What did the left eye say to the right eye?
You look different.
Have you met anyone in the clinic who comes to you & says that “I am a complete spook in photographs.” This phenomenon of shining white pupil is nothing but an abnormal white pupillary reflex which is also known as leukocoria.
Normally when light passes through the pupil it is reflected as reddish-orange glow. In leukocoria, the pupils shine white. This condition can be unilateral or bilateral depending on the etiology. Any abnormality in the path of normal red reflex, be it retina, lens, vitreous will lead to an altered reflex.
Leukocoria or ‘white pupillary reflex’ is seen in many disorders. Let’s discuss most important ones NEET-PG or NEXT point of view. In MCQ you may get a clinical case along with image showing leucocoria. How to diagnose? For this you must be knowing causes of leucocoria & key features of these causes based on which they can be diagnosed.
Retinoblastoma presents as leukocoria. The most important fact to remember is that retinoblastoma essentially presents in the pediatric age group. It is the most common intraocular tumor in children where its average age of diagnosis is 18 months (typically less than 5 yrs age). Characteristic feature on USG is that tumor is a soft tissue mass with calcification & necrosis which often helps it to differentiate it from PHPV.
Persistent Hyperplastic Primary Vitreous (PHPV) is a developmental defect in which the embryonic structures in eye (hyaloid arteries & primary vitreous) fail to regress. It also presents as unilateral leukocoria. But in such cases h/o previously normal red reflex will not be there. USG reveals a fibrous vascular band extending from the posterior aspect of the lens to optic disc. Remember that fibrous tissue is also seen behind the lens in cases of Retinopathy of prematurity (ROP). But ROP is seen in premature infants born before 31 weeks of gestation or full-term infants if they received an excess of oxygen in the NICU. It occurs due to abnormal growth of blood vessels in the retina. They can also present as cases of leukokoria due to retinal detachment & retrolental fibroplasia.
While differentiating various causes of leukocoria, case history plays a very important role. For example, if there is H/o trauma in the eye presenting with leukocoria, the cause can be cataract. Also, past histories which help to identify prenatal infections such as TORCH may direct diagnosis towards a congenital cataract (say, as a part of Congenital Rubella Syndrome). Congenital cataracts can also be associated with certain chromosomal abnormalities, metabolic & systemic conditions.
Ocular Toxocariasis can also present as unilateral leukocoria. It is a zoonotic disease caused by infections by roundworms. Such cases always have h/o exposure to pets.
Coats disease presents mostly as unilateral leukocoria. It is an ocular disorder where there is abnormal development of blood vessels in the retina. The blood vessels may be dilated or even leak which may lead to intraretinal or subretinal exudations. Such exudations can cause retinal detachment. Again age gives clue to the diagnosis. Age of diagnosis in Coat’s disease is 5 years. Due to retinal exudations, the pupil appears yellowish.
I hope this little piece of information cuts short the time required to solve lengthy questions in NEXT & NEET-PG exams.
Dr. Kainat Moosa
Medical Content Writer