prescribing for presbyopia
Avoiding Dry Eye Symptoms in Presbyopic Lens Wearers
BY CRAIG W. NORMAN, FCLSA
It's not uncommon for presbyopic contact lens wearers to complain of dry eye symptoms such as end-of-day lens awareness, a gritty sensation, increased blinking, or variable visual acuity. The description of these symptoms prompts us to begin problem solving and to consider changes in lens type, lens material, replacement frequency, lens care, or additional ocular lubricant use.
Perhaps we could have avoided these symptoms by paying more attention to the patient work-up during the presbyopic contact lens fitting process. In our clinic, we use a three-pronged approach in an attempt to identify potential contact lens-induced dry eye patients prior to the multifocal fit or refit.
Obviously, we gather data regarding the types of medications (antihistamines, diuretics, etc.) patients may be using that could influence their tear film. We're also quite interested in any difficulties that may have occurred with previous contact lens wear.
We additionally question patients on potential environmental factors such as air quality at work and home, air travel frequency, and smoking status. We detail their daily tasks such as driving, computer work, reading, etc., to ensure that these tasks are not causing reduced blinking.
Analyzing the quality of the tear film is extremely important in the presbyopic patient contact lens work-up. We look at tear breakup time (TBUT) to ensure that it is equal to or greater than 10 seconds.
Figure 1. Lagophthalmos noted in a pre-presbyopic contact lens fitting work-up.
We also closely evaluate the inferior tear meniscus height, which should be about 0.2mm, while evaluating the amount of debris floating in this area — which should be negligible.
Evaluating fluorescein staining of the cornea is quite helpful. We employ the zonal grading system to distinguish the amount of staining in the center and peripheral areas of the cornea.
Rose bengal stain can also be useful to evaluate dead or devitalized cells and mucus in suspected dry eye patients.
Eyelid examination helps to discern blinking frequency, structural anomalies, and ability to spread tears evenly over the ocular surface.
Blinking frequency is directly related to TBUT. A patient should blink more often than the measured TBUT. For instance, if the patient's normal blink is every eight seconds and his TBUT is 10 seconds, we can feel confident that his tear film will remain stable and will not prematurely evaporate.
We also look closely for lagophthalmos (Figure 1). Incomplete lid closure induces inferior dryness at night, resulting in corneal staining in the hours just after awakening.
During the examination, we also evaluate potential underlying lid disease. Note and treat anterior and posterior (meibomian gland dysfunction) blepharitis before lens wear. Recently, it's been suggested that lens wear may increase incidence of meibomian gland dysfunction, so it's important to document that this wasn't already active before presbyopic lens wear. CLS
Craig Norman is director of the Contact Lens Section at the South Bend Clinic in South Bend, Indiana. He is a fellow of the Contact Lens Society of America and is an advisor to the GP Lens Institute. He is also a consultant to B&L.