Avellino Corneal Dystrophy (ACD) is also known as Granular Corneal Dystrophy (GCD) type II.
It was discovered for the first time in 1988, in families who emigrated to the U.S from the province of Avellino, Italy. Before 1988, ACD was loosely referred to as GCD, without distinguishing between GCD Type I and GCD Type II.
ACD is a disease where opacity occurs at the center of corneas
It is an autosomal dominant hereditary disorder. The disease usually develops slowly; however, it varies according to the individual patient’s age, lifestyle, and living environment. There is currently no distinctive treatment for the disease.
The genetic mutation, is known to cause the rapid development of the disease due to the ultraviolet light (UVB) or corneal injuries.
The BIGH3 gene is located at the human body’s fifth-chromosome short arm and is involved in the production of the BIGH3 protein, which consists of 683 amino acids. This gene is known to be activated when injured or stimulated, thereby producing the BIGH3 protein.
There are three Genotypes of Avellino Gene Mutation:
| Genotype | Genotype Name |
|---|---|
| HH | Homozygous |
| HN | Heterozygous |
| NN | Normal |
With a calculated ACD prevalence rate at 1/870 persons, the LASIK surgeons benefit from this test to protect them from the risk of post-operative complications as well as provide the test pre-operative to identify patients at risk (or carrier of the gene).
HN : Heterozygous
HN : Heterozygous
HH : Homozygous
HH : Homozygous
The HN Heterozygous individuals are generally not detected through Slit-lamp examination. Therefore, the ACD gene test is the only way to know for certain if the patient is pre-dispositioned with this autosomal dominant trait.
For many patients, their only symptom is visually insignificant corneal opacities. However, extensive exposure to Ultraviolet Light or corrective vision laser Lasik surgeries can rapidly exacerbates the corneal opacity. Both the Homozygous and Heterozygous patients are advised not to receive laser surgeries.
Therefore, the AGDS™ (Avellino – GENE Detection System) Test is becoming one of the preferred pre-screening tests by Ophthalmologists for evaluating patients who seek corrective vision laser surgeries.
The HH Homozygous patients have severe corneal opacities and decreased visual acuity from childhood. Even after Phototherapeutic Keratectomy (PTK), corneal deposits reappear in 10 to 18 months after surgery.
Phototherapeutic keratectomy (PTK)
The disease shows earlier and more severe recurrence as the treatments are repeated, which requires further PTK.
Corneal grafting has been the usual treatment for improving vision in the severe ACD patients. The cornea is clear right after surgery however, deposits start to reappear in the corneal graft within 12 to 24 months, with the same pattern.
Immediately after PTK
After 3 months :
Recurrence of the granular deposition
After 3 year : Severe granular deposition
ACD patient after LASIK
Thirty-eight years old patient / Seven years after LASIK
Treatment Options
The eye treatment medical community does not have a cure for the Avellino Corneal Dystrophy. Therefore early AGDS™ testing is advised for individuals considering LASIK or for people working or living in high UVB environments.
Phototherapeutic keratectomy (PTK), lamellar keratoplasty (LK), deep lamellar keratoplasty (DLKP) and penetrating keratoplasty (PKP) can improve vision at least temporarily but deposits tend to reoccur.