Changes in contrast sensitivity when wearing low, medium and high water content soft lenses

doi:10.1016/S0141-7037(86)80010-6

Journal of The British Contact Lens Association

Volume 9, Issue 1, 1986, Pages 21-25

Journal of The Briti...

https://doi.org/10.1016/S0141-7037(86)80010-6 Get rights and content

Abstract

The effect of soft lens water content on the contrast sensitivity function was investigated bymeasuring the contrast sensitivity of 6 subjects, each wearing soft lenses of 38.6, 50.0 and 67.5% water content. (All other lens parameters were constant). Results demonstrated an inverse relationship, i.e. the lower the water content, the greater the reduction in contrast sensitivity. It is hypothesised that the amount and cause of the contrast sensitivity decrement is dependent on the oxygen transmissibility of the soft lenses and therefore, in turn, corneal oedema.

References (34)

GuillonM.
Long term effects of soft contact lenses — a preliminary report
J. Brit. Contact Lens Assoc.
(1981)
GuillonM. et al.
Variations in contrast sensitivity function with spectacles and contact lenses
J. Brit. Contact Lens Assoc.
(1983)
SammonsW.A.
Thin lens design and average thickness
J. Brit. Contact Lens Ass.
(1981)
SheridanM. et al.
Changes in the water content of Hydrogel lenses during wear
J. Brit. Contact Lens Ass.
(1983)
ApplegateR.A. et al.
Changes in the contrast sensitivity function induced by contact lens wear
Amer. J. Optom. & Physiol. Opt.
(1975)
ArdenG.B.
The importance of measuring contrast sensitivity in cases of visual disturbance
Br. J. Ophthalmol.
(1978)
BarrJ.T. et al.
Corneal endothelial response to rigid contact lenses
Am. J. Optom & Physiol. Opt.
(1980)
BauerG.T.
Experimental study of the bending-induced change of the power and longitudinal spherical aberration of soft contact lenses
J. Lpt. Soc. Am.
(1979)
BernsteinI.H. et al.
Contrast sensitivities through spectacles and soft contact lenses
Amer. J. Optom. & Physiol. Opt.
(1981)
Bodis-WollnerI.
Detection of visual defects using the contrast sensitivity function
Int. Ophthalmol. Clin.
(1980)

DeDonatoL.M.

Changes in the hydration of Hydrogel contact lenses with wear

Am. J. Optom. & Physiol. Optics.

(1982)

FattI.

Gas Transmission Properties of Soft Contact Lenses

GassonA.

Visual considerations with hydrophilic lenses

The Ophthalmic Optician

(1975)

GrosvenorT.

Visual acuity, astigmatism and soft contact lenses

Am. J. Optom. Arch. Am. Acad. Optom.

(1972)

HessR.F. et al.

The effect of corneal oedema on visual function

Invest. Ophthal Vis. Sci.

(1977)

MandellR.B. et al.

Theory of the contact lens adaptation process

J. Amer. Optom. Assoc.

(1968)

MandellR.B. et al.

Corneal swelling caused by contact lens wear

Arch. Ophthal.

(1970)

Cited by (28)

Sports Vision: Vision Care for the Enhancement of Sports Performance
2020, Sports Vision: Vision Care for the Enhancement of Sports Performance
Reliability of a computer-based system for measuring visual performance skills
2011, Optometry
Citation Excerpt :
Ginsburg20 also showed that higher spatial frequencies will be affected before lower spatial frequencies by changes in target distance, movement direction, and low illumination. Contrast sensitivity also may be degraded in contact lens wearers if lens fit or water content are not optimal for the patient, resulting in corneal edema even when SVA seems acceptable.21 Finally, contrast sensitivity can increase or decrease after refractive surgery.22
Athletes have demonstrated better visual abilities than nonathletes. A vision assessment for an athlete should include methods to evaluate the quality of visual performance skills in the most appropriate, accurate, and repeatable manner. This study determines the reliability of the visual performance measures assessed with a computer-based system, known as the Nike Sensory Station.
One hundred twenty-five subjects (56 men, 69 women), age 18 to 30, completed Phase I of the study. Subjects attended 2 sessions, separated by at least 1 week, in which identical protocols were followed. Subjects completed the following assessments: Visual Clarity, Contrast Sensitivity, Depth Perception, Near–Far Quickness, Target Capture, Perception Span, Eye–Hand Coordination, Go/No Go, and Reaction Time. An additional 36 subjects (20 men, 16 women), age 22 to 35, completed Phase II of the study involving modifications to the equipment, instructions, and protocols from Phase I.
Results show no significant change in performance over time on assessments of Visual Clarity, Contrast Sensitivity, Depth Perception, Target Capture, Perception Span, and Reaction Time. Performance did improve over time for Near-Far Quickness, Eye-Hand Coordination, and Go/No Go.
The results of this study show that many of the Nike Sensory Station assessments show repeatability and no learning effect over time. The measures that did improve across sessions show an expected learning effect caused by the motor response characteristics being measured.
Central and peripheral visual performance in myopes: Contact lenses versus spectacles
2011, Contact Lens and Anterior Eye
Citation Excerpt :
The majority of studies considering this subject were undertaken in the 1980's or before, when soft contact lenses were either spun cast or lathe cut, and suffered from poor homogeneity and surface quality [18]. Lens materials also had lower oxygen transmissibility than modern lenses, giving rise to the potential for corneal oedema and a subsequent reduction in contrast sensitivity [38]. Lens designs, materials and manufacturing techniques have improved significantly over the last two decades and daily disposable soft contact lenses account for close to 60% of the UK contact lens market (ACLM report 2009), because of their convenience and the absence of deposit problems [39].
Myopia is known to degrade visual performance with both optical and retinal changes implicated. Whether contact lenses or spectacles provide better visual performance for myopes is still under debate. The purpose of this study was to examine central and peripheral visual function in myopic subjects corrected with contact lenses versus spectacles.
Size thresholds were measured at 13 locations for 20 myopic subjects (mean spherical equivalent refractive error (SE): −6.43 ± 1.22 D and cylinder power: −0.23 ± 0.22 D) corrected with contact lenses (new etafilcon A contact lens, fitted 15 min prior to measurements) versus spectacles. Measurements were taken at both low (δl/l = 14%) and high (δl/l = 100%) contrast levels. The data were analysed using one way repeated-measures ANOVA.
Size thresholds increased with eccentricity in a similar manner for both forms of optical correction. Repeated-measures ANOVA showed no statistically significant difference in central and peripheral visual performance between the two forms of correction for both low and high contrast tasks. The outcome remained the same following correction for spectacle magnification.
Eye care practitioners can be confident that modern soft contact lenses do not impair visual performance compared to spectacle lenses for the majority of myopes.
Clinical performances of two disposable soft contact lenses of different materials on Hong Kong-Chinese
2000, Contact Lens and Anterior Eye
Dryness due to contact lens wear and poor wetting of contact lenses among contact lens wearers is a common observation and contact lens manufacturers have introduced new, better quality soft lens materials that are claimed to be more deposit resistant, and/or dehydration resistant. The purpose of this study was to evaluate and compare the clinical performance of Hydron ActiSoft 60§, made of a new material (HyGMA™) which is claimed to be dehydration resistant with excellent wettability, with ActiFresh 400, made of conventional non-ionic hydrogel material. The experiment was conducted as a double-masked, randomised, cross-over study. Clinical assessment included pre-lens non-invasive tear break up time (PL-NITBUT), logMar visual acuity and contrast sensitivity (CS). Corneal staining, if any, was recorded at each visit. Subjective ratings in regard to dryness, grittiness, lens awareness, vision, comfort, handling (removal), handling (cleaning) and the overall preference of each lens type were obtained at the end of 3 (Phase A) and 6 months' (Phase B) wear. Twenty-eight subjects successfully completed the study. In Phase A, no significant differences were found in both baseline PL-NITBUT and PL-NITBUT after wearing the same lenses for 1 month between the two lens types. In phase B, baseline PL-NITBUT for ActiFresh 400 was significantly shorter than that for ActiSoft 60. However, after 1 month of wear, the difference in PL-NITBUT between the two lens types was no longer significant. PL-NITBUT was significantly reduced after 1 month's wear for both ActiSoft 60 and Actifresh 400, and in both Phase A and Phase B. The two lens types provided comparable logMAR visual acuity, and there was no significant differences in CS (Pelli Robson) between spectacle lens correction (equivalent spheres) and either lens type. The incidence of corneal epithelial staining was significantly higher and more severe with ActiFresh 400 than with ActiSoft 60, both in Phase A and Phase B. Statistically, there were no significant differences in the scores to the set of questions listed in the questionnaire between the two lens types, except for lens awareness and lens handling. Of the subjects having a preference for one lens, more subjects preferred ActiSoft 60 than ActiFresh 400. In terms of overall preference of the two lens types, at the end of Phase A, 50% of the subjects preferred ActiSoft 60 while only 30% preferred ActiFresh 400, the remaining 20% had no preference. However, by the end of Phase B, preferences for ActiSoft 60 and ActiFresh 400 were comparable. This appeared to be due mainly to the ease of lens handling of the latter.
Comparative study on the clinical performance of acuvue and focus contact lenses
1997, International Contact Lens Clinic
We compared the visual performance of Acuvue and Focus contact lenses with spectacle correction; 17 Hong Kong-Chinese were recruited, and contrast thresholds (at spatial frequencies of 1.0, 4.0, and 16.0 c/deg) were measured for each type of correction. Our results showed that the level of myopia did not affect the contrast thresholds measured for each type of correction at all levels of spatial frequencies tested. There was also no significant difference in the contrast thresholds between types of correction used. The subjective performances of the two brands of lens used were also assessed by asking each subject to answer a questionnaire at the end of the study. The scorings in the questionnaire for Focus were consistently more favorable than those for Acuvue for all symptom variables. This suggested that subjects preferred Focus to Acuvue, although the differences did not reach statistical significance. Our results also showed that “lens discomfort” was the most powerful symptom variable that determined a subject's overall lens preference.
Determination of the total attenuation coefficient for six contact lens materials using the Beer-Lambert law
1996, Ophthalmic and Physiological Optics
The Beer—Lambert law has been used to determine the total attenuation coefficient, μ_t, of three hard and three soft contact lens materials. The three hard contact lens materials were PMMA, Polycon II and Boston IV whereas the 3 soft materials were chosen with differing water contents of 38, 55 and 70%, respectively. The total attenuation coefficients of all six materials were obtained from measurements of the axial transmission at 632.8 nm of a series of plano powered lenses varying in axial thickness from 0.5 to 3.5 mm. The value of the total attenuation coefficient depends on both scattering and absorption and hence PMMA and Boston IV, which both incorporated a handling tint, showed significantly higher values (P < 0.0001) ofμ_t (0.562 ± 0.010mm⁻¹and 0.820 ± 0.008mm⁻¹, respectively) than Polycon II (μ_t = 0.025 ± 0.005mm⁻¹). A comparison between Polycon II and the three hydrated soft contact lens materials showed a significant increase (P < 0.02) in the total attenuation coefficients for the 38% and 55% water content materials, and a weakly significant increase for the 70% water content soft lens material (P < 0.1). On the assumption that the absorption coefficients of these four materials are approximately constant, then this change would be due to an increase in the scattering coefficient of the material and could contribute to an increase in intraocular scatter. No significant difference (P > 0.5) was found between any of the hydrated soft contact lens materials tested.

View all citing articles on Scopus

^*: C. P. Grey, BSc, MSc, FBCO, Postgraduate School of Studies in Optometry and Physiological Optics, University of Bradford, Bradford, West Yorkshire BD7 1DP.

View full text

Changes in contrast sensitivity when wearing low, medium and high water content soft lenses

Abstract

J. Brit. Contact Lens Assoc.

J. Brit. Contact Lens Assoc.

J. Brit. Contact Lens Ass.

J. Brit. Contact Lens Ass.

Changes in the contrast sensitivity function induced by contact lens wear

Amer. J. Optom. & Physiol. Opt.

The importance of measuring contrast sensitivity in cases of visual disturbance

Br. J. Ophthalmol.

Corneal endothelial response to rigid contact lenses

Am. J. Optom & Physiol. Opt.

Experimental study of the bending-induced change of the power and longitudinal spherical aberration of soft contact lenses

J. Lpt. Soc. Am.

Contrast sensitivities through spectacles and soft contact lenses