Posterior Lenticonus

Definition: Posterior lenticonus is a developmental anomaly of the lens in which the posterior portion of the lens bulges outward in a cone-shape.
Incidence/Prevalence: Posterior lenticonus is much more common than anterior lenticonus. Sporadic and inherited cases have been described, particularly X-linked and autosomal dominant inheritance patterns. Inherited cases are more common than sporadic cases.
Etiology: Associations include microcornea, anterior lentiplanus, glycinuria and Duane’s syndrome. [Ref 1] Although Alport’s syndrome is mostly associated with anterior lenticonus, simultaneous anterior and posterior lenticonus have been described in Alport’s syndrome.[Ref 2] It has been written that the abrupt thinning in the posterior capsule at the point of the lenticonus is the cause of the bulge on the basis of mechanical issues. This dogma of course does not adequately explain the inheritance patterns or associations! The association with Mittendorf's dot is particularly provocative.
Clinical Findings: Posterior lenticonus may be present at birth or develop in the following months. Amblyopia may be present. Posterior lenticonus may occur as an isolated ocular finding. There is a slight female predominance. Posterior lenticonus most commonly is unilateral but may be bilateral. There may be a high degree of astigmatism. Retinoscopy will show a distorted myopic reflex. Oblique lighting with the slit lamp is helpful to see the cone shape. With progression the cone and surrounding lamellae may opacify.
Gross and Histopathology: Histologic reports feature a thin posterior lens capsule. There is one report of an associated posterior subcapsular cataract. In the photograph (arrow 1) a rounded bulging of the posterior capsule is seen. This might be better termed lentiglobus because it is not truly cone shaped.
Treatment: If visually significant (opacified) or if amblyopia is present, lens removal is indicated. An anterior capsulorhexis with clear lens removal by aspiration and IOL placement within the capsular bag is the usual treatment. Often removal of the lens will restore vision. [Ref 3]
References
1. Surv Ophthalmol. 2003 Mar-Apr;48(2):125-44.
2. Indian J Ophthalmol. 2005 Sep;53(3):212-3.
3. J Cataract Refract Surg. 2006 Feb;32(2):261-3.