Pinguecula

Etiology

The risk factors for the progression of pinguecula include exposure to ultraviolet light, trauma, wind, dust, sand, working outdoors for a long duration, and advancing age.[1] It occurs more frequently with age, and it is commonly seen in males most likely due to occupational exposure to sunlight or ultraviolet light. Almost all individuals show some evidence of pinguecula in their 80s.

Contact lens wear is an additional risk factor for the development of pinguecula. The cause for nasal predominance could be due to the actinic damage which occurs in this area because of reflection from the side of the nose.[2] The grade of pinguecula was higher in contact lens wearers than in non-contact lens wearers. However, it was higher in the hard contact lens wearers than soft contact lens wearers. Constant friction and inflammation of the conjunctiva caused by the contact lens edge may be responsible for the early onset of pinguecula in contact lens wearers.

Gaucher disease may be associated with pinguecula that is pigmented (brown) and triangular. Histology of such lesions reveals Gaucher cells (lipid-laden macrophage). Other lysosomal storage disorders can also have pinguecula.

Epidemiology

The prevalence of pinguecula is variable from region to region. Prevalence can range from 22.5% to 97%.[3] Pinguecula is a benign lesion. It is a grey white-yellow mass on the bulbar conjunctiva. Pinguecula does not have any sex predilection, it equally affects males and females. Similarly there is no racial predilection.

Histopathology

Pingueculae are usually well-defined nodular lesions. Histologically, the epithelium is normal, thinned, hyperkeratotic, or hyperplastic. In patients with brown or black skin, epithelial racial melanosis will be evident. The substantia propria exhibits basophilic staining on hematoxylin and eosin staining, termed elastotic degeneration. This elastotic degeneration consists of material that stains elastin but is not degraded by elastase. Sometimes it is associated with fat or calcified globules. In a pinguecula, the elastotic degeneration is nodular. Histologically pinguecula is analogous to pterygium, except for the lack of vascularisation and corneal involvement.[4]

A study localized advanced glycation end (AGE) products in the subepithelial amorphous deposit in pinguecula, which may denote the severity of exposure to ultraviolet light or the reduced levels of anti-oxidants.[5]

History and Physical

Pinguecula is a benign lesion. It is a grey white-yellow elevated round mass on the bulbar conjunctiva. It usually occurs within the interpalpebral conjunctiva, para-limbal zone at 3 o'clock, or 9 o'clock position. But, it has a predilection for the nasal part of the bulbar conjunctiva. It appears to be a precursor of pterygium, which may encroach onto the cornea. However, the relation of pinguecula and pterygium is controversial, and the progression of pinguecula to pterygium has come into question.

Pinguecula does not affect visual acuity. Though it is asymptomatic, it causes cosmetic complaints. However, if it is inflamed, it is known as pingueculitis. When a  pinguecula is inflamed,  the dilated blood vessels release histamine,  serotonin,  bradykinin, and prostaglandins to result in the symptoms of pingueculitis. The surface of the conjunctiva overlying the pinguecula will interfere with the normal spreading of the tear film. Thus dry eye symptoms such as burning sensation, itching, and foreign body sensation occur. Dellen may appear near the pinguecula. Tear break-up time may diminish in patients with pinguecula.

Evaluation

No laboratory investigations are required to diagnose pinguecula. Recently optical coherence tomography-angiography has been used for visualizing the anterior segment of the eye. It has been seen that changes in the vascularization of pinguecula conjunctiva were not obvious. There was no significant difference in blood vessel density between the normal conjunctiva and the pinguecula.[6] The anterior segment optical coherence tomography shows the morphological patterns of pinguecula. The anterior segment of optical coherence tomography of pinguecula revealed wedge-shaped masses. They are similar in configuration to the anterior segment optical coherence tomography pattern of the pterygium. In pinguecula, the wedge-shaped mass stopped at the limbal region and did not elevate the corneal epithelium. A clearly defined line of separation was present between the pinguecula and the underlying scleral tissue. The thickness of the pinguecula is assessable using anterior segment optical coherence tomography.[7]

Treatment / Management

Providers should advise patients with pinguecula to safeguard their eyes from ultraviolet light, wind, and dust.[8] The eye should be protected by sunglasses and wide-brimmed hats to avoid sunlight exposure during the day. These are effective strategies for minimizing sun damage.[9] A wide-brimmed hat or visor can reduce the amount of ultraviolet light reaching the eye by up to 30%.[10] Polycarbonate and high index lenses block all ultraviolet-A and ultraviolet-B up to 380 nm. CR- 39, a plastic polymer used in the manufacture of eyeglass lenses, blocks ultraviolet-B light. However, the crown glass used in optical glasses does not have ultraviolet–B blocking properties. Transition lenses offer 100% ultraviolet light protection. Polarized lenses offer additional protection, and some contact lenses provide ultraviolet light protection as well.[11] Treatment for pinguecula is rarely required. Artificial tears may be useful in mild cases of dryness or foreign body sensation. If inflammation is more severe, a short course of topical steroids or topical antibiotic–steroid in tapering dose may be indicated. Topical non-steroidal anti-inflammatory drugs are also effective in treating pingueculitis. Cold compresses may help patients with inflamed pinguecula.(B2)

Surgical excision is considered only for cosmetic reasons. Surgical excision of the pinguecula is possible under topical anesthesia. Following the excision, the bare sclera can be closed with a conjunctival autograft. Topical antibiotic-steroid eye drops are prescribed during the post-operative period. It is a final resort either in cases of chronic persistent irritation when the treatment, as mentioned above, has failed, and when interference with contact lens wear occurs. Excision should be followed by histological evaluation; this is to exclude malignancy when the pinguecula is atypical in either location or appearance.[12](B3)

Argon laser photocoagulation is an alternative to standard surgical excision for pinguecula. It is a safe method for removing a pinguecula for cosmetic purposes. It provides control of the extent and depth of removal of tissue. Thus conjunctival defects and complications are reduced. Argon laser photocoagulation involves the use of argon green laser (wavelength 514 nm). A topical anesthetic drop is instilled into the conjunctival sac before the procedure. High power laser is used for thick pinguecula, whereas low power laser is appropriate for thinner pinguecula. Usually contiguous, non-overlapping laser spots of 200 microns are used (laser duration 100 milliseconds (ms), power 300 to 360 mW, argon green laser).[13] The laser was applied only over the pinguecula and to the conjunctival tissue alone, sparing the tenon capsule and sclera.[13] A case report used the following parameters- 532 nm green laser, spot size 50 microns, laser power 350 to 400 mW, and laser duration 100 ms.[14] In this report, the first two perpendicular grooves were made over the pinguecula with laser, and then the entire lesion was photo-coagulated.[14](B2)

Following argon laser photocoagulation, the conjunctival defects are allowed to re-epithelialize. During the post-operative period, patients should receive a topical antibiotic steroid eye drop.[13](B2)

There were no significant differences between surgical excision and argon laser photocoagulation in cosmetic outcomes. Surgical excision of symptomatic pinguecula with conjunctival autograft with fibrin glue may improve cosmesis. It also improved dry eye symptoms.[15]

Differential Diagnosis

Differential diagnoses of pinguecula are as  follows:

1. Pterygium: It gradually progresses to encroach the cornea. When it involves the pupillary area, it affects the visual acuity of the patient, or it may reduce the uncorrected visual acuity due to induced astigmatism even when the pterygium does not involve the pupillary area.
2. Conjunctival foreign body: Conjunctival foreign body is recognizable by slit-lamp examination of the eye—the patient complaints of foreign body sensation and watering of the eye surface. The conjunctival foreign body is removable with a sterile disposable needle.
3. Phlycten: Can occur anywhere on the conjunctiva. It appears as an elevated summit and stains with fluorescein dye. The phlycten is due to a hypersensitive reaction to an endogenous allergen. It is usually associated with Mycobacterium tuberculosis.
4. Nodular Scleritis: Nodular scleritis is associated with severe pain. Scleral inflammation correlates with a distinct nodule in nodular scleritis.
5. Limbal dermoid: The limbal dermoid is a pale yellow mass. The common location is the inferior temporal limbus. It may involve the conjunctiva and cornea.
6. Conjunctival malignant melanoma: Conjunctival malignant melanoma is a rare malignant tumor of the conjunctiva. It is visible as a raised elevated pigmented lesion associated with a feeder vessel.
7. Conjunctival epithelial inclusion cyst: Conjunctival epithelial inclusion cyst is a cystic swelling filled with clear fluid. Patients are usually asymptomatic.
8. Ocular surface squamous neoplasia: Ocular surface squamous neoplasia is a common malignancy of the ocular surface. Patients complain of redness and foreign body sensation. They usually present in the interpalpebral conjunctiva. It gradually approaches the limbus. It is usually associated with a sentinel vessel.
9. Conjunctival naevus: Conjunctival naevus is a benign lesion of the conjunctiva. They are flat pigmented lesions.

Staging

Pinguecula is divided into three grades as follows:

• Grade P(0): no pinguecula.
• Grade P(1): mild or moderate pinguecula-yellowish flat and white or slightly elevated lesion.
• Grade P(2): severe pinguecula-highly vascularised and elevated lesion.[16]

Prognosis

Pinguecula is generally an asymptomatic lesion. As already described, it is a benign lesion so it has a good prognosis. It only causes cosmetic problems. It can gradually increase in size or progress to pterygium over time.

Complications

Usually, pinguecula is asymptomatic. Surgical excision should be a consideration if the patient is symptomatic or has recurrent episodes of pingueculitis. Complications may arise after the excision of the pinguecula. The complications include the recurrence of pinguecula and pigmentary changes at the site of removal.