Safety and Effectiveness of Smooth Incision Lenticular Keratomileusis (SILKTM) Using the ELITA(TM) Femtosecond Laser System for Correction of Myopic and Astigmatic Refractive Errors.

Purpose: To evaluate visual outcomes following the Smooth Incision Lenticular Keratomileusis (SILKTM) procedure for correction of myopic refractive errors with and without astigmatism, using the ELITATM Femtosecond Laser System. Patients and Methods: A prospective, multicenter, single-arm, open-label clinical study was conducted. Eighty-five myopic subjects (n = 170 eyes), aged 18 years or older, with manifest refractive spherical equivalent (MRSE) up to -12.00 D and astigmatism up to -6.00 D, were treated binocularly using the ELITA femtosecond laser and followed up for 6 months. Intended correction was emmetropia for all eyes. The primary outcome measures included post-operative uncorrected and corrected distance visual acuity (UDVA and CDVA). Secondary outcome measures included surgeon's rating for ease of lenticule extraction, predictability, safety, and stability. Results: A total of 170 eyes of 85 patients underwent SILK. Preoperative mean MRSE was -4.14 D ± 1.32 D (range -1.38 D to -8.88 D) and the mean cylinder was -0.77 D ± 0.62 D. Intraoperative surgeon ease of lenticule dissection was rated as grade 0 or 1 in 85.3% of eyes (no/only mild dissection needed). UDVA at 1 day, 1 week, 1 month, and 6 months was 20/20 or better in 65.9%, 85.4%, 91.5%, and 96% of eyes, respectively. No eyes lost any lines of CDVA at 6 months compared to the preoperative. The postoperative MRSE was stable over time, ranging from -0.34 D ± 0.24 D at 1 month to -0.33 D ± 0.23 D at 6 months. MRSE predictability (± 0.50 D) was 93.5% (129/138) at 3 months and 91.1% (113/124) at 6 months. No serious adverse events were noted. Conclusion: The SILK procedure with the ELITA Femtosecond Laser System is safe and effective for the treatment of myopic refractive errors with and without astigmatism. Fast visual recovery was demonstrated, with stability achieved by 3 months.

Simultaneous Topography-guided Custom Ablation With Corneal Cross-linking for Keratoconus: 10-Year Prospective Outcomes.

PURPOSE: To assess 10-year visual and tomographic outcomes of topography-guided custom ablation (T-CAT) with corneal cross-linking (CXL) in eyes with keratoconus. METHODS: T-CAT with CXL was performed in 600 eyes (522 patients). Based on the T-CAT ablation plan, the theoretical maximum ablation depth was 50 µm after epithelium removal. After ablation, accelerated corneal cross-linking (CXL) was performed in the central 8-mm zone (9 mW/cm2 for 10 minutes in "epi-off" mode). The visual acuity and tomography were assessed. RESULTS: There was significant improvement in uncorrected (P = .001) and corrected (P = .001) distance visual acuity after the procedure. Keratometry, root mean square lower order aberrations and higher order aberrations, defocus, coma 90°, and spherical aberration reduced significantly after surgery at 10 years of follow-up (P < .005). All Pentacam (Oculus Optikgerate GmbH) tomographic variables showed significant changes indicating regularization after T-CAT (P < .005). Flattening of greater than 5.00 diopters in maximum keratometry was noted in 6 eyes (1%). Two of 600 eyes progressed postoperatively and required repeat CXL. CONCLUSIONS: T-CAT plus CXL is a safe and effective technique even in the long term for regularizing the anterior corneal surface with significant visual improvement and reduction in higher order corneal aberrations. [J Refract Surg. 2023;39(11):759-766.].

Cold bandage contact lens use reduces post-photorefractive keratectomy or corneal collagen-crosslinking pain perception in patients.

Purpose: To compare post-operative pain perception using bandage contact lens (BCL) stored at 2-8°C (Cold BCL, CL-BCL) or room temperature (23 - 25°C, RT-BCL) after photorefractive keratectomy (PRK) or corneal collagen-crosslinking (CXL) and determine status of nociception associated factors. Methods: In this prospective interventional study, 56 patients undergoing PRK for refractive correction and 100 keratoconus (KC) undergoing CXL were recruited following approval from the institutional ethics committee with informed consent. Patients undergoing bilateral PRK received RT-BCL on one eye and CL-BCL on the other. Pain was graded by Wong-Baker scoring on the first post-operative day (PoD1). Expression of transient receptor potential channels (TRPV1, TRPA1, TRPM8), calcitonin gene-related peptide (CGRP) and IL-6 was measured in cellular content from used BCLs collected on PoD1. Equal number of KC patients received RT-BCL or CL-BCL post-CXL. Pain was graded by Wong-Baker scoring on PoD1. Results: Pain scores on PoD1 were significantly (P < 0.0001) reduced in subjects receiving CL-BCL (Mean ± SD: 2.6 ± 2.1) compared to RT-BCL (6.0 ± 2.4) post-PRK. 80.4% of subjects reported reduced pain scores with CL-BCL. 19.6% reported no change or increased pain scores with CL-BCL. TRPM8 expression was significantly (P < 0.05) increased in BCL of subjects reporting reduced pain with CL-BCL compared to those who did not. Pain scores on PoD1 were significantly (P < 0.0001) reduced in subjects receiving CL-BCL (3.2 ± 2.1) compared to RT-BCL (7.2 ± 1.8) post-CXL. Conclusion: The simple approach of using a cold BCL post-operatively substantially reduced pain perception and could overcome post-operative pain-related limited acceptance of PRK/CXL.

Artificial intelligence-based stratification of demographic, ocular surface high-risk factors in progression of keratoconus.

Purpose: The purpose of this study was to identify and analyze the clinical and ocular surface risk factors influencing the progression of keratoconus (KC) using an artificial intelligence (AI) model. Methods: This was a prospective analysis in which 450 KC patients were included. We used the random forest (RF) classifier model from our previous study (which evaluated longitudinal changes in tomographic parameters to predict "progression" and "no progression") to classify these patients. Clinical and ocular surface risk factors were determined through a questionnaire, which included presence of eye rubbing, duration of indoor activity, usage of lubricants and immunomodulator topical medications, duration of computer use, hormonal disturbances, use of hand sanitizers, immunoglobulin E (IgE), and vitamins D and B12 from blood investigations. An AI model was then built to assess whether these risk factors were linked to the future progression versus no progression of KC. The area under the curve (AUC) and other metrics were evaluated. Results: The tomographic AI model classified 322 eyes as progression and 128 eyes as no progression. Also, 76% of the cases that were classified as progression (from tomographic changes) were correctly predicted as progression and 67% of cases that were classified as no progression were predicted as no progression based on clinical risk factors at the first visit. IgE had the highest information gain, followed by presence of systemic allergies, vitamin D, and eye rubbing. The clinical risk factors AI model achieved an AUC of 0.812. Conclusion: This study demonstrated the importance of using AI for risk stratification and profiling of patients based on clinical risk factors, which could impact the progression in KC eyes and help manage them better.

Role of in vivo confocal microscopy in dry eye disease and eye pain.

Dry eye disease is known to have a lot of variability in presentation with overlapping subtypes. Understanding the pathology of this condition will guide therapeutic options. In vivo confocal microscopy is a diagnostic and imaging modality that provides high magnification and high-resolution images of all layers of the cornea and ocular surface. Various structures in the cornea and their alterations due to dry eye have been imaged. The impact of the tear film instability, inflammation, and altered homeostasis on the corneal epithelium, nerves, keratocytes, and dendritic cells have been evaluated across different studies. In addition, key features of IVCM in patients with neuropathic pain have been highlighted in this paper.

Vitamin D and eye: Current evidence and practice guidelines.

Vitamin D is a steroid hormone that has widespread role in human physiology, not only in the maintenance of calcium homeostasis but also in immunomodulation, cellular differentiation, and proliferation. The immunomodulatory effects of vitamin D are well known and are applicable to the ocular surface immune cells and structural cells. The role of vitamin D in ocular surface conditions such as dry eye disease (DED), keratoconus (KC), and post-surgical outcomes has received widespread and well-deserved attention. Vitamin D supplementation is shown to improve DED clinically as well as in experimental models. The anti-inflammatory properties may be crucial in the treatment of ocular surface conditions such as DED and KC. Vitamin D plays a multifaceted role in corneal wound healing with its anti-inflammatory and extracellular matrix remodeling properties. In this review, we discuss how to approach patients with DED and those undergoing refractive surgery with the available basic and clinical knowledge on the role of vitamin D in these conditions. We aim to highlight the importance of clinically harnessing vitamin D-mediated natural immuno-inflammatory modulation in combination with currently available standard of care strategies to reduce the morbidity and disease duration associated with ocular surface diseases.

Tear biomarkers in dry eye disease: Progress in the last decade.

Dry eye disease (DED) is a commonly occurring, multifactorial disease characterized by reduced tear film stability and hyperosmolarity at the ocular surface, leading to discomfort and visual compromise. DED is driven by chronic inflammation and its pathogenesis involves multiple ocular surface structures such as the cornea, conjunctiva, lacrimal glands, and meibomian glands. The tear film secretion and its composition are regulated by the ocular surface in orchestration with the environment and bodily cues. Thus, any dysregulation in ocular surface homeostasis causes an increase in tear break-up time (TBUT), osmolarity changes, and reduction in tear film volume, all of which are indicators of DED. Tear film abnormalities are perpetuated by underlying inflammatory signaling and secretion of inflammatory factors, leading to the recruitment of immune cells and clinical pathology. Tear-soluble factors such as cytokines and chemokines are the best surrogate markers of disease severity and can also drive the altered profile of ocular surface cells contributing to the disease. Soluble factors can thus help in disease classification and planning treatment strategies. Our analysis suggests increased levels of cytokines namely interleukin-1ß (IL-1ß), IL-2, IL-4, IL-6, IL-9, IL-12, IL-17A, interferon-gamma (IFN-γ), tumor necrosis factor-alpha (TNF-α); chemokines (CCL2, CCL3, CCL4, CXCL8); MMP-9, FGF, VEGF-A; soluble receptors (sICAM-1, sTNFR1), neurotrophic factors (NGF, substance P, serotonin) and IL1RA and reduced levels of IL-7, IL-17F, CXCL1, CXCL10, EGF and lactoferrin in DED. Due to the non-invasive sample collection and ease of quantitively measuring soluble factors, tears are one of the best-studied biological samples to molecularly stratify DED patients and monitor their response to therapy. In this review, we evaluate and summarize the soluble factors profiles in DED patients from the studies conducted over the past decade and across various patient groups and etiologies. The use of biomarker testing in clinical settings will aid in the advancement of personalized medicine and represents the next step in managing DED.

Ion channels in dry eye disease.

Dry eye disease (DED) which affects millions of people worldwide is an ocular surface disease that is strongly associated with pain, discomfort, and visual disturbances. Altered tear film dynamics, hyperosmolarity, ocular surface inflammation, and neurosensory abnormalities are the key contributors to DED pathogenesis. The presence of discordance between signs and symptoms of DED in patients and refractoriness to current therapies in some patients underpin the need for studying additional contributors that can be modulated. The presence of electrolytes or ions including sodium, potassium, chloride, bicarbonate, calcium, and magnesium in the tear fluid and ocular surface cells contribute to ocular surface homeostasis. Ionic or electrolyte imbalance and osmotic imbalance have been observed in DED and feed-forward interaction between ionic imbalances and inflammation alter cellular processes in the ocular surface resulting in DED. Ionic balances in various cellular and intercellular compartments are maintained by dynamic transport via ion channel proteins present in cell membranes. Hence, alterations in the expression and/or activity of about 33 types of ion channels that belong to voltage-gated channels, ligand-gated channels, mechanosensitive ion channel, aquaporins, chloride ion channel, sodium-potassium-chloride pumps or cotransporters have been investigated in the context of ocular surface health and DED in animal and/or human subjects. An increase in the expression or activity of TRPA1, TRPV1, Nav1.8, KCNJ6, ASIC1, ASIC3, P2X, P2Y, and NMDA receptor have been implicated in DED pathogenesis, whereas an increase in the expression or activity of TRPM8, GABAA receptor, CFTR, and NKA have been associated with resolution of DED.

Ocular surface immune cell diversity in dry eye disease.

Dry eye disease (DED) is a multifactorial chronic ocular surface inflammatory condition. Disease severity has been directly related to the immuno-inflammatory status of the ocular surface. Any perturbation in the orchestrated functional harmony between the ocular surface structural cells and immune cells, both resident and trafficking ones, can adversely affect ocular surface health. The diversity and contribution of ocular surface immune cells in DED have been of interest for over a couple of decades. As is true with any mucosal tissue, the ocular surface harbors a variety of immune cells of the innate-adaptive continuum and some of which are altered in DED. The current review curates and organizes the knowledge related to the ocular surface immune cell diversity in DED. Ten different major immune cell types and 21 immune cell subsets have been studied in the context of DED in human subjects and in animal models. The most pertinent observations are increased ocular surface proportions of neutrophils, dendritic cells, macrophages, and T cell subsets (CD4+; CD8+; Th17) along with a decrease in T regulatory cells. Some of these cells have demonstrated disease-causal association with ocular surface health parameters such as OSDI score, Schirmer's test-1, tear break-up time, and corneal staining. The review also summarizes various interventional strategies studied to modulate specific immune cell subsets and reduce DED severity. Further advancements would enable the use of ocular surface immune cell diversity, in patient stratification, i.e. DED-immunotypes, disease monitoring, and selective targeting to resolve the morbidity related to DED.

Autophagy in dry eye disease: Therapeutic implications of autophagy modulators on the ocular surface.

Dry eye disease (DED) is a chronic ocular surface disorder, associated with inflammation, which can cause severe morbidity, visual compromise, and loss of quality of life, affecting up to 5-50% of the world population. In DED, ocular surface damage and tear film instability due to abnormal tear secretion lead to ocular surface pain, discomfort, and epithelial barrier disruption. Studies have shown the involvement of autophagy regulation in dry eye disease as a pathogenic mechanism along with the inflammatory response. Autophagy is a self-degradation pathway in mammalian cells that reduces the excessive inflammation driven by the secretion of inflammatory factors in tears. Specific autophagy modulators are already available for the management of DED currently. However, growing studies on autophagy regulation in DED might further encourage the development of autophagy modulating drugs that reduce the pathological response at the ocular surface. In this review, we summarize the role of autophagy in the pathogenesis of dry eye disease and explore its therapeutic application.

Hormones and dry eye disease.

The endocrine system influences all tissues and cells in the human body. The ocular surface is constantly exposed to circulating hormones and expresses their specific receptors. Dry eye disease (DED) is a disorder with multifactorial etiology, and endocrine anomalies are one of the inciting factors. The endocrine anomalies that cause DED include physiological conditions such as menopause, menstrual cycle variations, pathologies such as polycystic ovarian syndrome, androgen resistance, iatrogenic conditions such as contraceptive use, and antiandrogen treatment. This review highlights the status of these hormones in DED along with the mechanism of action of different hormones on the ocular surface structures and the clinical implications of these effects. The influence of androgens, estrogens, and progesterone on the ocular surface tissues, and the implications of androgen-deficient states in DED are also discussed. The physiological and pathological effects of menopause and sex hormone replacement therapy are discussed. The effects of insulin and insulin resistance on the ocular surface and DED, and the growing potential of topical insulin therapeutics for DED are mentioned. Thyroid-associated ophthalmopathy, its impact on the ocular surface, and the tissue effects of thyroid hormone in the context of DED are reviewed. Finally, the potential role of hormonal therapeutics in the management of DED has also been discussed. The compelling evidence suggests that it would be clinically beneficial to consider the possibility of hormonal imbalances and their impact while treating patients with DED.

Patient stratification using point of care biomarkers in dry eye disease.

With changes in lifestyle, such as the increasing use of digital screens and rising demand for refractive surgery, dry eye disease has become increasingly prevalent in recent times. While we are equipped with a number of diagnostic modalities and a myriad of treatment forms, ranging from topical medication to procedural therapies, the condition remains an enigma in terms of varied patient satisfaction. An understanding of the molecular basis of a disease may open up new avenues in the customization of its treatment. We attempt to simplify this in the form of a stepwise protocol to incorporate biomarker assays in dry eye management.

Assessing clinical and molecular outcomes of prophylactic thermal pulsation therapy on ocular surface health following refractive surgery.

Purpose: To study ocular surface signs, symptoms, and tear film composition following prophylactic thermal pulsation therapy (TPT) prior to refractive surgery, and to compare these outcomes with those who underwent TPT after refractive surgery. Methods: Patients with mild-to-moderate evaporative dry eye disease (DED) and/or meibomian gland dysfunction (MGD) undergoing refractive surgery were included. Group 1 patients received TPT (LipiFlow) prior to laser-assisted in situ keratomileusis (LASIK; n = 32, 64 eyes), and Group 2 patients received TPT three months after LASIK (n = 27, 52 eyes). Ocular Surface Disease Index (OSDI) score, Schirmer's test (ST1, ST2), Tear Breakup Time (TBUT), meibography, and tear fluid were obtained preoperatively and at three months postoperatively in Groups 1 and 2. Additional postoperative evaluation was performed three months after TPT in Group 2. Tear soluble factor profile was measured by multiplex enzyme-linked immunosorbent assay (ELISA) using flow cytometry. Results: Postoperative OSDI score was significantly lower and TBUT was significantly higher when compared with matched preoperative values of Group 1 participants. On the other hand, the postoperative OSDI score was significantly higher and TBUT significantly lower when compared with matched preoperative values of Group 2 participants. TPT significantly reduced the postoperative elevation in OSDI and significantly reduced the postoperative reduction in TBUT in Group 2 participants. Tear Matrix metalloproteinase-9/ Tissue inhibitor matrix metalloproteinase 1 (MMP-9/TIMP1) ratio was significantly higher, postoperatively, when compared with matched preoperative levels in Group 2. However, MMP9/TIMP1 ratio remained unaltered in Group 1 participants. Conclusion: TPT prior to refractive surgery improved postsurgical ocular surface signs and symptoms and reduced tear inflammatory factors, thereby suggesting the plausibility of reduced post-refractive surgery DED in patients.

Nexus of ocular motility and dry eye.

Purpose: To evaluate the effectiveness of vision therapy (VT) in patients with chronic presumed refractory dry eye disease (DED) and concurrent nonstrabismic binocular vision anomalies (NSBVAs). To propose an algorithmic approach to manage patients with refractory DED. Methods: Thirty-two patients with chronic (>1 year) presumed refractory DED and NSBVA were prospectively evaluated. The baseline dry eye evaluation and comprehensive orthoptic evaluation were done. VT was administered by a trained orthoptist for 2 weeks. The binocular vision (BV) parameters and percentage subjective improvement were assessed after the VT. Results: On evaluation, 12 patients (37.5%) had both DED and NSBVA, and 20 patients (62.5%) had only NSBVA. Twenty-nine patients (90.62%) showed significant improvement in BV parameters following VT. Binocular near point of accommodation (median, range) improved from 17 (8-40) to 12 (5-26) mm (P value < 0.0001), and near point of convergence (median, range) improved from 6 (3-33) to 6 (5-14) (P value 0.004) with VT. Thirty-one patients (96.87%) reported symptomatic improvement after VT, and 62.5% of these showed more than 50% improvement in symptoms. Conclusion: The present study confirms the beneficial role of VT in the treatment of patients with DED with concurrent NSBVA. It is essential to diagnose and treat NSBVA in patients with DED to ensure complete relief of symptoms and patient satisfaction. As there is a significant overlap between symptoms of dry eye disease and that of NSBVA, a complete orthoptic evaluation is recommended in all patients presenting with refractory dry eye disease related symptoms.

Modulation of mucin secretion using combined polyethylene glycol-propylene glycol topical formulation in a hyperosmotic stress-based explant model.

Purpose: Ocular surface discomfort and dry eye disease are caused by a dysfunctional tear film. The efficacy of lubricating eye drops on the human eye is known, but the compositions may show differential effects on rescuing the tear film. Mucins form a critical layer of the tear film, a reduction of which may be causative for ocular surface conditions. Therefore, it is essential to develop relevant human-derived models to test mucin production. Methods: Human corneoscleral rims were obtained from a healthy donor (n = 8) post-corneal keratoplasty and cultured in DMEM/F12 media. Hyperosmolar stress mimicking dry eye disease was induced by exposing the corneoscleral rim tissues to +200 mOsml NaCl-containing media. The corneoscleral rims were treated with polyethylene glycol-propylene glycol (PEG-PG)-based topical formulation. Gene expression analysis was performed for NFAT5, MUC5AC, and MUC16. Secreted mucins were measured by enzyme-linked immunosorbent assay (ELISA) (Elabscience, Houston, TX, USA) for MUC5AC and MUC16. Results: The corneoscleral rims responded to hyperosmolar stress by upregulating NFAT5, a marker for increased osmolarity, as observed in the case of dry eye disease. The expression of MUC5AC and MUC16 was reduced upon an increase in hyperosmotic stress. The corneoscleral rim tissues showed induction of MUC5AC and MUC16 expression upon treatment with PEG-PG topical formulation but did not show significant changes in the presence of hyperosmolar treatments. Conclusion: Our findings showed that PEG-PG-based topical formulation slightly alleviated hyperosmolar stress-induced decrease in MUC5AC and MUC16 gene expression that is encountered in DED.

Role of artificial intelligence in determining factors impacting patients' refractive surgery decisions.

Purpose: To create a predictive model using artificial intelligence (AI) and assess if available data from patients' registration records can help in predicting definitive endpoints such as the probability of patients signing up for refractive surgery. Methods: This was a retrospective analysis. Electronic health records data of 423 patients presenting to the refractive surgery department were incorporated into models using multivariable logistic regression, decision trees classifier, and random forest (RF). Mean area under the receiver operating characteristic curve (ROC-AUC), sensitivity (Se), specificity (Sp), classification accuracy, precision, recall, and F1-score were calculated for each model to evaluate performance. Results: The RF classifier provided the best output among the various models, and the top variables identified in this study by the RF classifier excluding income were insurance, time spent in the clinic, age, occupation, residence, source of referral, and so on. About 93% of the cases that did undergo refractive surgery were correctly predicted as having undergone refractive surgery. The AI model achieved an ROC-AUC of 0.945 with an Se of 88% and Sp of 92.5%. Conclusion: This study demonstrated the importance of stratification and identifying various factors using an AI model which could impact patients' decisions while selecting a refractive surgery. Eye centers can build specialized prediction profiles across disease categories and may allow for the identification of prospective obstacles in the patient's decision-making process, as well as strategies for dealing with them.

Decision taking in corneal refractive surgery.

A 27-year-old woman who wants to get rid of contact lenses and spectacles was seen at our clinic. She had strabismus surgery as a child and was patched for the right eye but now shows mild nondisturbing exophoria. Infrequently, she likes to box in the sports school. Her corrected distance visual acuity at presentation in the right eye was 20/16 with -3.75 -0.75 × 50 and in the left eye 20/16 with -3.75 -1.25 × 142. Her cycloplegic refraction in the right eye was -3.75 -0.75 × 44 and in the left eye was -3.25 -1.25 × 147. The left eye is the dominant eye. The tear break-up time was 8 seconds in both eyes, and the Schirmer tear test was 7 to 10 mm in right and left eyes, respectively. Pupil sizes under mesopic conditions were 6.62 mm and 6.68 mm. The anterior chamber depth (ACD) (measured from the epithelium) in the right eye was 3.89 mm and in the left eye was 3.87 mm. The corneal thickness was 503 µm and 493 µm of the right and left eye, respectively. Corneal endothelial cell density was on average 2700 cells/mm2 for both eyes. Slitlamp biomicroscopy showed clear corneas and a normal flat iris configuration. Supplemental Figures 1 to 4 (available at http://links.lww.com/JRS/A818, http://links.lww.com/JRS/A819, http://links.lww.com/JRS/A820, and http://links.lww.com/JRS/A821) show the corneal topography and Belin-Ambrósio deviation (BAD) maps at presentation of the right eye and left eye, respectively. Would you consider this patient a candidate for corneal refractive surgery (eg, laser-assisted subepithelial keratectomy, laser in situ keratomileusis [LASIK], or small-incision lenticule extraction [SMILE] procedure)? Has your opinion changed given the recent opinion of the U.S. Food and Drug Administration (FDA) regarding LASIK?1 The patient herself is slightly favoring an implantation of a phakic intraocular lens (pIOL), as she prefers something reversible. Would you implant a pIOL, and which type of IOL, for this level of myopia? What is your diagnosis or are additional diagnostic methodologies needed to establish a diagnosis? What is your treatment advice for this patient? REFERENCES 1. U.S. Food and Drug Administration, HHS. Laser-assisted in situ keratomileusis (LASIK) lasers-patient labeling recommendations; draft guidance for industry and food and drug administration staff; availability. July 28, 2022, Federal Register; 87 FR 45334. Available at: https://www.fda.gov/regulatory-information/search-fda-guidance-documents/laser-assisted-situ-keratomileusis-lasik-lasers-patient-labeling-recommendations Accessed January 25, 2023.

New simulation software to predict postoperative corneal stiffness before laser vision correction.

PURPOSE: To develop a new virtual surgery simulation platform to predict postoperative corneal stiffness (Kc mean ) after laser vision correction (LVC) surgery. SETTING: Narayana Nethralaya Eye Hospital and Sankara Nethralaya, India; Humanitas Clinical and Research Center, Italy. DESIGN: Retrospective observational case series. METHODS: 529 eyes from 529 patients from 3 eye centers and 10 post-small-incision lenticule extraction (SMILE) ectasia eyes were included. The software (called AcuSimX) derived the anisotropic, fibril, and extracellular matrix biomechanical properties (using finite element calculation) of the cornea using the preoperative Corvis-ST, Pentacam measurement, and inverse finite element method assuming published healthy collagen fibril orientations. Then, the software-computed postoperative Kc mean was adjusted with an artificial intelligence (AI) model (Orange AI) for measurement uncertainties. A decision tree was developed to classify ectasia from normal eyes using the software-computed and preoperative parameters. RESULTS: In the training cohort (n = 371 eyes from 371 patients), the mean absolute error and intraclass correlation coefficient were 6.24 N/m and 0.84 (95% CI, 0.80-0.87), respectively. Similarly, in the test cohort (n = 158 eyes from 158 patients), these were 6.47 N/m and 0.84 (0.78-0.89), respectively. In the 10 ectasia eyes, the measured in vivo (74.01 [70.01-78.01]) and software-computed (74.1 [69.03-79.17]) Kc mean were not statistically different ( P = .96). Although no statistically significant differences in these values were observed between the stable and ectasia groups ( P ≥ .14), the decision tree classification had an area under the receiver operating characteristic curve of 1.0. CONCLUSIONS: The new software provided an easy-to-use virtual surgery simulation platform for post-LVC corneal stiffness prediction by clinicians and was assessed in post-SMILE ectasia eyes. Further assessments with ectasia after surgeries are required.

Impact of crossplay between ocular aberrations and depth of focus in topo-guided laser-assisted in situ keratomileusis outcomes.

Purpose: To develop a nomogram in cases with mismatch between subjective and Topolyzer cylinder, and based on the magnitude of the mismatch, customize a treatment plan to attain good visual outcomes post-laser-assisted in situ keratomileusis (LASIK) surgery. Methods: The patients were evaluated preoperatively using corneal tomography with Pentacam. Five optimal corneal topography scans were obtained from the Topolyzer Vario were used for planning the LASIK treatment. For the nomogram purpose, the patients were divided into three categories based on the difference between the subjective cylinder and Topolyzer (corneal) cylinder. The first group (group 1) consisted of eyes of patients, where the difference was less than or equal to 0.4 D. The second group (group 2) consisted of eyes, where the difference was more than 0.4 D and the subjective cylinder was lesser than the Topolyzer cylinder. The third group (group 3) included eyes where the difference was more than 0.4 D but the subjective cylinder was greater than the Topolyzer cylinder. LASIK was performed with the WaveLight FS 200 femtosecond laser and WaveLight EX500 excimer laser. Assessment of astigmatism correction for the three groups was done using Aplins vector analysis. For comparison of proportions, Chi-square test was used. A P value less than 0.05 was considered statistically significant. Results: The UDVA was statistically significantly different when compared between groups 1 and 2 (P = 0.02). However, the corrected distance visual acuity (CDVA) was similar among all the three groups (P = 0.1). Group 3 showed an increase of residual cylinder by -0.25 D, which was significant at intermediate and near reading distances (P < 0.05). Group 3 showed significantly higher target-induced astigmatism (TIA) compared to groups 1 and 2 (P = 0.01). The mean surgically induced astigmatism (SIA) was the least in group 2, which was statistically significant (P < 0.01). Conclusion: The outcomes for distance vision using our nomogram postoperatively were excellent, but further refinement for improving the near vision outcomes is required.