Phillip J. Buckhurst

A new optical low coherence reflectometry device for ocular biometry in cataract patients

Background: A new commercially available optical low coherence reflectometry device (Lenstar, Haag-Streit or Allegro Biograph, Wavelight) provides high-resolution non-contact measurements of ocular biometry. The study evaluates the validity and repeatability of these measurements compared with current clinical instrumentation. Method: Measurements were taken with the LenStar and IOLMaster on 112 patients aged 41–96 years listed for cataract surgery. A subgroup of 21 patients also had A-scan applanation ultrasonography (OcuScan) performed. Intersession repeatability of the LenStar measurements was assessed on 32 patients Results: LenStar measurements of white-to-white were similar to the IOLMaster (average difference 0.06 (SD 0.03) D; p = 0.305); corneal curvature measurements were similar to the IOLMaster (average difference −0.04 (0.20) D; p = 0.240); anterior chamber depth measurements were significantly longer than the IOLMaster (by 0.10 (0.40) mm) and ultrasound (by 0.32 (0.62) mm; p<0.001); crystalline lens thickness measurements were similar to ultrasound (difference 0.16 (0.83) mm, p = 0.382); axial length measurements were significantly longer than the IOLMaster (by 0.01 (0.02) mm) but shorter than ultrasound (by 0.14 (0.15) mm; p<0.001). The LensStar was unable to take measurements due to dense media opacities in a similar number of patients to the IOLMaster (9–10%). The LenStar biometric measurements were found to be highly repeatable (variability ⩽2% of average value). Conclusions: Although there were some statistical differences between ocular biometry measurements between the LenStar and current clinical instruments, they were not clinically significant. LenStar measurements were highly repeatable and the instrument easy to use.

Objective analysis of toric intraocular lens rotation and centration

PURPOSE: To assess the repeatability of an objective image‐analysis technique to determine intraocular lens (IOL) rotation and centration. SETTING: Six European ophthalmology clinics. METHODS: Eyes with an Akreos AO aspheric IOL with orientation marks were imaged. A masked observer rated image quality. The axis of rotation was determined from a line bisecting the IOL orientation marks. This was normalized for rotation of the eye between visits using the axis bisecting 2 consistent conjunctival vessels or iris features. The center of ovals overlaid to circumscribe the IOL optic edge and the pupil or limbus were compared to determine IOL centration. Intrasession repeatability was assessed in a subgroup of eyes and the variability of repeated analysis examined. RESULTS: The SD of intrasession repeatability was ±0.79 degrees for IOL rotational stability, ±0.10 mm for horizontal centration, and ±0.10 mm for vertical centration. The SD of repeated‐analysis variability of the same image was ±0.70 degrees, ±0.20 mm, and ±0.31 mm, respectively. The mean eye rotation (absolute) between visits was 2.23 degrees ± 1.84 (SD) (10% >5 degrees rotation) using 1 set of consistent conjunctival vessels or iris features and 2.03 ± 1.66 degrees (7%>5 degrees rotation) using the mean of 2 sets (P = .13). Poorer image quality resulted in larger apparent absolute IOL rotation (r = −0.45, P<.001). CONCLUSIONS: Objective analysis of digital retroillumination images allowed sensitive assessment of IOL rotation and centration stability. Eye rotation between images can lead to significant errors if not taken into account. Image quality is important to analysis accuracy. Financial Disclosure: Neither author has a financial or proprietary interest in any material or method mentioned.

Surgical correction of astigmatism during cataract surgery

High levels of corneal astigmatism are prevalent in a significant proportion of the population. During cataract surgery pre‐existing astigmatism can be corrected using single or paired incisions on the steep axis of the cornea, using relaxing incisions or with the use of a toric intraocular lens. This review provides an overview of the conventional methods of astigmatic correction during cataract surgery and in particular, discusses the various types of toric lenses presently available and the techniques used in determining the correct axis for the placement of such lenses. Furthermore, the potential causes of rotation in toric lenses are identified, along with techniques for assessing and quantifying the amount of rotation and subsequent management options for addressing post‐operative rotation.

Rotational and centration stability of an aspheric intraocular lens with a simulated toric design.

PURPOSE: To assess the stability of the Akreos AO intraocular lens (IOL) platform with a simulated toric design using objective image analysis. SETTING: Six hospital eye clinics across Europe. METHODS: After implantation in 1 eye of patients, IOLs with orientation marks were imaged at 1 to 2 days, 7 to 14 days, 30 to 60 days, and 120 to 180 days. The axis of rotation and IOL centration were objectively assessed using validated image analysis. RESULTS: The study enrolled 107 patients with a mean age of 69.9 years ± 7.7 (SD). The image quality was sufficient for IOL rotation analysis in 91% of eyes. The mean rotation between the first day postoperatively and 120 to 180 days was 1.93 ± 2.33 degrees, with 96% of IOLs rotating fewer than 5 degrees and 99% rotating fewer than 10 degrees. There was no significant rotation between visits and no clear bias in the direction of rotation. In 71% of eyes, the dilation and image quality was sufficient for image analysis of centration. The mean change in centration between 1 day and 120 to 180 days was 0.21 ± 0.11 mm, with all IOLs decentering less than 0.5 mm. There was no significant decentration between visits and no clear bias in the direction of the decentration. CONCLUSION: Objective analysis of digital retroillumination images taken at different postoperative periods shows the aspheric IOL platform was stable in the eye and is therefore suitable for the application of a toric surface to correct corneal astigmatism. Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned.

Development of a questionnaire to assess the relative subjective benefits of presbyopia correction

PURPOSE: To develop a standardized questionnaire of near visual function and satisfaction to complement visual function evaluations of presbyopic corrections. SETTING: Eye Clinic, School of Life and Health Sciences, Aston University, Midland Eye Institute and Solihull Hospital, Birmingham, United Kingdom. DESIGN: Questionnaire development. METHODS: A preliminary 26‐item questionnaire of previously used near visual function items was completed by patients with monofocal intraocular lenses (IOLs), multifocal IOLs, accommodating IOLs, multifocal contact lenses, or varifocal spectacles. Rasch analysis was used for item reduction, after which internal and test–retest reliabilities were determined. Construct validity was determined by correlating the resulting Near Activity Visual Questionnaire (NAVQ) scores with near visual acuity and critical print size (CPS), which was measured using the Minnesota Low Vision Reading Test chart. Discrimination ability was assessed through receiver‐operating characteristic (ROC) curve analysis. RESULTS: One hundred fifty patients completed the questionnaire. Item reduction resulted in a 10‐item NAVQ with excellent separation (2.92), internal consistency (Cronbach α = 0.95), and test–retest reliability (intraclass correlation coefficient = 0.72). Correlations of questionnaire scores with near visual acuity (r = 0.32) and CPS (r = 0.27) provided evidence of validity, and discrimination ability was excellent (area under ROC curve = 0.91). CONCLUSION: Results show the NAVQ is a reliable, valid instrument that can be incorporated into the evaluation of presbyopic corrections. Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned.

Exploring the optimum step size for defocus curves

Purpose To evaluate the effect of reducing the number of visual acuity measurements made in a defocus curve on the quality of data quantified. Setting Midland Eye, Solihull, United Kingdom. Design Evaluation of a technique. Methods Defocus curves were constructed by measuring visual acuity on a distance logMAR letter chart, randomizing the test letters between lens presentations. The lens powers evaluated ranged between +1.50 diopters (D) and −5.00 D in 0.50 D steps, which were also presented in a randomized order. Defocus curves were measured binocularly with the Tecnis diffractive, Rezoom refractive, Lentis rotationally asymmetric segmented (+3.00 D addition [add]), and Finevision trifocal multifocal intraocular lenses (IOLs) implanted bilaterally, and also for the diffractive IOL and refractive or rotationally asymmetric segmented (+3.00 D and +1.50 D adds) multifocal IOLs implanted contralaterally. Relative and absolute range of clear‐focus metrics and area metrics were calculated for curves fitted using 0.50 D, 1.00 D, and 1.50 D steps and a near add‐specific profile (ie, distance, half the near add, and the full near‐add powers). Results A significant difference in simulated results was found in at least 1 of the relative or absolute range of clear‐focus or area metrics for each of the multifocal designs examined when the defocus‐curve step size was increased (P<.05). Conclusion Faster methods of capturing defocus curves from multifocal IOL designs appear to distort the metric results and are therefore not valid. Financial Disclosure No author has a financial or proprietary interest in any material or method mentioned.

Evaluation of an open-field autorefractor's ability to measure refraction and hence potential to assess objective accommodation in pseudophakes

Background To evaluate the accuracy of an open-field autorefractor compared with subjective refraction in pseudophakes and hence its ability to assess objective eye focus with intraocular lenses (IOLs). Methods Objective refraction was measured at 6 m using the Shin-Nippon NVision-K 5001/Grand Seiko WR-5100K open-field autorefractor (five repeats) and by subjective refraction on 141 eyes implanted with a spherical (Softec1 n=53), aspherical (SoftecHD n=37) or accommodating (1CU n=22; Tetraflex n=29) IOL. Autorefraction was repeated 2 months later. Results The autorefractor prescription was similar (average difference: 0.09±0.53 D; p=0.19) to that found by subjective refraction, with ∼71% within ±0.50 D. The horizontal cylindrical components were similar (difference: 0.00±0.39 D; p=0.96), although the oblique (J45) autorefractor cylindrical vector was slightly more negative (by −0.06±0.25 D; p=0.06) than the subjective refraction. The results were similar for each of the IOL designs except for the spherical IOL, where the mean spherical equivalent difference between autorefraction and subjective was more hypermetropic than the Tetraflex accommodating IOL (F=2.77, p=0.04). The intrasession repeatability was <0.55 D (95% CI) and intersession repeatability <0.50 D in ≥85%. Conclusions The autorefractor gives valid and repeatable measures of pseudophakic eye refraction and hence objective accommodation.

Safety and effectiveness of a new toric presbyopia-correcting posterior chamber silicone intraocular lens.

Purpose To evaluate the safety and effectiveness of the Trulign toric intraocular lens (IOL) in adults with cataract. Setting Eight private practices in the United States and 1 in Canada. Design Prospective randomized single‐masked multicenter study. Methods A toric IOL (1.25 D, 2.00 D, or 2.75 D, determined by a toric calculator) was implanted in eligible patients with age‐related cataract requiring a 16.00 to 27.00 diopter (D) spherical IOL power and with a predicted postoperative astigmatism of 0.83 to 2.50 D. Eyes within the lowest cylinder range (predicted postoperative astigmatism 0.83 to 1.32 D) were randomized in a 1:1 ratio between the 1.25 D toric IOL group and the nontoric accommodating IOL (Crystalens) control group. Results The toric 1.25 D group had a statistically significantly greater percentage reduction in absolute cylinder (P < .001) and uncorrected distance visual acuity (P = .002) than the control group at the 120‐ to 180‐day visit. The mean monocular uncorrected vision at distance, intermediate, and near was 20/25, 20/22, and 20/39, respectively, with the 1.25 D, 2.00 D, and 2.75 D toric IOLs in aggregate (toric group). In addition, 96.1% of patients (123/128) had 5.0 degrees or less absolute IOL rotation postoperatively. Regarding safety, the endpoints for preservation of corrected visual acuity and the incidence of complications and adverse events were met. Conclusion The toric IOL was safe and effective in reducing the effects of preoperative corneal astigmatism and provided excellent uncorrected distance and intermediate vision and functional near vision. Financial Disclosures Dr. Pepose is a consultant to Bausch & Lomb and was medical monitor of this study. Drs. Buckhurst, Whitman, Feinerman, Hovanesian, Davies, Labor, and Carter are consultants to Bausch & Lomb. At the time of the study, Drs. Hayashida, and Khodai were employees of Bausch & Lomb. Drs. Colvard and Mittleman have financial or proprietary interest in any material or method mentioned.

Tablet App halometer for the assessment of dysphotopsia.

Purpose To assess the validity and repeatability of the Aston Halometer. Setting University clinic, United Kingdom. Design Prospective, repeated‐measures experimental study. Methods The halometer comprises a bright light‐emitting‐diode (LED) glare source in the center of an iPad4. Letters subtending 0.21° (˜0.3 logMAR) were moved centrifugally from the LED in 0.05 degree steps in 8 orientations separated by 45 degrees for each of 4 contrast levels (1000, 500, 100, and 25 Weber contrast units [Cw]) in random order. Bangerter occlusion foils were inserted in front of the right eye to simulate monocular glare conditions in 20 subjects (mean age 27.7 ± 3.1 years). Subjects were positioned 2 meters from the screen in a dark room with the iPad controlled from an iPhone via Bluetooth operated by the researcher. The C‐Quant straylight meter was also used with each of the foils to measure the level of straylight over the retina. Halometry and straylight repeatability was assessed at a second visit. Results Halo size increased with the different occlusion foils and target contrasts (F = 29.564, P < .001) as expected and in a pattern similar to straylight measures (F = 80.655, P < 0.001). Lower contrast letters showed better sensitivity but larger glare‐obscured areas, resulting in ceiling effects caused by the screen’s field‐of‐view, with 500 Cw being the best compromise. Intraobserver and interobserver repeatability of the Aston Halometer was good (500Cw: 0.84 to 0.93 and 0.53 to 0.73) and similar to the straylight meter. Conclusion The halometer provides a sensitive, repeatable way of quantifying a patient‐recognized form of disability glare in multiple orientations to add objectivity to subjectively reported discomfort glare.

Comparison of reliability and repeatability of corneal curvature assessment with six keratometers

Keratometric methodology varies between instruments and the differences may have a clinical impact. We investigated the agreement and reproducibility of six keratometers.