Eye treatments: In order to enhance the effectiveness of treatment, in addition to topical application, eye injection methods often have to be combined.
There are many methods to help drugs get into the eye directly and more than systemic sugar. Choosing appropriate ophthalmic methods has a significant impact on treatment outcomes.
The topical medication is applied to the conjunctiva with the lower map, from which the drug will penetrate the cornea and the conjunctiva into the anterior part of the eyeball. About 80% of the drug gets into the eye through the cornea, the rest is through the conjunctiva or tears. The corneal epithelium is an obstacle to the passage of drugs when the corneal epithelium is damaged by pathological processes, the ability of the drug to permeate the cornea is greatly improved. However, a significant amount of eye drops is absorbed into the body and can cause systemic side effects, especially toxic reactions (e.g. atropine, adrenalin, etc.). Common eye drops come in two forms:
Liquid eye drops
Liquid eye drops are the most commonly used form of eye medicine. Liquid medicine has the advantage of being easy to use and does not affect eyesight. The downside of the liquid medicine is that the shelf life on the conjunctival-corneal surface is very short (90% of the drug is removed from the eye after 1-2 minutes), the shorter the duration of the drug if you blink a lot, because Therefore, in order to increase the effectiveness of the drug, the number of times to be used is often higher and should not be blinked much after applying for the medicine. Most eye drops come in the form of water.
Ointment less stimulating, and less absorbed through the religion, more stable than liquid medicine and longer shelf life in the eye should be able to reduce the number of medications. The downside of the ointment is that it forms a thin layer in front of the cornea that causes blurred vision, causes eyelashes to stick, and often causes contact dermatitis. The ointment should be used at noon and at night before bedtime. Medicines commonly used in the form of ointments are antibiotics (tetracycline, aureomycin, gentamycin, chloramphenicol), antiseptics (methylene blue, mercury gold oxide), antivirals (Zovirax) and some relaxants or contractions. pupil.
Put the medicine in the eye
To overcome the shortcomings of ophthalmic medications, which are the short shelf life of the eye and the uneven amount of the drug absorbed into the eye, a drug-impregnated membrane (almost a contact lens) or a small pill is produced. (almost a grain size) used to put in contact with the corneal conjunctiva or with the bottom. The drug will release slowly, steadily and for a long time (possibly up to 1 week). The most commonly used medications in this form are pupils that are dilated or dilated pupils (pilocarpine or atropine).
Figure - The pupil dilating pill in the eye
Inject medication in the eye
In many eye diseases, to enhance the effectiveness of treatment, in addition to topical application, people often have to combine eye injection methods to give more medicine to the eye. There are different methods of eye injection depending on the location of the pathological lesion:
Inject under the conjunctiva
The sub-conjunctival injection is used to treat diseases of the anterior eye part. Some drugs that do not penetrate the eyeballs through the eye route when injected under the conjunctiva can diffuse into the eye through the corneal margin or sclera.
Technique: after applying a local anaesthetic, using a syringe with a small needle to poke through the conjunctiva about 3-4 mm from the edge, injecting under the conjunctiva an amount of drug about 1/4 ml to 1 mm. The conjunctiva will experience mild edema at the injection site.
Medicines commonly used for sub-conjunctival injections: antibiotics, corticosteroids, pupil dilators and ciliary paralysis (to prevent iris stickiness in the treatment of uveitis), 5-fluorouracil (anti-metabolic drugs, to reduce scarring fibrosis after glaucoma surgery).
Tenon subcapsular injection
Tenon subcapsular injection is used in the treatment of diseases of the anterior eyeball. Drugs used to inject under the conjunctiva are also used under the tenon condom.
Technique: after applying a local anaesthetic, use small forceps to gently lift up the conjunctiva and poke the needle under the conjunctiva toward the back. The drug that is injected under the tenon capsule can spread further back.
Figure - Tenon subcapsular injection
Inject after the eyeball
Post-ocular injection is a fairly common method in the past, mainly for the treatment of diseases of the optic nerve and of structures in the muscle apex.
The technique: use a long needle through the skin or through the same object under the eyeball, to pass the drug into the muscle apex behind the eyeball.
Commonly used drugs: anaesthetics, antibiotics, corticosteroids, vitamins, vasodilators. Some injections behind the eyeball can cause complications such as needle sticking to the eyeball, hematoma behind the eyeball, sometimes causing paralysis or loss of vision (often temporary), so this method is more and more current. less and less used.
Injections next to the eyeball
Parallel injection of the eyeball is intended to deliver medication to the area either before or after the equator of the eyeball, which can be injected through the skin or through the same underlying object. Commonly used drugs are antibiotics or corticosteroids. Parenteral injections are less likely to cause complications than post-ocular injections, so in recent years this technique has been widely used to anaesthetize eye surgeries instead of post-ocular injections.
Inject in the anterior chamber
This is a method of bringing drugs directly into the anterior chamber, mainly used for severe uveitis or used in surgery.
Technique: after injecting the anaesthetic with topical anaesthetic, use a small knife to poke the anterior chamber at the edge in the direction parallel to the iris surface, then use a syringe with a conical needle through the hole to inject medicine into the room. Care should be taken when handling because there may be complications of anterior haemorrhage or tearing of the glass capsule.
The drugs commonly used for injection in the anterior chamber include antibiotics, corticosteroids, and pupil (in surgery).
Inject in vitreous
In some severe cases of intraocular infections (such as endocarditis), the vitreous injection method is used to deliver the drug directly into the eyeball. antibiotics and corticosteroids. When injecting in the eyeball, only a small amount of drug (0.1 - 0.2 ml) is used with a low concentration to avoid toxicity to the vitreous and retina.
Electrophoresis is a method that can help drugs overcome the corneal epithelial barrier. The drug solution is placed in contact with the cornea and stored in a small cup that carries an electrode. The drug is absorbed into the eye when an electrical potential is generated. The electrode must match the charge of the drug in the solution. Corneal anodes are commonly used for drugs with a positive charge (e.g., gentamycin, kanamycin, streptomycin). Corneal negative electrodes are commonly used for negatively charged drugs (cephalosporins).
Wash eyes repeatedly
In some cases of severe infections (such as corneal ulceration caused by green pus bacillus), to constantly bring antibiotics into the eye.
Technique: the patient lies in bed, using an infusion bottle connected to a tube with one end of the tube fixed to the eyelid. The patient's eyelids are fixed with tape. Each eyewash lasts about 1 hour, can be repeated 2 to 3 times a day.