Sheila Rae

The effect of altering spherical aberration on the static accommodative response

Purpose:  To investigate the effect of altering the spherical aberration (SA) of the eye on the static accommodative response.

Peripheral refractive changes associated with myopia progression

PURPOSE To evaluate the changes in peripheral refraction profiles associated with myopia progression and treatment modalities used in the Cambridge Anti-Myopia Study. METHODS one hundred and seventy-seven myopes in the age range of 14 to 22 years were enrolled in the study. The mean spherical equivalent refractive error was 3.12 1.87 diopters (D) and the refractive error of each participant was corrected with contact lenses. The participants were randomly assigned to one of four treatment groups, which included: altered spherical aberration and vision training, altered spherical aberration only, vision training only, and control. Peripheral refractive error was measured using an open field autorefractor in the central 60° of the retina in 10° steps. The refractive error was measured using cycloplegic autorefraction. Two-year refractive progression data and initial peripheral refraction measurements were available in 113 participants. Measurements of peripheral refraction and cycloplegic refraction were obtained at three visits over 2 years in 12-month intervals for 92 participants. RESULTS All subjects showed a relative peripheral hyperopia, especially in the nasal retina. A limited magnitude of myopia progression of -0.34 ± 0.36 D over 2 years was found in each of the four groups on average. There were no significant differences in the rate of progression between any of the treatment groups (P > 0.05). Initial peripheral J45 astigmatic refractive error at 20° and 30° in the nasal retina was weakly correlated with progression of myopia over 2 years (r = -0.27, P = 0.004 and r = -0.20, P = 0.040, respectively; n = 113). The change in spherical equivalent peripheral refractive error at 30° nasal retina over time was also significantly correlated with progression of myopia especially at 24 months (r = -0.24, P = 0.017, n = 92). CONCLUSIONS Relative peripheral hyperopia is associated with myopia. Myopia progression may be weakly linked to changes in the peripheral refraction profiles in the nasal retina. However, a causative link between peripheral refractive error and myopia progression could not be established.

Aberration Control and Vision Training as an Effective Means of Improving Accommodation in Individuals with Myopia

PURPOSE To test the efficacy of a novel dual treatment for improving accommodative accuracy and dynamics in young persons with myopia. METHODS Ninety-three young persons with myopia (mean spherical equivalent, -3.0 +/- 1.8 D; age 16.8 +/- 2.1 years; spherical aberration +0.06 +/- 0.04 microm) participated in the study. Custom-designed soft contact lenses were used to alter ocular SA to -0.10 microm to improve accommodative accuracy and reduce any lag of accommodation. A vision training regimen was performed for 18 minutes per day for up to 6 weeks to improve speed of dynamic accommodation. Control groups had contact lenses with no added SA and/or no exercises. To avoid any effects of natural levels of negative aberration on the results of the study, all participants who had negative SA were excluded. RESULTS The treatment contact lenses produced a significant reduction in lag of accommodation (P < 0.05) at all proximal viewing distances measured. The vision training measurement and treatment resulted in a significant increase in distance facility rate for all groups compared with their own baselines (P < 0.05). Near facility rate improved in the vision training treatment group only compared with its baseline (P < 0.05). Both positive and negative response times for distant viewing were significantly shorter in all groups after training compared with their baseline values (P < 0.05). At near, the positive response times were decreased significantly (P < 0.05) in both groups, whereas the negative response times decreased significantly only in the vision training treatment group. CONCLUSIONS After 3 months, the dual treatments (altering SA and vision training) used in the study were effective in modifying accommodation. The static accommodative response to targets at proximal distances was increased by the altered SA contact lenses and rates of dynamic accommodation improved with vision training.

Increasing negative spherical aberration with soft contact lenses improves high and low contrast visual acuity in young adults

Purpose:  To evaluate the effects of a customised manipulation of spherical aberration (SA) on the high and low contrast visual acuities and contrast sensitivity of young adult myopes.

A randomised clinical trial to assess the effect of a dual treatment on myopia progression: The Cambridge Anti‐Myopia Study

To evaluate the effect of a dual treatment modality for myopia, by improving accommodative functions, on myopia progression.

The effect of soft contact lens wear and time from blink on wavefront aberration measurement variation

Introduction:  Advances in contact lens design technology allow incorporation of correction of higher‐order aberrations to improve or manipulate the eyes optical quality. Repeatability of aberration measurements in vivo with contact lens wear has not been established.

The Cambridge Anti-myopia Study: variables associated with myopia progression

Purpose To identify variables associated with myopia progression and to identify any interaction between accommodative function, myopia progression, age, and treatment effect in the Cambridge Anti-Myopia Study. Methods Contact lenses were used to improve static accommodation by altering ocular spherical aberration, and vision training was performed to improve dynamic accommodation. One hundred forty-two subjects, aged 14–21 years, were recruited who had a minimum of −0.75D of myopia. Subjects were assigned to contact lens treatment only, vision training only, contact lens treatment and vision training, or control group. Spherical aberration, lag of accommodation, accommodative convergence/accommodation (AC/A) ratio, accommodative facility, ocular biometry, and refractive error were measured at regular intervals throughout the 2-year trial. Results Ninety-five subjects completed the 24-month trial period. There was no significant difference in myopia progression between the four treatment groups at 24 months. Age, lag of accommodation, and AC/A ratio were significantly associated with myopia progression. There was a significant treatment effect at 12 months in the contact lens treatment group in younger subjects, based on a median split, aged under 16.9 years (p = 0.005). This treatment effect was not maintained over the second year of the trial. Younger subjects experienced a greater reduction in lag of accommodation with the treatment contact lens at 3 months (p = 0.03), compared to older contact lens treatment and control groups. There was no interaction between AC/A ratio and contact lens treatment effect. Conclusions Age, lag of accommodation, and AC/A ratio were significantly associated with myopia progression. Although there was no significant treatment effect at 24 months, an interaction between age and contact lens treatment suggests younger subjects may be more amenable, at least in the short term, to alteration of the visual system using optical treatments.

Meeting the UK driving vision standards with reduced contrast sensitivity

PurposeThe visual standard to hold a UK drivers license since 2012 includes visual acuity (VA) measured indoors and the ability to read a car numberplate outdoors. Individuals with reduced contrast sensitivity may have greater visual difficulties outdoors. The agreement between the two tests in the presence of combined reduction in contrast sensitivity and VA was investigated.MethodsSimulation glasses (‘sim-specs’) were used to reduce both high-contrast VA and contrast sensitivity (CS). Following evaluation of the influence of sim-specs on VA and CS, levels 2 to 4 were chosen to give a range of VAs on either side of the driving standard of 6/12. Sixty-two participants wearing sim-specs then had VA tested with Snellen and ETDRS charts indoors, and ability to read a numberplate assessed outdoors as per DVLA regulations.ResultsSim-specs reduced VA and CS by ~0.10 logMAR VA per 0.10 logCS. The sensitivity of test chart VA <6/12 to correctly predict failure on the numberplate was 61% for Snellen and 56% for ETDRS.ConclusionFalse-negative and -positive rates were higher than in a previous study with uncorrected refractive error only. Reduced CS increased the lack of agreement between the two driving vision standards, which likely occurs as the VA test is performed indoors and the numberplate test outdoors. The increased likelihood of failing the numberplate test even though VA is 6/12 or better needs to be considered when advising patients on fitness to drive who have ocular disease such as cataract.

Advising patients on visual fitness to drive: implications of revised DVLA regulations.

Aim To examine the relationship between the two UK vision standards for driving: the ability to read a number-plate at 20 m and achieving 6/12 (+0.30 logMAR). Methods 120 participants were assessed without refractive correction in this cross-sectional study. Vision was assessed with a Snellen chart, Early Treatment of Diabetic Retinopathy Study (ETDRS) style logMAR letter chart and logMAR chart using Landolt rings. Ability to read a post-2001 number-plate was assessed outdoors. Results For all charts, there was an ‘overlap zone’ of visions within which it was uncertain whether participants would pass the number-plate test. Within this zone, sensitivity and specificity of the 6/12 cut-off for predicting number-plate performance were reasonable for Snellen and ETDRS style charts, but poor for Landolt. All participants with 6/7.5 Snellen (+0.10 logMAR ETDRS) or better could read a number-plate. Some participants (2–6%) with vision between this level and 6/12 could not read a number-plate, and 14%–15% could read a number-plate but not achieve 6/12. Conclusions To best predict drivers’ ability to read a number-plate, vision should be assessed using a logMAR letter chart or a Snellen chart scored by full line. Drivers with 6/7.5 (+0.10 logMAR) or better vision can be advised that they meet the driving standard. Drivers with acuity between 6/9 and 6/12 (+0.12—+0.30 logMAR) should be advised to check their ability to read a number-plate, as some may not be able to. Clinicians will see patients who can read a number-plate, but do not achieve 6/12, who will need improved vision to meet visual requirements for driving.

Distance word acuity, critical print size and driving vision standards

A comparison was made between letter visual acuity and word acuity at distance and between letter acuity and the minimum word size allowing maximum and fluent reading speeds.