An introduction to nutrition for an optometrist

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Experimental Assessment of the Spatial and Temporal Distribution of Non-Contact Tonometer Airflows

(1) The aim of the study was to investigate the spatial and temporal characteristics of the airflow created by two commercially available non-contact tonometers: the CorvisST and the Ocular Response Analyser (ORA). (2) The airflow pressure was measured using a microelectromechanical system (MEMS) pressure sensor to investigate the spatial and temporal distribution. The airflow from the CorvisST and Ocular Response Analyser were mapped to a 600 µm and a 1 mm resolution grid, respectively. (3) Central airflow pressure of the CorvisST (96.4 ± 1.4 mmHg) was higher than that of the Ocular Response Analyser (91.7 ± 0.7 mmHg). The duration of the air-puffs also differed, with the CorvisST showing a shorter duration (21.483 ± 0.2881 ms) than that of the ORA (23.061 ± 0.1872 ms). The rising edge of the CorvisST airflow pressure profile demonstrated a lower gradient (+8.94 mmHg/ms) compared to that of the Ocular Response Analyser (+11.00 mmHg/ms). Both had similar decay response edges: CorvisST −11.18 mmHg/ms, Ocular Response Analyser −11.65 mmHg/ms. (4) The study presents a valid method to investigate the physical dimensions of the airflow pressure of non-contact tonometers. Novel findings relating to the magnitude, duration and spatial characteristics of the respective airflow pressures are reported. It is anticipated that this information will better inform clinical studies and theoretical models relating to ocular biomechanics.</jats:p

Conformation of the anterior segment in human myopia.

PURPOSE: Topography of the in vivo anterior segment is of relevance in understanding its role in myopia and in the development of ocular surgical procedures. Using 3D magnetic resonance (MR) images of the human eye, regional variations in surface area (SA) and bulbosity of four anterior segment regions were investigated in association with refractive status (Rx), axial length (AL) and total ocular volume (OV). METHODS: T2-weighted ocular MR images from 43 adults aged 18-40 years (mean ± SD; 28.65 ± 6.20) comprising 20 non-myopes (≥-0.50) 0.57 ± 1.38 and 23 myopes (<-0.50) -6.37 ± 4.23 MSE (D) were collected. 2D representations of each quadrant (superior-temporal [ST], superior-nasal [SN], inferior-temporal [IT] and inferior-nasal [IN]) of the anterior section (3.5-9 mm) were fitted with second-order polynomials. Polynomials were integrated and rotated about the x-axis to generate SA; dividing the SA by 4 provided relative quadrantial SA. The x2 coefficient provides indices of bulbosity. OV was derived from the 3D MRI scans. Rx and AL were measured using cycloplegic autorefraction and the Zeiss IOLMaster, respectively. One- and two-way repeated-measures ANCOVAs tested differences in SA and bulbosity for Rx, gender, ethnicity and age. Pearson's correlation coefficient tested the relationship between MRI-derived metrics and biometry. RESULTS: Significant differences in SA were observed between quadrants (p < 0.001) with differences between ST versus IN, IN versus IT and SN versus IT. An interaction effect (p = 0.01) for Rx suggested smaller temporal (ST and IT) and larger nasal (SN and IN) SA in myopes. AL and myopic Rx were negative correlated (p < 0.05) with SA at IN, SN and IT. OV was significantly associated with SA at ST. Bulbosity showed no regional differences nor an effect of AL or Rx. CONCLUSION: Significant regional variation in SA exists across the anterior segment that is modulated by Rx and AL. It is unclear whether these structural characteristics are a precursor or consequence of myopia and may warrant investigation when developing biomechanical interventions

Visual Function and Subjective Perception of Vision following bilateral implantation of monofocal and multifocal intraocular lenses: A Randomised Controlled Trial

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Optimising curve fitting techniques to look for standardisation of the analysis of defocus curves derived from multifocal intraocular lenses.

INTRODUCTION: To establish the most appropriate curve fitting method to allow accurate comparison of defocus curves derived from intraocular lenses (IOLs). METHODS: Defocus curves were plotted in five IOL groups (monofocal, extended depth of focus, refractive bifocal, diffractive bifocal and trifocal). Polynomial curves from 2nd to 11th order and cubic splines were fitted. Goodness of fit (GOF) was assessed using five methods: least squares, coefficient of determination (R2 adj ), Akaike information criteria (AIC), visual inspection and Snedecor and Cochran. Additional defocus steps at -2.25 D and -2.75 D were measured and compared to the calculated visual acuity (VA) values. Area under the defocus curve and range of focus were also compared. RESULTS: Goodness of fit demonstrated variable results, with more lenient methods such as R2 adj leading to overfitting and conservative methods such as AIC resulting in underfitting. Furthermore, conservative methods diminished the inflection points resulting in an underestimation of VA. Polynomial of at least 8th order was required for comparison of area methods, but overfitted the EDoF and monofocal groups; the spline curve was consistent for all IOLs and methods. CONCLUSIONS: This study demonstrates the inherent difficulty of selecting a single polynomial function. The R2 method can be used cautiously along with visual inspection to guard against overfitting. Spline curves are suitable for all IOLs, guarding against the issues of overfitting. Therefore, for analysis of the defocus profile of IOLs, the fitting of a spline curves is advocated and should be used wherever possible

One-year post-operative comparison of visual function and patient satisfaction with trifocal and extended depth of focus intraocular lenses.

PURPOSE: To evaluate visual performance with trifocal and extended depth of focus IOL at 1 year post-operatively. SETTING: BMI Southend Hospital. DESIGN: Cohort study. METHODS: An age-matched cohort of forty subjects bilaterally implanted with the AT LISA 839MP trifocal IOL (20 patients, 40 eyes) and the Tecnis Symfony extended depth of focus IOL (20 patients, 40 eyes) were assessed at 3-6 months and 12-18 months post-operatively. Primary outcome measures were distance (6 m), intermediate (70 cm), near visual acuity (40 cm), and analysis of defocus profiles. Secondary outcomes included contrast sensitivity, Radner reading performance, quality of vision and assessment of halos. RESULTS: Distance visual acuity (VA) and defocus areas were similar (p = 0.07). No significant difference in intermediate VA was noted but the intermediate area of focus was greater in the EDoF (0.31 ± 0.12 LogMAR*m-1) compared to the trifocal (0.22 ± 0.08LogMAR*m-1) (p = 0.02). However, all near metrics were significantly better in the trifocal group. 80% of trifocal subjects were spectacle independent compared to 50% EDoF subjects. Quality of vision questionnaire found no significant differences between groups, however halo scores were greater at 3-6 months in the trifocal group (p < 0.01) but no differences were noted at 12-18 months. CONCLUSIONS: Near vision is significantly better for the trifocal, thus greater levels of spectacle independence. The range of intermediate vision was greater for the EDoF but no difference in intermediate VA. In the early period, differences in contrast sensitivity and halo size/intensity were noted, however, by one-year these measures were not significantly different

Evaluation of clinical outcomes following implantation of a sub-2-mm hydrophilic acrylic MICS intraocular lens

PURPOSE: To evaluate clinical outcomes following sub-2-mm microincision cataract surgery (MICS) and intraocular lens (IOL) implantation. SETTING: Five EU clinical sites. DESIGN: Prospective, multicenter, open-label, single-arm, non-randomized. METHODS: Preoperative assessment involved visual acuity (VA), intraocular pressure and biometry measurements. 1.4-mm wound-assisted or 1.8-mm MICS was performed. Follow-up visits were made 1 day, 1-2 weeks, 1-2 and 4-6 months after surgery. The incision size, corrected distance VA (CDVA), uncorrected distance VA, manifest refraction spherical equivalent (MRSE), refraction predictability/stability and IOL decentration were assessed. At 12-, 18-, and 24-month, long-term centration, posterior capsular opacification (PCO) and Nd:YAG capsulotomy rates were investigated. RESULTS: A total of 103 eyes were implanted with the study IOL (INCISE, Bausch &amp; Lomb), 96 of which were included in visual outcome analysis. A mean 6-month CDVA of - 0.02 logMAR (20/20 + 1) was observed and 75 eyes (79.8%) and 93 eyes (98.3%) achieved a visual acuity of at least 20/20 or 20/40. Mean MRSE was - 0.20 ± 0.60 D. Mean absolute predictive error was 0.44 ± 0.36 D, with 90.4% within 1.00 D of target. Mean total decentration was 0.35 ± 0.36 mm at 6 months and 0.32 ± 0.14 mm at 24 months (p &gt; 0.05). 24-month evaluation of posterior capsular opacification score was 0.03 for the central area. A Nd:YAG rate of 3.4% was observed at 24 months. CONCLUSIONS: The new MICS IOL provided excellent visual outcomes and was safe and effective for the sub-2-mm procedure. The MICS IOL demonstrated long-term centration, stability and a low rate of PCO development