Do bifocals reduce accommodative amplitude in convergence excess esotropia?
BACKGROUND
As therapy with bifocal lenses can generate a condition of acquired hypo-accommodation, we assessed the results of bifocal therapy in children with non-refractive accommodative esotropia in whom near point of accommodation (NPA) was measured before the prescription of the lenses and at the end of the study.


METHODS
We examined 28 consecutive patients orthophoric for far, but with esotropia due to excess convergence for near (group 1), and 28 matched controls, orthophoric for far and near (group 2). The patients were prescribed bifocal lenses between the age of 5 and 8. The NPA was measured at time zero and after 4 years of follow-up in both groups.


RESULTS
NPA values, measured at time 0, were lower than average (10 dioptres) in ten of the 28 patients in group 1, and increased over the 4 years of follow-up without exceeding 10 dioptres. Only one of the other 18 patients in group 1, with normal NPA, had a lower value at the end of the study, although the values were still above 10 dioptres.


CONCLUSIONS
In several patients, excessive convergence is secondary to the extra accommodative effort required due to the presence of a primitive NPA deficit. In these subjects, the prognosis can be made on the basis of NPA measurement, and treatment with bifocal lenses will always be required to compensate. Furthermore, the parents of these small patients should be informed, even before the prescription of bifocals, that prospective surgery of medial rectus muscles will not eliminate the need for bifocals.
Ophthalmology Service, Department of Surgery and Anaesthesiology, University of Bologna, Bologna, Italy. michela.fresina@libero.it
Michela
M
Fresina
Costantino
C
Schiavi
Emilio C
EC
Campos
D000065:Accommodation, Ocular / Q000502:physiology*; D002648:Child; D002675:Child, Preschool; D003290:Convergence, Ocular / Q000502:physiology*; D004948:Esotropia / Q000503:physiopathology / Q000628:therapy*; D005139:Eyeglasses; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male