Effectiveness of toric soft contact lenses for vision correction in patients with different degrees of astigmatism: a real-world study

AIM:To assess the visual correction of patients with different degrees of astigmatism with toric soft contact lenses(TSC).METHODS:It was a real-world study with prospective and single-arm design.A total of 384 patients with astigmatism who came for TSC fitting and alignment from November 2022 to January 2023 were included.According to the difference in astigmatism,patients were divided into groups A(cylinder degree:-0.75 to-0.50 D),B(cylinder degree:-1.75 to-1.00 D)and C(cylinder degree≤-2.00 D),and followed up on the day of wear,1wk,1 and 3mo,mainly to observe visual acuity,refraction,lens fit,visual quality and comfort at 1wk after wear.The visual acuity success rate and the overall success rate of the fitting were evaluation indicators(taking into account the four dimensions of visual acuity,fitting,quality of vision and comfort).The visual acuity success rate was calculated by taking“corrected visual acuity with contact lenses is no less than 1 line or better than best spectacle-corrected visual acuity”(i.e.corrected visual acuity with contact lenses is 1 line below,equal to,one line above or more than best spectaclecorrected visual acuity)as the criterion for visual success,and the the overall success rate of the fitting was calculated by using the comprehensive indicators(visual acuity,fit,visual quality,comfort)to meet certain conditions as the judgment criteria for successful fitting.RESULTS:After 1wk of wearing TSC,the visual acuity success rates of patients were 100%(207/207),98.58%(139/141)and 97.22%(35/36)in the three groups,respectively,with residual cylinder closed to 0.The acceptability of the lens fitting was over 95%;the incidence of adverse visual symptoms was within 10%and the comfort acceptability was over 97%.The overall success rate of fitting for patients with high,medium and low astigmatism was 93.72%(194/207),90.78%(128/141)and 88.89%(32/36),respectively.CONCLUSION:TSC(model:G&G POP·CT)are effective in correcting astigmatism in patients with different degrees of astigmatism.

Is the Use of Empirically Designed Custom Soft Contact Lenses a Good Option for Challenging Patients?

Purpose: Reasons for the lack of success for contact lens patients range from poor fit, to discomfort or to a less than optimum wearing schedule. This project was a preliminary investigation of customized soft toric contact lenses as an alternative for unsuccessful contact lens patients or potential drop-outs. Methods: Fifteen healthy non-compromised, previously unsuccessful contact lens wearing patients (13 women, 2 men) with ages from 21 to 33 years (25.1 ± 2.7 years) were the subjects for this study. They were empirically fitted with 15 astigmatic and 5 spherical customized SpecialEyes soft contact lenses. Visual acuities, comfort, lens movement, and rotation were evaluated. Results: Patients fitted with customized SpecialEyes soft contact lenses had statistically significant better visual acuities than with Phoropter Manifest Refraction. The lenses used in this study centered well and moved no more than 1 mm upon each blink. Lens rotation was less than 10 degrees for all toric lenses. Patients gave very positive vision and comfort ratings. Conclusion: This preliminary study supports the application of a software program to empirically design and manufacture Special Eyes custom soft lenses based upon corneal topographical parameters and subjective manifest refraction for those patients who either have challenging corneal parameters, high sphero-cylindrical prescriptions, or are currently dissatisfied with their contact lenses and are potential drop-outs.

Oxygen permeability of soft contact lenses in different pH, osmolality and buffering solution

AIMTo determine the effect of pH, osmolality, and buffering system on the oxygen permeability (Dk) of soft contact lenses.METHODSTwo hydrogel lenses (nelfilcon A and etafilcon A) and 2 silicone hydrogel lenses (lotrafilcon A and balafilcon A) were used in the study. These lenses were incubated in phosphate-buffered saline (PBS) and borate-buffered saline (BBS) solutions adjusted by 0.8 pH increments to a pH in the range of 5.8-9.0 or in hypotonic (280 mOsmol/kg), isotonic (310 mOsmol/kg) and hypertonic (380 mOsmol/kg) PBS solutions. Polarographic method was used for measuring the Dk and lenses were stacked as 4 layers to correct the boundary effect.RESULTSDk values of all contact lenses measured in BBS solutions were more stable than those in PBS solutions. Especially the etafilcon A lens showed a relative big change compared with other types of contact lenses at the same conditions. When the osmolality of PBS solution increased from hypotonic to hypertonic, Dk of all contact lenses decreased. Variations in Dk existed depending on lens materials, etafilcon A lens was the most affected and nelfilcon A was the least affected by osmolality.CONCLUSIONFrom the result obtained, it is revealed that Dk of contact lenses is changed by the pH, osmolality, and buffering condition of tear. Thus, Dk of contact lens can be varied by the lens wearers' physiological and/or pathological conditions.

Corneal Wavefront Aberrations in Patients Wearing Multifocal Soft Contact Lenses for Myopia Control

Purpose: The purpose of this study was to evaluate the change in corneal wavefront aberrations in young adults who have been fit with multifocal soft contact lenses for myopia progression control. Findings have been analyzed for statistical significance and clinical relevance and compared to reportedly successful Orthokeratology outcomes. Methods: The dominant eye of 40 participants (27 women, 13 men;mean age 27.3 ± 3.2 years;range 23 to 39 years) was fit with Proclear Multifocal center distance lenses (Coopervision, Pleasanton, USA) having a variety of distance powers and reading additions. Refractive errors were limited to a range of –6.00 D up to +1.00 D of sphere, and no greater than –1.00 D of cylinder. Corneal wavefront measurements were performed over 6 mm diameters with a Zeiss Atlas 9000 corneal topographer (Zeiss Meditec, Dublin, USA) prior to, and following lens fitting. Data were converted into rectangular Fourier optics terms M, J0, J45 and RMS values for each reading addition were statistically analyzed. Following evaluation of statistical significance and clinical relevance, results were compared to published data from successful Orthokeratology treatments. Results: Statistically significant changes in higher order aberrations were detected for lenses of all reading additions. Lens groups with higher Add-powers demonstrated stronger changes with increased significance. Final RMS values relating to 2nd, 3rd and 4th Zernike Orders reached clinical significance with a wavefront error of 0.10 μm, the equivalent of 0.25D. Moreover, as Add-powers increased, 3rd and 4th order aberrations likewise showed an increase. Pre-fitting astigmatism values accounted for the highest recorded aberrations and remained predominantly unchanged. Conclusion: Proclear Multifocal center-distance contact lenses were found to increase higher order wavefront aberrations in a manner dependent on their Add-power. In comparison to successful Orthokeratology outcomes, the amounts of resulting aberrations are notably different.

Contact lens impact on quality of life in keratoconus patients: rigid gas permeable versus soft siliconehydrogel keratoconus lenses

AIMTo determine the impact of rigid gas permeable (RGP) and silicone-hydrogel keratoconus lenses on the quality of life (QoL) in keratoconus (KCN) patients using the self-reported results from the Contact Lens Impact on Quality of Life (CLIQ) Questionnaire.METHODSFrom January 2013 to April 2013, 27 consecutive KCN patients who wore RGP contact lenses (conflexair100 UV KE Zeiss-Wöhlk) or soft silicone-hydrogel contact lenses (SHCLs) for KCN (KeraSoft IC- Bausch&Lomb or Hydrocone Toris K-Swiss lens) completed the CLIQ questionnaire.RESULTSThe mean age of 27 patients was 29.6±8.0y. Fifteen patients were RGP user. The groups were comparable with respect to the mean patient age, sex, and mean K values (P=0.1, P=0.8 and P=0.1, respectively). The mean CLIQperson measure was 42.8±5.5 in RGP group and 39.6±5.5 in SHCLs for KCN group (P=0.06). CLIQperson measure was positively correlated with steep K value (r=0.301, P=0.04). When eyes were stratified by visual acuity with contact lenses, the mean CLIQperson measure was 42.01±5.6 in eyes with a visual acuity of 20/20-20/25 (n=44) and 38.4±5.26 in eyes with a visual acuity of 20/32 or less (n=10; P=0.097).CONCLUSIONRGP lenses and SHCLs for KCN have similar impact on QoL.

Intraocular pressure measurement over soft contact lens by rebound tonometer: a comparative study

AIM: To evaluate the intraocular pressure(IOP)measurements by Icare rebound tonometer over a contact lens in comparison with Goldmann applanation tonometry(GAT). METHODS: Fifty patients using contact lens were included in this study. One of the eyes of the patients was selected randomly and their IOP were measured by rebound tonometer with and without contact lens(RTCL,RT respectively) and by GAT, as well as their central corneal thickness(CCT) by optical pachymeter. The results of both methods were compared by correlation analysis, general linear method repeated measure and Bland-Altman analysis.RESULTS: Mean IOP values measured by RTCL, RT and GAT were 15.68 ±3.7, 14.50 ±3.4 and 14.16 ±2.8(P 【0.001), respectively. Mean IOP by RTCL was significantly higher than the measurements implemented by RT and GAT(P 【0.001), while there was no difference between the measurements by GAT and RT(P =0.629). There was a good level of positive correlation between GAT and RTCL as well as RT(r =0.786 P 【0.001, r =0.833 P 【0.001, respectively). We have observed that CCT increase did not show any correlation with the differences of the measurements between RTCL and RT(P =0.329), RTCL and GAT(P =0.07) as well as RT and GAT(P =0.189) in linear regression model.CONCLUSION: The average of the measurements over contact lens by rebound tonometer was found to be higher than what was measured by GAT. Although this difference is statistically significant, it may be clinically negligible in the normal population.

EFFECT OF SHORT-TERM SOFT CONTACT LENS WEAR ON HUMAN OCULAR ABERRATIONS

Objective To evaluate the effect of short-term soft contact lens （SCLs） wearing on human ocular aberrations （ HOA ）. Methods This prospective study included 50 eyes of 50 young volunteers wearing SCLs for 1 month. The ocular aberrations were measured by Allegretto Wavefront Analyzer. The root-mean-square （RMS） values of the general （RMSG） , higher-order （RMSH） , first to sixth order （ RMS1 to RMS6） and aberration coefficients were analyzed. Results There were no significant differences in the mean values of RMSG, RMSH, RMS1 to RMS6 （ P 〉 0. 05 ） and changes of absolute values of aberration coefficients between baseline and various visits after SCLs discontinuation. However, at d I after the discontinuation of SCLs, changes in coefficient values of the third-order aberrations （ C6 to C9 ） were slightly higher than others, and C7 was the highest. The increase factors of RMS values were higher at 1 week and lower at the 2 week visit after SCLs discontinuation. The uniformity of dominating type in HOA and the corneal topography form was both about 60% after discontinuation of SCLs. The corneal thickness increased after SCLs wear and gradually decreased to baseline until 1 month discontinuation of SCLs. Conclusion The effect of short-term SCLs wear on human ocular aberrations is slight but profound. A month or more wait should be allowed before the short-term SCLs wearers are scheduled for wavefronted-guided LASIK.

EFFECTS OF PREOPERATIVE SOFT CONTACT LENS WEAR ON HIGHER-ORDER ABERRATIONS AFTER LASER IN SITU KERATOMILEUSIS

Objective To evaluate the effects of preoperative soft contact lens (SCL) wear on higher-order aberrations(HOAs)correction after wavefront-guided and conventional laser in situ keratomileusis (LASIK). Methods A prospective randomized double-masked comparative study was conducted in 180 eyes of 90 patients scheduled for LASIK, including 92 eyes of 46 patients with previous SCL wear. The patients were divided into four groups: no SCL-conventional group, SCL-conventional group, no SCL-wavefront group and SCL-wavefront group. Preoperative and postoperative examinations included uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), contrast sensitivity and HOAs. Results The UCVA and BSCVA were 20/20 in all patients at 6 months postoperatively. And 36.3%, 22.7%, 18.1% and 35.4% gained one line or more of BSCVA in no SCL-wavefront group, SCL-wavefront group, no SCL-conventional group and SCL-conventional group, respectively. Both the safety index and efficacy index surpassed one in 4 groups and were highest in no SCL-wavefront group. The increase in root-mean-square (RMS) values of HOAs was significantly lower in no SCL-wavefront group and higher in SCL-wavefront group. At 6 months postoperatively, the increase in RMS of HOAs (RMSh) were 0.67, 1.58, 1.17 and 1.28 in no SCL-wavefront group, SCL-wavefront group, no SCL-conventional group and SCL-conventional group, respectively. Conclusion Preoperative contact lens wear has significant influence on the efficacy of HOAs correction in wavefront-guided LASIK. Patients with contact lens wear preoperatively should be cautious when scheduled for wavefront-guided LASIK.

Soft Bandage Contact Lenses in Management of Early Bleb Leak Following Trabeculectomy

Purpose: To investigate the efficacy of a soft bandage contact lens in the management of early bleb leak following trabeculectomy.Methods: Between October 2011 and April 2013, 11 patients with early bleb leak following fornix-based trabeculectomy were instructed to wear a soft bandage contact lens 14 mm in diameter continuously for 1-2 weeks. The daily visual acuity,intraocular pressure(IOP), anterior chamber situation, and healing condition were measured at 1, 3, and 7 d, after con tact lens removal,.and 3 months after trabeculectomy..The conditions of blebs,.sensation of wearing contact lens,.and adverse events were recorded.Results:.Bleb leaks were observed at 2-8 d after surgery,(4.09±1.10 d on average). The daily Log MAR visual acuity did not significantly differ before and after contact lens wear(P>0.05). The IOP was significantly raised after at 1, 3, and7 d after lens wear.(all P <0.05).The IOP at 3 months after lens wear did not significantly differ from that measured at lens removal(t=1.191, P=0.089). At 1 d after lens wear, 6cases had deeper anterior chambers..All patients presented with a significantly deepened anterior chamber at 3 d after lens wear,.and were restored to the preoperative conditions..The bleb leakage was successfully treated at 7 d after lens removal in 10 patients, while 1 patient had to wear the contact lens for another 7 d for full healing of the bleb leak. No ocular infection was noted throughout the management.Conclusion: A soft bandage contact lens of 14 mm diameter is a safe and efficacious therapy for an early bleb leak following fornix-based trabeculectomy.

Clinic study on silicone hydrogel contact lenses used as bandage contact lenses after LASEK surgery

AIM: To compare the clinical performance of two types of silicon hydrogel contact lenses used as bandage lenses after LASEK surgery. METHODS: A prospective, double-masked study was conducted on 42 eyes of 21 patients who received binocular LASEK surgeries. The interocular difference in spherical equivalent power was less than -1.50D. Patients were randomly assigned to wear Galyfilcon A (Lens A) bandage contact lens in one eye and Balafilcon A (Lens B) in the fellow eye after the surgery. The responses to a subjective questionnaire on comfort of wearing, corneal epithelial status, conjunctival hyperemia, limbal neovascularization, lens fitting and contact lens debris were assessed 1 and 5 days postoperatively. Corneal endothelium was assessed before and 5 days after the surgery upon bandage lens removal. RESULTS: There was no difference between the two groups in terms of conjunctival hyperemia, limbal neovascularization, contact lens fitting, corneal epithelial status, corneal endothelium cell density (CD) and endothelium cell size (CS) at any postoperative visit. Complaints of discomfort, including foreign body sensation, pain and intolerance were statistically more among Lens B wearers at any postoperative visit (P < 0.05). Lens B appeared to attract much more debris than Lens A at the 5-day post-operative follow-up visit (P < 0.01). CONCLUSION: The two types of silicon hydrogel lenses investigated in this study demonstrated similar clinical performance in terms of corneal responses and lens fitting. However, Lens A showed a better performance in terms of comfort of wearing and deposit resistance.

Application of Flipped Classroom Teaching Model Based on Micro-Course in Practical Training Teaching of Contact Lens Fitting Technology

Objective:This paper aims to study the application of flipped classroom teaching model based on micro-course in the practical training teaching of contact lens fitting technology.Methods:From September 21 to July 23,120 students majoring in ophthalmology and optometry were selected and randomly divided into groups.The control group adopted the traditional teaching mode,and the study group adopted the flipped classroom teaching mode based on micro-course.Teaching scores and the skills,observation and judgment,adaptability,and communication skills were compared between the groups.Results:Statistical comparison of teaching scores under different management methods showed that the clinical thinking score and practice work quality in the study group were higher than those of the control group,and the effect of the study group was better(P<0.05).The overall scores of skills,observation and judgment,adaptability,and communication skills of the study group were better than those in the control group,and the comprehensive ability scores in the two groups were significantly different(P<0.05).Conclusion:In practical training teaching of contact lens fitting technology,the application of flipped classroom teaching based on micro-course can improve the skill scores of personnel,and the overall effect is good.This can lay the foundation for advanced ophthalmology and optometry talents with profound theoretical knowledge and professional skills.

Comparation of effectiveness of silicone hydrogel contact lens and hydrogel contact lens in patients after LASEK

AIMTo conduct a comparative study of effectiveness of silicone hydrogel contact lens and hydrogel contact lens, which are used in patients after laser-assisted subepithelial keratomileusis (LASEK).METHODSSixty-three patients (121 eyes) with a spherical equivalent ≤-5.0 D were chosen after undergoing LASEK in 2012 at Guangdong General Hospital. They were randomly divided into 2 groups. The silicone hydrogel group included 32 cases (61 eyes) that wore silicone hydrogel contact lenses for 4-6d after the operation, while the hydrogel group included 31 cases (60 eyes) who wore hydrogel contact lenses for 4-6d after the operation. Patients' self-reported postoperative symptoms (including pain, photophobia, tears, and foreign body sensation) were evaluated. The healing time of the corneal epithelium, the visual acuity of patients without contact lens after epithelial healing, and the incidence of delayed corneal epithelial shedding were also assessed. The follow-up time was 1mo.RESULTSPostoperative symptoms were milder in the silicone hydrogel group than in the hydrogel group. There were significant differences in pain, foreign body sensation, and photophobia between the 2 groups (P<0.05), although there was no significant difference in postoperative tearing (P>0.05). The healing time of the corneal epithelium in the silicone hydrogel lens group was markedly shorter than that in the hydrogel group (4.07±0.25 vs 4.33±0.82d, t=2.43, P=0.02). Visual acuity without contact lenses after healing of the corneal epithelium was better in the silicone hydrogel group compared with the hydrogel group (χ2=7.76, P=0.02). There was no significant difference in the occurrence of delayed corneal epithelial shedding between the 2 groups (P>0.05).CONCLUSIONPatients with LASEK using silicon hydrogel contact lenses had less discomfort and shorter corneal epithelial healing time compared with those using hydrogel contact lenses, suggesting that silicon hydrogel contact lenses may be considered to be a better choice of bandage contact lens after LASEK.

Comparison of the effects of first and second generation silicone hydrogel contact lens wear on tear film osmolarity

AIM:To compare the effects of first and second generation silicone hydrogel(SiH) contact lens wear on tear film osmolarity.METHODS:The healthy subjects who have never used contact lenses before were enrolled in the study.Tear film osmolarity values of 16 eyes(group 1) who wore first generation SiH contact lenses were compared with those of 18 eyes(group 2) who wore second generation SiH contact lenses after three months follow-up.RESULTS:Beforecontactlenswear,tearfilmosmolarity of groups 1 and 2 were 305.02±49.08 milliosmole(mOsm) and 284.66±30.18mOsm,respectively.After three months of contact lens wear,osmolarity values were found 317.74±60.23mOsm in group 1 and 298.40±37.77mOsm in group 2.Although osmolarity values for both groups of SiH contact lens wear after three months periods were slightly higher than before the contact lens wear,the difference was not statistically significant. CONCLUSION:Contact lens wear may cause evaporation from the tear film and can increase tear film osmolarity leading to symptoms of dry eye disease.In the current study,there is a tendency to increase tear film osmolarity for both groups of SiH contact lens wear,but the difference is not statistically significant.

Does offering only the spherical contact lens trial to the low astigmats mislead the practitioners?

AIM:To compare the visual acuity(VA),comfort,and patient preference in a soft toric contact lens(TCL)versus soft spherical contact lens(SCL)in low astigmatic subjects during the contact lens(CL)trial.METHODS:This subject-masked,block randomized,2×2 crossover study recruited 40 neophyte subjects(80 eyes)aged 18 to 33 y with astigmatism in the range of 0.75-1.25 D with or without spherical power from-6.00 D to+6.00 D.The participants were scheduled for two days CL trial and were fitted with the best-fit SCL and TCL.After 4 h of wear,they were assessed objectively for high contrast VA and subjective vision,comfort,and preference.RESULTS:The responses of 36 subjects(response rate 90%)with a mean age of 23.02±2.97 y(range 18 to 33 y)were analyzed.One-line improvement of monocular VA in the logMAR chart was reported to TCL as compared to SCL(-0.044±0.06 vs 0.04±0.03 logMAR,P=0.01)but the binocular vision remained similar(-0.12±0.07 vs-0.14±0.04 logMAR,P=0.38).Subjects felt a noticeable difference in clarity when shifted to TCL as compared to the SCL.The satisfaction with vision(vision quality)was significantly better with TCL(P=0.03).The fatigue with TCL was graded less at 2.5±0.6,compared to SCL at 4.6±1.3(P=0.04).Thirty-three participants(91.6%)preferred to use contact lens of which 26 participants(79%)preferred TCL.CONCLUSION:The findings suggest that VA and comfort are better with TCL as compared to SCL which is only observed if the patient was offered both offering SCL with spherical equivalent power alone as the first option can mislead the practitioner;TCL trial should be the first choice of the lens in low-to-moderate astigmatism.

Evaluation of refractive correction for standard automated perimetry in eyes wearing multifocal contact lenses

AIM：To evaluate the refractive correction for standard automated perimetry（SAP）in eyes with refractive multifocal contact lenses（CL）in healthy young participants.METHODS：Twenty-nine eyes of 29 participants were included.Accommodation was paralyzed in all participants with 1%cyclopentolate hydrochloride.SAP was performed using the Humphrey SITA-standard 24-2 and 10-2 protocol under three refractive conditions：monofocal CL corrected for near distance（baseline）;multifocal CL corrected for distance（m CL-D）;and m CL-D corrected for near vision using a spectacle lens（m CL-N）.Primary outcome measures were the foveal threshold,mean deviation（MD）,and pattern standard deviation（PSD）.RESULTS：The foveal threshold of m CL-N with both the24-2 and 10-2 protocols significantly decreased by 2.2-2.5 d B（P〈0.001）,while that of m CL-D with the 24-2 protocol significantly decreased by 1.5 d B（P=0.0427）,as compared with that of baseline.Although there was no significant difference between the MD of baseline and m CL-D with the24-2 and 10-2 protocols,the MD of m CL-N was significantly decreased by 1.0-1.3 d B（P〈0.001）as compared with that of both baseline and m CL-D,with both 24-2 and 10-2 protocols.There was no significant difference in the PSD among the three refractive conditions with both the 24-2 and 10-2 protocols.CONCLUSION：Despite the induced mydriasis and the optical design of the multifocal lens used in this study,our results indicated that,when the dome-shaped visual field test is performed with eyes with large pupils and wearing refractive multifocal CLs,distance correction without additional near correction is to be recommended.

Continuous Wear of Hydrogel Contact Lenses for Therapeutic Use

Purpose: To investigate the efficacy and complications of continuous wear of etafilcon A for therapeutic use. Materials and Methods: The subjects were 228 eyes of 219 outpatients prescribed contact lens (CL) for one week of continuous therapeutic wear during 10 years. The reason for prescription of CLs, the primary disease, the duration of CL wear and the complications were assessed retrospectively. Results: The predominant reason for prescription of CLs was relief of pain or a foreign-body sensation (62.3%) and protection of the corneal epithelium (20.6%). The primary disease was post-penetrating keratoplasty (36.8%), followed by corneal epithelial erosion (14.5%), post-lamellar keratoplasty (14.0%) and bullous keratopathy (12.2%). The average duration of wearing single lens was 6.5 ± 3.2 days. The average duration of wearing CLs in total was 9.2 ± 10.7 months. The most frequent problem associated with continuous wear of CLs was their dropping out of CLs (12.3%). The complications associated with CLs included conjunctivitis with papillary hyperplasia, corneal erosion and superficial punctate keratitis, but corneal ulcer and corneal infiltrates were not found. Conclusion: Serious complications were not shown changing the lenses every week to keep to the prescribed time limit for continuous therapeutic wear, even if corneal epithelial barrier function is impaired.

ZERNIKE ASTIGMATISM AND VISUAL PERFORMANCE IN MYOPIC EYES BY RIGID GAS PERMEABLE CONTACT LENSES WEAR

To investigate the effects of rigid-gas-permeable contact lens(RGP-CL)wear on Zernike astigmatism and visual performance in myopic eyes.Methods:A wavefront sensor was used to evaluate Zernike astigmatism for 21 eyes with minimum astigmatism and 18 eyes with moderate astigmatism under three different modes of refractive correction:the RGP-CL,spectacle lens correcting spherical equivalent(SL)and spectacle lens fully correcting spherical error and astigmatism(fSL).Contrast visual acuity was assessed with a VA tester at four contrast levels and two luminance backgrounds.Results:Compared to the SL wear,RGP-CL wear changed the main axis astigmatism(Z_(2)^(2))from
0:09-0:34 to 0.34-0.22 for the minimum astigmatism group,while the contrast VA was improved about 0.05 LogMAR(F=8:06,p<0:01).For the group with moderate astigmatism,significant reduction in Z_(2)^(2)was found for both fSL wear(t=4:78,p<0:001)and RGP-CL wear(t=6:29,p<0:0001).The changes in astigmatism were significantly correlated between the fSL and RGP-CL wears(r=0:897,p<0:0001 for Z_(2)^(-2);and r=0:643,p=0:004 for Z_(2)^(2)).Contrast VA was significantly improved for both fSL and RGP-CL wears and the improvements were significantly correlated between each other for all four contrast levels and two backgrounds.Conclusion:RGP-CL wear induces astigmatism for the eyes with minor astigmatism probably due to a correction of corneal astigmatism and thus a manifesting of the lens astigmatism.For the astigmatic eyes,RGP-CL wear has similar effect on correcting astigmatism as the spectacle lens wear with spherical-cylinder correction and also produces similar visual improvement.

Curative effect assessment of bandage contact lens in neurogenic keratitis

AIM: To observe the curative effect of bandage contact lens in neurogenic keratitis.METHODS: Twenty cases of neurogenic keratitis were studied at the Department of Ophthalmology, the First Affiliated Hospital of China Medical University, between October 2012 and June 2013. These included 13 males and 7 females, aged from 35 to 88 y. Patients were voluntarily divided into an experimental group(lens wearing group, n =10) and control group(drug therapy,n =10). In experimental group patients wore silicone hydrogel bandage soft contact lens. Both groups used the following eyedrops: 0.5% levofloxacin TID; 0.5%Sodium carboxymethyl cellulose QID; fibroblast growth factor BID; ganciclovir BID [cases complicated with herpes simplex virus(HSV)]; compound tropicamide BID(cases concurrent hypopyon). The healing time of corneal ulcer and complication rates were observed in the two groups.RESULTS: The healing time of corneal ulcer in the experimental group was 10.80±4.44 d versus 46.70±13.88 d in the control group(P 【0.05). No complications occurred in the experimental group, except for the lens falling off twice in one case, the patient recovered eight days after rewearing the lens. While in the control group, all cases vascularized, 2 cases were complicated with descemetocele that recovered with amniotic membrane transplantation and 1 case was complicated with corneal perforation that recovered by autologous conjunctival flap covering.CONCLUSION: Bandage contact lens is a safe and effective method of treating neurogenic keratitis andsignificantly shortened the healing time of corneal ulcer.

Numerical Simulation of Heat Transfer and Deformation of Initial Shell in Soft Contact Continuous Casting Mold Under High Frequency Electromagnetic Field

Heat transfer and deformation of initial solidification shell in soft contact continuous casting mold under high frequency electromagnetic field were analyzed using numerical simulation method; the relative electromagnetic parameters were obtained from the previous studies. Owing to the induction heating of a high frequency electromagnetic field （20 kHz）, the thickness of initial solidification shell decreases, and the temperature of strand surface and slit copper mold increases when compared with the case without the electromagnetic filed. The viscosity of flux de- creases because of the induction heating of the high frequency electromagnetic field, and the dimension of the flux channel increases with electromagnetic pressure; thus, the deformation behavior of initial solidification shell was different before and after the action of high frequency electromagnetic field. Furthermore, the abatement mechanism of oscillation marks under high frequency electromagnetic field was explained.

Effects of contact lens wearing on keratoconus:a confocal microscopy observation

AIM： To evaluate the corneal cell morphology of new keratoconus patients wearing two different types of rigid gas-permeable（RGP） contact lenses for 1y.METHODS： Thirty nine eyes of 39 new keratoconus patients were selected and randomly fitted with two types of RGP contact lenses.Group 1 had 21 eyes with regular rigid gas-permeable（RRGP） contact lens and rest 18 eyes were in group 2 with specially designed rigid gas-permeable（SRGP） contact lens.Corneal cell morphology was evaluated using a slit scanning confocal microscope at no-lens wear and after 1y of contact lens wearing.RESULTS： After 1y of contact lens wearing in group 1,the mean anterior and posterior stromal keratocyte density were significantly less（P=0.006 and P=0.001,respectively） compared to no-lens wear.The mean cell area of anterior and posterior stromal keratocyte were also significantly different（P=0.005 and P=0.001） from no-lens wear.The anterior and posterior stromal haze increased by 18.74% and 23.81%,respectively after 1y of contact lens wearing.Whereas in group 2,statistically significant changes were observed only in cell density ＆ area of anterior stroma（P=0.001 and P=0.001,respectively） after 1y.While,level of anterior and posterior stromal haze increased by 16.67% and 11.11% after 1y of contact lens wearing.Polymegathism and pleomorphism also increased after 1y of contact lens wearing in both the contact lens groups.CONCLUSION： Confocal microscopy observation shows the significant alterations in corneal cell morphology of keratoconic corneas wearing contact lenses especially in group 1.The type of contact lens must be carefully selected to minimize changes in corneal cell morphology.