What is ectopia lentis?
Ectopia lentis is defined as displacement or malposition of the crystalline lens of the eye. The lens is supported in place by zonules attached to the wall of the eye: very fine fibers. Disruption or dysfunction of the zonular fibers of the lens, regardless of cause (trauma or heritable condition), causes ectopia lentis. The degree of zonular impairment determines the degree of lens displacement. Ectopia lentis may occur after trauma or may be associated with ocular or systemic disease. Ectopia lentis may be the first sign of a more serious systemic disease. Additionally, ectopic lentis can cause major complications within the eye, including significant refractive shifts, pupillary block glaucoma, retinal damage, and blindness.
Ectopia lentis and Ocular Diseases
Simple ectopia lentis – simple ectopia lentis can occur as a congenital disorder or as a spontaneous disorder later in life. Both are hereditary and can be inherited in an autosomal dominant or recessive pattern. Mutations resulting in simple ectopia lentis include mutations to the ADAMTSL4 gene located on chromosome 1 (recessive inheritance pattern) and the FBN1 gene located on chromosome 15 (dominant inheritance pattern). These mutations often result in irregularity and degeneration of the zonular fibers, leading to lens dislocation. Significant overlap exists between the genetics of simple ectopia lentis and the systemic diseases associated with ectopia lentis. The mutations to the FBN1 gene can also result in Marfan syndrome. Ectopia lentis is rarely caused by or associated with:
- Aniridia
- Congenital glaucoma
- Pseudoexfoliation syndrome
- Syphillis
- Retinitis pigmentosa
- Intraocular tumor
- Axenfeld Rieger syndrome
- Megalocornea
Ectopia Lentis and Systemic Diseases
Marfan syndrome – Marfan syndrome is the most common cause of heritable ectopia lentis, and ectopia lentis is the most frequent ocular manifestation of Marfan syndrome, occurring in approximately 75% of patients. Marfan syndrome is an autosomal dominant disease resulting from various mutations to the fibrillin-1 gene located on chromosome 15. It is thought that the increased incidence of ectopia lentis with Marfan syndrome is due to altered fibrillin microfibrils leading to incompetent zonular fibers and structural abnormalities of the lens capsule.
Homocystinuria – Homocystinuria is the second most common cause of heritable ectopia lentis. Homocystinuria is an autosomal recessive metabolic disorder most often caused by a near absence of cystathionine b-synthetase. It is associated with intellectual disability, osteoporosis, chest deformities, and increased risk of thrombotic episodes. Lens dislocation occurs in 90% of patients, and is thought to be due to decreased zonular integrity due to the enzymatic defect.
Other systemic diseases associated with ectopia lentis:
- Weill-Marchesani syndrome
- Sulfite oxidase deficiency
- Hyperlysinemia
- Ehlers-Danlos syndrome
- Sturge-Weber syndrome
- Mandibulofacial dysostosis
- Wildervanck syndrome
- Conradi syndrome
- Pfaundler syndrome
- Crouzon syndrome
- Pierre Robin syndrome
- Sprengel deformity
Video Ectopia Lentis Surgery
This 46 year old woman has had progressive vision loss from ectopia lentis which is more difficult to correct. Also, her other eye had surgery 5 years ago and she is having a lot of trouble with the anisometropia (imbalance between the two eyes). She was corrected to about 20/60 before the surgery and within 2 months of surgery was 20/25 uncorrected with good function. She had developed an inadvertent filter bleb in the fellow eye following surgery so her IOL was placed through a corneal incision rather than a scleral tunnel. She also requested the ACIOL to balance the two eyes.