2. LA MITILICULTURA GALLEGA EN SU ETAPA MADURA (1976-2005):
2.3. Comentario final. El sector mejillonero desde una óptica comparativa
Symptoms
Pain, photophobia, red eye; may be asymptomatic.
Signs
Peripheral corneal thinning (best seen with a narrow slit beam), may have a sterile infiltrate or ulcer.
Differential Diagnosis
Infectious infiltrate or ulcer. Lesions are often treated as infectious until cultures come back negative.
See 4.11, Bacterial Keratitis.
Etiology
z Connective tissue disease (e.g., rheumatoid arthritis, Wegener granulomatosis, relapsing
polychondritis, polyarteritis nodosa, systemic lupus erythematosus, others). Peripheral (unilateral or bilateral) corneal thinning/ulcers may be associated with inflammatory infiltrates. May progress circumferentially to involve the entire peripheral cornea. Perforation may occur. This may be the first manifestation of systemic disease.
z Terrien marginal degeneration: Often asymptomatic; usually bilateral; slowly progressive thinning of the peripheral cornea; typically superior; more often in men. The anterior chamber is quiet, and the eye is typically not injected. A yellow line (lipid) may appear, with a fine pannus over the thinned areas of involvement. The thinning may slowly spread circumferentially. Irregular and against-the-rule astigmatism is often present. The epithelium usually remains intact, but perforation may occur with minor trauma.
z Mooren ulcer: Unilateral or bilateral; idiopathic (autoimmunity may play a key role); diagnosis of exclusion. Painful corneal thinning and ulceration with inflammation; initially starts as a focal area in the peripheral cornea nasally or temporally without limbal sparing with subsequent extension circumferentially or centrally. An epithelial defect, stromal thinning, and a leading undermined edge are present. Limbal blood vessels may grow into the ulcer, and perforation can occur. Mooren-like ulcer
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has been associated with systemic hepatitis C virus infection.
z Pellucid marginal degeneration: Painless, bilateral asymmetric corneal thinning of the inferior peripheral cornea (usually from the 4- to 8-o'clock portions). There is no anterior chamber reaction, conjunctival injection, lipid deposition, or vascularization. The epithelium is intact. Corneal protrusion may be seen above the area of thinning. The thinning may slowly progress.
z Furrow degeneration: Painless corneal thinning just peripheral to an arcus senilis, typically in the elderly. Noninflammatory without vascularization. Perforation is rare. Usually nonprogressive and does not require treatment.
z Delle: Painless oval corneal thinning resulting from corneal drying and stromal dehydration adjacent to an abnormal conjunctival or corneal elevation. The epithelium is usually intact. See 4.24, Dellen.
z Staphylococcal hypersensitivity/marginal keratitis: Peripheral, white corneal infiltrate(s) with limbal clearing that may have an epithelial defect and mild thinning. See 4.19, Staphylococcal
Hypersensitivity.
z Dry-eye syndrome: Peripheral sterile corneal melts may result from severe cases of dry-eye. See 4.3, Dry-Eye Syndrome.
z Exposure/neurotrophic keratopathy: Typically, a sterile oval ulcer develops inferiorly on the cornea without signs of significant inflammation. May be associated with an eyelid abnormality, a fifth or seventh cranial nerve defect, or proptosis. The ulcer may become superinfected. See 4.5, Exposure Keratopathy and 4.6, Neurotrophic Keratopathy.
z Sclerokeratitis: Corneal ulceration is associated with severe radiating ocular pain because of
accompanying scleritis. The sclera develops a blue hue, scleral vessels are engorged, and scleral edema with or without nodules is present. An underlying connective tissue disease, especially Wegener granulomatosis, must be ruled out. See 5.7, Scleritis.
z Vernal keratoconjunctivitis: Superior, shallow, shield-shaped, sterile corneal ulcer, accompanied by giant papillae on the superior tarsal conjunctiva or limbus, with or without degenerated limbal eosinophils (Horner Trantas dots). The conjunctivitis is usually bilateral, often occurs in children, and recurs during the summer months, but it can occur anytime in warm climates. See 5.1, Acute Conjunctivitis.
z Ocular rosacea: Typically affects the inferior cornea in middle-aged patients. Erythema and telangiectasia of the eyelid margins, corneal neovascularization. See 5.9, Ocular Rosacea.
z Others: e.g., cataract surgery, inflammatory bowel disease, previous HSV or HZV infections, and leukemia can rarely cause peripheral corneal thinning/ulceration.
Work-Up
1. History: Contact lens wearer or previous HSV or HZV keratitis? Connective tissue disease or
inflammatory bowel disease? Other systemic symptoms? Seasonal conjunctivitis with itching (vernal)?
Prior ocular surgery?
2. External examination: Old facial scars of HZV? Eyelid-closure problem causing exposure? Blue tinge to the sclera? Rosacea facies?
3. Slit-lamp examination: Look for infiltrate, corneal ulcer, hypopyon, uveitis, scleritis, old herpetic scarring, poor tear lake, SPK, blepharitis. Look for giant papillae on the superior tarsal conjunctiva or limbal papillae. Measure IOP.
4. Schirmer test (see 4.3, Dry-Eye Syndrome).
5. Dilated fundus examination: Look for cotton-wool spots consistent with connective tissue disease or evidence of posterior scleritis (e.g., vitritis, subretinal fluid, chorioretinal folds, exudative retinal
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detachment).
6. Corneal scrapings and cultures when infection is suspected. See Appendix 8, Corneal Culture Procedure.
7. Serum antinuclear antibody, rheumatoid factor, erythrocyte sedimentation rate, and complete blood count with differential to rule out connective tissue disease and leukemia, if suspected. Serum antineutrophilic cytoplasmic antibody levels should be obtained to rule out Wegener granulomatosis.
8. Scleritis work-up, when present (see 5.7, Scleritis).
9. Refer to an internist (or rheumatologist) when connective tissue disease is suspected.
Treatment
See sections on dellen, staphylococcal hypersensitivity, dry-eye syndrome, exposure and neurotrophic keratopathies, scleritis, vernal conjunctivitis, and ocular rosacea.
1. Corneal thinning due to connective tissue disease: Management is usually coordinated with a rheumatologist or internist.
—Antibiotic ointment (e.g., erythromycin ointment) or ocular lubricants while awake (e.g., Refresh Plus or TheraTears q1h or Refresh PM ointment q2h).
—Cycloplegic drops (e.g., scopolamine 0.25% or atropine 1% b.i.d. to t.i.d.) when an anterior chamber reaction or pain is present.
—Consider doxycycline 100 mg p.o., b.i.d. because of its metalloproteinase inhibition properties.
—Systemic steroids (e.g., prednisone, 60 to 100 mg p.o., q.d.; the dosage is adjusted according to the response) and a histamine type 2 receptor (H2) blocker (e.g., ranitidine 150 mg p.o., b.i.d.)
are used for significant and progressive corneal thinning, but not for perforation.
—An immunosuppressive agent (e.g., methotrexate, mycophenolate mofetil, infliximab, azathioprine, cyclophosphamide) is often required, especially for Wegener granulomatosis. This should be done in coordination with the patient's internist or rheumatologist.
—Excision of adjacent inflamed conjunctiva is occasionally helpful when the condition progresses despite treatment.
—Punctal occlusion if dry-eye syndrome is present. Typical cyclosporine 0.05% (e.g., Restasis) b.i.d.
to q.i.d. also may be helpful. Experimental research suggests benefits of oral omega-3 fatty acids for severe dry-eye syndrome.
—Consider cyanoacrylate tissue adhesive or corneal transplantation surgery for an impending or actual corneal perforation. A conjunctival flap or amniotic membrane graft can also be used for an impending corneal perforation.
—Patients with significant corneal thinning should wear their glasses [or protective glasses (e.g., polycarbonate lens)] during the day and an eye shield at night.
2. Terrien marginal degeneration: Correct astigmatism with glasses or contact lenses if possible.
Protective eyewear should be worn if significant thinning is present. Lamellar grafts can be used if thinning is extreme.
3. Mooren ulcer: Underlying systemic diseases must be ruled out before this diagnosis can be made.
Topical corticosteroids, topical cyclosporine 0.05% to 2%, limbal conjunctival excision, corneal gluing, and lamellar keratoplasty may be beneficial. Systemic immunosuppressants (e.g. oral cortico-steroids, methotrexate, cyclophosphamide, and cyclosporine) are indicated and may be lifesaving. See
treatment for corneal thinning secondary to connective tissue disease above.
4. Pellucid marginal degeneration: See 4.25, Keratoconus.
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5. Furrow degeneration: No treatment is required.
Note
Topical steroids are usually not used in the presence of significant corneal thinning because of the risk of perforation. Gradually taper topical steroids if the patient is already taking them. Corneal thinning due to relapsing polychondritis, however, seems to improve with topical steroids (e.g., prednisolone acetate 1% q1–2h).
Note
If systemic steroid therapy is to be instituted, obtain a steroid work-up (see
“Prednisone” in Pharmacopoeia) as indicated, and involve the patient's primary medical doctor.
Follow-Up
Patients with severe disease are examined daily in the hospital or as outpatients if compliant; those with milder conditions are checked less frequently. Watch carefully for signs of superinfection (e.g., increased pain, stromal infiltration, anterior chamber cells and flare, conjunctival injection), increased IOP, and progressive corneal thinning. Treatment is maintained until the epithelial defect over the ulcer heals and is then gradually tapered. As long as an epithelial defect is pres-ent, there is risk of progressive thinning and perforation.
4.24 Dellen Dellen Symptoms
Usually asymptomatic; irritation, foreign body sensation.
Signs
Critical. Corneal thinning, usually at the limbus, often in the shape of an ellipse,
accompanied by an adjacent focal conjunctival or corneal elevation.
Other. Fluorescein pooling in the area, but minimal staining. No infiltrate, no anterior chamber reaction, minimal to moderate hyperemia.
Differential Diagnosis
See 4.23, Peripheral Corneal Thinning/Ulceration.
Etiology
Poor spread of the tear film over a focal area of cornea (with resultant stromal dehydration) due to an adjacent surface elevation (e.g., chemosis, conjunctival hemorrhage, filtering bleb, pterygium, tumor, and poststrabismus surgery).
Work-Up
1. History: Previous eye surgery?
2. Slit-lamp examination with fluorescein staining: Look for an adjacent area of elevation.
Treatment
1. Lubricating or antibiotic ointment (e.g., Refresh PM, erythromycin ointment) q.i.d. and q.h.s. Maintain the ointment at least q.h.s. until the adjacent elevation is eliminated.
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2. If the cause cannot be removed (e.g., filtering bleb), lubricating ointment should be applied nightly, and viscous artificial tear drops (e.g., Refresh Liquigel, Celluvisc, GenTeal Gel or TheraTears Gel) used four to eight times per day. If drops are needed more than four times per day, a preservative-free drop should be used.
Follow-Up
Unless there is severe thinning, reexamination can be performed in 1 to 7 days, at which time the cornea can be expected to be of normal thickness. If it is not, full-time patching and lubrication should again be instituted.
4.25 Keratoconus Keratoconus Symptoms
Progressive decreased vision, usually beginning in adolescence and continuing into middle age. Acute corneal hydrops can cause a sudden decrease in vision, pain, red eye, photophobia, and profuse tearing.
Signs
(See Figure 4.25.1.)
Critical. Slowly progressive irregular astigmatism resulting from paracentral thinning and bulging of the cornea (maximal thinning near the apex of the protrusion), vertical tension lines in the posterior cornea (Vogt striae), an irregular corneal retinoscopic reflex (scissor reflex), and egg-shaped mires on
keratometry. Inferior steepening is seen on corneal topographic evaluation. Usually bilateral but often asymmetric.
Other. Fleischer ring (epithelial iron deposits at the base of the cone), bulging of the lower eyelid when looking downward (Munson sign),
superficial corneal scarring. Corneal hydrops (sudden development of corneal edema) results from a rupture in Descemet membrane (see Figure 4.25.2).
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Figure 4.25.1. Keratoconus.
Associations
Keratoconus is associated with Down syndrome, atopic disease, Turner syndrome, Leber congenital amaurosis, mitral valve prolapse, retinitis pigmentosa, and Marfan syndrome. It is related to chronic eye rubbing. Family history of keratoconus is also a risk factor.
Differential Diagnosis
z Pellucid marginal degeneration: Corneal thinning in the inferior periphery. The cornea protrudes superior to the band of thinning.
z Keratoglobus: Rare, congenital, nonprogressive. Uniform circularly thinned cornea with maximal thinning in the mid-periphery of the cornea. The cornea protrudes central to the area of maximal thinning.
Note
Treatment for pellucid marginal degeneration is the same as for keratoconus, except corneal transplantation is technically more difficult due to peripheral thinning and has a higher failure rate because larger grafts are necessary.
z Post–refractive surgery ectasia: After lamellar refractive surgery such as laser in situ keratomileusis (LASIK), and rarely surface ablation, a condition very similar to keratoconus can develop. It is treated in the same manner as keratoconus.
Work-Up
1. History: Duration and rate of decreased vision? Frequent change in eyeglass prescriptions? History of eye rubbing? Medical problems? Allergies? Family history? Previous refractive surgery?
2. Slit-lamp examination with close attention to location and characteristics of corneal thinning, Vogt striae, and a Fleischer ring (may be best appreciated with cobalt blue light).
3. Retinoscopy and refraction. Look for irregular astigmatism and a waterdrop or scissors red reflex.
4. Corneal topography (can show central and inferior steepening) and keratometry (irregular mires and steepening).
Treatment
1. Patients are instructed not to rub their eyes.
2. Correct refractive errors with glasses or soft contact lenses (for mild cases) or RGP contact lenses Figure 4.25.2. Acute corneal hydrops.
(successful in most cases). Occasionally, hybrid contact lenses are required.
3. Corneal transplantation surgery is usually indicated when contact lenses cannot be tolerated or no longer produce satisfactory vision.
4. Intracorneal ring segments have been successful in getting some patients back into contact lenses, especially in mild to moderate keratoconus.
5. Acute corneal hydrops:
—Cycloplegic agent (e.g., cyclopentolate 1%), bacitracin ointment q.i.d., and consider brimonidine (e.g., alphagan).
—Start sodium chloride 5% ointment (e.g., Muro 128) b.i.d. until resolved (usually several weeks to months).
—Glasses or a shield should be worn by patients at risk for trauma or by those who rub their eyes.
Note
Acute hydrops is not an indication for emergency corneal transplantation, except in the extremely rare case of corneal perforation (which is first treated medically and
sometimes with tissue adhesives).
Follow-Up
Every 3 to 12 months, depending on the progression of symptoms. After an episode of hydrops, examine the patient every 1 to 4 weeks until resolved (which can take several months).