This striking image of a peripheral retinal disease taken by the Optos 200 degree camera shows non-perfusion of retinal arterioles in the far periphery, with arteriolar-venular anastomosis and the beginning of neovascular proliferation.
At first glance, you may have been thinking it is diabetic retinopathy. However, this patient is not diabetic. She has sickle cell disease, which is a genetic disease characterized by sickle-shaped red blood cells which block capillaries and restrict blood flow.
This eye is beginning stage III of proliferative sickle retinopathy. Stage II is characterized by A-V anastomosis, with non-perfusion beyond the areas of anastomosis. Stage III is characterized by neovasularization that eventually results in vitreous hemorrhage and/or retinal detachment if not treated. Laser photocoagulation is a common treatment.
An anastomosis is a connection between two tubular structures.
Click here for more images in higher resolution, including a color image showing "silver-wire" appearance of the damaged arterioles.
Click here for more information on the ophthalmic manifestations of sickle cell disease.
Optic nerve head drusen: A tale of two images.
Which of these autofluorescence (FAF) images is of an optic nerve that does not have optic nerve head drusen? The answer may surprise you.
The correct answer is that both optic nerves have optic nerve head drusen. It appears that the nerve on the left side does not have drusen because the FAF has failed to pick up the drusen, probably because the drusen is buried too deeply in the nerve head tissue.
How do we know that the optic nerve on the left has drusen? It can be detected by Bscan ultrasonography, which is the “gold standard” in optic nerve head drusen detection.
That brings up an interesting question. What is the “failure rate”, or “false negative” rate for FAF regarding ON drusen detection? Are there any other imaging techniques that have a better “detection rate” than FAF? Someone should study that! Yes, you guessed it, someone did study that.
Gili et al* studied the sensitivity and specificity of the following imaging modalities with regard to detecting optic nerve head drusen, with the following results.
Autofluorescence: 88% sensitivity, 100% specificity
Red filter: 80% sensitivity, 97% specificity
Green filter: 71% sensitivity, 97% specificity
Color photo: 66% sensitivity, 100% specificity
Autofluorescence had the best results, but you will still miss the drusen (false negative) about 12% of the time, which means a negative result should have a Bscan performed. Also, with FAF, you are unlikely to get a false positive reading (100% specificity).
*Sensitivity and specificity of monochromatic photography of the ocular fundus in differentiating optic nerve head drusen and optic disc oedema. Pablo Gili, Patricia Flores-Rodríguez, Julio Yangüela, Javier Orduña-Azcona, María Dolores Martín-Ríos. Graefe's Archive for Clinical and Experimental Ophthalmology March 2013, Volume 251, Issue 3, pp 923-928
Branch vein occlusion. Includes color, mid-phase fluorescein angiogram, and late-phase FA. Taken with Optos wide angle camera at 200 degree setting.
Asteroid hyalosis. The color images shows the small refractile bodies floating in the vitreous. Notice that the fluorescein angiogram filters "see" through the condition, revealing a good view of the posterior pole. Taken with the Optos wide angle camera at the 100 degree setting.