Contact Lens–Related Complications

Function

Tear and Contact Lens Interaction

The corneal tear film plays a vital role in maintaining the functional integrity of the cornea. It acts as a barrier, nourishes, and lubricates the corneal surface. The cornea is the primary refractive surface and comprises numerous refractive elements.[8]

It is vital to maintain the transparency and integrity of the cornea. The contact lens acts as a barrier between the tear film and the cornea and hampers the harmonious relationship between the two. This interaction reduces contact lenses' health, functioning, efficiency, efficacy, and acceptability.[9]

Lens Position and Tear Film Interaction

The lens can't be clamped or stuck to the cornea. The properties of the tear film, such as surface tension and viscosity, act as glue to hold the contact lens over the cornea surface.[10] Once the lens is inserted inside the eye, the conjunctival mucus rubs against the lens surface with several blinks, and tear fluid helps to wet the lens. The tear fluid spreads all over the lens surface, including the periphery, and helps to stick the lens to the surface.[11]

The pre-lens tear film acts as a plastic sheet to hold and tack the lens due to the firm, cohesive force between the water molecules and also serves as an adhesive force between water and the lens material. Approximately 11grams of force is needed to displace the lens as per experimental studies. When the tear film covering the lens breaks, the method of internal adhesion plays a key role. Negative pressure builds up between the lens, the corneal surface, and the tear film. It acts as a collar between the edge of the lens and the cornea, and this tear film acts as a container for the lens. When measured, this negative pressure is approximately 29 dynes/ cm.[12]

Optical Properties

The tear lens or the post-lens tear film interface plays an essential role in improving the function of the contact lens.[13] The irregularities on the corneal surface are filled by the back of the tear lens film, thus forming a uniform optical surface, and the front surface of the tear lens is shaped by the rear surface of the contact lens.[12]

The refractive index of the cornea is 1.376, and that of tears is 1.337. If the indices were equal, all degrees of the irregularities of the corneal surface, as well as astigmatism, would be perfectly corrected with the CL. With high degrees of astigmatism, residual astigmatism will be proportionately higher.[14]

Impact on Corneal Nourishment

Contact lens impacts the cornea in numerous ways.

1. Retard the tear evaporation and interfere with tear hypertonicity.
2. Acts as a barrier to the delivery of oxygen
3. Traps the water and reduces waste disposal
4. Injure or traumatize the dead epithelial cells.[15]

The hard CL covers approximately 50-80% of the corneal surface, and 70 to 85% of this area is permanently protected with normal lens mobility. The covered area is dependent on the nutrition of the tear film under the contact lens. The post-lens tear interface needs constant renewal to meet the corneal oxygen demands.[16]

It has been observed that under static conditions, the oxygen in the post-lens tear interface is exhausted within 90 seconds with hard or soft CL with 40% hydration. Further, the non-oxygen dependant pathway is significantly less efficient (approximately 1/18) than the oxygen-dependent pathway. There is an accumulation of lactic acid, the corneal nutrition is compromised, and this is corneal edema and haziness.[13]

The blinking mechanism creates a pump mechanism in the cornea-contact lens interface, and the pressure on the lid presses the contact lens, which expels the post-lens tear interface, which is then formed again. The pump efficacy depends upon

• Tear volume behind the contact lens
• Blink frequency
• Percentage exchange of fluid with each blink[16]

The soft contact lens has a large diameter and comprehensively covers the lens surface. An aqualung effect is seen due to the hydrophilic nature of the lens. When blinking is absent, the corneal surface lacks oxygen, and the pump effect is missing. The oxygen delivery in soft lenses is only 10% of hard CL. But the lens flexibility helps create a capillary layer of fluid under the lens surface. The corneal deturgescence is reduced due to hypotonicity of the tear film resulting from excessive secretion of tears, change in blink rate, and impairment of evaporation.[17]

Lens Edge Effect

The contact lens is covered by the patient's tear film, resulting in a prism-shaped meniscus at the lens edge. If the edge of the lens comes in the pupillary area, it may result in the formation of the second focus of the image on the retina. This is common with low riding as well as high-riding lenses. This is called as ghost image effect or the edge flare effect.[18]

Lens Damage 

The lens spoilage can result from irregular contact lens interactions with the tear film. There can be multiple deposits on the contact lens surface which can affect the lens's optical properties. The deposits can damage the contact lens and reduce its working efficiency within six months. The lens deposits can be due to

• Lens surface irregularities due to manufacturing defects
• Tear film inadequacy
• The porosity of the lens
• Blink irregularity and deficiency
• Immediate tear film break-up time
• Altered tear film composition
• Reduced tear film volume
• Altered pH of the tear film[19]

Issues of Concern

Corneal Complications

Epithelial Complications

Epithelial Edema

Epithelial edema occurs secondary to hypoxia and is usually reversible. It is one of the commonest and earliest corneal complications.[15]

Microcysts

It occurs due to a decrease in corneal metabolism over a long period. They are seen most commonly with soft CL or extended wear contact lenses. These appear as small dots over the cornea of varying density and may mimic Cogan's microcystic dystrophy. These dots clear once the lens is removed. It is advised for these patients to switch from extended wear to daily wear or daily wear to gas-permeable lenses.[20]

Abrasions

These are caused by trauma or mechanical injury due to the lens or while insertion or removal of the lens. A foreign body embedded in the lens can also induce corneal abrasions.[21] The patients usually present with pain, redness, and watering, and the abrasions can be delineated on staining. The best treatment is contact lens removal and a course of topical antibiotics. Patching should be avoided in these cases due to fear of the eye getting infected. Once the infection resolves, contact lens wear can be initiated slowly.[22]

Superficial Punctate Keratitis

Superficial Punctate Keratitis (SPKs) occurs due to mechanical injury from the lens or during lens application.[23] Contact lens-induced chemical toxicity also results in SPK. This occurs secondary to preservatives present in the saline, not being able to clean the lens properly after using surfactant or enzyme cleansers, or failure to clean or neutralize hydrogen peroxide disinfectants.[24]

The associated ocular pathologies like dry eyes and blepharitis can also cause SPKs. Patients with SPK have to stop the lenses until the lesions resolve. The topical antibiotics, lubricating eye drops, and ointments also promote healing. The patient should be reassessed before deciding on CL wear again.[25]

Staining at 3 and 9 o Clock

This occurs due to corneal desiccation because of interruption of tear film or reduction of tear film at the nasal and temporal limbus. The main risk factors are poor lens edge tilt, limited lens movement, low riding lens, poor blink rate, presence of pinguecula, and adherence to the lens surface. It occurs most commonly in RGP lenses.[26]

Sterile Infiltrates

These are due to an inflammatory response to a particular antigen with associated corneal leucocyte infiltration from the adjacent limbal vessels.[27] The preservatives present in the contact lens cleaning solution are implicated as the major source of antigens. These appear as small opacities, which can be epithelial, subepithelial, or anterior stroma.[24] These infiltrate do not cause any symptoms and are detected on a routine examination. In some cases, a corneal infiltrate is an early indicator of microbial keratitis. The infiltrate disappears once the contact lens is discontinued. Once the infiltrate resolves, the patient can start wearing the CL with a preservative-free saline solution.[28]

Peripheral Corneal Ulceration

These ulcers are characterized by epithelial infiltration with an intact Bowman layer. The clinical presentation is different from that of microbial keratitis.[29] The peripheral corneal ulcers involve the paralimbal area and are white, crescentic to oval excavated ulcers and may be associated with thinning. There is mild congestion and focal infiltrates in contrast to microbial keratitis, which usually affects the visual axis and is characterized by epithelial defect and stromal melt. Peripheral corneal ulceration is also called marginal keratitis, and the primary causative agent is staphylococcal toxins.[30]

Corneal Neovascularization

This results from excessive hypoxia due to prolonged lens wear or a tight or thicker lens. Neovascularization can be superficial, deep, sectoral, or involve 360 degrees of the cornea.[4] In extended wear contact or therapeutic CL, a small amount of peripheral superficial vascularization is common (1 to 2 mm). A growth having a progression of more than 2 mm or involving a middle or deeper stroma is not common. Careful fitting of CL, regular follow-up of patients, and use of high oxygen transmission lenses with discontinuation of older ones is the treatment for neovascularization.[31]

Microbial (Infective) Keratitis

This is also known as contact lens-induced keratitis (CLIK). It is one of the serious complications but not a very common complication of contact lens wear. It may occur with any type of contact lens wear but is more common with soft CL and more familiar with extended wear CL.[4]

It starts with an epithelial defect secondary to trauma or hypoxic associated with microbial contamination. The significant risk factors are poor personal hygiene, inadequate lens cleaning, contamination of lens cover or lens cleaning solution, and the presence of dry eyes and blepharitis. The common organisms involved are Pseudomonas aeruginosa and Acanthamoeba. The other microorganisms, such as gram-negative and gram-positive bacteria, can also cause CL-induced keratitis.[4]

Acanthamoeba Castellani Infection

This condition is more common in patients using homemade saline for lenses, swimming in a swimming pool with CL, swimming in contaminated water, and exposure to tub and tap water. The most common clinical features are a pain out of proportion to clinical findings, irregularity of epithelium, and patchy stromal infiltrate.[32]

The late clinical features include stromal infiltrate, radial keratoneuritis, and elevated linear epithelial lines. Precautions must be taken to prevent this problem in patients. Prolonged lens wear, primarily sleeping with CL on, is a significant risk factor for acanthamoeba keratitis. Good ocular hygiene with regular cleaning and disinfection are the critical factors in preventing corneal ulcers in these patients. The patient should be explained in detail the risk factors and warning signs of corneal infection to avoid this ocular catastrophe. Once the corneal ulcer has occurred, it should be dealt with very early and meticulously.[33]

Pseudomonas Aeruginosa Keratitis

Pseudomonas is the most common cause of microbial keratitis in patients using CL. The patient usually presents with pain, redness, and discharge out of proportion and size of the infiltrate. The clinical findings are the presence of corneal infiltrate, ring infiltrates, and the presence of hypopyon in advanced cases.[34]

Fungal Keratitis 

Another sight-threatening complication associated with CL is fungal keratitis, characterized by dense gray-white stromal infiltrate, feathery margins, satellite lesions, endothelial exudate, and hypopyon. The diagnosis is by the corneal scraping of the infiltrate, and smearing and culture will pinpoint the microorganism.[35] The incidence of fungal keratitis secondary to CL wear varies from 10 to 21%. The most common causative agents are Aspergillus, Fusarium, and Candida. CL wear is the major cause of yeast-like fungal keratitis.[36]

Extended-wear lenses are associated with an increased risk of CL keratitis, followed by hydrogel and rigid gas-permeable contact lenses. Trauma with vegetative matter is the major cause, and topical antifungals are the mainstay of treatment. The commonly used antifungals are 5% Natamycin, 0.3% Amphotericin B, 1% voriconazole, 1% Itraconazole, and 1% Itraconazole. Non-resolving cases will require therapeutic keratoplasty.[4]

Warpage

Prolonged contact lens wear can induce severe and permanent astigmatism in the eyes in response to chronic hypoxia. The corneal shape changes temporarily due to prolonged use of impermeable hard CL. The warpage is usually detected on corneal topography and reverses with the discontinuation of CL. It can also cause a temporary reduction in visual acuity.[37]

The other complications with contact lenses can be foreign body tract formation, corneal Dellen, vacuoles, mucin ball formation, and dimple veiling.

Corneal Endothelial Changes

Contact lens wearers can have both short-term and long-term endothelial changes. The endothelial changes are thought to occur secondary to hypoxia which causes lactic acid accumulation in the cornea,  elevated levels of carbon dioxide, and reduced pH.[38]

Two types of changes are seen clinically

Endothelial bleb response

This is thought to occur minutes after using a thick, soft, or rigid contact lens. This is a transient effect and doesn't produce other side effects. The bleb changes usually resolve after 30 minutes of lens application or rapidly after lens discontinuation.[13]

Endothelial Polymegathism and Pleomorphism

These changes are noticed after a long time of contact lens wear. These changes are associated with corneal decompensation following intraocular surgery. These changes can be reduced by promoting the use of daily wear CL over extended-wear lenses and the use of RGP lenses over rigid PMMA lenses.[39]

Contact Lens-Related Discomfort

Per the Tear Film and Ocular Surface Society, discomfort associated with CL is characterized by occasional or regular adverse eye sensations associated with lens application, which may or may not be associated with visual discomfort, secondary to reduced harmony between the CL and surrounding ocular surface environment.[40]

This results in reduced usage or discontinuation of CL. The CL factors associated with discomfort are lens material, design, wearing time, hygiene, and fit to the ocular surface. The environmental factors are ocular surface changes, occupation, external temperature, humidity, associated medication use, and compliance. The goal of management is to reduce patient discomfort and modify the associated factors to provide a comfortable daily wear time.[4]

Conjunctival Complications

Allergic Conjunctivitis

This common complication has been reported with thiomersal-containing solutions. The patient presents with pain, redness, itching, and burning sensations. The reaction usually develops after days to months following exposure to thiomersal.[23] The examination reveals conjunctival hyperemia and the papillary response of the conjunctiva. Avoidance of thiomersal is the best treatment, and steroid eye drops should be used in tapering doses to prevent this reaction.[41]

Giant Papillary Conjunctivitis

This is an immunological complication in which the contact lens deposits and proteins act as an allergic stimulus.[23] The main risk factors for GPC include patient susceptibility, contact lens wear schedule, contact lens care regimen, lens material, and design. GPC is known to occur more commonly after soft CL. Patients with asthma, hay fever, and animal allergy are more susceptible.[4]

The most common symptoms are itching, redness, increased mucus production, photophobia, irritation, and reduction in lens tolerance. The upper palpebral conjunctiva show giant cobblestone papillae.[42] The GPC can be reduced by avoiding contact lens use, regular use of enzyme cleanser, change of lenses, avoiding heat disinfectants, and avoiding the use of CL with CL on. The lens should be avoided for at least 1 to 2 months, and treating the patients with sodium cromoglycate and steroid eye drops. Once the condition subsides, newer lenses may be fitted to avoid the recurrence.[43]

Superior Limbic Keratoconjunctivitis

Superior limbic keratoconjunctivitis is a hypersensitivity reaction to thiomersal or preservatives in contact lens solution. SLK is usually bilateral and asymmetric.[44]

The patients typically present with pain, redness, foreign body sensation, and contact lens intolerance. The anterior segment findings usually reveal inflammation and hypertrophy of superior bulbar conjunctiva that stain with Rose Bengal stain, punctate epithelial erosions, microphones of the superior cornea, and papillary hypertrophy of superior tarsal conjunctiva. The CL should be discontinued, and lubricating eyedrops should be used frequently. When the pathology resolves, the patient should be given a new pair of contact lenses and must be advised to use non-preserved saline and perform frequent lens cleaning.[44]

Clinical Significance

Contact lens-related problems and complications cause significant physical and mental trauma to the patient. It is a considerable economic burden for society. If not managed on time, these can result in a loss of visual acuity.[4] Every patient being prescribed contact lenses should be explained in detail the contact lens material properties, fitting technique, maintaining ocular hygiene, lens hygiene, and how to use and clean lenses to prevent the ill effects of the lens.[4]

The patients should receive explanations regarding the types of lenses available in the market and the pro and cons associated with each type of lens.[2] 

Other Issues

Complications Associated With Contact Lens

Contact lenses can be damaged or spoiled by use over time and may create various problems. There can be physical damage to the lens, change in lens color, loss of lens, and deposits over the lens.[45]

Physical Damage to the Lens

Damage to the lens can occur in the form of lens breakage, chipping, and cracking while inserting or removing the lens. The biochemical degradation of the lens also causes physical damage to the lens.[4]

Lens Discoloration

This can occur due to systemic uses of drugs such as rifampicin, fluorescein, and phenylephrine.[46]

Loss of Lens

This occurs more commonly in the pediatric age group than in adults. Most widely reported with rigid lenses than soft lenses and more familiar with extended wear lenses than daily wear.[47]

Deposits over Lens

This is another common problem with CL. This is more commonly reported with extended wear, daily-wear soft, RGP, and hard lenses. The deposits can be from the tear film, lens handling, cosmetics, topical drugs, and pollutants like dust and fumes.[20] The lens deposits occur secondary to a lack of personal hygiene, lens surface defects, age-related changes, material decay, and local ocular pathologies like blepharitis, meibomitis, lagophthalmos, and dry eyes.[25]

The lens deposits can be proteinaceous as well as lipid-laden deposits. These can cause physical damage to the lens, physiological impairment of diffusion of gases, blurred vision, hazy vision, halos, distortion, polyopia, photophobia, aberrations, and astigmatism. The treatment is that lenses should be replaced when the deposits are clinically significant. The daily-wear lenses should be replaced after every six months.[48]

Enhancing Healthcare Team Outcomes

Avoiding problems and complications with contact lenses is of prime importance for the patient and the treating surgeon. While prescribing CL to a patient, the treating surgeon must weigh the risk and benefits for a particular patient based on the primary indication.[49]

The patient undergoes refraction by an optometrist; the nursing and the allied staff help in patient recruitment, follow-up, and counseling, the treating surgeon, decides the type of contact lens; and the contact lens specialists and paramedical staff help in lens fit and counseling. Hence, this multidisciplinary approach help in patient management with a good outcome.[50]

Nursing, Allied Health, and Interprofessional Team Interventions

The nursing staff, allied health professionals, and the interprofessional team play a key role in deciding the type of contact lens, comfort with the contact lens, a preliminary diagnosis of any complications associated with the contact lens, and patient management with regular follow-up.[51]

Nursing, Allied Health, and Interprofessional Team Monitoring

The nursing staff, allied health professionals, and the interprofessional team play a key role in monitoring the patients who are regular contact lens wearers and determining any problems associated with the regular use of contact lenses.[52]