Contact lenses offer a convenient and often preferred alternative to spectacles for vision correction. However, successful contact lens fitting and complications management are crucial for patient comfort and eye health. This guide will provide a comprehensive overview for students, covering patient selection, fitting procedures, and common issues encountered with both soft and rigid gas permeable (RGP) lenses.

Understanding Contact Lens Fitting and Complications

Proper contact lens fitting goes beyond simply matching a prescription. It involves a thorough evaluation of the patient's eyes, lifestyle, and visual needs to ensure optimal comfort, vision, and long-term ocular health. Addressing potential complications proactively is equally important.

Patient Selection and Evaluation for Contact Lenses

Careful patient selection is paramount for successful contact lens wear. A detailed history and evaluation help identify suitable candidates and potential challenges.

Key Considerations in Patient Selection

History: Past medications, previous surgeries (e.g., cosmetic lid surgery affecting RGP bifocal positioning).
Patient Goals and Motivation: Crucial for managing expectations, especially for presbyopic corrections.
Visual and Occupational Requirements: Lifestyle, mode of employment, and specific visual demands.
Tear Film Stability: Tears naturally decrease with age. A TBUT (Tear Break-Up Time) of less than 5 seconds may contraindicate lens wear. Schirmer or Phenol Red tests assess tear quantity.
Anatomic Measurements: Palpebral aperture (low lower lid can cause issues with translating bifocals), pupil diameter (large pupils may experience "ghosting").
Corneal Health: Pinguecula or pterygium, loss of endothelial cells (making the cornea susceptible to edema), and crystalline lens changes are more common in older eyes.

Presbyopia: Patient Consultation and Expectation Management

Fitting presbyopic patients with bifocal contact lenses requires careful consultation. Patients must have appropriate and realistic expectations about visual quality.

Motivation: Highly motivated patients often have better outcomes.
Education: Informing patients about the expected levels of visual quality helps develop optimism and realism.
Expectation Setting: A good approach is to aim for clear vision for at least 85% of their normal visual needs. Patients accustomed to perfect 20/20 vision with glasses and concerned about compromise may not be the best candidates. Some patients will accept reasonable compromise for the benefits of contact lens wear, aiming for "20/happy" instead of 20/20.
Refraction: Best candidates typically require > 1.00D of hyperopia or > 1.25D of myopia. Low hyperopes often expect better vision with bifocals. Low myopes can be difficult as they see well at near without correction. Amblyopia or monocularity are generally contraindications.

Contact Lens Correction Options for Presbyopia

Several contact lens modalities exist to correct presbyopia, offering visual freedom and binocularity.

Types of Bifocal Contact Lenses

Simultaneous Vision: Both distance and near prescriptions are present simultaneously across the lens. These can be soft or rigid.
Aspheric Designs: Pupil-dependent, with the pupil constricting for near tasks and dilating for distance. Must be well-centered.
Back Aspheric: Offers clear distance vision with limited reading power.
Front Aspheric: Allows higher reading power, potentially compromising distance clarity. Most designs are front aspheric.
Examples: Air Optix Multifocal (Alcon), Proclear Multifocal & Biofinity (CooperVision), Acuvue Oasys (Vistakon).
Air Optix Multifocal: A progressive aspheric design, center-near, with add power concentrated centrally. Features 3 add powers (Low, Med, Hi) and a smooth transition zone.
Proclear/Biofinity Multifocal: Monthly replacement, progressive bifocal, visibility tint. Two different lenses: D lens (dominant eye, center distance) and N lens (non-dominant eye, center near).
Translating: Rigid lenses where the lens moves on the eye, allowing the wearer to look through different power zones. Patients with "low" lower lids may have trouble with these.

Other Presbyopic Correction Modalities

Contact Lenses + Reading Glasses: Best vision at distance and near, but requires frequent removal/application of reading glasses.
Monovision: One eye corrected for distance, the other for near. May require supplemental correction for critical vision tasks.
Enhanced Monovision (Air Optix): Fitting the dominant eye with a single vision lens and the non-dominant eye with a bifocal (improves distance acuity), OR fitting the non-dominant eye with a single vision lens for near, decreasing the distance power of the bifocal on the dominant eye (improves near acuity).
Modified Bifocal Approach (Air Optix): Adding plus power to the distance power of the non-dominant eye (improves near acuity), OR adding minus power to the distance power of the dominant eye (improves distance acuity).

Contact Lens Fitting Procedures

Precise fitting techniques are essential for optimal vision and comfort.

Initial Lens Selection and Evaluation (e.g., Proclear/Biofinity)

Subjective Refraction & Add Power: Determine eye dominancy (e.g., using +2.00D in front of each eye).
Initial Trial Lens: Vertex distance Rx, spherical equivalent. Select add power based on patient's add correction (e.g., -4.50-0.75x090 Add +2.00 becomes Trial: -4.50 Med add).
Settling Time: Allow 15-20 minutes for lenses to settle. During this time, the patient can be sent to the reception area.
Binocular Vision Testing: Evaluate distance and near vision under binocular conditions. Never occlude one eye. Use good lighting for near testing. Use hand-held lenses or flipper bars (phoropter influences pupil size).
Refinement: Add +/- 0.25D changes for distance and near to determine lens changes. Differences of 0.25D can have significant effects. Visual quality is often a better indicator of success than visual acuity.
Patient Management (Air Optix Multifocal): Don't over-refine at initial fitting. Discuss expected ghosting of letters, light halos, and starburst effects at night. Dispense lenses for 3-4 days; patients quickly determine satisfaction level.

General Contact Lens Problems and Solutions

Contact lens wearers may experience various issues that require proper diagnosis and management.

General Patient Management Strategies

Lens Wear Schedule: Some patients may need daily disposable lenses for occasional wear.
Rewetting Drops: May be needed regularly.
Lens Care Education: Re-educate patients on proper cleaning and handling.

Rigid Gas Permeable (GP) Lens Problem Solving

GP lenses, while offering excellent vision, can present specific challenges.

Reduced Vision
Flexure: Bending force from the upper lid induces toricity. Causes include steep fitting, reduced center thickness (CT), large optical zone diameter (OZD), and material flexibility.
Diagnosis: Over keratometry shows toricity.
Management: Flatter BCR (at least 0.50D), increase CT by 0.02mm per diopter of corneal astigmatism, reduce OZD (at least 0.3mm), change to lower Dk material.
Warpage: Differs from flexure (warpage is permanent, flexure is immediate). Acquired over time, causing distortion and unpredictable refractive changes. BCR measurement with a radiuscope verifies as toric.
Causes: Excessive digital pressure during cleaning.
Management: Routinely verify BCR, educate patients to clean lenses in the palm of the hand, change to a low Dk material. Once warpage occurs, lens change is required.
Decentration: Can cause corneal desiccation, warpage, poor alignment, and reduced vision.
Inferior: Lens too steep, too heavy, inadequate edge. Management: Flatter BCR for myopes, minimum CT, lenticular designs, lid attachment fit.
Superior: Slight decentration is beneficial. Excessive can cause lens adherence. Management: Steeper BCR, thinner edge designs, increase CT.
Lateral: Most frustrating. Causes include decentered corneal apex, against-the-rule astigmatism. Management: Aspheric designs (e.g., Boston Envision), larger OAD lenses.
Power Change: Increase in minus power with decreased CT. Cause: Abrasive cleaners, forceful digital cleaning. Management: Mild abrasive cleaner, gentle rubbing in palm.
Poor Surface Wettability:
Initial: Manufacturing problem (heat buildup, poor polishing, residual polish). Diagnosis: Breakup of tear film on lens surface. Management: Pre-soak lenses 24 hours, use laboratory cleaner/solvent, re-condition with wetting solution, light polish (rarely needed).
Acquired: Muco-protein film/haze. Causes: Poor tear quality, improper blinking, inadequate compliance, improper solution use. Management: Daily surfactant/abrasive cleaners, daily liquid enzymatic cleaner, rewetting drops, re-educate patient, change materials.
Corneal Desiccation
3 and 9 O'Clock Staining: Drying of peripheral cornea, common in >50% of GP wearers. Can lead to thinning, ulceration, neovascularization. Causes: Lens material, centration, edge clearance, tear film stability.
Management: Improve tear film over lens (low Dk materials, FS/A), improve lens centration (lid attachment fit, superior lens-to-cornea relationship).
Vascularized Limbal Keratitis (VLK): Acute corneal desiccation complication, common in rigid extended wear or long-term S/A lens wearers with steep fits (peripheral seal-off).
Management: Discontinue lens wear, antibiotic steroid q.i.d., re-evaluate in 24 hours, taper medication in 4-5 days. Change lens material (if S/A) or flatten peripheral curve system.
Edge Clearance: Avoid excessively high edge lift to reduce peripheral tear volume. Use tri-curve/tetra-curve designs with peripheral edge width no larger than 0.3mm, radius no flatter than 11.0mm. Use aspheric designs for better alignment.
Tear Film Stability: Patients with low to borderline TBUT (5-9 seconds) may experience desiccation. Management: Rewetting drops (hourly), highly wettable materials.
Other GP Complications (PMMA Lenses)
Edematous Corneal Formations: Sub-epithelial dendritic appearance centrally, reflecting low-grade edema. Develops gradually in long-term wearers. Difficult to detect (use indirect illumination).
Polymegethism: Alteration of endothelial cell area, caused by corneal hypoxia.
Central Corneal Clouding (CCC): Circumscribed epithelial edema, grayish haze seen with retro or indirect illumination. Patient has adequate VA with CLs but unsatisfactory with spectacles. Causes spectacle blur, increased myopia, steepening K readings.
Corneal Warpage Syndrome: Distortion and unpredictable keratometric/refractive changes due to prolonged corneal edema (up to 30% of PMMA wearers). Causes keratoconus-like changes, irregular astigmatism, reduced VA. Often reversible but difficult to refit.

Hydrogel Lens Problem Solving

Hydrogel lenses are popular but can lead to specific complications, often reduced with disposable lenses and proper compliance.

Reduced Vision
Contact Lens Associated:
Lens Deposits: Muco-proteinaceous film, lipid-calcium complexes ("jelly bumps"). Causes "foggy" or "hazy" vision. Diagnosis: In vivo biomicroscope evaluation. Management: Enzymatic cleaner (2-3 successive cleanings for moderate deposits), rubbing after soaking, replace lenses for "jelly bumps," refit with disposables if frequent spoilage.
Incorrect Prescription: Verify lens power at dispensing. Perform over-refraction (OR). Could be uncorrected refractive astigmatism (patient understands why monocular vision is worse), toric lens rotation (more problematic with high cylinders/oblique astigmatism). Use pinhole to rule out pathology.
Inverted Lens: Common complaint, especially with new/thin lens wearers. May cause mild irritation and increased movement. Diagnosis: Slit lamp for edge lift, "taco test." Management: Re-educate, try lenses with inversion marks (Acuvue, Fresh Look). Removal and correction improve vision and irritation.
Uncorrected Refractive Error/Flare/Defective Lens Material/Improper Fitting/Excessive Tearing: Problem-oriented case history (onset, duration, present with spectacles).
Both Contact Lenses & Spectacles: Could indicate corneal abnormalities (edema, abrasion, punctate keratitis, infectious keratitis) or intraocular abnormalities.
Discomfort
Defective Lenses: Abrasions, tears, scratches, nicks, holes. Causes irritation, discomfort, reduced VA. If monocular, switch lens to fellow eye; if discomfort follows, replace lens. If not, find another cause.
Upon Insertion: Torn lens (examine edge/surface), solution sensitivity (stinging/burning, improves with lens removal), prism ballast in toric lenses (makes lens thicker).
After Removal: Origin typically the cornea. If discomfort continues, it's an ocular emergency (corneal abrasion, infection, ulcer). Fluorescein evaluation.
Constant Discomfort: Tight lens (compression ring), corneal edema/related symptoms (blur, myopic creep). Management: Flatter BC, smaller diameter, higher O2 transmission materials, replace deposited lens, address excessive movement.
Sudden After Lens Wear: Trapped foreign body (dust, cosmetics). Management: Remove lens, rinse eye. Deposited lens ("jelly bumps"), discomfort increases with wear. Torn lens (edge nicking not touching cornea).
Photophobia: Often used loosely for irritation. Causes: Epithelial abrasions (mild irritation, may go unnoticed), deeper abrasions (severe pain, lacrimation, blepharospasm, photophobia). Check for discharge (mucopurulent, watery, stringy) and lens defects.
Treatment (Superficial Abrasion): Lens removal, heals within 24 hours. Antibiotic usually not warranted unless poor hygiene/compliance.
Treatment (Deeper Abrasion): More aggressive, lens removal, antibiotics if infection risk.
Excessive Lens Movement: Causes: Deposited lens (refit with disposables), inverted lens (re-educate), flat lens (change to steeper BC or larger OAD), inferior lens decentration, corneal exposure on movement, edge lift.
Dryness: Causes: Poor tear quality/quantity, pregnancy, incomplete blink.

Other Complications and Management

Poor patient compliance with lens care systems can induce many hydrogel complications.

Medications & Environment: These can impact lens comfort and wear time.
Computer Use: Prolonged computer use reduces blink rate, contributing to dryness.
Refitting: For complex issues like corneal desiccation, refitting may be necessary.
Verification of New Lenses: Always evaluate new lenses on the patient's eye at dispensing to detect uncorrected prescriptions, visible defects, and discomfort. Educate patients on symptoms of defective lenses.

Frequently Asked Questions about Contact Lens Fitting

What are the main steps in a contact lens fitting process?

The main steps involve patient selection and evaluation (history, goals, visual needs, eye health), trial lens selection based on refraction, allowing settling time, binocular vision testing (distance and near), and refinement of the prescription. Patient education and expectation management are integral throughout the process.

How can I tell if my contact lens is inverted?

An inverted contact lens often causes mild irritation, discomfort, and reduced vision due to increased movement and a poor fit. You can typically identify it by placing the lens on your fingertip; if the edges flare out like a soup bowl, it's inverted. If it forms a smooth, perfect cup, it's correctly oriented. Some lenses have inversion marks.

What causes reduced vision with contact lenses, and how is it managed?

Reduced vision can stem from numerous causes. For GP lenses, it could be flexure, warpage, decentration, power changes, or poor surface wettability. For hydrogel lenses, causes include lens deposits, an incorrect prescription, an inverted lens, uncorrected astigmatism, or defective lens material. Management depends entirely on the cause, ranging from lens replacement, parameter adjustments, re-education on cleaning, to addressing underlying ocular conditions. Always consult your eye care professional for diagnosis and treatment.

Contact Lens Fitting and Complications