Rigid Gas Permeable Lens Wear Research Articles

LENS CARE COMPLIANCE RATES AND PERCEPTIONS AMONG RIGID GAS PERMEABLE CONTACT LENS WEARERS - A PILOT STUDY.

The aim was to estimate compliance rate among rigid gas permeable lens wearers (RGPLW) in lens system care, identify procedures in lens care process with poorest compliance levels, and assess concordance between participant reported practices and their subjectively perceived compliance. The study included outpatient RGPLW managed at Zagreb University Hospital Center in Zagreb, Croatia. They filled out a questionnaire that included demographic data, duration of lens wear, self-evaluation compliance grade, and 14 lens care procedures and wearing habits indicative of compliance. There were 50 patients (mean age 34.6 years, 68% female). Full compliance was found in a single patient. The mean number of non-compliant procedures was 5.48, with 32% of participants non-compliant in more than 50% of the compliance criteria. Critical procedures of the lens care process were infrequent lens case exchange (74%), using tap water for lens (70%), and improper case cleaning (68%). The mean lens case replacement time was 9.8 months (SD 6.76), with only 26% of patients replacing lens case at least once in 3 months. Excessive daily lens wear was associated with greater total number of non-compliant procedures (p<0.0008). RGPLW were aware of their inappropriate lens care only when achieved non-compliance in almost 50% of the procedures. In conclusion, lens wearers were not aware of their extremely low compliance rate in several aspects of lens and lens case maintenance. Study results indicated the key procedures the practitioners should focus on when evaluating subjective and objective compliance and reinforcing care and hygiene education of RGPLW.

Effect of spherical rigid gas permeable lens on correction of corneal astigmatism

Background: Objectives were to study an effect of spherical RGP (rigid gas permeable) contact lens in correcting high corneal astigmatism more than 3 diopter.Methods: Total 48 eyes with corneal astigmatism greater than 3.00 diopter were included in study. At the first visit, routine preliminary examination, parameter assessment and subjective refraction has been carried out followed by patient counselling for RGP lens wear. Based on the corneal parameters considering keratometry as well as corneal topography, RGP lens trial was done. Post adaptation period, lens fitting analysis was done by understanding Fluorescein pattern with slit lamp and over refraction was done. Final lens has been ordered on this basis with understanding of tear lens formed, lens performance on cornea and edge width minimal of 0.80 mm to 1.00 mm. Patients were assessed at an interval of every two months from a date of lens dispensing.Results: The spherical RGP lens did correct the corneal astigmatism of more than 3D by formation of tear lens between cornea and lens. Vision improved by 2 to 3 lines compared to the spectacle correction without compromising corneal integrity at the central or peripheral cornea. Keratoconic eye showed significant vision improvement without the use of toric lens.Conclusions: Astigmatic eyes showed significant improvement in acuity with spherical RGP lens without compromising corneal integrity.

Short-term changes in topometric indices after discontinuation of rigid gas permeable lens wear in keratoconic eyes.

Purpose:To estimate the time taken for topometric indices to stabilize in keratoconic corneas following cessation of habitual RGP contact lens wear.Methods:A total of 29 eyes of 20 patients, diagnosed with mild to severe keratoconus were included in this prospective observational study. All patients were experienced RGP contact lens wearers (either conventional RGP or Rose K2 lens) with each patient having used these lenses for at least a year. Corneal topography was performed immediately following discontinuation of habitual contact lens wear at baseline and each of four consecutive visits, 1-week apart.Results:An overall reduction in the keratometry and thickness values were noted on tomography immediately following cessation of contact lens wear and these indices increased significantly in the 1st week (P < 0.001). Consecutive visits following the first visit did not show any significant change in the topometric parameters (P > 0.05). Subgroup analysis revealed a similar trend in eyes with “severe” keratoconus and in eyes fitted with the “three-point touch” philosophy. However, eyes with “mild-moderate” keratoconus and those fitted with “apical clearance” fitting philosophy showed marginal differences even within the 1-week period of lens cessation.Conclusion:Maximum changes in keratometry and pachymetry values following discontinuation of RGP lens wear stabilize within the 1st week of cessation of rigid lens wear in a keratoconic cornea. These changes were more pronounced in patients with severe keratoconus and those with an apical bearing fit. This information would be useful for practitioners to assess the progression of keratoconus in RGP lens users before collagen cross-linking.

Tomographic and Refractive Characteristics of Pediatric First-Degree Relatives of Keratoconus Patients

To evaluate the tomographic and refractive characteristics of pediatric first-degree relatives of patients with keratoconus. Cross-sectional study. Setting: Department of Ophthalmology at the American University of Beirut Medical, Beirut, Lebanon. Pediatric first-degree relatives of patients with keratoconus. Both eyes of all participants aged between 6 and 18 years were included and studied. Soft contact lens use in the past 2weeks or rigid gas-permeable lens wear within 4weeks, history of prior ocular surgery or infectious keratitis, and unreliable corneal tomography. Masking and Randomization: Two masked cornea and refractive surgeons of different training backgrounds independently evaluated the participants' tomographic outputs. Additionally, the tomographic data were analyzed using Smadja's decision tree. Scheimpflug tomography, manifest refraction, and slit-lamp examination. Anterior curvature indices, posterior elevation values, thinnest pachymetry, and subjective and objective tomographic interpretation. One hundred eighty-three subjects were recruited. Tomographic evaluation after Cohen's kappa coefficient analysis revealed 32 patients as having keratoconus (17.5%), while 35 patients (19.1%) were labeled as keratoconus by objective analysis. There were 11.5%-15.5% of patients with keratoconus aged less than 11 years, 18.0% aged 12-15 years, and 25.5% aged 16-18 years. Their respective steepest anterior curvature and thinnest pachymetry are 44.8 ± 6.5 diopters (D) and 515.9 ± 39.2μm, 47.34 ± 3.4 D and 496.1 ± 37.9μm, and 49.7 ± 6.1 D and 486.0 ± 66.5μm. A total of 37.5% of the keratoconus patients were unilateral as evaluated by tomography alone. The prevalence of keratoconus in pediatric first-degree relatives of diagnosed keratoconus patients is high. Screening in this high-risk group is warranted.

Patient-related barriers to Rigid Gas Permeable (RGP) lens wear among keratoconus patients in Jordan.

To assess potential patient-related barriers to rigid gas permeable (RGP) lens wear for vision rehabilitation in a sample of keratoconus (KC) patients in Jordan. Barriers for RGP contact lens wear among KC patients were discussed and specified by a focus group which consisted of five optometrists who are involved in contact lens practice. The focus group addressed potential barriers for RGP lens wear from the patient's perspective. The identified barriers were then used to design the final questionnaire used in the study. The questionnaire consisted of 8 questions which ask the participant to rate, within a 5-points scale (1: strongly disagree to 5: strongly agree), how each suggested item is considered a barrier for RGP lens wear. 204 KC patients (86 females, 118 males) were involved in a semi-structured interview to answer the questionnaire. The average age of participants was 30.85 (±8.74) years old and ranged from 18 to 62 years. The average age of diagnosis of KC (±standard deviation) is 21.96 (±7.22) years old with a range of 12-52 years. All participants reported that they had never tried RGP lenses for their vision rehabilitation; however, other management options were reported such as glasses, keratoplasty, collagen cross linking and Intacs. The mean score of total barriers to RGP wear was high at 3.8 (±0.4) (out of 5). The major identified barriers were: lack of awareness of the benefits of RGP lenses, fear of possible lens complications, lack of medical insurance and high cost of the lens. The study reveals that several barriers were identified as prevalent. Consequently, there is an imperative need to adopt better planning strategies for management protocol of KC in order to assure best eye care service for KC patients in Jordan.

An observational cross-sectional study on the corneal endothelium of medium-term rigid gas permeable contact lens wearers.

To assess if polymegethism and pleomorphism were evident in corneal endothelium after medium-term rigid gas permeable (RGP) contact lens wear. In a cross-sectional observational study over 12 years, single images of the central region of the corneal endothelium of one eye of 46 subjects were taken with a non-contact specular microscope, along with a measure of central corneal thickness (CCT). The images were printed onto A3-sized paper and 100 cells/image measured by planimetry. Subjects aged between 20 and 32 years, with an average cumulative RGP wear of 6.0+/- 1.6 years (range 3-9 years) were assessed; 26 of the subjects were Caucasian and 20 were Asian. The mean CCT was 0.515+/- 0.027mm. The group cell area value was 401+/- 42 sq micron to give an estimated endothelial cell density (ECD) of 2520+/- 273 cells/sq mm. As compared to a historical database, most endothelia (37/46) showed some changes with the mean coefficient of variation on cell area (COV) being 36.7+/- 8.0% and the percentage of 6-sided (HEX) being 51.8+/- 8.8%. There were modest correlations between years of RGP wear and both COV (p=0.009, r spearman=0.424) and HEX (p=0.025, r spearman=-0.291), but not for ECD or CCT. Corneal endothelial polymegethism appears to be a commonplace consequence of RGP lens wear with the magnitude of the change being related to the cumulative duration of the lens wear.

Are scleral lenses safe for the meibomian gland?

SummaryNowadays, we are experiencing scleral lens rebirth through the development of new designs and materials respecting the anterior ocular surface represented by the cornea, the limbus and the anterior bulbar conjunctiva. But what about the posterior ocular surface, represented by the tarsal conjunctiva, the lid margin and meibomian glands? The interaction of the scleral lens with the posterior ocular surface will be assessed clinically in keratoconus patients wearing scleral lens for more than 2 years and compared in a randomized manner with soft lens, hybrid lens and corneal rigid gas permeable lens wearers and with control sample. Lid wiper epitheliopathy grade, tear film break up time, quality of meibum and meibomian gland trophicity will be compared between different groups…

Corneal aberration changes after rigid gas permeable contact lens wear in keratokonic patients

PurposeTo determine the short-term effect of rigid gas permeable (RGP) contact lenses on corneal aberrations in keratoconic patients. MethodSixteen keratoconic eyes with no history of RGP lens wear were included. They all had corneal aberrometry using Pentacam, and different aberration indices of the anterior and posterior surfaces of the cornea were measured before and 3 months after fitting RGP lenses. The effect of baseline parameters on these changes was tested in univariate and multiple models. ResultsTotal aberrations and individual Zernike coefficients did not show statistically significant changes after using RGP lenses. Although not statistically significant, vertical coma decreased in the anterior (p = 0.073) and posterior surface (p = 0.095). Relationships that remained statistically significant in the multiple model were between baseline central corneal thickness and changes in total higher order aberrations and anterior 4th order astigmatism 0°, and between baseline 2nd order astigmatism 45° and its changes. ConclusionIn this study, corneal aberrations remained unchanged 3 months after wearing RGP contact lens. Further studies with sufficient samples in different groups of keratoconus severity or baseline aberrations are needed to obtain more accurate results.

The influence of rigid gas permeable lens wear on the concentrations of dinucleotides in tears and the effect on dry eye signs and symptoms in keratoconus.

To evaluate the signs and symptoms of dry eye and dinucleotide secretion in tears of keratoconus patients (KC) and the potential effect of rigid gas permeable (RGP) contact lens wear. Twenty-three KC patients and forty control subjects were enrolled in this study. Signs of dry eye including tear volume, tear stability and corneal staining along with symptoms were assessed using the McMonnies questionnaire. Tears were collected using Schirmer strips, and dinucleotide concentrations in collected tears measured using high pressure liquid chromatography. Values obtained in KC and controls were compared. The effect of contact lens wear in KC was also assessed. KC eyes showed a significantly lower tear volume compared to controls, shorter tear break up time (TBUT), higher corneal staining and higher McMonnies dry eye questionnaire scores (p<0.05). When compared with non-wearers, KC contact lens wearers showed significantly higher symptoms, lower Schirmer and TBUT values (p<0.05). Concentration of Ap4A (0.695±0.304μM vs. 0.185±0.178μM) and Ap5A (0.132±0.128μM vs. 0.045±0.036μM) were higher in KC compared to controls (p<0.001) and only Ap4A was statistically higher in RGP wearers compared to non-wearers (0.794±0.478μM vs. 0.417±0.313μM) (p<0.05). Signs and symptoms of dry eye as well as concentrations of Ap4A and Ap5A were markedly increased in KC patients compared to controls. Moreover, Ap4A and symptoms of dry eye were statistically higher in RGP wearers compared to non-wearers. This seems to indicate that factors such as RGP contact lens wear might exacerbate the clinical condition of dry eye.

Symptoms and Signs in Rigid Gas Permeable Lens Wearers During Adaptation Period

To evaluate neophyte contact lens wearers' fitting to rigid gas permeable (RGP) contact lenses in terms of wearing time, tear volume, stability, corneal staining, and subjective ratings, over a 1-month period of time. Twenty-two young healthy subjects were enrolled for wearing RGP on a daily wear basis. The participants included in this study never wore contact lenses and showed a value under 10 in McMonnies Questionnaire. Contact Lens Dry Eye Questionnaire, Visual Analog Scales, Schirmer test, tear film break-up time (BUT), and corneal staining grading were performed. Follow-up visits were scheduled at 1, 7, 15, and 28 days. Six subjects dropped out due to discomfort from the study before 1 month (27% of discontinuation rate). Successful RGP wearers (16 participants) achieved high levels of subjective vision and reported comfort scores of approximately 9 of 10 between 10 and 15 days. They reported wearing their lenses for an average of 10.12±2.43 hr after 1 month of wear. Conversely, unsuccessful wearers discontinued wearing the lenses after the first 10 to 15 days, showing comfort scores and wearing time significantly lower compared with the first day of wear. Schirmer test showed a significant increase at 10 days (P<0.001), and the BUT trends decreased after the first week of wear in unsuccessful group. Symptomatology related with dryness and discomfort, detected during the first 10 days of the adaptation, may help the clinician to predict those participants who will potentially fail to adapt to RGP lens wear.

Comparison of Changes in Ocular Surface Status after Wearing Orthokeratologic and Rigid Gas Permeable Lens

Purpose: To evaluate the differences in dry eye and meibomian gland dysfunction (MGD) by comparing ocular surface status before and after wearing an orthokeratologic (OK) lens and rigid gas permeable (RGP) lens made of the same material. Methods: The ocular surface and meibomian gland statuses of 12 eyes of 12 OK lens wearers (OK lens group) and 16 eyes of 16 RGP wearers (RGP lens group) were evaluated before and 1 and 3 months after lens wearing. Ocular surface disease index (OSDI), tear film break-up time (TBUT), Schirmer’s test I, and ocular surface staining score were evaluated for ocular surface parameters. Meibomian gland function was evaluated by assessing lid margin abnormality, meibomian gland expressibility, and meibum quality. Results: TBUT and ocular surface staining score after 1 and 3 months of wearing an OK lens were significantly aggravated (p = 0.004, p < 0.001). The MGD grade, lid margin abnormality, meibomian gland expressibility, and meibum quality were aggravated after 1 and 3 months of wearing an OK lens (p < 0.001, p < 0.001, p < 0.001, p = 0.002). After 1 and 3 months of wearing an RGP lens, OSDI, TBUT, and ocular surface staining score were aggravated (all p < 0.001). The MGD grade, lid margin abnormality, meibomian gland expressibility, and meibum quality were aggravated after 1 and 3 months of wearing an RGP lens (all p < 0.001). MGD grade, lid margin abnormality, meibomian gland expressibility, and meibum quality were significantly more aggravated in the RGP lens group than in the OK lens group after 3 months (p < 0.001, p < 0.001, p = 0.001, p < 0.001). Conclusions: Use of OK and RGP lenses affects ocular surface status. Especially, meibomian gland parameters and OSDI showed greater changes in RGP lens wearers than OK lens wearers. J Korean Ophthalmol Soc 2016;57(4):546-554

Contrast Sensitivity Function after Correcting Residual Wavefront Aberrations during RGP Lens Wear

To investigate the effect on the contrast sensitivity function (CSF) of correcting the residual wavefront aberrations in myopic and keratoconic subjects wearing rigid gas permeable (RGP) contact lenses. Seventeen eyes of 16 myopic subjects and 20 eyes of 19 keratoconic subjects were included in this study. All eyes were habitually corrected with RGP lenses. The residual aberrations of the RGP lens-wearing eyes were compensated by an adaptive optics (AO) system. The contrast sensitivities were measured through a 4-mm artificial pupil at spatial frequencies of 2, 4, 8, 16, and 32 cycles per degree (cpd) during RGP lens wear for the myopic and keratoconic groups, respectively. The CSF measurements were repeated with and without AO correction. Comparisons of contrast sensitivity at all spatial frequencies with and without AO correction were performed respectively for the myopic and keratoconic groups during RGP lens wear. In the myopic RGP lens-wearing group, the differences in contrast sensitivity at each spatial frequency, with and without AO correction, were not significant (all p values > 0.05). In the keratoconic RGP lens-wearing group, the contrast sensitivities at all spatial frequencies with AO correction were higher than those without AO correction, but differences only at the low (2 cpd) and intermediate (4, 8, and 16 cpd) spatial frequencies were significant (p = 0.039, 0.005, 0.001, and 0.007). The residual aberrations significantly reduced the contrast sensitivities at low and intermediate spatial frequencies for keratoconic RGP lens-wearing eyes but did not have any effect on the CSF for the myopic RGP lens-wearing eyes. Developing techniques that could more completely correct the wavefront aberrations may improve visual performance in keratoconus.

Changes in Diadenosine Polyphosphates during Alignment-Fit and Orthokeratology Rigid Gas Permeable Lens Wear

To evaluate the levels of dinucleotides diadenosine tetraphosphate (Ap(4)A) and diadenosine pentaphosphate (Ap(5)A) in tears of patients wearing rigid gas permeable (RGP) contact lenses on a daily wear basis and of patients wearing reverse-geometry RGP lenses overnight for orthokeratology treatment. Twenty-two young volunteers (10 females, 12 males; 23.47 ± 4.49 years) were fitted with an alignment-fit RGP lens (paflufocon B) for a month, and after a 15-day washout period they were fitted with reverse-geometry RGP lenses for corneal reshaping (paflufocon D) for another month. During each period, tears were collected at baseline day 1, 7, 15, and 28. Ap(4)A and Ap(5)A were measured by high-pressure liquid chromatography (HPLC). Additionally, corneal staining, break-up time (BUT), Schirmer test, and dryness symptoms were evaluated. Ap(4)A concentrations increased significantly from baseline during the whole period of daily wear of RGP lenses (P < 0.001); concentration was also significantly higher than in the orthokeratology group, which remained at baseline levels during the study period except at day 1 (P < 0.001) and day 28 (P = 0.041). While BUT and Schirmer remained unchanged in both groups, discomfort and dryness were significantly increased during alignment-fit RGP daily wear but not during the orthokeratology period. Daily wear of RGP lenses increased the levels of Ap(4)A due to mechanical stimulation by blinking of the corneal epithelium, and this is associated with discomfort. Also, orthokeratology did not produce symptoms or signs of ocular dryness, which could be a potential advantage over soft contact lenses in terms of contact lens-induced dryness.

Changes in Refraction, Ocular Aberrations, and Corneal Structure After Suspending Rigid Gas-Permeable Contact Lens Wear in Keratoconus

This study reports on changes in visual acuity, ocular higher-order aberrations, and refraction after suspending rigid gas-permeable lens wear for 1 week in 15 patients with moderate to severe keratoconus. Alterations in the anterior surface, central corneal powers and axes, and central corneal thickness were also explored. Scheimpflug photography and Hartmann-Shack aberrometry were performed at 2 visits, 7 days apart, after the patients had removed their habitual contact lenses. Subjective refraction and both high- and low-contrast logarithm of the minimum angle of resolution visual acuities were also recorded at both visits. Reductions in both high-contrast visual acuity (P = 0.001) and low-contrast visual acuity (P = 0.002), along with an increase in third-order root mean square aberrations (P = 0.008), occurred after rigid gas-permeable lens wear was suspended in these patients with keratoconus. However, no significant changes in subjective refraction were found over the 1-week period (P ≥ 0.10). Significant correlations were observed between third-order coma root mean square aberrations and the measured high-contrast (r(p) ≥ 0.59; P ≤ 0.02) and low-contrast visual acuities (r(P) ≥ 0.61; P ≤ 0.015). In addition to increases in the anterior surface central corneal powers (P ≤ 0.02), a reduction in central corneal thickness also was found between the 2 visits (P = 0.00016). Changes in the optical and structural parameters of the keratoconic cornea occur after suspending rigid gas-permeable contact lens wear. This information may be of interest to practitioners concerned with prescribing aberration-controlling soft contact lenses for such patients.

Visual performance and optical quality with soft lenses in keratoconus patients

To assess visual performance and ocular aberrations in keratoconic patients using toric soft contact lenses (SCL), rigid-gas-permeable (RGP) contact lenses and spectacle lens correction. Twenty-two keratoconus patients (16 RGP lens wearers and six spectacle wearers) were fitted with toric SCL. Ocular aberrations were measured with and without the patient's habitual RGP lenses and with the SCL in place. In the spectacle wearers, aberrations were measured with and without the SCL. Visual performance (high- and low-contrast visual acuity) was evaluated with the patient's habitual correction and with the SCL. In the RGP lens wearers both the habitual lenses and the toric SCL significantly reduced coma, trefoil, 3rd-order, 4th-order cylinder and higher-order root-mean-square (RMS) aberrations (p ≤ 0.015). In the spectacle wearers the toric SCL significantly reduced coma, 3rd-order and higher-order RMS aberrations (p ≤ 0.01). The patients' habitual RGP lenses gave better low-contrast acuity (p ≤ 0.006) compared to the toric SCL; however, no significant difference was found between lens types for high-contrast acuity (p = 0.10). In the spectacle wearers no significant differences in visual performance measurements were found between the patients' spectacles and the toric SCL (p ≥ 0.06). The results show that RGP lenses provided superior visual performances and greater reduction of 3rd-order aberrations compared to toric SCL in this group of keratoconic patients. In the spectacle-wearing group, visual performance with the toric SCL was found to be comparable to that measured with spectacles. Nevertheless, with the exception of spherical aberration, the toric SCL were successful in significantly reducing uncorrected higher-order aberrations.

Confocal Microscopic Observations of Stromal Keratocytes in Soft and Rigid Contact Lens Wearers

To determine the density of corneal stromal cells in wearers of soft contact lenses (SCLs) and rigid gas-permeable (RGP) contact lenses (CLs). The keratocyte density (KD) was measured at different depths of the stroma by confocal microscopy. In study 1, 32 wearers of rigid gas-permeable (RGP) lenses and 30 wearers of SCLs were studied. Forty volunteers with no history of CL wear were studied as controls. In study 2, 16 volunteers with no history of CL wear were divided into 2 groups; 7 subjects wore RGP lenses (oxygen transmissibility, Dk/L, 35) and 9 subjects wore SCLs (Dk/L, 34). All subjects were asked to wear the CLs daily for 6 months. In study 1, the KDs in the anterior stroma (AST) and the posterior stroma (PST) of the cornea were significantly lower in the RGP lens group than in the control group. The KD in the SCL group was significantly lower at all depths of the cornea than that of the control group. In study 2, the KD in the AST of the RGP lens group was significantly lower after 1 month of CL wear. The KD in the AST and PST of the SCL group was decreased significantly at 1 month, and all layers were decreased by 10% to 20% 6 months after wearing CLs. At 5 weeks after discontinuation of SCL wear, the KD in all layers was not significantly different from that at the baseline. The change in the KD was greater in CL wearers than in volunteers with no history of CL wear and also greater in SCL wearers than in RGP lens wearers. Analysis of the KD by confocal microscopy may be a useful method for evaluating the effect of CL wear.

Corneal Changes After Suspending Contact Lens Wear in Early Pellucid Marginal Corneal Degeneration and Moderate Keratoconus

This case study reports on how refraction, visual acuity, and ocular higher-order aberrations changed after rigid gas-permeable (RGP) lens wear was suspended by a patient with early pellucid marginal corneal degeneration (PMD) and by a patient with moderate keratoconus. Alterations in central corneal power and axes, central corneal thickness, and corneal topography were also explored. Ocular aberrations and Scheimpflug photography were measured at 2 visits, 7 days apart, after the patients had removed their contact lenses. Subjective refraction and logarithm of the minimum angle of resolution visual acuities were also recorded at both visits. In contrast to the keratoconic patient, the patient with early PMD showed changes in subjective refraction (approximately -1.75 diopter cylinder of astigmatism), front surface central powers (∼1.3 diopter [D] horizontally and 2 D vertically), and anterior surface topography (∼1.2 D) between visits. Both patients showed an increase in total higher-order root mean square (HORMS) aberrations after suspending lens wear (∼0.40 μm for the moderately keratoconic patient and 0.22 μm for the early PMD patient). Changes in the optical and structural parameters of the cornea after suspending lens wear are likely to be dependent on a multitude of factors, such as the lens fitting and the biomechanical properties of the cornea. The findings of this report may be useful to practitioners when refracting or refitting existing RGP lens wearers with ectasia or to those involved in prescribing aberration-controlling contact lenses for conditions such as keratoconus and PMD.

Postmarket Surveillance of Menicon Z Rigid Gas-Permeable Contact Lenses for up to 30 Days Continuous Wear in the United States

To evaluate the incidence of microbial keratitis associated with the use of the Menicon Z rigid gas-permeable (RGP) contact lenses (CLs) for up to 30 days continuous wear (CW). For this study, CW was defined as wearing CLs in an extended-wear modality with an average wearing time of 22 days or more. Microbial keratitis was the sole endpoint of the study safety evaluation. Subjects who were interested in RGP lens CW were recruited for the study through 33 investigational practices. To be eligible for the study, subjects must have worn the Menicon Z lens for CW for at least 1.5 months with an average CW time of 22 days or more. Eligible wearers were then contacted at 6-month intervals for up to 24 months after enrollment to determine their typical wearing schedules and continuance of wear and to detect any problems that would be indicative of microbial keratitis. Discontinuation from the study was defined as a discontinuation of contact with or CL wear by the study participants. Study volunteers could be discontinued from the study at 6, 12, 18, or 24 months if they could not be contacted (lost to follow-up); if they were not wearing their CL for CW; or at their own request. Wearing time data collected for individuals discontinued from the study was included in the wearing time analysis. The study population included 507 participants, of whom 173 had discontinued by the end of study at 24 months. Lack of 22 days or more of CW was the most frequently cited reason for discontinuation and accounted for 121 of the 173 subject discontinuations. Lost to follow-up, study participant choice, and other reasons accounted for the remaining 52 subject discontinuations. Of the reported wearing times over the duration of the study, 1,275 of the 1,527 contacts resulted in reported wearing times of 22 days or more of CW. There were no findings of microbial keratitis during the study. Overall, there was a low reported rate of complications for the enrolled study participants. On the basis of this study, CW of the Menicon Z hyper-Dk/t RGP lens provides a safe and full-time vision correction alternative for patients who can adapt to RGP lens wear.

Effect of contact lenses on the protein composition in tear film: a ProteinChip study

The aim of this study was to analyze and compare the effects of rigid gas permeable and soft contact lenses on the protein composition in the tear film of contact lens wearers. Wearers of soft contact lenses (CL_S, n = 13) and rigid gas permeable contact lenses (CL_H, n = 13) were recruited for this study. Thirteen non-contact lens wearers were also included as the control. Tears were collected using Schirmer strips and frozen until use. The tears were eluted and analyzed on ProteinChips SELDI-TOF (surface-enhanced laser desorption and ionization in time of flight mass spectrometry; Bio-Rad, USA) with different chromatographic surfaces (cationic and anionic exchanger and reversed phase surface). The SELDI spectra were analyzed by multivariate statistical analysis and artificial neural networks in order to find a biomarker panel which differentiates best between the groups. In order to identify protein/peptide peaks from SELDI spectra which showed a significant difference between groups, fractionated tear samples were analyzed using MALDI-TOF MS (matrix-assisted laser desorption/ionization time-of-flight mass spectrometry). For validation of biomarkers, we used an antibody microarray approach. Complex patterns of tear proteins and peptides were detected in the control group and in both contact lens groups. The tear protein composition in both wearers of rigid gas permeable (CL_H) and soft contact lenses (CL_S) differed significantly from protein composition in non-contact lens wearers (p < 0.01). The identification of biomarkers revealed an increase of Protein S100 A8 in the group of wearers of soft contact lenses (CL_S) and a decrease of a main tear protein, lysozyme, in both contact lens groups. The identified biomarker cystatin was upregulated in the group of rigid gas permeable lens wearers (CL_H), whereas the protein intensity of secretoglobin was significantly reduced in this group. Using the microarray approach, detected alterations could be confirmed. Contact lens wear alters the protein profiles in a complex manner. This study demonstrates that significant changes can be found in wearers of soft contact lenses (CL_S) and rigid gas permeable contact lenses (CL_H). Some biomarker intensities are significantly altered only in the group of rigid gas permeable lens wearers (CL_H).

Randomised controlled trial of the effects of two rigid gas permeable (RGP) contact lens materials and two surface cleaners on straylight values

In a double-masked randomized controlled crossover study we investigated both the retinal responses to straylight, and the effects of lens cleaners on straylight values, in two different RGP contact lens materials. Thirty patients (20-59 years) wearing RGP lenses were refitted with new lenses made of Boston XO material in one eye and made of Comfort O2 (ONSI-56) material in the other eye. Reported wetting angles for the Boston XO material (103 degrees ) and for the ONSI-56 material (7.2 degrees ) were obtained by sessile drop measurements. After refitting, the study comprised three 5-week trial periods. In Period 1 half of the participants (Group A) wore Boston XO lenses in their right eye and Comfort O2 (ONSI-56) lenses in their left eye, and the other half (Group B) vice versa. In Period 2 Group A wore Comfort O2 (ONSI-56) lenses in their right eye and Boston XO lenses in their left, and Group B vice versa. All participants used Miraflow cleaner during periods 1 and 2. In Period 3, during which all participants used Boston cleaner, Group A wore Boston XO lenses in their right eye and Comfort O2 (ONSI-56) lenses in their left eye and Group B vice versa. Straylight data (log S) were obtained with and without contact lenses using the Oculus C-Quant straylight meter in all three periods. Central corneal thickness (CCT) was measured in the second and third periods. When not wearing lenses (n = 60 eyes) at the end of the second 5 week trial period straylight was measured twice with averages of 1.07 log S, and the corrected CCT measurements averaged 546 mum. Straylight values with Comfort O2 (ONSI-56) reached 1.15 log S at the end of both the second (n = 25 eyes) and third periods (n = 23 eyes). Straylight values with Boston XO were 1.17 log S (n = 26 eyes) at the end of the second period, and 1.16 log S (n = 25 eyes) at the end of the third period. Existing RGP lens wearers refitted with new lenses with different contact angles, made of Boston XO and Comfort O2 (ONSI-56) showed, over three 5 week periods, relatively small increases in straylight, which were functionally comparable, irrespective of the type of lens material or lens cleaner used. At every visit, straylight values and CCTs returned to baseline levels after RGP lens removal, confirming that the straylight fluctuations were mainly due to scattering from the RGP lenses; or tear film interaction; or a combination of both.