Atoll sign in posterior lenticonus: A case report of bilateral posterior lenticonus with review of literature

Posterior lenticonus is a rare progressive disease characterized by protrusion of posterior lens capsule along with lens cortex into the vitreous cavity. Posterior lenticonus is more common but present unilaterally unlike anterior lenticonus, which presents bilaterally. Posterior lenticonus is a common cause of unilateral infantile cataract but is a very rare cause of bilateral cataract. Diagnosis is mainly clinical but can be difficult in asymptomatic patients; oil drop sign (in mild posterior lenticonus) and fish tail sign (lenticular cortex hanging in vitreous cavity after posterior capsular dehiscence) are described in posterior lenticonus. We are proposing an atoll sign in advanced case of posterior lenticonus with intact posterior capsule on slit lamp examination. The positive atoll sign will have more favorable prognosis since posterior capsule is intact, hence posterior chamber intraocular lens implantation will be more feasible with better visual prognosis as was the case with our patient.