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PubMed1998

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↗
PubMed1995

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↗
PubMed1985

Alpha neoprotein molecules in normal lenses from animals of different ages and in cataractous lenses.

Alpha neoprotein molecules are formed by an association of A and B subunits resulting in a different quaternary structure than in alpha crystallin. The content of alpha neoprotein vs. alpha crystallin was estimated separately on the crystallin, cryoprotein and albuminoid fractions in lenses of animals of different species and ages, in lenses with experimentally induced cataracts and in human cataractous lenses. Alpha crystallin was determined on immunoadsorbents with bound antibodies restricted to quaternary determinants of this protein. Alpha neoprotein molecules were determined in the filtrate containing lens proteins not bound on the above immunoadsorbent. The filtrate was applied on an anti-A chain immunoadsorbent, and after desorption the A chain-containing molecules were applied on an anti-B chain immunoadsorbent. The amount of lens proteins bound to the latter immunoadsorbent gave a measure of molecules formed by an association of A with B chains other than in alpha crystallin, that is of alpha neoproteins. No alpha neoprotein was present in lenses from 2-week-old rats or in the 3- to 6-month-old calf lens cortex. The 2-year-old bovine lens nucleus did contain alpha neoproteins, but only in the albuminoid fraction. The lenses of adult rats (i.e. 3- to 4-month-old) contained alpha neoprotein molecules mainly in the albuminoid fraction; small amounts were also found in the cryoprotein fraction. All three fractions of lens proteins from 1-year-old rats contained alpha neoprotein molecules. No significant differences in the content of alpha neoprotein molecules were found in lenses with experimentally induced X-ray and galactose cataracts and in normal controls. This finding does not exclude possible structural differences between normal and cataractous alpha neoproteins. In human senile cataractous lenses, the content of alpha neoprotein molecules in all fractions analyzed equaled or exceeded the content of alpha crystallin present. The present findings demonstrate an age-dependent formation in the mammalian lens of alpha crystallin neoproteins lacking native quaternary determinants. The data obtained point to the possibility that the structural lability of alpha crystallin may be a contributing factor in cataractogenesis.

Aging↗
PubMed2004

A 6-month follow-up of successful refits from daily disposable soft contact lenses to continuous wear of high-Dk silicone-hydrogel lenses.

PURPOSE: To compare, in routine optometric practice, the outcome of keeping successful soft contact lens (SCL) wearers in their lenses to re-fitting them with continuous wear of silicone hydrogel (SiH) lenses. METHODS: Forty-nine successful daily disposable lens wearers were recruited; 19 continued to wear daily SCLs and 30 were refitted with high-Dk SiH lenses on a 30-day/night schedule. Patients were assessed at baseline, 3 and 6 months by slit lamp examination along with the Efron grading scales, and central corneal thickness (CCT) and the corneal endothelium were assessed by non-contact specular microscopy. RESULTS: No substantial changes in subjective vision, refraction, visual acuity or overall lens comfort occurred for those completing the study, although five SiH lens wearers did discontinue due to reduced comfort, eyelid problems or seasonal allergy. Contact lens induced peripheral ulcers (CLPU) were observed in three patients in the first 3 months in the SiH lens group and these were also discontinued. Over the 6 month period, a complete set of records was obtained for 16 in each group. For those completing the study, lens dryness scores were variable, but there was a slight improvement in favour of SiH lenses. Small, but statistically significant, reductions in corneal staining, bulbar hyperaemia, and limbal neovascularisation in favour of the SiH lenses were also evident but mainly because of further increases in the daily lens wearers. Contact lens induced papillary conjunctivitis (CLPC) and corneal endothelial polymegethism were mild to moderate and showed slight increases in the daily lens wearers at 6 months. CONCLUSIONS: The present studies confirm that the continuous wear of SiH lenses for up to 30 days can be considered as an alternative to daily disposable soft lens wear, but is not suitable for everyone.

Adult↗
PubMed2003

Therapeutic contact lenses: the role of high-Dk lenses.

Currently, the armamentarium of contact lenses that can be used for therapeutic effect provides a wider selection of lenses than ever before. If the therapeutic goal is protection and healing of the corneal epithelium, epithelial or stromal edema is best avoided, and the selection of a high-Dk silicone hydrogel (balafilcon A, lotrafilcon A) lens or a very thin membrane-type lens (crofilcon) is the best choice. If the goal is surface protection as well as stimulation of stromal wound vascularization, selection of a low-water content, thick, hydrophilic lens is the better option. If the patient is prone to lens loss or requires frequent replacement of the therapeutic lens, a prudent economic decision is to select a daily disposable moderate-water content lens. Specific circumstances may mandate the selection of a specific therapeutic lens. Patients with a prior history of active giant papillary conjunctivitis may be better served by the use of a crofilcon glyceryl methacrylate lens, which has a lower incidence of this complication. Patients who have dry eye may benefit from a higher-water content lens if adequate unpreserved tear supplementation is provided with or without punctal occlusion. The options when selecting a therapeutic contact lens are wider than ever before. Although the new generation of high-Dk lenses promises fewer limiting problems of vascularization and infection, one can use the older traditional therapeutic lenses when induced vascularization of the cornea is needed or when an economic necessity exists. Not all of the available lenses are FDA approved for therapeutic use, and such wear is an off-label use. The patient should be informed of the goal of therapy as well as the benefits and risks of therapeutic contact lenses.

Contact Lenses↗
PubMed1993

Comparison between "readables" aspheric spectacle lenses and conventional spherical spectacle lenses for overcorrection of presbyopic single-vision contact lens wearers.

Binocular spectacle overcorrection for near with "Readables" progressive-addition lenses and with lenses having spherical surfaces were compared by 36 successful presbyopic wearers of single-vision contact lenses. The two forms of near correction were each worn by these subjects for 3 weeks in a randomized cross-over study and were also directly compared for 1 week in which both overcorrections were available. "Readables" spectacle correction was significantly better than the conventional overcorrection in four of the five patient response categories studied (visual comfort, close vision, intermediate vision, and function without removal) and was not significantly different in one of the five categories (ability to adapt). When asked to choose between the two near corrections, 81 percent of the subjects (29 of 36) preferred their "Readables" spectacles. It appears that "Readables" spectacle lenses offer a viable alternative to single-vision lenses when used for near correction of presbyopic patients wearing single-vision contact lenses for distance correction.

Adult↗
PubMed2003

Corneal hypoxia secondary to contact lenses: the effect of high-Dk lenses.

Contact lenses made from materials of low-oxygen permeability (Dk) do not meet the oxygen requirements of the cornea for overnight wear. Long-term extended wear of these lenses results in chronic changes to all layers of the cornea, many of which are associated with hypoxia. High-Dk silicone hydrogel and gas permeable lenses are now available for 30-night continuous wear. The high-oxygen transmissibilities of these lenses have enabled the development of a successful continuous wear modality by eliminating the hypoxic effects of long-term wear. Presently, the focus is on improving lens performance by developing lenses that are more biocompatible, provide greater comfort, and maintain a stable tear film without inflammatory or mechanically induced adverse events.

Contact Lenses↗
PubMed1975

Comparison of soflens contact lenses (polymacon) with hard contact lenses and spectacles.

A study, comparing Soflens TM contact lenses (polymacon) with hard contact lenses and spectacles, and using 150 male and female patients, has been done. Volunteers qualified for the study if they had healthy eyes and had worn one type of corrective lenses for six months before they were interviewed and examined. During each patient's examination, his type of correction was not known. Such matters as visual acuity, corneal measurements and average wearing time were considered. (Soflens contact lenses were felt to be safer than hard contact lenses.)

Adolescent↗
PubMed1996

A new matrix formulation of spectacle magnification using pupil magnification. II and III: High myopia corrected with contact lenses and intraocular lenses.

In this paper we use the matrix method to calculate spectacle magnification (SM) and relative spectacle magnification (RSM) using pupil magnification for myopic eyes corrected with contact lenses (CLs), and intraocular lenses (IOLs). For myopic eyes corrected with contact lenses, the calculation is very similar to the one done for myopic eyes corrected with ophthalmic lenses (OLs) since both OLs and CLs are external correcting systems. For myopic eyes corrected with intraocular lenses, the calculation is different from the ones carried out for myopic eyes with external correcting systems. In this paper we show the differences that exist between the matrix calculations for these two correcting systems, external and internal. The magnifications are calculated for specific myopic eyes corrected with CLs and IOLs. By comparing the results obtained with three correction types, namely, OLs, CLs and IOLs, we will be able to choose the best correction system for each case.

Contact Lenses↗
PubMed2001

[Complication profiles of posterior chamber intraocular lenses IOL). An analysis of 586 foldable and 2077 rigid explanted intraocular lenses].

BACKGROUND: Foldable intraocular lenses (IOL) have become increasingly preferred choice for IOL implantation after cataract removal. However, both foldable as well as rigid IOLs are not yet complication-free and may need explanation. MATERIAL AND METHODS: A total of 2663 explanted posterior chamber IOLs (PCIOLs) were accessioned at the Center for Research on Ocular Therapeutics and Biodevices between January 1988 and September 2000. The lenses were examined grossly using a Leitz/Wild M-8-Zoom stereomicroscope. The clinical reasons for explanation were documented for foldable as well as for rigid lenses. RESULTS: Of a total of 2663 explanted PCIOLs, 586 were foldable lenses and 2077 were rigid PMMA lenses The most frequent reason for explantation of all 2663 IOLs studied was decentration/dislocation. Optic and haptic damage and posterior capsule rupture were significantly more often a reason for explantation in several foldable designs compared to rigid PCIOLs. Whereas rigid designs lead more often to corneal decompensation. The percentage of explanted IOLs because of inflammatory reactions decreased significantly from 1994 to 2000. CONCLUSIONS: The complication profiles of rigid and foldable IOLs revealed some apparent differences due to the nature of the IOL biomaterials and designs. IOL optic/haptic damage was a common complication for foldable IOLs, whereas it was only discovered in single digits for rigid PMMA IOLs. The possible explanation for this is, that the soft and flexible biomaterials, from which all the foldable IOLs were manufactured, are easier to be damaged during folding, unfolding and insertion procedure. In our opinion this relative disadvantage of foldable IOLs is by far outweighed by the numerous advantages of the small incision cataract surgery. The decreasing inflammatory reactions can be explained by advances in surgical techniques, especially the secure in-the-bag fixation of IOLs.

Humans↗
PubMed2006

Ocular motor triad with single vision contact lenses compared to spectacle lenses.

AIM: Theoretically myopes are required to exert more accommodation and vergence when wearing single vision contact lenses compared to glasses and hypermetropes less. This study aims to quantify the effects clinically. METHOD: Thirty subjects (21 female, nine male, average age 21.0+/-2.2 years) with a range of refractive errors (-7.87 D to +3.50 D) viewed in a random order, static targets at 0.1, 0.5, 1.0, 2.0, 3.0, 4.0 and 5.0 D accommodative demand that were matched for angular subtense. The subjects were fully corrected with spectacles and daily disposable contact lenses to their full prescription. Accommodation was monitored objectively with the PowerRefractor and Shin-Nippon SRW5000 and vergence and pupil size with the PowerRefractor. RESULTS: Myopes exerted greater accommodative effort for viewing near targets with contact lenses than glasses and hypermetropes less (r(2)=0.35, p=0.001 PowerRefractor). Myopes also exerted greater vergence effort for viewing near targets with contact lenses than glasses and hypermetropes less (r(2)=0.22, p<0.01). CONCLUSION: Theoretical calculation of the accommodative and vergence requirements with glasses compared to contact lenses reflect clinical findings, although there is reasonable variability between individuals.

Accommodation, Ocular↗
PubMed2006

Initial comfort of lotrafilcon A silicone hydrogel contact lenses versus etafilcon A contact lenses for extended wear.

PURPOSE: To compare the initial comfort afforded by silicone hydrogel lenses (lotrafilcon A) versus the comfort afforded by conventional hydrogel lenses (etafilcon A) in extended wear (EW). DESIGN: Prospective, double-masked and randomized controlled trial. METHODS: Lotrafilcon A and etafilcon A contact lenses were eye randomly fitted on an EW basis for 7 days and nights in 20 subjects. A forced-choice subject preference questionnaire was made. Subjects were comfort, dryness, red eye and visual quality after night wear and at the end of the day. Subjective scored satisfaction (scale: 1-5) and lens preference were assessed. RESULTS: Lotrafilcon A proved more comfortable after night wear (60%, CI95% 38-82%) and at the end of the day (70%, CI95% 49-90%) than etafilcon A after night wear (10%, CI95% 0-23%, P<0.05) and at the end of the day (20%, CI95% 2-38%, P<0.05). The feeling of dryness was more marked with etafilcon A after night wear (50%, CI95% 27-72%) and at the end of the day (50%, CI95% 27-72%) than it was with lotrafilcon A (15%, CI95% 0%-31%) after night wear (P>0.05) and at the end of the day (25%, CI95% 5%-44%, P<0.05). General satisfaction with the lotrafilcon A lens was 3.65 points (CI95% 3-4.2) and with etafilcon A 2.95 points (CI95% 2.5-3.3, P<0.05). Eighty percent (CI95% 62%-98%) of subjects preferred lotrafilcon A (P<0.05) for EW. CONCLUSIONS: In EW, lotrafilcon A contact lenses were more comfortable and led to less dryness after night wear and at the end of the day than etafilcon A contact lenses.

Adolescent↗
PubMed2003

Opacification of hydrophilic acrylic intraocular lenses: a clinical and ultrastructural analysis of three explanted lenses.

BACKGROUND: The purpose of our study was to report the clinical and ultrastructural results of the late opacification of three Hydroview intraocular lenses (IOLs) explanted from three patients with late postoperative visual acuity drop. PATIENTS AND METHODS: Three different patients without any systemic or ocular associated pathology presented with decreased visual acuity 12 to 24 months after uneventful phacoemulsification and Hydroview IOL implantation. The lenses were explanted and examined by photon and transmission electron microscopy (TEM), as well as through laboratory chemical analysis using bleaching with H 2 O 2, SDS-electrophoresis and silver staining for protein detection. They were cut in small pieces, fixed with osmium tetroxide 1.5 %, dehydrated through ascending grades of ethanol, and embedded in EPON 812. Ultrathin sections were stained with aqueous solutions of uranyl acetate and lead citrate, and they were examined with JEOL 2000 CX TEM. One normal IOL was also prepared in the same way and served as control. RESULTS CONTROL: It was transparent and no material on the surface of semithin and thin sections was detected. Cases 1 and 2: A total gray-whitish opacification of these lenses occurred. An amorphous loose material was present on semithin sections in alternation with normal areas. Evaluation with TEM revealed a pattern of network distribution within the lenses material. The latter was continuous and lightly granulated at the periphery, yet irregularly arranged in the center, more intensely stained, leaving areas of normal appearance. After bleaching, no changes in opacification were seen macroscopically. SDS-electrophoresis and silver staining did not detect proteins. Case 3: This lens had a small opacification close to the periphery. CONCLUSIONS: Late opacification of hydrophilic IOLs is not an uncommon phenomenon after uneventful cataract surgery. Although calcified deposits on the surfaces of such lenses have been reported, this is the first study that describes ultrastructural changes in the IOL material itself.

Aged↗
PubMed1998

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↗
PubMed1992

Microbial contamination of hydrophilic contact lenses. Part I: Quantitation of microbes on patient worn-and-handled lenses.

We cultured Soflens (polymacon) contact lenses to determine the number of microorganisms present following normal patient wear and handling just prior to disinfection. Total protein deposited was determined for the companion lens from each patient. A random population of 109 adapted soft contact lens patients participated in the study. Some patients participated more than once, resulting in a total of 196 lenses being cultured and 195 lenses analyzed for total protein. The left lens was cultured immediately. The right lens was extracted at 70 degrees C in sodium hydroxide, and the total protein in the extract determined using a modified Lowry protein assay. The mean protein deposition per lens was 3.4 micrograms (median 2 micrograms per lens; range less than 1 to 78 micrograms/lens). Microorganisms were cultured from 95% of the lenses. The mean bacterial count (in colony forming units per lens) was 2,482 (median: 123; range less than 3 to 150,000). Fungal contamination was found on 11% of the lenses at very low levels (3-9 yeast/lens and 3-18 mold/lens). Statistical analysis found no significant relationship between bacterial bioburden and any of the study parameters, including total protein, lens age, or subjective evaluation of lens cleanliness.

Bacteria↗
PubMed1998

Influence of special-effect contact lenses (Crazy Lenses) on visual function.

PURPOSE: Special-effect contact lenses (opaque, tinted soft contact lenses that incorporate decorative images such as "cateyes," stars, or hearts to alter eye color and structure) have become increasingly popular. The purpose of this study was to investigate whether such lenses impair visual function. METHODS: A clear soft contact lens and a special-effect soft contact lens (Crazy lens,) were fit in changing sequence in nine healthy subjects. The parameters studied included: visual acuity, contrast sensitivity (with and without glare), visual field, and mesopic vision (with and without glare). RESULTS: The following parameters displayed a statistically significant difference (P < 0.05). Visual acuity was decreased to 0.9 +/- 0.23 in the Crazy lens group as compared with 1.2 +/- 0.13 in the clear lens group. Goldmann visual field displayed a significant constriction of the isopters: III/4, I/4, and I/3. Mesopic vision without glare was reduced from 1:2.5 to 1:7.4. Contrast sensitivity was significantly reduced in a photopic condition with and without glare and in a scotopic condition without glare. Furthermore, the special-effect lenses were associated with a decrease in lens wearing comfort. CONCLUSIONS: Special-effect contact lenses were associated with a reduction of many visual functions, including visual acuity and contrast sensitivity. For some wearers this may interfere with activities where excellent vision is crucial, such as driving a car.

Adult↗
PubMed2004

Will visual discomfort among visual display unit (VDU) users change in development when moving from single vision lenses to specially designed VDU progressive lenses?

PURPOSE: Three types of progressive additions lenses (PAL) specially designed for VDU-work and one single vision lens were compared in a prospective field study. The aim was to investigate if these progressive lenses created a difference in the development of visual discomfort compared to single vision lenses when working on an optimized VDU-workstation. METHODS: The study had a prospective, parallel group design, with four groups of VDU-workers. Approximately 40 subjects in each group, selected after careful task analysis with special attention towards the visual angles and distances to the work tasks. The groups were followed over one year. A questionnaire concerning visual conditions, working conditions, discomfort in different body areas, the status of the subjects' optometric corrections, psychological factors both at work and at home, amount, frequency and duration of VDU-work etc. was filled in before the intervention, after six months and after one year. No other contact was made with the subjects. The VDU-lenses included were Interview (Essilor), Gradal RD (Zeiss) and Technica (American Optical). Pain intensity and duration were assessed on a 100 mm Visual Analogue Scale (VAS) before the intervention, and six and twelve months after the intervention. All subjects were given a complete optometric examination. RESULTS: Only small changes in the development of headache and visual discomfort were registered. However, the subjective evaluation of area of clear vision and overall satisfaction was significantly improved for the Interview and Gradal RD lens (p < 0.05). There were no significant changes for Technica and single vision lenses. CONCLUSION: Lens designs that cover viewing distances from near and out to approximately 2 meters work well compared to lens designs trying to cover greater range of clear vision. When tasks analysis shows that single vision correction may be used, this is still an acceptable solution.

Computer Terminals↗
PubMed1979

Extended-wear contact lenses and intraocular lenses for aphakic correction.

We evaluated extended-wear soft contact lens use in 128 aphakic eyes of 113 patients, 44 of whom had been unable to wear conventional contact lenses; 116 eyes (91%) have been successfully fitted and have worn the extended-wear lenses without significant complication. Eleven patients were unable to wear the lens or had to be discontinued for transient lens-related problems. In 103 eyes successfully fitted the lens is removed for cleaning less often than monthly. Ninety six of the 116 eyes fitted have visual acuity as good as, or better than, with aphakic correcting spectacles. The results obtained with the extended-wear soft contact lens are similar to those obtained with intraocular lenses, except for the recent high incidence of inflammation seen after intraocular lens insertion when using ethylene-oxide-sterilized lenses.

Adolescent↗