Background  

To examine if standardized reading charts with highly comparable test items can be used for evaluating impairments in the monocular reading performance of children with microstrabismic amblyopia characterized by a small angle of squint with less than 5 degrees.

Methods  

The reading performance of 22 children (mean age: 11.7±1.6 years) with unilateral microstrabismic amblyopia was evaluated monocularly in both eyes, using standardized reading charts for the simultaneous determination of reading acuity and speed. The print sizes of the highly comparable sentence optotypes were logarithmically graded, providing constant geometric proportions for all testing distances in order to control contour interaction. All children were under continuous amblyopia therapy.

Results  

In the amblyopic eyes, reading acuity and maximum reading speed were significantly impaired when compared to the sound fellow eyes (P<0.001). In respect of the maximum reading speed, a mean inter-ocular difference of 33±19 words per minute was found, revealing functionally relevant deficits in monocular reading performance. The amblyopic eyes achieved only a significantly reduced reading acuity (mean inter-ocular difference: LogRAD 0.5±0.24; P<0.001). In eight children, the amblyopic eyes achieved a best-corrected visual acuity of LogMAR 0.0 or better: in respect of the visual acuity, there was no significant inter-ocular difference, but reading acuity and maximum reading speed were significantly impaired when compared to the fellow eyes.

Conclusions  

Microstrabismic amblyopia was associated with significant impairment of reading acuity and speed in treated amblyopes, even in those with no persistent acuity deficit. To improve treatment addressing these functional deficits, reading performance should be monitored over time using standardized reading tests, which provide essential information about functionally relevant reading impairments.