Evaluation of preoperative dry eye in people undergoing corneal refractive surgery to correct myopia

AIM: To investigate the incidence of preoperative dry eye and related factors in patients undergoing corneal refractive surgery to correct myopia.METHODS: A total of 141 patients with myopia who underwent corneal refractive surgery were surveyed by questionnaires, tear film break-up time(BUT) test, Schimer I test(SIt), corneal fluorescein staining(FL) test and diagnosed according to the currently recognized domestic diagnostic criteria for dry eye. Correlation analysis of factors such as age, gender, regular wearing of contact lens(CL), diopter(spherical equivalent), corneal thickness, and corneal curvature that may affect the onset of dry eye was carried out to clarify the main influencing factors. RESULTS: There were 64 patients(45.39%) diagnosed with dry eye. The male patients(20.31%) was significantly less than that of non-dry eye subjects(41.56%;χ~2=7.260, P=0.007);the proportion of patients with dry eye wearing CL(81.25%) was significantly higher than that of non-dry eye subjects(51.95%;χ~2=13.234, P<0.001);the median diopter level of dry eye patients was-6.59(IQR:-8.87,-4.58) D, and the median diopter level of non-dry eye subjects was-5.69(IQR:-7.15,-4.03) D. The diopter level of dry eye patients was significantly higher(Z=-2.086, P=0.019). However, the age, best corrected visual acuity, and intraocular pressure of dry eye patients were not statistically different from those of non-dry eye subjects(t=-0.257,-0.383 and 0.778, P=0.798, 0.702, and 0.438);the corneal thickness and corneal curvature(K1 and K2) were also not statistically different either(Z=-1.487,-1.036 and-1.707, P=0.137, 0.300, and 0.088). The research further analyzes the three significant factors in the single factor analysis(gender, CL wear, and diopter) in a multi-factor way: CL wear and diopter were the influencing factors of dry eye disease. Among them, CL wear increased the risk of dry eye by 2.934 times compared with no CL wear;for every 1 D increase in diopter, the risk of dry eye increased by 0.761 times.CONCLUSION: Preoperative dry eye is relatively common in patients who undergo corneal refractive surgery to correct myopia, especially in patients who have a history of CL wear and a high diopter level before surgery. Therefore, it is necessary to carry out preoperative screening and timely treatment of dry eye to obtain the best treatment outcome and postoperative satisfaction.

Femtosecond laser corneal refractive surgery for the correction of high myopic anisometropic amblyopia in juveniles

AIM： To evaluate the effects of femtosecond laser-assisted in situ keratomileusis（FS-LASIK） and small-incision lenticule extraction（SMILE） to correct high myopic anisometropic amblyopia in juvenile patients. METHODS： From November 2013 to January 2015, 33 amblyopic patients with high myopic anisometropic amblyopia were studied. FS-LASIK（30 eyes） or SMILE（3 eyes） was performed in the amblyopic eyes. Visual acuity, refraction, contrast sensitivity, stereoacuity and complications were evaluated. Patients completed followup examinations at 3 d, 1 mo, 3 mo and the last follow-up time（mean 8.17±3.23 mo） after surgery. RESULTS： The mean age at surgery was 9.04±3.04 y（range 6-16 y）. The mean spherical equivalent in the amblyopic eyes was significantly decreased from-10.00±2.39 D preoperatively to-0.06±1.06 D at 1 mo,-0.19±1.33 D at 3 mo and-0.60±1.43 D at approximately 8 mo postoperatively（P〈0.05 for all）. The mean myopic anisometropia was significantly decreased from-9.45±2.33 D preoperatively to ＋0.37±1.48 D at 1 mo,-0.46±1.47 D at 3 mo and-0.09±1.83 D at approximately 8 mo（P〈0.05 for all）. The logarithm of the minimum angle of resolution（log MAR） for uncorrected and corrected distance visual acuity（UDVA and CDVA, respectively） of the amblyopic eye improved from 1.74±0.35 and 0.98±0.63 preoperatively to 0.45±0.31 and 0.41±0.33 at approximately 8 mo after surgery, respectively. The logM AR CDVA at 3 d, 1, 3 and 8 mo postoperatively improved by means of 1.42, 2.22, 2.96, and 4.39 lines, and a gain of more than two lines accounted for 45%, 50%, 74% and 86% of all patients, respectively. The contrast sensitivity of both amblyopic eyes and dominant eyes at 0.5, 2, 8 cycles perdegree was significantly improved postoperatively（P〈0.05 for all）. Of the 33 pediatric patients, no patients had near stereopsis preoperatively and seven patients（21.2%） recovered near stereopsis（400″ to 60″） at approximately 8 mo after surgery. No intraoperative or postoperative complications occurred in any patient.CONCLUSION： FS-LASIK or SMILE can be promising alternative methods to correct high myopic anisometropic amblyopia in juvenile patients who have failed with traditional approaches.

Comparison of total corneal power measurements obtained with different devices after myopic keratorefractive surgery

AIM:To analyze the differences,agreements,and correlation among total corneal power parameters generated by different instruments after myopic keratorefractive surgery.METHODS:The prospective cross-sectional study included patients who underwent myopic keratorefractive surgery and received measurements of corneal power 3mo after surgery.Automated keratometer was used for the measurement of simulated keratometry(Sim K),sweptsource optical coherence tomography(SS-OCT)based biometer for total keratometry(TK),anterior segment-OCT for real keratometry(RK),and Scheimpflug keratometer for the true net power(TNP),the total corneal refractive power(TCRP)and equivalent K-readings(EKR).The differences among these parameters were analyzed,and the agreements and correlation between Sim K and other total corneal power parameters were investigated.RESULTS:A total of 70 eyes of 70 patients after myopic keratorefractive surgery were included.The evaluated corneal power parameters were as follows:Sim K 38.32±1.93 D,TK 37.54±2.12 D,RK 36.64±2.09 D,TNP 36.56±1.97 D,TCRP 36.70±2.01 D,and EKR 37.55±2.00 D.Pairwise comparison showed that there were significant differences(P<0.001)among all parameters except for between TK and EKR,RK and TNP,RK and TCRP(P=1.000,1.000,1.000,respectively).The limits of agreement between Sim K and TK,RK,TNP,TCPR,and EKR were 1.08,1.08,1.43,1.48,and 1.73 D,respectively.All parameters showed good correlation with Sim K,and the correlation coefficients were 0.995,0.994,0.983,0.982,and 0.975.CONCLUSION:Among the corneal power parameters after myopic keratorefractive surgery,the value of Sim K is the largest,followed by TK and EKR,with TCRP,RK,and TNP being the smallest.The differences among the parameters may be attributable to the different calculation principles.Correct understanding and evaluation of corneal power parameters can provide a theoretical basis for taking advantage of the total corneal power to improve the accuracy of intraocular lens calculation after keratorefractive surgery.

Progress of corneal collagen cross-linking combined with refractive surgery

As a photochemical reaction that can stiffen the cornea,corneal collagen cross-linking(CXL) is the only promising method of preventing the progress of keratectasia,such as keratoconus and secondary ectasia following refractive surgery. The aim of CXL is to stabilize the underlying condition,with a small chance of visual improvement. Combining CXL with refractive surgery targeting both stabilization and reshaping of the corneal tissue for visual function improvement is a good treatment option. This review aims to provide a comprehensive and unbiased summary of the published research regarding combined CXL and refractive surgery,including measures and results,to help elucidate the future direction of CXL.

Corneal neuromediator profiles following laser refractive surgery

Laser refractive surgery is one of the most commonly performed procedures worldwide.In laser refractive surgery,Femtosecond Laser in Situ Keratomileusis and Refractive Lenticule Extraction have emerged as promising alternatives to microkeratome Laser in Situ Keratomileusis and Photorefractive Keratectomy.Following laser refractive surgery,the corneal nerves,epithelial and stromal cells release neuromediators,including neurotrophins,neuropeptides and neurotransmitters.Notably,nerve growth factor,substance P,calcitonin gene-related peptide and various cytokines are important mediators of neurogenic inflammation and corneal nerve regeneration.Alterations in neuromediator profiles and ocular surface parameters following laser refractive surgery are attributed to the surgical techniques and the severity of tissue insult induced.In this review,we will discuss the(1)Functions of neuromediators and their physiological and clinical significance;(2)Changes in the neuromediators following various laser refractive surgeries;(3)Correlation between neuromediators,ocular surface health and corneal nerve status;and(4)Future directions,including the use of neuromediators as potential biomarkers for ocular surface health following laser refractive surgery,and as adjuncts to aid in corneal regeneration after laser refractive surgery.

Surgical approaches to correct corneal astigmatism at time of cataract surgery: a mini-review

Among refractive errors,astigmatism is the most common optical aberration,where refraction changes in different meridians of the eye.It causes blurred vision at any distance and includes corneal,lenticular,and retinal astigmatism.Cataract surgery used to cause a progressive increase in the pre-exisiting corneal astigmatism because of creating a surgically induced astigmatism,for example,a large size surgery incision.The development of surgical techniques during last decades has made cataract surgery interchange to treat preoperative corneal astigmatism at time of surgery.Nowadays,three surgical approaches can be used.By placing a sutureless clear corneal incision on the steep meridian of the cornea,a preoperative corneal astigmatism less than 1.0 D can be corrected.Single or paired peripheral corneal relaxing incisions(PCRIs)provide 1.0-3.0 D corneal astigmatism correction.PCRIs are typically used for treating 1.0-1.5 D of regular corneal astigmatism,if more than 2.0 D,the risk of overcorrection and irregular astigmatism is increased.When toric intraocular lenses(IOLs)are unavailable in markets,PCRIs are still a reasonable option for patients with up to 3.0 D of pre-existing corneal astigmatism.Toric IOLs implantation can correct 1.0-4.5 D of corneal astigmatism.Several IOLs are approved to correct a high degree of corneal astigmatism with cylinder power up to 12.0 D.These approaches can be used alone or in combination.

Corneal re-innervation following refractive surgery treatments

Laser refractive surgery is one of the most performed surgical procedures in the world. Although regarded safe and efficient, it has side effects. All of the laser based refractive surgical procedures invoke corneal nerve injury to some degree. The impact of this denervation can range from mild discomfort to neurotrophic corneas. Currently, three techniques are widely used for laser vision correction: small incision lenticule extraction, laser-assisted keratomileusis in situ and photorefractive keratotomy. Each of these techniques affects corneal innervation differently and has a different pattern of nerve regeneration. The purpose of this review is to summarize the different underlying mechanisms for corneal nerve injury and compare the different patterns of corneal reinnervation.

Short term effects of small incision lenticule extraction surgery on corneal endothelium

AIM： To assess the effects of small incision lenticule extraction（SMILE） surgery on the corneal endothelium at1 d to 1mo postoperatively.·METHODS： A retrospective, observational study was conducted on 47 patients（47 eyes） who received SMILE surgery. Patients were grouped according to contact lens wear condition. The corneal endothelium was examined preoperatively and at 1d, 1wk and 1mo postoperatively.The corneal endothelium was analyzed for endothelial cell density（ECD）, percentage of hexagonal cells, and coefficient of variation（CV） of cell size.·RESULTS： There were no significant decrease in the ECD, percentage of hexagonal cells or increase in CV at1 d, 1wk and 1mo postoperatively（P 〉0.05）. However,there was a small increase of ECD by 2.88% in contact lens wearers（78.26±113.62 cell/mm2, P 〈0.05）.· CONCLUSION： SMILE has no significant adverse effects on the corneal ECD and morphology during 1mo follow-up time.

Posterior corneal astigmatism modifications after cataract surgery and its role on total corneal astigmatism

Background:In recent years posterior corneal astigmatism and its effect on total corneal astigmatism has been studied,with research showing that this can impact total astigmatism.This study aims to ascertain if there is significant change in the posterior corneal astigmatism after cataract surgery and its impact on the total astigmatism.Methods:Analysis of 76 eyes that underwent cataract surgery with monofocal intraocular lens implantation.Corneal topography was performed with Pentacam(OCULUS®)pre-and post-operatively.Total corneal astigmatism was calculated with the algorithm of vergence tracing.We compared preoperative and postoperative changes in the magnitude and axis differences of anterior corneal curvature astigmatism,posterior corneal curvature astigmatism and the calculated total corneal astigmatism.We calculated the correlation between the total preoperative astigmatism and the difference between total corneal astigmatism and anterior corneal astigmatism.Results:The mean preoperative and postoperative posterior astigmatism was 0.31±0.02 D,showing no significant differences before and after surgery(P=0.989).Statistically significant differences between the calculated total corneal astigmatism and anterior corneal astigmatism were registered preoperatively and postoperatively in the with-the-rule anterior(WTR)corneal astigmatism(P=0.004,P<0.0001);against-the-rule(ATR)anterior corneal astigmatism(P<0.0001,P<0.0001)and in the oblique(P=0.026,P=0.019)subgroups.The posterior corneal astigmatism and the total corneal astigmatism correlated positively with the differences between the total corneal and anterior corneal astigmatism(R=0.378,P=0.001).Conclusions:There were statistically significant differences between the magnitude of the total astigmatism and anterior corneal astigmatism,underlining the impact of posterior corneal astigmatism.A positive correlation between the preoperative posterior astigmatism and the difference between the total corneal and the anterior corneal astigmatism suggests a specially relevant role of posterior corneal astigmatism when evaluating patients with higher degrees of astigmatism.

Correction of low corneal astigmatism in cataract surgery

· AIM: To evaluate and compare aspheric toric intraocular lens(IOL) implantation and aspheric monofocal IOL implantation with limbal relaxing incisions(LRI) to manage low corneal astigmatism(1.0-2.0 D) in cataract surgery.· METHODS: A prospective randomized comparative clinical study was performed. There were randomly recruited 102 eyes(102 patients) with cataracts associated with corneal astigmatism and divided into two groups. The first group received toric IOL implantation and the second one monofocal IOL implantation with peripheral corneal relaxing incisions. Outcomes considered were: visual acuity, postoperative residual astigmatism, endothelial cell count, the need for spectacles, and patient satisfaction. To determine the postoperative toric axis, all patients who underwent the toric IOL implantation were further evaluated using an OPD Scan III(Nidek Co, Japan). Follow-up lasted 6mo.· RESULTS: The mean uncorrected distance visual acuity(UCVA) and the best corrected visual acuity(BCVA) demonstrated statistically significant improvement after surgery in both groups. At the end of the follow-up the UCVA was statistically better in the patients with toric IOL implants compared to those patients who underwent implantation of monofocal IOL plus LRI. The mean residual refractive astigmatism was of 0.4 D for the toric IOL group and 1.1 D for the LRI group(P 【0.01). No difference was observed in the postoperative endothelial cell count between the two groups.· CONCLUSION: The two surgical procedures demonstrated a significant decrease in refractive astigmatism. Toric IOL implantation was more effective and predictable compared to the limbal relaxing incision.

Clinical observation of removal of the necrotic corneal tissue combined with conjunctival flap covering surgery under the guidance of the AS-OCT in treatment of fungal keratitis

AIM: To study the clinical observation of removal of the necrotic corneal tissue combined with conjunctival flap covering surgery under the guidance of the AS-OCT in treatment of fungal keratitis. METHODS:A retrospective study was done to 10 patients (10 eyes) who had accepted removal of the necrotic corneal tissue combined with conjunctival flap covering surgery for fungal keratitis,the diagnosis by corneal scraping and smear examination or confocal microscopy check hyphae. Local and systemic antifungal therapy more than one week for all patients, corneal ulcer enlarge or no shrink. Slit lamp microscope examination the diameter of corneal ulcer about 2mm-4mm. Anterior segment optical coherence tomography (AS-OCT)examine the depth of corneal ulcer between 1/3-1/2, infiltrate corneal stroma about 20um-80um,the diameter of corneal ulcer about 3mm-6mm.Type-B ultrasonic exclusion endophthalmitis. Complete removal lesions until transparent of stoma, make conjunctival flap equal or greater than ulcer 1mm nearby conjunctiva. Continued antifungal therapy. The vision, fungal recurrence, conjunctival flap rollback or desquamate were analysed. ' RESULTS:Ten patients had success done this surgery, the corneal ulcer was not enlarge and healing afteroperation. 7 cases were bridging conjunctival flap and 3cases were single conjunctival flap. Preoperation vision above 0.1 had 8 cases,7 cases had vision above 0.1 one week after surgery, while 1 cases vision droped from 0.3 to 0.05.There was not recurrent for fungal,2 cases conjunctival flap rollback:1 case was bridging and 1case was single flap, no conjunctival flap desquamate. CONCLUSION: It is safe and effective to perform removal of the necrotic corneal tissue combined with conjunctival flap covering surgery under the guidance of the AS-OCT in treatment of fungal keratitis which werenot sensitive or aggravate for antifungal drugs.

Changes of corneal central thickness of aphakia following congenital cataract surgery under the first six months of life

AIM: To observe the central corneal thickness (CCT) changes in infants and young children who had been undergone bilateral congenital cataract surgery, and to compare the changes with normal control group which was selected from healthy population. METHODS: A cross section case-control study contained 28 cases (56 eyes) of bilateral aphakia (aphakic group) due to congenital cataract surgery combining with posterior continuous curvilinear capsulorhexis and with anterior vitrectomy during 2-6 months after birth. Fourteen children (28 eyes) of age-sex matched with the aphalic group were selected as normal control group. CCT and intraocular pressure (TOP) were measured postoperatively and the results were compared between groups. RESULTS: The mean CCT was 653.5 +/- 82.4 mu m in the aphakic group and 579.6 +/- 39.2 mu m in the control group, with a significant difference (P=0.000). The mean value of TOP in aphakic group (22.0 +/- 1.6mmHg) was greater than that of control group (16.9 +/- 2.1mmHg), P=0.023. There was a negative correlation between age and CCT in normal control group (r=-0.531, P=0.026), and there was no correlation in bilateral aphakia group (r=-0.324, P=0.165). CONCLUSION: Aphakic children due to congenital cataract surgery have a greater CCT than normal children. It is necessary to consider CCT in evaluating IOP for children after congenital cataract surgery.

Refractive surgery: the most cost-saving technique in refractive errors correction

AIM： To compare the lifetime and annual economic burden of spectacles, contact lenses, and refractive surgery in correction of refractive errors.METHODS： This is a cross-sectional study with convenience sampling which 120 patients were interviewed in a tertiary referral hospital in the Iranian health care system. The bottom-up based cost of illness approach was estimated using a face-to-face interview to assess the direct and indirect cost of different refractive errors correction of any correction technologies. RESULTS： Correction with spectacle imposes a total direct cost of US dollar （US$） 342.5 （±8.41） per year and US$9373.5 （±230.1） per lifetime to each patient. These figures for the contact lenses were obtained US$198.3 （±0.12） and US$5203.1 （±256.3） and for refractive surgery were obtained US$19.1 （±1.2） and US$568.1 （±64.6）, respectively. Overall, based on age-adjusted prevalence rates, astigmatism had the highest share of refractive errors economic burden with a lifetime direct cost of slightly less than US$5.49 billion, while hyperopia and myopia imposed less than US$5.24 and 4.2 billion on patients, respectively. The annually imposed cost on each individual Iranian patient with refractive errors is US$308.5. CONCLUSION： Based on 18mo post refractive surgery course observation, which is generalized to whole life, refractive surgery significantly imposed much less cost compared with spectacles and contact lenses. Refractive errors among Iranians result in considerable economic burden. Using the refractive surgery instead of other two correction methods has the ability to reduce this economic loss in the future.

Comparing corneal outcome between femtosecond laser-assisted cataract surgery and conventional phaco surgery in Fuchs’endothelial dystrophy patients:a randomized pilot study with 6mo follow up

AIM:To compare the corneal outcome in Fuchs’endothelial dystrophy(FED)patients between femtosecond laser-assisted cataract surgery(FLACS)and conventional phaco surgery(CPS).METHODS:This was a randomized controlled study comparing one eye surgery by FLACS and the contralateral eye operated by CPS(stop and chop technique)in FED patients.Central corneal thickness,corneal light backscatter,corneal densitometry,and central corneal endothelial cell count and hexagonality(noncontact endothelial cell microscope),and corrected distance visual acuity(CDVA)were assessed preoperatively and at day 1,40,and 180 postoperatively.RESULTS:Totally 31 patients(16 women)were included.At day 40 postoperatively,the mean endothelial cell loss(ECL)was 23.67%by FLACS and 17.30%by CPS(P=0.53).At day 180 postoperatively,ECL was 25.58%in FLACS and 21.32%in CPS(P=0.69).Densitometry data in all layers and all annuli from anterior layer to posterior layer in annuli 0-2,2-6,6-10 and 10-12,total densitometry with all layers and all annuli was performed.A significant difference was found in 6-10(posterior layer)at day 1 with-1.42 grayscale units(GSU;95%CI:-2.66 to-0.19,P=0.02).In 10-12(anterior layer,central layer and all layers)at day 40 were significant different with 7.7(95%CI:1.89 to 13.50,P=0.009),3.97(95%CI:0.23 to 7.71,P=0.03),4.73 GSU(95%CI:0.71 to 8.75,P=0.02),respectively.In the remaining parameters we found no difference between the two groups(P>0.05).Three CPS eyes suffered from corneal decompensation.CONCLUSION:There is no significant difference in corneal outcome between FLACS and CPS.Endothelial cell density and pentacam corneal outcome may be inadequate as outcome parameters in FED patients.

Optimal incision sites to reduce corneal aberration variations after small incision phacoemulsification cataract surgery

AIM： To analyze the effect of steep meridian small incision phacoemulsification cataract surgery on anterior,posterior and total corneal wavefront aberration.· METHODS： Steep meridian small incision phacoemulsification cataract surgery was performed in age-related cataract patients which were divided into three groups according to the incision site： 12 o＇clock, 9o＇clock and between 9 and 12 o＇clock（BENT） incision groups. The preoperative and 3-month postoperative root mean square（RMS） values of anterior, posterior and total corneal wavefront aberration including coma,spherical aberration, and total higher-order aberrations（HOAs）, were measured by Pentacam scheimpflug imaging. The mean preoperative and postoperative corneal wavefront aberrations were documented.·RESULTS： Total corneal aberration and total lower-order aberrations decreased significantly in three groups after operation. RMS value of total HOAs decreased significantly postoperatively in the 12 o＇clock incision group（P 〈0.001）. Corneal spherical aberration was statistically significantly lower after steep meridian small incision phacoemulsification cataract surgery in BENT incision group（P 〈0.05） and Pearson correlation analysisindicated that spherical aberration changes had no significant relationship with total astigmatism changes in all three corneal incision location.·CONCLUSION： Corneal incision of phacoemulsification cataract surgery can affect corneal wavefront aberration.The 12 o＇clock corneal incision eliminated more HOAs and the spherical aberrations decreased in BENT incision group obviously when we selected steep meridian small incision. Cataract lens replacement using wavefront-corrected intraocular lens combined with optimized corneal incision site would improve ocular aberration results.

Iris recognition:a biometric method after refractive surgery

Iris recognition,as a biometric method,outperforms others because of its high accuracy. Iris is the visible internal organ of human,so it is stable and very difficult to be altered. But if an eye surgery must be made to some individuals,it may be rejected by iris recognition system as imposters after the surgery,because the iris pattern was altered or damaged somewhat during surgery and cannot match the iris template stored before the surgery. In this paper,we originally discuss whether refractive surgery for vision correction(LASIK surgery) would influence the performance of iris recognition. And experiments are designed and tested on iris images captured especially for this research from patients before and after refractive surgery. Experiments showed that refractive surgery has little influence on iris recognition.

Human eye ocular component analysis for refractive state and refractive surgery

AIM： To analyze the clinical factors influencing the human vision corrections via the changing of ocular components of human eye in various applications; and to analyze refractive state via a new effective axial length.METHODS： An effective eye model was introduced by the ocular components of human eye including refractive indexes, surface radius（r1, r2, R1, R2） and thickness（t, T） of the cornea and lens, the anterior chamber depth（S1） and the vitreous length（S2）. Gaussian optics was used to calculate the change rate of refractive error per unit amount of ocular components of a human eye（the rate function M）. A new criterion of myopia was presented via an effective axial length.RESULTS： For typical corneal and lens power of 42 and 21.9 diopters, the rate function Mj（j=1 to 6） were calculated for a 1% change of r1, r2, R1, R2, t, T（in diopters） M1=＋0.485, M2=-0.063, M3=＋0.053, M4=＋0.091, M5=＋0.012, and M6=-0.021 diopters. For 1.0 mm increase of S1 and S2, the rate functions were M7=＋1.35, and M8=-2.67 diopter/mm, respectively. These rate functions were used to analyze the clinical outcomes in various applications including laser in situ keratomileusis surgery, corneal cross linking procedure, femtosecond laser surgery and scleral ablation for accommodation.CONCLUSION： Using Gaussian optics, analytic formulas are presented for the change of refractive power due to various ocular parameter changes. These formulas provide useful clinical guidance in refractive surgery and other related procedures.

Changes of lactate dehydrogenase in corneal edema after cataract surgery treated with trans-corneal oxygenation therapy

AIM:To investigate the changes in levels of the lactate dehydrogenase(LDH)enzyme in corneal edema after cataract surgery with trans-corneal oxygenation therapy.METHODS:This pre-post design study design conducted on 15 patients with corneal edema after cataract surgery and receiving trans-corneal oxygenation therapy.Tear sample(using Schirmer paper,from the inferior fornix of the conjunctiva)was carried out prior to trans-corneal oxygenation therapy,on the day 2(D2)and day 5(D5)postoperatively before and after trans-corneal oxygenation therapy.Visual acuity[VA(Log MAR)],corneal endothelial density,central corneal thickness(CCT),and coefficient of variation corneal endothelial(Co V)were recorded.The value of LDH was measured using ELISA.The difference in mean LDH value before and after trans-corneal oxygenation therapy,between two groups were analyzed using Wilcoxon signed rank test.RESULTS:There was a decrease in LDH tear concentration at D2(pre vs post:1127.54±497.09 vs 696.91±489.49;P=0.002)and D5(pre vs post:1064.17±677.77 vs 780.28±428.95;P=0.027)after trans-corneal oxygenation therapy as well as decrease in LDH concentration on the D2 compared to D5(P=0.041).The mean CCT was decreased significantly after the administration of trans-corneal oxygenation(pre vs post:632.10±25.66 vs 563.90±51.54;P=0.005).The mean VA and Co V increased significantly after the administration of trans-corneal oxygenation(P=0.001 and P=0.028,respectively).However,there was no difference in mean of corneal endothelial density(P=0.814).CONCLUSION:Trans-corneal oxygenation therapy is associated with significant decrease of tears LDH levels in post cataract surgery with corneal edema.It is accompanied by clinical improvement such as significant reduction of CCT.

Effect of femtosecond laser-assisted steepest-meridian clear corneal incisions on preexisting corneal regular astigmatism at the time of cataract surgery

AIM:To investigate the clinical efficacy and safety of femtosecond laser-assisted steepest-meridian clear corneal incisions for correcting preexisting corneal astigmatism performed at the time of cataract surgery.METHODS:This prospective case series study comprised consecutive age-related cataract patients with corneal regular astigmatism(range:+0.75 to+2.50 D)who had femtosecond laser-assisted steepest-meridian clear corneal incisions(single or paired).Corneal astigmatism was performed with the Pentacam preoperatively and 3 mo postoperatively.Total corneal astigmatism and steepestmeridian measured in the 3-mm central zone were used to guide the location,size and number of clear corneal incision.The vector analysis of astigmatic change was performed using the Alpins method.RESULTS:Totally 138 eyes of 138 patients were included.The mean preoperative corneal astigmatism was 1.31±0.41 D,and was significantly reduced to 0.69±0.34 D(equivalent to difference vector)after surgery(P<0.01).The surgically-induced astigmatism was 1.02±0.54 D.The correction index(ratio of target induced astigmatism and surgically-induced astigmatism:0.72±0.36)as well as the magnitude of error(difference between surgically-induced astigmatism and target induced astigmatism:-0.29±0.51)represented a slight under correction.For angle of error,the arithmetic mean was 1.11±13.70,indicating no significant systematic alignment errors.CONCLUSION:Femtosecond-assisted steepest-meridian clear corneal incision is a fast,customizable,adjustable,precise,and safe technique for the reduction of low to moderate corneal astigmatism during cataract surgery.

Evaluation of axial length/total corneal refractive power ratio as a potential marker for ocular diagnosis of Marfan’s syndrome in children

AIM:To investigate whether the axial length(AL)/total corneal refractive power(TCRP)ratio is a sensitive and simple factor that can be used for the early diagnosis of Marfan’s syndrome(MFS)in children.METHODS:The relationship between the AL/TCRP ratio and the diagnosis of MFS for 192 eyes in 97 children were evaluate.The biological characteristics,including age,sex,AL,and TCRP,were collected from medical records.Receiver operating characteristic(ROC)curve analysis was performed to investigate whether the AL/TCRP ratio effectively distinguishes MFS from other subjects.The Youden index was used to re-divide the whole population into two groups according to an AL/TCRP ratio of 0.59.RESULTS:Of 96 subjects(mean age 7.46±3.28 y)evaluated,56(110 eyes)had a definite diagnosis of MFS in childhood based on the revised Ghent criteria,41(82 eyes)with diagnosis of congenital ectopia lentis(EL)were included as a control group.AL was negatively correlated with TCRP,with a linear regression coefficient of-0.36(R2=0.08).A significant correlation was found between age and the AL/TCRP ratio(P=0.023).ROC curve analysis showed that the AL/TCRP ratio distinguished MFS from the other patients at a threshold of 0.59.MFS patients were present in 24/58(41.38%)patients with an AL/TCRP ratio of≤0.59 and in 34/39(87.18%)patients with an AL/TCRP ratio of>0.59.CONCLUSION:An AL/TCRP ratio of>0.59 is significantly associated with the risk of MFS.The AL/TCRP ratio should be measured as a promising marker for the prognosis of children MFS.Changes in the AL/TCRP ratio should be monitored over time.