The core function of optometrists is the prescribing of spectacles to alleviate symptoms and improve visual function, yet the criteria for prescribing spectacles have received little attention in the clinical and scientific literature. The decision whether to correct a small refractive error in particular can be difficult, for there is no clear cut-off point between normality and abnormality and there is therefore a need for prescribing guidelines to aid this decision. However, in a previous paper we found the current prescribing guidelines to be conflicting and rarely based on clinical research (O’Leary and Evans 2003). In addition, this survey of optometrists discovered that a wide variety of criteria were used when deciding whether to prescribe, particularly in the case of low refractive errors where visual acuity (VA) may have limitations as an indicator of benefit. Several other more recent publications have highlighted the lack of uniformity in prescribing criteria for hypermetropia (Cotter 2007; Farbrother 2008; Leat 2011; Reiter et al. 2007). Our previous research showed that in cases of low refractive errors optometrists are likely to rely on symptoms when deciding whether to prescribe (O’Leary and Evans 2003). However, although eliminating symptoms is obviously important, it has been shown that symptoms relating to low refractive errors can be vague and non-specific (Brookman 1996) and that the presence of symptoms may not correlate with the magnitude of the anomaly found (O’Leary and Evans 2003) or the final prescription given (Ball 1982b). Additionally, practitioners might wish to prevent symptoms occurring in the first place, and some patients, especially children, may not recognise symptoms until they are eliminated. In a previous paper we used a rate of reading test to investigate at what point it became beneficial to correct heterophoric anomalies (O’Leary and Evans 2006). In the research described here we have used the same dynamic reading test to investigate at what point correcting small degrees of hypermetropia, presbyopia and astigmatism becomes beneficial.