March 2009

Cloverleaf Pattern Reveals Surgical History

History and Chief Complaint

A 75-year-old woman was referred to our office by her refractive surgeon for a contact lens evaluation. The patient’s chief complaint was unacceptable glare and photophobia from her right eye while driving at night. She described the glare as bright starbursts surrounding lights, such as headlights and street lamps. The surgeon had determined the patient was not a good candidate for a LASIK touch-up.

The patient’s ocular history was remarkable for radial keratotomy (RK) OD 10 years ago and LASIK OD 1 year ago. She had been wearing eyeglasses for the past year to correct her distance and near vision; however, this did not alleviate her symptoms of glare. The patient reported she did not experience glare when viewing monocularly with her left eye. She also reported that when uncorrected, she would sometimes use her left eye to read.

The patient’s medical history was significant for hypothyroidism, for which she was taking levothyroxine (Synthroid, Abbott Laboratories), and depression, for which she was taking clonazepam (Klonopin, Roche Laboratories).

Clinical Evaluation

Initial examination revealed best-corrected visual acuities of 20/40 OD and 20/20 OS through the following subjective refraction: pl –0.75 x 180 OD and –0.50 –1.25 x 090 OS. Four RK scars and one circumlimbal LASIK scar were noted OD. All other biomicroscopy findings were unremarkable.

Topography of the right eye revealed four discrete areas of flattening in the midperiphery of the cornea. To correct the vision and address the complaints of glare, a Dyna Intra-Limbal GP spherical contact lens (Lens Dynamics Inc.) was prescribed for the right eye. The parameters were as follows:

Base curve 7.88 mm (42.87D)
Power –0.50 DS
Overall diameter 10.8 mm
Optic zone diameter 8.9 mm
Peripheral curves (PC) Standard

With the lens in place, visual acuity was 20/25+. An over-refraction of +0.50 –1.00 x 025 improved the patient’s vision to 20/20. Fluorescein pattern evaluation revealed central alignment and four discrete areas of apical touch, similar to the petals of a cloverleaf, in the midperiphery. The edge lift was acceptable, and the lens positioned centrally on the cornea. The left eye was not fitted with a contact lens.

Because the patient habitually wore a progressive spectacle correction, I prescribed distance overcorrection for the spectacle lens of her right eye. The combination of the contact lens and the eyeglasses relieved the symptoms of glare at night.

Follow-up

During the next 7 months, the patient returned to our clinic for follow-up visits with complaints of lens dryness and discomfort, leading to a part-time wear schedule of the GP lens. Fluorescein evaluation revealed the same cloverleaf pattern and adequate tear exchange. The lens was positioned slightly superiorly. We confirmed that the lens edge was causing the discomfort. Polishing and tapering the lens edge provided initial relief; however, the patient returned with complaints of continued discomfort and occasional lens ejection.

Before reordering a new GP lens, we fitted the patient with a silicone hydrogel lens to be worn under the GP lens for a piggyback fit. The silicone hydrogel lens draped well on the cornea with good coverage, centration and movement. We observed no fluting of the lens edge. The GP lens had good movement and tear exchange when fitted over the silicone hydrogel lens. The patient achieved 20/20 visual acuity through the GP and silicone hydrogel lens combination. The patient reported an improvement in comfort, leading to a full-time wear schedule.

Discussion

Patients who have undergone RK or LASIK occasionally present to eyecare practitioners with irregular and thinner-than-normal corneas. This can lead to diurnal fluctuations in refractive error. A well-prescribed GP lens with adequate tear exchange can compensate for this fluctuation and provide stable vision throughout the day. What’s more, corneal irregularities can result in irregular astigmatism, leading to the symptom of starbursts around lights, especially in dark environments. It is important to maintain corneal health, as RK incisions are susceptible to neovascularization; therefore, oxygen transmissibility is an important aspect to consider when prescribing contact lenses for these patients. GP lenses can improve visual acuities and visual function in patients with irregular corneas, which is rewarding for patients and eyecare practitioners alike.

By Dawn Lam, MSc, OD, FAAO
Fullerton, Calif.

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