Journal of Cataract and Refractive Surgery

Article	Citations
Reply: Outcomes of femtosecond laser–assisted cataract and refractive lens surgery in patients with prior radial keratotomy	77
Open-angle glaucoma and Fuchs dystrophy	71
Comment on: Late-onset toxic anterior segment syndrome after possible aluminum and silicon contaminated intraocular implantation	52
OCT to identify macular changes not clinically detectable in elderly patients with cataract	41
Reply: Effect of longitudinal and torsional ultrasound on corneal endothelial cells: experimental study in rabbit eyes	38
Comment on: Light as a drug: prospective randomized evaluation and comparison of the effect of decreased illumination on visual recovery following cataract surgery	37
Let's talk about something uncomfortable	33
Pseudophakic retinal detachment: a ticking time bomb	33
Agreement between 2 SS-OCT biometry devices	32
Comparison of two side-port incisions in phacoemulsification	32
Comment on: Incidence and factors for pseudoaccommodation after monofocal lens implantation: the Monofocal Extended Range of Vision study	32
Safety and effectiveness comparison of a new cohesive ophthalmic viscosurgical device	32
Lens Morphology in Cataract Patients with Zonula Dialysis by Anterior Segment Optical Coherence Tomography	32
Late approach for LASIK flap striae	32
Comparison of posterior capsule rupture rates during phacoemulsification using 3D heads-up visualization system and traditional microscopes	32
Method to analyze the refractive outcomes of online intraocular lens power formulas	31
Posterior capsule opacification with two similar-design hydrophobic acrylic intraocular lenses: 3-year results of a randomized controlled trial	31
Comparison of two different intraocular lenses used in the modified Yamane technique	31
Comment on: Ray-tracing–guided myopic LASIK: real-world clinical outcomes	30
Pilocarpine HCl 1.25% for treatment of presbyopia after laser vision correction: pooled analysis of two phase 3 randomized trials (GEMINI 1 and 2)	29
Should enhanced monofocal intraocular lenses be the standard of care? An evidence-based appraisal by the ESCRS Functional Vision Working Group	28
Clinical performance after implantation of an EDOF intraocular lens in the dominant eye and a presbyopia-correcting intraocular lens in the nondominant eye	28
Study on the relationship between bacterial endotoxin and the onset of toxic anterior segment syndrome	28
Clinical and refractive outcomes after topography-guided refractive surgery planned using Phorcides surgery planning software	27
Patient-reported quality of vision in a prospective randomized contralateral-eye trial comparing LASIK and small-incision lenticule extraction	26

Anti-inflammatory medication use after cataract surgery: online survey of practice patterns	26
Accuracy of predicted refraction using two swept-source optical coherence biometers and an intraoperative aberrometer	26
Royal College of Ophthalmologists' National Ophthalmology Database study of cataract surgery: report 11, techniques and complications of local anesthesia for cataract surgery in the United Kingdom	25
Comparative effectiveness of VISUMAX 800 with keratorefractive lenticule extraction and FS-LASIK in the treatment of myopic astigmatism	24
Distribution and associated factors of crystalline lens volume in noncataract adolescents and adults and patients with cataract in a Chinese population	23
Longitudinal observation of posterior capsule opacification in pediatric eyes with Marfan syndrome after in-the-bag intraocular lens implantation	23
Potential environmental effect of reducing the variation of disposable materials used for cataract surgery	23
Comment on: Assessing chatbots ability to produce leaflets on cataract surgery: Bing AI, chatGPT 3.5, chatGPT 4o, ChatSonic, Google Bard, Perplexity, and Pi	23
Comment on: Efficacy of intracameral moxifloxacin in prevention of post-cataract surgery endophthalmitis: a randomized controlled trial	23
Sustaining sustainability	22
Refractive surgery as a treatment tool for strabismus: systematic review	22
Phase retardation and corneal sublayer thickness repeatability using ultrahigh-resolution polarization-sensitive OCT	22
Comment on: Clinical and histopathological findings in the dead bag syndrome	22
Comparison of higher-order corneal irregularities in eyes with oblique, with-the-rule, and against-the-rule astigmatism	22
Comment on: Predicted vs measured posterior corneal astigmatism for toric intraocular lens calculations	21
Femto-masking: laser-generated apertures to extend depth of focus and reduce optical aberrations in intraocular lenses	21
Rotational stability of a new hydrophobic acrylic intraocular lens platform	21
3D X-ray computed tomography in the analyses of intraocular lenses explanted because of postoperative opacification	21
Comparative study of FLACS vs conventional phacoemulsification for cataract patients with high myopia	20
Nationwide study of the association between keratoconus and autism spectrum disorder	20
Visual and refractive outcomes after bilateral implantation of an enhanced monofocal intraocular lens: prospective study	20
Optimization of crystalline lens refractive index to improve the accuracy of intraocular lens power calculation in patients with dense cataract	19
Haptics and axis stability of customized vertical implantable collamer lens implantation	19
Comparative study of refractive and visual quality after wavefront-optimized FS-LASIK for angle kappa adjustment in dominant and nondominant eyes	19
Evaluating ASC-4 transfer rates in cataract surgery: insights into timing and causes of hospital transfers	19
Perception of visual outcomes in patients after delayed compared with immediately sequential bilateral cataract surgery	19
Posterior synechiae and cataract formation as a late complication of a foldable iris-fixated phakic intraocular lens	19
Reply: Clinical data registry comparing outcomes of two light adjustable lenses	19
Multifocal intraocular lens implantation in children with unilateral congenital cataracts	18
In-the-Bag Uveitis–Glaucoma–Hyphema Syndrome with Iris Chafing: Anterior Segment OCT	18
Comment on: Impact of spherical aberration on visual quality and depth of focus	18
Comment on: Cataract surgery in herpes simplex virus ocular disease	18
Comment on: Evidence-based functional classification of simultaneous vision intraocular lenses: seeking a global consensus by the ESCRS Functional Vision Working Group	18
Artificial intelligence chatbot and Academy Preferred Practice Pattern® Guidelines on cataract and glaucoma	18
Cataract Extraction with Capsular Bag Scleral Fixation in a Patient with a Congenital Lens Coloboma	18
Comment on paper: “Depth of focus as a function of spherical aberration using adaptive optics in pseudophakic subjects” by Tabernero et al	18
Reducing ophthalmic surgical waste through electronic instructions for use: a multisociety position paper	18
Hyper-reflective Dots and Curl in True Exfoliation Syndrome	18
Reply: Light as a drug: prospective randomized evaluation and comparison of the effect of decreased illumination on visual recovery following cataract surgery	17
Reply: Automated and subjective refraction with monofocal, multifocal, and EDOF intraocular lenses: review	17
The JCRS 100 Club	17
Structural integrity of eyelets in a hydrophobic intraocular lens with four-point scleral fixation	17
Pupil size measurements with a multifunctional aberrometer/coherence interferometer/tomographer and two infrared-based pupillometers	17
Comment on: New keratoconus staging system based on OCT	17
Comment on: Clinical and refractive outcomes after topography-guided refractive surgery planned using Phorcides surgery planning software	17
RE: Generative Artificial Intelligence for Postoperative Parameters Prediction in Implantable Collamer Lens Surgery	16
Reducing stress in the operating room: stress relief for the surgeon	16
Long-term results of hyperopic ablations using alcohol-assisted PRK and FS-LASIK: comparative study	16
Efficacy of remote care in cataract surgery: systematic review	15
Real-world efficacy, safety, and usability of a microvolume eyedrop delivery device in glaucoma: prospective randomized crossover trial	15

DICOM: What it is and why it matters	15
Reply: Anchor-assisted capsular bag IOL implantation to correct subluxated lenses in children with Marfan syndrome: long-term follow-up	15
VAULT: vault accuracy using deep learning technology: new image-based artificial intelligence model for predicting implantable collamer lens postoperative vault	15
Long-term results of a new posterior chamber phakic intraocular lens in patients with high myopia: 5-year results	15
Evaluation of a new device to treat negative dysphotopsia	15
Keratorefractive Lenticule Extraction for myopia and myopic astigmatism using a 2 MHz femtosecond laser: 12-month refractive outcomes.	14
Long-term effect of canaloplasty on intraocular pressure and use of intraocular pressure–lowering medications in patients with open-angle glaucoma	14
Three-year comparison of two mix-and-match strategies: enhanced monofocal and trifocal vs enhanced monofocal and trifocal EDOF intraocular lenses	14
Effect of residual sphere on uncorrected visual acuity and satisfaction in patients with monofocal and multifocal intraocular lenses	14
Comparison of visual outcomes of bilateral dual-technology diffractive intraocular lens vs blended enhanced monofocal with dual-technology intraocular lens	14
Visual and Refractive Outcomes after Keratorefractive Lenticle Extraction (KLEx) in Moderate and High Myopia: Analysis of more than 1500 eyes	14
FS-LASIK for the treatment of moderate-to-high hyperopia	14
Outcomes of manual arcuate keratotomy with compression sutures for high regular postkeratoplasty astigmatism	14
Long-term efficacy and safety profiles after posterior chamber phakic intraocular lens implantation in eyes with more than 10 years of follow-up	14
Age-related appearance of lamellar structures in lens capsule of cataractous eyes and its pathological significance	14
Impact of topographic hot spots on the refractive outcomes of combined DMEK and cataract surgery	14
Comparison of visual function and patient-reported outcomes between two full range of field intraocular lenses: a randomized controlled study	14
Enhancing Cataract Surgery Training Through a Secure Microscope-Integrated Live Video Supervision System	14
Visual performance and subjective experience 3 months and 12 months after combined implantation of 2 new complementary continuous phase multifocal intraocular lenses	14
Comment on: Relative efficacy of intracameral moxifloxacin injection methods	13
One-year follow-up of a multifocal intraocular lens with optimized elevated phase shift	13
Influence of Nd:YAG laser capsulotomy on toric intraocular lens rotation and change in cylinder power	13
Attitudes and access to surgical video recording among ophthalmology trainees in Scotland	13
Predicting intraocular lens tilt using a machine learning concept	13
Relative efficacy of intracameral moxifloxacin injection methods	13
Characterization of vault with two models of posterior chamber phakic intraocular lenses	13
Documenting the subjective patient experience of first vs second eye during immediately sequential bilateral cataract surgery	13
Depth of field or depth of focus?	13
Reply: Relative efficacy of intracameral moxifloxacin injection methods	13
Leaner and greener	12
Evaluating text-based generative artificial intelligence models for patient information regarding cataract surgery	12
Comment on: Variations in morphology and patency of disposable hydrodissection cannulas used in cataract surgery	12
Comparison of long-term outcomes of simultaneous accelerated corneal crosslinking combined with intracorneal ring segment or topography-guided PRK	12
Evaluation of corneal biomechanical behavior in vivo for healthy and keratoconic eyes using the stress–strain index	12
Modern cataract surgery with simplified technology: new trend?	12
Acute-onset postoperative endophthalmitis after cataract surgery performed by resident and attending physicians at a university teaching hospital	12
Little pearls for routine cases	12
Fibromyalgia and LASIK: outcomes, complication rates, and ocular pain risk	12
Factors predisposing to intraoperative floppy-iris syndrome: An up-to-date meta-analysis	11
Innovative utilization of ultra-wide field fundus images and deep learning algorithms for screening high-risk posterior polar cataract	11
Global consensus on the evidence-based functional classification of simultaneous vision IOLs	11
Erratum to: Spherical aberration for expanding depth of focus. Joaquín Fernández, MD, PhD, Manuel Rodríguez-Vallejo, OD, PhD, Noemí Burguera, OD, PhD, Carlos Rocha-de-Lossada, MD, David P. Piñero, OD,	11
Size variability and fitting of 30-gauge thin-wall needles and 3-piece intraocular lens haptics for the flanged intrascleral fixation technique	11
Longitudinal outcomes of iStent inject with cataract surgery compared with cataract surgery alone: real-world data from the Fight Glaucoma Blindness registry	11
Mix-and-match vs bilateral trifocal and bilateral EDOF intraocular lens implantation: the spline curve battle	11
Trends in patient, surgeon, and procedural characteristics of intraocular lens exchange among Medicare beneficiaries 2011 to 2020	11
Prediction model of the horizontal trabecular iris angle after phakic posterior chamber implantable intraocular lens surgery	11
Paper waste from instructions for use brochures in cataract surgery implant packaging in Europe and the United States	11
Customized corneal crosslinking with excimer laser–assisted epithelium removal for progressive keratoconus: 1-year results	11
Posterior lenticonus: slitlamp retroillumination and AS-OCT correlation	11
Immunohistochemical findings of lens capsules obtained from patients with dead bag syndrome	11
Comparison of the new Hoffer QST with 4 modern accurate formulas	11
Comment on: Novel spore-like calcification on a hydrophilic acrylic intraocular lens	11
Comment on: Double-flanged polypropylene technique: 5-year results	10
Unilateral vortex keratopathy of unknown etiology	10
Comparative evaluation of multiple nomograms for predicting postoperative vault after implantable collamer lens surgery	10
Prescription patterns in DMEK: European survey	10
Evaluation of long-term clinical outcomes after toric implantable collamer lens implantation	10
Comment on: Intraocular lens rotational stability after cataract surgery with and without primary posterior continuous curvilinear capsulorhexis	10
Hyperopic LASIK and postoperative corneal steepness: revisiting the 49-diopter limit	10
Impact of anterior capsule polishing on capsule opacification and capsule bend after age-related cataract surgery	10
Suboptimal visual outcome after femto-LASIK ablation in a high myopic patient	10
Corneal scar after ulcer in a young patient demanding visual restoration in a timely fashion treated with PTK + topo-guided PRK	10
Visual outcomes and complications of combined vs sequential cataract surgery and pars plana vitrectomy: multicenter database study	10
Initial results of DMEK combined with cataract surgery and implantation of the light-adjustable lens	10
Accuracy of intraocular lens power calculation in patients with endothelial dystrophy without edema	10
Combination of iris vessel area density and surgery interval as the predictor of perceived pain during consecutive second-eye cataract surgery	10
Enhancing visibility and efficiency in toric intraocular lens surgery with the pivot technique and an assistant-mounted guidance system	10
Artificial intelligence and surgery: what's next?	10
Evaluation of intraoperative aphakic eye axial length measurements using swept-source OCT	10
Visual outcomes, contrast sensitivity, and defocus profile with an aspheric monofocal intraocular lens using positive spherical aberration	10
Visual performance of a novel wavefront shaping EDOF intraocular lens on a new hydrophobic acrylic platform	10
Comment on: Influence of ocular biometric parameters such as effective lens position, keratometry, and axial length on near add power of multifocal intraocular lens	10
Presbyopia correction using the monocular bi-aspheric ablation profile in myopic eyes	10
Large healthcare system evaluation of postoperative moxifloxacin ophthalmic solution cross-reactivity	10
Changes in straylight after cataract surgery	10
ASCRS clinical advisory on intracameral moxifloxacin injection for infection prophylaxis	10
Reducing the Carbon Footprint of Refractive Surgery Through Same-Day Postoperative Care	9
Optical confirmation by a thick-lens formula of the optimized A-constant (as calculated by a thin-lens formula) of a new intraocular lens	9
Inferior-Superior Epithelial Thickness Difference: Zone-Specific Analysis Across Topographic Asymmetry	9

Comment on: Safety and effectiveness comparison of a new cohesive ophthalmic viscosurgical device	9
Flange depth for scleral pocket vs no pocket techniques for intrascleral intraocular lens fixation	9
Histopathological Characteristics of Zonular Fibers and Lens Capsule and Their Relationship to Clinical Features in Intraocular Lens Dislocation	9
Enlargement of main corneal incision: clinical intraindividual comparison of two preloaded intraocular lens injectors	9
Comment on: Anterior vitreous detachment and retrolental material during cataract surgery: incidence and risk factors, with pathological evidence	9
Comparison of cataract surgery outcomes in patients with type 1 vs type 2 diabetes mellitus and patients without diabetes mellitus	9
Effect of a topical antibiotic and povidone-iodine vs povidone-iodine alone on conjunctival flora:systematic review and meta-analysis	9
Precision of a new SS-OCT biometer to measure anterior segment parameters and agreement with 3 instruments with different measurement principles	9
Occlusion Break Surge Performance of a Next Generation Phacoemulsification System	9
Light as a drug: prospective randomized evaluation and comparison of the effect of decreased illumination on visual recovery after cataract surgery	9
Reply: Ray-tracing–guided myopic LASIK: real-world clinical outcomes	9
Erratum to: Intraocular lens power calculation accuracy after keratorefractive lenticule extraction with the novel ESCRS post-keratorefractive surgery calculator	9
Effect of simulated lenticular debris on corneal endothelial cells: experimental study in rabbit eyes	9
Effect of suction angle on zonular fibers during residual cortex removal in phacoemulsification using finite element modeling	9
Efficacy of segmented axial length and artificial intelligence approaches to intraocular lens power calculation in short eyes	9
Contemporary statistical analysis of refractive error in adults, pseudophakia, and refractive surgery	9
Comparison of epithelium-on customized remodeled vision and epithelium-off accelerated crosslinking in keratoconus treatment: 2-year study	9
Erratum to: Lu NJ, Hafezi F, Rozema JJ, Hillen M, Hafezi N, Zhang J, Koppen C. Repeatability of a Scheimpflug tonometer to measure biomechanical parameters before and after myopic refractive surgery.	9
Comparison of keratometry using SS-OCT and dual Scheimpflug-Placido imaging in postmyopic corneal refractive surgery eyes	9
Capsulotomy morphology in cataract surgery: comparison of five femtosecond lasers	9
Reflections	9
Complete anterior dislocation of the capsular bag–intraocular lens complex in pseudoexfoliation syndrome	9
Comparison of implantation of posterior chamber phakic IOL implantation and laser vision correction in terms of corneal endothelial cells: 3-year observational paired-eye study	9
Mapping of corneal birefringence in thin and asymmetric keratoconus corneas with ultrahigh-resolution polarization-sensitive OCT	8
Traumatic cataract with iridodialysis	8
Reply: Association between anterior chamber biometry and posterior capsular defects	8
Anterior chamber cytokine production and postoperative macular edema in patients with diabetes undergoing FLACS	8
Prediction of visual outcomes using virtual implantation of a trifocal intraocular lens in presbyopic lens exchange patients	8
Two point four million cataract surgeries: 30 years with the Swedish National Cataract Register, 1992-2021	8
Diagonal haptic capture of an acrylic intraocular lens - Longterm safety and efficacy	8
Evaluation of a visual acuity eHealth tool in patients with cataract	8
Zonular and capsular bag disorders: a hypothetical perspective based on recent pathophysiological insights	8
Tackling the challenge of needless surgical waste in ophthalmology	8
Comment on: Efficacy of Intracameral Moxifloxacin in Prevention of Postcataract Surgery Endophthalmitis	8
Addressing corneal opacity after herpes zoster infection	8
Intraoperative complications and visual outcomes of cataract surgery in neovascular age-related macular degeneration	8
Functional outcomes after bilateral refractive lens exchange with a continuous-range-of-vision intraocular lens	8
Corneal sensitivity and ocular surface health in patients undergoing femtosecond LASIK retreatment for residual refraction	8
Improving refractive predictability with high-powered intraocular lenses: refractive implications of various optic designs	8
Comparative analysis of visual outcomes with 2 enhanced monofocal intraocular lenses	8
Experimental study comparing 2 different phacoemulsification systems with intraocular pressure control during steady-state flow and occlusion break surge events	8
Comparing outcomes of Tel-Aviv Protocol vs Athens Protocol in the treatment of progressive keratoconus	8
Comment on: Intraocular lens power calculation with ray tracing based on AS-OCT and adjusted axial length after myopic excimer laser surgery	8
COVID-19 pandemic and surgical training: cataract surgery in the Veterans Health Administration	8
Correlation between Placido-disc and rotating Scheimpflug keratometric findings before and after corneal crosslinking in children with keratoconus	8
Comparison between FLACS and Nd:YAG laser in preventing the Argentinian flag sign in intumescent white cataracts	8
Simultaneous pterygium and cataract removal with light adjustable lens implantation	8
New evidence for effectiveness of intracameral moxifloxacin for postcataract surgery endophthalmitis prophylaxis	8
Risk factors for occurrence of reverse pupillary block after intraocular lens fixation surgery	8
Comparison of pain perception in immediate vs delayed sequential bilateral cataract surgery	7
Effectiveness and safety of a thermo-mechanical action device versus thermal pulsation device in the treatment of meibomian gland dysfunction	7
Investigating the effect of different riboflavin concentrations on corneal biomechanical properties in crosslinking	7
Standards for analyzing astigmatic outcomes: Part I: astigmatism basics	7
Corneal opacities after small-incision lenticule extraction	7
Reply: Long-term efficacy and safety profiles of iris-fixated foldable anterior chamber phakic intraocular lens implantation in eyes with more than 10-years of follow-up	7
Cataract and diabetes: review of the literature	7
Spherical equivalent prediction analysis in intraocular lens power calculations using Eyetemis: a comprehensive approach	7
Comment on: Phacoemulsification in patients with corneal opacities using slit illumination of the surgical microscope	7
Size exchange and vault response in posterior chamber phakic intraocular lens implantation: 12 years at a high-volume center	7
Digital 3D heads-up LASIK surgery: feasibility, surgical duration, complication rates, and comparison with a conventional microscope	7
How to reduce free radicals during phacoemulsification: electron paramagnetic resonance measurements comparing the production of free radicals in different use cases	7
Pearls for the young cataract surgeon: the white cataract	7
Accuracy and refractive adjustment of IOL calculation formulas for primary IOL fixation using the Yamane technique	7
Impact of prior pars plana vitrectomy on development of cystoid macular edema after uneventful cataract surgery	7
Reply: Incidence and factors for pseudoaccommodation after monofocal lens implantation: the Monofocal Extended Range of Vision study	7
Visual outcomes, satisfaction, and spectacle independence with a nondiffractive extended vision intraocular lens targeted for slight monovision	7
Reply: Late-onset toxic anterior segment syndrome after possible aluminum-contaminated and silicon-contaminated intraocular lens implantation	7
Reply: Efficacy of segmented axial length and artificial intelligence approaches to intraocular lens power calculation in short eyes	7
Light-adjustable lens in eyes with a history of radial keratotomy	7
Ptosis effects on intraocular lens power calculation	7
Intraocular lens power calculation in myopic eyes undergoing bilensectomy: analysis of comparability and accuracy	7
Quantification of physiological tilt of the phakic eye using biometry parameters and AS-OCT	7
Transconjunctival sutureless intrascleral fixation of 3-piece intraocular lenses using a curved needle	7
Evaluating the safety and operability of asymmetric trapezoid and near-square side-port incision in cataract surgery	7
Costs associated with in-home postoperative eyedrop nursing care in Belgium: implications for a switch to dropless cataract surgery	7
Biometric description of 34 589 eyes undergoing cataract surgery: sex differences	7
Comment on: Eyelid margin disease (blepharitis and meibomian gland dysfunction): clinical review of evidence-based and emerging treatments	7
Incidence of Fluorescein Angiography–Proven Cystoid Macular Edema Following Four-Point Gore-Tex Scleral Fixation of the Akreos AO60 Introcular Lens	7
Bridging discovery and practice: why translational research matters in advancing refractive surgery	6
Clinical Outcomes and In Vivo Wavefront Analysis of a Toric Transcleral Plug-Fixated IOL Using a Pyramidal Sensor Aberrometer	6
Intracorneal knot or flange depot fixation: new transscleral technique for intraocular lens fixation	6
Phakic intraocular lens explantation: series of 175 surgeries	6
Corneal diameter measurements by 3 optical biometers and their effect on phakic intraocular lens sizing	6
Intraocular lens power calculation adapted to sutureless scleral fixation with the Yamane technique	6
Comparison of postocclusion surge between venturi and peristaltic phacoemulsification pump type	6
Refractive outcomes after secondary scleral-sutured toric intraocular lenses for the correction of corneal astigmatism	6
Intracameral phenylephrine for surgical mydriasis and intraoperative floppy-iris syndrome: systemic adverse effects and optimal dose	6
Erratum to: Clinical and laboratory studies on the effects of capsular tension ring on surgical outcomes of trifocal intraocular lens implantation	6
Multimodal deep learning for predicting postoperative vault and selecting implantable collamer lens sizes using AS-OCT and ultrasound biomicroscopy images	6
Comment on: Experimental study comparing 2 different phacoemulsification systems with intraocular pressure control during steady-state flow and occlusion break surge events	6
Standard vs total keratometry for intraocular lens power calculation in cataract surgery combined with DMEK	6
Fish-tail sign: posterior capsular defect tracing the path of an intraocular foreign body	6
Early outcomes of second-generation light-adjustable lenses in eyes with and without corneal refractive surgery	6
Prediction of postoperative effective lens position using iris root depth in primary angle-closure diseases	6
Preliminary demonstration of a novel intraocular lens power calculation: the O formula	6