Comparing methods of determining addition in presbyopes.

BACKGROUND: The use of plus lenses to compensate for the reduction in the range of accommodation associated with presbyopia, brings the near point of accommodation to a comfortable distance for near visual tasks. Our aim was to compare the tentative near addition determined using the most common procedures with the final addition prescribed in presbyopic patients. METHODS: Sixty-nine healthy subjects with a mean age of 51.0 years (range 40 to 60 years) were studied. Tentative near additions were determined using seven different techniques: dynamic retinoscopy, amplitude of accommodation (AA), age-expected addition, binocular fused cross-cylinder with and without myopisation, near duochrome, and balance of negative and positive relative accommodation. The power of the addition was then refined to arrive at the final addition. RESULTS: The mean tentative near additions were higher than the final addition for every procedure except for the fused cross-cylinder without initial myopisation and age-expected addition methods. These biases were small in clinical terms (less than 0.25 D) with the exception of the AA procedure (0.34 D). The intervals between the 95% limits of agreement differed substantially and were always higher than +/-0.50 D. CONCLUSIONS: All the techniques used displayed similar behaviour and provided a tentative addition close to the final addition. Due to the wide agreement intervals observed, the likelihood of error is high and supports the idea that any tentative addition has to be adjusted according to the particular needs of each patient. Among the methods examined here, we would recommend the age-expected procedure, as this technique produced results that correlated best with the final addition.

Ocular dominance diagnosis and its influence in monovision.

PURPOSE: To analyze the response of normal emmetropic subjects to different ocular dominance tests and to analyze the influence of this response in surgically induced monovision. DESIGN: A prospective study of diagnostic accuracy was carried out to analyze the different tests to determine ocular dominance, without a gold standard test. METHODS: Nine different tests were carried out in a group of 51 emmetropic subjects to determine both motor and sensory ocular dominance. For analysis, patients were divided into two groups according to age. Normal ophthalmologic examination results were the inclusion requirement, with normal binocular vision and good stereoacuity. RESULTS: A significant percentage of uncertain or ambiguous results in all tests performed was found, except in the hole-in-card and kaleidoscope tests. When the tests were compared, two by two, the correlation or equivalence found was low and was much lower if tests were compared three by three. CONCLUSIONS: No clear ocular dominance was found in most studied subjects; instead, there must be a constant alternating balance between both eyes in most emmetropic persons, but not in those with pathologic features. This fact would explain the great variability both between and within different kinds of tests. Also, it would establish that the monovision technique is well tolerated in most patients, with unsuccessful results only in those patients with strong or clear dominance. Consequently, it seems appropriate to evaluate patient's dominance before monovision surgery to exclude those individuals with clear dominance.