Lower dose of metformin combined with artesunate induced autophagy-dependent apoptosis of glioblastoma by activating ROS-AMPK-mTOR axis.

Glioblastoma multiform (GBM), one of the most common, aggressive primary brain tumours, demonstrates resistance to radiotherapy and chemotherapy after surgical resection and treatment failure. Metformin (MET) has been shown to suppress the proliferative capacity and invasion ability of GBM cells by activating AMPK and inhibiting mTOR, but the effective dose exceeded the maximum tolerated dose. Artesunate (ART) can exert certain anti-tumour effects by activating the AMPK-mTOR axis and inducing autophagy in tumour cells. Therefore, this study investigated the effects of MET combined with ART combination therapy on autophagy and apoptosis in GBM cells. MET combined with ART treatment effectively suppressed the viability, mono-cloning ability, migration and invasion capacities, as well as metastatic ability of GBM cells. The underlying mechanism involved modulation of the ROS-AMPK-mTOR axis, which was confirmed using 3-methyladenine and rapamycin to inhibit or promote the effects of MET combined with ART, respectively. The study findings suggest that MET used in combination with ART can induce autophagy-dependent apoptosis in GBM cells by activating the ROS-AMPK-mTOR pathway, providing a potential new treatment for GBM.

Accuracy of 14 intraocular lens power calculation formulas in extremely long eyes.

PURPOSE: To compare the accuracy of 14 formulas in calculating intraocular lens (IOL) power in extremely long eyes with axial length (AL) over 30.0 mm. METHODS: In this retrospective study, 211 eyes (211 patients) with ALs > 30.0 mm were successfully treated with cataract surgery without complications. Ocular biometric parameters were obtained from IOLMaster 700. Fourteen formulas were evaluated using the optimized A constants: Barrett Universal II (BUII), Kane, Emmetropia Verifying Optical (EVO) 2.0, PEARL-DGS, T2, SRK/T, Holladay 1, Holladay 2, Haigis and Wang-Koch AL adjusted formulas (SRK/Tmodified-W/K, Holladay 1modified-W/K, Holladay 1NP-modified-W/K, Holladay 2modified-W/K, Holladay 2NP-modified-W/K). The mean prediction error (PE) and standard deviation (SD), mean absolute errors (MAE), median absolute errors (MedAE), and the percentage of prediction errors (PEs) within ± 0.25 D, ± 0.50 D, ± 1.00 D were analyzed. RESULTS: The Kane formula had the smallest MAE (0.43 D) and MedAE (0.34 D). The highest percentage of PE within ± 0.25 D was for EVO 2.0 (37.91%) and the Holladay 1NP-modified-W/K formulas (37.91%). The Kane formula had the highest percentage of PEs in the range of ± 0.50, ± 0.75, ± 1.00, and ± 2.00 D. There was no significant difference in PEs within ± 0.25, ± 0.50 ± 0.75 and ± 1.00 D between BUII, Kane, EVO 2.0 and Wang-Koch AL adjusted formulas (P > .05) by using Cochran's Q test. The Holladay 2modified-W/K formula has the lowest percentage of hyperopic outcomes (29.38%). CONCLUSIONS: The BUII, Kane, EVO 2.0 and Wang-Koch AL adjusted formulas have comparable accuracy for IOL power calculation in eyes with ALs > 30.0 mm.

Effect of vacancy ordering on the grain growth of Ge2Sb2Te5film.

Ge2Sb2Te5(GST) is the most widely used matrix material in phase change random access memory (PCRAM). In practical PCRAM device, the formed large hexagonal phase in GST material is not preferred, especially when the size of storage architecture is continually scaling down. In this report, with the aid of spherical-aberration corrected transmission electron microscopy (Cs-TEM), the grain growth behavior during thein situheating process in GST alloy is investigated. Generally, the metastable face-centered-cubic (f-) grain tends to grow up with increasing temperature. However, a part of f-phase nanograins with {111} surface plane does not grow very obviously. Thus, the grain size distribution at high temperature shows a large average grain size as well as a large standard deviation. When the vacancy ordering layers forms at the grain boundary area in the nanograins, which is parallel to {111} surface plane, it could stabilize and refine these f-phase grains. By elaborating the relationship between the grain growth and the vacancy ordering process in GST, this work offers a new perspective for the grain refinement in GST-based PCRAM devices.

Study on the enlargement index of femtosecond laser-assisted capsulorhexis in 2-6-year-old patients with congenital cataract.

BACKGROUND: To identify the capsule enlargement index after femtosecond laser-assisted anterior capsulorhexis in 2-6-year-old children who underwent congenital cataract surgery. METHODS: In this prospective case series study, femtosecond laser-assisted anterior capsulorhexis was performed in patients with congenital cataract, aged 2-6 years. The actual achieved capsulorhexis diameters were measured with Digimizer version 4.2.6. Correlation coefficient (r) and multiple linear regression analysis were used to evaluate the variables that could potentially influence anterior capsulorhexis enlargement index (E). RESULTS: This prospective study enrolled 28 eyes of 22 patients with congenital cataract. The mean age of the patients at surgery was 4.67 years ±1.54 (standard deviation [SD]). "E" of the 28 cases was 1.211 ± 0.039 (SD). Correlation analysis showed that "E" correlated significantly with the anterior chamber depth (ACD) (r = - 0.469, p = 0.021) and axial length (AL) (r = 0.452, p = 0.027). The following formula was developed by using multivariable linear regression analysis: Predicted E = 1.177-0.052 × ACD + 0.009 × AL, R2 = 0.346 (F = 4.396, p = 0.046). CONCLUSIONS: The anterior capsulorhexis enlargement index and its calculation formula could help to set up an accurate programmed capsulorhexis diameter for femtosecond laser-assisted congenital cataract surgery in children aged 2-6 years. Thus, an appropriate actual capsulorhexis diameter could be achieved.

Prevalence of reduced visual acuity among school-aged children and adolescents in 6 districts of Changsha city: a population-based survey.

BACKGROUND: To calculate and evaluate the prevalence of reduced uncorrected distant visual acuity (UCDVA) in primary, middle and high schools in 6 districts of Changsha, Hunan, China. METHODS: A population-based retrospective study was conducted in 239 schools in 6 districts of Changsha. After routine eye examination to rule out diseases that can affect refraction, 250,980 eligible students from primary, middle and high schools were enrolled in the survey. Then the uncorrected distant and near visual acuity of each eye were measured. Categories of schools, districts, grades, eye exercises and sports time were also documented and analyzed. RESULTS: The overall prevalence of reduced UCDVA was 51.8% (95% confidence interval [CI]: 51.6-52.0%) in 6 districts of Changsha. Results of individual districts were as follows: Furong district 59.9%(95% CI: 57.9-61.8%), Tianxin district 62.3%(95% CI: 60.5-64.0%), Wangcheng district 47.8%(95% CI: 46.8-48.8%), Kaifu district 58.5%(95% CI: 58.0-58.9%), Yuhua district 47.0%(95% CI: 46.7-47.4%) and Yuelu district 52.6%(95% CI: 52.3-52.9%). The proportion of normal VA is seen to decrease from primary grade 3. The proportion of mildly reduced UCDVA is higher in primary grade 1 and 2. The proportion of moderately reduced UCDVA remains similar during 12 grades. The proportion of severely reduced UCDVA increases with grades. Multivariate analysis shows that the prevalence of reduced UCDVA is higher in key schools (risk ratio [RR] = 1.47, 95% CI 1.44-1.50) than non-key schools. CONCLUSIONS: According to the existing data analysis results, the prevalence of reduced UCDVA among primary, middle and high school students in Changsha is very high. Some effective measures need to be taken to prevent it.

Ocular Dominance Shift in Refractive Cataract Surgery: A prospective, observational study.

PURPOSE: To explore the features of the dominant and non-dominant eyes in patients with cataracts and predict ocular dominance shift (ODS) based on preoperative indicators. DESIGN: and setting: This prospective, observational study was conducted in Changsha Aier Eye Hospital in Changsha, Hunan province, China. METHODS: Patients with age-related cataracts who underwent unilateral cataract surgery were enrolled in this study. Before the procedure, uncorrected visual acuity (UCVA) was assessed, and non-cycloplegic subjective refraction evaluations were conducted to determine best-corrected visual acuity (BCVA). Total astigmatism, corneal astigmatism, and intraocular astigmatism were measured using OPD-Scan III. Cataract type was assessed using slit-lamp biomicroscopy based on the Lens Opacities Classification System III (LOCS III). Ocular dominance (OD) was determined under corrected conditions using the hole-in-card test. Follow-up visits occurred at 1 day, 1 week, and 1-month post-surgery. After 1 month, OD was re-evaluated, and participants completed the Catquest-9SF questionnaire. RESULTS: 94 patients (188 eyes) were enrolled in the study. The analysis showed that the ODS rate of unilateral cataract surgery was 40.4%. In addition, age, uncorrected visual acuity of non-dominant eye, posterior subcapsular cataract and total astigmatism are risk factors for ODS. Besides, no difference in vision-related quality of life was detected between patients who had ODS and those who did not. CONCLUSIONS: We identified several preoperative parameters as potential risk factors of ODS after cataract surgery. These findings provide guidance for predicting changes in the dominant eye, thus improve the precise selection of intraocular lenses and the implementation of monovision strategies.

Tuning the Crystallization Mechanism by Composition Vacancy in Phase Change Materials.

Interface-influenced crystallization is crucial to understanding the nucleation- and growth-dominated crystallization mechanisms in phase-change materials (PCMs), but little is known. Here, we find that composition vacancy can reduce the interface energy by decreasing the coordinate number (CN) at the interface. Compared to growth-dominated GeTe, nucleation-dominated Ge2Sb2Te5 (GST) exhibits composition vacancies in the (111) interface to saturate or stabilize the Te-terminated plane. Together, the experimental and computational results provide evidence that GST prefers (111) with reduced CN. Furthermore, the (8 - n) bonding rule, rather than CN6, in the nuclei of both GeTe and GST results in lower interface energy, allowing crystallization to be observed at the simulation time in general PCMs. In comparison to GeTe, the reduced CN in the GST nuclei further decreases the interface energy, promoting faster nucleation. Our findings provide an approach to designing ultrafast phase-change memory through vacancy-stabilized interfaces.

Repressing iron overload ameliorates central post-stroke pain via the Hdac2-Kv1.2 axis in a rat model of hemorrhagic stroke.

JOURNAL/nrgr/04.03/01300535-202412000-00027/figure1/v/2024-04-08T165401Z/r/image-tiff Thalamic hemorrhage can lead to the development of central post-stroke pain. Changes in histone acetylation levels, which are regulated by histone deacetylases, affect the excitability of neurons surrounding the hemorrhagic area. However, the regulatory mechanism of histone deacetylases in central post-stroke pain remains unclear. Here, we show that iron overload leads to an increase in histone deacetylase 2 expression in damaged ventral posterolateral nucleus neurons. Inhibiting this increase restored histone H3 acetylation in the Kcna2 promoter region of the voltage-dependent potassium (Kv) channel subunit gene in a rat model of central post-stroke pain, thereby increasing Kcna2 expression and relieving central pain. However, in the absence of nerve injury, increasing histone deacetylase 2 expression decreased Kcna2 expression, decreased Kv current, increased the excitability of neurons in the ventral posterolateral nucleus area, and led to neuropathic pain symptoms. Moreover, treatment with the iron chelator deferiprone effectively reduced iron overload in the ventral posterolateral nucleus after intracerebral hemorrhage, reversed histone deacetylase 2 upregulation and Kv1.2 downregulation, and alleviated mechanical hypersensitivity in central post-stroke pain rats. These results suggest that histone deacetylase 2 upregulation and Kv1.2 downregulation, mediated by iron overload, are important factors in central post-stroke pain pathogenesis and could serve as new targets for central post-stroke pain treatment.

Adiponectin Mediates the Protection of H2S Against Chronic Restraint Stress-Induced Cognitive Impairment via Attenuating Hippocampal Damage.

Emerging evidence shows that chronic restraint stress (CRS) can induce cognitive dysfunction, which involves in hippocampal damage. Our recent research reveals that hydrogen sulfide (H2S), a novel gasotransmitter, protects against CRS-induced cognitive impairment, but the underlying mechanism remains unclear. Adiponectin, the most abundant plasma adipokine, has been shown to elicit neuroprotective property and attenuate cognitive impairment. Hence, the present work was aimed to explore whether adiponectin mediates the protective effect of H2S on CRS-induced cognitive impairment by inhibiting hippocampal damage. Results found that administration of Anti-Acrp30, a neutralizing antibody of adiponectin, obviously reverses sodium hydrosulfide (NaHS, an exogenous H2S donor)-induced the inhibition on CRS-induced cognitive impairment according to Y-maze test, Novel object recognition (NOR) test, and Morris water maze (MWM) test. In addition, Anti-Acrp30 blocked the protective effect of NaHS on hippocampal apoptosis in rats-subjected with CRS as evidenced by the pathological changes in hippocampus tissues in hematoxylin and eosin (HE) staining and the increases in the amount of the condensed and stained to yellowish-brown or brownish yellow neuron nucleuses in terminal deoxynucleotidyl transferase transfer-mediated dUTP nick end-labeling (TUNEL) staining as well as the expression of hippocampal pro-apoptotic protein (Bax), and a decrease in the expression of hippocampal anti-apoptotic protein (Bcl-2). Furthermore, Anti-Acrp30 mitigated the inhibitory effect of NaHS on CRS-induced oxidative stress as illustrated by the up-regulation of malondialdehyde (MDA) content and the down-regulation of superoxide dismutase (SOD) activity and glutathione (GSH) level in the hippocampus. Moreover, Anti-Acrp30 eliminated NaHS-induced the reduction of endoplasmic reticulum (ER) stress-related proteins including binding immunoglobulin protein (BIP), C/EBP homologous protein (CHOP), and Cleaved Caspase-12 expressions in the hippocampus of rats-exposed to CRS. Taken together, these results indicated that adiponectin mediates the protection of H2S against CRS-induced cognitive impairment through ameliorating hippocampal damage.

Comparison of IOL Power Calculation Formulas for a Trifocal IOL in Eyes With High Myopia.

PURPOSE: To analyze the results of new intraocular lens (IOL) formulas (Emmetropia Verifying Optical [EVO], Kane, Olsen, and Barrett Universal II), traditional formulas (Haigis and SRK/T), and modified Wang-Koch axial length adjustment formulas with the SRK/T and Holladay 1 (SRK/Tmodified-W/K and H1modified-W/K) in Chinese patients with long eyes. METHODS: In this retrospective case series, patients with an axial length of 26 mm or greater having uneventful femtosecond laser-assisted cataract surgery with one trifocal IOL model were enrolled. The actual postoperative spherical equivalent of the manifest refraction was compared with the formula-predicted refraction based on the implanted IOL power. A subgroup analysis was performed based on the axial length. RESULTS: A total of 113 eyes was enrolled. Using User Group for Laser Interference Biometry constants, the modified Wang-Koch formulas had the lowest percentage of eyes with hyperopic outcomes. The Barrett Universal II, Olsen, Kane, and EVO 2.0 formulas produced a statistically lower median absolute error than the SRK/Tmodified-W/K and SRK/T formulas (P < .05). The Barrett Universal II formula produced higher percentages of eyes within ±0.50 diopters (D) of the prediction error than the SRK/T formula (P < .05). In eyes with axial lengths of less than 28 mm, there were no significant differences in the prediction accuracy of the eight formulas. In eyes with axial lengths of 28 mm or greater, the new IOL formulas yielded the lowest median absolute error, followed by the H1modified-W/K and Haigis formulas. The SRK/Tmodified-W/K formula had the highest mean absolute error and the lowest percentages of eyes within ±0.25 and ±0.50 D of endpoint. The traditional formulas yielded the highest risk of refractive surprise. CONCLUSIONS: All formulas achieved good results in eyes with axial lengths of less than 28 mm with trifocal IOL implanted. The newer formulas tend to produce better outcomes for eyes with high myopia. The SRK/Tmodified-W/K formula provided improved accuracy only in eyes with axial lengths of 30 mm or greater. [J Refract Surg. 2021;37(8):538-544.].

Safety of implantable Collamer lens implantation without ophthalmic viscosurgical device: A retrospective cohort study.

To compare the safety of implantable Collamer lens (ICL) implantation with and without ophthalmic viscosurgical device (OVD).A total of 148 eyes underwent a conventional ICL implantation with OVD (OVD group), and 112 eyes underwent a modified ICL implantation without OVD (OVD-free group). The balanced salt solution was used to load ICL and maintain the anterior chamber in the OVD-free group. The surgical time, postoperative uncorrected distance visual acuity, intraocular pressure, endothelial cell density (ECD), and percentage of hexagonal cells were compared between the OVD and the OVD-free groups.No significant differences were detected in uncorrected distance visual acuity, intraocular pressure, ECD, and percentage of hexagonal cells at any time post-surgery between the 2 groups (P > .05). The mean ECD loss was 1.9% in the OVD-free group and 2.3% in the OVD group at 2 years post-surgery (P = .680). The surgical time was much shorter in the OVD-free group than that in the OVD group (P ≤ .001). None of the following occurred at any time during the 2-year follow-up period in both groups: cataract formation, macular degeneration, or any other vision-threatening complications.OVD-free ICL implantation presented satisfactory results for safety. Compared to OVD, the OVD-free technique had the advantages of decreased surgical time, increased efficiency, and reduced cost.

Sub-Tenon Sustained Controllable Delivery of Dexamethasone for Treating Severe Acute Experimental Uveitis.

PURPOSE: To evaluate the efficacy of dexamethasone (DXM) through sub-tenon sustained controllable drug delivery system (SSCDDS) for treating severe acute experimental uveitis. METHODS: Rabbits were treated with either DXM (treated group) or normal saline (control group) through SSCDDS. Clinical signs of uveitis were assessed at days 1, 3, 5, 7, and 14 after treatment. Histopathologic examinations were performed to evaluate inflammatory cell infiltration on posttreatment days 7 and 14. RESULTS: All signs of experimental uveitis were reduced by SSCDDS of DXM according to clinical criteria, and the treated group had significantly less inflammation than the control group (p<0.05). Histopathologic examinations showed severe inflammation and marked inflammatory cell infiltration in the control group, but minimal inflammation in the treated group. CONCLUSIONS: Sub-tenon sustained controllable delivery of DXM effectively suppresses severe acute inflammation in a rabbit model of uveitis. The proposed minimal invasive system might be a promising candidate for managing severe ocular diseases.

Outcomes of cataract surgery in eyes with ocular melanoma treated with iodine-125 brachytherapy.

PURPOSE: To evaluate visual and surgical outcomes of cataract surgery in eyes with a history of iodine-125 (I125) brachytherapy for ocular melanoma. SETTING: Department of Ophthalmology, David Geffen School of Medicine at UCLA and the Stein Eye Institute, Los Angeles, California, USA. DESIGN: Retrospective case series. METHODS: Patients with ocular melanoma treated by I125 brachytherapy who subsequently had cataract surgery were evaluated. The recorded data included tumor size, location, preoperative ocular comorbidities, corrected distance visual acuity (CDVA), operative complications, and brachytherapy-related maculopathy before and after surgery. RESULTS: Thirty-two eyes of 32 patients were included. The mean age at the time of cataract surgery was 66.1 years. The median follow-up was 53.5 months. There were no intraoperative complications. Eighteen eyes (56.3%) had a history of preoperative radiation retinopathy, 10 involving the macula. Between 2 weeks and 4 weeks postoperatively, 22 eyes (68.8%) had an improvement in CDVA (≥2 lines). Seven of 10 eyes that failed to improve had radiation maculopathy. By the last follow-up examination, 13 eyes (40.6%) had improved CDVA, 9 eyes (28.1%) were worse (≥2 lines), and 10 eyes (31.3%) were unchanged (within ±1 line). Of 15 eyes that lost CDVA gains achieved between 2 weeks and 4 weeks postoperatively, 9 eyes had new-onset or worsening maculopathy. Cataract surgery had no effect on local tumor control or distant metastasis. CONCLUSIONS: Cataract surgery after I125 brachytherapy for ocular melanoma improved CDVA in most eyes during the immediate postoperative period. Gains were often lost with further follow-up. Progression of radiation maculopathy was primarily responsible for subsequent visual decline.

Neuroprotective effect of melatonin on retinal ganglion cells in rats.

To investigate the neuroprotective effect of melatonin (MT) on retinal ganglion cells (RGCs) in rats with ischemia reperfusion injury (RIR), 24 healthy SD rats were randomly divided into two groups: group A and group B. RIR model was induced in the left eyes by increasing the pressure of the anterior chamber. Group A was treated with 10 % alcohol- normal saline (1 mL/kg/d, ip), while group B was treated with 0.5 % MT (1 mL/kg/d, ip). On the basis of the time interval between the left eyes RIR and the sacrifice, rats in both group A and group B were further divided into 3 subgroups: groups A1 and B1 (days 7), groups A2 and B2 (days 14), groups A3 and B3 (days 30), with 4 rats in each subgroup. 7 day before the sacrifice, 3 % fluorogold was bilaterally injected into superior colliculi and geniculate body. The eyes were enucleated after being sacrificed, and mounting of the retina from both eyes was performed on a slide and observed under a fluorescence microscope. Four photos were taken from each of the four quadrants of the retina. The labeled-RGCs were counted by using a computerized image analyzer. The rate of the labeled-RGCs was used for statistical analysis. Our results showed that, in group A, the rate of the labeled-RGCs was (77.16 +/- 6.35) %, (65.53 +/- 7.01) %, (53.85 +/- 4.38) % on day 7, 14 and 30. In group B, the rate of the labeled-RGCs was (81. 33 +/- 9.27) %, (79.80 +/- 8.36) %, (80. 34 +/- 11.05) % on day 7, 14 and 30. In group B, which was treated with MT after RIR, the rate of labeled-RGCs was significantly higher than that of group A on day 14 and day 30 (P<0.05). It is concluded that, in the RIR rats, MT therapy could increase the survival rate of the RGCs and could rescue and restore the injured RGCs.

Insulin-like growth factor I promotes oocyte maturation through increasing the expression and phosphorylation of epidermal growth factor receptor in the zebrafish ovary.

The resumption of oocyte meiosis is a critical step for the progression of oocyte development, which requires an intimate collaboration of a variety of hormones and growth factors. Insulin-like growth factor I (IGF-I) and epidermal growth factor (EGF) family are well recognized to promote oocyte maturation. However, the mechanism by which they coordinate this process remains unknown. The present study demonstrated that IGF-I can increase egfr mRNA and protein levels in follicle cell culture or intact follicles. This stimulation can be significantly inhibited by IGF-IR specific inhibitor, NVP-ADW742. The inhibitors against phosphatidylinositol-3-kinase (PI3K), phosphoinositide-dependent protein kinase 1 (PDK1) and Akt also dramatically abolished IGF-I-induced egfr expression, suggesting that the classical PI3K/Akt pathway mediated the action of IGF-I in this regulation. We further found that not only was the protein level of Egfr increased, but also the phosphorylation level was enhanced by IGF-I. Unlike egfr, IGF-I failed to stimulate the expression of Egf-like ligands whereas decreased the level of protein-tyrosine phosphatase, receptor type, kappa (ptprk), a protein tyrosine phosphatase. The oocyte maturation assay further confirmed that IGF-I initiates this regulation through its cognate receptor in the follicle cells. Taken together, IGF-I promoted oocyte maturation, in part at least, through Egf-like ligands/Egfr pathway. This study sheds light on the cross-talk between two important growth factors in the zebrafish ovary and the mechanism underlying the IGF-I induction on oocyte maturation.

Characterization of limbal stem cell deficiency by in vivo laser scanning confocal microscopy: a microstructural approach.

OBJECTIVE: To evaluate the cellular changes in the corneal epithelium and surrounding structures in limbal stem cell deficiency (LSCD) by using in vivo laser scanning confocal microscopy. METHODS: This was a prospective comparative study that included 27 eyes of 20 patients with LSCD and 12 eyes of 10 healthy subjects. All subjects underwent slitlamp examination, and LSCD was classified into 3 groups on the basis of clinical presentation. Confocal imaging of the central cornea and 4 locations of limbus was performed. Morphologic characteristics of the corneal epithelium were studied. The basal epithelial cell density and subbasal nerve density in the central cornea were calculated, and a potential correlation between the decrease in basal epithelial cell density and subbasal nerve density in LSCD was investigated. RESULTS: The wing and basal epithelial cells became progressively metaplastic, and the basal epithelial cell density and subbasal nerve density in the early and intermittent stages decreased significantly compared with controls (all P < .01). Normal basal epithelial cell morphology was completely lost and subbasal nerves were absent in the late stage of LSCD. The decrease in basal cell density correlated with the decrease in subbasal nerve density in patients with LSCD (P = .03). CONCLUSIONS: There are significant microstructural changes associated with early LSCD. These cellular changes could help to understand the disease process and classify and monitor limbal stem cell dysfunction.

Accuracy of Scheimpflug Holladay equivalent keratometry readings after corneal refractive surgery.

PURPOSE: To determine the accuracy of Pentacam Scheimpflug system Holladay equivalent keratometry (K) readings (EKRs) in calculating intraocular lens (IOL) power after corneal refractive surgery, including laser in situ keratomileusis (LASIK), photorefractive keratectomy (PRK), and radial keratotomy (RK). SETTING: Jules Stein Eye Institute, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, California, USA. METHODS: In this combined retrospective and prospective clinical study, patients who had cataract surgery after corneal refractive surgery were recalled to have Scheimpflug imaging of the operated cornea and Holladay EKR determination. The Holladay EKR was compared with a gold-standard K value, which was the back-calculated value using the original Hoffer formula based on the actual surgical outcomes. Eyes without a history of refractive surgery served as controls. RESULTS: Twenty-seven patients (41 eyes) were evaluated; 26 eyes had previous LASIK or PRK and 15, previous RK. Forty-one eyes served as controls. The mean error of the Holladay EKR in eyes with previous LASIK or PRK was +1.84 diopters (D) (range +0.66 to +4.94 D). The mean error in eyes with previous RK was +2.17 D (range +0.48 to +3.09 D). In the control eyes, the mean EKR error was +1.38 D (range -0.17 to +2.54 D). CONCLUSIONS: The Holladay EKR calculated using version 1.16r04 of the Scheimpflug system software was inaccurate in virgin corneas and in those with a history of LASIK, PRK, or RK using current IOL power calculation formulas. The Scheimpflug power measurements were consistently steeper than the true corneal power.