Corneal Dystrophy

BASICS


DESCRIPTION


• Two major categories of lattice corneal dystrophy are described by the International Committee for Classification of Corneal Dystrophies (IC3D) (1).


• A dystrophy is a process that is noninflammatory and bilateral.


• Lattice corneal dystrophy type I (LCD I) is typically an autosomal dominant corneal dystrophy that leads to frequent recurrent corneal erosions and can progress to severe visual impairment.


• The onset of symptoms is in the first decade of life, with visual impairment often by the fourth decade.


• With this dystrophy protein (amyloid) deposits in the corneal stroma creating refractile branching lines the resemble lattice work. In LCD I, the branching lines do not reach the corneal limbus.


• Synonyms of LCD I include classic LCD and Biber-Haab-Dimmer dystrophy.


• Lattice corneal dystrophy type II (LCD II) has similar corneal changes but the lattice lines start peripherally and move centrally.


• Onset of symptoms is typically in third to fourth decade of life


• Often LCD II is associated with systemic amyloidosis and can be associated with central and peripheral neuropathy, carpal tunnel syndrome, autonomic disturbances, and cardiac arrhythmia


• Synonyms of LCD II include Meretoja syndrome, Amyloidosis V, Familial amyloidotic polyneuropathy IV, Familial amyloidosis, Finnish.


• Autosomal recessive variants of LCD are known, but are very rare. Most patients with have Japanese ancestry.


EPIDEMIOLOGY


LCD is the most common of the stromal corneal dystrophies but is still relatively rare.


RISK FACTORS


• Family history of LCD. Spontaneous mutation in the TGFβI gene can lead to the dystrophy in the absence of a family history.


• Family history of systemic amyloidosis is a risk factor for LCD II. Spontaneous mutation in the Gelsolin (9q34) is responsible for sporadic cases.


Genetics


• LCD I is linked to the transforming growth factor-β-induced (TGFβI) gene on chromosome 5q31 as are many other corneal stromal dystrophies. This gene was once called the BIGH3 gene.


• LCD II is linked to the gelsolin gene 9q34.


GENERAL PREVENTION


Genetic screening


PATHOPHYSIOLOGY


• Accumulation of amyloid protein in the corneal stroma leads to branching refractile lines. When these deposits of amyloid are close to the surface of the corneal erosions of corneal epithelium can occur. Corneal epithelial erosions lead to pain, light sensitivity, and in some cases reduced vision.


• Multiple recurrences of epithelial erosions will lead to scar formation on the corneal leading to a decline in best corrected vision.


ETIOLOGY


Genetic mutation in either the TGFβI or Gelsolin gene. Multiple mutations have been documented in the FAS1 domain of the TGFβI gene, all leading to the phenotype of LCD.


COMMONLY ASSOCIATED CONDITIONS


• LCD I has no commonly associated conditions.


• LCD II is part of a systemic amyloidosis and can be associated with any or all of the following:


– Cranial neuropathy leading to facial drooping and corneal anesthesia


– Peripheral neuropathy


– Autonomic dysfunctions such as postural orthostatic tachycardia syndrome, vasovagal syncope, and neurally mediated hypotension


DIAGNOSIS


HISTORY


• Younger patients will complain of spontaneous foreign body sensation.


• Tearing and photophobia will occur in one or both eyes.


• Erosions in the visual axis will reduce vision.


• Older patients will additionally experience a reduction in best corrected vision.


PHYSICAL EXAM


• In early disease the slit lamp exam of the cornea may show subepithelial faint opacities usually close to the apex of the cornea.


• With time the opacities form branching lattice lines that migrate peripherally and deeper into the cornea.


• Repeated corneal epithelial erosions will eventually cause scar formation in the anterior cornea.


• Corneal sensation is often reduced which made reduce healing time.


• In LCD II, the lattice lines may start at the periphery and move centrally over time, and they are more likely to include the periphery.


• Recurrent erosions are less likely in LCD II, but neurotrophic epithelial defects are often a problem.


DIAGNOSTIC TESTS & INTERPRETATION


Diagnostic Procedures/Other


Diagnosis is based on physical exam.


Pathological Findings


• Pathology will show deposits in the cornea of amyloid protein.


• Amyloid protein will stain with congo red stain.


• Amyloid protein will also show apple green birefringence with polarized light.


DIFFERENTIAL DIAGNOSIS


• Recurrent corneal erosion


• Amyloid corneal degeneration


• Granular dystrophy


• Macular dystrophy


TREATMENT


MEDICATION


First Line


• Treatment of the recurrent erosions with:


– Topical antibiotics, usually a fluoroquinolone


– Hypertonic saline drops/ointment


– Frequent lubricating drops


– Cyclopedias to reduce photophobia


Second Line


• Epithelial debridement can accelerate the healing of an epithelial erosion.


• Bandage contact lenses are helpful in reducing the pain of an erosion and may speed healing. Antibiotic prophylaxis is a must in these cases with close follow-up.


ADDITIONAL TREATMENT


General Measures


• Routine health care is a must.


• Communication with primary care provider is essential especially in cases of LCD II.


• Reassurance of the patient that while no cure is available, excellent treatments are available.


Issues for Referral


• Referral to a corneal/external disease specialist may be indicated once erosions become problematic or best-corrected vision becomes reduced.


• Frequency of follow-up will depend on severity of symptoms and corneal changes.


SURGERY/OTHER PROCEDURES


• Reduced best-corrected vision from LCD is usually due to progressive scar formation and irregularity in the cornea.


• In early stages, erosions and mild scars can be treated with superficial keratectomy and diamond burr debridement.


• More significant superficial scars can be treated with phototherapeutic keratectomy (PTK) (2).


• Deeper scars require treatment by full or partial thickness corneal transplantation.


• Watch for slower epithelial healing in patients with LCD (3).


• LCD will eventually return in the transplanted cornea.


IN-PATIENT CONSIDERATIONS


Initial Stabilization

Inpatient admission for LCD is very unusual unless it is for systemic complications of familial amyloidosis.


ONGOING CARE


FOLLOW-UP RECOMMENDATIONS


• Regular follow-up with a comprehensive ophthalmologist or cornea specialist is recommended.


• Frequency of follow-up will depend on severity of corneal changes.


• If patients have had a corneal transplant, regular follow-up is needed to ensure transplant success and watch for recurrence of dystrophy.


Patient Monitoring


Any patient who is on topical steroids long time after corneal transplant must be monitored for steroid-related complications such as cataract progression and elevation in eye pressure.


PATIENT EDUCATION


• Patient education is essential.


www.cornealdystrophyfoundation.org


PROGNOSIS


• Patients with LCD I are very likely to need corneal surgery by the fourth decade. With proper follow-up and management the prognosis for good vision is excellent.


• Longevity of life is normal in these patients.


• Patients with LCD II are less likely to need corneal surgery, but much more likely to suffer from health problems related to systemic amyloidosis.


COMPLICATIONS


• Infectious keratitis can be seen with corneal epithelial erosions and from chronic steroid use.


• Recurrence of lattice dystrophy in the transplanted corneal is common.


• Steroid-induced glaucoma is observed in transplant patients.


• Corneal transplant rejection.



REFERENCES


1. Weiss JS, et al. The IC3D classification of the corneal dystrophies. Cornea 2008;27:S1–S42.


2. Ayres BD, Rapuaon CJ. Excimer laser phototherapeutic keratectomy. Ocular Surface 2006;4(4):196–206.


3. Foerster CG, Langenbucher A, Cursliefen C, et al. Delayed epithelial healing after keratoplasty for lattice corneal dystrophy. Cornea 2007;26:1182–1183.

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Nov 9, 2016 | Posted by in OPHTHALMOLOGY | Comments Off on Corneal Dystrophy
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