Posterior subcapsular cataract is a relatively common type of cataract which develops in the posterior capsule of the lens and causes visual impairment, especially while reading. It is reported to happen rapidly in individuals on steroids, or amongst patients with diabetes, high-grade myopia or retinitis pigmentosa. It can occur alone or may be associated with other lens opacities. An ophthalmic examination and slit-lamp evaluation are required to diagnose its presence.
Posterior subcapsular cataract (PSC) is a type of lenticular opacity. It can occasionally be associated with other lens opacities like a nuclear or cortical cataract. The incidence of isolated PSC is low and has been reported to be 1-2% in patients between the fifth and eighth decades of life  while it is 7% in the pediatric population . Although PSC can be idiopathic, it reported to be associated with several medical conditions  such as myopia , diabetes , dermatological diseases , long-term steroid use   , retinitis pigmentosa , ocular injury , smoking  and vitamin D deficiency . It starts as a small opacity on the posterior aspect of the lens and in the path of light.
A majority of the PSC in pediatric patients are unilateral but can be bilateral in adults . Patients present with difficulty in reading, halos or a glare around lights at night and clouding of vision in the presence of illumination which improves in presence of low light. However, visual acuity is maintained until a nuclear cataract develops. Based on the signs and symptoms, PSC is classified as:
PSCs can be of two types: progressive or stationary . Progressive PSC is associated with radiating opacities in the posterior cortex with symptoms worsening gradually as the extensions expand peripherally. The stationary variant is a central opacity surrounded by concentric rings and resembles a bull's eye. It is located in the posterior capsule and is associated with good visual acuity.
The workup in PSC consists of a thorough history, specifically for pre-existing medical comorbidities and a detailed ophthalmological examination. Visual acuity testing is followed by a slit-lamp exam to evaluate the opacity and exclude anterior vitreous involvement or adherence of the anterior capsule. Slit-lamp images and retro-illumination are used according to the 'Lens Opacities Classification System (LOCS)' to grade cataracts while A-scan ultrasound, keratometry, and intra-ocular pressures are routinely calculated prior to cataract surgery.
A complete blood count, a plain X-ray chest and other tests depending upon associated comorbidities are also required prior to surgery. An electrocardiogram may be indicated to rule out cardiac diseases.
An anterior segment optical coherence tomography (OCT) performed preoperatively helps to grade cataracts, identify patients with PSC who are at risk of posterior capsular rupture; to plan the surgery and counsel the patients  .