Types Of Contact Lenses Research Articles

써클콘택트렌즈의 염료 용출에 대한 연구

목적: 본 연구는 면봉으로 문지르기를 하였을 때 써클콘택트렌즈로부터의 염료 용출 여부를 알아보기 위하여 수행되었다. 방법: 총 7종의 써클콘택트렌즈를 면봉으로 문질렀을 때 표면의 변화를 주사전자현미경으로 관찰하고, <TEX>$20^{\circ}C$</TEX> 및 <TEX>$36.5^{\circ}C$</TEX>에서 각각 다목적용액에 1 주일간 담가두었을 때의 염료용출과 비교하였다. 결과: 면봉으로 문지르기를 하였을 때 전면 혹은 후면에서 염료가 용출되어 나오는 렌즈는 총 7종 중 5종으로 나타났으며, 염료 용출 여부는 써클콘택트렌즈 종류에 따라 상이하였고 동일 써클콘택트렌즈라 하더라도 전면과 후면에서 상이하였다. 염료가 용출된 경우는 문지르기로 인하여 염료 부분이 긁혀 나감을 주사전자현미경 관찰을 통하여 확인할 수 있었다. 그러나 다목적용액에 <TEX>$20^{\circ}C$</TEX> 혹은 <TEX>$36.5^{\circ}C$</TEX>에 1 주일간 담궈 두었을 때에는 염료는 용출되지 않았다. 실험 대상 써클콘택트렌즈 중 50% 이상의 제조사에서 착색제의 성분에 대한 정보를 제공하지 않고 있으며 염색방법 등과 같은 기본정보들이 부실하게 제공되고 있었다. 결론: 본 연구에서는 물리적인 힘이 가해졌을 때 써클콘택트렌즈의 염료 용출에 대한 결과를 도출하였고 써클콘택트렌즈의 개발 및 안전한 착용에 기여할 것으로 보인다. Purpose: The present study was conducted to investigate whether the elution of the dyes from the circle contact lenses existed or not when rubbed with cotton swab. Methods: The change of lens surface was observed by scanning electron microscope when a total of seven kinds of circle contact lens were rubbed with cotton swab, and the dye elution was further compared when the lenses were soaked in multi-purpose solution in <TEX>$20^{\circ}C$</TEX> and <TEX>$36.5^{\circ}C$</TEX> for a week. Results: Five of a total of 7 circle contact lenses showed the dye elution from the front or the back surface of the lens when rubbed with cotton swabs, and existence of dye elution was varied depending on the type of contact lenses and different at the front and back surface even in the same lens. The tear-off of the pigmented portion by the rubbing was found through scanning electron microscopic observation when the dye elution existed. However, the dye was not eluted when the circle contact lenses was soaked in a multi-purpose solution in <TEX>$20^{\circ}C$</TEX> or <TEX>$36.5^{\circ}C$</TEX> for a week. Ingredient of colorant was not provided by the manufacturers in more than 50% of the circle contact lenses investigated for this study and the basic information such as the pigmentation method was provided inappropriately. Conclusions: In this study, the result was the dye elution from circle contact lenses was obtained when a physical force is applied thus, it may appear to contribute the development of circle contact lenses and safety of lens wear.

Studying functional properties of hydrogel and silicone–hydrogel contact lenses with PALS, MIR and Raman spectroscopy

Determination of free volume holes of the hydrogel and silicone–hydrogel polymer contact lenses were investigated. Two types of polymer contact lenses were used as materials: the first is a hydrogel contact lenses Proclear family (Omafilcon A), while the second is a silicone–hydrogel contact lens of the family Biofinity (Comfilcon A). Positron annihilation lifetime spectroscopy PALS was used to characterize geometrical sizes and fraction of the free volume holes in the investigated samples. There is a clear difference in the free volume sizes and their fractions between silicone–hydrogel and polymer hydrogel contact lenses which in turn are connected with oxygen permeability in these lenses. Apart from that, spectroscopic (middle infrared) MIR and Raman examinations were carried out in order to demonstrate the differences of the water content in the test contact lenses.

Cosmetic Contact Lenses and Iris Recognition Spoofing

Automatically detecting novel types of cosmetic contact lenses in iris images is a very difficult pattern-recognition problem, but experimental datasets that enable researchers to study this problem have recently become available.

Contact Lens Fitting and Long-Term Management for the Boston Keratoprosthesis

To examine the types of contact lenses used as bandage lenses in the postoperative management of patients with Boston type 1 keratoprosthesis (K-Pro). We examined the lens parameters, the number of trial lenses used to achieve successful fit, and lens replacement schedule. The strategies to achieving a successful fit in these complex patients are reviewed. This was a single-center, retrospective chart review of patients who had undergone implantation of the Boston keratoprosthesis in 1 or more eyes from January 2006 to December 2011. Patients included male and female subjects aged 18 years or older who had been fit with bandage contact lenses as part of their postoperative management. Twenty-two eyes of 15 patients met the criteria for this review. The age range was 30 to 90 years. There were eight men and seven women. The average number of lenses to achieve a successful fit varied from 1 to 8, with an average of 2.22 trial lenses used per patient. By 6 months after the surgery, 12 K-Pro eyes showed visual acuity of 20/200 or better, with 7 of those eyes attaining better than 20/80 best-corrected Snellen distance acuity. Our results show that it is often necessary to use custom contact lenses for K-Pro patients. Management of poor tear film quality, protein deposition, inflammation, lens replacement schedule, and antibiotic resistance are related considerations.

Compliance study of contact lens wearers in Japan, part 1: internet survey of actual circumstances of lens use.

To conduct a survey of contact lens (CL) wearers who use their CLs with satisfaction in Japan and to establish the actual circumstances of CL use. An Internet survey was conducted in 1,000 CL wearers in Japan with questionnaires concerning CL purchase/change, compliance with the duration of wear, and occurrence of complications of CL use. Replies from 636 women (63.6%) and 364 men (36.4%) were received. The largest source of CL purchase was CL specialty stores (eyeglass chains, 41.3%). The most frequent CL types were 2-week frequent replacement (2WFR) soft CLs (SCLs) (32.1%), daily disposable (DD) (31.0%), and other lenses. The main determining factors of purchase were "price" (38.0%), "recommendation of a doctor/staff" (37.6%), and "comfort" (34.1%). The number of wearers who changed their CLs was 372 (37.2%), and the main reasons for change were "inexpensive" (34.9%) and "recommendation of a doctor/staff" (31.2%). In DD and 2WFR/planed replacement SCLs, 270 (42.7%) of 632 wearers were compliant with the recommended duration of use, and the remainder were self-identified as noncompliant. The main reason given for noncompliant behavior was "no harm in extending the duration of use" (60.3%). The number of wearers with eye complications related to lens was 373 (37.3%). The choice of CLs by wearers seems to be price driven rather than being safety focused. Despite being aware of noncompliant behaviors regarding CL use, there were many noncompliant wearers. Clearly, ophthalmologists, optometrists, CL manufacturers, and other CL-related practitioners should cooperate and better educate patients to promote the importance of compliance with safe lens use.

The effect of tinted soft contact lens wear on functional visual acuity and higher-order aberrations

To investigate the differences of functional visual acuity (FVA) and high order aberrations (HOAs) in relation to tinted and clear hydrogel soft contact lens (SCL) wear. A prospective comparative study was performed in 16 eyes of 16 healthy volunteers. Dynamic visual acuity (using a FVA measurement system) and higher-order aberrations (using a wavefront sensor) were compared in subjects wearing two types of soft contact lenses: 1-day Acuvue(®) (Vistakon, Jacksonville, FL) clear and the 1-day Acuvue(®) Define(TM) (Vistakon, Jacksonville, FL) tinted lens. The blink rates were recorded during FVA testing. The correlation between the difference of HOAs and differences in FVA values was analyzed. The mean LogMAR FVA scores with clear and tinted SCLs were 0.07 ± 0.13 and 0.14 ± 0.17 (P<0.05). The mean blink frequencies with clear and tinted SCL wear were 18.4 ± 8.3 and 25.3 ± 4.7 blinks/min (P<0.05). Both 3rd-order aberrations and total HOAs showed statistically significant differences between the two types of soft contact lenses for 6mm pupil measurements (P<0.05). A significant positive linear correlation was observed between ΔHOAs and ΔLogMAR FVA for 6mm pupil measurements (R=0.53, P=0.04). Tinted contact lens wear appears to induce a reduction in optical quality. Functional visual acuity measurement is a useful procedure to study the changes of visual performance and quality in tinted contact lens wear.

Ocular and visual alterations in computer workers contact lens wearers: scoping review

The high number of computer workers wearing contact lenses raises the question whether the sum of these two risk factors for eye health may cause a worsening of Computer Vision Syndrome. The aim of this review is to synthesize the knowledge about ocular and visual alterations related with computer use in contact lens wearers. International review of scientific papers (2003-2013) in Spanish and English, using Scoping Review method, in Medline through PubMed and in Scopus. The initial search provided 114 references, after applying inclusion/exclusion criteria six of them were included. All of them reveal that symptoms when using computer are more prevalent in contact lens wearers, with values of symptoms presentation prevalence ranging from 95.0% to 16.9% in wearers and from 57.5% to 9.9% in non-wearers, and four times more likely to develop dry eye [OR: 4.07 (95% CI: 3.52 to 4.71)]. Computer workers suffer more ocular and visual disturbances if they also are contact lens users, but studies are few and non conclusive. Likewise, further research regarding contact lens type and their conditions of use, both in symptoms and tear quality and ocular surface are needed. Silicone hydrogel lenses are associated with more comfort.

Identification of microorganisms associated with reusable color contact lens trial sets in private eye clinics and offices in Tehran in 2013

Background and Aim: It is of special importance to consider disinfection principles for next use or all types of reusable trial contact lenses; in order to prevent of transferring infectious agents from one patient to another.The aim of this research was to study the rate of observing disinfecting principles forreusable color contact lens trial sets by the practitioners in the optometry and ophthalmology offices and private eye clinics in Tehran. Materials and Methods: In this observational cross-sectional study, 42 eye centers ( including 3 private eye clinics, 14 ophthalmology offices and 25 optometry offices) in Tehran using reusable color contact lens trial sets to present color contact lenses were checked. Sampling were made randomly from the surface of color contact lenses trial set (totally 65 samples obtained). Samples were cultured in standard laboratory conditions and the data were analyzed statistically for “Ratio Comparison Test”; using SPSS software (version 19). Results: In some samples, one type and in some others two types of microorganisms were grown concurrently. In 81.5% of the samples, the bacterial contamination including Escherichia coli, Pseudomonas aeruginosa, Citrobacter, Klebsiella, Proteus, Diphtheroids, and Macrococcus was observed and in 18.5% of the samples, no bacterial contamination was found. Conclusion: Based on the findings, it seems that the present method in using reusable color contact lens trial sets may not be a suitable method. Key Words: Microorganism, Reusable Color Contact Lens trial Sets, Eye Offices and Private eye Clinics, Tehran.

The evolution of tear substitutes: from saline solutions to cationic nanoemulsion

The article defines the milestones of the development of the main types of artificial tears, describes characteristics and benefits of the new tear substitute Cationorm® based on Novasorb® technology: electrostatic mucoadhesion, rapid and optimal spreading, and long time of contact with the ocular surface, favorable action on all tear film layers, osmoregulation, compatibility with different contact lens types, and prolonged clinical efficacy.

Applications of Different Types of Gas-Permeable Contact Lenses in Keratoconus and Their Visual Results

To show applications of different types of gas-permeable contact lenses in patients with keratoconus and to compare visual acuity (VA) results. A total of 229 eyes of 133 patients who used different types of rigid gas-permeable contact lenses between April 2003 and April 2010 at the Cornea and Contact Lens Unit of Eye Clinic 2 of the Ministry of Health, Ulucanlar Eye Training and Research Hospital, were included. Visual acuity of patients was classified as uncorrected and corrected with eyeglasses and corrected with contact lenses. The patients were compared in terms of VA, daily contact lens wear time, and complications. A total of 70 out of 133 (52.6%) patients in our study were male, and 63 (47.4%) were female. The mean age was 25.9 ± 7.03 years (12-45). As for the classification of the 229 eyes included in the study, 136 of 229 (59.4%) eyes had moderate keratoconus, 88 (38.4%) had advanced keratoconus, and 5 (2.2%) had severe keratoconus. Following the contact lens application, the VA in all patients increased when compared to uncorrected and corrected with eyeglasses groups and the difference was statistically significant (p<0.005). When a comparison of different types of contact lenses was made, a statistically significant difference was not found (p>0.5) in terms of increase in VA. When patients were evaluated in terms of contact lens wear times, it was observed that Boston Equalens II was preferred by patients wearing lenses 4-8 hours/day. For patients wearing lenses more than 8 hours a day, Rose K lens was used the most. No serious complication was observed in any of the patients that would lead them to stop wearing contact lenses during the follow-up period. There was also no need for keratoplasty in any patient during the follow-up period. We detected an increase in VA in patients with rigid contact lenses. In addition, some contact lenses were better tolerated by patients and were used for a longer time during the day.

STUDY OF THE OPTICAL POWER OF NANOPHOTONIC SOFT CONTACT LENSES BASED ON POLY (2- HYDROXYETHYL METHACRYLATE) AND FULLERENE

In this paper results of comparative study of the optical power of soft contact lenses (SCL) made of standard material for SCL and nanophotonic materials with different measurement techniques used for the final contact lens controllers are presented. Three types of nanophotonic soft contact lenses were made of standard polymacon material (Soleko SP38TM) incorporated with fullerene C60, fullerol C60(OH)24 and fullerene metformin hydroxylate C60(OH)12(OC4N5H10)12. For the purposes of material characterization for potential application as soft contact lenses, the optical properties of the soft contact lenses were measured by Rotlex and Nidek device. With Rotlex device the following optical results were obtained: optical power and map of defects, while with the Nidek device: optical power, cylinder power and cylinder axis. The obtained values of optical power and map of defects showed that the optical power of synthesized nanophotonic soft contact lens is same to the nominal value, while this was not the case for the standard soft contact lens. Also, the quality of the nanophotonic soft contact lens is better than the standard one. Hence, it is possible to synthesize new nanophotonic soft contact lenses of desired optical characteristics, implying possibilities for their application in this field.

The Role of Microbial Biofilms Consisting on the Contact Lenses in Ocular Infection,Taif, KSA

This study was carried out during 2013, from ophthalmic private clinics, Taif, KSA. All patients understudy were complained from using contact lenses (CLs). Incidence of ocular inflammation due to duration of CLs use, that showed the predominate of ocular inflammation were at 1 st , 2 nd , 3 rd , 4 th , and 5 th days as 37.3, 26.7, 18, 10.7 and 7.3% respectively. Incidence of contact lenses type and inflammation affection, that showed the predominate of cosmetics CLs type were 65.3%, then medical type as 34.7%. The predominate inflammation were in bilateral eyes as 57.3%, then unilateral eye as 42.7% respectively. Incidence of local ocular inflammation signs, that showed the predominate signs of ocular inflammation were redness, lacrimation, itching, F.B. sensation, secretion and edema were 72, 68, 56, 48, 36, and 24% respectively. Incidence of CLs biofilm positive for microbial isolates, total CLs were examined 150, which resulted in 64% positive and 36% negative for microbial isolates respectively. Incidence of CLs biofilm microbial isolates types and species, total CLs were examined 96. The bacteria, fungus and protozoa were resulted in 70.8, 20.9, and 8.3% respectively. The predominant isolates were Pseudomonas aeruginosa, Serratia marcescens, Staph. aureus, Fusarium spp., Staph. epidermidis, Candida albicans, Acanthamoeba keratitis and Strept. spp., as percentage 22.9, 16.7, 14.6, 11.5, 10.4, 9.4, 8.3 and 6.2% respectively.

Wide-angle viewing system.

A wide-angle viewing system offers a panoramic view of the surgical field and also improves the safety and efficacy of the vitreoretinal surgical procedure. Surgeons can easily observe the fundus in almost the whole area and evaluate the retinal pathologies through the panoramic view even in eyes with small pupils, corneal opacity, or eyes implanted with multifocal intraocular lens or toric intraocular lens. Recent wide-angle viewing systems consist of two types: contact lens and non-contact lens. The benefit of the contact lens type is better resolution and contrast of the fundus image compared to the non-contact lens type. The contact lens is directly attached to the cornea and the aberration and the reflection from the corneal surface are canceled. However, the eye position needs to be fixed and surgical procedures that rotate the eye should be avoided because incomplete attachment of the contact lens causes decreased visibility of the fundus image. The benefit of the non-contact lens type is that the viewing angle can be changed by moving the front lens up and down to adjust the distance between the cornea and the front lens. The surgical procedures are more flexible and the eye can be rotated. Dehydration of the corneal surface decreases the visibility of the fundus image and the corneal surface needs to be covered with viscoelastic material to avoid dehydration. Condensation of the front lens also decreases the visibility of fundus. Understanding the optical characteristics of the wide-angle viewing system is the key to a successful vitreoretinal surgery.

Reducing dropout of contact lens wear with Biotrue multipurpose solution

PurposeTo evaluate whether the use of Biotrue multipurpose solution (MPS) could significantly reduce the likelihood with which patients drop out of using daily wear contact lenses (CLs) amongst 18–44-year-old frequent replacement CL wearers.MethodsDaily wear CL subjects habitually using MPSs (other than Biotrue MPS) who reported an intent to imminently drop out of CL wear because of comfort and dryness complaints were recruited to participate in this investigation. Subjects were switched to Biotrue MPS and continued to use habitual CL types with the new MPS for 2 weeks. Subjects completed an online satisfaction questionnaire at baseline and after 2 weeks to assess the change in symptoms and the intent to drop out of CL wear. Six months after completion of the initial study, a follow-up survey was administered to a subset of the initial participants.ResultsA total of 153 daily wear (silicone hydrogel and hydrogel) subjects completed this 2-week study with Biotrue MPS. When measuring those with the highest propensity to drop out of lens wear (n=93) after switching to Biotrue MPS, 90% of subjects significantly reduced their likelihood of dropping out of CL wear (P<0.0001). Online interviews were conducted with 73 of the study participants 6 months after completion of the initial study. A total of 93% of participants responded that they were still wearing CLs at least once per week. Of the 7% of respondents who were not currently wearing lenses 6 months after the initial study, two had dropped out of lens wear completely, and three still wore lenses less than once per week.ConclusionPatients intending to drop out of CL wear due to discomfort and dryness significantly reduced their propensity of discontinuing lens wear following use of Biotrue MPS. Six months after completion of the study, 93% of patients were still wearing CLs at least once per week.

Progression of keratoconus in patients wearing pancorneal toric edge rigid gas-permeable contact lenses

To investigate the rate of progression of keratoconus in patients wearing pancorneal toric edge rigid gas-permeable contact lenses (pancorneal RGP-CL) compared to non-pancorneal RGP-CL. We also evaluated alterations in anterior chamber parameters with the progression of keratoconus and investigated the location of the cone in eyes with keratoconus. The current study was a retrospective study including patients with clinically evident keratoconus from the outpatient clinic from the Department of Ophthalmology of the Erasmus Medical Center, Rotterdam, the Netherlands. Medical history and contact lens characteristics were documented. All participants underwent ophthalmic examination including corneal topography. Corneal topography was repeated at one of the consecutive visits of the patient. Patients were divided into two groups: those wearing pancorneal RGP-CL and those wearing other contact lens types. As a measure of progression of keratoconus differences in corneal topography parameters between both groups were compared. A total of 82 patients were included of which 42 had follow-up (mean 17.8 months) data. We found a significant difference in progression between eyes fitted with and without pancorneal RGP-CL (K-flat: p=0.09, K-steep: p=0.02, K-mean: p=0.02, and K-minimum: p=0.04). Compared with eyes fitted without pancorneal RGP-CL no significant difference in K-values was found for eyes fitted with pancorneal RGP-CL during follow-up. Furthermore, a significant decrease in anterior chamber volume (p<0.001) and corneal volume (p=0.008) was found during follow-up. In 86.6% the location of the cone was located infero-temporal. Pancorneal RGP-CL have a better effect on stabilizing progression of keratoconus than non-pancorneal RGP-CL. The finding of an infero-temporal location of the cone in keratoconic corneas may improve results of contact lens fitting and surgical management.

Influence of specimen thickness on the nanoindentation of hydrogels: Measuring the mechanical properties of soft contact lenses

Nanoindentation offers a convenient method for the testing of thin hydrogel specimens, such as contact lenses, to directly assess their mechanical properties. Here we investigate the mechanical properties of poly(hydroxyethyl methacrylate) (pHEMA) specimens of a range of uniform thickness values and demonstrate that, with 50 and 100μm radius spherical indenters, a significant increase in apparent elastic modulus is seen when the specimen thickness is smaller than 500μm at indentation depths <1μm. This is a manifestation of the well known indentation thickness effect but occurring at larger critical thicknesses than seen with other materials. A simple empirical relation is determined for the variation in apparent elastic modulus with normalised thickness. The empirical thickness correction function obtained from pHEMA specimens was subsequently used to correct for the thickness variation within a range of contact lenses supplied by a number of different manufacturers fabricated from both pHEMA and silicone polymers, with a range of optical strengths and hence thickness profiles. The correction function is seen to compensate for the variation in apparent elastic modulus with lens thickness for all four contact lens types, irrespective of lens material. The measured Young's modulus of the contact lens material, corrected for thickness, was compared with that quoted by the manufacturers of the contact lenses, obtained by conventional bulk mechanical testing, to find good agreement.

Contact lens related keratitis: Acute presentation and management options: The Manchester Royal Eye Hospital Acute Services experience

A prospective study on the initial assessment and further management of patients with Contact Lens related keratitis presenting to the Acute Services at Manchester Royal Eye Hospital.. Other points which will be highlighted are 1.Referral protocols when a patient with Contact lens related keratitis presents to an optometrist 2.How soon would a patient with contact lens related keratitis need to be seen by an ophthalmologist 3.Initial assessment and further management. 4.What type of contact lens related keratitis are referred to a corneal subspecialist 5.What type of contact lenses is more likely to cause contact lens related keratitis according to The Manchester Royal Eye Hospital Experience. 6.How long does it usually take for full resolution 7.Best advice to patients to try and avoid contact lens related keratitis

The use of contact lenses following intra-ocular lens (IOL) implantation in infants born with congenital cataracts

Purpose: Congenital cataracts are a major cause of childhood blindness due to deprivation amblyopia leading to loss of visual function and lifelong visual impairment. Advances in surgical techniques mean that infants can be fitted with an IOL at the time of cataract removal, ideally less than 10 weeks of age. They tend to be left hypermetropic to allow for axial elongation. This residual hypermetropia can be managed successfully with contact lenses, particularly useful in unilateral cataract. This retrospective audit aimed to determine the type and parameters of contact lenses used to achieve optimum fitting together with the length of time lenses were required dependent upon the rate of myopic shift.

Objective and subjective visual performance of multifocal contact lenses: Pilot study

The aim of the present study was to compare the objective and subjective visual performance of three different soft multifocal contact lenses. 10 subjects (habitual soft contact lens wearers) between the ages of 40 and 45 years participated in the study. Three different multifocal silicone hydrogel contact lenses (Acuvue Oasys, Air Optix and Biofinity) were fit within the same visit. All the lenses were fit according to the manufacturers' recommendation using the respective fitting guide. Visual performance tests included low and high contrast distance and near visual acuity, contrast sensitivity, range of clear vision and through-focus curve. Objective visual performance tests included measurement of open field accommodative response at different defocus levels and optical aberrations at different viewing distances. Accommodative response was not significantly different between the three types of multifocal contact lenses at each of the accommodative stimulus levels (p>0.05). Accommodative lag increased for higher stimulus levels for all 3 types of contact lenses. Ocular aberrations were not significantly different between these 3 contact lens designs at each of the different viewing distances (p>0.05). In addition, optical aberrations did not significantly differ between different viewing distances for any of these lenses (p>0.05). ANOVA revealed no significant difference in high and low contrast distance visual acuity as well as near visual acuity and contrast sensitivity function between the 3 multifocal contact lenses and spectacles (p>0.05). There was no statistically significant difference in accommodative response, optical aberrations or visual performance between the 3 multifocal contact lenses in early presbyopes.

Comparing the Optical Properties of Soft Contact Lenses On and Off the Eye

The purpose of the current study was to examine the on- and off-eye optical performance of two types of soft contact lenses (hydrogel and silicone hydrogel). The monochromatic aberrations (λ = 850 nm) of contact lenses were measured on-eye using a clinical Shack-Hartmann ocular aberrometer. In addition, we used an off-eye single-pass contact lens aberrometer (λ = 540 nm) in which the soft contact lens was placed within a wet cell. Comparison of the lower and higher order aberrations measured with these two methods required compensation for different wavelengths and knowledge of the refractive index of the contact lens materials. The measured on-eye sphere and spherical aberration values were generally similar to those measured off-eye and those specified by the lens manufacturers for both types of soft contact lenses. However, there were notable differences, especially for high plus-powered lenses, which typically exhibited lower sphere power on the eye than expected from the lens specifications and from the off-eye measured powers, both of which were almost identical. Longitudinal spherical aberration varied with lens power in the hydrogel lenses, as expected from geometric optics theory. Longitudinal spherical aberration measurements on- and off-eye, however, deviated significantly from that expected of a thin lens with spherical surfaces due to surface asphericities. The difference between on- and off-eye optics can be modeled as a tear lens or as relative lens thickness changes caused by lens flexure. The results of the current study reveal that the major difference between the on-eye lens optics and the manufacturers' specifications is not due to lens errors but due to eye-lens interactions, which could be either lens flexure or a tear lens forming behind the soft contact lens.