Treating a Rare Corneal Disease
By William L. Miller, OD, PhD, FAAO
Salzmann's nodular degeneration (SND) is a condition that is rarely seen even if your practice is geared toward anterior segment pathology. SND may be idiopathic or caused by phlyctenular keratoconjunctivitis or trachoma. However, generalized cases of corneal inflammatory disease may also be precursors. Other conditions associated with the genesis of SND include ocular trauma, surgery, and meibomian gland disease. Some reports indicate that SND may be associated with contact lens wear—mostly soft lenses (Hamada et al, 2011; Farjo et al, 2006). SND can be unilateral or bilateral and is reported more frequently in middle-aged white women.
Signs and Symptoms
Many patients will be asymptomatic, but some may experience reduced visual acuity. They may also complain of visual disturbances as a result of the induced irregular astigmatism. SND will appear as solitary or multiple yellowish white to blue nodules arranged circularly in the region of the central and midperipheral cornea. They are typically without neovascularization; however, areas surrounding or deep to the nodules may become vascularized. A pigmented line at the base of the nodule may be present, much like a Fleischer's ring in keratoconus. The size of the individual nodules is usually small, around 1mm to 2mm in size, and nearly round in shape. The nodules are slowly progressive and can cause refractive error changes. They are typically located anterior to the anterior limiting lamina, which is often absent or discontinuous, although the epithelium will remain intact. But advanced SND can penetrate to underlying stromal tissue.
Diagnosis is based predominantly on biomicroscopic findings, although auxillary instrumentation such as in vivo confocal microscopy may give indications as to the histopathologic changes that occur. Differential diagnosis should include spheroid degeneration and corneal keloids.
Figure 1. An example of Salzmann's nodular degeneration (SND). COURTESY OF JAN BERGMANSON, OD, PHD
Options for Treatment
Treatment for most SND patients will be aimed at targeting the symptomatic sequelae from the disease, which will likely include dry eye complaints and recurrent corneal erosions. These can be managed with topical lubrication in the former and bandage contact lenses and lubrication and/or topical hyperosmotics in the latter. For those patients who have meibomian gland disease-induced SND, the addition of systemic doxycycline will also prove beneficial in preventing exacerbation of the disease process. The additional contemporary use of lipid-replacing tear supplements may also be helpful.
For patients for whom medically conservative therapy fails, the next step is referral to a corneal surgeon for an excision, lamellar keratectomy, or phototherapeutic keratectomy. A lamellar procedure and in rare cases a penetrating keratoplasty are indicated in cases of SND that bridge into the midstromal region of the cornea. Some have also advocated the concomitant use of mitomycin-C after surgery aimed at preventing an SND recurrence (Bowers et al, 2003). At least one report advocates use of a diamond burr to perform a superficial keratectomy to remove visually significant anterior lesions such as SND (Malta and Soong, 2008). CLS
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Dr. Miller is an associate professor and chair of the Clinical Sciences Department at the University of Houston College of Optometry. He is a member of the American Academy of Optometry and the AOA where he serves on its Journal Review Board. You can reach him at firstname.lastname@example.org