Happy Independence Day!

I ought to have posted this piece regarding firework injuries on Wednesday to get folks in the mood – but, better late than never!

This is an entertaining little experiment published in JAMA investigating the mechanism of ocular trauma from fireworks.  These authors created a setup in which a cadaveric eye was suspended in a network of sensors – and then concussive charges and fireworks were exploded at various distances.

Based on their experiments, these authors conclude most of the ocular injury potential is superficial and results from flying debris, rather from any explosive pressure wave.  Fascinating little study!

“Mechanisms of Eye Injuries From Fireworks”
www.ncbi.nlm.nih.gov/pubmed/22760285