They include a growing range of treponemal and nontreponemal assays. Treponemal tests are more specific, and are positive for any one who has ever been infected with yaws; they include the Treponema pallidum particle agglutination assay. Nontreponemal assays can be used to indicate the progress of an infection and a cure, and positive results weaken and may become negative after recovery, especially after a case treated early. They include the venereal disease research laboratory (VDRL; requires microscopy) and rapid plasma reagin (RPR; naked-eye result) tests, both of which flocculate patient-derived antibodies with antigens.Serological tests cannot distinguish yaws from the closely related syphilis; no test distinguishing yaws from syphilis is widely available. The two genomes differ by about 0.2%. PCR and DNA sequencing can distinguish the two. There are also no common blood tests which distinguish among the four treponematoses: syphilis (Treponema pallidum pallidum), yaws (Treponema pallidum pertenue), bejel (Treponema pallidum endemicum), and pinta (Treponema carateum).Haemophilus ducreyi infections can cause skin conditions that mimic primary yaws. People infected with Haemophilus ducreyi lesions may or may not also have latent yaws, and thus may or may not test positive on serological tests. This was discovered in the mid-2010s. It seems that a recently diverged strain of Haemophilus ducreyi has evolved from being a sexually transmitted infection to being a skin ulcer pathogen that looks like yaws.Yaws has been reported in nonendemic countries.
It also appears that central serous retinopathy can be a result of a depression in a treated solar damaged eye.The duration of exposure necessary to cause injury varies with the intensity of light, and also affects the possibility and length of recovery. Diagnosis
A person with photic retinopathy may notice an impairment in their vision, for example a spot that does not go away after a reasonable recovery time, or blurring. They may also have eye pain or headaches. Vision impairment is usually in both eyes, but can be in just one. Impairment of a person with 20/20 vision usually ends up being about 20/40 or 20/60, but can be better or far worse.A doctor examining an eye with retinopathy may be able to see no signs at all, or a slight macular edema, which is a sort of blister on or under the macula, an oval colored spot normally visible to an eye doctor on each persons retina. But while even that edema goes away, within a few days the patient will generally develop a discoloration of the retina at the injured point, often yellow or white, turning red over the next few weeks. Treatment
Photic retinopathy generally goes away on its own over time, but there is no specific treatment known to be reliable for speeding recovery. One path sometimes attempted, which has unclear results, is to treat the initial macular edema with corticosteroids.