CASE 1-5
Blurry, Uncomfortable Soft Lens
Figure 1-5
History
JC, a 31-year-old Caucasian male, presents for his first soft contact lens progress evaluation. He complains of variable vision and mild lens awareness later in the day. He has built up his wear time to 8 hours per day. He uses the ReNu Multipurpose solution to clean and disinfect his lenses. His ocular and medical histories are unremarkable. He takes no medications and has no allergies.
Symptoms
•Variable vision
•Mild lens awareness later in the day
25
26 Clinical Cases in Contact Lenses
Clinical Findings
• VA with CL:
OD 20/25 OS 20/25+2
• Over-refraction:
OD Plano –0.25 × 090, 20/25 OS +0.25 –0.25 × 090, 20/25+2
•Retinoscopy reflex is distorted inferior centrally OU
•Contact lens parameters: OU Biomedics 55 / 8.6 / 14.2 / –3.50
•Contact lens fit: Central position, 0.5 mm movement on blink, no lag on upgaze, minimal movement on push-up (see Figure 1-5)
•Biomicroscopy: All structures clear and healthy OU
•Keratometry:
OD 43.75 / 44.50 @ 090
OS 44.25 / 44.50 @ 090
• Subjective refraction:
OD –3.50 –0.25 × 090, 20/20 OS –3.25 –0.25 × 090, 20/20
Based on the clinical data, develop your list of differential diagnoses. Then, determine your final diagnosis and develop your treatment plan.
Differential Diagnoses
•Uncorrected astigmatism
•Defective lens optics
•Steep-fitting lens
•Flat-fitting lens
•Dry eye
Diagnosis
Steep-fitting lens
Management
The patient was refit with a lens that has a flatter base curve to improve lens draping and visual acuity:
Biomedics 55 / 8.9 / 14.2 / –3.50 OU
Blurry, Uncomfortable Soft Lens 27
The patient’s visual acuity improved to a sharp 20/20 in each eye. The flatter base curve also increased movement, which resulted in increased comfort throughout the day. He was able to attain a wear time up to 14 hours per day.
Discussion
This patient’s symptoms were created by a soft lens with too steep a base curve. Even though the base curve is much flatter than K, if the peripheral cornea and sclera are flatter than normal, the lens may fit too tightly. Tight fitting lenses may result in poor comfort and vision.1–3 The poor comfort is due to decreased lens movement, which results in poor tear exchange, lens binding, and hypoxia. Over time, these factors can lead to further corneal complications, such as acute red eyes and infiltrates. It is important to detect these problems at early follow-up visits to head off more serious complications. In soft lens wearers, staining with sodium fluorescein is often not done for fear that the lenses will be stained. However, it is an important test that can help detect early tight lens–induced changes. For example, changes that are very difficult or impossible to detect without the aid of fluorescein include limbal compression rings, peripheral corneal staining, and peripheral furrow staining.4 After instillation, fluorescein can be irrigated from the tears with saline solution prior to reinserting the contact lenses. An alternative is to use high-molecular-weight fluorescein, which will not stain soft contact lenses.
Poor vision is sometimes induced by steep soft lenses.1–3 Because the lenses cannot drape the cornea completely, they attempt to vault the cornea, like a steep-fitting rigid contact lens. However, unlike a rigid lens, a soft lens cannot maintain its shape, and it collapses in the center. The result is a distorted central zone that blurs the patient’s vision. Blinking often smooths the soft lens for a short time, during which the patient will observe clearer vision. Diagnostically, you can detect a steep-fitting soft lens by performing over-retinoscopy or over- keratometry.1–3 The retinoscopy reflex will be dark or distorted in the central or inferior-central portion of the pupil, which is caused by the light rays being scattered in the distorted zone. This may clear on vigorous blinking. On over-keratometry, the mires will be slightly blurry but clear following a blink. Either positive test indicates the need for a flatter base curve.
Even if a patient does not complain on follow-up visits, if the lens appears to be fitting too tightly for any of the preceding reasons, it is
28 Clinical Cases in Contact Lenses
important to refit to a flatter base curve to head off future potential tight lens complications.
Clinical Pearls
•Steep-fitting soft lenses may cause discomfort later in the day.
•Steep-fitting soft lenses may cause blurry vision.
•Steep-fitting soft lenses may be detected by retinoscopy or keratometry.
References
1.Mandell RB. Hydrogel lenses with spherical surfaces. In: Mandell RB (ed). Contact Lens Practice, 4th ed. Springfield, IL: Charles C Thomas, 1988:544–550.
2.Gasson A, Lloyd M. Soft (hydrogel) lens fitting. In: Philips AJ, Speedwell L (eds). Contact Lenses, 4th ed. Oxford, England: But- terworth–Heinemann, 1997:379–380.
3.Guillon M. Basic contact lens fitting. In: Ruben M, Guillon M (eds). Contact Lens Practice. London: Chapman and Hall, 1994:599–601.
4.Davis LJ, Lebow KA. Noninfectious corneal staining. In: Silbert JA (ed). Anterior Segment Complications of Contact Lens Wear, 2nd ed. Boston: Butterworth–Heinemann, 2000:82–89.