Hom ntawm qhov muag astigmatism: nta, kuaj mob, kho thiab kho

Cov txheej txheem:

Hom ntawm qhov muag astigmatism: nta, kuaj mob, kho thiab kho
Hom ntawm qhov muag astigmatism: nta, kuaj mob, kho thiab kho

Video: Hom ntawm qhov muag astigmatism: nta, kuaj mob, kho thiab kho

Video: Hom ntawm qhov muag astigmatism: nta, kuaj mob, kho thiab kho
Video: Hnub no mus thauj puv luj nawb 2024, Kaum ib hlis
Anonim

Dab tsi yog hom astigmatism? Yuav kuaj tus kab mob no li cas? Koj yuav pom cov lus teb rau cov lus nug no thiab lwm yam hauv kab lus. Astigmatism yog ib qho teeb meem ntawm refraction (lub teeb refraction), nyob rau hauv uas cov duab yog tsom tsis tau ntawm ib qho, tab sis ntawm ob peb lub ntsiab lus ntawm lub retina ib zaug. Qhov no yog vim qhov tsis raug ntawm lub cornea.

Ua ke nrog kev pom deb thiab pom ze, astigmatism yog hais txog ametropia. Cov no yog cov xwm txheej tshwm sim los ntawm qhov tsis raug refraction. Nws yuav tsum tau muab sau tseg tias astigmatism yog ib tug heev pathology, uas, raws li ntau yam, tshwm sim nyob rau hauv 25% ntawm tag nrho cov pejxeem. Xav txog hom, theem, tsos mob thiab kho astigmatism hauv qab no.

Qhov no yog dab tsi?

Dab tsi yog astigmatism? Nws yog ib qho tseem ceeb ntawm qhov tsis pom kev. Qhov tseeb, astigmatism yog ib qho kev hloov ntawm tus qauv refractive hwj chim ntawm pob tshab spheres ntawm lub qhov muag, nyob rau hauv uas nws tsis muaj zog (hypermetropic astigmatism) los yog ntxiv dag zog rau (myopic astigmatism), raws li zoo raws li ib tug pronounced teeb meem ntawm sphericity, yuav pom tau. Nyob rau hauv cov ntaub ntawv no, raws li ib tug txoj cai, lub refractive hwj chim nyob rau hauvqee qhov meridians muaj ntau dua li lwm tus.

Hom astigmatism yooj yim complex sib xyaw
Hom astigmatism yooj yim complex sib xyaw

Nrog qhov kev ua txhaum cai no, tus neeg tsis tuaj yeem xaiv qhov kev ncua deb ntawm qhov khoom kom pom tseeb. Qhov kev ncua deb nyob rau hauv ib qho meridian rau lub refraction ntawm lub teeb rays tej zaum yuav txaus, thiab nyob rau hauv lwm yam - tsis txaus.

Ua rau astigmatism

Tsawg tus neeg paub cov tsos mob, ua rau, cov tsos mob thiab hom astigmatism. Tus kab mob no tshwm sim vim qhov tsis raug ntawm lub cornea (qee zaum lub lens). Lo lus "astigmatism" yog txhais los ntawm Latin li "tsis muaj ib tug focal point."

Nws paub tias lub lens thiab pob txha ntawm lub qhov muag tsis zoo muaj lub ntsej muag tiaj tus. Nrog astigmatism, qhov sphericity no cuam tshuam, thiab vim li ntawd, qhov sib txawv curvature yog tsim nyob rau hauv ntau cov lus qhia. Cov meridians sib txawv ntawm qhov chaw ntawm lub pob zeb hauv lub xeev no muaj lub zog sib txawv, yog li daim duab ntawm ib yam khoom thaum lub sij hawm dhau los ntawm lub teeb rays los ntawm lub cornea yog distorted.

Kev faib tawm ntawm hom astigmatism
Kev faib tawm ntawm hom astigmatism

Qee qhov chaw ntawm daim duab tau kwv yees mus rau retina, lwm tus tom qab lossis pem hauv ntej ntawm nws. Tab sis muaj cov xwm txheej uas nyuaj dua. Yog li ntawd, ib tug neeg tsis pom ib daim duab zoo tib yam, tab sis ib qho kev hloov pauv, uas qee cov kab tau pom meej meej, thaum lwm tus yog qhov muag plooj. Cov neeg uas muaj astigmatism pom cov khoom nyob ib puag ncig lawv li cas? Siv ib tug oval teaspoon thiab saib rau hauv nws. Koj yuav pom koj qhov kev xav cuam tshuam hauv nws, thiab qhov no yog li cas cov neeg uas muaj astigmatism pom txhua yam nyob ib puag ncig.

Symptoms

Hom astigmatism peb yuav xav txogNtxiv mus, thiab tam sim no peb sau cov tsos mob ntawm tus kab mob no. Cov no suav nrog:

  1. Headache.
  2. qhov muag tsis pom kev uas tsis nyob ntawm qhov deb.
  3. Deformation ntawm cov kab ncaj.
  4. Txhob qhov muag tsis pom kev.
  5. qaug zog ntawm lub cev tsis pom kev.

Views

Tus kab mob no raug cais raws li qee yam. Raws li lawv, cov nram qab no hom ntawm astigmatism yog txawv:

  • los ntawm qhov pom - tau, congenital;
  • Yon pathology - lens, corneal;
  • by hom: nrog oblique axes - ncaj, thim rov qab;
  • raws li lub hauv paus ntawm lub zog refractive - tsis raug, raug;
  • nyob rau hauv tsos - complex, myopic, yooj yim;
  • hypermetropic - sib xyaw, yooj yim, complex.
  • Tus neeg uas muaj astigmatism pom li cas?
    Tus neeg uas muaj astigmatism pom li cas?

Nws paub tias tib neeg lub qhov muag yog ib qho qauv uas pom tsis yog qhov khoom nws tus kheej, tab sis lub teeb pom los ntawm nws qhov chaw. Cov hluav taws xob poob rau ntawm retina, los ntawm cov ntaub ntawv xa tawm ntawm cov paj hlwb mus rau lub hlwb, qhov twg daim duab kawg yog tsim. Tab sis ua ntej ntawd, lub teeb mus dhau ib qho kev ntse ntawm refraction.

Txhua qhov taw qhia ntawm cov khoom muaj kev cuam tshuam cov rays ntawm lub teeb, uas yog thawj zaug refracted nyob rau hauv lub cornea thiab nkag mus rau lub lens los ntawm ib tug dej. Tom qab ntawd, dhau ntawm lub lens, cov rays raug xa mus rau lub cev vitreous, rov ua dua, thiab tom qab ntawd lawv xaus rau ntawm retina.

Qhov kev txiav txim ntawm refraction ntawm lub teeb rays thiab cov qauv intricate ntawm lub qhov muag txiav txim siab ntau yam kev hloov pauv ntawm tus kab mob no.

Astigmatismtau thiab congenital

Pom zoo, hom astigmatism tsis yooj yim kawm. Congenital daim ntawv ntawm tus kab mob no feem ntau yog txiav txim los ntawm cov txheej txheem pathological thaum lub sij hawm tso lub cev ntawm lub zes qe menyuam nyob rau hauv thaum ntxov theem ntawm cev xeeb tub. Congenital astigmatism feem ntau yog los ntawm niam txiv. Yog vim li ntawd nws thiaj pib loj hlob thaum ntxov.

Yog niam lossis txiv raug tus kab mob no, yuav tsum tau kuaj tus menyuam kom muaj tus kabmob sai li sai tau, vim tias nws tuaj yeem ua tau.

Cov me nyuam uas tsis pom kev yog feem ntau squint, qaij lawv lub taub hau rau ib sab, dov lawv ob lub qhov muag ua ke, thiab lwm yam. Yog tias tsis kho raws sijhawm, cov kev kho zoo li no tuaj yeem ua rau muaj kev pheej hmoo ntawm strabismus. Nws tseem yuav nyob txawm tias thaum koj tshem tawm qhov laj thawj.

Txhua tus yuav tsum paub qhov kev faib tawm ntawm hom astigmatism. Congenital astigmatism yog pathological thiab physiological. Hauv qhov thib ob, qhov sib txawv ntawm qhov sib txawv ntawm lub hauv paus meridians yog tsawg. Inconspicuous astigmatism ntawm 0.5 diopters yog txuam nrog kev loj hlob ntawm lub qhov muag nyob rau hauv cov me nyuam mos, uas ua rau negligible deformation. Thiab txawm tias astigmatism ntawm 0.75-1 diopter tsis cuam tshuam rau qhov pom kev ua haujlwm ntawm qhov muag.

Yog tias qhov txawv txav txawv txav ntau dua ib lub diopter, tus mob yog pathological, nrog rau kev txo qis ntawm qhov muag pom thiab xav tau kev kho tshwj xeeb.

Congenital astigmatism ua rau tib neeg mob ntau dua li qhov muaj hnub nyoog. Tom qab tag nrho, ib tug me nyuam los ntawm thawj hnub ntawm lub neej perceives daim duabtsis raug, uas ua rau muaj kev cuam tshuam rau kev txhim kho ntawm cov cuab yeej pom kev tag nrho.

Hom astigmatism hauv cov menyuam yaus
Hom astigmatism hauv cov menyuam yaus

Tau txais astigmatism tsis cuam tshuam nrog cov txheej txheem physiological hauv lub cev thiab cov kab mob congenital, yog li nws tuaj yeem tshwm sim txhua lub hnub nyoog. Tus kab mob no hloov zuj zus nyob rau hauv kev cuam tshuam ntawm sab nraud ua rau ua rau muaj qhov tsis xws luag hauv lub lens lossis cornea. Nws tuaj yeem tshwm sim vim yog cov hauv qab no:

  1. Mob keratoconus - ib qho mob ntawm lub pob kws, vim nws dhau los ua nyias thiab siv rau ntawm cov duab conical.
  2. Kev raug mob - kev puas tsuaj rau lub qhov muag los ntawm cov khoom ntse lossis txiav, subluxation ntawm lub lens, ruptures ntawm nws ligaments.
  3. Keratitis - cov txheej txheem inflammatory hauv pob txha, uas yog tshwm sim los ntawm kev kis kab mob, kev cuam tshuam ntawm lub cev lossis kev nkag mus ntawm cov tshuaj lom neeg, ua rau muaj kev ua txhaum ntawm kev ncaj ncees ntawm lub pob txha thiab khoov nws.
  4. Kev yug me nyuam nyuaj - qhov kev quab yuam ntawm lub taub hau ntawm tus menyuam hauv plab, nyem, ua rau lub qhov muag deformation thiab orbits.
  5. Pathologies ntawm lub dentoalveolar system - xws li mob ntawm lub puab tsaig sab sauv thiab cov hniav, ua rau deformation ntawm lub orbits, xws li protrusion ntawm lub puab tsaig sab sauv rau pem hauv ntej, qhib tom, thiab hais txog.
  6. Kev kho mob ntawm lub qhov muag tuaj yeem ua rau muaj kev loj hlob ntawm induced astigmatism. Yog li, yog tias tus kws kho mob rub cov seams nruj dhau ntawm lub qhov txhab ntawm lub pob kws, nws cov duab tuaj yeem hloov pauv tau. Kev tshem tawm thaum ntxov ntawm sutures muaj cov txiaj ntsig zoo ib yam, thaum cov npoo ntawm qhov incision diverge tawm tsam keeb kwm yav dhau los ntawm kev nce siab hauv lub paj hlwb.

Peb txuas ntxiv kawm cov hom astigmatism ntxiv. pob qhov muagastigmatism (corneal) tshwm sim vim tuberosity ntawm lub cornea, nws tsis sib xws curvature. Tsis tas li ntawd, kev khoov ntawm aspherical cornea nyob rau hauv txoj kab ntsug, raws li txoj cai, muaj zog dua, thiab vim li ntawd, cov rays ntawm lub teeb yog refracted ntau tshaj li cov kab rov tav. Hom kab no tuaj yeem kis tau (tom qab raug mob thiab raug mob) los yog tau los ntawm noob neej (kwv yees).

Laser kho ntawm astigmatism
Laser kho ntawm astigmatism

Lenticular astigmatism yog qhov tsawg dua. Qhov ua rau ntawm tus kab mob no feem ntau yog los ntawm keeb kwm. Nws yog tus cwj pwm los ntawm asymmetry ntawm lub lens lossis nws qhov kev tso kawm txheeb ze rau qhov chaw anteroposterior ntawm lub qhov muag. Cov peev txheej ntawm astigmatism tau txais yog:

  • senile cataract, nyob rau hauv uas cov txheej ntawm lub lens swell;
  • kev raug mob (kev hloov ntawm lub lens, contusion ntawm lub qhov muag, uas yog nrog los ntawm huab);
  • ntshav qab zib mellitus (nce ntshav qab zib provokes cov organic hloov hauv lub lens).

rov qab thiab ncaj

Cia peb soj ntsuam cov nram qab no hom ntawm qhov muag astigmatism. Cov hom kab mob no yog txiav txim los ntawm lub zog ntawm lub teeb refraction (refraction) nyob rau hauv lub hauv paus meridians. Yog hais tias ib qho tseem ceeb refractive cia muaj ib tug ntsug meridian, qhov no yog ncaj qha astigmatism. Nrog rau hom no, cov kab ntsug tau raug ntes kom meej meej. Nrog lub hnub nyoog, ncaj qha astigmatism hloov mus rau qhov thim rov qab.

Rov qab astigmatism yog qhov ua txhaum cai uas kab rov tav meridian muaj qhov txwv tsis pub muaj peev xwm. Yog li ntawd lub npe txawv - kab rov tav astigmatism. Tus kab mob no tsis tshua muaj tshwm sim. Txij li thaum lub ntiaj teb sab nraud muaj qhov kev taw qhia ntsug, astigmatism ntawm hom rov qab ua rau tsis xis nyob, tsis yooj yim.

Muaj lwm qhov kev hloov pauv - astigmatism nrog oblique axes, thaum cov meridians nrog kev txwv thiab tsawg kawg refractive zog tsis dhau ntawm txoj kab ntsug lossis kab rov tav, tab sis raws li oblique, deb ntawm lawv.

Yuav thiab yog

Txhua tus kws kho mob tuaj yeem qhia koj txog hom, hom thiab kho astigmatism. Tab sis nws yog qhov zoo dua yog tias koj kawm cov nuances ntawm koj tus kheej. Qhov tseeb astigmatism yog tus cwj pwm los ntawm cov duab elliptical ntawm lub qhov muag. Nws tshwm sim ntau dua li lwm yam kev hloov pauv, vim nws yog qhov pib ntawm lub pob txha. Lub teeb hla lub elongated axis ntawm lub oval yuav refracted tsawg, thiab mus los ntawm ib tug luv luv meridian - ntau npaum li sai tau.

Lub sijhawm dhau mus, hauv 50% ntawm cov neeg mob, tus kabmob nce lossis txo qis. Ntxiv mus, qhov ua tau ntawm ib lossis lwm txoj kev loj hlob yog yuav luag zoo tib yam. Hauv lwm qhov xwm txheej, tus kab mob tsis hloov nws daim ntawv. Xws li kev hloov kho yog txuam nrog kev loj hlob ntawm lub cev ntawm lub zeem muag, lawv cov dej num thaum lub sij hawm loj hlob ntawm tus me nyuam.

Dab tsi yog astigmatism?
Dab tsi yog astigmatism?

Nyob rau hauv cov meridians qhia nyob rau hauv sib txawv cov lus qhia, nrog rau hom kab mob no, lub refraction ntawm lub rays tshwm sim los yog muaj zog los yog qaug zog. Tab sis lub zog ntawm refraction nyob rau hauv txhua tus ntawm lawv yog zoo tib yam raws tag nrho ntev.

Tib lub sijhawm sib txawv ntawm qhov sib txawv ntawm lub ntsiab meridians, tsis xwm yeem astigmatism yog txiav txim siab los ntawm qhov tseeb tias tib lub meridian yog qhov sib txawv ntawm qhov sib txawv.

hom kab mob no cuam tshuam rau cov uas tau raug phais, raug mob lossiskab mob qhov muag. Cov neeg no tau txo qhov pom kev pom, mob taub hau loj tshwm sim thaum pom kev ntxhov siab, cov khoom hauv nqe lus nug tau hloov pauv, bifurcated.

Hmoov tsis zoo, astigmatism tsis tu ncua, raws li nws tseem hu ua, kho tsis tau. Nyob rau hauv cov ntaub ntawv no, qhov kho qhov muag kho qhov muag tsis coj qhov xav tau ib yam. Qhov no yog qhov ua ntej thaum tus kab mob no yooj yim los tiv thaiv dua li kho.

Hyperopic thiab myopic

Ua tib zoo kawm hom thiab kho qhov muag astigmatism, thiab tom qab ntawd koj tuaj yeem tiv thaiv tus kab mob no ib txwm. Dab tsi yog myopic yooj yim astigmatism (nearsighted)? Qhov no yog ib qho mob thaum qee lub rays, tom qab dhau los ntawm cov qauv refractive ntawm lub qhov muag, tau sau rau ntawm retina, thaum lwm tus nyob rau pem hauv ntej ntawm retina (myopic tsom). Qhov kev ncua deb ntawm qhov tsom xam ntau dua, qhov ntau dua qhov kev ua txhaum cai, daim duab pom qhov muag pom ntau dua.

Nws paub tias astigmatism ntawm 1 diopter nrog lub ntsug txhim kho meridian tsis ua rau muaj kev tsis txaus siab ntawm qhov muag tsis pom. Tias yog vim li cas nws yog hom lub cev.

Myopic complex astigmatism yog ib yam mob thaum lub teeb refracted sau nyob rau hauv pem hauv ntej ntawm lub retina ntawm ntau lub ntsiab lus ntawm qhov tsis sib xws ntawm nws, uas yog, myopic teeb meem pom nyob rau hauv ob meridians ib zaug. Qhov kev puas tsuaj no tuaj yeem tshwm sim vim yog vim li cas hauv qab no:

  1. Acquired (formations ntawm lub pob txha ntawm ib qho caws pliav vim muaj mob, raug mob, phais, tsawg zaus - daim ntawv pathological ntawm lub lens).
  2. Congenital (kev hloov pauv ntawm lub pob txha).

Hypermetropic astigmatism los ntawmlub mechanism ntawm qhov tsos yog zoo tib yam rau myopic ib. Ntawm no qhov txawv yog qhov pom kev deb (hypermetropia) yog ib hom kev cuam tshuam thaum lub ntsej muag nyob tom qab retina, thiab tsis nyob rau pem hauv ntej. Kev ua txhaum cai yog qhov nyuaj thiab yooj yim, tau txais thiab yug los.

Mixed astigmatism

Tam sim no xav txog kev sib xyaw astigmatism. Nws sawv cev li cas? Kev sib xyaw astigmatism yog ib qho mob thaum ob hom kev ua tsis pom kev tsis pom kev sib xyaw ua ke: cov kab hluav taws xob ntawm ib qho meridian tsim ua kom pom tseeb tom qab retina (hypermetropic hom), thiab lwm yam nyob rau hauv pem hauv ntej ntawm retina (myopic hom). Nrog rau cov kab mob no, txhua daim duab pom tau tias yog deformed, nws yuav luag tsis tuaj yeem txiav txim siab qhov loj ntawm cov khoom, qhov deb ntawm nws.

Daim ntawv loj tshaj plaws ntawm qhov muag tsis pom kev yog sib xyaw ob sab astigmatism, uas feem ntau yog nrog los ntawm kev txhim kho lig ntawm lub cev tsis pom kev thiab strabismus.

Tus kab mob siab dua, qhov mob nyuaj dua. Yog li ntawd, nws yog ib qho tseem ceeb kom paub txog qhov pom ntawm pathology nyob rau lub sijhawm, txij li kev kho sai sai thiab ntsuas kev kho mob, lawv muaj feem ntau dua rau kev ua tiav.

Yuav kho li cas?

Hom ntawm qhov muag astigmatism thiab kev kho mob
Hom ntawm qhov muag astigmatism thiab kev kho mob

Astigmatism tuaj yeem kho tau. Muaj cov txheej txheem ib ntus ntawm kev kho qhov muag pom, tso cai rau tus neeg mob coj txoj kev ua neej mus txog thaum rov ua tiav:

  1. Cov tshuaj tiv thaiv kab mob. Txhawm rau kho astigmatism, siv cov lo ntsiab muag tshwj xeeb toric, uas tsis ua rau tsis yooj yim thaum hnav, tsis zoo li tsom iav.
  2. kho kom raug. Rau astigmatism, tus neeg mob yuav tsum hnavtshwj xeeb tsom iav nrog lo ntsiab muag nyob rau hauv daim ntawv ntawm ib lub tog raj kheej. Ua ntej lawv xaiv, ib tug neeg tau txais kev kuaj mob tshwj xeeb. Cov kws tshaj lij hais tias hnav tsom iav rau cov neeg uas muaj qhov siab ntawm astigmatism tuaj yeem ua rau kiv taub hau, mob ntawm qhov muag, thiab qhov muag tsis pom kev.

Txawm li cas los xij, hnav cov tsom iav lossis tsom iav tuaj yeem kho qhov pom kev ib ntus. Koj tuaj yeem tshem tau tus kab mob mus tas li nrog kev pab kho qhov muag tsis pom kev (Lasik), uas tsis ntev los no tau siv ntau thiab ntau zaus los kho astigmatism.

Kev Tiv Thaiv

Kev tiv thaiv ntawm astigmatism yog dab tsi? Nws muaj cov nram qab no nuances:

  1. Ua raws li txoj cai ntawm kev pom, kev ua lub cev. Kev pom kev nro yuav tsum tau hloov pauv nrog kev so nquag.
  2. Ua raws li txoj cai teeb pom kev zoo. Qhov chaw ua haujlwm yuav tsum muaj teeb pom kev zoo.
  3. Siv cov vitamins nrog lutein.
  4. Ua gymnastics rau qhov muag. Txhua 20 feeb thaum lub qhov muag mob, koj yuav tsum tau ua gymnastics rau lub cev ntawm lub zeem muag.
  5. Kho qhov muag kab mob uas cuam tshuam rau kev loj hlob ntawm astigmatism.
  6. Kho qhov muag thiab txhim kho cov ntshav ncig hauv lub qhov muag thiab nws cov ntaub so ntswg. Qhov no tuaj yeem ua tiav nrog kev pab ntawm kev kho lub cev zaws - kho xim, pneumomassage thiab lwm yam. Tag nrho cov nta no tau ua tiav hauv lub cuab yeej "Points of Sidorenko".
Qhov muag zoo li cas nrog astigmatism?
Qhov muag zoo li cas nrog astigmatism?

Nws yog ib qho tseem ceeb kom nco ntsoov tias kev tiv thaiv ntawm astigmatism yog ib qho tseem ceeb heev. Hais lus nruj me ntsis, astigmatism tsis yog ib qho mob, tab sis yog "yuam kev" ntawm lub qhov muag. Txawm li cas los xij, qhov no tsis txhais tau tiastias nws muaj kev nyab xeeb. Kev kuaj mob nyuaj thiab kev kho mob tuaj yeem ua tiav hauv ntau lub tsev kho mob ophthalmological. Thaum xaiv lub tsev kho mob, xav txog tsis yog tus nqi ntawm kev kho mob nkaus xwb, tab sis kuj yog lub koob npe nrov thiab qib ntawm cov kws kho mob tshwj xeeb.

Astigmatism hauv me nyuam mos

Ntau hom astigmatism hauv cov menyuam yaus tshwm sim ntau dua li qhov feem ntau ntseeg. Yog li, 40% ntawm cov menyuam kawm ntawv muaj qhov tsis muaj zog ntawm astigmatism, thiab 6% muaj qhov muaj zog. Qhov no pathology tsis tsuas yog ua rau tsis xis nyob rau tus me nyuam, nws kuj yog fraught nrog kev loj hlob ntawm myopia thiab txo qis hauv tsev kawm ntawv kev ua tau zoo. Yog li ntawd, nws yog ib qho tseem ceeb heev kom paub qhov teeb meem no raws sij hawm thiab pib kho.

Ib tug me nyuam raug kev txom nyem los ntawm txhua yam ntawm astigmatism (yooj yim, complex, sib xyaw, thiab lwm yam), raws li txoj cai, tsis yws txog qhov tsis pom kev vim nws ib txwm pom nws li no thiab tsis paub tias nws tsis yog lawm.. Qhov tseeb no nyuaj rau kev kuaj mob tam sim no. Astigmatism nyob rau hauv cov me nyuam feem ntau yog kuaj pom ntawm lub sij hawm nrog tus kws kho mob ophthalmologist. Yog li ntawd, qhia koj tus menyuam mus rau kws kho mob txij li hnub nyoog 2 lub hlis thiab, yog tias kuaj pom tus kab mob no, mus ntsib tus kws kho mob tshwj xeeb txhua rau lub hlis. Thiab noj qab nyob zoo!

Pom zoo: