Cotton Wool Spots
|Cotton Wool Spots|
|Classification and external resources|
In otherwise healthy patients, the observance of a cotton wool spot is not considered normal. A signle cotton wool spot in one eye can be the earliest ophthalmoscopic finding in diabetic or hypertensive retinopathy. In a series of patients who had cotton-wool spots and no known medical history, diastolic blood pressure equal to or greater than 90 mmHg was detected in 50% of patients, and an elevated blood sugar was found in 20% of patients. (1, 2, 3)
Can be categorized into:
- Ischemic : hypertension, diabetes, ocular ischemic syndrome, retinal vein occlusion, anemia, hyperviscosity state, hypercoagulable state, radiation, acute blood loss.
- Immune and inflammatory conditions: systemic lupus erythematosus, dermatomyositis, scleroderma, polyarteritis nodosa, giant cell arteritis.
- Infectious: HIV retinopathy, cat-scratch disease, rocky mountain spotted fever, leptospirosis, onchocerciasis, bacteremia, fungemia.
- Embolic: carotid emboli, cardiac emboli, cardiac valvular disease, endocarditis, rheumatic heart disease, deep venous emboli, Purtscher-like retinopathy, foreign-body emboli.
- Neoplastic: lymphoma, leukemia, metastasis.
- Medication induced: interferon retinopathy.
- Miscellaneous: trauma, epiretinal membrane, high-altitude retinopathy, papilledema, papillitis, Purtscher retinopathy.
- Idiopathic. (2,3,4,5)
Cotton wool spots are believed to occur secondary to ischemia from retinal arteriole obstruction (5). However, factors responsible for focal interruption of axoplasmic flow in the retinal nerve fiber layer may result in similar intra-axonal organelle accumulations (6).
The histological hallmark of cotton wool spots is considered by many authors to be cytoid bodies. They are named cytoid bodies because they look like cells, however they are eosinophilic segments of ganglion cell axons that are swollen because of defective axoplasmic flow. Cytoid bodies are usually packed with accumulations of mitochondria and other intracellular material (7,8).
On ophthalmic fundus exam, cotton wool spots may appear as small, yellow-white (or grayish-white), slightly elevated lesions, which look like clouds with a fimbriate border in the superficial retina. Usually they are less than 1/3 disc areas in diameter, and are commonly found in the posterior pole of the funds (5).
Cotton wool spots in general are visually asymptomatic, however, a patient may present with vision loss if the fovea is involved (5). Systemic symptoms of the underlying etiology may be present.
Diagnosis is usually achieved by a complete ocular examination, including a detailed dilated fundus exam. However, fluorescein angiography may reveal areas of capillary nonperfusion near cotton wool spots (1). On the other hand, additional work up may be needed to detect the underlying etiology.
Differential diagnosis of other yellow-white retinal lesions may include: myelinated nerve fibers, hard exudate, retinal infiltrate, retinal drusen, chorioretinal atrophy, intraluminal plaque and early endogenous chorioretinitis (9).
Work up and treatment are directed towards the underlying etiology. Cotton wool spots classically disappear in 6–12 weeks, however in diabetic retinopathy they may persist for longer (1, 5).
1- Adam T. Gerstenblith, Michael P. Rabinowitz. Wills Eye Manual, The: office and emergency room diagnosis and treatment of eye disease, 6th edition. Lippincott Williams & Wilkins, 2012.
2- Brown GC, Brown MM, Hiller T, Fischer D, Benson WE, Magargal LE. "Cotton-wool spots." Retina. 5, no. 4 (Fall-Winter 1985): 206-14.
3- Arroyo, ￼ Jorge G. "Cotton-Wool Spots May Challenge Diagnosis ." Review of ophthalmology, 2004: 111-114.
4- Arroyo JG, Irvine AR. "Retinal distortion and cotton-wool spots associated with epiretinal membrane contraction." Ophthalmology 102 (1995): 662-8.
5- Purnima S. Patel, SriniVas R. Sadda. "Retinal Artery Obstructions." In Retina (Fifth Edition), by Stephen J. Ryan, 1012-1025. Elsevier Inc., 2012.
6- D. McLeod, D. McLeod, E. M. Kohner and A. C. Bird. "The role of axoplasmic transport in the pathogenesis of retinal cotton-wool spots." Br J Ophthalmol 61 (1977): 177-191.
7- McLeod, D. "Why cotton wool spots should not be regarded as retinal nerve fibre layer infarcts." Br J Ophthalmol. 89, no. 2 (2 2005): 229–237.
8- Jr, Ralph C. Eagle. Eye pathology an atlas and text . 2nd edition. Philadelphia: Lippincott Williams & Wilkins, 2011.
9- The Eyes Have It: Yellow-White Things in the Retina. http://www.aao.org/theeyeshaveit/optic-fundus/yellow-white.cfm (accessed 11 02, 2014).