Lisch nodules are small, benign growths on the surface of the iris, the colored part of the eye. First described in 1937 by Austrian ophthalmologist Karl Lisch, these nodules are hamartomas. This means they are composed of a disorganized collection of mature, normal cells—in this case, pigmented dendritic melanocytes. These growths are harmless and do not cause symptoms or require medical intervention.
Appearance and Characteristics
Lisch nodules are well-defined, dome-shaped elevations on the iris surface that measure between one to two millimeters in diameter. Their color can range from clear to yellowish-brown, and their appearance may differ depending on iris color; they often look darker in blue eyes and lighter in brown eyes. The nodules can be translucent, making them difficult to see, or more opaque and visible as brownish spots.
These growths are found in both eyes and increase in number and size as a person ages. They begin to appear during childhood, becoming more prevalent around puberty, and it is common for multiple nodules to be present.
Connection to Neurofibromatosis Type 1
The presence of Lisch nodules is strongly linked to Neurofibromatosis type 1 (NF1), a genetic disorder. Their appearance is one of the established diagnostic criteria for NF1, a condition characterized by the growth of tumors along nerves. The identification of two or more Lisch nodules is a significant indicator used to confirm an NF1 diagnosis, particularly in younger patients.
More than 90% of adults with NF1 have Lisch nodules, making them the most common ocular manifestation of the disorder. Their detection often prompts further investigation for other signs of the underlying genetic condition.
Diagnosis and Impact on Vision
An eye care professional, such as an ophthalmologist or optometrist, identifies Lisch nodules during a routine eye exam. They are often too small to be seen without specialized equipment. The standard method for detection is a slit-lamp examination, which uses a microscope with a high-intensity light beam for a detailed, magnified view of the iris surface. This noninvasive method is accurate for diagnosis.
Lisch nodules themselves are harmless and do not interfere with vision or cause any physical discomfort. Patients are typically unaware they have them until found during an exam. The nodules do not require treatment, as medical management is directed at the systemic effects of Neurofibromatosis Type 1.