Cataracts , Keratoconus, Pellucid Marginal Degeneration - Found an Expert
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I came across an article on exactly my situation: "Managing the Keratoconus and PMD Patient Who Has a Cataract. https://www.cornealphysician.com/issues/2022/april-2022/managing-the-keratoconus-and-pmd-patient-who-has-a
As I finished reading the article I was thinking "This was really thorough and good, but it points out so many pitfalls and possibilities -- how am I going to tactfully make sure my surgeon, whoever that ultimately turns out to be, is aware of all these things?" Then my eye fell on the names of the authors at the bottom of the article.The second name jumped off the page at me, because she is the director of the eye clinic right down the street from my house! I immediately got on the phone and made an appointment to see her. She had a cancellation so there was an opening in exactly one week from today!
I have PMD, which is a thinning of the cornea, leading to sagging and lots of astigmatism. Fortunately, its only in one eye, although the other has astigmatism too. In addition to the challenge of dealing with lots of astigmatism, the cataract surgeon has to think carefully about where and how to do the incision through such a weak cornea. That's one of the things the article covers.
I won't attempt to summarize the article, but one thing I was really happy to see was she talks about the use of the IC-8 pinhole IOL in cases like mine. It's just a small part of the article but I really like the idea of a pinhole IOL and it's probably the reason my Google search landed on this article. I was Googling "IC-8 IOL in Pellucid Marginal Degeneration" (without quotes).I have Googled many, many different search strings related to cataracts and PMD, but this was the first time I encountered this article. And what luck that it happened to be co-authored by a doctor near me and that I recognized her name and that she had an opening on her calendar so soon!
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RonAKA jimluck
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Thank you for the article link as I have been diagnosed with Keratoconus. I recall there is a special reconstructive PRK that they can potentially do with a vitamin B or something that is supposed to fortify the cornea. Have not read the article but I will...
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Have now read it. The procedure I was talking about is called Corneal cross-linking (CXL). This article however seems to be focused on dealing with Keratoconus (KCN) prior to cataract surgery, but I unfortunately was not diagnosed with KCN until after surgery by a Lasik specialist. My cataract surgeon only said irregular astigmatism and didn't say a word about KCN.
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Reading this article reinforces my hindsight conclusion that I really should have gotten a toric lens. I was quite willing but my surgeon kept flip flopping on it, and I finally said no. Hindsight is always perfect, but if I had it to do over again I would have gotten a sphere IOL power 0.5 D higher, and the -1.0 D cylinder toric. That would have put me at -1.5 D sphere and perhaps got my astigmatism under 0.5 D.
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This said my vision is still pretty good and I very seldom wear my +1.25 glasses.
RonAKA jimluck
Posted
I recall researching the IC-8 and have saved links to some articles. I dismissed it as an option for me, but I don't really remember why, beyond the fact it may not be available in Canada. Here is a quote from one article on who many not be suited to the lens:
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But there must be patients unsuited for the IC-8 IOL – what factors do our experts consider? Vote is clear: “Avoid eyes with central corneal scarring that overlaps the center aperture.” He also notes that he typically excludes patients with mesopic pupil sizes >6 mm as they are more likely to experience dysphotopsias, especially glare. Similarly, Shiu counsels avoiding eyes with with mesopic pupils larger than 5 mm (again, because the patients will likely experience halos and glare), and patients with macular pathology (because the IC-8 lens’ pinhole effect may reduce contrast too much). “I also avoid patients with severe glaucoma because of their existing issues with restricted visual field and contrast sensitivity,” says Shiu. Chan avoids monocular patients, patients with vitreous opacity, large or eccentric pupils, and those with retinal diseases such as AMD, advanced glaucoma, or significant diabetic retinopathy. Similarly, Auffarth cautions against implanting an IC-8 IOL in patients with very high need for near vision, severe retinal problems, glaucomatous damage, capsular rupture, pseudoexfoliation syndrome, or zonular weakness. Beltz suggests avoiding patients who don’t want to notice a difference between their eyes, and those at high risk of developing ocular diseases such as glaucoma, AMD, or DR."
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What I see is that the IC-8 is typically only used in the non dominant near eye, and with about -1.0 D myopia, or essentially a micro monovison. It could be similar to using a Vivity at -1.0 D?? Reading in lower light is always an issue with IOLs, and the IC-8 may make that worse? Lots of things to consider. Have a read of this article if you have not already.
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The IC-8 IOL: Big Advantages Through Small Apertures 09/09/2019
jimluck RonAKA
Posted
Yes I have read that article. There are a lot of articles out there and they all seem to report good results. Good visual acuity at all distances, plus good night vision, plus correction of up to 1.5 d of astigmatism with a high degree of forgiveness if the surgeon doesn't exactly hit refractive targets, plus no worries about post-operative rotation because it's not a toric lens. It is a monofocal lens coupled with a small aperture. The lens is usually targeted to slight myopia but the small aperture gives 20/20 distance vision thanks to the pinhole effect, despite the myopia targeting, so it is not mini monovision. I am thinking of it for my left eye, where my astigmatism is not too bad. I would still need glasses for the residual astigmatism, but my priority is sharp vision, not necessarily glasses independence. If it would enable me to see well with monofocal glasses at all distances, that would be great. I might even put it in both eyes. Food for thought.
RonAKA jimluck
Posted
I would not put it in both eyes, and when they target -1.0 D it really is micro-monovision. Be careful.
RonAKA jimluck
Edited
I have been doing a bit of research on Keratoconus and collagen cross-linking combined with TG-PRK to address it and I found this article from a MD at the Bochner eye clinic in Toronto. I recall you were considering them. It seems one can do the cross-linking combined with TG-PRK prior to cataract surgery in order to simplify the cataract surgery, and toric lens requirement.
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Give Keratoconos The One Two Punch Raymond Stein MD
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I also noticed when doing some checking of the VisionMax Clinic in Edmonton that they seem to offer IOLs with up to 12 D cylinder correction. They also offer the collagen cross linking.
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This said I saw a doctor at another Lasik clinic today and he said the combination of cross linking and TG-PRK is relatively new and the long term stability of it was still not proven.
jimluck RonAKA
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Thanks Ron. That's really amazing that you're keeping me in mind and posting something tailored for me weeks later when you come across something relevant. Very thoughtful!
Thankfully, my astigmatism is pretty regular, despite its severity in the right eye and despite the big beer belly in the cornea below the central zone that is the only part relevant for eyesight. And it has been stable for many years. So my doctors don't want to do anything radical. They're optimistic a toric lens of sufficient cylinder will vastly improve my uncorrected visual accuity. They point to a red line on my topo map and say "see -- it's pretty straight where it crosses the central area." Apparently that's a very good thing. It sure isn't straight elsewhere.
Three interesting cornea stories:
My thoughts on residual astigmatism: I plan on wearing glasses for distance after surgery. If they have to have some cylinder correction in them, that's no big deal. It would be nice if the lenses were thin -- only possible if most of the astigmatism is gone. My priority is to have great near vision without glasses. I find moderate astigmatism is not much of an issue up close. My left eye now has -2.25 cyl in the glasses prescription but gives great uncorrected near vision. The astigmatism correction becomes more important farther out. But there's a limit even for near vision on how much astigmatism can be ignored. The right eye vision is an absolute mess at all distances without glasses, due to its -8.25 needed cyl. It's amazing how good it becomes with the glasses given where it starts out. I mean, 20/40 ain't bad compared to complete mess! And I used to get 20/30 before the cataract worsened.
Sometimes I think about what life for me would have been like in previous centuries without high-cyl glasses and electronic hearing aids. Not good.
RonAKA jimluck
Posted
"Thankfully, my astigmatism is pretty regular, despite its severity in the right eye and despite the big beer belly in the cornea below the central zone that is the only part relevant for eyesight."
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I looked at the Pentacam topography map for my left irregular astigmatism eye yesterday at the ophthalmologist's office. He explained that the steepest area of the cornea is give a hotter colour and the least steep is a cooler colour. I have a somewhat hotter colour in the bottom left quadrant well off center. He said that with normal astigmatism this hotter area of higher steepness should be centred on the middle of the eye. Mine is not. I think that is kind of the definition of irregular astigmatism.
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I suspect the reason you are getting different results from the 1/d=f formula is the impact of astigmatism. The surgeon called it myopic astigmatism. The steepness of the cornea in that area gives me significantly closer vision than the sphere alone would predict. He says that is the reason he would be very hesitant to correct my astigmatism with Lasik or PRK. I would lose my current very good reading vision.
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The idea of doing PRK first before cataract surgery is interesting. It kind of gives the surgeon two shots at getting things right. Once with PRK, and then a second time later with a toric IOL. The risk as I see it would be in getting the measurements of the eye correct post PRK to accurately predict the sphere and cylinder power needed.