Ophthalmology: Common conditions affecting the external eye

Ophthalmology: Common conditions affecting the external eye

You should recognize and treat blepharitis, meibomian gland dysfunction and dry eyes which are the most common causes of ocular discomfort in adult patients.

Aims

Detection and medical management of:

  • Blepharitis and meibomian gland dysfunction (MGD).
  • Dry eyes.
  • Allergic eye disease.

The tear film

The eyelid margins have lashes on the anterior lamella, and the meibomian orifices open behind the grey line from the posterior lamella (Figure 32.1). The tear film is bound to the cornea by microvilli glycocalyx on the epithelial goblet cells. The deepest layer is mucin, which is very thin; the middle layer is aqueous and the surface layer is lipid, from the meibomian glands (Figure 32.2).

Treatment

Depends on the underlying cause. If severe, corneal scarring with superficial vascularization leads to reduced vision and even corneal perforation.

Common conditions

Blepharitis and meibomian gland dysfunction (MGD)

Blepharitis

Low-grade chronic staphylococcal lid margin disease with ‘redrimmed’ eyelids in young adults and middle-aged persons (Figure 32.3).
Symptoms: itchy, sore, watery eyes.
Signs: red-rimmed lid margins, eyelash crusts and collarettes, and distorted lid margin microanatomy (irregularities, pits and telangiectasia).
Management: Blepharitis cannot be ‘cured’ but can be managed to minimize symptoms, which are often a nuisance but rarely sight threatening.
Daily lid hygiene is imperative.

  • Warm compresses twice daily. Run a flannel under warm tap water, and apply to the closed eyelids for 1 minute to soften the thickened oil in the meibomian glands and dilate the opening of the glands. The oil is crucial to tear stability, improving the surface tension of the tears.
  • Firm pressure applied to the closed eyelid margins through the flannel, wiping side to side to express the oil and scrub or lift adherent debris (mixture of dead skin cells and secretions) from the lashes.

In addition, lubricate the eye with artificial tear drops and treat infections when present and recommend a diet rich in Omega 3, 6 and 9.
Oral lymecycline, doxycycline or minocycline for several months.

Meibomian gland dysfunction (MGD)

Thick oily meibomian secretion causing stingy sore eyes and red thickened eyelids. Poor aqueous tear film results. Often associated with rosacea (Figure 32.4). Management is as for blepharitis, adding antibiotic for rosacea.

Upper eyelid entropion

Mild upper eyelid entropion from chronic staphylococcal lid margin disease.
Symptoms: foreign-body lash sensation and dry, gritty eyes.
Signs: trichiasis and punctate epithelial corneal stain.

Management
  • Epilation, electrolysis and cryotherapy trichiasis, medical topical lubricants and anterior lamella reposition.

Pterygium

See Figure 32.6.

Dry eyes

Idiopathic dry eyes

Symptoms: gritty, sandy, burning dry eyes with reflex tear flooding.
Signs: poor tear film, interpalpebral punctuate epithelial staining and poor wetting on litmus paper (Schirmer’s test).
Management: Vigorously treating blepharitis and meibomian gland dysfunction, use of artificial tears without preservatives and carbomeric gels, and surgical punctal occlusion with punctual plugs or punctual cautery.

Sjögren’s syndrome

This exocrine gland hypofunction affects the lacrimal, salivary glands and the gastrointestinal tract. It predominantly affects women (90% cases), and the age of onset is from 35 to 55 years. Primary Sjögren’s syndrome is idiopathic (approximately 50%). Secondary causes include rheumatoid arthritis, lupus or scleroderma. Symptoms are severe fatigue; dry eyes, nose and throat; dental caries and digestive problems. Vision can be impaired from epithelial damage and subsequent conjunctival and corneal scarring.

Other causes of dry eye
  • Stevens–Johnson syndrome
  • ocular cicatricial pemphigoid (Figure 32.8)
  • lacrimal gland trauma (surgical excision or ductile destruction) and chemical, radiotherapy and thermal injury
  • fibromyalgia and chronic fatigue syndrome.

Superior limbic keratitis (SLK)

The typical patient with superior limbic keratoconjunctivitis (SLK) (Figure 32.7) is female, aged 20–60 years with chronic symptoms of bilateral red and irritable eyes. It may be asymmetrical. After episodes of exacerbation and remission it usually resolves. The patient may also have abnormal thyroid function.

Management
  • SLK has been treated with silver nitrate or thermal cauterisation of the superior bulbar conjunctiva, pressure patching, and large diameter bandage contact lenses (BCL), topical trans-retinoic acid 0.1%, and recession or resection of the superior bulbar conjunctiva.
  • Over 50% of patients with SLK are said to have keratoconjunctivitis sicca (severe dry eye). Punctual plugs have also been used to treat SLK.

Allergic eye disease

Hayfever

This is seasonal allergic conjunctivitis, from type 1 immediate immune response with histamine release to allergens such as pollen.
Symptoms: bilateral, itchy, watery eyes with lid swelling and sometimes mucous discharge. Rhinorrhoea and sneezing. Worse in young people with atopy.
Management: topical mast cell stabilizer (e.g. sodium chromoglycate or lodoxamide).

Perennial allergic conjunctivitis

This is triggered by allergens such as house dust mites, moulds, pollens, food preservatives and animal dander. It is bilateral, with episodic symptoms. Management is the same as for hayfever, plus oral and topical antihistamine when severe.

Vernal keratoconjunctivitis sicca (VKC)

This is a young person’s disease (7–11 years). Signs include characteristic upper tarsal conjunctival cobblestones, which
may induce ptosis. There are often perilimbal giant papillae, known as limbal vernal. Management is as for hayfever, plus topical steroids when severe.

Acute allergic conjunctivitis

Sudden, unilateral, itchy lid swelling and marked conjunctival chemosis.
Signs are worse than symptoms. Triggered by plant allergens.
Resolves spontaneously without treatment within 24–36 h.

Common conditions affecting the cornea

The cornea is the window of the eye. It must be clear and healthy to function well. It requires protection by the eyelids, a healthy tear film as well as a healthy endothelial pump to keep it transparent. It is highly sensitive.

Aims

  • Outline the basic anatomy of the cornea.
  • Know the signs and symptoms of corneal disease.
  • Describe common disease processes involving the cornea.

Corneal clarity

The cornea is clear due to its highly organized structure of collagen fibres. It is free of blood vessels and allows the passage of light in an organized way so that a clear image is focused on the retina (Figure 33.1). The corneal layers all contribute to its function. The deepest endothelial cells actively pump fluid out from the stroma.
Disturbance of the eyelids, conjunctiva or tear film may lead to corneal problems, including ulceration. If corneal ulceration is severe, scarring with vascularization may lead to reduced vision and, in rare cases, to corneal perforation requiring surgical management. Corneal anaesthesia (fifth cranial nerve palsy) predisposes one to severe keratitis.

Corneal disease

Keratitis

General term used to denote inflammation of the cornea from infection and inflammation.
Symptoms: pain and photosensitivity which may be absent in herpetic disease due to corneal hypoaesthesia, reduced visual acuity and/or discharge.
Signs: reduced visual acuity and circumcorneal injection—a red, inflamed eye, the presence of staining on fluorescein drop instillation, visible corneal infiltrate with or without anterior chamber hypopyon and blepharospasm.

Marginal keratitis

This peripheral cornea ulcer is an immune reaction to chronic staphylococal lid margin disease.

Infections

Bacterial keratitis

Secondary to minor trauma (corneal abrasion or contact lens wear).
Treat as an emergency as severe infections can lead to corneal perforation, endophthalmitis and loss of vision.

Often due to Pseudomonas in contact lens–related keratitis which causes rapid corneal opacification and melt in less than 24 h (Figure 33.3). Rapidly identify the infective agent by C&S and treat with intensive topical antibiotics.

Acanthamoeba keratitis

Acanthamoeba is characterised by pain and causes prolonged corneal infection. It is associated with poor contact lens hygiene, daily wear soft contact lenses and especially the use of tap water in lens cleaning.
Diagnosis may require corneal biopsy and histological assessment.
Look for a corneal Wessely ring using the slit lamp (Figure 33.4).
Corneal grafting may be required for chronic infection with deep corneal stromal scarring and acanthamoeba cysts.

Viral keratitis

Herpes simplex types 1 and 2:

  • Epithelial disease—dendritic ulceration.
  • Stromal disease—disciform keratitis:
    ○ Immune mediated, presenting as a disc-shaped area of corneal oedema, hence the term ‘disciform’
    ○ Stromal necrosis may result in scarring with vascularization, reducing corneal sensation, clarity and vision.
    Treat epithelial disease with antiviral medication (e.g. aciclovir topically and/or systemically). Use topical corticosteroids judiciously for disciform keratitis.

Herpes zoster ophthalmicus (Figure 33.6) Affects the fifth cranial nerve with segmental skin vesicles and erythema, of the upper eyelid, but not crossing the forehead midline. There is associated headache, malaise and fever. There is variable corneal involvement with conjunctivitis, seen as multiple epithelial pseudodendrites and anterior stromal infiltration responsive to topical corticosteroids. Increased risk in immunocompromised patients (e.g. HIV). Treatment is with systemic antivirals.

Inflammation

Peripheral necrotizing keratitis

Related to an underlying systemic vasculitis (e.g. rheumatoid arthritis, systemic lupus erythematosis or Wegener’s granulomatosis). Peripheral destruction of corneal tissue is secondary to an ischaemic microvasculitis in the adjacent scleral and conjunctival vessels, or mediated immunologically by blood-borne factors or matrix metalloproteinases secreted into the tears. This pathological process is exacerbated by secondary Sjögren’s syndrome.
Treatment: treat the underlying disease process with systemic immunosuppression. Treat corneal perforation conservatively with tissue glue, bandage contact lenses or corneal grafting.

Hereditary corneal dystrophies

Occurs in any level in the cornea: epithelial, stromal and endothelial.
When severe, corneal grafting may be required to restore vision, although dystrophic changes often recur in the grafts.

Fingerprint and map-dot corneal epithelial dystrophies cause acute painful recurrent corneal erosions, particularly on waking. Other dystrophies include lattice dystrophy, with deposition of amyloid in the corneal stroma, and inherited disorders of corneal metabolism (e.g. granular and macular dystrophy).
Fuchs’ endothelial dystrophy results in corneal clouding because of endothelial pump failure. The painful bullous keratopathy is treated with a bandage contact lens and eventual keratoplasty.

Keratoconus

Common hereditary corneal dystrophy that is associated with Down’s syndrome, disorders of collagen metabolism or atopic eye disease or is idiopathic. Keratoconic patients require special-fit contact lenses and, if needed, corneal grafting (Table 33.1). (See Chapters 34 and 35).

Management options
  • Contact lenses
  • Collagen cross-linking; this recent development in the management of keratoconus is to slow disease progression. The corneal epithelium is debrided and riboflavin drops are applied, followed by ultraviolet A exposure 370 nm for 30 min to strengthen the corneal stroma by creating new collagen cross-links which helps slow deformation of the cornea.
  • Intracorneal ring segments: implants made of PMMA which are placed in the corneal mid-stroma to flatten it and change the shape of the cone to reduce the astigmatism and make it less irregular. The channels to place the implants can be cut manually or by using a femtosecond laser. Typically, two arc-shaped implants are used for early keratoconus with a clear central cornea.
  • Corneal graft: full-thickness graft, known as a penetrating keratoplasty (PK), or a lamellar or layered graft, known as a deep anterior lamellar keratoplasty (DALK).

Corneal neoplasia

Conjunctival-corneal intraepithelial neoplasia (CCIN) and squamous carcinoma are important rare conditions that are more common in fairer-skinned individuals in hotter climes and in immunocompromised patients with HIV. Treatment: surgical excision or local destructive procedures.

Medical uses of contact lenses

Contact lens wear is common in the general population to correct refractive errors. They are also used as a bandage on a painful cornea and as a cosmetic prop. Unfortunately, contact lens wear can be associated with corneal morbidity.

Aims

  • Medical indications for contact lenses (CL).
  • Complications of contact lens wear.
    Contact lenses are an excellent alternative to glasses. They are also widely used therapeutically in corneal disease. They are fitted for each patient based on the steepness and diameter of the cornea.

Keratoconus

In keratoconus, gas-permeable hard CL are used. Some soft CL are suitable, too, in the early stages. Once the corneal curvature is very ‘steep’, or the cornea is very thin, corneal graft becomes necessary.

Therapeutic bandage contact lenses

These are soft contact lenses with several functions.

Protection of normal epithelium

  • Trichiasis—to prevent lashes from rubbing the cornea.
  • Lid margin deformation (e.g. lower lid entropion with lashes touching the cornea, as temporary relief until surgery can be performed)
  • Protection of corneal graft epithelium.
  • Dry eye (e.g. pemphigoid and Stevens–Johnson syndrome).
  • Exposure keratitis—following seventh cranial nerve palsy.
  • To protect the cornea if there are sutures on the lid margin or under the eyelid, abrading the cornea. Use until sutures dissolve or can be removed.

Healing abnormal epithelium

  • Corneal epithelial dystrophy (e.g. Cogan’s microcystic epithelial dystrophy, Meesman’s dystrophy, Reis–Buckler’s dystrophy and map-dot or fingerpoint dystrophy).
  • Chronic corneal ulcers—due to herpes simplex or vernal keratoconjunctivitis.
  • Abrasions and erosions.
  • Filamentary keratitis—also rapid relief of the discomfort caused by the corneal filaments.
  • Chemical, thermal and irradiation burns—high high-water-content CL may be useful to restore normal epithelialization.

Moulding and splinting

  • Post-keratoplasty (corneal grafting)—to flatten and reposition the graft when lifting or displacement of graft occurs.
  • Wound leaks—small corneal perforations need tight fitting; posttrabeculectomy bleb leaks need large lenses to cover the leak.

Pain relief

  • Bullous keratopathy—CL help to alleviate pain by covering exposed nerve endings (Figure 34.2).
  • Postrefractive surgery—photorefractive keratectomy (PRK) and laser-assisted sub-epithelial keratectomy (LASEK) for pain relief and wound healing.

Complications of contact lenses

Corneal physiology

The constant metabolic activity in the cornea maintains transparency, temperature, cell reproduction and the transport of tissue materials.
The main nutrients are glucose, amino acids (from the aqueous humour) and oxygen (from the tear film by diffusion when the eye is open, and from the tarsal conjunctiva when the eyelids are closed).
Without oxygen, there is hypoxia or anoxia.

Hypoxia and anoxia

There are virtually no lenses available that fully meet the oxygen requirements of the cornea, and there is no CL as physiological or oxygen permeable as having no CL on the eye.
One of the first important effects of hypoxia (which the patient is unaware of) is a drop in corneal sensitivity. Anoxia causes corneal swelling, especially of the epithelium. If there is not enough oxygen available to convert glucose, by the means of glycolysis, into energy, the waste product (lactic acid) is allowed to diffuse and build up in the stroma. Sufficient osmotic pressure is created to allow water to be drawn into the stroma faster than the endothelial pump can remove it, so eventually corneal epithelial and stromal swelling occurs.
Lack of oxygen results in acute epithelial necrosis, microcystic epitheliopathy, epithelial and stromal oedema and corneal neovascularization.

Anatomical effects

Result in the following: tight lens syndrome (Figure 34.3), corneal abrasions (foreign bodies), three and nine o’clock staining (drying of corneal surface and abnormal blink), inferior corneal stain (incomplete blinking), dimple veil (static air bubble under lens) and over-wearing syndrome (mechanical and metabolic factors).

Biological activity

The presence of a CL acting as a biological active surface can cause:

  • Toxic keratopathy (proteolytic enzyme—the chemical preservative in lens-cleaning solutions).
  • Thiomersal keratopathy (the preservative in CL solutions or instilled eye drops acts as a hapten, causing a delayed hypersensitivity response)
  • Giant papillary conjunctivitis (multifactorial aetiology—immune response to antigenic proteins on lenses and mechanical effects of lens edge) causes red sticky eye.
  • Sterile corneal infiltrate—inflammatory response in the absence of an infecting organism, hypersensitivity to disinfectants and bacterial products as well as lens fit are aetiological factors.

Microbial keratitis

Caused by a complex interaction of various factors and increased ocular susceptibility and exposure to pathogens, and it is associated with Pseudomonas, Staphylococcus and Acanthamoeba (ubiquitous free-living protozoan). Hypopyon ulcer many occur. Even a small hypopyon ulcer can rapidly progress (Figure 34.4).


Guidelines for managing microbial conjunctivitis

Emergencies are a routine occurrence in CL practice.

  • Leave the lens out—inflammatory symptoms of lens-related disease
    respond within a few days of ceasing lens wear.
  • Exclude microbial keratitis.
  • Do not treat a red eye with steroids when there is a corneal ulcer.

Advice for patients

Maintain a high standard of CL hygiene. Lenses should be cleaned and disinfected each time they are removed. Avoid overnight wear.
Have back-up spectacles. Leave lenses out when adverse symptoms or a red eye develops.
Feel good—look good—see good: if these criteria are not met, the patient should seek help.

Cosmetic contact lenses

Used to hide a corneal scar or aniridia or to disguise iris abnormality (Figure 34.5). Can have a visual pupil through which the wearer can see, or it can be occlusive.
These are becoming increasingly popular, often with larger diameter coloured lenses to make the eyes look bigger cosmetically.