A 3-month comparison study of subjective and objective visual quality of small incision lenticule extraction and transepithelial photorefractive keratectomy in patients with low and moderate myopia

AIM:To compare the subjective and objective visual quality between small incision lenticule extraction(SMILE)and transepithelial photorefractive keratectomy(t PRK)in patients with low and moderate myopia.METHODS:Patients undertaking SMILE or t PRK for the correction of low and moderate myopia were consecutively recruited in this prospective cohort study with a 3-month follow-up period.Objective evaluation[visual acuity test,manifest refraction,wavefront aberrations,the total cut-off value of the total modulation transfer function(MTFcut-off),and Strehl ratio(SR)]and subjective evaluation of visual quality(quality-of-life questionnaire)were conducted before surgery and at days 1,7,30,and 90 after surgery.RESULTS:A total of 47 patients(94 eyes)with SMILE and 22 patients(22 eyes)with t PRK were enrolled.The uncorrected visual acuity(UCVA)was better in SMILE patients on day 7 after surgery(1.13±0.13 vs 0.99±0.17,t=4.85,P<0.001)but was comparable at days 30 and 90.At day 90,the SMILE group had a lower spherical equivalent(SE)than the t PRK group(0.04±0.31 vs 0.19±0.43,t=2.08,P=0.042).Total higher order aberrations(HOAs)were induced in both surgical types,which were more evident in the t PRK group with 3-mm pupil diameter(0.16±0.07 vs0.11±0.05,t=4.27,P<0.001)and 5-mm pupil diameter(0.39±0.17 vs 0.36±0.11,t=2.33,P=0.022).The MTFcut-offand SR showed a trend of improvement in both SMILE and t PRK patients but were statistically better in the SMILE group with both pupil diameters.There was a significant improvement of contrast sensitivity(CS)over baseline levels at the spatial frequency of 18 cycles/degree(c/d)in the SMILE group(F=2.72,P=0.033)and at 3 c/d(F=3.03,P=0.031),12 c/d(F=3.72,P=0.013),and 18 c/d(F=4.62,P=0.004)in the t PRK group.The subjective quality of life questionnaire showed a steady improvement in the SMILE group(F=8.31,P<0.001)but not the t PRK group.CONCLUSION:SMILE and t PRK are both safe and effective ways to correct low and moderate myopia.A generally better and quicker recovery of visual quality favors the application of SMILE in qualified patients.

Transpalpebral intraocular pressure measurement by Diaton compared to Goldman applanation tonometer in myopic eyes before and after transepithelial photorefractive keratectomy in Saudi Arabia

AIM:To compare intraocular pressure(IOP)measured via the trans palpebral IOP(tp IOP)method using a Diaton or with a Goldman applanation tonometer(GAT)and study the determinants of IOP difference in eyes undergoing transepithelial photorefractive keratectomy(TPRK)for myopia.METHODS:This cross-sectional validation study was held in 2020 in an eye hospital in Saudi Arabia.IOP was measured by Diaton and GAT before treatment,after one week,and one month of TPRK.It is considered if IOP difference by Diaton and GAT was less than±2 mm Hg acceptable.The IOP difference was tested if correlated to spherical equivalent(SE),central corneal thickness(CCT),age,gender,or tp IOP.RESULTS:Totolly 200 myopic eyes of 100 patients were included in the study.The mean difference of IOP measured by two methods before TPRK,1wk,and 1mo after TPRK were 0.790,-0.790,and-0.920 mm Hg,respectively(P<0.001).Diaton could measure IOP effectively 89.5%eyes before TPRK and 82%and 84%at 1wk and 1mo after TPTK,respectively.At week 1,IOP differences were significantly correlated to baseline CCT(P=0.02)and tp IOP at week 1(P<0.001).One month after TPRK,only tp IOP was significantly correlated to the difference in IOP(P<0.001).CONCLUSION:Diaton is a good screening tool for IOP before TPRK.It helps in monitoring IOP after surgery.Although more practical,it is less efficient than GAT.In eyes with high myopia and low tp IOP before surgery,IOP post-TPRK by Diaton and GAT could differ.

Single-step transepithelial photorefractive keratectomy in high myopia：qualitative and quantitative visual functions

AIM:To investigate quantitative and qualitative optical outcomes of single-step transepithelial photorefractive keratectomy(Trans PRK)in high myopia.METHODS:In a prospective interventional case-series,30 eyes with high myopia(-6.00 to-8.75 D)with(up to-3.00 D)or without astigmatism were enrolled from Bina Eye Hospital,Tehran,Iran. One-step Trans PRK was performed with aberration-free aspherical optimized profile and SCHWIND AMARIS 500 laser. One-year follow-up results for refraction,visual acuities,vector analysis,ocular wavefront(OWF)and corneal wave-front(CWF)higher order aberrations(HOA),contrast sensitivity(CS),and postoperative haze were assessed.RESULTS:After the surgery,both photopic and mesopic CSs significantly improved(both P<0.001). We detected significant induction of OWF coma and trefoil(P<0.001 for both)HOAs; CWF coma(P=0.002),spherical(P<0.001),and tetrafoil(P=0.003)HOAs in 6 mm analysis diameter; and CWF trefoil(P=0.04)HOA in 4 mm analysis diameter. The range of mean induction observed for various HOAs was0.005-0.11 μm. The 86.7% of eyes reached an uncorrected distance visual acuity of 20/20 or better; 96.7% of eyes were within ±0.5 D of targeted spherical refraction. In vector analysis,mean correction index value was 1.03 and mean index of success was 0.22. By 12mo after the operation,no eye lost any number of corrected distancevisual acuity lines. We detected no corneal haze greater than 1^+ throughout the follow-up.CONCLUSION:Our findings show promising effects of single-step Trans PRK on quality of vision in high myopic eyes. It also improves refraction and visual acuity.

Photorefractive keratectomy in the correction of astigmatism using Schwind Amaris 750s laser

AIM: To evaluate the results of three photorefractive keratectomy (PRK) procedures in the treatment of astigmatism. · METHODS: In this retrospective comparative case series, 89 eyes of 50 patients who underwent PRK treatment for astigmatism were enrolled. The patients were divided into 3 groups based on the PRK procedure: Group 1: PRK without mitomycin -C (MMC) application, Group 2: PRK with MMC application, and Group 3: Trans-Photorefractive Keratectomy (T-PRK). The efficacy, safety, predictability, and complications of treatment were assessed at 1, 3 and 6 months after the treatment. ·RESULTS: At postoperative 6 months, the percentage of postoperative uncorrected visual acuity (UCVA) of 20/ 20 or better was 55.6% (20 eyes) in group 1, 75% (15 eyes) in group 2, and 75.8% (25 eyes) in group 3 (P = 0.144). The percentage of postoperative best corrected visual acuity (BCVA) of unchanged or gained ≥1 lines was 80.6% (29 eyes) in group 1, 70% (14 eyes) in group 2, and 90.9% (30 eyes) in group 3 (P =0.151). The percentage of postoperative BCVA of lost ≥2 lines was 11.1% (4 eyes) in group 1, 20% (4 eyes) in group 2, and 6.1% (2 eyes) in group 3. The mean manifest refractive spherical equivalent (MRSE) and mean cylindrical refraction were not significantly different among the each groups (P >0.05). At postoperative 6 months, the percentage of MRSE of within ±0.50 D was 100% (36 eyes) in Group 1, 100% (20 eyes) in Group 2, and 93.9% (31 eyes) in Group 3. At the each follow-up period, there was no significant difference in number of eyes with haze and mean haze score(P>0.05). ·CONCLUSION: The study showed that PRK without MMC, PRK with MMC and T-PRK appears to have similareffectiveness, safety and predictability in the treatment of astigmatism. The incidence of haze was also similar between the three groups.

Transepithelial photorefractive keratectomy mode using SCHWIND-ESIRIS excimer laser:initial clinical results

AIM:To evaluate postoperative pain,uncorrected visual acuity(UCVA),and cornea haze value after transepithelial photorefractive keratectomy(T-PRK) performed with aspherical ablation profile using SCHWIND ESIRIS excimer laser.· METHODS:Retrospective case series.Fifty-nine eyes(32 patients) with myopia associated with or without astigmatism underwent phototherapeutic keratectomy(PTK) followed by photorefractive keratectomy(PRK) which performed by Optimized Refractive Keratecomy(ORK)-CAM software based on aspherical ablation profile using SCHWIND ESIRIS excimer laser.Postoperative pain scale was measured on a questionnaire through five levels.Haze was graded by five grades,and UCVA,manifest refraction spherical equivalent(MRSE) were analyzed.· RESULTS:Mean pain level was(1.37±0.613)(range:1 to 3),the mean time picking out the soft contact lens was(6.22±1.73) days,at 3 months,UCVA was 1.0 for 40 eyes(67.8%),0.5 for all eyes(100.0%).The UCVA was significantly less than the preoperative best spectacle corrected visual acuity(BSCVA)(t =-2.84,P =0.006),haze value was(0.27±0.25),no patients had a haze grade up to 2.Mean MRSE was(0.76±0.96) diopter(D) by 3 months.· CONCLUSION:The outcomes from this study show that using the SCHWIND ESIRIS aspherical ablation profile for transepithelial PRK has a good visual result.The primary advantage is related to a spherical ablation profile,automatically considers the ablation volume of the stroma and the accurate and smooth removal of the epithelium with PTK.Additional studies are needed to determine long-term outcomes.

Long term results of no- alcohol laser epithelial keratomileusis and photorefractive keratectomy for myopia

AIM: To evaluate the long term clinical results of mechanical no-alcohol-assisted laser epithelial keratomileusis(LASEK) versus standard photorefractive keratectomy(PRK) for low-moderate myopia.METHODS: Twenty-five eyes treated with LASEK and twenty-five eyes treated with PRK were evaluated with a mean follow-up duration of 60 mo. Mechanical separation of the epithelium was performed with blunt spatula and without application of alcohol. Laser ablation was performed with the MEL-70 excimer laser. All patients were examined daily until epithelial closure; at 1, 3, 6,and 12 mo, and every year subsequently. Main outcome measures were uncorrected distance visual acuity(UDVA), corrected distance visual acuity(CDVA),manifest refraction, haze, efficacy and safety indexes.RESULTS: Twenty-one eyes and 22 eyes completed follow-up of 60 mo in LASEK and PRK group respectively. Manifest refraction at 60 mo follow-up was-0.01 and 0.26 in LASEK and PRK group respectively. In the LASEK group mean UDVA and mean CDVA after60 mo were 20/22 and 20/20 respectively(P >0.01). In the PRK group mean UDVA and mean CDVA at 60 mo follow-up were 20/20 and 20/20 after 60mo(P >0.01). The efficacy indexes were 0.87 and 0.95, and the safety indexes were1.25 and 1.4 respectively for LASEK group and PRK group.CONCLUSION: Both standard PRK and no-alcohol LASEK offer safe and effective correction of low-moderate myopia in the long term without any statistically significant difference between the two groups.

Photorefractive keratectomy after cataract surgery in uncommon cases: long-term results

AIM: To evaluate the efficacy and safety of the excimer laser correction of the residual refractive errors after cataract extraction with intraocular lens(IOL) implantation in uncommon cases.METHODS: Totally 24 patients with high residual refractive error after cataract surgery with IOL implantation were examined. Twenty-two patients had a history of phacoemulsification and IOL implantation, and two had extra-capsular cataract extraction with IOL implantation. Detailed examination of preoperative medical records was done to explain the origin of the post-cataract refractive errors. All patients underwent photorefractire keratectomy(PRK) enhancement. The mean outcome measures were refraction, uncorretted visual acuity(UCVA), best corrected visual acuity(BCVA) and corneal transparency and follow up ranged from 1 to 8 y.RESULTS: The principal causes of residual ametropia was inexact IOL calculation in abnormal eyes with high myopia and congenital lens abnormalities, followed by corneal astigmatism both suture induced and preexisting. After cataract surgery and before the laser enhancement the mean spherical equivalent(SE) was-0.56±3 D ranging from-4.62 to +2.25 D in high myopic patients, instead it was-1±1.73 D ranging from-3.25 to +3.75 D in the astigmatic eyes, with a mean cylinder of-3.75±0 ranging from-3 to +5.50 D. After laser refractive surgery the mean SE was 0.1±0.73, ranging from-0.50 to +1.50 in the myopic group, and it was-0.50±0.57 ranging from-1.25 to +0.50 in astigmatic patients, with a mean cylinder of-0.25±0.75. In myopic patients the mean UCVA and BCVA were 0.038±0.072 logMAR and 0.018±0.04 respectively, both ranging from 0.10 to 0.0. In astigmatic patients, the mean UCVA and BCVA were 0.213±0.132 and 0.00±0.0 respectively, UCVA ranging from 0.50 to 0.22 and BCVA was 0.00. All patients presented normal corneal transparency. No ocular hypertension was detected and no corneal haze was observed. All registered values remained stable also at the end line evaluation.CONCLUSION: The excimer laser treatment of residual refractive errors after cataract surgery with IOL implantation in abnormal eyes resulted in satisfactory and stable visual outcome with good safety and efficacy.

Clinical outcomes of transepithelial photorefractive keratectomy versus femtosecond laser assisted keratomileusis for correction of high myopia in South Egyptian population

AIM: To evaluate the safety and efficacy of transepithelial photorefractive keratectomy(t-PRK) with adjuvant mitomycin C(MMC) versus femtosecond laser assisted keratomileusis(Femto-LASIK) in correction of high myopia.METHODS: Prospective randomized comparative study including 156 eyes of 156 patients with high myopia and a spherical equivalent refraction(SER) <-6.00 D. They were divided randomly into two groups: Group A included 72 eyes treated with t-PRK with adjuvant MMC and Group B included 84 eyes treated with Femto-LASIK. Visual acuity, SER, corneal topography, pachymetry and keratometry were assessed for 12 mo postoperatively.RESULTS: The preoperative mean SER was-8.86±1.81 and-9.25±1.70 D in t-PRK MMC group and Femto-LASIK respectively(P=0.99) which improved to-0.65±0.43 D and-0.69±0.50 D at 12 mo follow up. Mean SER remained stable during the 12 mo of follow-up, with no statistically significant difference between the two groups(P=0.64). In t-PRK MMC group, only six eyes needed retreatment after six months of follow up. And two eyes showed haze(one reversible haze grade 2, while the other had dense irreversible haze grade 4).CONCLUSION: t-PRK MMC provides safe and satisfactory visual outcomes and acceptable risk as Femto-LASIK in patients with high myopia.

5-year follow-up of combined non-topography guided photorefractive keratectomy and corneal collagen cross linking for keratoconus

AIM: To evaluate the visual outcomes of simultaneous non-topography guided photorefractive keratectomy(PRK) and corneal collagen cross-linking(CXL) in eyes with keratoconus 5 y after the procedure.METHODS: Prospective, interventional, non-randomized, and non-controlled case series design was used. Sixty eyes of 30 patients(16 males and 14 females; age: 21-41 y) with mild, non-progressive(stages 1-2) keratoconus were enrolled. Refraction, uncorrected distance visual acuity(UDVA) and corrected distance visual acuity(CDVA), flat and steep keratometry readings, and adverse events were evaluated preoperatively and postoperatively. Data were collected preoperatively and postoperatively at 3 mo, 1, 2, 3, 4, and 5 y follow-up visits after combined non-topography-guided PRK with CXL was performed. All patients had at least 5 y of follow-up.RESULTS: All study parameters showed a statistically significant improvement at 5 y over baseline values. The mean follow-up time was 68.20±4.71 mo(range: 60-106 mo). Patients showed a significant improvement in UDVA from 1.24±0.79 log MAR prior to combined non-TG-PRK+CXL to 0.06±0.15 log MAR postoperatively at the time of their last follow-up visit. CDVA significantly increased from 0.06±0.19 log MAR preoperatively to 0.03±0.12 log MAR postoperatively. A significant decrease in the mean spherical equivalent(SE) refraction was observed from-2.28±1.8 to-0.79±0.93 diopters(D)(P<0.05), and the manifest sphere decreased from-1.62±1.23 to-0.27±0.21 D(P=0.001). The manifest cylinder significantly decreased from-1.73±0.86 to-0.29±0.34 D postoperatively(P=0.001). The mean steep keratometry was 45.13±1.32 vs 47.28±2.12 D preoperatively(P<0.05), and the preoperative mean steepest keratometry(Kmax) 48.6±3.1 was reduced significantly to 46.8±2.9 postoperatively(P<0.05). CONCLUSION: Combined non-TG-PRK with 15 min CXL is an effective and safe option for correcting mild refractive error and improving visual acuity in patients with mild stable keratoconus.

Combined corneal CXL and photorefractive keratectomy for treatment of keratoconus: a review

Keratoconus and iatrogenic keratectasia are the corneal ectatic disorders occurring due to biomechanical weakening of the cornea resulting in distorted images,myopia, and irregular astigmatism. Corneal collagen cross-linking(CXL) is performed to arrest keratoconus successfully. The main aim of this review is to discuss the safety and efficacy of the adjuvant therapies, such as the combination of CXL and photorefractive keratectomy(PRK) for the treatment of corneal ectatic disorders. A comprehensive literature search was performed using PubM ed, MEDLINE, and Scopus using keywords ‘collagen’‘keratoconus’,‘keratectasia’,‘collagen cross-linking’,and ‘photorefractive keratectomy’. Search results were restricted to clinical studies published in English. Corneal CXL effectively arrests the progression of keratoconus by enhancing corneal rigidity. However, functional vision is not improved by cross-linking. Combining CXL to refractive surgeries such as topography-guided PRK or transepithelial PRK is found to be a safe and effective method in providing corneal stability as well as significantly improving functional visual acuity with few minor complications. This combined technique also prevents regression of keratoconus and reduce the risk of keratectasia. CXL combined with PRK is a promising therapeutic approach in ophthalmology that can be successfully used to treat progressive keratoconus and other corneal ectatic disorders and to enhance visual acuity.

Risk factors of regression and undercorrection in photorefractive keratectomy: a case-control study

AIM: To determine risk factors of regression and undercorrection following photorefractive keratectomy(PRK) in myopia or myopic astigmatism.·METHODS: A case-control study was designed in which eyes with an indication for re-treatment(RT) were defined as cases; primary criteria for RT indication, as assessed at least 9mo postoperatively, included an uncorrected distance visual acuity(UDVA) of 20/30 or worse and a stable refraction for more than 3mo.Additional considerations included optical quality symptoms and significant higher order aberrations(HOAs). Controls were chosen from the same cohort of operated eyes which had complete post-operative follow up data beyond 9mo and did not need RT. The cohort included patients who had undergone PRK by the Tissue-Saving(TS) ablation profile of Technolas 217z100 excimer laser(Bausch & Lomb, Rochester, NY, USA).Mitomycin C had been used in all of the primary procedures.·RESULTS: We had 70 case eyes and 158 control eyes,and they were comparable in terms of age, sex and follow-up time(P values: 0.58, 1.00 and 0.89,respectively). Pre-operative spherical equivalent of more than-5.00 diopter(D), intended optical zone(OZ)diameter of less than 6.00 mm and ocular fixation instability during laser ablation were associated with RT indications(all P values <0.001). These factors maintained their significance in the multiple logistic regression model with odd ratios of 6.12, 6.71 and 7.89, respectively.·CONCLUSION: Higher refractive correction(>-5.00 D),smaller OZ(<6.00 mm) and unstable fixation during laser ablation of PRK for myopia and myopic astigmatism were found to be strong predictors of undercorrection and regression.

Photorefractive Spatial Dark-Soliton Stripes in LiNbO_(3):Fe Crystal and Their Application

We observed the photorefractive spatial dark-soliton stripes In LiNbO3:Fe crystal,and demonsirate the planar waveguide property of refractive index proiile induced by these spatial dark-soli ton stripes.We suggest a new mothed to form the planar waveguide utilizing the grating fixing technique.

Incoherently Coupled Bright-Dark Soliton Pairs in Biased Centrosymmetric Photorefractive Media

It is shown theoretically that incoherently coupled bright-dark soliton pairs can exist in biased centrosymmetric photorefractive media under steady-state conditions. These soliton pairs can be established provided that the two optical beams have the same polarization, wavelength, and are mutually incoherent.

A New Method to Suppress the Fanning Noise in the Photorefractive LiNbO_(3):Fe Crystals

A new method to suppress the fanning noise caused by He-Ne laser in the cooperation with Ar+laser in photorefractive LiNbO_(3):Fe crystal was successfully realized.This method is simple and efficient.By using this method,fanning-noise-free hologram can be stored in LiNbO_(3):Fecrystal.

CLINICAL ANALYSIS OF EXCIMER LASER PHOTOREFRACTIVE KERATECTOMY FOR TREATMENT OF MYOPIA AND MYOPIC ASTIGMATISM

Ｉｎ１９８３，Ｔｒｏｋｅｌｅｔａｌ〔１〕ｆｉｒｓｔｒｅｐｏｒｔｅｄｔｈｅｌａｂｏｒａｔｏｒｙｒｅａｓｅａｒｃｈａｂｏｕｔｅｘｃｉｍｅｒｌａｓｅｒ．Ｃｌｉｎｉｃａｌｕｓｉｎｇｏｆｅｘｃｉｍｅｒｌａｓｅｒｐｈｏ－ｔｏｒｅｆｒａｃｔｉｖｅｋｅｒａｔｅｃｔｏ...

Photorefractive Self-Bending and High-Performance KNSBN:Cu Crystal Self-Pumped Phase-Conjugator

The mechanism for the high-performance KNSBN:Cu crystal self-pumped phase-conjugator is first put forward in this letter as no-loop photorefractive self-bending succesive four-wave mixing interaction.And the photore fractive backscattering amplification was found to play a very important role in it.

Transepithelial photorefractive keratectomy for myopia:effect of age and keratometric values

AIM:To investigate demographic and preoperative factors increasing the risk of ametropia following transepithelial photorefractive keratectomy(trans PRK)in myopia and myopic astigmatism.METHODS:This retrospective cohort study included myopic eyes(-0.50 to-8.75 D)with or without astigmatism(up to 3.50 D)enrolled at Dr.Yap Eye Hospital Yogyakarta.Trans PRK was performed using Technolaz 217 z100 excimer laser.Subjects were clustered into ametropia and emmetropia group based on uncorrected distance visual acuities(UDVA)3 mo post-operatively.Multiple preoperative and intraoperative parameters were analyzed using Logistic regression to obtain their effect on ametropia risk following trans PRK.RESULTS:A total of 140 eyes of 87 consecutive subjects were studied.Prevalence of ametropia following trans PRK was 20(14.29%)eyes.Subjects in ametropia group were significantly older than the emmetropia group(31.80±14.23 vs 18.88±2.41,respectively;P<0.001).Bivariate Logistic regression analysis showed that older age(OR=1.23),higher preoperative spherical equivalent(>-6 D;OR=12.78),steeper anterior keratometric readings(Kmax>45 D and mean K>44 D;OR=4.28 and 4.35,respectively)increased the risk of ametropia following trans PRK.Adjusted multivariate Logistic regression analysis showed that age was the strongest predictor for the incidence of ametropia following trans PRK.Complications of trans PRK were overcorrection,suspected posterior keratoectasia and accommodation insuffiency.CONCLUSION:Older age can be the strongest factor for increasing ametropia risk following trans PRK.Cut-off points of Kmax and mean K at 45 and 44 D respectively are proposed as the predictors for ametropia following trans PRK.

Post photorefractive keratectomy corneal ectasia

Dear Editor,We write to describe two cases of corneal ectasia occurred after photorefractive keratectomy.Due to the wide diffusion of refractive surgery,many ophthalmologists attempted to identify the risk factors and prevention methods to avoid such severe complication of this technique.Since post-

Preliminary results of a new intrastromal corneal ring segment as a tissue saving procedure in photorefractive keratectomy to correct moderate to high myopia

AIM:To evaluate the clinical results after implantation of a new intrastromal corneal ring segment(ICRS)associated with photorefractive keratectomy(PRK)to correct high myopia(HM)patients with thin corneas.METHODS:We evaluated 42 eyes of 23 HM patients that had ICRS implantation followed by PRK.The mean age of patients was 29.1±7.12 y(range 18 to 40 years old).Uncorrected visual acuity(UCVA),best corrected visual acuity(BCVA),keratometry,spherical equivalent,pachymetry,and aberrometry were compared using ANOVA with repeated measurements evaluated preoperatively and at last follow-up visit after the procedures.The refractive predictability and simulated/real corneal ablation were also assessed.RESULTS:The mean follow-up time after PRK was 6.8±1.6 mo.The mean preoperative UCVA improved from 20/800 preoperative to 20/100 after ICRS and 20/35 after PRK.The mean preoperative BCVA was 20/25(range from 20/30 to 20/20)and remained unchanged after ICRS implantation.Following the PRK the mean BCVA was 20/25(range from 20/30 to 20/20).The mean spherical equivalent decreased from-7.25±1.12(range-5.00 to-9.00)preoperatively to-3.32±1.0(range-2.00 to-5.00)postoperatively(P<0.001)after ICRS implantation and decreased from-2.44±1.51 preoperatively to 0.32±0.45(range-0.625 to 0.875)postoperatively(P<0.001)after PRK.The change in BCVA and topographic astigmatism was statistically significant(P<0.0001).CONCLUSION:ICRS in HM associated with PRK can be a tissue saving procedure and an alternative surgical option for correction of moderate to high myopia.

Synthesis of Multifunctional Polysiloxanes for Photorefractive Effect

Thephotorefractivepolymershaveat'tractedconsiderableinterestin1990sduetotheirpotentialapplicationsincoherentopticalsystemsandseveraladvantagesovertheinorganiccrystals"'.Togeneratephotorefractiveeffects,thepolymermustpossessaphoto-chargegenerator,acha...