Refractive Error Girls work from Dr.Sameerjamal lectures records 2010
RE عيوب الإنكسار • Types of RE: 1- Myopia 2- Hypermetropia 3- Astigmatism 4- Presbyopia • Emmetropia: with no RE • Ammetropia: with RE • Anisometropia: one eye has more RE than the other. This type is associated with complications
1- Myopiaقصر النظر • It’s the most common one • Majority of patients complaining of vision loss usually due to RE 90 % and 10% for organic causes. • The light normally falls on the retina : • If the light get refracted before reaching to the retina the image will be focus in front of the retina. Pathogenesis : 1- Eye is larger than it should be, makes the light bent in front of the retina 2- Refracted power of the eye (mainly cornea) is higher than usual (Miss match between the axial length and refracted power of the eye.) • To look at the subjects from near distance less than 6 meter we use our lens (use it for accommodation mainly ) , but more than 6 meter we use our cornea. • Why people have myopia ? Causes ? • Congenital • Acquired (inherited – Environmental (children at there 1st year of life have higher incidence), reading in dark room , excessive reading . – lenses subluxation(by trauma or Marfan’s syndrome) the lens still in the visual axis – Drugs( ocular drugs affect the eye as (sulphonamide & tetracycline) and the body ) – DM: when it’s not control the lens swells up by fluid so RP of eye increase and myopia occur, but if it was controlled the lens shrink and the myopia goes away. • Idiopathic
Classification of myopia according to : • Pathogenesis • Time of onset ( congenital or acquired ) Myopia it can be : • Simple 90% : majority of cases present with simple myopia less than 6 degree and they don’t have complications in the retina from myopia. • Malignant 10%: continuously progressive start fro m – 1 to مالا نهاية ممكنand it increased with time and it’s associated with retinal changes and visual loss. It’s usually more than -6 degree. Cause for malignant Myopia : • It keeps continue to growth, the retina is attached to choroid (attached to) sclera. The eye is enlarged from the out side and the retina is stretching inside, with this stretching eventually cause retinal tears and the end result will be retinal detachment. • So for simple myopic patients they have to follow up their ophthalmologist for life, cause they might have malignant myopia and have retinal complications. • We give atropine drops to arrest the progression. Treatment : • Glasses ( minus glasses bi concave), for a child with mild myopia we don’t prescribe glasses but after .75 and more we can . • Contact lenses : we don’t describe it for children cause it has so many complications such as : (infections – allergies)and their myopia will get worse , cause contact lenses is a foreign body. suitable age is 11 and more • Surgery : most of the time it’s for cosmetics reasons not for medical . 1- Lasik on the surface of the cornea to change it’s RP. 2- intra ocular lenses ( phakic IOLs) : it’s for the patients not suitable for Lasik surgery. Criteria of successful surgery : • For myopia ( - 6 degree or less ) • Age between 21 – 25 not before that because simple myopia will continue to change until the age of 21 • Make sure that this myopic patient (22 yo or more ) doesn't have any progression for the last year before doing the surgery. NB: بعض الناس مثلا الي يروحوا الجيش ممكن نسويلهم عملية من سن 18 عشان طبيعة حياتهم ماتنفع بوجود النظارات - Myopia complication is amblyopia .
2- Hypermetropiaطول البصر • It’s due to miss match between the axial length and the RP of the eye . It means that the eyes is actually smaller than it should be , so the images will be focus behind the retina . • Causes : 1- Congenital : majority of cases have a congenital hyperopia . Every one is born hyperopic because our eyes is small and still growing . So physiological hyperopia is (+2) if it’s more it will be pathological. 2- Acquired : the minority of the cases. it's due to : • Aphakia :is the absence of the lens of the eye, due to surgical removal, a perforating wound or ulcer, or congenital anomaly. So in cataract the lens will be removed so the patient will become hyperopic . - Lens dislocation by trauma. Treatment : the same as myopia NB : the surgery in hyperopia is less successful than myopia and the suitable age for the surgery is 18 years. • As a GP how you going to know if the patient who wear glasses is myopic or hyperopic by just inspection ? The glasses in myopia is make the patient eye looks smaller (make the objects looks smaller ) but the glasses in hyperopic patients makes his eyes looks bigger. • patients with hyperopia basically they can’t see the far objects so they use their lens to correct this distance ,so they can’t see the near objects as well ,because they using the accommodation mechanism to contract their lens to correct the hyperopia. (this is in mild hyperopia) • In sever cases : 4 and more even if they accommodate they can’t correct the vision for distance so they can’t see the near & far objects because they have reached the maximum accommodation.
3- Astigmatism اللاغورية • The curvature of the lens or cornea may vary in different meridians causing and image blur on the retina ( oval shape). • Most of the people have spherical RE but in Astigmatism the lens is oval is shape and that’s makes the refractions not equal from all the surfaces. • If the light rays all focused on the retina and some rays focus in front of the retina this is called ( myopic Astigmatism) • If the light rays all focused on the retina and some rays focus behind the retina this is called ( hyperopic Astigmatism) • In astigmatism the image is distorted in a particular angel. • Any abnormal head postural in a child is consider eye problem until prove otherwise. • A symptom of astigmatism is head tilting and turning. Causes : 1- congenital : most of the time A lot of children have physiological Astigmatism that fades away with age .but some of them will continue. So until the age of 20 the patient has to go to ophthalmologist not to optometrist. 2- Acquired: • Contact lenses that treat the myopia with continuous pressure it will cause astigmatism. • Lens sublaxation ( on one side only) • Hereditary disorder of the cornea as keratoconus Treatment : the same but with cylindrical lenses ( that has a power in only one meridian) - The power of the lenses and the meridian it will work on from 0 to 180 degree .
Presbyopia • It’s acquired from 40 -45 years old. • Due to loss of lens elasticity because of proteins deposit in the lens. Even if the zonules are intact the lens is not elastic . And we use our lens when we are reading or to see at less than 6 meter distance. • presbyopia is hyperopia of older age and it’s physiological acquired inability to read at certain age group. • If the person get older and he can read without a glasses that means: • He is already have myopia • Eye problems as early cataract. • Some children have presbyopia symptoms as in accommodation paralysis (neurological dis ) • Treatment : - Limited lens – 3 diopter why ? Because -3 (power of the lens) is the maximum distance for reading 100/33=3
Role of GP in management the RE? 1- educate the patient before referral to ophthalmologist. 2- if the child have a RE we have to prescribe glasses , otherwise the child will develop amblyopia (lazy eye, it develops from 0-12 years old). For age < 20 with only visual loss refer to ophthalmologist. > 20 years old patient with RE refer to ophthalmologist or optometrist > 20 with organic problem refer to ophthalmologist - For the GP : to differentiate between RE & organic problem use the multiple pinhole test (MPH), if the vision improved then it’s a RE if it’s get worse it’s organic. 3- screening the patients for RE & visual loss by testing the visual acuity. 4- formal eye examinations at the 1st 2 years of all children. NB: prescribing glasses is objectives (depend on the tools not on the patient). • RE diagnosis is OBJECTIVES. • GP confirm the Dx of RE by MPH test. How is RE diagnosed by ophthalmologist ? - Retinoscope -Autorefractometers Examination of children for RE: 1- children that have +ve FH of RE they have to follow up with the ophthalmologist at the 1st year of their life. 2- Routine and regular eye examination at (2-5-12) years old . This with patient have –ve FH. 3- any children have symptoms of RE as : headache , strabismus ..etc , need to be seen. Types of lenses : 1- Monofocal lenses : for myopia & hypermyopia has power = 360 (spherical lenses) 2- Cylinderical lenses: for astigmatism (has power in one meridian) 3- Multifocal lenses : for prespyopia and myopia