Interface fluid syndrome caused by the corneal perforation injury after small incision lenticule extraction: a case report.

BACKGROUND: To report a case of interface fluid syndrome (IFS) following traumatic corneal perforation repair after small incision lenticule extraction (SMILE). CASE PRESENTATION: A 23-year-old woman, with a past history of SMILE, was struck in the left eye with a barbecue prod and subsequently underwent corneal perforation repair at local hospital. Primary wound repaired with a single 10 - 0 nylon suture at the area of leakage. After the surgery, her best corrected visual acuity (BCVA) was 20/30. Four days later, she presented at our hospital with blurred vision, and interface fluid syndrome (IFS) was diagnosed. Intraoperative optical coherence tomography (iOCT) was used to guide the resuturing of the corneal perforation in the left eye, followed by anterior chamber gas injection. At the first postoperative month, the BCVA was 20/25. The corneal cap adhered closely to the stroma, the surface became smooth. CONCLUSIONS: This case illustrates that any corneal perforation following lamellar surgery, including SMILE, may lead to IFS. It is crucial to consider the depth of corneal perforation, and intraoperative optical coherence tomography (iOCT) plays a unique role in the repair procedure.

Association of myopia and astigmatism with postoperative ocular high order aberration after small incision lenticule extraction.

OBJECTIVE: To investigate the correlation between higher-order aberrations (HOA) after small incision lenticule extraction (SMILE) and the severity of myopia and astigmatism, along with the relevant factors. These findings will provide valuable insights for decreasing the occurrence of HOA after SMILE and enhancing visual quality. METHODS: A total of 75 patients (150 eyes) with myopia and astigmatism who underwent SMILE were categorized into four groups based on the severity of myopia and astigmatism: Myopia Group 1 (Group M1, spherical diopter ranged from -1.00 D to -4.00 D), Myopia Group 2 (Group M2, spherical diopter ranged from -4.10 D to -10.00 D), Astigmatism Group 1 (Group A1, cylindrical diopter ranged from 0 D to -1.00 D), and Astigmatism Group 2 (Group A2, cylindrical diopter ranged from -1.10 D to -3.00 D). A comprehensive assessment was performed to examine the association between HOA and various relevant factors, including a detailed analysis of the subgroups. RESULTS: Group M1 had significantly lower levels of total eye coma aberration (CA), corneal total HOA (tHOA), internal tHOA, and vertical CA ( Z 3 - 1 ) after SMILE than Group M2 (P < 0.05). Similarly, Group A1 had significantly lower levels of total eye tHOA, CA, trefoil aberration (TA), corneal tHOA, TA, and vertical TA ( Z 3 - 3 ) after SMILE than Group A2 (P < 0.05). Pearson correlation analysis indicated a statistically significant positive relationship between the severity of myopia/astigmatism and most HOA (P < 0.05). Subgroup evaluations demonstrated a notable increase in postoperative HOA associated with myopia and astigmatism in Groups M2 and A2 compared with the control group. Lenticule thickness, postoperative central corneal thickness (CCT), postoperative uncorrected distance visual acuity (UDVA), and postoperative corneal Km and Cyl were strongly correlated with most HOA. Age, eyes, and postoperative intraocular pressure (IOP) were only associated with specific HOA. CONCLUSION: HOA positively correlated with the severity of myopia and astigmatism after SMILE. However, this relationship was not linear. HOA after SMILE was influenced by various factors, and additional specialized investigations are required to establish its clinical importance.

[Peripheral sterile corneal infiltrates after small incision lenticule extraction].

A 31-year-old female patient with refractive error in both eyes underwent small incision lenticule extraction. On the 4th day after surgery, arc-shaped peripheral corneal infiltrates appeared in the right eye. Tobramycin and dexamethasone eye drops, 0.3% gatifloxacin eye drops, and a corneal bandage lens were applied to the eye. After bacterial infection was ruled out, dexamethasone sodium phosphate was injected subconjunctivally near the corneal lesion. The symptoms improved and the corneal lesion subsided afterwards.

[Chinese expert consensus on the prevention and treatment of complications of laser corneal refractive surgery (2024)].

Laser corneal refractive surgery has been carried out in China for three decades. The safety, efficacy, predictability, and long-term stability of the surgery have been well established. In the past 10 years, with the wide use of small incision lenticule extraction (SMILE) and trans-epithelial photorefractive keratectomy (T-PRK), the number of corneal laser surgeries in China has increased significantly. Although severe postoperative complications are rare, there is still the possibility of complications. Once complications occur and are not treated in time and effectively, the visual acuity and visual quality of patients would be affected. Paying attention to preoperative risk factors, standardization of the surgery procedure, and timely diagnosis and treatment of postoperative complications can minimize the negative effects. Therefore, the Cornea Group of Ophthalmology Branch of Chinese Medical Association has organized experts and scholars in this field to establish a consensus on the prevention and treatment of complications in laser corneal refractive surgery, providing guidance for the related clinical work.

The dynamic changes and influencing factors of visual symptoms after small incision lenticule extraction.

BACKGROUND: To investigate the dynamic changes and influencing factors of visual symptoms after small incision lenticule extraction (SMILE). METHODS: This was a prospective observational study. Visual symptoms including glare, haloes, starbursts, hazy vision, fluctuation, blurred vision, double vision and focusing difficulties were evaluated before and 1, 3, 6 months after SMILE using a questionnaire. Generalized linear mixed models were used to assess the effects of preoperative characteristics and objective visual quality parameters on postoperative visual symptoms. RESULTS: 73 patients/146 eyes were enrolled. Preoperatively, the most common symptoms were glare (55% of eyes), haloes (48%), starbursts (44%) and blurred vision (37%). At 1 month postoperatively, the incidence and extent scores of glare, haloes, hazy vision and fluctuation rose significantly. At 3 months, the incidence and extent scores of glare, haloes and hazy vision restored to baseline. And at 6 months, the extent scores of fluctuation returned to baseline. Other symptoms (e.g., starbursts) did not change before and 1, 3, 6 months after SMILE. Preoperative visual symptoms were associated with postoperative symptoms, as patients with a symptom preoperatively had higher postoperative scores for that symptom. Age was related to postoperative extent of double vision (coefficient = 0.12, P = 0.046). There were no significant associations between postoperative visual symptoms and preoperative SE, scotopic pupil size, angle kappa (with intraoperative adjustment), postoperative HOAs or scattering indexes. CONCLUSIONS: The incidence and extent scores of hazy vision, glare, haloes and fluctuation increased at the first month after SMILE, and recovered to baseline at 3 or 6 months. Preoperative visual symptoms were associated with the postoperative symptoms and should be fully considered before SMILE.

The effects of programmed optical zones on achieved corneal refractive power with myopic astigmatism after small incision lenticule extraction (SMILE): a vector analysis.

PURPOSE: To evaluate the effects of different programmed optical zones (POZs) on achieved corneal refractive power (CRP) with myopic astigmatism after small incision lenticule extraction (SMILE). METHODS: In total, 113 patients (113 eyes) were included in this retrospective study. The eyes were divided into two groups according to POZ: group A (6.5, 6.6, and 6.7 mm, n = 59) and group B (6.8, 6.9, and 7.0 mm, n = 54). Fourier vector analysis was applied to evaluate the error values between the attempted and achieved corneal refractive power (CRP). Alpins vector analysis was used to calculate surgically induced astigmatism (SIA), difference vector (DV), magnitude of error (ME), and astigmatism correction index (ACI). Multivariate regression analysis was performed to assess potential factors associated with the error values. RESULTS: The error values in the group with large POZ were closer to zero, and significantly associated with the POZ at 2 and 4 mm of the cornea (ß = - 0.50, 95% confidence interval [CI] [- 0.80, - 0.20]; ß = - 0.37, 95% CI [- 0.63, - 0.10], P < 0.05, respectively). For the correction of astigmatism, the values of SIA, ME, and ACI were lower in group B than in group A (P < 0.05). The fitting curves between TIA and SIA were y = 0.83x + 0.19 (R2 = 0.84) and y = 1.05x + 0.04 (R2 = 0.90), respectively. CONCLUSIONS: Smaller POZs resulted in higher error values between the achieved- and attempted-CRP in the SMILE procedure, which should be considered when performing surgery.

[Corneal ectasia following small-incision lenticule extraction: a case report].

A 22-year-old male presented with complaints of blurred vision in his right eye over the past 2 years following small incision lenticule extraction (SMILE) surgery conducted 4 years ago. Following a thorough ocular examination and evaluation, he was diagnosed with corneal ectasia in the right eye after the SMILE procedure. Subsequently, the patient underwent corneal cross-linking (CXL) treatment in the right eye to prevent the progression of the condition. After 3 months of treatment, the corneal ectasia remained stable. This article outlines the process of diagnosis and treatment, reviews the corneal conditions prior to the SMILE surgery, and analyzes the possible reasons behind the occurrence of postoperative corneal ectasia.

Case Report: Bilateral Corneal Ectasia Developed during Pregnancy after Small-incision Lenticule Extraction.

SIGNIFICANCE: This case highlights that hormonal changes during pregnancy could affect the biomechanical stability of the cornea and lead to corneal ectasia during pregnancy after corneal refractive surgery. PURPOSE: We report an unusual case of bilateral corneal ectasia after small-incision lenticule extraction that developed during pregnancy. CASE REPORT: A 27-year-old woman experienced post-small-incision lenticule extraction corneal ectasia. Her pre-operative corneal topography was normal, with a minimum central corneal thickness of 538 µm in the right eye and 530 µm in the left eye. The manifest refraction was -7.75 -0.25 × 180 and -7.50 -0.75 × 10, and the lenticule thickness was 140 and 139 µm in the right and left eyes, respectively. After 11 months, in her first trimester, the patient began to experience gradually deteriorating blurred vision. Two years post-operatively, corneal ectasia was diagnosed based on topographic data. The automatic optometer examination was -7.25 -2.50 × 42 in the right eye and -11.00 -5.00 × 140 in the left eye. Later, the patient underwent corneal collagen cross-linking to control further progression and was recommended to wear rigid gas-permeable contact lenses. CONCLUSIONS: Surgeons should be alert for cornea ectasia after refractive surgery in pregnant patients, as hormonal changes during pregnancy may affect corneal biomechanical stability.

Risk factors for postlaser refractive surgery corneal ectasia.

PURPOSE OF REVIEW: To summarize newly reported and update previously known risk factors for post laser vision correction (LVC) corneal ectasia. RECENT FINDINGS: Advances in corneal topography and tomography have improved detection of preclinical ectasia-related changes. This has allowed for enhanced screening of surgical candidates. There are also known genetic predispositions for corneal ectasia, and recent genetic analyses have revealed various genes and inflammatory biomolecular markers related to corneal biomechanical integrity. Other models of risk assessment such as finite element biomechanical modeling and artificial intelligence tools have shown promise in detecting more subtle risk factors, such as those related to mechanical strain. SUMMARY: Risk factors for post-LVC corneal ectasia involve both surgery and patient-specific characteristics, such as topographic and tomographic abnormalities, younger age, thinner preoperative corneas, and residual stromal beds, high myopia, and higher percentage tissue altered. Preoperative risk stratification has helped to decrease the incidence of postoperative ectasia, a trend which will likely continue with advancements in analytic tools and better understanding of underlying genetic predispositions.

[Enhancing the management and control of perioperative infection in small incision lenticule extraction].

Small incision lenticule extraction (SMILE) has been widely used in the treatment of myopia and astigmatism due to its small incision (2 mm), without open corneal flap, rapid recovery of the ocular surface function and good comfort. However, it is the microincision and the potential cavity under the corneal cap that provide a suitable environment for microbial nourishment. In this article, the characteristics of SMILE and the particularity of postoperative infection are stated, and the key points of risk management and control during the period of operation as well as the principles of identification and treatment of infection after SMILE surgery are put forward, so as to enhance the perioperative preparation in SMILE and make sure of the safety and high quality for myopic eyes. (Chin J Ophthalmol, 2020, 56: 86-88).

Corneal crosslinking (CXL) with 18-mW/cm2 irradiance and 5.4-J/cm2 radiant exposure-early postoperative safety.

PURPOSE: To investigate safety of accelerated corneal crosslinking during the first postoperative month. METHODS: In this retrospective study, 76 eyes of 60 patients with verified progressive keratectasia were enrolled in this study and followed for 1 month after accelerated CXL (18 mW/cm2 for 5 min, radiant exposure 5.4 J/cm2) (A-CXL(5*18)). Preoperatively, objective refraction, slit lamp inspection, and corneal tomography were performed. Early postoperative slit lamp examinations were performed on days 1 and 4. At 1 month, objective refraction, slit lamp inspection, and corneal tomography were performed. RESULTS: Gender distribution was m:f = 55:21, OD:OS was 40:36, and the average age was 26.5 ± 8.6 years at surgery. Only 71 of the 76 eyes completed the 1-month follow-up, indicating a dropout rate of 6.6%. In 7.0% (n = 5), sterile infiltrates were observed; 5.6% of eyes (n = 4) showed delayed epithelial healing (> 4 days) in 2.8% (n = 2); an infection occurred and in 1 eye (1.4%), a stromal scar was detected; no other complications, neither a loss of two or more Snellen lines at 1 month postoperatively, were observed. As a risk factor for sterile infiltrates, thin preoperative pachymetry could be identified (p = 0.027). CONCLUSIONS: This study revealed no difference in early postoperative safety between CXL using 18 mW/cm2 and standard corneal CXL. Thinner preoperative pachymetry could be identified predicting a higher rate of postoperative sterile infiltrates.

Corneal thickness, residual stromal thickness, and its effect on opaque bubble layer in small-incision lenticule extraction.

PURPOSE: To evaluate the effects of the central corneal thickness (CCT) and residual stromal thickness (RST) on the formation of opaque bubble layer (OBL) during small-incision lenticule extraction (SMILE). METHODS: A total of 345 eyes from Refractive Surgery Center database at Tianjin Eye Hospital that had been subjected to SMILE surgery and followed for 6 months were included in this study and divided into OBL and OBL-free groups. Preoperative, intraoperative, and postoperative data for all eyes were evaluated and analyzed using multivariate regression analysis. After adjustment for several confounding factors, potential associations of CCT and RST with OBL were elucidated by determining odds ratios (ORs) and 95% confidence intervals (CIs). RESULTS: In total, 22 of the 345 eyes developed various degrees of OBL during the femtosecond laser scanning phase of SMILE surgery. After adjustment for age, sex, and refractive errors, significant relationships were detected between CCT and RST and OBL formation (OR 1.04; 95% CI 1.02-1.06; OR 1.03; 95% CI 1.02-1.05, respectively, P < 0.001). Smooth curve fitting revealed an increased risk of OBL in the presence of an increased CCT or RST. However, visual outcomes were comparable between the two groups at both 3 and 6 months postoperatively. CONCLUSIONS: The results suggest that OBL formation during SMILE surgery is more likely in eyes with a thicker cornea. CCT and RST can be considered independent risk factors for OBL formation. Although this phenomenon may disturb the surgical procedure, it is unlikely to affect the postoperative visual outcome.

U.S. Multicenter Clinical Trial of Corneal Collagen Crosslinking for Treatment of Corneal Ectasia after Refractive Surgery.

PURPOSE: To evaluate the safety and efficacy of corneal collagen crosslinking (CXL) for the treatment of corneal ectasia after laser refractive surgery. DESIGN: Prospective, randomized, multicenter, controlled clinical trial. PARTICIPANTS: One hundred seventy-nine subjects with corneal ectasia after previous refractive surgery. METHODS: The treatment group underwent standard CXL, and the sham control group received riboflavin alone without removal of the epithelium. MAIN OUTCOME MEASURES: The primary efficacy criterion was the change over 1 year of topography-derived maximum keratometry (K), comparing treatment with control groups. Secondary outcomes evaluated were corrected distance visual acuity (CDVA), uncorrected distance visual acuity (UDVA), manifest refraction spherical equivalent, endothelial cell count, and adverse events. RESULTS: In the crosslinking treatment group, the maximum K value decreased by 0.7 diopters (D) from baseline to 1 year, whereas there was continued progression in the control group (1.3 D difference between treatment and control, P < 0.0001). In the treatment group, the maximum K value decreased by 2.0 D or more in 14 eyes (18%) and increased by 2.0 D or more in 3 eyes (4%). The CDVA improved by an average of 5.0 logarithm of the minimum angle of resolution (logMAR) letters. Twenty-three eyes (32%) gained and 3 eyes (4%) lost 10 or more logMAR letters. The UDVA improved 4.5 logMAR letters. Corneal haze was the most frequently reported crosslinking-related adverse finding. CONCLUSIONS: Corneal collagen crosslinking was effective in improving the maximum K value, CDVA, and UDVA in eyes with corneal ectasia 1 year after treatment, with an excellent safety profile. CXL is the first approved procedure to diminish progression of this ectatic corneal process.

Enhancement after Small-Incision Lenticule Extraction: Incidence, Risk Factors, and Outcomes.

PURPOSE: To report the incidence, risk factors, and outcomes of enhancement after small-incision lenticule extraction (SMILE). DESIGN: Retrospective cohort study. PARTICIPANTS: Five hundred twenty-four eyes of 307 patients who underwent SMILE at Singapore National Eye Center between February 2012 and March 2016. METHODS: The data collected included patient age at primary SMILE, gender, race, preoperative and postoperative manifest refraction spherical equivalent (MRSE), preoperative and postoperative uncorrected distance visual acuity and corrected distance visual acuity, the occurrence of suction loss during the procedure, and the need for enhancement. All enhancements were carried out by performing an alcohol-assisted photorefractive keratectomy (PRK) procedure with application of mitomycin C (MMC). MAIN OUTCOME MEASURES: Incidence, prevalence, preoperative and intraoperative risk factors for enhancement, and outcomes after enhancement. RESULTS: The prevalence of enhancement was 2.7%, and 71.4% eyes had enhancement within 1 year of primary SMILE. The incidence of enhancement was 2.1% and 2.9% at 1 and 2 years, respectively. Age older than 35 years, preoperative MRSE more than -6.00 diopters (D), preoperative myopia more than 6.00 D, preoperative astigmatism more than 3.00 D, and intraoperative suction loss were significant risk factors for enhancement after SMILE after adjusting for all other covariates (odds ratios, 5.58, 4.80, 1.41, 3.06, and 2.14, respectively; P = 0.004, 0.021, 0.022, 0.002, and 0.020, respectively). In the patients who underwent bilateral SMILE, the first-operated eye had a marginal trend toward significance for enhancement (P = 0.054). There was no gender or racial difference. In the 14 eyes requiring enhancement, the uncorrected distance visual acuity before enhancement ranged from 20/80 to 20/25, and the mean attempted enhancement spherical equivalent was -0.50±0.86 D. The uncorrected distance visual acuity improved in most patients (92.9%) after enhancement. CONCLUSIONS: The 2-year incidence of enhancement after SMILE was 2.9%. Risk factors associated with enhancement included older age at SMILE procedure, greater preoperative MRSE, greater preoperative myopia, greater preoperative astigmatism, and the occurrence of intraoperative suction loss. Clinical outcomes of using PRK with application of MMC for enhancement were good.

[Limitations of SMILE (Small Incision Lenticule Extraction)]. / Grenzen von SMILE (Small Incision Lenticule Extraction).

Background SMILE is a relatively new technique to correct moderate and high myopia. The limits of SMILE are yet unknown. Methods Literature research using PubMed until October 1, 2016. Results/Discussion Recently presented axial 2D-strain-stress measurements indicate that the biomechanical impairment of the cornea after SMILE and LASIK is comparable. The difference in elastic moduli is statistically not different. The visual rehabilitation after SMILE takes significantly longer (weeks) compared to LASIK (days). The refractive success rate of SMILE is still not as good as that of LASIK (88 % vs. 95 % within ± 0.5 D) but SMILE has caught up during the past years. The problem of reoperations is not yet solved. Conclusion More technical and clinical improvements are required to make SMILE comparable to LASIK regarding success rate and patient convenience. The biomechnical argument pro SMILE has turned out to be weak. To achieve the improvements a commercially competing femtosecond laser would be of advantage.

[Three Years Follow-up Study after Refractive Small Incision Lenticule Extraction (SMILE) Using 500 kHz Femtosecond Laser in "Fast Mode"]. / Drei Jahre Nachbeobachtung nach refraktiver Small Incision Lenticule Extraction (SMILE) mit einem 500-kHz-Femtosekundenlaser im "Fast Mode".

Background The aim of this clinical trial was to check the results of laser built-in settings 3 years after ReLEx SMILE for moderate and high myopia in unselected "real life" patients. Patients and Methods 50 myopic eyes of 27 patients were called in for examination after 3 years. 25 of these eyes with a preoperative myopia under - 6D comprised the "moderate myopia subgroup". All surgeries were performed with the 500 kHz VisuMax® femtosecond laser (Carl Zeiss Meditec AG, Jena) in the "fast mode" setting. Results The spherical equivalent (SE) of the entire group changed from - 6.18 D (± 1.91) prior to surgery to - 0.18 D (± 0.39) 3 years later. The preoperative SE in the moderate myopia subgroup changed from - 4.71 D (± 0.94) to - 0.04 D (± 0.23). 14 % of 50 eyes gained one line and 22 % lost one line of CDVA. The regression between month 3 and 36 was 0.07D for the entire group and 0.06 D for the moderate myopia subgroup. There were no late side effects. Primary undercorrection was predominantly seen in eyes over - 6 D. Conclusion ReLEx SMILE shows remarkable stability over the entire range of myopias after 3 years, however primary undercorrection occurs predominantly in eyes of - 6.0 D, which necessitates nomogram adjustment.

[The clinical analysis of corneal interface fluid syndrome after Laser lamellar corneal refractive surgery].

Objective: To analysis, the clinical characteristics, refractive changes, and clinical treatment of interface fluid syndrome after laser lamellar corneal refractive surgery. Methods: During Dec. 2010 to Apr. 2016. In total 6 cases(9 eyes), 3 cases were bilateral, 3 cases were unilateral. Five patients were male and 1 was female. The age of the patients ranged from 20 to 29 years was (24.83±4.02) years. Six cases(9 eyes)of IFS were diagnosed at our hospital. The history and complete ophthalmic examination that include Slit-lamp examination, Slit-lamp photography, refraction, corneal thickness measurement, corneal endothelial cell counting, IOP, anterior segment OCT(AS-OCT), exams were recorded. Results: Post-lasik Primary open angle glaucoma was 2 eyes in 1 patient. 1 patient(1 eye)was Posner-Schlossmann Syndrome and 1 patient(1 eye)was iritis after femtosecond laser. Post-small incision lenticule extraction by steroid drops induced elevated IOP were 5 eyes in 3 patients. Slit-lamp exam indicated edematous corneal flap or cap, lamellar haze, interface fluids accumulation. AS-OCT showed obvious interface dark area. The corneal flap or cap thickening and wrinkles, IOP change, diopter myopic shift, Corneal thickening. Conclusions: IFS is a rare but serious complication after Laser lamellar corneal refractive surgery. The main causes are high intraocular pressure and/or dysfunction of corneal endothelium. For patients with high IOP after laser lamellar corneal refractive surgery, follow up should be observed closely. accurate diagnosis by OCT and corneal endothelial cell counting. Early diagnosis, accurate treatment, its prognosis is good. (Chin J Ophthalmol, 2017, 53: 847-854).

[Comparative analysis of corneal aberrations after intrastromal segments and MyoRing implantation using femtosecond laser in patients with keratoconus]. / Sravnitel'nyi analiz rogovichnykh aberratsii posle femtolazernoi implantatsii intrastromal'nykh segmentov i kolets pri keratokonuse.

AIM: to comparatively analyze corneal aberrations after intrastromal corneal segments (ICS) and MyoRing implantation using femtosecond laser in patients with stage II-III keratoconus (KC) by Pentacam examination. MATERIAL AND METHODS: We have operated on 135 patients (145 eyes) with stage II or III KC. Depending on surgical technique, all patients were divided into two groups. Group I consisted of patients with KC, who received optimized femtosecond laser-assisted MyoRing implantation, group II - of those, who received femtosecond laser-assisted ICS implantation. Depending on the stage of the disease, each group was further divided into two subgroups, for stage II and stage III KC, respectively. Before and after surgery, all patients underwent visometry, biomicroscopy, corneal topography, and corneal aberrations measurement under photopic and mesopic conditions on Pentacam. The follow-up period averaged 30 months (from 6 to 34 months). RESULTS: In both groups corneal aberrations significantly decreased after surgery, which was confirmed by an improvement in parameters of refraction and keratometry readings. CONCLUSION: Implantation of intrastromal MyoRings leads to a greater reduction in the total corneal aberration, higher-order aberrations under photopic and mesopic conditions, and spherical aberration under photopic conditions as compared to ICS in patients with stage III KC; a comparable reduction in the total corneal, higher-order, and spherical aberrations under photopic conditions as compared to ICS in patients with stage II KC; a comparable increase in spherical aberration under mesopic conditions as compared to ICS in patients with stage III KC.

Corneal biomechanical changes in eyes with small incision lenticule extraction and laser assisted in situ keratomileusis.

BACKGROUND: Evaluating the corneal biomechanical changes using the Ocular Response Analyzer and the Corvis ST in eyes with incision lenticule extraction (SMILE) and laser assisted in situ keratomileusis (LASIK). METHODS: This is a retrospective study that included 50 eyes equally divided into two groups. The first group included eyes that underwent SMILE procedure using VisuMax® 500 kHz laser system (Carl Zeiss Meditec, Jena, Germany) and the second group included eyes that underwent LASIK procedure using the EX500 Allegretto excimer laser platform (Wavelight GmbH, Erlangen, Germany). The Ocular Response Analyzer (ORA) and the Corvis ST (CST) measured the corneal biomechanical changes before and after the procedures. RESULTS: The ORA showed significant decrease of corneal hysteresis (CH) and corneal resistance factor (CRF) in both groups postoperatively. The percentage of change of CH and CRF were found to be significantly higher in group II. There was no significant difference in the IOP with the ORA and the CST pre and postoperatively in either group. Using CST, the deformation amplitude and HC peak distances increased significantly in both groups. It was also noted that the mean percentage of change of the deformation amplitude was nearly five times higher in group II than group I. CONCLUSION: Both LASIK and SMILE substantially decreased the corneal biomechanical properties with greater reduction in the LASIK group.