Postoperative Corneal Topography Research Articles

Explore the safety and efficiency of mild myopia retention in patients with myopia and presbyopia

Objective: To explore the corrective effects of a personalized corneal refractive surgery design that retains mild myopia in patients over 40 years old with refractive errors and presbyopia. Methods: A retrospective case series study was conducted, including 60 patients (120 eyes) over 40 years old who underwent corneal refractive surgery at Peking Union Medical College Hospital l from January 2023 to December 2023. The patients were divided into two groups based on their preference: Group A (retained mild myopia) and Group B (fully corrected), with 30 patients (60 eyes) in each group. Preoperative and postoperative visual acuity, subjective refraction, slit-lamp examination, corneal topography, and intraocular pressure were assessed at 1 day, 1 week, 1 month, 3 months, 6 months, and 12 months after surgery. The effectiveness and safety indices were calculated based on visual acuity before and after surgery. The National Eye Institute Refractive Quality of Life questionnaire was used to evaluate patient satisfaction and postoperative visual symptoms. Results: There were no significant differences in preoperative uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), spherical equivalent (SE), corneal thickness, and intraocular pressure between the two groups (all P>0.05). At the final follow-up, the proportions of eyes with UDVA≥0.8 and≥1.0 were 93.3% (56/60) and 60.0% (36/60) in Group A, and 100% (60/60) and 83.3% (50/60) in Group B, respectively. The SE was significantly different between Group A [(-0.35±0.52) D] and Group B [(-0.07±0.55) D] (P<0.05). Near visual acuity was better in Group A than in Group B (P<0.05). The effectiveness indices were 0.96±0.23 and 0.99±0.12, and the safety indices were 1.02±0.11 and 1.02±0.07 for Groups A and B, respectively. Both groups had high overall satisfaction, but Group A had higher scores for near vision, reading, and computer screen viewing. Conclusion: The personalized corneal refractive surgery design that retains mild myopia provides good corrective effects for patients over 40 years old with refractive errors, improving patient satisfaction and quality of life.

Sequential Customized Therapeutic Keratectomy in Patients With a History of Radial Keratotomy

Purpose: To evaluate the outcome of sequential customized therapeutic keratectomy (SCTK) in reducing higher order aberrations (HOAs) and improving quality of vision in highly aberrated corneas consequent to previous radial keratotomy (RK). Methods: A retrospective review of patients undergoing SCTK treatment from January 2012 to October 2020 was conducted in the Eye Center, Humanitas Clinical and Research Center (Rozzano, Italy). Indications for treatment in patients who had RK were significantly and/or progressively reduced corrected distance visual acuity (CDVA) combined with visual symptoms critically affecting quality of life. Preoperative and postoperative CDVA, corneal topography and aberrometry, Scheimpflug tomography, and anterior segment optical coherence tomography were registered. Results: Thirty-four patients who underwent RK a mean of 26.62 ± 7.10 years before SCTK treatment were included. SCTK induced a significant improvement of CDVA from 0.44 ± 0.82 logMAR preoperatively to 0.15 ± 0.64 logMAR postoperatively ( P &lt; .001). No patient experienced worsening of CDVA, whereas 8 patients (23,50%) gained one line and 23 patients (67.65%) gained two lines or more. A significant decrease in corneal coma, trefoil, and spherical aberrations was also noted ( P = .003, .003, and .004, respectively). Conclusions: SCTK proved to be a safe and effective option to treat highly aberrated eyes following RK. The authors suggest the use of SCTK as a first-line approach for the treatment of HOAs after RK and avoiding more invasive procedures such as corneal transplantation or intraocular lens implantation. [ J Refract Surg . 2023;39(12):808–816.]

MCSTransWnet: A new deep learning process for postoperative corneal topography prediction based on raw multimodal data from the Pentacam HR system

This work provides a new multimodal fusion generative adversarial net (GAN) model, Multiple Conditions Transform W-net (MCSTransWnet), which primarily uses femtosecond laser arcuate keratotomy surgical parameters and preoperative corneal topography to predict postoperative corneal topography in astigmatism-corrected patients. The MCSTransWnet model comprises a generator and a discriminator, and the generator is composed of two sub-generators. The first sub-generator extracts features using the U-net model, vision transform (ViT) and a multi-parameter conditional module branch. ​The second sub-generator uses a U-net network for further image denoising. The discriminator uses the pixel discriminator in Pix2Pix. Currently, most GAN models are convolutional neural networks; however, due to their feature extraction locality, it is difficult to comprehend the relationships among global features. Thus, we added a vision Transform network as the model branch to extract the global features. It is normally difficult to train the transformer, and image noise and geometric information loss are likely. Hence, we adopted the standard U-net fusion scheme and transform network as the generator, so that global features, local features, and rich image details could be obtained simultaneously. Our experimental results clearly demonstrate that MCSTransWnet successfully predicts postoperative corneal topographies (structural similarity ​= ​0.765, peak signal-to-noise ratio ​= ​16.012, and Fréchet inception distance ​= ​9.264). Using this technique to obtain the rough shape of the postoperative corneal topography in advance gives clinicians more references and guides changes to surgical planning and improves the success rate of surgery.

Accuracy of Astigmatism Calculation with the Barrett, Panacea, and enVista Toric Calculators.

To evaluate residual refractive astigmatism using the Panacea and enVista toric calculators, compared to the gold-standard Barrett toric calculator. A retrospective and comparative study was conducted in one center. We reviewed the medical records of all patients with a diagnosis of senile cataracts and regular corneal astigmatism, without previous corneal or intraocular surgery, who underwent phacoemulsification with implantation of a toric intraocular lens, who had pre- and postoperative corneal topography, biometry, and refraction measurements. The frequency of preoperative astigmatism according to the axis was 70 (84%) eyes showing with-the-rule (WTR) astigmatism, 9 (14%) eyes with against-the-rule (ATR) astigmatism, and 1 (2%) eye with oblique astigmatism. Regarding astigmatism prediction errors, there were statistically significant differences between the enVista and Panacea calculators (median of 0.39, 0.18, and 0.52 for Barrett, enVista, and Panacea, respectively). The residual astigmatism prediction error centroid was similar for the Barrett and enVista toric calculators, and both were lower compared to the Panacea calculator (x-component p < 0.001). The enVista toric calculator incorporating the Emmetropia Verifying Optical (EVO) toric calculator provides similar results to the gold-standard Barrett calculator.

The Effects of Blepharoptosis Surgery on Meibomian Gland, Tear Film, and Corneal Topography.

The objective of this study was to evaluate the Meibomian gland (MG), tear film, and corneal changes in the post-operative period following ptosis surgery using corneal topography. This non-comparative, case series study analyzed 30 eyes of 23 patients undergoing blepharoptosis surgery with an external approach. Ocular surface and tear film evaluation was performed at baseline and post-operative 3rd month. The corneal topography was used to assess the MG, the noninvasive tear film break-up time (NI-TBUT), K values, astigmatism, and corneal aberrations. For the examination of dry eyes, the I-TBUT, Schirmer, and ocular surface disease index (OSDI) questionnaires were also performed. The study involved patients with a mean age of 55.1±18.11 years. Postoperatively, marginal reflex distance 1 is significantly increased (1.23±1.09 vs. 3.65±0.65; p=0.001). Results revealed no significant changes in Kmean (43.65±1.15 vs. 43.67±1.14; p=0.727), astigmatism (-1±0.74 vs. -0.99±0.68; p=0.910), and corrected distance visual acuity logMAR (0.09±0.1 vs. 0.07±0.11; p=0.497). There was a significant increase in MG loss area postoperatively (5.02±5.04-7.75±6.75; p=0.047), while the degree of MG loss did not significantly change (0.2±0.48 vs. 0.37±0.56; p=0.132). However, no significant differences were detected in Schirmer I test (17.4±4.7 vs. 16.1±5.5; p=0.711), I-TBUT (12.4±3.1 vs. 11.9±4.7; p=0.483), and OSDI questionnaire score (16.7±9.4 vs. 17.9±10.3; p=0.176) between baseline and post-operative measurements. Similarly, no significant changes were found in NI-TBUT (5.73±3.72 vs. 6.58 4.71; p=0.535) and NIAvg-TBUT (6.06±4.8 vs. 7.51±4.43; p=0.322) values. Surgical correction of blepharoptosis affects MG morphology without causing dry eye at the 3rd month. Post-operative corneal topography is useful in demonstrating changes in the MG.

Effect of Pterygium Removal Combined with Conjunctival Autograft on Corneal Parameters in Swept-Source Imaging.

Background: Both pterygium ingrowth and excision determine alterations in corneal topography. The aim of this study was to evaluate the influence of pterygium removal combined with conjunctival autografts in addition to the use of human fibrin tissue glue on changes in corneal parameters as measured by 3-D swept-source anterior segment optical coherence tomography (AS-OCT) imaging. Methods: Sixteen eyes (16 patients) with pterygium that qualified for surgical treatment were enrolled in this study. Eye examination, slit lamp, and 3-D AS-OCT (CASIA 2) assessment were performed before the surgery and 7 days, 1 month, and 6 months after pterygium excision. Topographic parameters of both anterior and posterior surfaces of the cornea were analysed at each follow-up visit. Results: The gradual decrease in total astigmatism power from preoperative median 2.75 (6.15) D to 1.2 (1.1) D at 6-month follow-up (p = 0.034) was noted from the day 7 visit. Values were strongly influenced by variations of anterior cornea astigmatism. In contrast, a gradual total HOA reduction at the 1-month (from median 0.79 (1.3) D to 0.44 (0.27) D; p = 0.038) and at 6-month visits (0.25 (0.09); p = 0.001) was observed. Similarly, values were strongly influenced by variations of the anterior. Additionally, total average keratometry values increased from preoperative 44.05 (2.25) D to 44.6 (1.9) (p = 0.043) 1 month after the surgery. Conclusions: Significant steepening of the anterior cornea and a reduction in both astigmatism and HOA were observed after pterygium excision. The anterior corneal surface was an essential component of the total postoperative corneal topography values. Three-dimensional swept-source AS-OCT imaging seems to be a valuable tool for monitoring both the progression of the disease and postoperative effects in pterygium eyes.

Effect of Opposite Clear Corneal Incision (CCI) on Corneal Higher-Order Aberrations after Phacoemulsification

Abstract Background: Nowadays, care of a cataractous patient greatly exceeds surgical removal of the opacified lens. In a step foreword to welfare of the elderly, phacoemulsification can perform as a refractive tool, addressing both spherical and astigmatic refractive errors. Aim of Study: The aim of that work was to evaluate safety and effectiveness of OCCIs, as an innovative procedure for correction of corneal astigmatism, during phacoemulsification. Patients and Methods: The study assessed 64 patients, who underwent phacoemulsification. Pre-operative and post-operative corneal topography was done, documented and statistically analyzed for each patient. Results: The study revealed a decrease of pre-operative corneal astigmatism from a pre-operative mean of –1.78D to a post-operative mean of 1.09D in OCCI group and a decrease of pre-operative corneal astigmatism from a pre-operative mean of –1.71D to a postoperative mean of 1.29D in single incision group. Conclusion: The present study revealed that OCCIs with appropriate pre-operative corneal topography represent a real advance in the applications of refractive lenticular surgery. OCCIs provide an innovative technique for managing pre-operative, regular, corneal astigmatism. This is simple, easy to learn technique, with no extra instrumentation. The OCCIs in this study was safe, with no wound related complications. However, OCCIs require careful early post-operative care, due to their penetrating nature. Once the wounds are sealed, risk of further complications approaches zero. Further studies on that technique, employing different incision architecture are required to help development of nomograms correlating the incision length, width, age of the patient, and the amount of pre-operative corneal astigmatism to be corrected.

Sutureless Intrascleral Posterior Chamber Intraocular Lens Fixation: Analysis of Clinical Outcomes and Postoperative Complications.

Purpose To report a technique for performing sutureless intrascleral fixation of a posterior chamber intraocular lens (PC-IOL) and analyzing the clinical outcomes and postoperative complications. Study Design. 68 eyes of 66 patients who received the technique were studied retrospectively. Methods The best-corrected visual acuity (BCVA), intraocular pressure (IOP), anterior chamber depth (ACD), IOL tilt and decentration, corneal topography (K1 and K2), and postoperative complications were determined at 3 months. Results The mean preoperative BCVA was 1.63 ± 1.24 logMAR units, and the mean postoperative BCVA was 0.74 ± 0.59 logMAR units at 3 months (P < 0.05). The mean preoperative IOP was 21.9 ± 12.6 mmHg, and the mean postoperative IOP was 16.9 ± 4.5 mmHg at 3 months (P = 0.001). The mean preoperative corneal topography (K1 and K2) was K1 = 42.14 ± 1.91 and K2 = 43.54 ± 1.51; the mean postoperative corneal topography (K1 and K2) was K1 = 43.03 ± 2.18 and K2 = 43.40 ± 1.71 at 3 months (P = 0.678 and 0.468, respectively). The mean preoperative spherical equivalent was +11.00 ± 13.19 diopters (D), and the mean postoperative spherical equivalent was +0.06 ± 0.86 D (P < 0.005). The mean IOL tilt was 2.4 ± 1.7°, and the mean decentration was 0.35 ± 0.21 mm. The mean ACD was 4.31 ± 0.29 mm. Conclusions The 27-gauge sutureless intrascleral PC-IOL implantation technique minimizes intraoperative injury, simplifies procedure, and provides good PC-IOL fixation with few postoperative complications.

A novel Q-value-based nomogram for single intracorneal ring segment implantation versus standard manufacturer's nomogram combined with accelerated cross-linking for treatment of keratoconus: a randomized controlled trial.

PurposeTo compare the efficacy of implanting a single Keraring segment according to a novel Q‐value‐based nomogram (QN) to that of segment implantation according to the manufacturer's standard nomogram (SN), for keratoconus treatment.MethodsThis was a prospective, randomized controlled trial of 104 patients (104 eyes) with Amsler‐Krumeich grade 1 or 2 keratoconus, and type 1 or 2 cone asymmetry determined according to manufacturer's classification. They were randomly distributed into two groups: group A patients (n = 52) underwent Keraring implantation according to the SN, and group B patients (n = 52) underwent implantation of a single (210° arc‐length) Keraring segment according to the QN. Both treatments were combined with accelerated transepithelial cross‐linking, and follow‐up was 6 months. Main outcome measures were preoperative and postoperative visual acuity, subjective refraction and corneal topography.ResultsAt postoperative month 6, group B exhibited statistically significantly higher values of mean uncorrected distance visual acuity (UDVA), sphere, K2, K‐average, K‐max and Q‐anterior (p = 0.02, 0.01, 0.002, 0.001, 0.0001 and 0.03, respectively) compared to that of group A. However, group A exhibited better refractive cylindrical improvements (p = 0.04). In group A, we documented spontaneous extrusion of one Keraring segment.ConclusionSingle 210° arc‐length segment implantation using our objective QN was more efficacious for keratoconus treatment than using the subjective SN. The nomograms were comparable when the Q‐anterior value was >−1.00; however, the QN was superior to the SN when the Q‐anterior value was ≤−1.00. The QN yielded greater postoperative UDVA and smoother corneal remodelling than did the SN for treatment of grade 1 and 2 keratoconic eyes.

The Influence of Ultrasound Ciliary Plasty on Corneal Parameters.

To assess the postoperative corneal topography for 1 year after UCP. In total, 78 patients with primary and secondary refractory glaucoma were enrolled in the study. The primary outcome measures were the corneal parameters obtained with anterior segment swept-source optical coherence tomography. Intraocular pressure, number of antiglaucoma medications, and best-corrected logMAR visual acuities were analyzed as secondary outcome measures. Measurements were performed preoperatively and at 1 week, and 1, 3, 6, and 12 months postoperatively. A total of 39 patients (39 eyes) completed the follow-up period of 12 months. There was a significant difference in the anterior/posterior steep/flat keratometry and anterior/posterior astigmatism values immediately after UCP. However, 3 months postoperatively these parameters returned to their initial values and there were no significant differences noted. The mean±SD values of anterior astigmatism preoperatively and at 1 week, and 1, 3, 6, and 12 months postoperatively were 1.12±0.66 D, 2.17±0.91 D (P<0.001), 2.05±0.93 D (P<0.001), 1.55±0.75 D (P=0.004), 1.31±0.70 D (P=0.024), and 1.20±0.73 D (P=0.406), respectively. The astigmatism axis tended to approach 90 degrees meridian with a significant difference 1 week postoperatively. Central and minimal corneal thickness remained unchanged, whereas the intraocular pressure and the number of antiglaucoma medications decreased significantly. UCP influenced the corneal topography parameters in the immediate postoperative period; however, with time, all parameters returned to their initial values.

Graft-size selection and anisometropia reduction in penetrating keratoplasty (PKP).

PurposeTo compare the amount of myopia induced by same-size donor-to-host penetrating keratoplasty with that of the amount of myopia induced by over-sized donor-to-host penetrating keratoplasty.SettingTertiary referral academic center.DesignRetrospective cohort study.MethodsCharts from patients who underwent penetrating keratoplasty by the same technique at Bascom Palmer Eye Institute between Nov 1, 2002, and January 1, 2006, were reviewed. The patients underwent optical penetrating keratoplasty using 12 interrupted 10–0 nylon sutures and a 12-bite continuous 10–0 nylon suture by a single surgeon (R.K.F.). The surgical technique used would be considered standard of care at most institutions. The Institutional Review Board, University of Miami Human Subjects Research Office, approved the study protocol. The donor graft was over-sized by 0.25mm in eyes when the intended final refractive target was greater than -1.00 diopters spherical equivalent (SE). The same-size donor graft was used when the intended final refractive target was less than -1.00 diopters SE. The selection of donor graft size was entirely based upon clinical parameters, meaning that the intended final refractive target was determined per each patient’s fellow eye refraction, with the intention of reducing anisometropia. All patients received postoperative refraction and corneal topography. These measurements were performed at 6–8 weeks when the initial removal of sutures commenced, then at 6 months, then after completion of selective suture removal, then again at 12 months.ResultsAt 12 months, the over-sized group resulted in -1.35 diopters (SD = 2.25) SE of refraction, and the same-size group resulted in -0.14 diopters (SD = 2.42) SE. This approached statistical significance (p = 0.052) in comparison to -1.00 diopters spherical equivalent.ConclusionsUsing a donor graft that is over-sized by 0.25mm results in refraction of -1.00 diopters SE or more of myopia. Using a same-size donor-graft results in refraction of less than -1.00 diopters SE. Therefore, careful graft-size selection can result in a more favorable clinical outcome—namely, reduction in anisometropia—in patients undergoing penetrating keratoplasty.

Predictability of the Achieved Lenticule Thickness in Small Incision Lenticule Extraction for Myopia Correction

To investigate the predictability of the achieved lenticule thickness in small incision lenticule extraction (SMILE) for the correction of myopia. In this prospective study, a total of 80 eyes of 45 patients who underwent the SMILE procedure were included. A Scheimpflug camera was used to measure the preoperative and postoperative corneal topography. Achieved lenticule thicknesses at the pupil center and corneal vertex were calculated by subtracting the postoperative corneal thickness at the pupil center and corneal vertex from preoperative corresponding values. Predictability between the achieved and VisuMax readout at different locations (the pupil center and corneal vertex) and postoperative visits (postoperative day 1 and 6 months) were evaluated using a general linear model. Achieved lenticule thickness at the pupil center and corneal vertex showed good correlation at both postoperative day 1 (pupil center: r=0.914, corneal vertex: r=0.903) and 6 months (pupil center: r=0.886, corneal vertex: r=0.866). The achieved lenticule thickness at postoperative day 1 was 8.5-μm thinner at the pupil center and 9.6-μm thinner at the corneal vertex than the VisuMax readout. This study suggests that the predictability between the achieved and VisuMax readout is favorable. The lenticule thickness at the pupil center is closer to the VisuMax readout than corneal vertex.

Assessment of Corneal Higher Order Aberrations Before and After Corneal Collagen Cross-Linking in Patients with Keratoconus

Purpose: This study aimed at assessing the shortterm effect of corneal collagen crosslinking on higher order aberrations of cornea in patients with keratoconus using corneal topography. Patients and Methods: The study was a prospective cohort study that was conducted in a private specialized eye hospital on 40 eyes of 28 keratoconus patients. Each patient was fully assessed preoperatively including doing corneal topography using Pentacam® HR. Transepithelial accelerated CXL was done to all patients. Postoperative corneal topography was done at six months and data was retrieved and analyzed. Results: RMS HOA recorded a higher mean value preoperatively, with a high statistically significant difference (p=0.00). All elements of HOAs showed lower postoperative values except for trefoil 30o. The difference was statistically significant in comma 0o, comma 90o, spherical aberrations and fifth order comma 90° (p=0.026, p= 0.003, p=0.005, and p=0.001 respectively). Conclusion: Transepithelial corneal collagen cross-linking improves corneal higher order aberrations. The maximum effect of the procedure is on comma 0o, comma 90o, spherical aberrations and fifth order comma 90° elements.

Refractive Outcomes After Phototherapeutic Refractive Keratectomy for Granular Corneal Dystrophy.

This retrospective study aimed to evaluate the effectiveness of a novel procedure named phototherapeutic refractive keratectomy (PTRK), which is a sequential procedure composed of phototherapeutic keratectomy ablation for removal of opacities, followed by smoothing ablation for reducing the corneal surface irregularities and photorefractive keratectomy ablation for correcting refractive errors in eyes with primary granular corneal dystrophy. Twenty-three eyes of 17 patients with granular corneal dystrophy were treated with PTRK. Preoperative and postoperative visual acuity, corneal topography, and changes in spherical equivalent and cylindrical refraction were examined and analyzed. The mean spherical equivalent power changed from -0.11 ± 1.36 diopters (D) to 0.19 ± 0.91 D postoperatively (P = 0.121). The change in the mean spherical equivalent was +0.30 ± 0.99 D. The mean preoperative uncorrected distance visual acuity (logMAR) of 0.40 ± 0.26 significantly improved to 0.075 ± 0.145 at 3 months after PTRK (P < 0.001). The mean preoperative corrected distance visual acuity (logMAR) of 0.18 ± 0.17 significantly improved to -0.02 ± 0.11 at 3 months after PTRK (P < 0.01). The surface regularity index was significantly decreased from 0.93 ± 0.46 preoperatively to 0.60 ± 0.30 postoperatively (P < 0.001). Our results showed that PTRK could improve corneal surface irregularities and remove opacities. Furthermore, both corrected visual acuity and uncorrected visual acuity improved by the addition of refractive correction. PTRK is a promising surgical procedure for improving postoperative quality of life with a high degree of patient satisfaction.

Observational study on the impact of corneal power on refractive status of patients after small incision lenticule extraction surgery

Objective: To observe the change of refractive status and possible influencing factors for patients with different corneal power who underwent small incision lenticule extraction (SMILE) surgery. Methods: Prospective cohort study was performed for patients who underwent small incision lenticule extraction (SMILE) surgery at Daping Hospital and Research Institute of Surgery of Third Military Medical University between January and August 2016. The patients were divided into 3 groups according to their corneal power: low curvature group (K(1)≤41.00 D), common curvature group (41.00 D<K(1) and K(2)< 46.00 D), and high curvature group (K(2) ≥ 46.00 D). Preoperative and postoperative (1 day, 1 week, 1, 3 and 6 month) ophthalmic examination results of the patients including uncorrected distance visual acuity (UCDVA), refractive status, intraocular pressure (IOP) and slip lamp microscope examination were recorded. Subjective refraction and Pentacam HR were detected at 6 month after operation so as to monitor the incidence of intraoperative and postoperative complications. The total corneal refractive power (TCRP) based on Ray Tracing technique was applied to evaluate the changes of corneal curvature before and after the surgery. Power vector analysis was applied to evaluate the refraction status based on preoperative and postoperative corneal topography. At 6 months postoperatively, Hotelling t(2) test was applied to compare the refractive status among the groups, and multiple linear regression was applied to analyze the potential influencing factors of under-correction/over-correction. Results: Fifty-four patients (108 eyes) were enrolled, among which 34 were male (68 eyes) and 20 were female (40 eyes). The 3 groups had the same sample size (18 patients and 36 eyes). The low curvature group was featured with youngest average age [(22±4) years, χ(2)=8.94, P<0.05], largest male patients proportion (15/18, χ(2)=11.20, P<0.01) and largest average pupil diameter [(3.26±0.36) mm, F=4.83, P<0.05], as compared to the other 2 groups. The incidence of severe OBL (25/36) was significantly higher in the high curvature group (χ(2)=65.06, P<0.01). All patients showed no diminution of vision and their UCDVA averaged 5.1 at 6 months postoperatively, however patients with low curvature were slightly "under-corrected" in 1-mm and 2-mm zones (Error values<0). The preoperative spherical equivalent (SE) and postoperative spherical aberration in 6-mm zone were the significant factors affecting the relationship between preoperative corneal curvature and postoperative refractive status (r=0.392, 2.745, P<0.05). Conclusions: SMILE is safe and effective for patients with both low and high curvature, but the incidence of intraoperative OBL is significantly higher in high curvature group. Patients with low curvature were slightly "under-corrected" in 1-mm and 2-mm zones, which may imply that the design of the lenticule may be aspheric and that the cornea reshaping process of younger patients may be of particular characteristics. (Chin J Ophthalmol, 2018, 54: 48-54).

Postoperative Corneal Asphericity in Low, Moderate, and High Myopic Eyes After Transepithelial PRK Using a New Pulse Allocation.

To evaluate the postoperative asphericity in low, moderate, and high myopic eyes after combined transepithelial photorefractive keratectomy and SmartSurfACE treatment (SCHWIND eye-tech-solutions GmbH, Kleinostheim, Germany). In this retrospective case series, the outcomes of myopic SmartSurfACE were evaluated at 3 months postoperatively in 106 eyes and divided into low (less than -4.125 diopters [D]), moderate (-4.125 to -6.25 D), and high (more than -6.25 D) myopia groups. In all cases, standard examinations and preoperative and postoperative corneal topography (SCHWIND Sirius) were performed. The analysis comprised evaluating the change in asphericity versus planned correction, comparing expected and achieved postoperative asphericity for all eyes, and comparison of the three groups in terms of the preoperative and postoperatively expected and achieved asphericity. RESULTS At 3 months postoperatively, the low myopia group (n = 33) improved average negative asphericity (Q = -0.04 ± 0.17 preoperative vs -0.19 ± 0.20 postoperative, P < .05). The moderate myopia group (n = 35) maintained or slightly improved average negative asphericity (Q = -0.07 ± 0.14 preoperative vs -0.05 ± 0.24 postoperative, P = .35). For the high myopia group (n = 38), the eyes became more oblate compared to the preoperative status (Q = -0.09 ± 0.15 preoperative vs 0.62 ± 0.70 postoperative, P < .05). In terms of asphericity, the difference between the three groups was not statistically significant preoperatively (P > .10), but showed significant differences postoperatively (P < .007). The cohort's average preoperative corrected distance visual acuity was 0.01 ± 0.04 logMAR (range: 0.0 to 0.18 logMAR) and uncorrected distance visual acuity was 0.03 ± 0.08 logMAR (range: -0.12 to 0.40 logMAR) 3 months postoperatively. SmartSurfACE maintained or slightly improved preoperative corneal asphericity for low to moderate myopic corrections (up to -6.00 D). This may provide advantages in the quality of vision and the onset of presbyopic symptoms after laser refractive surgery in myopic patients. [J Refract Surg. 2017;33(12):820-826.].

Conventional Versus Accelerated Collagen Cross-Linking for Keratoconus: A Comparison of Visual, Refractive, Topographic and Biomechanical Outcomes.

Objective:The aim was to compare the visual, refractive, topographic and biomechanical outcomes in patients with progressive keratoconus treated with either conventional or accelerated crosslinking at one year follow up.Methods:It is a prospective, non-randomised interventional study of 76 patients who underwent conventional (CXL; 3mW/cm2 for 30 minutes) or accelerated cross linking (KXL; 30mW/cm2 for 4 minutes) for progressive keratoconus. Baseline and postoperative visual acuity, manifest refraction, corneal topography, pachymetry, endothelial cell density and biomechanical parameters of corneal hysteresis and corneal resistance factor were evaluated and compared.Results:The 2 groups were comparable in terms of uncorrected and best corrected visual acuity and spherical equivalent. Both groups showed no significant increase in K1, K2 and Kmean from baseline at 12 months. There was also no difference between the CXL and KXL group for postoperative corneal topography as well as central and minimal pachymetry up to 12 months. There was a significant increase in both corneal hysteresis (0.62mm Hg, P=0.04) and corneal resistance factor (0.91mm Hg, P=0.003) in the KXL group at 12 months but not in the CXL group. There was no significant endothelial cell loss throughout follow up in both the groups.Conclusion:We have established comparability of the 2 protocols in stabilizing the progression of keratoconus. Our findings also suggested an added biomechanical advantage of accelerated crosslinking at 1 year follow up.

A study on efficacy of limbal relaxing incisions in correcting corneal astigmatism along with clear corneal phacoemulsification in a tertiary eye care centre in South India

Aim: The main aim of this study was to study the effectiveness of limbal relaxing incisions in correcting corneal astigmatism when combined with clear corneal phacoemulsification. Materials and Methods: 50 eyes of 37 patients satisfying the inclusion and exclusion criteria were included in the study. After adequate pre operative workup, all patients underwent limbal relaxing incisions coupled with clear corneal phacoemulsification. The incisions were calculated based on Gills nomogram. Postoperative visual acuity and corneal topography were performed to assess the correction of corneal astigmatism. Results: The mean age of our study population was 57.08± 10.07 years. 50 eyes of 21 males and 16 females were included in our study. The mean preoperative Uncorrected Visual Acuity was 1.0 with a standard deviation of 0.5 (in logMAR) and the best spectacle corrected visual acuity was 0.8 with a standard deviation of 0.4. The postoperative uncorrected visual acuity at 4 weeks 0.0±0.15 with a best corrected visual acuity was 0.09±0.1. At 12 weeks, uncorrected visual acuity was 0.0 with a standard deviation 0.07. There was 71.8% decrease in central corneal astigmatism after limbal relaxing incisions. Conclusion: Therefore we conclude that limbal relaxing incisions can be used effectively in conjunction with cataract surgery to reduce the astigmatism <3 D at the corneal level and aids us in providing spectacle free optimal distance vision in patients.

Corneal Topographic Changes After Eyelid Ptosis Surgery.

To evaluate the corneal topography and the topographic changes after ptosis surgery on patients affected by congenital and acquired blepharoptosis. Twenty eyes of 17 patients affected by acquired and congenital ptosis underwent surgical correction through anterior levator complex tightening. Computerized tomography (Syrius Sistem; CSO) was used to analyze any change in corneal astigmatism (CYL), simulated keratometry, anterior corneal symmetry index front, apical keratometry front, and central corneal thickness. Visual acuity, margin reflex distance, and levator function were also measured. After surgical ptosis repair, corneal topography demonstrated a reduction in average keratometry of 0.15 ± 0.47 diopters (D) and in corneal astigmatism of 0.26 ± 1.12 D. Significant differences were found in apical keratometry front (-1.84 ± 1.76 D) and in best-corrected visual acuity (-0.18 ± 0.06 logMAR) in the postoperative examinations. Central corneal thickness did not show significant differences between preoperative and postoperative examinations. Postoperative topographic maps showed a reduction of symmetry index front (0.10 ± 0.64 D). Eyelid ptosis modifies anterior corneal surface inducing refractive errors and modifying corneal astigmatism in patients, thus affecting the quality of vision. The surgical correction of blepharoptosis induces anterior corneal surface modification, restoring corneal symmetry and regular corneal astigmatism. Postoperative corneal topography showed normal corneal contours.

Small optical zones with aspheric profiles in laser refractive surgery for myopia: A surgical outcome and patient satisfaction study

To assess the outcomes of small optical zone (OZ) ablations used in conjunction with large transition zones (TZ) and a highly aspheric treatment profile. Interventional case series of 39 consecutive patients with myopia or myopic astigmatism. Patient data included pre and postoperative refraction and visual acuities, laser treatment settings and pre and postoperative corneal topography as well as questionnaire responses about the use of glasses and the quality of vision postoperatively. The mean preoperative spherical equivalent was -4.50±2.11 dioptres (D) and the mean OZ and TZ diameters were 4.5±0.5mm and 8.1±0.4mm, respectively. The mean patient age was 40.7±10.4 years. Manifest spherical refraction was within ±0.5D in 87% of patients (±1.0D in 99%) and cylindrical refraction within 0.5D in 79% (≤1.0D in 95%). The need to wear distance glasses postoperatively was associated with dissatisfaction with the quality of daytime vision (p=0.05) and unhappiness with night vision was associated with symptoms of halos (p=0.03) and starbursts (p=0.02). The proportion of patients reporting symptoms of dysphotopsias included: ghosting 0%; glare 2%; halos 10%; and starbursts 15%. There was a significant difference in the measured mean effective OZ diameter (4.8±0.3mm) compared to the mean programmed OZ (4.5±0.5mm, p=0.00). Small ablation zones, when used in conjunction with a large diameter TZ, do not lead to a greater incidence of unwanted visual phenomena over that reported by many studies with larger OZs.