Comparison of current paediatric contrast sensitivity assessments using simulated reduced contrast thresholds

PURPOSE

There are limited tests of contrast sensitivity (CS) for use in children. The Hiding Heidi (HH) is suitable for all cognitive abilities, but has a ceiling effect. The Double Happy (DH) test has comparable thresholds to the Pelli Robson (PR), however the ability to detect changes in contrast has not been established. This study aims to compare contrast thresholds and agreement between HH and the DH, comparing to the PR chart in normal conditions and under reduced visual and lighting conditions.

METHODS

Tests were repeated under different conditions to reduce the contrast. Room illumination was 20,900{plus minus}2% lux in bright conditions and 2,000{plus minus}2% lux in dim conditions, both conditions were repeated with the addition of simulation spectacles to reduce the clarity of vision. Participants' CS was measured uniocularly using the PR, HH and DH tests.

RESULTS

50 participants, age 18-62 years (mean{plus minus}standard deviation: 24.5{plus minus}7.98), were assessed. On HH 94% (n = 47) reached the maximum score, with the DH it was 18% (n = 9). The difference in reduction between conditions was smaller with HH in comparison to PR and DH, but significantly different from baseline conditions. Under dim conditions the reduction in PR and DH was -0.21 logCS units, but only -0.04 logCS for HH.

CONCLUSION

The DH test has better agreement with PR than HH and is better at detecting CS changes, highlighting the advantages of use in clinical practice.

Using a Computerised Staircase and Incremental Optotype Sizes to Improve Visual Acuity Assessment Accuracy

Background:

Given the impact of visual acuity results on diagnosis and management, it is essential that the test is accurate, determined by factors such as test-retest variability. Standardisation improves accuracy, which can be performed via a computerised staircase methodology. Standard clinical tests with scoring of 0.02 per optotype implies an incremental score per optotype despite optotype size remaining constant on each line. The aim of this study is to establish if near continuous incremental optotype display and scoring improves test-retest variability compared to current testing methods.

Methods:

A computerised three up, one down adaptive staircase was used to display Kay Picture optotypes on an LCD monitor. Three methods of visual acuity assessment were undertaken: ETDRS, Kay Pictures and computerised Kay Pictures. Tests were performed twice under standard clinical conditions.

Results:

One hundred nineteen adults were tested. Test-retest variability for computerised Kay pictures was 0.01 logMAR (±0.04, p = 0.001). Good levels of agreement were observed for computerised Kay pictures in terms of test-retest variability, where the test had the smallest mean bias (0.01 logMAR compared to 0.03 and 0.08 logMAR for Kay Pictures and ETDRS respectively) and narrowest limits of agreement. Participants performed better in computerised Kay pictures than Kay Pictures by 0.03 logMAR, and better in ETDRS than computerised Kay pictures by 0.1 logMAR.

Conclusion:

Computerised Kay pictures exhibited a low test-retest variability, demonstrating it is reliable and repeatable. This repeatability measure is lower than the test-retest variability of the ETDRS and Kay Pictures tests.

Evaluation of a New Method to Track Changes in Vision at Home for Children Undergoing Amblyopia Treatment

PURPOSE

A new amblyopia tracker app has been designed to provide parents with a method of monitoring a child's vision by presenting a single optotype size that the tester moves to identify the furthest distance the optotypes can be seen. The aim of this study is to evaluate this methodology in adults, comparing the findings to visual acuity (VA) measured with the iSight app and to determine the test retest variability.

METHODS

Adults, aged 18-39 years, with no known eye condition and VA ≤ 0.7 logMAR were recruited. Bangerter filters were used to simulate amblyopia, where VA was reduced below 0.0 with an interocular difference of at least 0.2 logMAR. Testing for both apps was performed monocularly, with the test order being randomised.

RESULTS

Data from 32 subjects were analysed. For the test retest variability analysis, paired t-tests showed no statistically significant difference between the tests for either eye, either app or the interocular acuity difference (p > 0.3 in all cases). Bland Altman plots showed similar limits of agreement between the two apps. When comparing measurements between the apps there was no statistically significant difference on the first or second test, either eye or the interocular acuity difference (p > 0.5 in all cases).

CONCLUSION

The results support the theory that changing distance is a valid method of assessing VA as the measurements agree well with the standard approach of reducing optotype size. Test retest variability is similar between the two apps and there is good agreement between the measurements.

Normative data for the redesigned Kay Pictures visual acuity test

The Kay Picture Test of visual acuity is used extensively in the diagnosis and management of children. The test has been redesigned and validated to meet the international visual acuity chart guidelines, necessitating the collection of new normative data. The data presented here demonstrates that the visual acuities of children <60 months of age with no visual deficiency improve with age and show no significant intraocular difference. This is the first report of normative data in young children for the redesigned Kay Pictures Test (singles format).

Malignant melanoma arising in a radiotherapy field: report of two cases and review of the literature

We report 2 patients who developed melanoma or melanoma metastases in radiation fields 6 and 43 years after radiation therapy, respectively. One of the patients had received adjuvant hyperfractionated photon therapy for Ewing sarcoma, while the other patient had received X-ray therapy for a hemangioma. While postradiation secondary cancers with a long latency period are not uncommon, the development of melanoma is exceedingly rare.

Magnetic bead RT-PCR: establishment of a new method for detecting circulating melanoma cells

This study was performed to detect circulating melanoma cells in peripheral blood using a novel method based on magnetic-activated cell separation (MACS) followed by a nested reverse transcriptase-polymerase chain reaction (RT-PCR) for tyrosinase and MART-1 mRNA. Samples to be tested were enriched for tumour cells either by isolating melanoma cells using two anti-melanoma antibodies (MART-1 and HMB-45) or by CD45 depletion of the non-melanoma cell fraction. The tumour cell-enriched fractions were subjected to mRNA isolation using oligo-deoxythymidylate (oligo-dT) magnetic beads followed by a nested RT-PCR. Sensitivity was assessed by spiking experiments and compared with a commonly used total RNA isolation system previously established in our department. Positive isolation of melanoma cells showed insufficient sensitivity, whereas negative isolation by depletion of leukocytes showed a detection limit of at least one melanoma cell per millilitre of whole blood. In further experiments, the depletion assay was applied to 25 peripheral blood samples of melanoma patients. The preliminary data obtained from the new method indicate a comparable detection rate to the established total RNA extraction method. However, not all the results were concordant. Therefore, future experiments need to be performed with a statistically greater number of patients.