Whenever I deem a case of viral conjunctivitis to be significant enough to warrant the prescription of a topical steroid, I have a very brief discussion with the patient beforehand.
I explain that I’m not targeting the virus itself, but rather the patient’s immune response to the viral insult. I liken it to a cold in which supportive therapy and anti-inflammatory medications don’t kill the virus but rather make the patient feel better as the condition runs its course.
It’s possible that similar conversations may be had in the future with respect to common retinal diseases as we become more familiar with the underlying mechanisms of action (however complex and multifactorial they may be).
Previously by Dr. Casella: Ensure patients know follow-up visits may be covered
Retinal immune response
An August 2019 review published online in Frontiers in Immunology does well to lay out where we stand with respect to our understanding of the link between the immune system and the various structures and chemicals that make up the neurosensory retina.1
This paper focuses specifically on microglia, the macrophages of the retina whose function is to go around eating up undesirable particles.
In addition to giving a nice synopsis of the history and discovery of microglia in the nervous system, the authors explain what we know about the role of these agents with respect to the formation and progression of several common degenerative retinal conditions. Additionally, the role of microglia during retinal development and subsequent retinal function is discussed.
Age-related macular degeneration (AMD) is discussed in detail with regard to the immune system. Complement factors and other inflammatory proteins have been found in elevated levels in the presence of AMD.
Enlarged microglia have been isolated in close proximity to retinal drusen, as drusen are chemoattractants for microglia, thus yielding an explanation for their movement into the subretinal space in those with AMD. This provides further evidence for a dysregulated immune response as having a causal role in AMD.
1. Rashid K, Akhtar-Schaefer I, Langmann T. Microglia in Retinal Degeneration. Front Immunol. 2019 Aug 20;10:1975. doi: 10.3389/fimmu.2019.01975. eCollection 2019.