• Estimation of effective lens position using a method independent of preoperative keratometry readings.

      Dooley, Ian; Charalampidou, Sofia; Nolan, John; Loughman, James; Molloy, Laura; Beatty, Stephen; Department of Ophthalmology, Waterford Regional Hospital, Institute of Eye, Surgery, Dublin, Ireland. iandooley@eustace.net (2012-02-01)
      PURPOSE: To evaluate the validity of a keratometry (K)-independent method of estimating effective lens position (ELP) before phacoemulsification cataract surgery. SETTING: Institute of Eye Surgery, Whitfield Clinic, Waterford, Ireland. DESIGN: Evaluation of diagnostic test or technology. METHODS: The anterior chamber diameter and corneal height in eyes scheduled for cataract surgery were measured with a rotating Scheimpflug camera. Corneal height and anterior chamber diameter were used to estimate the ELP in a K-independent method (using the SRK/T [ELP(rs)] and Holladay 1 [ELP(rh)] formulas). RESULTS: The mean ELP was calculated using the traditional (mean ELP(s) 5.59 mm +/- 0.52 mm [SD]; mean ELP(h) 5.63 +/- 0.42 mm) and K-independent (mean ELP(rs) 5.55 +/- 0.42 mm; mean ELP(rh) +/- SD 5.60 +/- 0.36 mm) methods. Agreement between ELP(s) and ELP(rs) and between ELP(h) and ELP(rh) were represented by Bland-Altman plots, with mean differences (+/- 1.96 SD) of 0.06 +/- 0.65 mm (range -0.59 to +0.71 mm; P=.08) in association with ELP(rs) and -0.04 +/- 0.39 mm (range -0.43 to +0.35 mm; P=.08) in association with ELP(rh). The mean absolute error for ELP(s) versus ELP(rs) estimation and for ELP(h) versus ELP(rh) estimation was 0.242 +/- 0.222 mm (range 0.001 to 1.272 mm) and 0.152 +/- 0.137 mm (range 0.001 to 0.814 mm), respectively. CONCLUSION: This study confirms that the K-independent ELP estimation method is comparable to traditional K-dependent methods and may be useful in post-refractive surgery patients.
    • Estimation of effective lens position using a method independent of preoperative keratometry readings.

      Dooley, Ian; Charalampidou, Sofia; Nolan, John; Loughman, James; Molloy, Laura; Beatty, Stephen; Department of Ophthalmology, Waterford Regional Hospital, Institute of Eye Surgery, Dublin, Ireland. iandooley@eustace.net (2011-03)
      To evaluate the validity of a keratometry (K)-independent method of estimating effective lens position (ELP) before phacoemulsification cataract surgery.
    • Surgically induced astigmatism after phacoemulsification with and without correction for posture-related ocular cyclotorsion: randomized controlled study.

      Dooley, Ian; Charalampidou, Sofia; Malik, Arhsed; Ormonde, Greta; Loughman, James; Molloy, Laura; Beatty, Stephen; Department of Ophthalmology, Waterford Regional Hospital, the Institute of Eye, Surgery, Whitfield Clinic, Suite 14, Whitfield Clinic, Cork Road, Waterford,, Ireland. iandooley@eustace.net (2012-02-01)
      PURPOSE: To report the impact of posture-related ocular cyclotorsion on one surgeon's surgically induced astigmatism (SIA) results and the variance in SIA. SETTING: Institute of Eye Surgery, Whitfield Clinic, Waterford, Ireland. METHODS: This prospective randomized controlled study included eyes that had phacoemulsification with intraocular lens implantation. Eyes were randomly assigned to have (intervention group) or not have (control group) correction for posture-related ocular cyclotorsion. In the intervention group, the clear corneal incision was placed precisely at the 120-degree meridian with instruments designed to correct posture-related ocular cyclotorsion. In the control group, the surgeon endeavored to place the incision at the 120-degree meridian, but without markings. RESULTS: The intervention group comprised 41 eyes and the control group, 61 eyes. The mean absolute SIA was 0.74 diopters (D) in the intervention group and 0.78 D in the control group; the difference between groups was not statistically significant (P>.5, unpaired 2-tailed Student t test). The variance in SIA was 0.29 D(2) and 0.31 D(2), respectively; the difference between groups was not statistically significant (P>.5, unpaired F test). CONCLUSIONS: Attempts to correct for posture-related ocular cyclotorsion did not influence SIA or its variance in a single-surgeon series. These results should be interpreted with full appreciation of the limitations of currently available techniques to correct for posture-related ocular cyclotorsion in the clinical setting.
    • Value of dual biometry in the detection and investigation of error in the preoperative prediction of refractive status following cataract surgery.

      Charalampidou, Sofia; Dooley, Ian; Molloy, Laura; Beatty, Stephen; Department of Ophthalmology, Waterford Regional Hospital, Waterford, Ireland., sonia.sofia1@gmail.com (2012-02-01)
      PURPOSE: To report the value of dual biometry in the detection of biometry errors. METHODS: Study 1: retrospective study of 224 consecutive cataract operations. The intraocular lens power calculation was based on immersion biometry. Study 2: immersion biometry was compared with optical coherence biometry (OCB) in terms of axial length, anterior chamber depth, keratometry readings and the recommended lens power to achieve emmetropia. Study 3: prospective study of 61 consecutive cataract operations. Both immersion and OCB were performed, but lens power calculation was based on the latter. RESULTS: Study 1: 115 (86%), 101 (75.4%), 90 (67.2%) and 50 (37.3%) of postoperative spherical equivalents were within +/-1.5 dioptres (D), +/-1.25 D, +/-1 D and +/-0.5 D of the target, respectively. Study 2: excellent agreement between axial length readings, anterior chamber depth readings and keratometry readings by immersion biometry and OCB was observed (reflected in a mean bias of -0.065 mm, -0.048 mm and +0.1803 D, respectively, in association with OCB). Agreement between the lens power recommended by each technique to achieve emmetropia was poor (mean bias of +1.16 D in association with OCB), but improved following appropriate modification of lens constants in the Accutome A-scan software (mean bias with OCB = -0.4 D). Study 3: 37 (92.5%) and 23 (57.5%) of operated eyes achieved a postoperative refraction within +/-1 D and +/-0.5 D of target, respectively. CONCLUSION: Systematic errors in biometry can exist, in the presence of acceptable postoperative refractive results. Dual biometry allows each biometric parameter to be scrutinized in isolation, and identify sources of error that may otherwise go undetected.