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| REVIEW ARTICLE |
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| Year : 2019 | Volume
: 1
| Issue : 1 | Page : 9 |
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Pinguecula
Eduardo Arenas1, Gioconda Armas1, Alfredo Ramirez2
1 Department of Ophthalmology, El Bosque University, Bogotá, Colombia
2 Department of Ophthalmology, Clínica Oftalmológica De La Selva, Tarapoto, Perú
| Date of Web Publication | 26-Sep-2019 |
Correspondence Address:
Dr. Eduardo Arenas
Carrera 21 No. 100-20 Piso 7, Bogotá
Colombia
 Source of Support: None, Conflict of Interest: None
DOI: 10.4103/2219-4665.267880
Pinguecula is a common disease in tropical countries however there are not so many published articles regarding its aetiology, signs , symptoms and management . It seems that Ultraviolet rays play an important role and it is one of the reasons that explain the prevalence in zones near the equator. Pingüeculas behave different in the nasal than in the temporal side playing an important role in the development of pterygium which explains the high incidence of its nasal location. Regarding treatment and management , there are different approaches that will discussed in this mayor review.
Keywords: Corneal degeneration, ocular surface, pinguecula
How to cite this article:
Arenas E, Armas G, Ramirez A. Pinguecula. Pan Am J Ophthalmol 2019;1:9 |
| Introduction | |  |
Pinguecula, from the Latin “pinguis,” which means “fatty,”[1] is a localized yellowish thickening of the conjunctiva, prevalent in young adults living in the tropics. The condition often goes unnoticed but could increase progressively leading to chronic symptoms[2] or could develop into a pterygium, resulting in particular alterations to the cornea.[3] Reviewing the literature reveals that few authors have discussed the clinical management of patients with pinguecula, even though there is a clear link between the incidence of this disorder and repeated exposure to sunlight in areas, with high levels of ultraviolet (UV) radiation. This is, without doubt, one of the main causes of the appearance of such injuries in the conjunctiva, which would give rise to the primary pinguecula.
| Definition | | |
Pinguecula is a lesion that resembles a yellow spot or bump in the conjunctival surface, which is located in the interpalpebral region and appears first in the temporal side and later in the nasal side. It is characterized by an avascular central elevation surrounded by capillaries, and in the nasal part, a similar lesion more punctate at mid-distance between the caruncle and the corneal limbus, in the axis of 180°.[4] Depending on the size and elevation of the lesions, the signs and symptoms increase, requiring ophthalmological care.
| Etiology | | |
According to different authors, the main cause of pinguecula formation is due to the influence of UV rays on individuals living in areas with greater sun exposure.[5] In 1951, Bartlett studied the disease and found that people in Mexico were particularly susceptible.[6] In addition, they estimated a prevalence of 50% in adults living in countries close to the equator. Other authors, such as Panchapakesan et al.[7] and Mimura et al.,[8] mention a prevalence that may vary between 22.5% and 70% in intertropical countries.
| Physiopathology | | |
In 1978, Arenas published a paper explaining how UV radiation could cause pinguecula and why this is more symptomatic and aggressive when it is localized on the nasal side of the eye.[9] It was explained that the temporal side of the eye is more exposed to sunlight than the nasal side, which is protected by the supraorbital notch and the nose. UV rays hit the outer or temporal side of the eye and by dispersion throughout the Bowman's layer and the Descemet membrane, emerging exactly 3 mm away from the nasal limbus producing a chronic subconjunctival burn in a punctual site, that initiates an inflammatory reaction of the Tenon's capsule. This gives rise to the nasal pinguecula, and the elevation then initiates a Dellen phenomenon, causing the conjunctiva to progressively cover the adjacent dry spot. This slowly progresses toward the limbal area initiating the classical pterygium, which continues growing to the center of the cornea[10] [Figure 1]. The mechanism of energy growth was described by Barraquer in 1964,[11] who explained why the lesion tends to grow because of this phenomenon. Fuchs in 1892[12] explained the important role of UV rays, as an etiological factor in the formation of these injuries.[13]
This type of pinguecula of solar origin is defined as primary because there are cases in which it can be originated by the presence of chronic irritations or the inclusion of foreign bodies that would be named secondary pingueculas.[14]
Secondary pinguecula
Some authors mention that there may be other reasons for the appearance of pinguecula in people exposed to foreign bodies, as sometimes happens with workers handling welding equipment. This was first described by Karay and Horiguchi[15] and by Norm, in Norway.[16] These conditions often occur as a consequence of foreign objects being introduced into the conjunctiva and producing a focalized inflammatory reaction. In Nigeria, Iyiade studied 405 welders, 50% of whom developed different types of pinguecula.[17] Other authors have also reported similar findings.[18]
In 1937, Dimitri proposed a different theory for secondary pinguecula; his theory associated the exposure to dust and other foreign objects with the condition.[19] Other authors have reported the existence of a link between the condition and occupations with a greater risk of exposure to these foreign objects as has been observed in motorcyclists.[20],[21]
| Prevalence | | |
Asokan studied the incidence of the disease in the South of India and found a prevalence of 11.3%.[22] Rezvan studied its frequency in Iran and found a prevalence of 61%.[23] Le performed a study in Shanghai[24] and found a prevalence of 75.57%. Viso also made a study in Spain and found a prevalence of 47.9%.[25] They also found a prevalence of 5.9% for the pterygium. In Teheran, the prevalence of pinguecula was 22.5%,[25] and in Nigeria, Iyiade, found a prevalence of 50.1% (much larger than pterygium 17.5%).[17]
In Latin America, there are very few studies available on the prevalence of this disorder. In Colombia, a prevalence of 11% was found in natives of the Riosucio region and 7% in the Choco region. This study also found a prevalence of 14.7% in the Afro-Colombian population.[26] Finally, Esposito found a prevalence of 32.1% in Patagonia (Argentina).[27]
As mentioned before, the prevalence of pinguecula is in areas with greater exposure to UV radiation.[28],[29] However, other studies such as those of Nakaishi, determined that there may be other factors creating a close link between occupation and the type of work and UV exposure for the prevalence of pinguecula.[30] Taylor found a higher prevalence in motorcycle police officers of 37.7%.[31] In Colombia, Cortes found a prevalence of 37.4% in workers exposed to cement dust.[32]
The pinguecula is also more prevalent in aging populations.[33] Other authors found that the prevalence was directly linked to age in people over 40.[14],[34]. Le found this in people over 50.[25] Mimura found that people aged 40 and above are at a higher risk of developing the condition.[35] Regarding gender, the incidence was higher in men tahn in women.[17],[23],[25] Other authors also found increased prevalence in rural areas and no differences among genders.[27]
Dysfunction of the tear film is another risk factor associated with the formation of pinguecula. Balogun found an association between alterations of the lacrimal film and the formation of pterygium, but not with pinguecula in breakup time (BUT) measurement.[36] Other authors, such as Oguz, showed that the BUT is shorter in people with pinguecula than in healthy people due to an irregularity in the ocular surface, demonstrating that if the tear layer is thinned by an irregularity located in the epithelium of the surface. The flow of lipids will increase considerably and with it the possibility of a rapid and highly focalized contamination of lipids on the mucus layer, causing a hydrophilicity of the tear film that will break immediately on these hydrophobic surfaces, destabilizing the tear film.[37] Hashemi et al.[38] and Siak et al.[39] both found, in contrast to the pterygium, a statistically significant relationship between the dysfunction of the Meibomian gland More Detailss and pinguecula, because it can alter the function of the lacrimal layer producing an increase in the dysfunction of Meibomian glands.
Regarding diabetes, smoking, and alcohol consumption, studies show a relationship between these diseases and the appearance of pinguecula,[40] while Asokan, in South India, found no association between these diseases and the appearance of pinguecula.[22] Ozer studied the link between pinguecula and thyroid orbitopathy, finding a higher prevalence in the group with thyroid orbitopathy.[41]
The use of contact lenses may be associated with the appearance of pinguecula produced by a microtrauma mechanism. Mimura found a higher prevalence in a group of patients using rigid contact lenses.[42] In another study by the same authors, they found an associated risk between conjunctivochalasis and pinguecula, but this was challenged by Hashemi who found an inverse link between these two entities and blepharitis.[43]
Some authors have found a link between pinguecula and systemic diseases such as psoriasis.[44],[45] Patients with erythrodermic psoriasis and Sjogren's syndrome are even more at risk.[46]
| Signs and Symptoms | | |
Most publications describe pinguecula as asymptomatic;[47] however, there are patients reporting symptoms such as the sensation of a foreign body, tearing, pain or discomfort,[48],[49] causing reddening, itching, and a sprain sensation.[50] Some studies suggest that pinguecula causes instability of the tear film,[51] though it is not clear so far if dry eye causes changes in the conjunctiva and later formation of the pinguecula, or if the pinguecula actually causes instability of the tear film.[52]
Changes in visual acuity are seldom associated with pinguecula being a casual finding in patients presenting symptoms of ocular surface disturbance.[3] In the Tehran Eye Study, Fotouhi found that 11.5% of people with pinguecula showed <20/40 visual acuity, compared to 4.3% of people without. However, when age was accounted for in this study, the correlation disappeared.[27] Pham et al.[53] and Lim et al.[54] found a significant risk of developing cataracts in patients with pinguecula.
The diagnosis of pinguecula is fundamentally clinical and is made based on the medical history and ocular examination. Kim analyzed the autofluorescence of pinguecula using a cobalt-blue filter and an additional yellow filter on a slit-lamp and found two patterns: (1) round and elevated lesions with tortuous vessels and no vessel invasion and (2) flat and bizarre lesions with vessel invasion.[55] Utine also analyzed the autofluorescence of pinguecula, but they used a scanning laser ophthalmoscope. The technique allowed them to distinguish pinguecula from other lesions and they obtained “well-defined autofluorescence” over a larger area than “the extent of visible pinguecula.”[56] Ip found Fuchs spots to be an early sign of UV radiation damage on the conjunctiva. These spots are precursors of lesions such as pinguecula and pterygium and are found in 95% of eyes with pinguecula and also in the contralateral eye.[14] Nanji et al.[57] and Demirci and Steen[58] used high-resolution optical coherence tomography and found similarities between pinguecula and pterygium. They both showed mild epithelial hyperreflectivity and slightly engrossed normal epithelia. In addition, the authors found a mass of dark, sub epithelial tissue near the limbus in patients with pinguecula.
| Management | | |
Many authors agree that pinguecula does not require treatment, unless the patient shows symptoms of inflammation.[59] In these cases, the use of lubricants and topical corticosteroids is recommend.[36] In 1997 and 1999, Frucht compared the effect of topical formulations in groups treated with 0.1% topical indomethacin and with 0.1% topical dexamethasone phosphate against a group treated with a placebo. They found that in the groups treated with the topical formulations, most of the symptoms improved.[60] In 2014, Arenas proposed a new local therapy for symptomatic pinguecula. The treatment consisted in the application of depot betamethasone directly into the lesion, with positive results and improvement in signs and symptoms.[61]
Ahn compared surgical management of pinguecula with the use of argon laser therapy. They found that laser therapy produced comparable results to surgical treatment. They also studied BUT a year after treatment and found improvement of symptoms in patients treated with laser therapy.[62] Napoli also used laser therapy and highlighted the safety of the procedure regarding bleeding compared with surgical management. In addition, Shin reported the effectiveness of laser therapy because it avoids subconjunctival hemorrhage[63] without causing subconjunctival hemorrhage. Jung also demonstrated the esthetic result of excision of the pinguecula with conjunctival autograft, a very safe and highly effective procedure, with regression of vascularization.[64]
| Histology | | |
Different histological changes are observed in pinguecula including atrophy, hyperplasia, metaplasia, dysplasia, subepithelial hyalinized collagen, and elastosis.[65],[66] Peiretti suggests the hypothesis that this disorder has a proliferative component, demonstrating an overexpression of two genes associated with the metabolism of low-density lipoprotein-receptor cholesterol, and HMG-CoA-R RNAm, in comparison with a healthy conjunctiva,[67] even in the presence of metallothionein.[68] Alterations to gene p53 are also suspected to cause the disorder. Authors have suggested how UV rays can cause mutations in gene p53 that alter the metabolism of cholesterol, leading to the disorder.[69] Hyung found “depositions of eosinophilic and amorphous materials in the subepithelial layer of the conjunctiva and degeneration of the collagen fibers in the conjunctival stroma” via autofluorescence imaging.[55] Chen determined that the pinguecula is an abnormal differentiation condition characterized by squamous metaplasia with proliferation toward the limbal border.[70] The progression from pinguecula to pterygium was documented by Chapman-Smith and others from remoter times, suggesting that pinguecula is a condition of abnormal differentiation characterized by squamous metaplasia and proliferation of cells toward the limbal ring.[71] Degenerative changes in the components of both disorders are believed to lead to inflammation; the lesion can result from a combination of elastodysplasia and posterior elastodystrophy.[72]
| Conclusions | | |
Few authors have addressed the prevalence of pinguecula in different parts of the world where its incidence is high. Chronic symptoms, unesthetic appearance, and the problems it represents for users of contact lenses, suggest more attention is needed for this condition.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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