Pinguecula (derived from Latin word pinguis, which means fat) represents an area of bulbar conjunctival thickening adjoining limbus in the palpebral fissure area. Pinguecula are less transparent than normal conjunctiva and often have a fatty appearance. They are usually bilateral, triangular, elevated, white to yellow in colour, horizontally oriented, and are located nasally much more often than temporally. They may also present on both the nasal and temporal conjunctiva in the eyes of some patients. Pinguecula does not cross the limbus, and current information suggests that pinguecula does not progress to pterygium and that the two are distinct disorders.
Pinguecula are associated with a two to three fold increase in incidence of age-related macular degeneration, possibly through a common light exposure effect (Pham TQ et al).
Degenerations of the conjunctiva are common conditions that, in most cases, have relatively little effect on ocular function and vision. These conditions increase in prevalence with increasing age as a result of past inflammation, of long-term toxic effects of environmental exposure, or of ageing itself. Conjunctival degenerations may be associated with chronic irritation, dryness, or previous history of trauma.
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Pinguecula are usually asymptomatic.
Pinguecula are associated only rarely with any symptoms other than a minimal cosmetic effect.
Ocular (eye) symptoms include:
Pinguecula remains relatively free from congestion and becomes conspicuous when the eye is inflamed. They may become red with surface keratinisation. When inflamed, the diagnosis of pingueculitis is given.
The causes of pinguecula are not known with certainty.
Pinguecula are more likely in males, welders and older individuals living in warmer climates. Pinguecula are more common than pterygium.
Evidence suggests its association with:
The diagnosis is usually clinical and may require slit-lamp biomicroscopy.
Pinguecula are characterised by elstotic degeneration of the collagen with hyalinisation of the conjunctival stroma, collection of basophilic elastotic fibers, and granular deposits.
The control of elastogenesis is seriously defective so that elastic fibers are abnormal in biochemical organisation. Normal assembly of elastic fibers is prevented due to marked reduction of elastic microfibrils. Limbal epithelial cell mutations at gene p53, probably due to ultraviolet irradiation, may be an early event in the development of pinguecula. The sub-epithelial dense concretions stain positively for lysozyme. Pinguecula may calcify with time.
Under electron microscopy, the granular material consists of hollow- centered microfibrils, which are elastic fiber precursors. The material is overproduced by numerous fibroblasts that are thought to be actinically activated by sunlight exposure.
Immunoassay suggests an abnormal epidermal differentiation due to a decline in the expression of Pax6, K19 keratin, and MUC5AC (a protein coding gene), but an associated increase in K10 and K14 keratin. There is also active proliferation of the squamous cells, as evidenced by positive expression of Ki67, P63, and K16 keratin.
Pinguecula may become inflamed due to dryness and irritation, resulting in so-called pingueculitis. The most common causes of such inflammation are:
The epithelium overlying a pinguecula can vary from atrophic and thinned to hyperplastic and thickened. Pinguecula are unlikely to undergo malignant conversion. However, a lesion that looks atypical should be approached with suspicion. Actinic keratosis, dysplastic changes, and even carcinoma can arise within the epithelium overlying a pinguecula.
Pinguecula may be differentiated from:
Management should be carried out under medical supervision.
Steroids or surgical excision are discouraged unless there is chronic irritation or interference with the use of contact lens.
Pinguecula may grow slowly over time but are associated with minimal ocular morbidity (a diseased state).
Potential possible complications of pinguecula are:
Prevention may include avoidance of ultraviolet-light exposure and use of ultraviolet-blocking spectacles.