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March 15, 2004

Other

Question from Tacoma, Washington, USA:

My 10 year old daughter was diagnosed with CNVM (Choroidal Neovascular Membrane) today by a neurosurgeon. What percentage of children get this disease? Is it a diabetes related problem? Is a laser procedure the only treatment option?

Answer:

Choroidal neovascular membranes are uncommon in children. The presence of a CNVM requires a break/rupture in the tissue underlying the retina (the “retinal pigment epithelium” or RPE, and/or the elastic tissue attached to it, called “Bruch’s membrane”) whereby new blood vessels grow up between these breaks, analogous to grass growing up between cracks in a side walk. Age-related macular degeneration in older adults is by far the leading cause of CNVM.

Diabetes is not a cause of CNVM. In a child, the most likely causes are diseases/conditions that disrupt the integrity of the RPE: eye trauma; ocular histoplasmosis (a fungal condition seen mostly in the Ohio River Valley and occasionally elsewhere=–my wife developed 3 CNVMs at ages 18, 25 and 33 from this); extremely high amounts of nearsightedness (nearsightedness is often caused by elongated eye balls, elongation that can stretch and crack the RPE); angioid streaks (a condition causing cracks in Bruch’s membrane and related to systemic collagen diseases like pseudoxanthoma elasticum and Paget’s disease); previous history of retinal scarring from eye diseases like toxoplasmosis.

Laser treatment is often used if the CNVM is outside of the fovea (the point where incoming light is focused on the retina). If your daughter’s vision in the affected eye is still good, the CNVM is likely outside of her fovea. For CNVM under or near the fovea, laser causes a permanent, central blind spot that diminishes vision, so many retinal specialists are now performing sub retinal surgery to remove the CNVM, in hope of minimizing vision loss. Some pharmacological medicines have been tried, mostly with limited success. As for laser treatment, the common use of photodynamic therapy (PDT) has resulted in much better outcomes for some patients (the patient receives an injection of dye that specifically targets CNVM and is activated by the laser to destroy abnormal blood vessels).

Make sure your child is being seen by a retinal specialist, and ask him/her about the various treatment strategies I have outlined above. Some specialists have much more experience than others with particular techniques, especially sub retinal surgery, so ask about this; great specialists are never offended by such queries.

PC