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Phlyctenulosis vs marginal keratitis

Is It an Ulcer or an Infiltrate

  1. Marginal keratitis. CLPUs can be distinguished from marginal keratitis and phlyctenulosis, even though they all involve Staphylococcal antigen hypersensitivity. Marginal catarrhal sterile ulcers or marginal keratitis are observed in patients with chronic Staphylococcal lid disease. These are typically middle-aged, non-contact lens wearers who.
  2. Phlyctenular keratoconjunctivitis is a nodular inflammation of the cornea or conjunctiva that results from a hypersensitivity reaction to a foreign antigen. Prior to the 1950s, phlyctenular keratoconjunctivitis often presented as a consequence of a hypersensitivity reaction to tuberculin protein due to high prevalence of tuberculosis
  3. Staphylococcal marginal keratitis is a hypersensitivity reaction to Staphylococcus antigens and is associated with chronic blepharitis. Focal, noninfectious subepithelial infiltrates occur, as a result of the host's antibody response, on the peripheral cornea but are separated from the limbus by a peripheral clear zone. phlyctenulosis.
  4. Staphylococcal Marginal Keratitis/Ulcer. Peripheral curvilinear infiltrates in superficial cornea often where the lids cross the corneal periphery associated with loss of corneal epithelium; ulcerations in the marginal zone separated from the limbus by a clear corneal zone. Often associated with blepharitis. Mooren Ulcer
  5. Marginal ulcers: Marginal ulcers may occur in which phlyctenulosis starts at the limbus and progresses to the cornea without leaving behind a clear space between the limbus and ulcer. Diffuse central pattern: A diffuse central pattern without ulceration often occurs in recurrent disease. This may lead to an in-growth of superficial or deep vessels

Phlyctenular Keratoconjunctivitis - EyeWik

Marginal keratitis is an inflammatory disease of the peripheral cornea, characterized by peripheral stromal infiltrates which are often associated with epithelium break down and ulceration. It is usually associated with the presence of blepharoconjunctivitis and is thought to represent an inflammatory response against S. aureus antigens Keratitis (marginal) The CMGs are guidelines on the diagnosis and management of a range of common and rare, but important, eye conditions that present with varying frequency in primary and first contact care

Phlyctenulosis. Phlyctenular keratoconjunctivitis is an immune-mediated condition in which the cornea becomes sensitized to a microbial antigen during a delayed hypersensitivity reaction. With repeated exposure to this antigen, phlyctenules can develop on the corneal or conjunctival side of the limbus. Staph marginal keratitis Phlyctenulosis. Phlyctenular keratoconjunctivitis is a nodular inflammation of the cornea or conjunctiva that arises from a hypersensitivity response to a foreign antigen. Prior to the 1950s, phlyctenular keratoconjunctivitis provided as a consequence of a hypersensitivity reaction to tuberculin protein due to the high occurrence of tuberculosis

Marginal keratitis vs microbial keratitis. Marginal keratitis is a clinical diagnosis; therefore no investigations are recommended. If microbial keratitis suspected, investigation and treatment should be carried out per RVEEH Microbial Keratitis Clinical Practice Guidelines (CPG) Second, not all keratitis visits were for microbial keratitis; some keratitis does not result from infection Salzmann's nodular degeneration SND is a slowly progressive condition in which gray-white to bluish nodules measuring 1-3 mm are seen anterior to Bowman's layer of the cornea, usually bilaterally[1],[2],[3]. These elevated nodules can be located near the limbus or in the mid-peripheral cornea[4]

Pterygium, from the Greek pterygos meaning wing, is a common ocular surface lesion originating in the limbal conjunctiva within the palpebral fissure with progressive involvement of the cornea. The lesion occurs more frequently at the nasal limbus than the temporal with a characteristic wing-like appearance Phlyctenular Keratoconjunctivitis. Inflammation of the conjunctiva and cornea induced by microbial antigens. Causative organisms include: Staphylococcus aureus, Mycobacterium tuberculosis, Chlamydia sp. Candida albicans and parasites (Ascaris lumbricoides, Ancylostoma duodenale) Marginal keratitis is a type ____ hypersensitivity reaction. III; NOT a direct bacterial infection, but a reaction against staph exotoxins. Phlyctenulosis is a type ___ hypersensitivity reaction. IV (delayed); reaction to staph antigens. Contraindication of herpes simplex epithelial keratitis Marginal corneal ulcer is characterized by the appearance of small, gray-white circumlimbal lesions. These infiltrative lesions are separated from the limbus by about 1 mm of clear cornea and they may have overlying epithelial defects. The non-infectious marginal keratitis is an immune system response to corneal damage 'peripheral ulcerative keratitis' is a shallow ulcer on the surface of the cornea, on the edge of the cornea. The eye is red just near the ulcer. The ulcer appears green when the doctor or nurse places a fluorescent dye drop in the eye

Treatment. Treat infection with antibiotic. Ask if allergic to Chloramphenicol. If not, supply Chloramphenicol 1% eye ointment 3 times daily for a week. If allergic to Chloramphenicol, or pregnant, supply Fucidic acid 1% liquid gel twice a day for a week. If no suspicion of herpes simplex keratitis, treat inflammation with The complete remission rate is in excess of 90 percent for MALT lymphoma, with excellent long-term local control in the majority of patients. Potential complications of EBRT include xerophthalmia, keratitis, cataract formation, and retinopathy. 6. Interferon alfa-2b is a glycoprotein produced by leukocytes and has both antiviral and antitumor. Start studying Anterior Segment 9.2.3 (Bacterial Keratitis to Phlyctenulosis). Learn vocabulary, terms, and more with flashcards, games, and other study tools

Marginal keratitis 2. Phlyctenulosis 3. Ocular Rosacea LOCAL CAUSES 19. I. Blepharitis Associated Keratitis ABSENT PRESENT Less than 2 clock hours of the peripheral cornea Less ulcerative tendency Does not progress centrally LOCAL CAUSES 20. Signs of blepharitis ABSENT MILDLY PRESENT crustiness, collarettes, flaking telangiectasia of eyelids. Anterior blepharitis (also known as Anterior Lid Margin Disease) caused by (1) direct infection, (2) reaction to staphylococcal exotoxin or (3) allergic response to staphylococcal antigen. Posterior blepharitis (also known as Posterior Lid Margin Disease) meibomian secretion becomes abnormal both chemically and physically These conditions include non-inflammatory conditions (eg, Terrien's marginal degeneration, pellucid marginal degeneration, and senile furrows) as well as others associated with inflammation or infection (eg, staphylococcal marginal keratitis, phlyctenulosis, vernal keratoconjunctivitis)

Catarrhal marginal ulcers. Hypersensitivity to staphylococcal antigens can cause peripheral corneal ulcers known as catarrhal marginal ulcers.37, 69, 91, 102 Phlyctenulosis is a kind of hypersensitivity reaction to systemic antigens. Corneal phlyctenules are typically seen at the limbus 2. Inflamatory keratitis (immune related) • Marginal keratitis, Phlyctenulosis , Rosacea (staph hypersensitivity) • Peripheral ulcerative keratitis (PUK). • Mooren ulcer • Ulcer or not (edges). • Site. • Clear zone from limbus. • Sclera involved or not. • Interstitial keratitis. 51. Marinal keratitis Hypersensitivity to staph. Phlyctenulosis can also accompany this condition as a type IV hypersensitivity reaction to microbial antigens. Chronic staphylococcal blepharitis can involve the cornea with a superficial coarse epitheliopathy and punctate corneal erosions. More serious corneal involvement, such as acute marginal infiltration and ulceration, is less common

marginal keratitis; phlyctenulosis; neovascularisation and pannus; mild papillary conjunctivitis Anterior marginal blepharitis (seborrhoeic) Lid margin hyperaemia Oily or greasy deposits on lid margins Conjunctival hyperaemia. In phlyctenulosis corneal involvement results in the classical symptom of extreme photophobia. Mooren's ulcer patient complained of photophobia, tearing, redness but pain was typically the outstanding features. Marginal keratitis associated with Blepharoconjunctivitis had the commonest bilateral presentation in this study. PUK associated with. Marginal keratitis often occurs due to staphylococcal infections, and the infiltrates show a clear space from the limbus. Peripheral corneal degenerations are noninflammatory, lack infiltrates, and have intact corneal epithelium. 4.4. Etiological diagnosis. Symptoms and signs pointing towards a systemic diagnosis help in management

The Infection That Wouldn't Quit - American Academy of

  1. Salzmann's nodular degeneration is a rare, noninflammatory, slowly progressive, degenerative condition. Bluish-white nodules raised above the surface of the cornea characterize it. It has usually developed in corneas with a history of phlyctenulosis, trachoma, vernal keratoconjunctivitis, measles, s
  2. In children the diagnosis of healed phlyctenulosis can be made with a high degree of accuracy because of the absence usually of confusing clinical pictures such as those produced by acne rosacea keratitis, recurrent staphylococcic marginal ulcers, recurrent herpes corneae, and so forth. 3
  3. Microbial keratitis is infection of the cornea that can be caused by a range of non-viral pathogens. The causative organisms include bacteria, protists (e.g. acanthamoeba), and fungi (yeasts, moulds and microsporidia). It is characterised by an acute or sub-acute onset of pain, conjunctival injection

Corneal Marginal Ulcer: Marginal keratitis with ulceration

secondary changes include stye formation , marginal keratitis and occasionally phlyctenulosis (Corneal nodulesthat developed near the limbus and then spread onto the cornea, carrying behind them a leash of vessels) . associated with tear film instability and dry eye . Cont. Signs of Staphylococcal blephariti - late sequella to keratitis, e.g. phlyctenulosis, I.K., trachoma - focal replacement of Bowman's with hyaline tissue - remove with superficial keratectomy Coat's Ring - small white ring in superficial corneal stroma after metallic foreign body, contains iron Lipid Keratopathy - yellow-white infiltrate with feathery edges i

Phlyctenular Keratoconjunctivitis National Health Portal

Marginal Keratitis - EyeWik

  1. Weak topical steroids Such as flurometholone 0.1 % QID for 1 week is usful for patients with sever papillary conjunctivitis , marginal keratitis and phlyctenulosis . 4. Tear substitutes Required for associted tear film instability and dryness Posterior blepharitis, the more common condition, is characterized by inflammation of the inner portion.
  2. al bulbs), geographic ulcer (scalloped borders), or marginal ulcer (dilated limbal vessels, no clear zone at limbus [vs Staph marginal ulcer that has clear zone]); associated with scarring and decreased corneal sensation (neurotrophic cornea)
  3. Inhoudsopgave hoornvliesontsteking Het hoornvlies (cornea) Hoornvliesontsteking (keratitis) Klachten Oorzaken en behandeling van een ontsteking bacteriën, virussen, schimmels, gisten chemicaliën (etsing) ultraviolette straling ('lasogen', 'sneeuwblind') trauma / ongeval ooglidafwijkingen (o.a. randkeratitis, exposure keratopathie) stoornis gevoelszenuw: neurotrofe keratitis.

PHLYCTENULOSIS STAPHYLOCOCCAL HYPERSENSITIVITY CONTACT LENS-ASSOCIATED INFILTRATES 54. Graft vs host disease 55. - Acne rosacea -Mooren s ulcer -Traumatic ,post surgical -Exposure keratopathy -Terrien's Marginal degeneration - Staphylococcal -Viral - Herpes -Acanthamoeba -Leibowitz 2nd edi pp568 56 Atopic, Vernal, Infiltrative, Immunological keratitis, Marginal Keratitis (marginal ulcer is a misnomer), Staph Toxic SPK, Medicamentosa, Non-syphilitic interstitial keratitis (Cogan syndrome), Contac lenses related: Phlyctenulosis: Term. Work-Up/Approach for Phlyctenulosis: Definition

Keratitis (marginal) - College of Optometrist

  1. Ambrósio R Jr, Periman LM, Netto MV, Wilson SE (2003) Bilateral marginal sterile infiltrates and diffuse lamellar keratitis after laser in situ keratomileusis. J Refract Surg 19:154-158 PubMed Google Schola
  2. Cont. Signs of Staphylococcal blepharitis • secondary changes include stye formation , marginal keratitis and occasionally phlyctenulosis (Corneal nodulesthat developed near the limbus and then spread onto the cornea, carrying behind them a leash of vessels) . • associated with tear film instability and dry eye
  3. Sympathetic ophthalmia and Vogt-KoyanagiHarada syndrome, corneal graft rejection, phlyctenulosis, and contact allergy are all type IV reactions. There is an association between vernal and keratoconus. 58 Pellucid marginal herpes simplex keratitis can sometimes mimic the picture of staphylococcal marginal keratitis. It is wise to check.
  4. Signs and Symptoms. Atopy is a genetic predisposition to develop an allergic reaction. 1 Systemic examples include allergic rhinitis and atopic dermatitis. The ocular correlate is atopic conjunctivitis. Patients with atopic keratoconjunctivitis (AKC) invariably have a personal or family history of allergic disease. 2 This may include atopic dermatitis, asthma, hayfever, food allergies and/or.
  5. ed and treated for recurrent corneal epithelial erosion and who presented again with signs suggestive of a microbial keratitis

antimicrobial keratitis. Cutaneous sebaceous gland dysfunction of the face, neck and vit hem. More common in fair skinned. Clinical Presentation. Excessive sebum secretions with chronic blepharitis. Eyelid margin telangiectasia; MG distortion- chalazia. Ocular surface involvement- conjunctivitis, marginal corneal infiltrates Phlyctenulosis. Marginal keratitis. Bacterial keratitis. Fungal keratitis. Acanthamoeba keratitis. Herpes simplex keratitis. Herpes zoster ophthalmicus (ophthalmic shingles) Thygeson's keratitis. Corneal dystrophies. Pterygium. Band keratopathy. Corneal degenerations and deposits. Corneal graft rejection Academia.edu is a platform for academics to share research papers bowmans. what type of collagen is sclera. type I (mneumonic, the L in sclera is 1) what type of collagen is associated with stromal wound healing. type III. what type of collagen is associated with basement membrane. type 4 (mneumonic; four is the floor) what is the most common risk factor for fungal keratitis corneal epithelial erosion. Recurrent corneal erosion (RCE) can develop after mechanical injury, as a complication of chronic ocular surface disease, or as a result of inherited dystrophies of the epithelial basement membrane or stroma. 1-7 Characteristically, there is a history of recurrent pain on waking, with lacrimation and photophobia

Corneoscleral Concerns: Trouble at the Borde

Dis- deposition in the peripheral cornea. This disease fPERIPHERAL CORNEAL DISORDERS results from a deficiency of homogentisic acid oxi- syndrome) may result in cornea1 stromal opacifica- dase, resulting in elevated serum and tissue levels of tion.305 Although, in most cases, these diffusely in- homogentisic acid HODS A retrospective study of keratoconic subjects examined between 2013 and 2018 was conducted. Subjects were included regardless of age, sex, pre-existing morbidity, or scleral lens design. Only eyes fit successfully with scleral contact lenses for ≥1 year were included. Exclusion criteria were prior corneal surgery, dystrophy, degeneration, and trauma. RESULTS A total of 157 eyes of 86. Common Causes of. Red Eye Case ED 57/F CC: left eye redness 1 day prior, noted sudden onset redness of the left eye with no associated pain, tearing, and blurring of vision. No history of trauma. On the day of consult, redness persisted and now with associated heaviness prompting consult at the ER Referred to ophtha for red eye Red Eye Cardinal sign of ocular inflammation Caused by.

The rate of ocular disease appears to vary widely in different populations. The rate of seropositivity for toxoplasmosis is estimated to be from 3% to as high as 70% of adults in the United States; this varies for different locales and age groups, [6] whereas the prevalence of ocular toxoplasmosis is less than 1% 24. Stein RM, Clinch TE, Cohen EJ, et al. Infected vs sterile corneal infiltrates in contact lens wearers. Am J Ophthalmol. 1988;105:632-636. 25. McLeod SD, Kolahdouz-Isfahani A, Rostamian K, et al. The role of smears, cultures, and antibiotic sensitivity testing in the management of suspected infectious keratitis. Ophthalmology. 1996;103:23. Quibron-t Buy cheap quibron-t 400mg on-lin

Phlyctenulosis: Causes and Treatment EYExan

Marginal keratitis with rosacea

Compositions and methods comprising protein activated receptor antagonists are provided More particularly, the present invention relates to the use of proteins, peptides and biomolecules that bind to protein activated receptor 2, and inhibit the processes associated with the activation of that receptor.More specifically, the present invention provides novel compositions and methods for the. Taken as a 1 gram dose, by mouth, one time, it has been documented as being as effective for the treatment of genital chlamydial infection as doxycycline. Topical therapy is adjunctive and includes erythromicin, tetracycline or sulfacetamide t.i.d. for three weeks as well. Patients with gonococcal conjunctivitis require immediate conjunctival. 21. GVHD的主要表現之一是keratitis sicca, 也可能有cicatrical lagophthalmos. => GVHD常發生在BMT之後 => active nonocular GVHD與ocular surface diseae有關 22. interstitial keratitis(IK)雖然多由congenital syphilis造成,但HZV,HSV, C. trachomatis也是原因之一

Video: Marginal keratitis vs microbial keratitis marginal

Salzmann Nodular Degeneration - EyeWik

Total PVD at Day 28 was achieved in 13.4% of ocriplasmin-treated eyes vs. 3.7% placebo Nonsurgical closure of macular holes was achieved in 40.6% of ocriplasmininjected eyes vs. 10.6% placebo FTMH width 400 m: closure at Month 6 (48.8% ocriplasmin vs. 18.2% placebo) 81 Ophthalmology Explorer o FTMH width > 400 m: 0% for both groups. Dhaval Patel M Since the first edition that was published in 1998 we have seen manychanges in ophthalmology from advancements in laser..

Patient assessment | ICNSWMK: A Stealthy OpponentMarginal keratitis - Meduweb

Pterygium - EyeWik

Compositions and methods comprising protein activated receptor antagonists are provided More particularly, the present invention relates to the use of proteins, peptides and biomolecules that bind to protein activated receptor 2, and inhibit the processes associated with the activation of that receptor The present invention relates to compounds, compositions, and methods for the study, diagnosis, and treatment of traits, diseases and conditions that respond to the modulation of gene expression and/or activity, and/or modulate a gene expression pathway. Specifically, the invention relates to double-stranded nucleic acid molecules including small nucleic acid molecules, such as short. The invention relates to antibodies against S100A4, methods for the preparation of these antibodies, pharmaceutical compositions comprising these antibodies, and therapeutic and diagnostic uses thereof Transcript. 1 Infectious Diseases in Critical Care Medicine . 2 INFECTIOUS DISEASE AND THERAPY Series Editor Burke A. Cunha Winthrop-University Hospital Mineola, New York and State University of New York School of Medicine Stony Brook, New York 1. Parasitic Infections in the Compromised Host, edited by Peter D. Walter and Robert M. Genta 2 Sr.no Authors Title Year Volume Issue Link; 1: Panchbhai A., Bhowate R. MRI evaluation of involvement of parotid and submandibular glands by tongue squamous cell carcinom

Phlyctenular Keratoconjunctivitis Columbia Ophthalmolog

Effectively manage even the most challenging contact lens complications with help from Contact Lens Complications, 3rd Edition! Award-winning author, clinician, and researcher Professor Nathan Efron presents a thoroughly up-to-date, clinician-friendly guide to identifying, understanding, and managing ocular response to contact lens wear 1-VA loss. 2-optic atrophy. 3-optociliary shunt vessels (connect choriod with retina) Dermoid Cysts. Normal tissue in abnormal location. (definition of choristoma) -GOLDENHAR's syndrome (ocular dermoid, skin tag, vertebral dysplasia) optic nerve glioma 플릭텐(phlycten), 플릭텐각막염, 플릭텐결막염, 플릭텐 각결막염 (phlyctenulosis, phlyctenular keratitis, phlyctenular conjunctivitis, PKC) 포도알균 가장자리 각막염(Staphylococcal marginal keratitis), 카타르성 궤양(Catarrhal ulcer, Staphylococcus hypersensitivity Of the approximately 33 million contact lens wearers in the United States, each year 6% experience a contact lens-related problem [1-3]. Contact lens wear causes significant physiologic changes in corneal metabolism, corneal epithelium and endothelium, tear composition and turnover, and oxygen and carbon dioxide levels within the cornea [4]. These changes can lead to many different.

Disease final exam review Flashcards Quizle

Case Presentation of Recurrent Peripheral Infiltrative Keratitis (PIK) of Unknown Cause 4/17/13 Northeastern State Universit A pesar de que la blefaroqueratoconjuntivitis estafilocócica es una enfermedad frecuente en la edad pediátrica, en la mayoría de los casos es subdiagnosticada. Se requiere de un tratamiento adecuado y oportuno para prevenir repercusiones visuales serias tutup, trichiasis (bulu mata salah arah), madarosis (kehilangan bulu mata) atau poliosis (kehilangan pigmentasi bulu mata) pada kasus yang sudah berlangsung lama perubahan sekunder termasuk pembentukan tembel, keratitis marginal dan kadang-kadang phlyctenulosis (nodul kornea yang berkembang di dekat limbus dan kemudian menyebar ke kornea.

Corneal ulcer and marginal corneal ulcer causes, symptoms

Pellucid marginal corneal degeneration, (Clinical Volume 4, Chapter 16) Peripheral ulcerative keratitis, sterile, associated with collagen vascular disease, (Clinical Volume 4, Chapter 2) Phlyctenulosis, (Foundations Volume 2, Chapter 49) (Foundations Volume 2,. Other peripheral corneal diseases Marginal keratitis This is a common inflammatory reaction due to hypersensitivity to staphylococcal exotoxin. It is often seen in patients with atopy, rosacea, or chronic blepharitis. Clinical features • Pain, FB sensation, redness (may be sectoral or adjacent to lid margins), photophobia, tearing, dVA Marginal arcade is 2 mm from the margin, and peripheral arcade in upper eyelid is 1 mm above the tarsus; both covered by levator (should not see during a blepharoplasty). Supratrochlear: above trochlea through septum, supplying skin of forehead and scalp Dorsal nasal: terminal branch of ophthalmic artery; lies within upper medial fat pad. Pediatric Ophthalmology And Strabismus - David Taylor [8lyrg188de0d]. Download & View Pediatric Ophthalmology And Strabismus - David Taylor as PDF for free Albert: Albert & Jakobiec's Principles & Practice of Ophthalmology THIRD EDITION Daniel M. Albert, MD MS Chair Emeritus, F. A. Davis Professor and Lorenz F. Zimmerman Professor, Department of Ophthalmology and Visual Sciences, Retina Research Foundation Emmett A. Humble Distinguished Director, of the Alice R. McPherson, MD, Eye Research Institute, University of Wisconsin Medical School.

Peripheral Ulcerative Keratitis / Marginal Corneal Ulcer

Toxic Keratitis: this pertains to microtrauma to the corneal surface epithelium secondary to contact to chemicals (such as alcohol based products like hair spray) or topical medications (active ingredient, preservatives or both). Presence of these superficial punctate lesions make the surface irregular and will thus affect vision. Abnormalities. by Ron Melton, O.D., and Randall Thomas, O.D. Sponsored by June 15, 2007 A Supplement to Dear friends and colleagues, Can you believe that optometrists write as many prescription Biblioteca en línea. Materiales de aprendizaje gratuitos It has usually developed in corneas with a history of phlyctenulosis, trachoma, vernal keratoconjunctivitis, measles, scarlet fever, and various other viral diseases. However, today the majority of cases have been seen without recognized previous keratitis. It is composed of dense irregularly arranged collagen tissue with hyalinization between. An icon used to represent a menu that can be toggled by interacting with this icon

Cornea EYE Hospital

Keratitis, Marginal Community Eye Care Guideline

This banner text can have markup.. web; books; video; audio; software; images; Toggle navigatio Offering current diagnostic and therapeutic guidance to manage ocular disorders, The Massachusetts Eye and Ear Infirmary.. Issuu is a digital publishing platform that makes it simple to publish magazines, catalogs, newspapers, books, and more online. Easily share your publications and get them in front of Issuu's. Fifteen age-matched non-IgE-S control children underwent the same determinations. s-ECP, PBECs and s-total IgE were significantly higher in IgE-S than in non-IgE-S VKC patients and in non-IgE-S VKC patients than in controls. A lower prevalence of IgE-S patients was found in bulbar vs. tarsal (P = 0. 050) or mixed forms (P = 0.002) bacterial keratitis細菌性角膜炎4-2-2. basal cell carcinoma of eyelid眼瞼基底細胞癌16-1-2. Behcet's diseaseBehcet病9-2-6;18-5-2. bichrom test雙色法13-6. binocular vision雙眼視覺14-1-4. blepharitis瞼緣炎1-2-3. blinding glare盲眩耀13-1-2. blood-aqueous barrier血—房水屏障8-2-2

Peripheral Corneal Disorders Flashcards | Quizlet