No prospective double-masked study has evaluated whether low astigmatism benefits
or harms patients with presbyopia, whose intermediate and near vision might theoretically
benefit from enhanced depth of focus provided by astigmatism. The purpose of the first
Myopic Astigmatism and Presbyopia (MAP I) study was to determine whether low myopic
astigmatism enhances or harms the visual acuity, stereopsis, or quality of life in
patients with presbyopia.
Prospective, randomized, double-masked, crossover design clinical trial.
Fifteen patients with presbyopia aged 45 to 68 years were recruited from an academic
center population. These patients were given a baseline eye examination, including
manifest refraction, Early Treatment of Diabetic Retinopathy Study (ETDRS) logarithm
of minimal angle of resolution (logMAR) visual acuity at distance, intermediate, and
near, accommodative amplitudes, and stereo vision. Each patient was then cycled in
random order through three masked pairs of soft contact lenses. The power of each
contact lens pair was calculated by the subtraction method to maintain a spherical
equivalent of -0.5 diopters, while providing either no astigmatism (spherical arm,
SPH), 1 diopter of with-the-rule (WTR) astigmatism, or 1 diopter of against-the-rule
(ATR) astigmatism. Actual refractive errors produced were measured by masked examiner.
Outcomes measured at the end of 1 week of usage of each contact lens arm were binocular
(ETDRS) logMAR visual acuity at three distances (far [4 m], intermediate [1 m], and
near [33cm]); near stereoacuity, using the quantitative Titmus Stereotest; and quality
of life, measured using the Refractive Status and Vision Profile (RSVP), a standardized
questionnaire.
Visual acuity results across the three arms were similar. However, 1-m logMAR visual
acuity was better for the spherical arm than either astigmatic arm (-0.06 SPH, +0.01
WTR, +0.02 ATR). Near (33 cm) and distance (4 m) acuities were similar across arms.
Stereoacuity was better in ATR than WTR (50 vs 102 seconds, P =.01). Subjects preferred
SPH slightly over the WTR astigmatic arm by the RSVP quality-of-life survey instrument
(101 vs 104, P =.05). Other intergroup comparisons showed no difference in RSVP scores.
This study has demonstrated that intermediate distance acuity and refractive quality
of life are slightly better with spherical low myopic refractive error vs either astigmatic
arm. Near and far distance acuity were unaffected by low myopic astigmatism compared
with spherical low myopia. Near stereopsis was best in the ATR arms, but this did
not produce better near visual acuity or RSVP quality of life.