Emma J. Berrow

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.

Validity and repeatability of the Aladdin ocular biometer

Aim To assess the accuracy and reproducibility of biometry undertaken with the Aladdin (Topcon, Tokyo, Japan) in comparison with the current gold standard device, the IOLMaster 500 (Zeiss, Jena, Germany). Setting University Eye Clinic, Birmingham, UK and Refractive Surgery Centre, Kiel, Germany. Methods The right eye of 75 patients with cataracts and 22 healthy participants were assessed using the two devices. Measurements of axial length (AL), anterior chamber depth (ACD) and keratometry (K) were undertaken with the Aladdin and IOLMaster 500 in random order by an experienced practitioner. A second practitioner then obtained measurements for each participant using the Aladdin biometer in order to assess interobserver variability. Results No statistically significant differences (p>0.05) between the two biometers were found for average difference (AL)±95% CI=0.01±0.06 mm), ACD (0.00±0.11 mm) or mean K values (0.08±0.51 D). Furthermore, interobserver variability was very good for each parameter (weighted κ≥0.85). One patients IOL powers could not be calculated with either biometer measurements, whereas a further three could not be analysed by the IOLMaster 500. The IOL power calculated from the valid measurements was not statistically significantly different between the biometers (p=0.842), with 91% of predictions within±0.25 D. Conclusions The Aladdin is a quick, easy-to-use biometer that produces valid and reproducible results that are comparable with those obtained with the IOLMaster 500.

The effects of a lutein-based supplement on objective and subjective measures of retinal and visual function in eyes with age-related maculopathy – a randomised controlled trial

Lutein and zeaxanthin are lipid-soluble antioxidants found within the macula region of the retina. Links have been suggested between increased levels of these carotenoids and reduced risk for age-related macular disease (ARMD). Therefore, the effect of lutein-based supplementation on retinal and visual function in people with early stages of ARMD (age-related maculopathy, ARM) was assessed using multifocal electroretinography (mfERG), contrast sensitivity and distance visual acuity. A total of fourteen participants were randomly allocated to either receive a lutein-based oral supplement (treated group) or no supplement (non-treated group). There were eight participants aged between 56 and 81 years (65·50 (SD 9·27) years) in the treated group and six participants aged between 61 and 83 years (69·67 (SD 7·52) years) in the non-treated group. Sample sizes provided 80% power at the 5% significance level. Participants attended for three visits (0, 20 and 40 weeks). At 60 weeks, the treated group attended a fourth visit following 20 weeks of supplement withdrawal. No changes were seen between the treated and non-treated groups during supplementation. Although not clinically significant, mfERG ring 3 N2 latency (P=0·041) and ring 4 P1 latency (P=0·016) increased, and a trend for reduction of mfERG amplitudes was observed in rings 1, 3 and 4 on supplement withdrawal. The statistically significant increase in mfERG latencies and the trend for reduced mfERG amplitudes on withdrawal are encouraging and may suggest a potentially beneficial effect of lutein-based supplementation in ARM-affected eyes.

Visual performance of a new bi-aspheric, segmented, asymmetric multifocal IOL.

PURPOSE To assess the visual performance and subjective experience of eyes implanted with a new bi-aspheric, segmented, multifocal intraocular lens: the Mplus X (Topcon Europe Medical, Capelle aan den IJssel, Netherlands). METHODS Seventeen patients (mean age: 64.0 + 12.8 years) had binocular implantation (34 eyes) with the Mplus X. Three months after the implantation, assessment was made of: manifest refraction; uncorrected and corrected distance visual acuity; uncorrected and distance corrected near visual acuity; defocus curves in photopic conditions; contrast sensitivity; halometry as an objective measure of glare; and patient satisfaction with unaided near vision using the Near Acuity Visual Questionnaire. RESULTS Mean residual manifest refraction was -0.13 + 0.51 diopters (D). Twenty-five eyes (74%) were within a mean spherical equivalent of -0.50 D. Mean uncorrected distance visual acuity was +0.10 + 0.12 logMAR monocularly and 0.02 - 0.09 IogMAR binocularly. Thirty-two eyes (94%) could read 0.3 or better without any reading correction and all patients could read 0.3 or better with a reading correction. Mean monocular uncorrected near visual acuity was 0.18 + 0.16 logMAR, improving to 0.15 + 0.15 logMAR with distance correction. Mean binocular uncorrected near visual acuity was 0.11 - 0.11 logMAR, improving to 0.09 - 0.12 logMAR with distance correction. Mean binocular contrast sensitivity was 1.75 _ 0.14 log units at 3 cycles per degree, 1.88 _ 0.20 log units at 6 cycles per degree, 1.66 + 0.19 log units at 12 cycles per degree, and 1.11 - 0.20 log units at 18 cycles per degree. Mean binocular and monocular halometry showed a glare profile of less than 10 of debilitating light scatter. Mean Near Acuity Visual Questionnaire Rasch score (0 = no difficulty, 100 = extreme difficulty) for satisfaction for near vision was 20.43 - 14.64 log-odd units. CONCLUSIONS The Mplus X provides a good visual outcome at distance and near with minimal dysphotopsia. Patients were very satisfied with their uncorrected near vision.

The electroretinogram: a useful tool for evaluating age-related macular disease?

With an ageing population, the number of age-related macular disease (ARMD) cases will inevitably rise. This gives greater impetus for the need to identify the disease earlier and assess treatments to slow disease progression. Differing electroretinogram (ERG) modalities have been reviewed in relation to the objective assessment of retinal function in ARMD and for monitoring the effectiveness of clinical interventions. Conflicting results have been found with regard to the efficacy of ERG findings in the investigation of ARMD in previous years. The newer multifocal ERG paradigm provides spatial topographical information about retinal function in ARMD. It has shown promising results in monitoring effectiveness of clinical interventions and studies are continuing in this area. Better knowledge of retinal function in ARMD may lead to enhanced treatments at each phase of the disease.

Risk Factors for Age-related Macular Degeneration

Although the pathogenesis of age-related macular disease (ARMD) is still not fully understood, genetic and environmental factors are implicated. Epidemiological studies have found conflicting findings between ARMD development and many potential risk factors. This review provides an up-to-date account of modifiable and non-modifiable risk factors associated with ARMD development, with potential mechanisms between risk factors and ARMD development described. Age, smoking and genetic factors appear to be consistently associated with an increased risk of developing ARMD. However, ageing and genetic disposition cannot be currently modified, leading to increased interest as to how other modifiable factors may reduce the risk of ARMD.