💎VVIP Kolkata Call Girls Parganas🩱7001035870🩱Independent Girl ( Ac Rooms Avai...
ptrigium.pptx
1. Pterygium
• Disease Entity
• Pterygium, from the Greek pterygos meaning “wing”, is a common ocular
surface lesion originating in the limbal conjunctiva within the palpebral
fissure with progressive involvement of the cornea.
• The lesion occurs more frequently at the nasal limbus than the temporal with
a characteristic wing-like appearance.
2. • Etiology
– The pathogenesis of pterygia is highly correlated with UV exposure.
– An increased incidence is noted in latitudes nearer the equator and
in individuals with a history of increased UV exposure (outdoor
work).
– Some studies have shown a slightly higher incidence in males than
females, which may only reflect a higher rate of UV radiation.
• Risk Factors
– UV radiation, proximity to the equator, dry climates, outdoor lifestyle
3. • General Pathology
– Histologically, pterygia are an accumulation of degenerated subepithelial
tissue which is basophilic with a characteristic slate gray appearance on
H&E staining.
– Vermiform or elastotic degeneration refers to the wavy worm-like
appearance of the fibers.
– Destruction of Bowman layer by fibrovascular ingrowth is typical.
– The overlying epithelium is usually normal, but may be acanthotic,
hyperkeratotic, or even dysplastic and often exhibits areas of goblet cell
hyperplasia.
4. • Pathophysiology
– The large number of theories that exist to explain the pathogenesis of pterygium
growth underscores the uncertainty of the etiology.
– The increased prevalence in hot dry climates and regions nearer to the equator
suggest a role of environmental factors such as UV radiation and dryness.
– Actinic changes seen on histopathology similar to actinic keratoses on the skin also
supports the role of UV radiation.
– It has been suggested that radiation activated fibroblasts may result in excessive
production of material resulting in pterygia.
– Other proposed theories include choline deficiency, inflammation, disregulation of
angiogenesis, immune system abnormalities, tear film abnormalities, as well as the
possible role of a viral stimulus.
– Coronea MT proposed that pterygium occur due to albedo concentration in the
anterior eye (albedo's hypothesis).
– Light entering the temporal limbus at 90 degree is concentrated at medial limbus
and this is responsible for predominance of medial pterygia
5. • Degenerative Versus Proliferative Disorder
– Pterygium has long been considered to be a chronic
degenerative condition based on histologic examination.
– Classically described as an “elastotic degeneration”,
pterygium tissue is characterized by abnormal subepithelial
tissue containing altered collagen fibers demonstrable with
elastic stains.
– There are, however, behavioral and etiologic features of
pterygium that suggest a proliferative growth disorder, not
unlike properties seen in benign tumors.
– As mentioned, pterygium has been linked to dysfunctions in
DNA repair mechanisms, cellular proliferation, migration, and
angiogenesis
6. • Pterygium surgery can be divided into four main
groups, in order of increasing complexity:
• 1. Bare sclera excision
• 2. Excision with conjunctival primary closure or transposition
• 3. Bare sclera excision with antimitotic adjunctive therapies
• 4. Ocular surface transplantation techniques, including
conjunctival or conjunctival-limbal autografts and amniotic
membrane transplantation (AMT).
7. • Mitomycin C
• Mitomycin C (MMC) is an alkylating agent that inhibits
DNA synthesis in all cells. This leads to cell death due to
the inability to repair the genotoxic injury caused by
alkylation. MMC causes a reduction in the number of
cellular division, especially when it comes in contact
with cells in the late G1 and early S phase of the cell
cycle. It therefore has an antiproliferative effect and
reduces fibrovascular tissue formation, which has a
direct effect in reducing recurrence after pterygium
excision
8. • MMC is used in pterygium management in three ways:
• 1. Preoperative subconjunctival injection of MMC directly into the
• pterygium tissue at the limbus, 1 month before bare sclera excision
• of the pterygium (0.1 mL of 0.15 mg/mL MMC). The recurrence
• rate reported was 6% during a 2-year follow-up period.66
• 2. Intraoperative application of surgical sponges soaked in MMC
• solution directly to the scleral bed at the time of pterygium excision.
• Typically with 0.02% MMC for 30 seconds to 5 minutes.51–53,62,67
• Recurrence rates in bare sclera excision reported with this application ranged from 3% to 43%.
• 3. Postoperative use of topical MMC eye drops. Typically, 0.02% MMC
• eye drops are used; however, concentrations vary between 0.005%
• and 0.04%, administered four times daily for 1–2 weeks. Recurrence rates with postoperative MMC drops
are reported between
• 0% and 38%.53,58,59 Application of MMC eye drops are associated
• with complications including ocular surface toxicity, iritis, limbal
• avascularity, scleral melts or calcific plaque, corneal decompensation, scleral or corneal perforations,
secondary glaucoma, and cataract formation.
9. • Several organisms have the ability to penetrate intact corneal epithelium and this group of
• organisms can be remembered using the following mnemonic ‘CHANeLS’.
• C— Corynebacterium
• H— Haemophilus influenza
• A— Acanthamoeba
• Ne— Neisseria gonorrhoea/ meningitidis
• L— Listeria
• S— Shigella
• Microbial keratitis caused by this group of organisms need to be treated aggressively to prevent
• permanent visual loss.
• ASCRS. Special Report: Acanthamoeba Keratitis. July 2007. Available at: http:// www.ascrs.org/
sites/
• default/ files/ resources/ Acanthamoeba%20Keratitis.pdf
• Tjia KF, et al. The interaction between Neisseria gonorrhoeae and the human cornea in organ
culture.
• An electron microscopic study. Graefes Arch Clin Exp Ophthalmol 988;226:34 – 5.
Editor's Notes
UV light, the major environmental risk factor in pterygium, has also been shown to induce mutations in solar keratosis, Bowen disease, and skin carcinomas.31,32 Moreover, wide excision is advocated, as pterygia have a high propensity for recurring aggressively after surgical excision, and adjunctive treatment with antimetabolites reduces its recurrence. Of note, pterygia is associated with a malignant predisposition, although this occurrence is rare, with the incidence varying between different geographical locations.