Extended wear contact lenses using high water contact lenses in aphakia.
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Aphakia, Postcataract↗
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Comparing goblet cell densities in patients wearing disposable hydrogel contact lenses versus silicone hydrogel contact lenses in an extended-wear modality.
PURPOSE: The current study evaluates the response of the ocular surface to extended contact lens wear by comparing a new silicone hydrogel lens to an ACUVUE 2 lens. METHODS: Twenty subjects with an average age of 28 years were randomly assigned to a fitting with ACUVUE 2 or PureVision lenses. Ocular surface assessment by impression cytology was performed at baseline and for the 6 months after initiation of lens wear. RESULTS: Although goblet cell density significantly increased with wear time, no statistically significant difference was observed between the contact lens groups. The average baseline goblet cell percentages were as follows: ACUVUE 2 group, 1.44; PureVision group, 1.11. The 6-month averages were as follows: ACUVUE 2 group, 3.16; PureVision group, 2.22. CONCLUSIONS: It appears that silicone hydrogel lenses may be slightly less irritating to the ocular surface than lenses not containing silicone. This could be a promising indicator for successful 30-day continuous wear.
Adult↗
Vision with disposable toric contact lenses and daily-wear toric contact lenses.
The study compared the vision, the use and evaluation criteria in a group of students with corrective daily-wear toric contact lenses and disposable toric contact lenses, in order to ascertain which of the two optical systems is more advantageous. We fitted 114 subjects with daily-wear and disposable lenses to be worn for 12 months, one type of lens in one eye and the other type in the fellow eye. The results reveal no significant differences between the two systems in terms of visual acuity attained; both lenses centred well and were comfortable. Nevertheless, the deposits were significantly greater in the daily-wear lenses. The ocular reactions were less with the disposable toric lenses. In conclusion, the disposable lenses led to fewer deposits and less ocular reactions, but are limited in parameters. However, both optical systems were appropriate for correcting for astigmatism, and provided good visual acuity.
Adolescent↗
Complications and symptoms with disposable daily wear contact lenses and conventional soft daily wear contact lenses.
We conducted a historical cohort study of 1,954 myopic cosmetic contact lens wearers (1,258 disposable soft daily wear lens users and 696 conventional [nondisposable] soft daily wear lens users). Our aim was to estimate the rates of complications and symptoms among patients using daily wear disposable contact lenses on a regular disposal regimen and to compare these with rates for conventional soft daily wear users. Patients were selected from five contact lens practices in Denmark. Data were abstracted from the eye care practitioners' office records for the period October 1987 through December 1989. Virtually all of the disposable lens users were on a two-week disposal regimen. Overall, the prevalence of complications was significantly lower among the daily wear disposable lens users than among the conventional soft daily wear lens users. The incidence of corneal ulcers did not differ significantly between the two study groups. As compared to conventional soft daily wear lens users, disposable daily wear lens users reported symptoms less frequently at routine scheduled visits and had a lower rate of unscheduled visits for complications and symptoms.
Adult↗
Aniseikonia measurement by phase difference haploscope in myopic anisometropia and unilateral aphakia (with special reference to Knapp's law and comparison between correction with spectacle lenses and contact lenses). 1971.
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Aniseikonia↗
Interactions of bacteria with contact lenses: the effect of soluble protein and carbohydrate on bacterial adhesion to contact lenses.
PURPOSE: During contact lens wear, components in the tear film adsorb to the contact lens surface to form a protein-rich coating. In this study, we investigated the importance of these components in bacterial adhesion to contact lenses. METHODS: Five strains of bacteria were tested for their ability to adhere to contact lenses (patient-worn; coated with lactoferrin, lysozyme, or an artificial tear formulation; or left uncoated) in the presence of various solutes (protein, carbohydrate). Bacterial adhesion was quantified by both a total count (light microscopy) and viable count (culturing on agar). RESULTS: None of the solutes were found to competitively inhibit bacterial adhesion to worn contact lenses. However, lactoferrin was observed to kill bacteria attached to worn contact lenses. CONCLUSIONS: We could find no evidence to indicate that bacterial adhesion to contact lenses is mediated by specific interactions between bacteria and contact lens-bound tear components. The interaction between attached bacteria and lactoferrin may be important in initiating inflammatory responses to contact lens wear.
Aeromonas hydrophila↗
An evaluation of the Cavitron Autorefractor 7 with contact lenses and non contact lens wearing patients.
The Autorefractor 7 is a microcomputor assisted electro-mechanical optical system recently introduced to the professions for the subjective measurement of refractive error, phorias, and accommodative capacity. In this study of 450 eyes, 150 were wearing hard contact lenses, 150 wearing soft lenses, and 150 habitually wore a spectacle correction. Comparisons involved only the subjective refractive feature of the instrument and indicated no predictable difference in the three groups. Comparison of the Autorefractor 7 and clinical subjective refraction with the phoropter, however, showed that the instrument is reliable in the majority of cases but has a tendency to overcorrect myopia and astigmatism.
Accommodation, Ocular↗
Patterns of mucin adherence to contact lenses.
PURPOSE: Contact lens wear alters the preocular fluid through factors that include tear deposits on the lens. In the current study, lens-adherent material was extracted to assess whether contact lenses sample mucins from the preocular fluid. METHODS: Discarded extended-wear contact lenses were collected from patients with no ocular surface disease. Mucins were extracted in guanidine hydrochloride (GuHCl) with protease inhibitors. After the supernatant was removed, the extraction was repeated twice with the addition of 10 mM dithiothreitol, making a total of three extractions. Mucins were isolated by cesium chloride (CsCl) gradient centrifugation and size fractionated on Sepharose CL2B. Charge distribution was analyzed on ion-exchange chromatography with a lithium perchlorate (LiClO(4)) gradient. RESULTS: Contact lens-adherent mucins comprised soluble mucins and mucins that required solubilization by (repeated) dithiothreitol treatment. MUC1, MUC4, MUC2, and MUC5AC mucins eluted mainly at low buoyant densities in extractions from lenses worn long term without disinfection and at successively higher buoyant densities from monthly disposable contact lenses. Mucins with little negative charge, which were observed in all extractions, and very highly negatively charged species, present in the second and third extractions from contact lenses, had no equivalents in tissue-extracted mucins. CONCLUSIONS: Mucins adhering to contact lenses are altered forms of intracellular mucins. Different degrees of adherence of mucins to contact lenses may occur, either because of mucin characteristics or after mucin complexation with adherent materials. In the context of good contact lens hygiene, their presence may offer some protection from toxicants in the tear film, because mucins could function as acceptors for charged moieties such as free radicals.
Chromatography, Ion Exchange↗
Visual correction of keratoconus with soft contact lenses.
Soft contact lenses were fitted on 96 eyes of 52 patients suffering from keratoconus. The visual acuity of 66 eyes was 4/10 or better with soft contact lenses alone. The amount of astigmatism corrected with soft contact lenses varied between 1.50 and 8.00 D, with an average of 2.80 D. Sixteen eyes had a residual astigmatism. Correcting this astigmatism with spectacles resulted in improved visual acuity, and finally, 71 eyes, or 74%, had a visual acuity 4/10 or better. Soft contact lenses of three manufacturers, Bausch & Lomb (the C series), Nusyte, and Bioflex, were used. Thicker lenses corrected more astigmatism and provided an improved visual acuity, especially the C series lenses of Bausch & Lomb, which presented certain advantages in visual correction of keratoconus patients.
Adolescent↗
Non-contact tonometry over soft contact lenses: effect of contact lens power on the measurement of intra-ocular pressure.
PURPOSE: To perform non-contact applanation tonometry over soft contact lenses and to examine any differences between the measured IOPs with and without the contact lens. METHOD: IOP was measured at one eye of eight subjects and re-evaluated through a soft lens in situ over the cornea. Seventy percent (ES70, Lunelle) water contact lenses or powers ranging from -15.00 D to +13.00 D were used. RESULTS: Mean IOP without lenses was 15.2 mmHg (S.D. = +/-4.2) and this did not change significantly for lenses ranging from -15.00 D to +3.00 D (P > 0.01) but did change for lens powers +6.00 D and above (P<0.01). The least squares line describing the change in measured IOP (deltaIOP) as a function of lens power (x) has the following characteristics, deltaIOP = 0.022 + 0.591x + 0.11x2 + 0.005x3 (r = 0.985, P = 0.0001). CONCLUSION: Non-contact tonometry can be performed with sufficient accuracy over a soft lens on condition: (a) lens centre thickness is no more 0.30 mm and (b) power is not greater than +3D.
Journal Article↗
[Optical correction of keratoconus by soft contact lenses].
Soft contact lenses have been used in 41 patients (71 eyes) aged 10-50 years with uni- and bilateral keratoconus. In 46 eyes (64.8 p.c.) application of soft contact lens enabled visual acuity of 5/5 to 5/25, mainly in initial or intermediate phases of keratoconus. In these cases correction with soft contact lenses gave better results than after application of ++sphero-cylindrical spectacles. In far advanced keratoconus one can observed better visual acuity after application of soft contact lenses in comparison with spectacles correction. However correction with hard contact lenses was the best one.
Adolescent↗
Medical applications of scleral contact lenses: 2. Gas-permeable scleral contact lenses.
The indications and outcome of the wear of gas-permeable (GP) scleral contact lenses in 118 eyes of 85 patients attending a Scleral Contact Lens Clinic during a 5-year period from July 1988 to June 1993 were analysed. Ninety-nine eyes (83.9%) were originally fitted with PMMA lenses and were subsequently changed to GP lenses, whereas 19 (16.1%) were fitted with GP lenses from the outset. The mean duration of GP scleral lens wear was 15.3 months, with a range between 3 and 58 months. The indications for refitting the cases previously wearing PMMA scleral lenses with GP material were related to problems of chronic hypoxia. Thirty-three eyes (26.8%) had previous episodes of corneal oedema, and of the 27 that had a minimum of 3 months' follow-up, none experienced further episodes of oedema. Of the 32 eyes (26%) that had developed corneal vascularisation associated with PMMA scleral lens wear, two eyes were noted to have significant vessel regression after a period of GP wear, whereas in the remainder of cases, vessels remained static and nonprogressive. Thirty additional eyes (24.2%) experienced inadequate wear times associated with discomfort, and in these eyes the change to GP scleral lenses produced a statistically significant reduction in the inability to wear lenses beyond 4 h (p < 0.05).
Adolescent↗
A 3-year prospective study of the clinical performance of daily disposable contact lenses compared with frequent replacement and conventional daily wear contact lenses.
PURPOSE: To determine the clinical performance of daily disposable contact lens wear compared to conventional daily wear contact lenses and frequent replacement contact lenses. METHODS: This 3-year prospective study was conducted in 12 U.S. practices. Of 338 eligible subjects enrolled (126 conventional daily wear, 144 frequent replacement, and 68 daily disposable), 229 subjects disposable group were compared with the conventional daily wear group and two sub-groups of frequent replacement subjects: (a) those with replacement at 2-weak intervals and (b) those with replacement at 1 or 3 months. RESULTS: Comparing the daily disposable and conventional daily wear groups, the daily disposable subjects were more likely to be asymptomatic, reported fewer symptoms of redness, cloudy vision and grittiness/dirty sensation, reported better vision and overall satisfaction, and had fewer lens surface deposits, complications, tarsal abnormalities, and unscheduled visits, while conventional daily wear subjects reported better lens handling. Comparing the daily disposable and frequent replacement (1/3 months) groups, daily disposable subjects reported fewer symptoms of foreign body sensation, redness, cloudy vision and grittiness/dirty sensation, reported better subjective vision, comfort and overall satisfaction, and has fewer lens surface deposits, complications, and tarsal abnormalities, while frequent replacement (1/3 months) subjects reported fewer dryness symptoms and better lens handling. Comparing the daily disposable and frequent replacement (2-weeks) groups, daily disposable subjects reported better subjective vision and overall satisfaction and had fewer lens surface deposits and tarsal abnormalities, while frequent replacement (2-weeks) subjects reported fewer photophobia symptoms. CONCLUSIONS: The results indicate that daily disposable wear may be the most trouble-free way of wearing contact lenses.
Adult↗
Pseudomonas corneal ulcer associated with disposable soft contact lenses.
Disposable contact lenses were developed to reduce the complications associated with cosmetic extended wear contact lenses. We describe two cases of Pseudomonas corneal ulcers that developed in patients wearing disposable soft contact lenses. Patients wearing these lenses remain at risk for infection.
Adult↗
Microbial contamination of hydrophilic contact lenses: quantitation and identification of microorganisms associated with contact lenses while on the eye.
Previous studies have demonstrated the presence of microorganisms on hydrogel contact lenses under various usage conditions. We conducted this study to quantify and identify viable bacteria and fungi associated with hydrogel contact lenses while on the eye. We removed the lenses from patients' eyes using aseptic techniques and cultured them to identify loosely adherent, as well as lens bound, microorganisms. Lenses were vortexed in a transfer medium (thereafter called the lens extract) and the lenses were then incubated in an agar sandwich separately from the transfer medium. We cultured 108 lenses (82 daily wear and 26 extended wear) from 49 patients. Bacteria were cultured from 38% (41) of the lenses; for 31 of these 41 lenses bacteria were isolated only from the lens extracts (made by vortexing lenses in a transfer medium), suggesting a transient association with the lenses. No fungi were isolated. Counts of less than 10 colony forming units (CFU)/lens were observed on 89% of the lenses. Staphylococcus epidermidis were the most frequently isolated bacteria. A statistically significant relation was observed between increased CFU/lens and increased lens age for extended wear lenses (p = 0.028).
Adult↗
Oxygen permeability of disposable soft contact lenses.
Disposable contact lenses are inexpensive hydrogel lenses that are approved for both daily and extended wear. Confusion may exist regarding the physical properties of disposable contact lenses. We used the single-chamber polarographic oxygen permeability measurement method, corrected for both boundary and edge effects, to determine objectively the oxygen permeability of three brands of disposable contact lenses. The oxygen permeability values determined for each lens material are as follows: Acuvue, 18 x 10(-11) cm2 ml O2/sec ml mm Hg (Dk); NewVues, 15 x 10(-11) Dk; and SeeQuence, 9 x 10(-11) Dk. This demonstrates that the inexpensive production techniques, which confer a relatively low unit expense, do not change the physical properties of the hydrogel materials as they relate to oxygen permeability and transmissibility. We concluded that hypoxic stress to the cornea is just as likely when using a disposable contact lens as it is when using a conventional reusable soft hydrogel lens of similar composition and water content.
Contact Lenses, Hydrophilic↗
Influence of myopia and aging on the optimal spherical aberration of soft contact lenses.
Soft contact lenses with different levels of third-order spherical aberration were tested in two samples of subjects aged between 20 and 45 years: 18 emmetropes and 19 myopes. Contrast sensitivity was measured at 12 cycles/degree to determine the optimal lens spherical aberration required by each individual. The optimal third-order coefficient was found to be negative on average in both refractive error groups. Myopic subjects required contact lenses with more negative spherical aberration than did emmetropes. The optimal aberration was also found to become increasingly negative with aging. The rate of this age-related change was faster in the myopic group. In comparison with aberration-free soft contact lenses, an improvement in contrast detection threshold of more than 25% was observed with optimal spherical aberration in half of the myopic subjects.
Adult↗
Editorial: Soft contact lenses.
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Contact Lenses↗