Fall 2012 - Indiana University School of Optometry

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tested 40 subjects who ranged in age from 9 to 38 years. A mean CA/C ratio was not reported, but based on a figure in the paper, CA/C ratios with Nott retinoscopy ranged from close to 0 to about 0.06 D/Δ, with a median of about 0.035 D/Δ. Eleven of their subjects had CA/C ratios determined by both dynamic retinoscopy and an optometer in a haploscopic arrangement. The coefficient of correlation of Nott retinoscopy CA/C with optometer CA/C was 0.79. Comments Mean CA/C ratios from different studies are summarized in Table 1. All of the studies in which accommodation was measured with the BCC or with dynamic retinoscopy found mean (or median) CA/C ratios to be less than 0.1 D/Δ and sometimes much less than that. Many of the studies in which accommodation was measured with an optometer found mean CA/C ratios to be more than 0.1 D/Δ. Clinical procedures that would allow the determination of CA/C ratios exist today. CA/C ratios may have some promise for analysis of binocular vision problems with further research and development. Some optometrists have suggested graphical procedures for analysis of AC/A and CA/C ratios. 1,4,17,18 The application of CA/C ratios as a useful clinical analytical tool would require standardization of measurement methods, establishment of norms, and development of analysis procedures in concert with AC/A ratios and other clinical findings. References 1. Schor CM, Narayan V. Graphical analysis of prism adaptation, convergence accommodation, and accommodative convergence. Am J Optom Physiol Opt 1982;59:774-784. 2. Schor CM. Fixation disparity and vergence adaptation. In: Schor CM, Ciuffreda KJ, eds. Vergence Eye Movements: Basic and Clinical Aspects. Boston: Butterworth-Heinemann, 1983:465-516. Study BCC Dynamic Retinoscopy Optometer Kent (n=17) 0.13 (0.06) Hung et al. (22 asymp.) 0.12 (0.05) Hung et al. (21 symp.) 0.11 (0.05) Rosenfield & Gilmartin (n=30) 0.06 (SD not given) Kotulak et al. (n=16) 0.10 (0.08) Nonaka et al. (78 with exo) 0.08 (0.04) Brautaset & Jennings (10 with CI) 0.14 (0.02) Fukushima et al. (n=16) 0.09 (0.04) Schor & Narayan (n=5) 0.087 (0.032) 0.08 (0.025) (Nott) 0.075 (0.025) Tsuetaki & Schor (n=6) 0.045 (0.022) (Nott) 0.055 (0.021) Daum et al. (78 asymp.) 0.06 (0.05) (MEM) Daum et al. (22 symp.) 0.07 (0.06) (MEM) Wick & Currie median about 0.035 (Nott) median about 0.04 Table 1 . Mean CA /C ratios in diopters per prism diopter. Standard deviations are in parentheses. Separate columns indicate the method by which accommodation was measured. 3. Schor C. The influence of interactions between accommodation and convergence on the lag of accommodation. Ophthal Physiol Opt 1999;19:134-150. 4. Daum KM, Rutstein RP, Houston G 4th, Clore KA, Corliss DA. Evaluation of a new criterion of binocularity. Optom Vis Sci 1989;66:218-228. 5. Fry GA. Significance of fused cross cylinder. Optom Weekly 1940;31:16-19. 6. Goodson RA, Afanador AJ. The accommodative response to the near point cross cylinder test. Optom Weekly 1974;65:1138-1140. 7. Kent PR. Convergence accommodation. Am J Optom Arch Am Acad Optom 1958;35:393-406. 8. Hung GK, Ciuffreda KJ, Semmlow JL. Static vergence and accommodation: population norms and orthoptics effects. Documenta Ophthalmologica 1986;62:165-179. 9. Rosenfield M, Gilmartin B. Assessment of the CA/C ratio in a myopic population. Am J Optom Physiol Opt 1988;65:168-173. 10. Kotulak JC, Morse SE, Rabin JC. Optical compensation for night myopia based on dark focus and CA/C ratio. Invest Ophthalmol Vis Sci 1995;36:1573- 1580. 11. Nonaka F, Hasebe S, Ohtsuki H. Convergence accommodation to convergence (CA/C) ratio in patients with intermittent exotropia and decompensated exophoria. Jpn J Ophthalmol 2004;48:300-305. 12. Brautaset RL, Jennings AJ. Effects of orthoptic treatment on the CA/C and AC/A ratios in convergence insufficiency. Invest Ophthalmol Vis Sci 2006;47:2876- 2880. 13. Fukushima T, Torii M, Ukai K, Wolffsohn JS, Page 19 ... Vol. 15, Nos. 1/2 ... 2012 ... Indiana Journal of Optometry ......................................................
Gilmartin B. The relationship between CA/C ratio and individual differences in dynamic accommodative responses while viewing stereoscopic images. J Vis 2009;9(13):21,1-13. 14. Rosenfield M, Ciuffreda KJ, Chen HW. Effect of age on the interaction between the AC/A and CA/C ratios. Ophthal Physiol Opt 1995;15:451-455. 15. Tsuetaki TK, Schor CM. Clinical method for measuring adaptation of tonic accommodation and vergence accommodation. Am J Optom Physiol Opt 1987;64:437-449. 16. Wick B, Currie D. Convergence accommodation: Laboratory and clinical evaluation. Optom Vis Sci 1991;68:226-231. 17. Wick B, London R. Analysis of binocular visual function using tests made under binocular conditions. Am J Optom Physiol Opt 1987;64:227-240. 18. Goss DA. Pratt system of clinical analysis of accommodation and convergence. Optom Vis Sci 1989;66:805-806. .................................................... Indiana Journal of Optometry ... 2012 ... Vol. 15, Nos. 1/2... page 20
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Fall 2012 - Indiana University School of Optometry

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