Finalists – Tulsi Patel
Project – The effect of centre distance contact lenses on adult visual function in young adults
Supervisor – Dr Alison Alderson and Dr Graham Mouat
As this very publication bears witness, there is much interest at present in the possibility of minimising myopic progression through various means. As this student project pointed out, one in five teenagers in the UK are myopic and the trend is increasing. High levels of myopia (greater than .00DS) significantly increases the risk of sight-threatening conditions, such as glaucoma, cataract and retinal detachment.
One method that is being tried is the use of centre distance multifocal contact lenses on young adults. The theory is that the lenses maintain a sustained peripheral myopic blur so reduce the stimulus for axial length growth. At present, no lenses are currently licensed in the UK for myopia control and so the use of multifocals is something of a compromise. The aim of this project was to look at the impact of such lenses on visual function.
Four types of contact lens were compared;
- CooperVision Biofinity single vision
- CooperVision Biofinity multifocal (add +2.00)
- J&J Acuvue Oasys for presbyopia (add +2.50)
- CooperVision Proclear multifocal (add +2.00)
The differences in the additions were noted by the judges as introducing an initial difference through a variation in power. Participants to assess with the lenses had to meet the following selection criteria:
- Acuity of 6/6 or more with an up-to-date correction in both eyes and with no anomaly of binocular vision
- Less than 1.00DC
- No ocular pathology
- Aged between 18 and 25 years inclusive
- Pupil size of larger than 5mm in low illumination
Overall, 12 participants were recruited and seven gave full data sets.
With the lenses in situ, the following tests were undertaken:
- Humphreys SITA fast 30-2 visual fields in the dominant eye
- High contrast (100%) visual acuity measured at high and low illuminations at 6m
- Low contrast (10%) visual acuity measured at high and low illumination at 6m and 3m
- Stereopsis measured using TNO at 40cm
- Centration and post-blink movement
Results
The Acuvue lenses appeared to impact most upon the distance high contrast acuity (figure 1) but had a higher addition.
Figure 1: Impact of lenses upon distance logMAR score
None of the lenses had any significant impact upon stereopsis (figure 2).
There was no significant effect of pupil size in the single vision lens and the Proclear lens (p=0.110) at low illumination (figure 3).
Figure 3: Pupil size impact on single vision and Proclear lenses
Pupil size had a significant impact on the acuity for both the Biofinity and Acuvue lenses (figure 4).
Figure 4: Pupil size impact on two multifocal lenses
Conclusions
This small study suggested that pupil size is an influence on the performance of the Acuvue Oasys lens.
All the lenses ‘gave reasonable acuity at high contrast’. The judges, however, were most impressed by the summary of the limitations of the study. These were highlighted as small sample size, lack of a 1m chart testing, no appropriate reading chart and lack of any follow up assessments.
It was also felt that the acuity assessments failed to take into account that the Acuvue lens had a higher addition so likely to suffer the reduction in acuity compared with a lower addition as in this study.
Finally, the pretext of the study was to consider myopia progression influence with these lenses, but this was something for future research.
A nicely presented study but one which well recognised its shortcomings.