A blue lesions on sclera ,what should it be?

Pigmented lesions that arise from the conjunctiva include nevus, complexion-associated melanosis (CAM), primary acquired melanosis (PAM), and malignant melanoma.1,2 All of these lesions arise from melanocytes. However, a number of other lesions have a similar appearance but a different source, such as pigment deposits from silver and iron.  

It is essential to differentiate these lesions. An undiagnosed melanoma, for instance, can be deadly. This review provides an overview of presentation and management of melanocytic conjunctival pigmented lesions.

hope that might helpful

Initial Workup  :

Medical history.

 need answer about the following questions : 1) their age when they first noticed the lesion, 2) their history of sun exposure, 3) their personal or family history of skin cancer, and 4) any recently noted changes in the appearance of the lesion.

Exam.

Features such as lesion color, thickness, and location are important in prognosis. Lesions on the bulbar conjunctiva are more common and apparent; they are also more easily detected by the patient than are those in the fornix.

Meticulous examination of the conjunctiva by slit lamp is key, as it is easy to miss a small lesion in the fornix or tarsus. Always evert the eyelids.

With regard to imaging, optical coherence tomography  OCT and ultrasound have been used to evaluate a variety of anterior segment lesions.3 OCT can be especially useful in differentiating amelanotic melanoma from ocular surface squamous neoplasia (OSSN). In OSSN, the epithelium is thickened, and there is an abrupt transition from the normal zone to hyperreflective thickened epithelium. In melanoma, the epithelium is usually thin, and a subepithelial lesion is present. Ultrasound can be used to assess the depth of the lesion and scleral invasion.