Wait, are you white or Asian?

by Juan Ding, OD, PhD

No, the real character in this story does not look like this. Her eyes look identical from the outside.

I want to tell another story of pigment… in the back of the eye. A bit like the previous post, but no one has poor vision this time and it’s all happy… at least till now.

You know you can tell if a person is white or black or Asian or Hispanic usually by their appearance, right? A large part is the difference in skin color- no brainer here. But do you know that eye doctors can tell the racial differences by the color of the retina? Like the skin and iris (blue or brown eyed), the retina, the tissue in the back of the eye, is also lined by pigment cells that show different amounts of pigment. Similar to skin color, white people typically have less pigment in their retina, which shows up more pinkish in color compared to those of darker colors, eg, Asians. However, most of the time, the two eyes will be identical in coloration. So this lady’s eyes are really unique. 

I first met her a few years ago, a healthy middle aged white female interested in new glasses and contact lenses. Her vision was normal and eyes healthy in every aspect, except when I looked at her retina with a lighted magnifier, I felt very confused. Her right and left retinas looked like they belonged to two different people- the right one being very light, just like from a typical white person, but her left retina looked much darker, as if she were Asian (Figure 1). I checked everywhere and both retinas looked completely healthy. There was absolutely nothing wrong with the retinas, just with different shades of pigment. This almost felt like a person had two arms or legs of different skin tones and that is not commonly seen unless a tanning session was done only on one side of the body. 

Figure 1. Color photos of right and left eyes of the same person with a marked different hue. Copy right: Boston Eye Blink

Though everything looked normal, I did refer her to a retinal specialist. 

She came back next year with a diagnosis of ocular melanocytoma in the left eye. 

This is a condition that usually looks like this (Figure 2a) or this (Figure 2b). It’s typically a cluster of pigment cells forming a defined area of pigmentation that can be easily identified.

Figure 2. Examples of ocular melanocytoma. A) optic nerve melanocytoma. Copy right: New York Eye Cancer Center. B) Iris melatocytoma. Copy right: Ophthalmology and Visual Sciences, University of Iowa. In both images, an arrow points to the melanocytoma.

In my patient’s case, her pigment cells are diffused and dispersed, with almost no visible clumps, that it looks natural, smooth and just belongs. There is also no other pigment difference between the two eyes, including on eyelids, conjunctiva and iris. The secret only lies behind the eyes, unrevealed by a dilated retinal exam.

I think it’s marvelous that a pigment disorder turns out just right for her. It’s as beautiful as those people who have different eye colors, iris heterochromia (Figure 3), but it’s well hidden and more mysterious.

Figure 3. Iris heterochromia, where two eyes can be of different colors. Copy right: American Academy of Ophthalmology

My eye is a mess

It was the end of the clinic day. I finished my last patient’s chart and was ready to go, before noticing that a procedure result just popped out. I clicked into it, it’s a visual field testing result of a 60 year old gentleman I saw a few days ago. He complained that after ceiling plaster dropped into his right eye, his right eye could not see in the periphery. 

This is a regular patient of mine. When the plaster incident happened 2 weeks ago I was on vacation so he saw another doctor in the practice. He initially went to the emergency room, received plenty of eye washing and antibiotic eye drops. He then saw my colleague two more times and according to the notes, his eye was recovering well. When I saw him his right eye was white and quiet, cornea completely healed, no defect, scar or edema. Internal structures of the eye were also normal. His visual acuity was 20/20. He did have trouble seeing fingers on the right side in his right eye. But his optic nerve appeared healthy. He’s a glaucoma suspect at baseline and I have been monitoring this over 2 years. The RNFL OCT that measures nerve thickness was stable to before. So the question is, why would he have a new visual field defect? 

Dr. House says, patients always lie. He insisted that this problem came about after the plaster accident. ‘My eye is a mess’, he said. ‘First it hurt like hell for three whole days, then I cannot see out of my right eye’.

For a chemical injury to hurt the optic nerve, there had to be other signs, like inflammation in the anterior chamber, vitreous and retina. But there was none. 

Also it made no sense that he’s losing vision from glaucoma progression, which is typically slow. 

It happened suddenly so it’s not a tumor pressing onto his optic nerve either.

Could he be exaggerating because he was frustrated about the whole thing? After all, he waited in the ED for 4 hours, and he was on hold for scheduling to see eye doctors for a long time and did not get call backs. 

Of course a formal visual field testing is in order. And that result just arrived in my inbox.

One peek at it, I knew I would not be going home any time soon (Figure 1). 

Figure 1. Visual field testing result of the right eye (top image) and the left eye (bottom image). The dark color indicates that the patient was not able to see in that part of the visual field.

The right eye was not seeing the right side of things, just as he complained. Problem is, his left eye was also missing quite a few things on the right side. The left eye was much less severe and it was not picked up in the confrontational visual field test we did in the exam room. 

This is what we call a hemianopsia (Figure 1), and it’s an emergency because a stroke was on the differential list. 

I called him immediately. I advised him to go to ED immediately, even though he did not have any other stroke symptoms. He does have a history of heart attack and has a pacemaker.

I then called his primary care doctor and she was going to follow up with him. 

Hemianopsia happens when one side of the brain that is in charge of vision becomes defective. This can happen with a stroke, a tumor or inflammation. In fact, according to the Cleveland Clinic, 70% of hemianopsia is due to stroke, 15% from brain tumors and 5% from bleeding in the brain [1].  Patients’ eyes can be completely normal, because the problem happens in the brain. It can happen as the only abnormal finding, without other telltale signs of a stroke. The dangerous part is that it is easily missed and over-looked, because the visual acuity can be 20/20, and you don’t find anything wrong with the eyes. Further, patients often describe this in a non-specific manner. Over the years I have heard ‘floaters in the left eye’, ‘my right eye is blurry’, or ‘my eye is a mess’. It is vitally important to always do a confrontational visual field and if suspicious, a formal visual field to clarify and confirm. Otherwise a critical, potentially life-threatening condition may be missed.

Hemianopsia from a stroke may improve over time though may not return to baseline completely, depending on the severity of the damage. Most start recovery within months of the stroke, but it may take up to 18 months for maximum recovery to occur [1]. I will see my patient in 3 months to check his visual field again. To help with vision deficit, certain prism may be used to expand the visual field, but that would the subject of another article.

References: 

[1] https://my.clevelandclinic.org/health/diseases/15766-homonymous-hemianopsia-

Scary- my eye is popping out!

Can your eye really pop out of your head? You see that in cartoons but can it happen to real people?

A group of our optometrist friends were chatting yesterday about this. One said that one of her patients told her about this history, and that she heard about this three times now from different sources. She did not see it herself but she was curious about it. 

I remember such an incident of one of my patients. It was an African American lady in her 30s in good health. I was holding her upper eyelid up in order to examine the lower part of her retina, when she suddenly screamed and screamed, ‘Oh my god, my eye pops out!’ she screamed repeatedly. I almost panicked by her screaming. But I looked at her and saw that her eyelid was retracted and got stuck behind the eyeball and the eyeball was fine. So I gently massaged her upper lid and asked her to blink. A few seconds later her eyelid came down and all was normal. At this time, my technician who was working in the next room came knocking on the door and asked if everything was OK. I told her that all was good. My patient was a little embarrassed about her reaction and calmed down. The rest of the exam was uneventful and the patient left with an essentially normal eye exam.

Having that experience made me cautious about manipulating patients’ eyelids thereafter. Some people’s eyelids are loose and you can easily flip them. If they also happen to have protruding eyeballs, then the lids can get stuck behind the eyeball, which further limits the eyeball from moving.

I thought that eyeball popping out was a misnomer, it’s rather the eyelid going behind. If you think about it, the eyeball is secured by 6 external eye muscles to the eye socket, and the optic nerve which is like a cable also connects the eyeball to the brain. How can you easily get the eyeball out of the socket? If you could, I imagine there would be a lot of damage, potentially to the optic nerve and can cause vision loss. Sure with strong force such as in trauma, eyeballs can fly out of the socket, even the brain can burst out of the skull. But for a person to have spontaneous eyeball popping out, that would require a very high pressure behind the eye, and it just does not happen that easily.

However, it turns out that I did not know this subject well enough. It truely can happen in a condition called globe subluxation. Yes the eyelid could be stuck behind, but the eyeball is really out of (maybe partially) the eye socket. This can be caused by trauma, but it can also happen from triggers such as eyelid rubbing or straining badly. 

Here is a photo from a real patient who suffered from globe subluxation. This is from a recent publication of a case report and all copyright belongs to the original authors and journal [1].

Figure 1. Spontaneous globe subluxation in a middle-aged woman [1]. Copyright in reference [1]

Quite a scene right? No doubt this is very unnerving to the patient as well as to the doctor!

According to this article, the most common risk factor associated with spontaneous globe luxation (SGL) is proptosis (that just means the eyeball is bulging) from having shallow orbits (eye sockets) or things growing in the back of the eyeball. The most common stuff growing behind the eyeball is actually from a condition called thyroid eye disease, in which excess fat and fibroblasts accumulate in the eye socket. Interestingly people with African descent tend to have shallow eye sockets and their eyes generally appear a little more bulging due to this reason. Other factors include loose tissues and muscles supporting the eye, loose eyelid, or having too much fat in the eye socket due to obesity. 

So what harm does globe subluxation do? Seems obvious that an eyeball hanging out is an eyeball not working well for its function, which is seeing. Indeed, if this is severe or goes on for a long time, the optic nerve may be damaged, resulting in vision loss, sometimes permanent. On the other hand, when the eyeball is out, it’s not covered by the lids, and the surface drys out quickly, which can cause pain, light sensitivity and blurry vision immediately. If you think about it, our eyelids really do a good job protecting the eyeball, you can simply close your eyes. With eye protruding out like in the photo above, the eyeball is left there to dry up and exposed to the outside world should something hit or scratch on it.

So how do you pop the eyeball back in? First, relax. Then ask the patient to lay down with face up (or recline on your exam chair). Ask the patient to look down while you gently apply pressure on the globe downward and inward. You can use a cotton swab to roll the eyelids back while applying pressure to the globe [2]. 

Lastly, after the eye goes back to normal, we should probably do some investigation as to why it’s out in the first place. As mentioned above, thyroid eye disease, floppy eyelid syndrome, or maybe even a tumor behind the eye can make a patient prone to developing globe subluxation. So these need to be ruled out.

When I think back about my patient, I wonder if that’s actually not the first time this happened to her. She could not see her eyes, how would she know her eye popped out if she had no prior experience? To me, that was not a true globe subluxation, but rather an eyelid retraction. But her eyelid being so loose and retracting easily should also raise some suspicion on my part to work up further for thyroid eye disease and floppy eyelid syndrome.

According to literature, this is a very rare condition. However it can happen when maneuvering eyelids including when rubbing or inserting/removing contact lenses. I feel lucky that so far I have not encountered this with numerous patients that I have worked with for contact lens I/R training. But the moral of the story is that don’t touch your eyes, cause they can pop out (just exaggerating). 

References

[1] Yadete, T., Isby, I., Patel, K. et al. Spontaneous globe subluxation: a case report and review of the literature. Int J Emerg Med 14, 74 (2021). https://doi.org/10.1186/s12245-021-00398-x

https://intjem.biomedcentral.com/articles/10.1186/s12245-021-00398-x

[2] https://www.reviewofoptometry.com/article/how-to-handle-globe-subluxation