Ocular Histoplasmosis

(Presumed Ocular Histoplasmosis Syndrome, or POHS)

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Read the page and the associated links for a great deal of information about POHS. After you've learned a bit, we have a Forum so you can ask questions and communicate with others

Note: :After many years of service, our old Bulletin Board provider has disappeared. We have a new board as of June 2007: Ocular Hisoplasmosis Forum. See the introductory post there for more information. Sorry for the inconvenience.

Informational links about POHS


Read the information in this link first for a comprehensive overview of POHS:

Background about histoplasmosis and more detailed information about histo and POHS

My POHS Story

I am not physician. Just a person with POHS. Here's my story so far.

One November day, I noticed a blind spot in my right eye. I went to New York University Medical Center's Emergency Room, where the Ophthalmological resident noted blood in my retina. Choroidal hemorrhage in someone my age is uncommon, so he directed me to Dr. Carol M. Lee, who specializes in diseases of the retina and vitreous.

During my retinal exam the next day, Dr. Lee stopped and asked me "Where did you grow up?" When I answered that I hail from East Tennessee, she was fairly certain that the oddly pigmented areas she discovered on my retina were "histo spots." That was the first I heard of ocular histoplasmosis. I was fortunate that Dr. Lee is not only an outstanding physician, but that she had trained in St. Louis, in the "Histo Belt."

Dr. Lee lasered the membrane soon thereafter, though much of the area was obscured by blood. In a few weeks, it was apparent 1) that the membrane was still growing and threatening to impinge on my fovea, and 2) I was a candidate for submacular surgery.

After a great deal of reading about the surgery and a phone conversation with Dr. Matthew Thomas (with whom Dr. Lee studied), I decided to fly to St. Louis and have it performed by Dr. Thomas. He had developed most of the techniques and instruments used in the surgery at the Barnes Retina Institute, and one could tell even from his medical writings (especially the chapter on the surgery in Retina) that he was a good fellow as well as a good surgeon.

The following January Dr. Thomas performed the surgery. My visual acuity before the surgery was 20/200, and six months later it was about 20/30, though I have significant blind spots in my right eye. There is no evidence of recurrent membrane growth--yet. Some of my visual problems are due to cystoid macular edema (or swelling), which I hope will respond to the treatment method described by Groucho Marx: "Time wounds all heels."

From Drs. Lee and Thomas and their staffs I received the best medical care for my condition available in the world (the surgery wasn't even attempted until 10 years before I had it, has been greatly refined in the intervening decade, and Dr. Lee's care and follow-up have been first-rate). Still I have rather limited vision in my right eye. But 20/30 with blind spots is better than 20/200 with a huge blind spot and encroaching membrane.

I am thankful there are no histo spots in my left eye.

Keith Spurgeon
keith - AT -bway.net

Update 2 yeas after first occurence: I still have the same blind spots, and the retinal pigmented epithelium has been disturbed, so it appears I will always have large blind spots. But, between the scotomas, I have 20/25 vision in my right eye.

To read stories of others with POHS, visit the letters page We also have a Bulletin Board so you can ask questions and communicate with others who have POHS

Questions and Answers:

I have received a few questions, so I'll try to answer them here as best I can. I'm not an M.D., though I consult the medical literature to answer these questions. Consult your physicians before acting upon any medical information you see on the Internet--or in a newspaper, magazine, or book, for that matter.

Cause of membrane growth
Q: I am curious as to the cause of the problem after so many years. The last I heard the reasons were still not well understood. Do you have any more current information?

A:The type of biomolecular work that'll have to be done to assess why these membranes grow has only just begun--there's one study about growth factors published in 1995 and not a whole lot else, though I haven't done an exhaustive search about it. There may to be some similarity between the causes of membrane growth in the "wet type" of age-related macular degeneration and POHS, and in that case we may benefit by research done into either syndrome. We hope for a good drug that will stop these membranes from growing.

POHS is hard to study in animal models because the best candidates are primates (they have a macula like we do while nonprimates don't), but they live a long time, too. And as you know there are usually quite a few years between the initial infection and the membrane problem, so it takes a long time to study this disorder.

Here's a bit on what is known (not much) about the growth of the membranes:

The initiator for this abnormal growth of new blood vessels is unknown. The results from HLA typing suggest that there may be a genetic predisposition for progression from atrophic scars to disciform lesions in ocular histoplasmosis. They also suggest that there may be a genetic factor that accounts for development of clinically apparent histo spots in the eyes of some persons infected with H. capsulatum and not others. Other hypotheses have attributed these infections to a larger initial inoculum of the fungus, reinfection, hypersensitivity, and presence of other risk factors that compromise the vascular system or the immune system.

[From chapter 103 of "Retina" 1994 edition. Full citation: Ocular Histoplasmosis, Hawkins, B.S., Schachat, A.P., Alexander, J., in Ryan's Retina, 2nd Edition, C. V. Mosby Company, St. Louis, 1994.]

Seems like they're throwing about everything against the wall there.

A recent study published in April, 1998 seems to indicate that reactivation of choroidal lesions doesn't contribute to neovasculation.

Recurrence of Membrane after Submacular Surgery
Q:From what I understand, there has been a study on the reoccurance rates of patients who have had submacular surgery. Are you familar with this study?

A: Probably the most comprehensive study about the recurrence of the membranes after CNV removal surgery is:

Managing recurrent neovascularization after subfoveal surgery in presumed ocular histoplasmosis syndrome. [Melberg NS, Thomas MA, Dickinson JD, Valluri S; Ophthalmology 1996 Jul;103(7):1064-1067 ]

The abstract to the study is available in Medline, so point your browser to:

http://www.ncbi.nlm.nih.gov/htbin-post/Entrez/query?uid=8684795&form=6&db=m& Dopt=b

The abstract is a bit sketchy (it's always better to have the full article, of course), so let me type in a bit from the discussion section of the paper:

Earlier studies on the surgical management of subfoveal CNV in the POHS have reported a postoperative reccurrence rate of 13% to 37%. Two of these studies had relatively short-term follow-up. In the third study, if only eyes with at least 12 months of follow-up were analyzed, the recurrence rate rose to 46%. This suggests that duration of follow-up is important in determining an estimate of recurrent neovascularization after subfoveal surgery. In the current study, the recurrence rate was 44%. Although this is the largest series with the longest follow-up reported to date, this figure is probably an underestimation. Although 84% of recurrences occur within 6 months and 88% of eyes in this study had at least 6 months of followup, this retrospective data will miss some recurrences. The actual recurrence rate may realistically approach 50%. Consequently, in our practice, we treat each patient as if a recurrence will develop.
For anyone looking over the medical literature and trying to cope with the statistics presented, I recommend reading Stephen Jay Gould's essay The Median Isn't the Message. It shows why the summary data about any disorder doesn't tell the whole story, and how seemingly dire statistics can be heartening--if you know how to interpret them.

Email keith *AT* bway.net

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