How Salzmann’s nodular degeneration affects your eye
Salzmann’s nodular degeneration (often shortened to SND) causes whitish-gray or bluish nodules to form on the cornea, the clear front window of the eye. They usually appear toward the edge of the cornea, though they can form centrally. Under a microscope they sit just beneath a thinned surface layer, where the cornea’s normal protective layer is disrupted.[1]
The nodules may cause no symptoms at all. When they do, people describe a foreign-body feeling, as if something is in the eye, and blurred vision.[1] The blur comes from shape. Raised nodules make the corneal surface uneven, and nodules can flatten the center of the cornea and add astigmatism, shifting your prescription.[1] Glasses can correct regular changes in prescription but not an uneven surface.
Who gets it. A 2019 review of the literature found SND most common in white women, with a peak in the fifth decade of life and another in the eighth and ninth. It affects both eyes more than half the time. In the largest case series reviewed, 72% of 108 people were female and 66% had it in both eyes.[1]
Its cause isn’t fully understood. It is linked to long-standing surface disease and inflammation, past injury, eye surgery including cataract surgery and LASIK, and long-term contact lens wear, especially soft lenses. The common thread seems to be a surface that has been irritated or disrupted over time, although many people with SND have none of these risk factors.[1] SND can also leave the surface prone to recurrent erosions.[4]
How a scleral lens works over the nodules
A scleral lens is a large rigid gas-permeable lens. It rests on the sclera (the white of the eye) and arches over the entire cornea without touching it. Before insertion the lens is filled with sterile saline, so a layer of fluid sits between the lens and the nodules.
That does two things:
- It replaces the uneven surface optically. Light passes through the smooth front of the lens and the even layer of saline before it reaches the cornea. The saline fills in around the nodules, which largely cancels out the irregularity they cause.
- It covers the nodules. The lens doesn’t touch the cornea, and the blinking lid slides over the smooth lens instead of the raised surface. In the study below, symptom scores improved with the lens.
What the research shows
The evidence is very limited. We found one study of scleral lenses for Salzmann’s. At one university practice, 9 people with symptomatic SND were referred for PROSE, a type of custom scleral lens. After excluding those who didn’t complete the fitting or had other eye problems affecting vision, 7 eyes of 4 people were studied. On average, vision improved from about 20/31 before to about 20/21 with the lens. Scores on a questionnaire about eye symptoms and how they affect daily tasks improved from 46.9 to 21.5, where lower is better.[2]
The authors concluded that PROSE can be an alternative to superficial keratectomy.[2] With only 7 eyes, and without the people who didn’t complete fitting, the study can’t tell you how likely you are to succeed or how many people stop wearing the lens over time.
A 2019 review places scleral lenses as an option for people who haven’t done well with conservative treatment but aren’t good surgical candidates, for example after several recurrences following surgery. It includes the case of an 80-year-old man whose nodules had returned in both eyes after three separate keratectomies and who was then fitted with a PROSE device.[1]
Surgery is the main treatment, and it works for many people. Removing symptomatic nodules, usually by superficial keratectomy (peeling or scraping them off), can restore the cornea’s shape and reverse the prescription changes they cause. Sometimes it is combined with laser treatment, an anti-scarring drug called mitomycin C, or an amniotic membrane graft.[1] Nodules can come back. In one series, they returned in 9 of 41 eyes (22%) after superficial keratectomy. In another, after laser treatment following keratectomy, vision improved in 86% of eyes but nodules recurred in 31%. A study of keratectomy with mitomycin C in 30 eyes reported no recurrences over an average of 28 months.[1]
If you’re planning cataract surgery
Salzmann’s matters before cataract surgery. Even nodules near the edge of the cornea can flatten its center and add astigmatism. That can make it harder to take the measurements used to choose the lens implant. A 2019 review recommends considering removal of the nodules before cataract surgery. It describes a case in which nodules made reliable measurements difficult until they were treated.[1]
If you already wear a scleral lens and are planning cataract surgery, ask both your surgeon and your fitter how the lens, the nodules, and the timing of any procedure fit together. Your lens prescription may need updating afterward.
Other options, compared
| Option | What it does | Typically suited to |
|---|---|---|
| Observation | Monitoring without treatment | Nodules that cause no symptoms |
| Lubricants and treating surface disease | Ease irritation and treat the underlying surface problem | Mild symptoms; alongside any other option |
| Glasses or soft lenses | Correct regular prescription changes | Mild blur without much surface irregularity |
| Corneal rigid gas-permeable lenses | Give a smooth optical surface on the cornea | Mild irregularity |
| Scleral lenses | Vault the cornea and nodules over a fluid layer | Irregular vision when surgery isn’t wanted, isn’t suitable, or nodules keep recurring |
| Superficial keratectomy (with or without mitomycin C or amniotic membrane) | Removes the nodules | Symptomatic nodules; the usual first-line procedure |
| Phototherapeutic keratectomy (laser) | Smooths the remaining surface | Often combined with keratectomy |
| Lamellar or full-thickness corneal transplant | Replaces corneal tissue | Rarely needed; nodules extending deep into the cornea |
Questions to ask a scleral lens fitter
- How many patients with Salzmann’s nodules have you fitted?
- Would surgery to remove the nodules be a better first step for me?
- Will the lens clear the nodules near the edge of my cornea, and how will you check?
- If I later have the nodules removed, will I still need the lens?
- I’m planning cataract surgery. Should the nodules be dealt with first?
- How many visits does a fit usually take, and what do the fees cover?
Common questions
Do scleral lenses get rid of Salzmann's nodules?
No. The lens arches over the nodules and corrects the blur they cause while you wear it. The nodules are still there. Removing them takes a procedure such as superficial keratectomy.
Should I have surgery or try a scleral lens first?
Surgery to remove symptomatic nodules is the usual recommendation, and it can restore the cornea's shape. A scleral lens is more often considered when nodules keep coming back after surgery, when surgery isn't a good option, or when you'd prefer to avoid it. Talk it through with a cornea specialist.
I'm planning cataract surgery. Does Salzmann's matter?
It can. Nodules, even near the edge of the cornea, can flatten the center of the cornea and add astigmatism, which can throw off the measurements used to choose your lens implant. A 2019 review suggests considering removing the nodules before cataract surgery. Ask your surgeon.
Can contact lenses cause Salzmann's nodules?
Long-term contact lens wear, especially soft lenses, has been associated with Salzmann's, along with surface diseases, injury, and eye surgery. An association doesn't mean the lens caused it. If you wear lenses and have nodules, your fitter will look at how the lens sits over them.