BLOG: What is ‘true’ lens exfoliation?
Click Here to Manage Email Alerts
Most optometrists are familiar with pseudoexfoliation, a flaking anterior lens capsule that signals a higher risk for glaucoma, loose zonules and even cardiovascular disease and dementia, according to Katsi and colleagues.
However, “pseudo” comes from a Greek root word meaning “false.” So, if pseudoexfoliation is a false lens exfoliation, what is real exfoliation?
So-called “true” lens exfoliation (TEX) is a condition first described in 1922, when Austrian ophthalmologist Anton Elschnig, MD, noticed damage to the anterior lens capsule in workers who were routinely exposed to high heat, especially glassblowers, blacksmiths and steelworkers. The condition was diagnosed frequently thereafter for about 10 years, after which the incidence decreased, possibly because of the advent of better eye protection (Callahan et al.). It is now quite rare. Because of its association with intense heat, it is assumed to be caused by infrared radiation and became known as “glassblower’s lens.” It has also been reported to occur in cases of uveitis, trauma or advanced age.
TEX appears as a delamination of the anterior lens capsule, in which a smooth-edged crescent of capsule splits and scrolls. The rent occurs in the peripheral capsule, parallel to the equator. In many cases it continues splitting circumferentially until a circular flap of diaphanous capsule almost completely detaches and floats, hinged, in the anterior chamber.
Why would heat damage the peripheral capsule, which would not suffer direct infrared radiation from a heat source, and yet leave the exposed central capsule untouched? One theory is that the pigmented iris serves as a heat sink that then bakes the capsule. Another theory states that lens epithelial cells, especially peripheral ones that are actively dividing, are particularly vulnerable to heat (Cooke et al.). In either theory, the weakened capsule is finally split and peeled by the rubbing and kneading of the posterior iris.
The condition is quite asymptomatic and, unlike with pseudoexfoliation, no treatment is necessary. However, these capsules can tear unpredictably, so any surgeon planning on doing cataract surgery should be prepared.
The two exfoliative conditions were first differentiated in 1954 by the brilliant Czech ophthalmologist Georgiana Dvorak-Theobald, MD, and as true exfoliation had already been studied, she named the new condition “pseudoexfoliation.” TEX can be differentiated from pseudoexfoliation by its smooth edges and the absence of fluffy gray-white material on the lens and pupil. The edges of TEX delamination have a sharper and cleaner look than in pseudoexfoliation. The two conditions do not appear to be related, and TEX has not been shown to increase the risk for glaucoma (Dvorak-Theobald).
The labels “true” and “pseudo” exfoliation, therefore, turn out to be simply artifacts of the chronological order of their discovery.
Remember Thomas Hobbes’ quote: “True and false are attributes of speech, not of things. And where speech is not, there is neither truth nor falsehood.”
References:
- Callahan A, et al. AMA Arch Ophthalmol. 1958;doi:10.1001/archopht.1958.00940020099010.
- Cooke CA, et al. J Cataract Refract Surg. 2007;doi:10.1016/j.jcrs.2006.12.019.
- Dvorak-Theobald G. Am J Ophthalmol. 1954;doi:10.1016/j.ajo.2018.02.018.
- Hobbes T. Leviathan; 1651.
- Katsi V, et al. N Am J Med Sci. 2013;doi:10.4103/1947-2714.117294.
For more information:
Oliver Kuhn-Wilken, OD, practices at Pacific Cataract and Laser Institute’s Tualatin Clinic in Oregon.
Collapse
Read more about
Click Here to Manage Email Alerts