A lump on the eyeball may be either a pingueculum or a pterygium, explains Summit Medical Group. It may also be indicative of eye cancer, notes Bupa.
Both pingueculae and pterygia are types of small growths that occur on the conjunctiva, which is a clear membrane that lines the white portion of the eyeball and the underside of the eyelid, notes Summit Medical Group. A pingueculum may be clear, or it may have a yellowish pigmentation. This type of eye bump occurs most frequently on the side of the eye nearest to the nose. A pterygium contains small blood vessels and can cover a portion of the clear layer on the front of the eye, called the cornea, if it grows large enough.
Potential causes of pingueculae and pterygia are exposure to ultraviolet rays, wind, dust and harmful chemicals, according to Summit Medical Group. They usually do not produce any symptoms and do not require treatment; however, they may cause redness, burning, itching, blurry vision, eye watering, dry eyes or a gritty sensation. If a pterygium grows large enough to affect vision, it may require surgical removal.
Eye cancer sometimes does not produce any symptoms, making it important to receive regular eye exams, according to Bupa. Some potential symptoms are vision impairment, a dark spot on the iris of the eye, a bulging eyeball, watering and seeing spots or light flashes.