Pterygium
El Pterygium or fleshy eye is an abnormal growth of the conjunctiva (transparent membrane of the eye) in the direction of the cornea that, sometimes, can get to cover. As usual the pterygium appears in the nasal or inner swim of the eye, although it can also appear on the outer side.
El pterygium treatment covers from lubricating eye drops in the more incipient states to Pterygium surgery in more advanced cases.
Pterygium
El Pterygium or fleshy eye is an abnormal growth of the conjunctiva (transparent membrane of the eye) in the direction of the cornea that, sometimes, can get to cover. As usual the pterygium appears in the nasal or inner swim of the eye, although it can also appear on the outer side.
El pterygium treatment covers from lubricating eye drops in the more incipient states to Pterygium surgery in more advanced cases.
What is the pterygium?
El pterygium, also written sometimes as pterygium, is a benign neoplastic lesion characterized by an invasive local fibrovascular growth of the conjunctiva towards the cornea (1)
El the origin of this proliferative tissue is in the basal epithelial stem cells of the limbal bed (CMEL) that they are activated and transformed into connective tissue (2)
Causes of the pterygium
It has been shown that main activating factor that causes pterygium is ultraviolet radiationTherefore, its incidence is much higher in the countries of the equatorial strip with a high rate of insolation (3-6). Although it has been proposed once, there does not seem to be a genetic predisposition to suffer from pterygium (7)
Solar UV radiation would act on the temporal area of the eye, spreading through the cornea, such as through a double mirror formed by the epithelium and endothelium reaching the nasal region with an enhancer effect of up to 20 times higher in the exit area, nasal, with respect to the entrance, temporary (8). Thus, the lesion begins in this nasal area, which is more protected from the sun, which seems a contradiction.
El The first effect of ultraviolet rays on the tissues is an elastic degeneration of the subconjunctival substantia propria.. UV activates fibroblasts that generate abnormal elastin that can no longer be degraded by elastase (9,10). The anomalous elastin will accumulate until it gives an image of rounded lesion, over-raised y yellowish in appearance located in the nasal area next to limbo, this is what we call pinguecula (Figure 3).
Together with this degenerative process, a inflammatory reaction responsible for the appearance of blood vessels in the subconjunctival space, surrounding the lesion and forming a triangular-shaped fibrovascular bundle with vertex towards the cornea, what will lead to pterygium.
Histochemical and molecular biology studies show that in the pterygium, ELSCs express the mutation of a tumor suppressor gene that causes the presence of the p53 protein (11,12), a common marker in various human cancers and in actinic lesions of the pterygium. skin (13), which suggests that Pterygium would be a tumor-like proliferative disorder. The p53 gene is related to the mechanisms of programmed cell death.
Ultraviolet rays act on CMEL causing a mutation in the gene responsible for the synthesis of the p53 protein, the gene loses the ability to act as a transcription factor, resulting in an uncontrolled cell proliferation and a change for the signals that activate the growth factors and the cyclin pathway D1-Cdk4 (11,12). The consequences of the p53 gene mutation is that CMELs grow out of control (14) become migratory and invade the cornea through the basement membrane (15), dragging conjunctival cells and inducing fibrovascular tissue formation at this level, due to to the increased levels of inflammation mediators, proliferative and angiogenic factors, as found in histopathological and histochemical analysis (16).
Ultraviolet rays act on CMEL causing a mutation in the gene responsible for the synthesis of the p53 protein, the gene loses the ability to act as a transcription factor, resulting in an uncontrolled cell proliferation and a change for the signals that activate the growth factors and the cyclin pathway D1-Cdk4 (11,12). The consequences of the p53 gene mutation is that CMELs grow out of control (14) become migratory and invade the cornea through the basement membrane (15), dragging conjunctival cells and inducing fibrovascular tissue formation at this level, due to to the increased levels of inflammation mediators, proliferative and angiogenic factors, as found in histopathological and histochemical analysis (16).
These studies reveal in turn that the changes occur in the "head" of the pterygium, the region that advances towards the cornea, being much lower in the rest of the lesion, a fundamental datum to have special care in the surgical treatment of the pterygium. The entire "head" must be removed well to eliminate the mediators responsible for the advancement of the pterygium, which cause frequent recurrences after surgery..
When the fibrovascular tissue reaches the cornea the balance between matrix metalloproteinase (MMPs) and inhibitors of these enzymes is upset. The concentration of MMPs (17) is increased, especially in the head of the pterygium, inducing changes in the collagen structure of the basement membrane of the corneal epithelium, the Bowmann and the corneal stroma. weakening of the collagen structure facilitating the penetration of the fibrovascular tissue from the limbus to the cornea (18). Once the barrier of the cornea is weakened, the advancement of fibrovascular tissue is produced by the presence of inflammatory factors, cytokines and proangiogenic factors (especially presence of VEGF) and fibroblast growth factors (especially TGF-Beta). Its identification opens a new path to the treatment of pterygium.
In summary, ultra-violet radiation and microtrauma induce a chronic inflammatory process, with loss of barrier function of corneo-conjunctival limbo. Fibrovascular proliferation occurs, remodeling of connective tissue, angiogenesis and corneal invasion.
Pterygium Surgery
El classic treatment is surgical type, that is, you have to make a pterygium operation with special attention to the corneal region, the head of the pterygium. When the size is small, after its removal, just suture the edges of the healthy conjunctiva but, when they are from larger size or type relapsing, a conjunctiva implant, amniotic membrane or cultured stem cells.
This procedure is effective in a high degree of cases but there is still a high percentage of recurrences that make a new surgery necessary. It is not well known cause of recurrences but everything suggests that a certain degree of inflammatory reaction persists and a bed in the limbus that facilitates the new fibrovascular proliferation and corneal invasionIn addition to the persistence of the causal factor, the ultraviolet radiation, thus It is necessary to assess these three factors.
There are many people who are reluctant to undergo pterygium surgery and that is why they ask themselves:how to eliminate pterygium without surgery? When he pterygium is small the ophthalmologist may recommend steroids to reduce inflammation or drops for pterygium.
The three key factors for the success of ptreigion surgery are:
Video operation of Pterigion step by step in Área Oftalmológica Avanzada
Before the surgery
Protection against ultra-violet radiation
In the first place it is obvious that we must protect the eyes against ultra-violet, Patients should be encouraged to avoid this type of radiation, either by reducing their exposure or by wearing protective goggles., taking care to choose the right frame and UV filter with sufficient power.
During surgery
Selective surgery and reconstruction of the conjunctiva
The third factor, avoid the recurrent pterygium, involves taking a series of surgical measures. The technique of removal must be careful, dissecting the entire Pterygium, body and head, the entire triangle must be removed. The body is made up of an altered conjunctival epithelium that should not be preserved and a fibrovascular connective tissue that must be completely removed.
La head of the Pterygium must be dissected in the cornea, reaching its deep planes and removing all of it. It is essential that the corneal and limbal surface is regular and smooth, since otherwise, we know that it is a factor that will facilitate the advancement of the fibrovascular tissue of the conjunctiva, initiating recurrence. For this it is necessary use instruments that “polish” the surface, a diamond dust bit, or the Barraquer wind turbine.
Once the abnormal tissue is removed we must assess the possibility of closing the edges of the healthy conjunctiva. If possible we use sutures that do not induce inflammation, such as nylon, since the usual ones such as vicryl, of the resorbable type, can facilitate fibrovascular neoformation. When the denuded area cannot be occluded by approximating the edges of the conjunctiva, a graft is necessary to ensure the barrier effect.
Whenever possible an autograft of conjunctiva from the same eye is preferable, generally from the superior temporal region and, if there is not enough tissue in that eye, it can be obtained from the contralateral eye, always taking care to obtain healthy limbic cells that guarantee the regeneration of the area. Another option is the implant of cultured stem cells exvivo and on support of amniotic membrane (22). The graft can sutured or fixed using adherent substances such as fibrin (tisucol TM).
After surgery
Inhibition of the local inflammatory reaction
The second factor, inflammatory reaction, must take preoperative, intraoperative and postoperative measures.
Before the intervention the administration of anti-inflammatory drugseither topical steroids or prior infiltration of anti-VGF. have been described good results with this maneuver, both in the incidence of recurrences and in recovery after surgery. At the intraoperative level, it is recommended apply drugs that inhibit fibroblastic proliferation, like Mitomycin C. Studies show the efficacy of this drug, its application at 0.02%, for 30 seconds, shows very good results (19). Other drugs such as Thiotepa or 5-Fluorouracil (20), have not shown the same level of efficacy.
In the postoperative period it is also necessary to control the inflammation, especially in the initial phases, for this reason it is necessary to administer topical steroids, even the instillation of Mitomycin C in the form of eye drops has been proposed in complex cases, where a possible recurrence is foreseeable. Maybe the The most recommended guideline at the present time in the prevention of recurrence or, when we see that it starts, it would be with anti-VGF infiltration in the risk area (21)
REFERENCES
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