EBM dystrophy is due to an abnormality of production of epithelial basement membrane that extends into the epithelium, leading to multiple basement membranes in the corneal epithelium. Trapped epithelial cells can form “Cogan’s microcysts.”
Typically degenerative, occasionally autosomal dominant (transforming growth factor beta–induced [TGFBI] gene of chromosome 5q31)
Symptoms
Most commonly asymptomatic
Recurrent erosion syndrome: may have unilateral or bilateral recurrent episodes of pain in the middle of the night or upon opening the eyes after sleep. Can occur after trauma with a sharp object such as a fingernail, tree branch, or paper edge
May note painless distortion of vision when the central cornea is involved
Signs
Slit-lamp examination shows maplike lines, dots (microcysts), and/or fingerprint-like epithelial lesions, which may occur singly or in various combinations (Fig. 5-1). These findings are best seen with retroillumination and with a broad slit beam from the side. “Negative staining” from slightly elevated areas of epithelium may be seen with fluorescein dye.
Eyes with recurrent erosions may have minimal clinical findings, localized areas of loose epithelium, or a frank epithelial defect.
Differential Diagnosis
Other anterior corneal dystrophies, such as Meesmann’s dystrophy and Reis-Bücklers dystrophy
Treatment
If vision is decreased due to central involvement, the irregular epithelium can be debrided.
Painful erosions can be treated with lubrication, hypertonic drops and ointment (sodium chloride 5%), pressure patching, topical corticosteroids and oral doxycycline, epithelial debridement, bandage soft contact lens, anterior stromal micropuncture, diamond burr polishing of Bowman’s membrane, or excimer laser phototherapeutic keratectomy (PTK).
Prognosis
Very good with appropriate treatment, although some patients have recalcitrant recurrent erosions
Figure 5-1. Epithelial basement membrane dystrophy.A. Reduplicated epithelial basement membrane causing maplike changes are readily visible centrally. Epithelial basement membrane dystrophy. B. Large maplike opacities are present throughout the central cornea, causing complaints of monocular “diplopia,” better described as “shadow vision.” C. Maplike changes in this eye are almost confluent centrally, resulting in significant visual distortion. Epithelial basement membrane dystrophy. D. The maplike changes here are often referred to as a “mare’s tail” pattern. E. Fluorescein stain and the cobalt blue light view of the cornea shown in D. Significant “negative staining” is evident because of areas of elevated epithelium. These elevated areas can cause foreign-body sensation and/or decreased vision. Epithelial basement membrane dystrophy.F. Dot changes of EBM dystrophy. These creamy white Cogan microcysts are tiny pockets of surface epithelial cells trapped beneath an abnormal epithelial basement membrane. G. A large area of epithelial microcysts is seen superiorly. Epithelial basement membrane dystrophy. H. Retroillumination view of the same eye highlights the epithelial microcysts. I. Fingerprint-like changes of EBM dystrophy in retroillumination. These parallel lines and bleblike changes are a result of irregularities in the epithelial basement membrane. They are causing irregular astigmatism and decreased vision.
MEESMANN’S CORNEAL DYSTROPHY (JUVENILE HEREDITARY EPITHELIAL DYSTROPHY)
Meesmann’s dystrophy is a rare bilateral epithelial disorder that can cause ocular irritation and photophobia.
Etiology and Pathology
Meesmann’s dystrophy is an autosomal dominant (keratin K3 and K12 genes of chromosomes 12q13 and 17q12, respectively) condition in which hundreds of tiny vesicles containing periodic acid-Schiff (PAS)–positive “peculiar substance” are found in the epithelium.
Symptoms
Patients are usually asymptomatic but may note irritation, glare, and photophobia. Mild pain may develop in adulthood as a result of recurring corneal erosions.
Signs
Retroillumination demonstrates myriad tiny, translucent, epithelial cysts that extend to the limbus and are most numerous in the interpalpebral region. The lesions appear gray or clear under direct illumination (Fig. 5-2).
Treatment
Most patients require no treatment. Consider lubrication and sunglasses for mild symptoms. Rarely, a bandage soft contact lens can be used or a superficial keratectomy can be performed for severe symptoms, but the dystrophy will recur.
Prognosis
Good, although rare patients will have chronic symptoms
Figure 5-2.Meesmann’s dystrophy. A. Multiple tiny, translucent, epithelial cysts are apparent in retroillumination. They tend to be more prominent in the interpalpebral zone. B. On direct illumination, the microcysts are gray in color but are difficult to see. On illumination of the iris, at the 3 o’clock edge of the pupil, myriad microcysts are visible.
REIS-BüCKLERS DYSTROPHY
Reis-Bücklers dystrophy is an uncommon, bilateral, symmetric dystrophy of Bowman’s membrane that causes pain and decreased vision early in life.
Etiology
Reis-Bücklers dystrophy is an autosomal dominant (TGFBI gene of chromosome 5q31) disorder that causes damage and scarring to Bowman’s membrane and the anterior stroma.
Symptoms
Severe recurrent corneal erosions from a young age, even soon after birth
Progression of the condition leads to reduced vision that occurs in the second to third decades of life, although in severe cases it can occur in the first decade.
Signs
Honeycomb appearance due to reticular, ring-shaped, subepithelial opacities that are most dense centrally but may involve the entire cornea. With time, they can progress deeper into the stroma (Fig. 5-3A–D).
Differential Diagnosis
Other anterior or stromal dystrophies (e.g., epithelial basement membrane dystrophy, granular dystrophy, macular dystrophy)
Treatment
Mild cases: lubrication
More severe cases: bandage soft contact lenses, superficial keratectomy, excimer laser PTK, mid-stromal or deep anterior lamellar keratoplasty, or penetrating keratoplasty may be necessary.
Prognosis
Excimer laser PTK can be quite successful in improving vision and decreasing painful episodes in many cases. Keratoplasty may be required in advanced cases. Recurrence in the donor graft is common after corneal transplantation and also after PTK (Fig. 5-3E and F). PTK can often be repeated or performed for recurrence after keratoplasty.
Figure 5-3. Reis-Bücklers dystrophy. A. A slight reticular pattern can be seen mainly in the central cornea in this eye with relatively mild Reis-Bücklers dystrophy. B. This eye has moderate changes of Reis-Bücklers dystrophy. It primarily involves the central cornea, but the opacity approaches the limbus inferiorly. Reis-Bücklers dystrophy. C. This eye with advanced Reis-Bücklers dystrophy has diffuse, reticular, limbus-to-limbus subepithelial and anterior stromal opacity. There are few if any clear spaces. D. This eye also has advanced Reis-Bücklers dystrophy. Fortunately, the vision improved significantly after excimer laser PTK. Reis-Bücklers dystrophy.E. Recurrent Reis-Bücklers a few years after a penetrating keratoplasty. Unfortunately, Reis-Bücklers recurs relatively rapidly after corneal transplantation. F. This eye also has recurrent Reis-Bücklers dystrophy several years after penetrating keratoplasty. Note the honeycomb opacity centrally and involvement of the entire corneal periphery.
GELATINOUS DROP–LIKE CORNEAL DYSTROPHY
Gelatinous drop–like corneal dystrophy is a rare condition that causes significant symptoms early in life.
Etiology and Pathology
Gelatinous drop–like corneal dystrophy is an autosomal recessive condition (tumor-associated calcium signal transducer 2 gene of chromosome 1p32)
Histopathology: subepithelial and stromal amyloid deposits
Symptoms
Severe decreased vision, pain, redness, photophobia, and tearing beginning in the first two decades of life.
Signs
There are a variety of presentations, including relatively flat subepithelial opacities similar to band keratopathy, small or large groups of elevated nodules (“mulberry” pattern) (Fig. 5-4A), and larger nodular lesions (“kumquat” pattern).
Superficial and deep neovascularization may develop.
Superficial and deep stromal opacification may also develop.
Differential Diagnosis
Other anterior or stromal dystrophies (e.g., macular dystrophy, Reis-Bücklers dystrophy, granular dystrophy)
Treatment
Mild cases: lubrication
More severe cases: bandage soft contact lenses, superficial keratectomy, excimer laser PTK, mid-stromal or deep anterior lamellar keratoplasty, or penetrating keratoplasty may be necessary.
Prognosis
Poor, because the condition typically recurs within a few years (Fig. 5-4B). Rarely, a keratoprosthesis may be required if there is good optic nerve and macular function.
Figure 5-4. Gelatinous drop–like dystrophy. A. Confluent severe central “mulberry-like” elevated lesions are seen in this man with gelatinous drop–like dystrophy. Obtaining good photographs was difficult due to intense photophobia. B. Approximately 2 years after penetrating keratoplasty, there was significant symptomatic recurrence of the nodules. This patient is the sister of the patient seen in A.
STROMAL CORNEAL DYSTROPHIES
GRANULAR DYSTROPHY
Granular dystrophy is an uncommon disorder that can cause decreased vision and recurrent painful erosions in young adults.
Etiology and Pathology
Granular dystrophy is an autosomal dominant (TGFBI gene of chromosome 5q31) disorder that becomes manifest during the first or second decade of life.
Histopathology: Hyaline deposits stain bright red with Masson trichrome.
Symptoms
Painful recurrent erosions are uncommon, but they may occur before vision is significantly affected.
Decreased vision occurs in young adulthood and middle age, when the corneal opacities become confluent.
Signs
Small, discrete, white granules (“crushed breadcrumbs”) within the central anterior stroma, separated by clear intervening spaces. With time, the lesions extend deeper within the stroma and become larger and more numerous. With more time, superficial lesions become confluent over the pupillary axis, severely affecting vision. The periphery is spared (Fig. 5-5).
Differential Diagnosis
Other anterior or stromal dystrophies (e.g., Reis-Bücklers dystrophy, macular dystrophy)
Treatment
Mild cases: lubrication
More severe cases: bandage soft contact lenses, superficial keratectomy, excimer laser PTK, mid-stromal or deep anterior lamellar keratoplasty, or penetrating keratoplasty may be necessary.
Prognosis
Excimer laser PTK can be quite successful in improving vision and decreasing painful episodes in many cases. Lamellar or penetrating keratoplasty may be required in advanced cases. Recurrence in the donor graft is common after corneal transplantation and also after PTK, although it takes longer than after surgery for Reis-Bücklers dystrophy. PTK can often be repeated or performed for recurrence after keratoplasty.
Figure 5-5. Granular dystrophy. A. This eye with mild granular dystrophy has minimal opacity and still retains excellent vision. There are numerous discrete white, “crushed breadcrumb” opacities centrally with clear intervening spaces. B. The same eye seen in retroillumination off the retina; the granules are highlighted. Granular dystrophy. C. This eye with granular dystrophy has relatively confluent opacities although the granules are small and not very dense. D. This slit-beam view demonstrates some of the granular opacities to be rather superficial. Granular dystrophy. E. This eye has a combination of the flat “crushed breadcrumb” opacities and the more three-dimensional dense white stellate opacities. The intervening spaces are still relatively clear. F. The larger, denser, deeper granules are hidden by almost confluent, very anterior stromal opacities. The Vision is poor. Fortunately, the confluent anterior opacities are often treatable with excimer laser PTK.
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