Correlation and agreement between the Mohindra and cycloplegic retinoscopy techniques in children

PURPOSE

As an objective technique to assess refractive status, retinoscopy is particularly useful in children. The Mohindra technique (RM) is an alternative for those patients not good candidates for cycloplegic retinoscopy (RC). The aim of the present research was to compare both techniques and to determine the correlation and agreement of their measurements.

MATERIAL AND METHODS

A total of 47 boys and girls of ages ranging from 3 to 11 years old were included in the study. Cycloplegic (cyclopentolate 1%) and Mohindra retinoscopy were conducted in both eyes, and refraction was also assessed with an autorefractometre (AR). The results from the three techniques were compared and a correction factor between RM and RC was calculated.

RESULTS

Statistically significant differences were found between RM and RC (median of -0.42 D; p < 0.001) and between RM and AR (median of -0.42 D; p = 0.008), but not between RC and AR (median of 0.00 D; p = 0.758). A strong correlation was found between RM and RC (rho = 0.846; p < 0.001), although the Bland-Altman test revealed a larger difference between these techniques in patients with larger hyperopic refractive errors, with a correction factor of RC = 1.15 RM + 0.42.

CONCLUSIONS

The Mohindra technique may be considered a valid alternative to cycloplegic retinoscopy in patients of young age, with a good correlation between both techniques, albeit less agreement in patients with high hyperopic refractions.

Differential visual acuity - A new approach to measuring visual acuity

BACKGROUND

A novel type of acuity measurement, which we refer to as 'differential acuity', requires the observer to identify one unique target among three others which are identical. This is a proof of concept study aimed to determine if differential acuity is equivalent to standard measures of recognition acuity.

METHODS

To create a range of visual acuity, vision was optically blurred in sixteen adults with normal visual acuity. Visual acuity was then measured with the differential acuity targets in both crowded and uncrowded format, and compared with standard ETDRS acuity or with singly presented letters and uncrowded letters were analysed separately.

RESULTS

The visual acuity results for crowded and uncrowded letters were analysed separately. Repeated measures analysis of variance showed that when a crowded Sloan C had to be differentiated from three crowded Os (CvsO), the results were not significantly different from ETDRS acuity or from naming one of four letters presented centrally (Name4) (p<0.05). Similar results were found for uncrowded letters - the C versus O and Name4 gave similar visual acuity. The 95% limits of agreement between the naming and C versus O differential acuity measures were between 0.17 and 0.27 logMAR.

CONCLUSION

From this proof of concept study we conclude that differential acuity gives similar results to the ETDRS chart in adults. We infer that the comparable but cognitively simpler differential visual acuity task could be applied in clinical settings for young children or patients with developmental delay who cannot respond by naming or matching.