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Ophthalmology > CORNEA
Dystrophy, Macular
Article Last Updated: Mar 16, 2006
AUTHOR AND EDITOR INFORMATION
Section 1 of 10  
Author: William Trattler, MD, Miami Center for Excellence in Eye Care; Consulting Staff, Department of Ophthalmology, Miami Baptist Hospital
William Trattler is a member of the following medical societies: American Academy of Ophthalmology
Coauthor(s):
William Lloyd Clark, MD, Consulting Staff, Palmetto Retina;
Natalie Afshari, MD, Assistant Professor, Cornea and Refractive Surgery, Department of Ophthalmology, Duke University Eye Center, Duke University Medical Center
Editors: Fernando H Murillo-Lopez, MD, Senior Surgeon, Unidad Privada de Oftalmologia CEMES; Simon K Law, MD, PharmD, Assistant Professor of Ophthalmology, Jules Stein Eye Institute; Chief of Section of Ophthalmology Surgical Services, Department of Veterans Affairs Healthcare Center, West Los Angeles; Christopher J Rapuano, MD, Professor, Department of Ophthalmology, Jefferson Medical College; Co-Chairman of the Cornea Service, Co-Chairman of Refractive Surgery Department, Wills Eye Hospital; Lance L Brown, OD, MD, Ophthalmologist, Affiliated With Freeman Hospital and St John's Hospital, Regional Eye Center, Joplin, Missouri; Hampton Roy Sr, MD, Associate Clinical Professor, Department of Ophthalmology, University of Arkansas for Medical Sciences
Author and Editor Disclosure
Synonyms and related keywords:
corneal dystrophy, corneal stroma, anterior corneal dystrophy, stromal corneal dystrophy, posterior corneal dystrophy, corneal dystrophies
Background
Macular dystrophy is an autosomal recessive condition, which is the least common but the most severe of the 3 major stromal corneal dystrophies. It is characterized by multiple, gray-white opacities that are present in the corneal stroma and that extend out into the peripheral cornea.
Pathophysiology
The cornea is the clear outer coat of the front of the eye. A dystrophy of the cornea is defined as a bilateral noninflammatory clouding of the cornea. Corneal dystrophies can be placed into 3 categories based on their location within the cornea. Anterior corneal dystrophies affect the corneal epithelium and may involve the Bowman membrane. Stromal corneal dystrophies (which include macular dystrophy) affect the central layer of the cornea, the stroma. Posterior corneal dystrophies involve the Descemet membrane and the endothelium.
Most corneal dystrophies have an onset prior to 20 years; exceptions include map-dot-fingerprint dystrophy and Fuchs corneal dystrophy. Most corneal dystrophies are dominantly inherited; exceptions are macular dystrophy, type 3 lattice dystrophy, and the autosomal-recessive form of congenital hereditary endothelial dystrophy.
Subgroups of macular dystrophy can be identified by immunohistochemical methods. Keratan sulfate was not detected in the serum of patients with histopathologically confirmed macular corneal dystrophy. Since keratan sulfate in the serum appears to be derived predominantly from the normal turnover of cartilage, these studies strongly suggest that the defect in keratan sulfate synthesis in macular corneal dystrophy is not restricted to corneal cells and that this condition is one manifestation of a systemic disorder of keratan sulfate.
Frequency
United States
Uncommon
Mortality/Morbidity
- Corneal changes become visible in the first decade of life; a significant reduction in vision usually occurs by age 20-40 years.
- Eye pain from recurrent corneal erosions can occur but is much less common than in patients with lattice or granular dystrophies.
Sex
No sexual predilection has been reported.
Age
Corneal changes become visible in the first decade of life; vision may be significantly reduced by age 20-40 years.
History
- In many patients, macular dystrophy is first visible in the cornea during the first decade of life.
- Generally, over time, vision decreases, and patients develop photosensitivity. They may also experience eye pain from recurrent corneal erosions.
Physical
- Macular dystrophy is characterized by multiple, gray-white opacities that are present in the corneal stroma and extend into the peripheral cornea. (In granular dystrophy, the deposits are located centrally.)
- These stromal opacities are distributed throughout the cornea without clear spaces. (Granular dystrophy has clear zones.)
- Macular corneal dystrophy involves the entire thickness of the cornea and is more superficial centrally and deeper peripherally. The central cornea in this condition may be thinned. Significant cornea guttata may be present.
Causes
- Macular dystrophy is autosomal recessive.
- The gene responsible for macular dystrophy is located on chromosome 6.
- The metabolic defect for this condition appears to be an error in the synthesis of keratan sulfate.
- Two types of macular dystrophy exist based on the absence or presence of keratan sulfate within the corneal stroma. Type I macular dystrophy has an absence of keratan sulfate, whereas in type II, keratan sulfate is present.
Dystrophy, Crystalline
Dystrophy, Granular
Dystrophy, Lattice
Other Problems to be Considered
Corneal opacities
Procedures
- A corneal biopsy sample (which would never be clinically indicated) would reveal deposits of glycosaminoglycans, which stain with Alcian blue and colloidal iron.
- Light microscopy reveals glycosaminoglycan deposits within stromal keratocytes.
Histologic Findings
Deposits in macular dystrophy are composed of glycosaminoglycans, which stain with Alcian blue and colloidal iron. Light microscopy demonstrates glycosaminoglycan deposits within stromal keratocytes. Two types of macular dystrophy exist based on the absence or presence of keratan sulfate within the corneal stroma. Type I macular dystrophy has an absence of keratan sulfate, whereas in type II, keratan sulfate is present.
Medical Care
- When recurrent corneal erosions occur with this condition, they are treated like any other form of recurrent corneal erosion.
- Under the care of an ophthalmologist, a bandage contact lens along with antibiotics can be prescribed. Alternatively, patching with an antibiotic ointment or frequent application of an antibiotic ointment can be used.
- Once the acute episode of recurrent corneal erosion resolves, preventive treatment may include sodium chloride 5% drops (eg, Muro 128) or artificial tear lubricating drops during the day and sodium chloride 5% ointment (eg, Muro 128) or lubricating ointment at bedtime.
- If recurrent corneal erosions occur despite medical therapy, then excimer laser phototherapeutic keratectomy (PTK) may be considered.
- Sunglasses are often helpful for severe glare symptoms.
Surgical Care
- Excessive corneal erosions or a mild visual decrease can be treated with excimer laser PTK, which works best when the opacities are superficial. The excimer laser removes superficial corneal opacities, smooths the corneal surface, and allows the epithelium to re-adhere more tightly.
- If visual acuity drops and the opacities are deep, lamellar or full-thickness corneal transplantation can be performed. Although the success rate for corneal transplantation is high, macular dystrophy deposits can recur with time.
Medical therapy for recurrent corneal erosions includes hypertonic saline, which is thought to increase adherence of the epithelium to the underlying stroma. Lubrication may also help prevent corneal erosions.
Drug Category: Hypertonic saline
Dehydrates the epithelium, allowing it to better adhere to the underlying stroma.
| Drug Name | Sodium chloride 5% (Muro 128, Adsorbonac, Afrin) |
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| Description | Used for temporary relief of corneal edema. |
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| Adult Dose | Solution: 1-2 gtt to affected eye(s) tid/qid
Ointment: Apply 0.25-0.5 inch to lower cul-de-sac hs |
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| Pediatric Dose | Administer as in adults |
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| Contraindications | Documented hypersensitivity |
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| Interactions | None reported |
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| Pregnancy | A - Safe in pregnancy
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| Precautions | May cause temporary burning and irritation upon use; if pain, change in vision, continued redness or irritation of the eye(s) occurs, reevaluate therapy; if initial condition/problem worsens or persists, reevaluate therapy; do not use product if it changes color or becomes cloudy |
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Drug Category: Lubricating agent
Moistens the ocular surface and decreases the frequency of recurrent erosions.
| Drug Name | Artificial tears (GenTeal, Refresh tears, TheraTears, Bion tears, Refresh Plus) |
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| Description | Contains equivalent of 0.9% NaCl and used to maintain ocular tonicity. Acts to stabilize and thicken precorneal tear film and prolong tear film breakup time, which occurs with dry eye states. |
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| Adult Dose | Solution: 1 gtt 4-8 times/d to affected eye(s) or as directed
Ointment: Apply 0.25-0.5 inch to lower cul-de-sac hs |
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| Pediatric Dose | Administer as in adults |
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| Contraindications | Documented hypersensitivity |
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| Interactions | None reported |
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| Pregnancy | A - Safe in pregnancy
|
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| Precautions | Hyperemia, photophobia, stickiness of eyelashes, and ocular discomfort or irritation may occur |
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Further Outpatient Care
- Patients with epithelial defects from recurrent corneal erosions need to be observed every few days to ensure that the abrasion is healing.
In/Out Patient Meds
- Patients with epithelial defects from recurrent corneal erosions are treated with topical antibiotics to prevent corneal infection.
Complications
- Complications of macular corneal dystrophy include photophobia; loss of vision; and, less commonly, recurrent corneal erosions.
Prognosis
- Of all stromal corneal dystrophies, macular corneal dystrophy results in the earliest visual loss. This visual loss is due to the lack of clear spaces between the denser gray-white macular opacities.
- Symptomatic patients are eligible for either excimer laser PTK (when the bulk of the opacity is superficial) or, more commonly, corneal transplantation.
| Media file 1:
Macular dystrophy. Image courtesy of James J. Reidy, MD, FACS, Associate Professor of Ophthalmology, State University of New York, School of Medicine & Biomedical Sciences, Buffalo, New York. |
 |  View Full Size Image | |
Media type: Photo
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- Al-Swailem SA, Al-Rajhi AA, Wagoner MD. Penetrating keratoplasty for macular corneal dystrophy. Ophthalmology. Feb 2005;112(2):220-4. [Medline].
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- Edward DP, Yue BY, Sugar J, et al. Heterogeneity in macular corneal dystrophy. Arch Ophthalmol. Nov 1988;106(11):1579-83. [Medline].
- Hafner A, Langenbucher A, Seitz B. Long-term results of phototherapeutic keratectomy with 193-nm excimer laser for macular corneal dystrophy. Am J Ophthalmol. Sep 2005;140(3):392-6. [Medline].
- Klintworth GK, Meyer R, Dennis R, et al. Macular corneal dystrophy. Lack of keratan sulfate in serum and cornea. Ophthalmic Paediatr Genet. Dec 1986;7(3):139-43. [Medline].
- Krachmer J. Cornea. Vol 2. 1996.
- Wirtitsch MG, Ergun E, Hermann B. Ultrahigh resolution optical coherence tomography in macular dystrophy. Am J Ophthalmol. Dec 2005;140(6):976-983. [Medline].
Dystrophy, Macular excerpt Article Last Updated: Mar 16, 2006
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