Preoperative Corneal Thickness Research Articles

Ciliochoroidal Detachment After Intrascleral Lens Fixation Using the Yamane Technique.

The purpose of this study was to compare the incidence of ciliochoroidal detachment (CCD) after intrascleral lens fixation using the Yamane technique and other vitrectomy procedures. This retrospective study evaluated patients who underwent intrascleral lens fixation using the Yamane technique at Hiroshima University Hospital between March 2023 and February 2024 and who could be followed up for at least one month. Patients who underwent vitrectomy for macular disease without air-fluid exchange comprised the control group. The frequency of CCD was compared using anterior segment optical coherence tomography imaging. Forty-five eyes of 45 patients (26 men and 19 women, mean age 70.8 years) were included. There were no significant differences in the population means or proportions between the intrascleral fixation and control groups for age, sex ratio, right-to-left eye ratio, preoperative visual acuity, preoperative intraocular pressure (IOP), ocular axis, and corneal thickness. The population mean of IOP on the day after surgery was significantly lower in the Yamane intrascleral fixation group (8.4 mmHg) than in the control group (11.5 mmHg) (P < 0.05). There was no significant difference in the population proportions of CCD on the day after surgery between the Yamane intrascleral fixation group and the control group. However, the CCD incidence was 20 eyes (80%) for the Yamane intrascleral fixation group and 12 eyes (60%) for the control group, which was higher in the intrascleral fixation group. There was no significant difference in population means of IOP or population proportions of CCD at one week and one month. There was no significant difference in population proportions of CCD on the day after surgery, although the CCD rate for the Yamane intrascleral fixation group was higher, and the population mean of the IOP was significantly lower. The Yamane technique assumedly lowered IOP because of the stress placed on the ciliary body. One week after the procedure, the IOP in the intrascleral fixation group normalized.

The Influence of Corneal Thickness on Surgically Induced Corneal Astigmatism Derived from Total Keratometry Measured by Anterior Segment Swept-Source OCT.

The purposeof the study was to explore the possible correlations between the anterior segment parameters derived from anterior segment swept-source optical coherence tomography (AS-SS-OCT) with the surgically induced corneal astigmatism (CSIA) calculated from total keratometry (TK) measured by AS-SS-OCT. Seventy-one eyes of 67 patients with age-related cataract who underwent phacoemulsification combined with intraocular lens implantation with 2.2-mm incision were included. The CSIA values were calculated from anterior keratometry (CSIAKant) and TK (CSIATK) measured by AS-SS-OCT, respectively. Hotelling's T2 test was used to evaluate the difference. The correlation of CSIA with various parameters derived from AS-SS-OCT was tested with the Spearman correlation coefficient. The centroid of CSIAKant and of CSIATK were 0.31 ± 0.55 D @ 54° and 0.41 ± 0.59 D @ 51°, with no significant difference (F = 1.283, p = 0.281, Hotelling's T2). The mean absolute CSIAKant and CSIATK were 0.58 ± 0.24 D and 0.65 ± 0.28 D. Spearman test showed that the magnitude of CSIAKant was negatively correlated with preoperative peripheral corneal thickness (PCT, p = 0.045) and the magnitude of anterior keratometry (p = 0.044). The magnitude of CSIATK was negatively correlated with preoperative central corneal thickness (CCT, p = 0.003) and preoperative PCT (p = 0.015). The increased thickness of the peripheral cornea is correlated with the decrease in the magnitude of the CSIA. The correlation we identified between the corneal thickness and the CSIA indicated that certain preoperative parameters should be considered for the prediction of CSIA for a more precise refractive outcome.

A Comparative Study of the Effect of Femtosecond Laser-Assisted Cataract Surgery on Corneal Astigmatism in Post-LASIK Eyes and Virgin Eyes.

To evaluate and compare the effect of femtosecond laser-assisted cataract surgery on corneal astigmatism in post-LASIK eyes and virgin eyes. Patients who underwent femtosecond laser-assisted cataract surgery were included in the study and categorized into two groups: Group A, consisting of patients with post-LASIK eyes, and Group B, consisting of patients with virgin eyes. Visual acuity, corneal astigmatism, and surgically induced astigmatism (SIA) were evaluated. Additionally, the correlation between SIA and preoperative corneal astigmatism, mean corneal curvature, and central corneal thickness was also analyzed. A total of 168 eyes were enrolled in this study, with 62 eyes in Group A and 106 eyes in Group B. Significant differences in corneal astigmatism and SIA were observed between the two groups in the early postoperative period following cataract surgery (P<0.05). However, there was no significant difference at 6 months postoperatively (P>0.05). Corneal astigmatism demonstrated an against-The-rule shift in both groups postoperatively. No significant correlation was identified between SIA and preoperative corneal astigmatism, corneal curvature or corneal thickness. Additionally, there was no significant difference observed between the two groups in terms of uncorrected distance visual acuity (UDVA) at 6 months postoperatively. The effect of femtosecond laser-assisted cataract surgery on corneal astigmatism in post-LASIK eyes and virgin eyes was different in the early postoperative period. However, there was no significant difference at 6 months postoperatively. The post-LASIK eyes exhibited a delayed recovery compared to the virgin eyes.

The association of pre-photorefractive keratectomy Schirmer-1 test value with postoperative corneal epithelial thickness, ocular surface discomfort, and visual acuity.

To investigate the association of pre-photorefractive keratectomy Schirmer-1 test value with post-photorefractive keratectomy central corneal epithelial thickness, ocular surface disease index score, and uncorrected distance visual acuity. Patients were categorized according to preoperative Schirmer-1 value: the normal Schirmer Group (n=54; Schirmer-1 test value, >10 mm) and the low Schirmer Group (n=52; Schirmer-1 test value, between 6 and 10 mm). We analyzed ablation depth, visual acuity, result of Schirmer-1 test (with anesthesia), tear film break-up time, ocular surface disease index score, central corneal epithelial thickness, and spherical equivalent refraction. We found significant differences between the groups in Schirmer-1 test value, tear film break-up time, and ocular surface disease index score, both preoperatively and postoperatively (p<0.001). The preoperative central corneal epithelial thicknesses of the two groups were similar (p>0.05). After photorefractive keratectomy, the Schirmer-1 test value and spherical equivalent refraction decreased in both groups (p<0.05), and ocular surface disease index scores and central corneal epithelial thickness values increased in the low Schirmer Group (p<0.001) but not in the normal Schirmer Group (p>0.05). The postoperative central corneal epithelial thicknesses of the low Schirmer Group were significantly higher than those of the normal Schirmer Group (p<0.001). Postoperative uncorrected distance visual acuity did not differ significantly between the two groups (p>0.05). In patients with low Schirmer-1 test values before photorefractive keratectomy, the corneal epithelium thickened and ocular surface complaints increased during the postoperative period. However, changes in the corneal epithelium did not affect the postoperative uncorrected distance visual acuity. To reduce postoperative problems on the ocular surface in these patients, we recommend that dry eye be treated before photorefractive keratectomy.

Predictability of the Achieved Lenticule Thickness in Keratorefractive Lenticule Extraction for Myopia Correction

Purpose: To assess the predictability between the SCHWIND ATOS femtosecond laser (SCHWIND eye-tech-solutions) read-out and achieved lenticule thickness measured using MS-39 anterior segment optical coherence tomography (ASOCT; CSO) at the corneal vertex at postoperative 1 day and 1 and 3 months of follow-up. Methods: This retrospective case series included 130 eyes of 65 consecutive patients who were treated with SmartSight (SCHWIND eye-tech-solutions) lenticule extraction. Sixty-four percent of patients were women with a mean spherical refraction of −4.98 ± 1.19 diopters (D) and mean astigmatism of 0.53 ± 0.64 D. The measurements were performed using AS-OCT with the Phoenix Software v 4.1.1.5. Lenticule thickness was obtained by the subtraction method between preoperative and postoperative total corneal thickness. Results: A lower reduction in central corneal thickness (CCT) compared to the laser read-out for all three follow-up visits can be observed. Essentially, the reduction in CCT was identical at 3 months versus 1 month. The reduction in CCT was lowest at postoperative 1 day. Examining the 1- and 3-month data (essentially equivalent), one can see a best fit of y = 0.94 x −7 µm. Conclusions: The reduction in CCT was stable from 1 month of follow-up. The stable reduction in CCT was −6% (−1.5% after accounting for design decisions) and −7 µm lower than the respective laser read-out. The findings are predictable, showing a certain level of the lenticules becoming slightly thinner than their respective laser read-outs. [ J Refract Surg . 2023;39(11):728–735.]

Evaluation of Endothelial Cell Density after Torsional Phaco-Emulsification in Patients with Pseudo-Exfoliation

Background The corneal endothelium is a single layer of hexagonal cells that do not have the ability to regenerate. The normal density of corneal endothelial cells in adults is approximately 2500 cells/mm² and it is reduced by about 0.6% a year. The endothelium performs an essential function of maintaining the hydration of the cornea. When the endothelial cells density is reduced to approximately 800cells/mm², it may lead to corneal decompensation causing corneal edema and loss of corneal transparency which disrupts vision. Aim of the Work The aim of this study is to compare pre-operative corneal thickness between normal subjects and subjects with pseudo-exfoliation and to determine the effects of phaco-emulsification surgery on corneal endothelial cell density in cataract patients with pseudo-exfoliation syndrome. Patients and Methods The type of study was case controlled study, at department of Ophthalmology at Ain Shams University hospitals. This study included 66 patients divided to two equal groups (33 each): study group: 33 patients with pseudo-exfoliation, control group: 33 patients with senile cataract without pseudo-exfoliation. Results We found that ECD loss was 11.42% in the study group and 8.11% in the Control group 4 weeks after surgery. Phaco time and used BSS values were significantly higher in patients with PXS but had no significant influence on endothelial cell loss. They also suggested that the corneal endothelium in PXS be vulnerable to cataract surgery. Conclusion Torsional mode phacoemulsification and IOL implantation provided a safe and favorable surgical outcome in patients with/without PXS. Torsional phacoemulsification led to significantly higher ECD loss in the PXS than that in the control group during the whole follow up period.

Effect of Keratoconus Stage and Classification Parameters on Deep Anterior Lamellar Keratoplasty Outcomes.

The aim of this study was to investigate the effect of the keratoconus (KC) stage according to the Amsler-Krumeich classification system and the parameters used in this classification on deep anterior lamellar keratoplasty outcomes. The preoperative KC stage was determined, and the presence of corneal scarring was noted. The preoperative and postoperative best-corrected visual acuity (BCVA), refractive error, mean central keratometry (K mean ) readings, topographic astigmatism, and minimum corneal thickness (CT) values were recorded. Intraoperative and postoperative complications were also noted. One hundred thirty-seven eyes (54 eyes in stage 3-83 eyes in stage 4) were included in the study. The mean follow-up period was 42.20 ± 24.36 months. There was no statistically significant difference between stage 3 and 4 KC groups for postoperative BCVA, K mean , CT, spherical equivalent, and topographic astigmatism values (each P value >0.05). The effect of preoperative BCVA, K mean , CT, and refractive error values on postoperative BCVA could not be demonstrated ( P = 0.264). In addition, no statistically significant correlation was found between postoperative and preoperative values (each P value > 0.05). Although intraoperative Descemet membrane perforation and postoperative early suture loosening were observed more frequently in stage 4 KC than in stage 3 KC, the 2 groups were statistically similar for these and other complications (each P value >0.05). The preoperative KC stage and the parameters used in classification are not useful in predicting postoperative deep anterior lamellar keratoplasty outcomes. The timing of the surgery should be planned with the awareness that the progression of the disease will not have a negative effect on outcomes.

Comparison Between Pulsed and Continuous Accelerated Corneal Cross-Linking Protocols.

To compare between two accelerated corneal cross-linking (A-CXL) protocols in the management of keratoconus (KC) as regard to the extent of corneal treatment. This retrospective, comparative study included patients having mild to moderate, progressive KC. The study population was divided into two groups; group 1 enrolled 103 eyes of 62 patients who received pulsed light A-CXL (pl-CXL) at a power of 30 mW/cm2 with an irradiation time of 4 minutes, while group 2 comprised 87 eyes of 51 patients who received continuous light A-CXL (cl-CXL) at a power of 12 mW/cm2 with an irradiation time of 10 minutes. Recordings of the central and peripheral demarcation line depths (DD), and the maximum (DDmax) and minimum (DDmin) DD, using anterior segment optical coherence tomography, were compared between the two studied groups one month after the treatment protocol. Treatment stability was also evaluated pre and postoperatively (one year following surgery) by comparing the refractive and keratometric outcomes in both groups. The differences between the preoperative corneal thickness (minimum and central) and the epithelial thickness measurements between both groups were not statistically significant. Although group 1 had slightly larger central DD (223.4 ± 62.3 um), DDmax (240.4 ± 61.8 um), and DDmin (201 ± 54 um) than those of group 2 (221.8 ± 37 um, 229.1 ± 38.4 um, and 212 ± 37.2 um, respectively), the differences between both groups' measurements were not statistically significant. Also, the two groups showed statistically insignificant differences regarding the subjective refraction and the average and maximum keratometry pre and postoperatively, denoting visual, refractive, and keratometric stability in both groups. Longer duration cl-CXL seems to be as effective as pl-CXL regarding both postoperative stability and the extent of corneal tissue penetration by the ultraviolet treatment.

Analysis of influencing factors of corneal edema after phacoemulsification for diabetic cataract.

The paper aimed to explore the influence factors of corneal edema after phacoemulsification for diabetic cataracts. For this aim, 80 patients (80 eyes) with senile cataracts who underwent phacoemulsification implantation in our hospital from August 2021 to January 2022 were included in this study, including 39 males (48.75%) and 41 females (51.25%), with an average age of 70.35±5.22 years. The OCT system during ophthalmology was used to capture corneal OCT images in the center of the cornea in real time before the phacoemulsification (the phacoemulsification probe just entered the anterior chamber after the balanced saline left the separated nucleus), at the end of phacoemulsification (when the phacoemulsification ultrasound probe was still in the anterior chamber and the perfusion pressure did not change compared with that in the previous step), at the end of perfusion aspiration (after the perfusion aspiration probe left the anterior chamber), and after surgery (after the watertight incision is closed). The corneal thickness was measured at each time point using Photoshop software. AL, curvature and ACD were measured using IOL-Master bio-measurement technology, and ACD referred to the distance between the front surface of the cornea and the front surface of the lens. Endothelial cell density was measured using CIM-530 non-contact mirror microscope. A handheld rebound tonometer was used to measure intraocular pressure and optical coherence tomography was used to assess the macular area of the fundus. Fundus photography was performed with a non-diffuse fundus camera. The results indicated that the preoperative corneal thickness was 514.35±29.62 μm, and the average corneal thickness at the end of the operation was 535.26±30.29μm, which was increased by 20.91±1.67 μm compared with that before operation (P<0.05), and the increase rate of corneal thickness was 4.07%. The corneal thickness of patients tended to increase with the increase in operation time and intraocular operation time (P<0.05). The distribution of corneal edema-related features showed that 42.50% of patients had persistent edema at the time of cataract surgery. The median onset time of corneal edema in the remaining patients was 5.44 years (1.96-21.35 years for 90% CR). The higher the nuclear hardness, the more severe the cataract, and the higher APT, EPT, APE, and TST (P<0.05). The older the patient, the higher the grade of cataract nucleus, and the higher EPT, APE, and TST, the greater the intraoperative corneal thickening (P<0.05). The higher the maximum area of endothelial cells, the greater the intraoperative corneal thickness increase, the lower the corneal endothelial cell density and the greater the intraoperative corneal thickness increase (P<0.05). It was concluded that postoperative corneal edema in phacoemulsification surgery for diabetic cataracts is closely related to intraocular perfusion pressure, nuclear hardness of lens, the density of corneal endothelial cells, the energy of phacoemulsification and duration.

The Accuracy of Flap Thickness and Diameter in LASIK Using a Femtosecond Laser.

To evaluate the resultant thickness of the WaveLight FS200 (Alcon Vision, LLC) created LASIK flap compared to intended thickness at the surgical visit, using the WaveLight EX500 (Alcon Vision, LLC) pachymeter and the resultant flap diameter compared to intended diameter. This single arm, prospective, single surgeon study assessed the accuracy of the intended flap thickness and diameter, after successful bilateral LASIK surgery. The WaveLight FS200 femtosecond laser was used to create all flaps with an intended thickness of 120 μm. Flap thickness was calculated by subtracting the stromal bed thickness after flap lift from the preoperative corneal thickness using the WaveLight EX500 on-board optical pachymeter. Flap diameter was determined using digital analysis. A total of 58 subjects (116 eyes) completed the study. The calculated mean flap thickness was 120.6 ± 9.0 μm (range 102 to 143 μm) using the EX500 pre- and post-flap pachymetry measurements. There was no statistically significant difference between the planned and achieved flap thickness (p > 0.05). The mean difference in flap diameter between planned and actual was 0.02 ± 0.05 mm. Corneal thickness measured by Pentacam at up to 2 months preoperatively versus EX500 just prior to surgery was similar, with EX500 measuring 2 μm less on average than the Pentacam. The results suggest that the WaveLight FS200 laser is reliable for LASIK flap thickness and diameter and accurately created flaps at the intended thickness and the intended diameter.

Evaluating the safety and efficacy of epi-off corneal cross-linking in patients with thin corneas due to keratectasia.

Corneal cross-linking (CXL) is a safe and effective procedure for slowing keratectasia progression in eyes with a corneal thickness of at least 400 µm. Limited research has evaluated the safety and efficacy of epi-off CXL in corneas thinner than 400 µm. To evaluate the safety and efficacy of CXL to slow keratectasia progression in eyes with <400 µm preoperative corneal thickness. Retrospective chart review. This retrospective chart review included 37 eyes who underwent epi-off, iso-osmolar riboflavin corneal CXL with a preoperative thinnest point of the cornea <400 µm and had at least 6-12 months of follow-up. Preoperative and postoperative uncorrected visual acuity, best-corrected visual acuity (BCVA), thinnest point of the cornea, flat keratometry, steep keratometry, maximum keratometry (Kmax), need for penetrating keratoplasty, and cases of endothelial failure were recorded. Data were collected at baseline and months 3, 6, 9, and 12 post-CXL. Following cross-linking, 18 eyes (47%) had improved BCVA, 13 (35%) had an unchanged BCVA, and 6 eyes (16%) had a worse BCVA (p = 0.05). The mean postoperative BCVA was 20/81 (0.61 LogMAR) compared to 20/121 (0.78 LogMAR) preoperatively (p = 0.06). Kmax decreased an average of 1.1 D at 3-month (p = 0.53) and 3.4 D at the furthest follow-up (p = 0.10). At the farthest follow-up, 22.7% of eyes had >1 D of Kmax steepening. No patients required keratoplasty and there were no cases of endothelial failure in the follow-up period. This research supports the safety and efficacy of epi-off, iso-osmolar CXL in eyes with <400 μm baseline corneal thickness with no patients requiring penetrating or endothelial keratoplasty, a trend toward improvement in BCVA, and Kmax flattening. In the future, prospective studies would be helpful to confirm these findings.

Detecting Subclinical Corneal Edema Using Corneal Thickness Mapping in Patients Presenting Fuchs Endothelial Corneal Dystrophy

To determine whether local corneal thickness changes observed with optical coherence tomography (OCT) can detect subclinical corneal edema in Fuchs endothelial corneal dystrophy (FECD). Retrospective cohort study. A series of patients presenting FECD who underwent cataract surgery alone (45 eyes) or with concomitant Descemet membrane endothelial keratoplasty (triple procedure; 117 eyes). The study reviewed medical records, collected the preoperative corneal thickness map and calculated the differences and ratio of corneal thickness measured at 5, 7, and 9 mm from the central corneal thickness. Area under the receiver operating characteristic curves (AUCs) were calculated and thresholds were selected to obtain a specificity of 90%. The median difference between 5- and 2-mm corneal thickness in the supra-nasal quadrant (∆5-2mmSN) was 38 µm (interquartile range 34-46) in the cataract group and 17 µm (2-38) in the triple procedure group (P < .001). The corneal thickness ratios of supra-nasal 5- to 2-mm (R5/2mmSN) and 7- to 2-mm (R7/2mmSN) were 1.07 (1.06-1.08) and 1.15 (1.13-1.17)] in the cataract group and 1.03 (1.00-1.06) and 1.09 (1.06-1.14) in the triple procedure group (P < .001). The probability of corneal edema was increased 7-fold with ∆5-2mm SN < 27 µm (AUC=0.76) and 9.4- and 7.4-fold with R5/2mmSN and R7/2mmSN < 1.045 (AUC=0.77) and 1.118 (AUC=0.76), respectively. Local changes in corneal thickness may be useful in detecting preclinical corneal edema, especially in patients with FECD undergoing cataract surgery.

Efficiency of Moria One-Use Plus Sub-Bowman’s Keratomileusis Head in Achieving Predicted Corneal Flap Thickness in Sub Bowmans Keratomileusis

Purpose: To evaluate the difference between predicted and resultant corneal flap thickness in Sub-Bowmans Keratomileusis using Moria One-Use Plus sub-Bowman’s keratomileusis head. Study Design: Interventional case series. Place and Duration of Study: Liaquat National Hospital, Karachi, from April 2019 to September 2019. Methods: Total 55 patients of either gender with age 20 to 45 years undergoing Sub-bowmans Keratomileusis (SBK) were included. Frequencies and percentages were computed for qualitative variables. Quantitative variables were presented as mean ± standard deviation. Student t-test, pair t test and ANOVA were used to compare the mean of resultant and predicted corneal flap thickness. Effect modifiers were controlled through stratification. Post stratification student t-test was again used to compare the mean of resultant and predicted corneal flap thickness. P-value ≤ 0.05 was considered significant. Results: The mean age was 26.83 ± 4.38. There was an insignificant differences in preoperative, intraoperative and corneal flap thickness of both eye with respect to gender (P &gt; 0.05). There was insignificant mean difference in preoperative and intraoperative corneal thickness (P &gt; 0.05) of both eye with respect to age group but significant mean difference in resultant flap corneal thickness seen with both age group (P &lt; 0.05). Significant difference was found in the flap thickness between the right and left eyes. The difference in the predicted and resultant flap thickness was statistically significant for right eye and insignificant for the left eye. Conclusion: With Moria microkeratome, accuracy of the flap can be predicted in SBK. It is a safe and effective method to achieve the desired results.

Descemet Stripping Automated Endothelial Keratoplasty in Thick Corneas.

Purpose: To evaluate the outcomes of Descemet’s Stripping Automated Endothelial Keratoplasty (DSAEK) in corneas > 820 microns in thickness. Methods: This retrospective study included 30 eyes of 30 patients who underwent DSAEK. Endothelial cell destiny (ECD) and corneal thickness were recorded before surgery and at 1 and 12 months postoperatively. Patients were divided into two groups (≤ 820 microns and > 820 microns) based on median preoperative corneal thickness. Linear regression analyses were used to investigate the correlations between ECD and preoperative corneal thickness. Results: Recipient corneal thickness (RCT) and postoperative central cornea thickness had a statistically significant difference 1 month after surgery (p = 0.03, p = 0.08, respectively). BCVA and ECD did not have a statistical difference in the two groups at 1 month and 12 months after DSAEK. Conclusions: BCVA, ECD and corneal thickness were similar at 12 months after DSAEK in thick corneas. DSAEK is a viable surgical option in thick corneas.

Simple method of measuring ocular rotation in supine position during small incision lenticule extraction.

To introduce a novel measurement method of static cyclotorsion in small incision lenticule extraction (SMILE) and to investigate the effect of preoperative parameters on cyclotorsion and the effect of cyclotorsion on postoperative outcomes. The medical records of 242 patients and 484 eyes who underwent SMILE surgery were retrospectively reviewed. Preoperative intraocular pressure, refractive error, and corneal thickness were investigated. Refractive values and visual acuity were measured at 1d, 1, 3, and 6mo. Ocular cyclotorsion in the supine position was measured by calculating the location and angle of the incision site of the cornea in the anterior slit photograph taken after surgery. Of the total 484 eyes in 242 patients, preoperative mean spherical equivalent (SE) was -4.10±1.64 D, and the mean astigmatism was -0.82±0.74 D. Uncorrected distance visual acuity (UCVA) and SE improved significantly after the surgery. Moreover, 219 (45.2%) eyes had excyclotorsion, 235 (48.6%) eyes had incyclotorsion, and 30 (6.2%) eyes had no torsion. The right eyes tended to be excyclotorted, and the left eyes tended to be incyclotorted (P<0.01). The mean cyclotorsion was 1.18°±3.69°, and the mean absolute value of cyclotorsion was 3.14°±2.26°. The range of cyclotorsion was 0.5°-11.4°. It was found that the smaller the preoperative sphere, the higher the amount of cyclotorsion (r=0.11, P=0.016). There was no significant association between the amount of cyclotorsion and preoperative astigmatism. There was no correlation between sex, preoperative corneal thickness, preoperative intraocular pressure, amount of cyclotorsion, and direction of cyclotorsion. The ratio of right eye excyclotorsion and left eye incyclotorsion on 1d was higher than that at 1, 3, and 6mo (all P<0.01). There was no difference between the 1, 3, and 6mo results in the right and left eyes (P=0.15, P=0.16, respectively). The newly devised ocular cyclotorsion measurement method can be used to evaluate ocular cyclotorsion after SMILE. Preoperative SE is associated with the amount of cyclotorsion, however, cyclotorsion doesn't have a significant effect on the results of SMILE surgery.

Predicting Corneal Improvement after Descemet Membrane Endothelial Keratoplasty for Fuchs Endothelial CornealDystrophy.

PurposeTo develop a model to predict corneal improvement after Descemet membrane endothelial keratoplasty (DMEK) for Fuchs endothelial corneal dystrophy (FECD) from Scheimpflug tomography.DesignCross-sectional study.ParticipantsForty-eight eyes (derivation group) and 45 eyes (validation group) with a range of severity of FECD undergoing DMEK.MethodsScheimpflug images were obtained before and after DMEK. Before DMEK, pachymetry map and posterior elevation map patterns were quantified by a special image analysis program measuring tomographic features of edema (loss of regular isopachs, displacement of the thinnest point of the cornea, posterior surface depression). Image-derived novel parameters were combined with instrument-derived parameters, and the relative influences of parameters associated with the change in central corneal thickness (CCT) after DMEK in the derivation group were determined by using a gradient boosting machine learning model. The parameters with highest relative influence were then fit in a linear regression model. The derived model was applied to the validation group. Correlations and agreement were assessed between predicted and observed changes in CCT.Main Outcome MeasuresPredictive power (R2) and mean difference between predicted and observed change in CCT.ResultsThe gradient boosting machine model identified 4 novel parameters of isopach circularity and eccentricity and 1 instrument-derived parameter (posterior surface radius); preoperative CCT was a poor predictor. In the derivation group, the model strongly predicted the change in CCT after DMEK (R2 = 0.80; 95% confidence interval [CI], 0.71–0.89) and the mean difference between predicted and observed change was, by definition, 0 μm. When the same 5 parameters were fit to the validation group, the model performed very highly (R2 = 0.89; 95% CI, 0.84–0.94). When the coefficient estimates from the derivation model were used to predict the change in CCT in the validation group, the predictive power was also high (R2 = 0.78; 95% CI, 0.68–0.88), and the mean difference was 4 μm (predicted minus observed).ConclusionsScheimpflug tomography maps of corneas with FECD can predict the improvement in CCT after DMEK, independent of preoperative corneal thickness measurement. The model could be applied in clinical practice or for clinical research of FECD.

Tomographic changes after corneal collagen cross-linking for progressive keratoconus - one-year follow-up study

Introduction/Objective. The aim of this study was to evaluate the outcome of corneal collagen crosslinking (CXL) in patients with progressive keratoconus. Methods. This retrospective single-centered interventional study included 52 eyes of 41 patients who underwent epithelium-off CXL procedure at the age &gt; 18 years. Corneal tomography data, uncorrected, and best spectacle-corrected distant visual acuity (UDVA and CDVA, respectively) were analyzed at baseline and postoperatively over the initial 12-month period. In addition, the natural course of corneal tomographic changes was demonstrated at one, three, six, nine, and 12 months after the CXL procedure. Results. At one year, mean UDVA improved significantly from 0.15 ? 0.22 (0.3 min ? logMAR ? 0 max logMAR) at baseline to 0.06 ? 0.09 logarithm of minimum angle resolution (logMAR) (0.1 min logMAR ? 0 max logMAR) (p = 0.024). Mean CDVA was 0.45 ? 0.39 0.45 ? 0.39 logMAR (0.8 min logMAR ? 0 max logMAR) at baseline and 0.06 ? 0.13 logMAR (1 min logMAR ? 0 max logMAR) at one year (p = 0.039). Maximum keratometry showed a significant flattening of 1.36 D ? 1.53 D (p = 0.0032) at one year after CXL. Minimum keratometry significantly decreased with a mean change of 1.15 ? 1.20 (p = 0.011). Mean anterior and posterior best fit sphere (ABFS and PBFS, respectively) remained stable during the entire follow-up period. Mean reduction of corneal thickness after CXL was 47 ? 61 ?m (p = 0.003). At one year, 29 (56%) eyes showed K max regression, 22 (53%) showed stabilization, and one (2%) showed progression. Spearman correlation coefficients were calculated to assess the correlation between difference in preoperative corneal thickness (CT), in posterior elevation corneal thickness (PECT), and minimum corneal thickness, ?CT (PECT ? minCT) and radius difference ?r (r1-r2). Spearman rs &gt; 0.3 proved statistical significance and correlation. Conclusion. In our study, CXL effectively prevented progression of keratoconus in 98% of eyes at one year, while improving visual acuity. The effect of CXL can be evaluated at the earliest after six months; at that time, the stability of the corneal shape was provided by following the CXL procedure. The main limitation of this study is the small number of patients included.

Preliminary Characterization of Predictive Factors of the Visual Change after Epi-On and Epi-Off Corneal Collagen Crosslinking Techniques.

Purpose To investigate the potential predictive factors of the visual change achieved with accelerated epi-on and epi-off corneal collagen crosslinking (CXL) in keratoconus. Methods This retrospective comparative study analyzed 67 eyes treated with an accelerated epithelium-on (epi-on group) and epithelium-off (epi-off group) CXL. The clinical outcomes were evaluated and compared during a 1-year follow-up. Likewise, the relationship of the change achieved with both CXL techniques in the corrected distance visual acuity (CDVA) with different preoperative data was investigated. Results The mean CDVA change at 3 months postoperatively was −0.04 ± 0.19 and −0.07 ± 0.25 in the epi-on and epi-off groups, respectively (p = 0.809). In the epi-on group, this change was significantly correlated with the preoperative apical (r = −0.375, p = 0.045) and central corneal thickness (r = −0.402, p = 0.031). In the epi-off group, the CDVA change was significantly correlated with not only the preoperative apical (r = 0.402, p = 0.028) and central corneal thickness (r = 0.367, p = 0.046) but also with some topometric and aberrometric indices (r ≤ −0.374, p ≤ 0.042). Furthermore, the change in CDVA in the epi-on group could be predicted from age, preoperative refractive astigmatism J45 component, anterior corneal asphericity, and posterior corneal high order aberration root mean square (p = 0.002, R2 = 0.503). In the epi-off group, the CDVA change could be predicted from the preoperative minimum corneal thickness and magnitude of the vertical anterior corneal primary coma component (p = 0.001, R2 = 0.446). Conclusions Clearly, different predictive factors of the visual change induced with the accelerated epi-on and epi-off CXL techniques are present, suggesting a different mechanism of action for stiffening the cornea and inducing changes in this structure.

Bowman's layer transplantation in advanced keratoconus; 18-months outcomes.

To assess the outcome of isolated Bowman's layer transplantation (BLT) in advanced keratoconus in the patients not suitable for ultra violet cross-linking and intra stromal corneal ring segments. Nonrandomized Quasi-Experimental. Mid corneal stromal dissection followed by implantation of manually isolated bowman layer from a donor into the recipient stromal pocket was performed in the Department of Ophthalmology Khyber Teaching Hospital Peshawar from September 2018 to October 2018 and followed up over 18months. Eleven eyes of 11 patients, 8 male and 3 female within the age range of 7-28years with progressive keratoconus went under BLT All keratometry values decreased after surgery. Mean anterior pre-operative SimK changed from 69.05 ± 10.85D to 61.14 ± 6.23D at 18months post-operatively (P = 0.005). Means pre-operative Kmax value decreased from 77.24 ± 7.58D to 71.07 ± 5.37D at 18months post-operatively (p = 0.060). The mean pre-operative posterior keratometry value changed from - 10.03 ± 0.88 to - 8.96 ± 1.06D at 18months post-operatively (P = 0.002). Mean pre-operative thinnest corneal thickness increased from 281.64 ± 196.86um to 355.27 ± 19.17um at 18th months post-operatively (P = 0.001). Pachymetry p-value pre-operative to 18months (P = 0.001) was statistically significant. Mean anterior SimK at 6months post-operatively, 60.55 ± 5.56D changed to 61.14 ± 6.23D at 18months post-operatively (P = 0.000), Kmax at 6months postoperative 71.60 ± 5.01D changed to 71.07 ± 5.37D at 18months post-operatively (P = 0.008). Both anterior K values at 6months and 18months post-operatively showed less significant change, and the same was true for Kmax data at 6months and 18months post-operatively. P-values at 6months to 18months post-operatively for cornea back data remained (P = 0.001) unchanged. No complications were observed intra-operatively or post-operatively. Bowman layer transplantation is a unique surgical treatment for advanced keratoconus to stabilize progressive ectasia with fewer complications avoiding the need for penetrating or deep anterior lamellar keratoplasty.

Effects of long‑term soft contact lens wear on corneal epithelial thickness after small incision lenticule extraction

The present study investigated changes in corneal epithelial thickness after small incision lenticule extraction (SMILE) in patients with long-term preoperative soft contact lens (SCL) wear, the impact of SCL wear on the efficacy of surgical outcomes and the effects of long-term SCL wear on postoperative corneal aberrations. Patients were assigned to three groups according to the duration of SCL wear: Group A, the non-SCL-wearing group; group B, those with SCL wear ≤1 year; and group C, those with SCL wear >1 year. Epithelial thickness was recorded in nine zones by anterior segment optical coherence tomography across a 5-mm diameter before surgery and at 1 week, and 1, 3 and 6 months post-surgery. Corneal epithelial thickness and corneal aberrations among the three groups were compared, as well as the effects of changes in corneal epithelial thickness on postoperative visual acuity and manifest refraction. No significant differences were noted with regard to age or preoperative spherical equivalent among groups A (22 eyes), B (17 eyes) and C (18 eyes). Preoperative corneal epithelial thickness in the inferonasal, inferior and inferotemporal zones was thinner in group B compared with that in group A, and corneal epithelial thickness was thinner in all nine zones in group C compared with that in group A (P<0.05). At all follow-up time points, in the central, nasal, inferonasal, inferior, inferotemporal and temporal areas, the epithelial thickness was thinner in group C compared with that in group A (P<0.05). At 3 months postoperatively, the epithelial thickness was thinner in the inferonasal and inferior sectors in group C compared with that in group B (P<0.05), and at 6 months postoperatively, the epithelial thickness in the inferior region was thinner in group C compared with that in group B (P<0.05). There were no significant differences in visual acuity or manifest refraction among the three groups at all postoperative time points. The total higher-order aberrations were greater in group C compared with those in group A for all time points (P<0.05) and were greater in group C at 1 and 3 months postoperatively compared with those in group B (P<0.05). The spherical aberrations at 3 and 6 months postoperatively were greater in group C compared with those in group A (P<0.05). The coma aberrations were greater in group C compared with those in groups A and B for all time points (P<0.05). In conclusion, long-term SCL wear will result in corneal epithelial thinning, which does not impact visual acuity or manifest refraction after SMILE.