PubMed · 14164190
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P KNAPP. 1964. STRABISMUS.. https://doi.org/10.1001/archopht.1964.00970020267024
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PURPOSE: To evaluate the effect of reducing the hyperopic correction on the state of binocular accommodative response in fully accommodative esotropia and to determine the "comfortable" amount of reduction in hyperopic correction. DESIGN: A cohort study. METHODS: Hyperopic corrections of children with a baseline refractive error of +1.50 to +5.0 diopters were gradually reduced in 0.50-diopter increments. Binocular accommodative ability was assessed by dynamic retinoscopy (monocular estimate method). Similar binocular accommodative responses were ascertained among patients with a baseline hyperopic correction of < or =3.0 of hyperopia and >3.0 of hyperopia, and patients were divided into two groups, group 1 (13 patients) and group 2 (18 patients), accordingly. RESULTS: After a reduction of 2.0 diopters in group 1 and 1.0 diopter in group 2, there was a decrease in accommodative response initially in the nondominant eye, accompanied by the dominant eye with a further reduction of 0.50 diopter. To overcome the bilateral accommodative lag, a reinstatement of a 0.50-diopter stronger hyperopic correction was required. Patients in group 1 tolerated a mean undercorrection of 2.37 diopters, and 77% were weaned from their spectacles. All of the children in group 2 were dependent upon spectacles at the completion of the study period. The final spectacle worn was a median of -1.67 diopters less than their full cycloplegic refraction. CONCLUSIONS: A complete binocular accommodative ability seems to be a prerequisite for the establishment of "comfortable" hyperopic undercorrections. It does not seem to be a reasonable approach to consider further reductions in hyperopic correction in the presence of a bilateral decreased accommodative performance.
Accommodation has long been suspected to be involved in the development of myopia because near work, particularly reading, is known to be a risk factor. In this study, we measured several dynamic characteristics of accommodative behavior during extended periods of reading under close-to-natural conditions in 20 young emmetropic and stable myopic subjects. Accommodative responses, errors, and variability (including power spectrum analysis) were analyzed and related to accommodative demand and subject refractive error. All accommodative behaviors showed large inter-subject variability at all of the reading demands. Accommodative lags and variability significantly increased with closer demands for all subjects (ANOVA, p<0.05). Myopes had significantly greater variability in their accommodation responses compared to emmetropes (ANOVA, p<0.05) and had larger accommodative lags at further reading distances (unpaired t test p<0.05). Power spectrum analysis showed a significant increase in the power of accommodative microfluctuations with closer demands (ANOVA, p<0.05) and with increasing myopia at the closest reading demand (ANOVA, p<0.01). The difference in the stability of the accommodative behavior between individuals with different refractive states suggests a possible relationship between variability in accommodation and the development of myopia.
AIM: To determine whether eyes implanted with the Lenstec KH-3500 "accommodative" intraocular lenses (IOLs) have improved subjective and objective focusing performance compared to a standard monofocal IOLs. METHODS: 28 participants were implanted monocularly with a KH-3500 "accommodative" IOL and 20 controls with a Softec1 IOL. Outcome measures of refraction, visual acuity, subjective amplitude of accommodation, objective accommodative stimulus response curve, aberrometry, and Scheimpflug imaging were taken at approximately 3 weeks and repeated after 6 months. RESULTS: Best corrected acuity with the KH-3500 was 0.06 (SD 0.13) logMAR at distance and 0.58 (0.20) logMAR at near. Accommodation was 0.39 (0.53) D measured objectively and 3.1 (1.6) D subjectively. Higher order aberrations were 0.87 (0.85) microm and lower order were 0.24 (0.39) microm. Posterior subcapsular light scatter was 0.95% (1.37%) greater than IOL clarity. In comparison, all control group measures were similar except objective (0.17 (0.13) D; p = 0.032) and subjective (2.0 (0.9) D; p = 0.009) amplitude of accommodation. Six months following surgery, posterior subcapsular scatter had increased (p<0.01) in the KH-3500 implanted subjects and near word acuity had decreased (p<0.05). CONCLUSIONS: The objective accommodating effects of the KH-3500 IOL appear to be limited, although the subjective and objective accommodative range is significantly increased compared to control subjects implanted with conventional IOLs. However, this "accommodative" ability of the lens appears to have decreased by 6 months post-surgery.