Sir,

We read with interest the above article by Nainiwal et al1 as it was the first report to date of vitreous haemorrhage resulting from dengue fever. A few points in the article however, require clarification and may be of relevance to the pathogenesis.

The authors have not clearly outlined the timeline of the systemic manifestations of the disease and the associated ocular symptoms and signs. The patient presented with ‘diminution of vision in right eye since 4 months’, ‘she had high-grade fever … 2 days before developing eye problems’ and that ‘she was referred to us after her general condition had improved’. We wish to clarify whether she underwent an ophthalmic assessment only 4 months after onset of dengue. Dengue haemorrhagic fever typically presents at time of defervescence some days after the onset of dengue. As such it would be useful to know when exactly from onset of the fever the patient developed ocular symptoms. Documented serum platelet levels on the day of onset of her ocular symptoms would have added further analytical value to the case report.

Recent case series have reported the mean interval between onset of visual symptoms and systemic manifestations of dengue fever to be in the range of 6.82 and 7.33 days. Two other case reports4, 5 have reported a mean interval of 3 days. Onset of ocular symptoms around 7 days after systemic symptoms lends well to the possible immunologic basis of dengue ocular disease.2

As it appears that the patient was not examined during the early onset of her visual symptoms, vitreous haemorrhage could have resulted at a later stage from a pre-existing dengue-related retinal haemorrhage—a known documented finding in dengue-related eye disease.2

Dengue fever is currently endemic in Singapore and we are conducting a prospective study of ocular manifestations in patients infected with dengue virus. To date, we have had one dengue patient with bilateral vitreous haemorrhages.

However, in our case the vitreous haemorrhages were very small and not the dominant finding. Also interestingly our patient's ocular symptoms arose at the nadir of her platelet count (29 000/cc) on day 8 of the disease. There could thus be two underlying mechanisms explaining the ocular signs in dengue eye disease. One could be immunologic with possible immune complex deposition in retinal vessels. The other could be an increased bleeding tendency resulting from decreased platelet counts.