Refractive Surgery Flashcards
What is Prolate shape?
shape of the cornea where curvature is steepest at the center and flattens out. Nasal is more flat than temporal
what is placido based corneal topography?
measures anterior corneal radius of curvature and ESTIMATE total K power
How much of the total refractive power of the eye comes from the cornea?
2/3. Anterior K is very + power; posterior K is negative in power thereby reducing total K refractive power
what are wavefront aberrations?
measuring small aberrations on the cornea by shining light on to retina and then measuring the reflected waves and using small lenses to neutralize the aberrations.
what’s the most used wavefront sensor called?
Hartmann-Shack
What are Zernike polynomials? what are they expressed as?
mathematical formulas used to describe cornea aberrations on wavefront–expressed as root mean square error “RMS”
what are the three most important Zernike coefficients affecting visual quality?
spherical aberration, coma, trefoil.
What is Fourier analysis?
an alternative method of interpreting aberrometer results than Zernike. Fourier is more detailed
What are lower order aberrations?
Lower order are things like myopia (positive defocus), hyperopia (negative defocus), regular astigmatism (orthogonal and oblique defocus)
What are higher order aberrations?
more complex aberrations that dependent on pupil size.. increases as pupil dilates.
may increase after surface ablation
impact of surface ablation/LASIK on spherical aberration?
increases spherical aberration leading to pronounced halos. increases depth of field but decreases contrast sensitivity
what are the three types of OCT domains?
frequency, time, spectral
what are the two types of dry eyes?
aqueous tear deficiency, evaporative dry eyes
how do giant papillae form?
weakening of inter papillary septa over time
what is at the center of follicles?
germinal centers
what is benign lymphoid folliculosis?
normal follicles on inferior palpebral conj or in the fornix in young people
make up of KPs
fibrin/proteins, neutrophils, lymphocytes, macrophages (mutton fat clumps)
two types of stromal keratitis and causes?
suppurative vs nonsuppurative
suppurative: bacterial, fungal, acanthomoeba
nonsuppurative: rheumatoid, cogan’s, syphilis, lyme, TB, leprosy
whats the pathophys of evaporative dry eyes
MGD where unsaturated fats becomes saturated and obstructs the gland and leads to tear film instability
whats the pathophys of aqueous tear deficiency?
T cell mediated inflammation/destruction of lacrimal gland leading to decreased tear production and increased epithelial apoptosis
how wide is the normal tear meniscus
1 mm and convex
mucus discharge is frequent in which kind of dry eye
aqueous tear deficiency
when is Aqueous tear deficiency considered secondary to sjogrens
if theres hypergammaglobulinemia, collagen vascular disease, SSaSSb positive
what is primary and secondary sjogre;s syndrome
primary has ill defined systemic disease process. secondary has well defined systemic disease process such as a rheumatoid condition
which dry eye is worse in the morning and which is worse in the evening?
evaporative is worse in AM
ATD is worse in PM
Categorization of MGD?
hypo vs hyper delivery. Hypodelivery then is hypo secretion vs obstruction. hypo secretion is due to cicatricial vs non cicatricial
risk factors of dry eyes?
xerophthalmia, allergies, contact lens wear, high n6/n3 fatty acid ratio, DM, smoking, prolonged video, meds (especially glaucoma drops with benzalkonium chloride)
MGD is often associated with what skin condition?
rosacea acne
whats the mainstay of ATD treatment?
replacement therapy: ATs, gels, ointments, restates, xiidra, scleral contacts, autologous serum, moist chambers
How to treat filamentous keratitis?
debride the filaments, supplement tears, punctal plugs, acetylcysteine 10% for mucolytic, low dose steroid/cyclosporin
what are demulcents
mucomemetics in Its
How long does restasis take to work. How long does xiidra?
restates is many months of consistent use. xiidra within a few weeks
side effects of xiidra
irritation, transient blurry vision, dysgusia, should not insert CL for 15 mins
what are the two cholinergic meds used for increasing tears and decreasing xerostomia?
pilocarpine, cevimeline
also can do omega fats to help
what are some surgical options for ATD?
punctal plugs/cautery, lid/conj chalasis surgery, lateral/medial tarrsorrhaphy
mainstay of MGD treatment?
eyelid hygiene–warm compress, lid massage, lid scrub,
what are some adjuncts for MGD treatment aside from hygiene
short term azithromycin drop use to decrease bacteria burden, omega fats, PO tetracycline/doxy/minocycline (control disease but not eliminate), LipiFlow
rosacea is associate with what organism. what’s the theory of pathogenesis
demodex–> increased canthelicidin –>inflammation–>dysfunction of sebaceous gland
what are things that can exacerbate rosacea
alcohol, emotional stress, spicy foods, hot/cold environment
features of ocular rosacea
recalcitrant chronic blepharitis, chalazion, excessive oil production, chronic conjunctivitis, stromal keratitis, sterile ulcers, episcleritis/iritis, corneal NV
facial lesions associated with rosacea
mid facial erythema, telangiectasis, flushing episodes, malarkey rash, rhinopehyma
mainstay of treating ocular rosacea?
PO tetracyclines (erythropoietin/azithro can be used if tetracyclines are contraindicated)
topical: metrogel and azelaic acid
Intense pulsed light therapy
management of ulcerative keratitis in rosacea?
conservative is better due to poor prognosis. Can be infectious or noninfectious–can use steroids if determined to not be infectious.
what is seborrheic blepharitis?
inflammation at the lid margin with scaling, scurf with greasy consistency, PEEs, evaporative dry eyes
treatment for seborrheic blepharitis?
lid hygiene, selenium sulfide shampoo
demodicosis is associated with what exam finding?
lash sleeving with refractory blepharitis
how to treat democicosis?
tea tree oil, oral ivermectin
staph blepharitis is seen in what population
young people.
clinical finding of staph blepharitis?
collarettes, hard brittle fibrinous scales, and hard crusts matted around cilia, macaronis, poliosis, trichiasis
what are two organisms commonly causing chronic blepharoconjunctivitis?
staph aureus and mortadella cunata.
chronic angular blepharoconjunctivitis is caused by what organism
moraxella cunata
staph marginal disease is usually at what clock hours?
2, 4, 8, 10
what two organisms cause phyctenules?
staph aureus, TB
hordeolum vs chalazion
hordeolum: inflammation of Zeiss or meibomian
chalazion: lipogranulomatous nodule of Zeiss or meibomian.
hair loss over chronic chalazion is indicative of what?
malignancy–basal, squam, or sebaceous cA.
intralesional injection of steroids can be done for chalazion… who should you not do it on.
dark skinned individual –can lighten skin in the lesion area.
