Which of the following is NOT a major etiology of a blue sclera?

• A. Minocycline
• B. Scleromalacia perforans
• C. Osteogenesis imperfecta
• D. Digitalis

Answer: (D)

Blue sclera happens when the sclera becomes unusually thin or accumulates pigment, allowing the underlying tissue to influence its color. The best-known causes are conditions that thin or pigment the sclera: a collagen disorder like osteogenesis imperfecta weakens and thins the sclera, making it appear blue; inflammatory thinning from scleritis can produce a similar blue hue known as scleromalacia perforans; and long-term minocycline use can lead to pigment deposition in the sclera, giving a blue-gray appearance. Digitalis, by contrast, is not associated with scleral thinning or pigment change. Its ocular associations are typically manifested as color vision changes (xanthopsia) and other toxicity effects, not blue sclera. So digitalis is not a major etiology of blue sclera.