Also read: Disorders of the Eye Disorders of the Ear
Refractive Errors
- Myopia: near-sightedness, treated with concave lenses. This can be produced an elongated eye, which results in the focused light appearing in front of the retina, rather than on it. This results in blurred vision that only focuses when near the individual.
- Hyperopia: far-sightedness, treated with convex lenses. This is produced by a shortened eye, which results in the light being unable to focus before it hits the retina. This results in blurred vision that only focuses when farther from the individual.
- Astigmatism: irregular curvature of the cornea, treated with cylindrical lenses. This produces streaks of light that appear from light sources.
- Presbyopia: far-sightedness that occurs with aging due to the loss of lens elasticity
| Refractive Error | Cause | Visual Changes | Corrective Lens |
|---|---|---|---|
| Myopia | Elongated eyeball Weak refraction | Nearsightedness | Concave Lens |
| Hyperopia | Shortened eyeball Strong refraction | Farsightedness | Convex Lens |
| Presbyopia | Loss of lens elasticity due to age | Farsightedness | Convex Lens |
| Astigmatism | Abnormalities in the curvature of the cornea | Blurred vision | Astigmatic Lens |
Diagnostic Examination
Visual Acuity Test, most commonly Snellen’s Test. The individual must identify a series of procedurally smaller letters initially simulated to be 20 feet from the individual, viewed through a slit lamp. The results of a visual acuity test is represented by two numbers over a fraction, such as 20/20. 20/20 is the vision of a normal individual.
- At a corrected vision of 20/200, in the Philippines, an individual is legally blind.
Clinically, these refractive errors all feature the blurring of vision and possibly seeing halos. For astigmatism, “silhouettes” can appear to the individual.
Management
The most common corrective method are corrective lenses in the form of glasses or contact lenses. A surgical method that is also commonly used is Laser Assisted In-situ Keratomelliusis (LASIK). This reforms the lens to correct the cornea based on prescription. The cornea is flapped open, a laser is used to reform inner corneal tissue, and the outer cornea is returned into place.
Surgical Considerations for the Eyes
All eye surgeries will share similar steps.
- Pre-operative: administration of antibiotics, anesthetics, and mydriatic medications all administered through ophthalmic drops.
- Mydriatic medication is used to dilate the pupil for better visualization of its structures.
- Post-operative:
- Position: the patient after any procedure is positioned side lying on the unaffected site or semi-fowler’s.
- Avoid excessive eye movement.
- Avoid touching the eye, employing the use of an eye shield during sleep to avoid accidental contact or rubbing of the eye.
- Avoid activities that increase intraocular pressure, similar to those activities that increase ICP such as uncontrolled coughing, bending at the waist, squatting, weight-lifting, straining, etc.
- Monitor for complications: the presence of pain, flashes of light, or visual floaters are all immediate indications for contacting the physician due to increased IOP.
- The presence of redness, itchiness, or glaring are all expected and not indications for referral.
- Dim the lights for comfort.
Cataracts
A disorder characterized by an opacity of the lens, which produce clouding of vision which may eventually result in obstructive blindness. This appears in multiple types:
- Senile Cataracts: cataracts that appear due to aging and the accumulation of free radicals in the lens. Free radicals are a byproduct of oxygen metabolism.
- Congenital Cataracts: the birth of a newborn with cataracts often due to the presence of maternal STIs, particularly those that are blood-borne.
- Traumatic Cataracts: cataract formation due to insult to the lens and subsequent scar formation. These may be due to eye surgery, accidents, or even radiation.
Smoking is a prominent risk factor to the formation of cataracts.
- Secondary Cataracts are sequelae to other disorders, the most prominent of which is diabetes mellitus. In fact, DM is the global leading cause of cataracts outside of senile cataracts.
Signs and Symptoms
- Cataracts form slowly— in early stages, cataracts will produce a cloudy, hazy, fog-like, smoky vision. This leads to poor color perception.
- Blurring of vision and halos around light also appear.
- In late stages, increasing opacity in the lens will present as an apparent whitish discoloration of the lens.
Diagnostic Examination
Visualization of the lens for opacities. This is done via ophthalmoscopy (direct visualization) or slit-lamp examination (machine-guided). Clinical signs and symptoms and patient history is also taken into account.
Management
A cataract is removed surgically, and its underlying cause is treated if it is secondary. There are three methods for cataract removal:
- Intracapsular Cataract Extraction: removal of the entire lens.
- Extracapsular Cataract Extraction: removal of the lens without removing its posterior capsule.
- Phacoemulsification: less risky, less invasive method through the use of a small incision wherein the old lens is broken down and suctioned.
After surgery, the same Surgical Considerations are applied. The removal of a lens means the patient will become aphakic, and as such requires the use of an aphakic lens. This can take the form of spectacles, or through the surgical injection of a prosthetic lens. Most phacoemulsification procedures are done in conjunction with a lens replacement.
Additionally, the patient is advised to stop smoking if they are a smoker.
Retinal Detachment
The detachment/separation of the retinal layer from the choroid layer. Based on its method of separation, there are multiple types:
- Rhegmatogenous: a tear or perforation in the retinal layer causes separation.
- Traction: a physical pulling force on the retina causes its membrane to become thinner, which allows fluids to accumulate in between the retina and the choroid.
- Combination: a combination of pulling and tearing.
- Exudative: the accumulation of exudate between the retina and the choroid as a result of infection, such as serous fluids, pus, etc.
The most common cause of retinal detachment is high myopia where the eye is stretched, resulting in a traction-type retinal detachment.
Signs and Symptoms
- Early stage: visual floaters and flashes of light. Floaters appear from red blood cells and proteins that enter the eye due to tearing or detachment. Flashes are caused by damage to the photoreceptors of the retina.
- Late stage: veil-like/curtain-like vision. The appearance of a section of one’s vision being covered by a curtain. This is caused by severe detachment of the membrane to the point that it is able to obstruct the retina from the light it attempts to perceive.
Management
The main method of management is surgical, focusing on the reattachment of the retinal layer to the choroid layer.
- Scleral Buckling: the use of a scleral belt to compress and alter the shape of the eye to allow for the reattachment of the affected region.
- Vitrectomy: the aspiration of fluids that have accumulated in between layers such as in traction and exudative retinal detachment.
- Retinopexy: the use of air, oil, silicon, or other substances injected into the eye and appropriate positioning in order to allow it to push the membrane back into place.
Glaucoma
The irreversible increase of intraocular pressure (IOP) that results in irreversible blindness from damage done to the optic nerve by the pressure. This may be caused by:
- An increase in the production of aqueous humor (fluid in the anterior chamber of the eye that nourishes and hydrates the cornea).
- A decrease in the drainage of aqueous humor.
Depending on the processes involved in glaucoma, there are two types:
- Open-angle Glaucoma: glaucoma that only involves the presence of increased aqueous humor with the presence of a normally functioning drainage system of the aqueous humor. This appears as a chronic-onset glaucoma as aqueous production is consistently higher than drainage rate.
- Close-angle Glaucoma: glaucoma that involves both the increased aqueous humor with the presence of a dysfunctional drainage system of the aqueous humor. This appears as an acute-onset glaucoma as drainage closes with iris displacement upon pupillary dilation (mydriasis).
Pathophysiology
flowchart TD
A(Tumor)
B(Genetics)
C(Displacement of the Iris)
D(Increased Aqueous Humor)
E(Decreased Drainage)
A-->D
B-->D
C-->E
F(Accumulation of aqueous humor)
G(Increased intraocular pressure)
D-->F
E-->F
F-->G
G-->H
H(Necrosis of the Optic Nerve)
H-->I
I(Permanent Blindness)
Signs and Symptoms
- Glaucoma may initially appear only with an increased intraocular pressure (normally 10 to 21 mm Hg).
- Acute-onset glaucoma (close-angle) presents with pain while chronic-onset glaucoma is painless.
- However, both of these appear with the characteristic loss of peripheral vision that appears as tunnel vision or gun barrel vision.
Diagnostic Examination
Measurement of the internal pressure of the eyes is done with tonometry. Glaucoma is diagnosed as soon as IOP increases beyond the normal limit of 21 mm Hg. There are two types of tonometry:
- Regular Tonometry, an instrument that directly probes the eye to measure pressure.
- Contactless Tonometry, an instrument that utilizes air pressure to measure pressure.
Management
- Medical Management:
- Alpha agonist such as epinephrine. This acts to decrease aqueous production. However, due to the action of epinephrine as a sympathomimetic, it dilates the pupil, which is contraindicated in close-angled glaucoma.
- Beta blockers such as timolol. This acts to decrease aqueous production. This is the first line of
- Carbonic anhydrase inhibitors such as acetazolamide. This acts to decrease aqueous production.
- Miotics such as pilocarpine. This acts to improve aqueous drainage, and is only used in close-angle glaucoma. If this medication is cloudy, discard it.
- Considerations:
- The treatment to be used is lifetime. Glaucoma is irreversible and incurable.
- Medications are administered to both eyes (OU).
- Apply pressure on the lacrimal ducts to prevent systemic absorption of the drug.
- Medications should always be available.
Otitis Externa
Hearing Loss
Hearing loss is present in many ear disorders. It may occur in two forms:
- Conductive hearing loss: a problem appears in the conduction of vibrations that occurs in the outer and middle ear. This is likely reversible.
- Sensorineural hearing loss: a problem appears in the nerves and brain that occurs in the inner ear. This is likely permanent.
Otitis externa is the inflammation of the outer ear, also known as Swimmer’s ear. This may be caused by:
- Infection via both bacterial and fungal microorganisms.
- Allergic reactions
- Heavy metals: non-hypoallergenic jewelry.
- Cosmetics and other chemicals
Signs and Symptoms
- The signs of inflammation: rubor, tumor, calor, dolor (and/or itchiness)
- Conductive Hearing Loss
- Discharge, if severe
Diagnostic Examination
A diagnosis is based on symptomatic assessment and a potential culture and sensitivity if infection is suspected.
Management
- Antiinflammatory: inflammation requires antiinflammatory.
- Antimicrobials: if bacterial or fungal causes are suspected.
- Antihistamine: reduce inflammatory reaction if allergy is suspected.
- Cold compress
- Analgesia for dolor
- Talk to the patient with their unaffected ear. Stand on the side that is unaffected.
- Patient Instruction: (a) avoid touching ears, (b) do not use earphones or headphones, (c) use hypoallergenic items to reduce irritation, and (d) avoid showers and swimming; wetting the ears in general.
Otitis Media
Otitis media is the inflammation of the middle ear, also known as glue ear. The only cause of otitis media is a upper respiratory tract infection (URTI) as it travels from the upper respiratory tract (nasopharynx, oropharynx) through the eustachian tube to the middle ear. The most common causative agent is Haemophilus influenzae, also the most common cause of upper respiratory tract infections.
- Incidentally, most cases of otitis media is found in children whose eustachian tubes are short, straight, and wide.
Signs and Symptoms
- Redness of the ear drum
- Pain or itchiness
- Foul-smelling discharge
- Feelings of fullness in the ear; bulging eardrum
- Increased risk for tympanic membrane perforation which, if present, will also produce discharge.
Diagnostic Examination
A diagnosis is based on symptomatic assessment and a potential culture and sensitivity if infection is suspected via tympanocentesis.
Management
- Administer antibiotics
- Administer anti-inflammatories
- Administer analgesics
- Surgery: myringotomy to facilitate the drainage of any exudates present in the middle ear. This will allow for faster healing.
Surgical Considerations for the Ears
Pre-operatively, there are often no special considerations. Post-operatively,
- Avoid blowing the nose as this can injure the surgical area.
- Avoid showers and swimming.
- Avoid riding planes due to the potential of barotrauma. However, if absolutely necessary, instruct the patient to chew gum to facilitate opening of the eustachian tube.
Otosclerosis
The formation of new spongy bone around the stapes, the last ossicle bone in the middle ear. It is the last of the three ossicle bones, starting with the malleus, the incus, then the stapes. This new bone causes failure in the conduction of vibrations being transferred. Its exact cause is unknown.
Signs and Symptoms
- Conductive hearing loss
- Tinnitus
- If severe (rarely), nystagmus can also appear as a manifestation.
Diagnostic Examination
Visualization can be done, along with hearing tests (Weber and Rinne)
Management
- Drug of Choice: Sodium Fluoride is known to decrease the progression of calcification.
- Surgery: stapedectomy and subsequent prosthesis.
Meniere’s Disease (Endolymphatic Hydrops)
The accumulation of fluids in the inner ear which is a form of third space shifting. There are many causes for this disease, but it all boils down to fluid volume excess.
Signs and Symptoms
There is a Meniere’s Triad that is classical for this disease:
- Tinnitus
- Vertigo
- Sensorineural Hearing Loss
Management
- Administer diuretics, specifically thiazides such as Hydrochlorothiazide (Diazide)
- Administer antiemetics or antivertigrals such as Promethazine (Phenargan)
- Diet: reduced salt to facilitate the reduction fluid volume, as well as decreased oral fluid intake.
- Promote safety: avoid sudden head movements to avoid vertigo. Injury is a common problem with patients with problems with balance.