| Macular corneal dystrophy | |
|---|---|
 | |
| Colloidal iron staining shows deposition of glycosaminoglycans in the cornea | |
| Specialty | Ophthalmology  |
Macular corneal dystrophy, also known as Fehr corneal dystrophy, is a rare pathological condition affecting the stroma of cornea first described by Arthur Groenouw in 1890.[1] Signs are usually noticed in the first decade of life and progress afterwards, with opacities developing in the cornea and attacks of pain. This gradual opacification leads to visual impairment often requiring keratoplasty in the later decades of life.[2]
Epidemiology[edit]
While Macular Corneal Dystrophy is found throughout the world, countries with the highest prevalence include Iceland, Saudi Arabia, India, and the United States.[3][4][5] In Iceland, MCD accounts for almost one-third of all corneal grafts performed.[4] Estimates from Claims Data in the United States place the prevalence of MCD at 9.7 per million, which represents less than 1% of corneal dystrophies.[6]
Pathophysiology[edit]
Macular Corneal Dystrophy is an autosomal recessive genetic disorder caused by mutations in the carbohydrate sulfotransferase gene (CHST6), resulting in abnormal proteoglycan synthesis. The accumulation of abnormal glycosaminogycans in the corneal epithelium and stroma leads to progressive opacification of the cornea and subsequent loss of visual acuity.[7][8] There are three variants of MCD characterized by immunophenotype:
- Type 1: no detectable keratan sulfate in either the serum or cornea
- Type 1A: keratan sulfate is absent in the serum but stroma shows immunoreactivity to keratan sulfate antibodies
- Type 2: normal amounts of keratan sulfate in the serum and stroma
These three variants are clinically and histopathologically indistinguishable.
Signs and Symptoms[edit]
The first signs of MCD are cloudy regions that appear on the cornea during adolescence, although opacification may be noticed as early as the first decade. These minute, gray, punctate opacities will over time merge into larger areas, causing the entire corneal stroma to become opaque. Ultimately this results in severe visual impairment, generally before the 5th decade of life.[2]
While some individuals remain asymptomatic, initial symptoms typically consist of painful attacks with photophobia, foreign body sensations, and recurrent erosions.[7] Corneal sensitivity is also reduced.[2]
Diagnosis[edit]
Histopathological staining shows characteristic alcian blue-positive deposits.[7] Various imaging modalities, including confocal microscopy and ocular coherence tomography, can provide information about the changes within the cornea and may be suitable replacements for tissue biopsy and excision.[8]
Treatment and Prognosis[edit]
When visual acuity is impacted, various forms of keratoplasty are often indicated. While corneal transplanthas traditionally been the standard treatment, less-invasive surgical techniques such as deep anterior lamellar keratoplasty and photo-therapeutic keratectomy are increasingly playing a role in management of MCD.[8] While post-operative prognosis is favorable, reoccurrences may occur.[7]
Various gene therapies, including enzyme replacement therapy and gene-targeting therapy, remain a potential future treatment modality for MCD.[8]
See also[edit]
References[edit]
- ^ Groenouw A. Knötchenförmige Hornhauttrübungen (noduli corneae). Arch Augenheilkunde. 1890;21:281–289.
- ^ a b c Klintworth GK (2009). "Corneal dystrophies". Orphanet J Rare Dis. 4: 7. doi:10.1186/1750-1172-4-7. PMC 2695576. PMID 19236704.
- ^ al Faran, M. F.; Tabbara, K. F. (January 1991). "Corneal dystrophies among patients undergoing keratoplasty in Saudi Arabia". Cornea. 10 (1): 13–16. ISSN 0277-3740. PMID 2019101.
- ^ a b Jonasson, F.; Johannsson, J. H.; Garner, A.; Rice, N. S. (1989). "Macular corneal dystrophy in Iceland". Eye. 3 ( Pt 4) (4): 446–454. doi:10.1038/eye.1989.66. ISSN 0950-222X. PMID 2606219. S2CID 7010862.
- ^ Pandrowala, Hijab; Bansal, Aashish; Vemuganti, Geeta K.; Rao, Gullapalli N. (August 2004). "Frequency, distribution, and outcome of keratoplasty for corneal dystrophies at a tertiary eye care center in South India". Cornea. 23 (6): 541–546. doi:10.1097/01.ico.0000126324.58884.b9. ISSN 0277-3740. PMID 15256989. S2CID 24467047.
- ^ Musch, David C.; Niziol, Leslie M.; Stein, Joshua D.; Kamyar, Roheena M.; Sugar, Alan (2011-09-01). "Prevalence of corneal dystrophies in the United States: estimates from claims data". Investigative Ophthalmology & Visual Science. 52 (9): 6959–6963. doi:10.1167/iovs.11-7771. ISSN 1552-5783. PMC 3175990. PMID 21791583.
- ^ a b c d Singh, Shalini; Das, Sujata; Kannabiran, Chitra; Jakati, Saumya; Chaurasia, Sunita (June 2021). "Macular Corneal Dystrophy: An Updated Review". Current Eye Research. 46 (6): 765–770. doi:10.1080/02713683.2020.1849727. ISSN 1460-2202. PMID 33171054. S2CID 226301889.
- ^ a b c d Aggarwal, Shruti; Peck, Travis; Golen, Jeffrey; Karcioglu, Zeynel A. (2018). "Macular corneal dystrophy: A review". Survey of Ophthalmology. 63 (5): 609–617. doi:10.1016/j.survophthal.2018.03.004. ISSN 1879-3304. PMID 29604391. S2CID 4533280.