Intended for healthcare professionals

Editorials

A little bit of measles does you good

BMJ 1999; 319 doi: https://doi.org/10.1136/bmj.319.7201.4 (Published 03 July 1999) Cite this as: BMJ 1999;319:4

Measles vaccination and the declining incidence of esotropia

Frank Shann's editorial 'A little bit of measles does you good' (1)
highlights several unexpected effects of mass measles vaccination. No
more satisfactory explanation has been advanced for an apparently marked
decline in the incidence of childhood esotropia (convergent squint) than
that it may be due to a large reduction in the incidence of measles.

Figures for the incidence of childhood esotropia, with a peak at age
3 to 4 years, are difficult to gather, but there is general agreement that
fewer cases present in the United Kingdom than a generation ago. More
easily verified is a marked decrease in the past 25 years in the number of
squint
operations performed. Previously about 2 squint corrections were done on
a typical 'general' ophthalmic operating list; now these operations are
becoming something of a rarity, though increased awareness of consecutive
divergence as a consequence of over-zealous squint correction has also
contributed to the decline in the number of operations.

The principal factors determining the onset of childhood esotropia
are genetic influences, refractive errors (usually hyperopia) and a high
accommodative convergence/accommodation ratio (2). The precipitating
cause of a child with normal, though fragile, binocular function
developing a squint has often been considered to be a systemic illness.
Measles used to be common at this age - now it is rare. Whether it is the
stress induced by
the illness or, more specifically, a subclinical encephalitis is unknown
(3), but the decline in measles and that of concomitant esotropia may be
connected.

Robin Finlay

Consultant ophthalmic surgeon

Royal United Hospital
Bath BA1 3NG

1 Shann F. Editorial: A little bit of measles does you good. BMJ
1999;319:4-5.

2 Parks MM. Abnormal accommodative convergence in squint. Arch
Ophthal 1958;59:364-80

3 Taylor D. Paediatric ophthalmology, Blackwell Scientific
Publications, 1990;625

Competing interests: No competing interests

08 July 1999
Robin Finlay