Thygeson’s superficial punctate keratitis (TSPK) is classified as a rare disease. No precise prevalence figure exists because the condition is so uncommon that large-scale studies have never been conducted. There are no multicenter trials or randomized controlled studies on TSPK, and the entire published literature draws from only a few hundred documented cases. In a review of all available data, researchers could identify just 241 patients total across decades of published reports.
How Rare It Actually Is
TSPK is rare enough that most eye doctors will see only a handful of cases in an entire career. The absence of any reliable incidence or prevalence statistics tells its own story: the condition simply doesn’t occur often enough for researchers to calculate a meaningful rate. For context, diseases typically need to affect fewer than 200,000 people in the United States to qualify as “rare” under federal definitions, and TSPK falls well below that threshold.
The condition is even rarer in children. Among the 241 cases compiled in one literature review, only 10 were children (about 4%), while 32% were adults, and the rest had no age recorded. This means a child presenting with TSPK is an unusual finding even within an already unusual disease, which can lead to delayed or missed diagnoses in younger patients.
Why It’s Hard to Diagnose
Part of the reason TSPK may be underreported is that it mimics more common eye conditions. The small, raised lesions on the cornea can look similar to viral infections like herpes simplex keratitis or adenoviral keratitis. A key distinguishing feature is that TSPK does not cause the redness and inflammation of the white part of the eye (conjunctivitis) that typically accompanies those infections. The eye looks relatively quiet and uninflamed compared to what the corneal findings would suggest.
Another clue is that TSPK does not respond to antiviral or antibiotic eye drops. If a patient has been treated for a suspected viral or bacterial infection and the corneal spots keep coming back, TSPK should be on the list of possibilities. Because the condition is so rare, though, many patients go through multiple rounds of ineffective treatment before getting the right diagnosis.
What Causes It
The exact cause remains unknown. The leading theory involves an immune reaction in the cornea, possibly triggered at some point by a virus. Researchers have looked for active viral infections during flares, testing corneal samples for herpes simplex, adenovirus, and varicella zoster. Those tests almost always come back negative, suggesting that even if a virus plays a role in setting off the disease, it isn’t actively present during symptoms.
What does appear during flares is an increase in specialized immune cells within the corneal surface layer. These immune cells correlate with active disease, which supports the idea that TSPK is driven by the body’s own immune response rather than an ongoing infection. This also explains why it responds to treatments that calm immune activity rather than those that fight viruses.
What Flares Feel Like and How Long They Last
Individual flares typically cause tearing, light sensitivity, a foreign body sensation, and mildly blurred vision. Both eyes are usually affected, though not always equally. Each episode generally lasts one to two months, followed by a remission period of four to six weeks before symptoms return. This cycle of flare and remission continues for an average of two to four years before the disease resolves on its own.
Some people are not that lucky. Rare cases have persisted for as long as 20 years. The good news is that TSPK almost never causes permanent vision loss or lasting corneal scarring. Once the disease finally burns out, most people retain normal visual acuity.
How Flares Are Managed
The most common treatment for active flares is low-dose steroid eye drops, which suppress the immune activity driving the corneal lesions. These work well for short-term control but aren’t ideal for long-term use because prolonged steroid drops can raise eye pressure and increase cataract risk.
For people who flare frequently or can’t tolerate steroids, cyclosporine eye drops offer an alternative. Cyclosporine works by calming the immune response without the side effects of steroids. In prospective studies, cyclosporine drops suppressed both the surface lesions and the deeper opacities that can develop over time. One published case followed a patient on cyclosporine drops for four and a half years, during which the disease went into complete remission with clear corneas and perfect vision.
A simpler option that works for some people is therapeutic soft contact lenses. In a small study, wearing a bandage contact lens resolved the corneal lesions and relieved symptoms, sometimes within 24 hours. Three out of four patients in that report were able to manage the condition with daily or extended-wear soft lenses alone, avoiding the need for steroid drops entirely. This approach may be worth discussing if you prefer to minimize medication use.
Living With a Rare Diagnosis
The rarity of TSPK can be frustrating. You may see multiple eye care providers before someone recognizes it, and you’re unlikely to meet another person with the same condition. Because there are no large clinical trials, treatment decisions rely heavily on case reports and small studies. Your doctor is essentially tailoring a plan based on limited published experience combined with how your eyes respond.
The reassuring part is that TSPK, despite being chronic and annoying, carries an excellent long-term outlook. It does not lead to serious vision loss. Flares are manageable with available treatments, and the disease eventually resolves on its own in the vast majority of cases.