On retinas and occlusions

Recently, I developed a blockage of a vein in the retina of the eye (branch retinal vein occlusion, BRVO). Because of this, fluid accumulates in the eye (forming an oedema). This in turn distorts a portion of my vision, with lines appearing wavy rather than straight. The only solution is to inject drugs that will deal with the oedema, but cannot do anything about the blockage.

I have a couple of injections of Ranibizumab, an anti-angiogenic medication. It works by “blocking a protein called vascular endothelial growth factor (VEGF). This stops the growth and leakage of abnormal blood vessels in the eye(s) that may cause vision loss.”

Each injection holds the problem at bay for 1-2 months, but then the doctor decides to administer a different drug, a corticosteroid Dexamethasone, which is supposed to be effective over a longer period of time. I do not realise, until later, that it is an implant!

This is my idiosyncratic documentation of the post-injection period.

Jan 24 The procedure takes longer than the previous times, I wonder and comment  about it at the end of the procedure, at which time the doctor casually mentions that I will see something floating around in my eye, but that it will soon disappear and I should not worry about it. I am exhausted, and sleep through from 8 pm to 7 am the next day.

Jan 25 I see the injected object — a black silhouetted narrow cylinder floating around.

  • The length of the rod seems to occupy about 1/3 of the field of vision when I close my eye
  • It floats across and top an bottom, along the edges of the eye, absolutely stiff; looks like a log on the surface of a body of water
  • It does not take a circular path in the eye when I rolled my eye, only moves around.
  • While doing yoga (lying down, twisting exercise) I notice that, when I have my head turned left, it floats up (against gravity) and toward the right corner (kadai) of the left eye; ditto when my head is turned to the right; then it moves toward the left corner (kadai) of the left eye.

Jan 29 in the morning, it turns really frisky! Movement seems uncontrollable and fast!

  • The length of the rod seemed to occupy about 1/4 of the field of vision when I close my eye
  • It is turning somersaults, turning over on itself every time I move my eye (much less when my eye is closed)
  • It turns dizzy circles around when I roll the eye; very distracting when I try to concentrate on doing yoga. I was reminded of my ~6 year old son, at one stage in his life, spent a lot of time rolling his eyes; when questioned, he said that he was following the floaters…

Jan 30-31, it has started moving around like a fluttering lash, swishing left and right.

After these observations, I develop a tentative explanation

      • the rod length (and width) reduces because that’s the drug being dispensed
      • if it exceeds a certain length (at least 1/4 the eyeball), it cannot (physically) tumble around in the vitreous chamber
      • once it goes below this length, it can
      • so, if we can look at the dimensions of the eyeball, we could get a sense of
        • how long the rod is
        • how minimally “deep” the chamber is

Hmm. Not sure it works that way.

Here is the eye. Where exactly is this rod swimming around?

The depth of the vitreous chamber seems to be on average 15 mm for the normal eye. Does this mean the initial size of the rod was at least 5 mm (probably smaller) and that it now is about 4 mm? That seems pretty large!

And so it is! I could have saved myself this circuitous path to this knowledge: the size of the implant is “approximately 0.46 mm in diameter and 6 mm in length.”

Feb 1-2 Still moving around like a fluttering lash, swishing left and right.

Feb 3 Mostly confined to the upper part of the eye, but still visible when I do the twisting movement in lying down yoga posture. I just get some glimpses otherwise.

Feb 4 Mostly visible only in the upper part of the eye, making a little windscreen wiper movement

Feb 5-15 Practically not there – only visible while lying down: just visible in upper part, no circular movements when I rolled the eye. It just does a weak, half-hearted sweep, only stage right to middle of the eye.




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