By Marissa Megaloconomos
BAppSci(Optom) GradCert(Ocular Therapeutics) Specialist Cert (Management of Contact Lens Patients) FBCLA CASA CO
A 28-year-old Caucasian female presented for her first consultation in more than two years to renew her contact lens prescription. She had been diagnosed in her teenage years with Horner syndrome affecting the right eye as a result of trauma, but had been a successful wearer of monthly disposable hydrogel lenses since she was 19 years old. General health was otherwise unremarkable and she was not taking medication.
Initial discussion revealed the patient had been wearing the same pair of lenses every day for the past four months as an extended wear schedule and she removed them only once a fortnight or so for a ‘quick rinse’ with multipurpose solution. The contact lenses she was wearing had a water content of 66 per cent and oxygen transmission (Dk/t) of 16 at -3.00 D.
Visual acuity with her contact lenses was R 6/7.5- and L 6/6- with no improvement following subjective refraction. As expected with Horner syndrome, she had a mild ptosis of the right superior eyelid (interpalpebral aperture 8.5 mm compared to 10 mm in the left eye) and miotic pupil;1 however, both pupils reacted efficiently to stimulus.
Contact lens assessment revealed a tight fit with no movement of the right lens on blink and minimal movement of the left lens. Both lenses displayed a very sluggish return on push-up test.
Slitlamp examination revealed neovascularisation of the right superior cornea (Figure 1) with surrounding oedema and grade 3.5 punctate epithelial erosions across the central and superior cornea suggestive of corneal hypoxia.2,3 The left cornea had diffuse grade 1.5 punctate epithelial erosions across the central cornea only. The patient was found to have a tear film deficiency with inadequate tear volume as determined by a Schirmer test.
Figure 1. Neovascularisation of the right superior cornea at initial presentation
The patient was initially managed with non-preserved lubricants every two hours and instructed to cease lens wear until the next review. Two weeks later, the patient reported significant improvement in comfort since ceasing lens wear but significant oedema and epithelial staining were observed and best-corrected visual acuity remained at R 6/7.5 and L 6/6.
The patient was treated with a tapered course of fluorometholone (0.1%) in the right eye and advised to continue the ocular lubricants regularly. Contact lens wear was discontinued until the ocular surface improved and after one month, visual acuity had improved to 6/4.5 in both eyes. After three months, the patient was refitted with silicone hydrogel daily disposable lenses for part-time wear.
There are many considerations when selecting a contact lens for a patient, including but not limited to the patient’s ocular surface integrity and tear film quality, systemic health conditions, compliance and wearing schedule.
Because contact lenses are defined as a ‘medical device’, it is our responsibility as the prescribing practitioner to ensure any item we recommend or prescribe is both safe and effective.
For this patient, factors that needed to be considered when providing a new contact lens prescription included the tear film deficiency, lid ptosis and compliance.
A study performed in 1999 found the minimum Dk/t for oxygen delivery to prevent anoxia throughout the entire corneal thickness in a closed eye was 125.4 Given compliance is a continual struggle with many patients, should we be prescribing only lenses with a Dk/t of at least 125 in case the patient sleeps in the lenses?
- van der Wiel HL, van Gijn J. The diagnosis of Horner’s syndrome. Clin Neurol Neurosurg 1988; 90: 2: 103-108.
- Sweeney DF. Clinical signs of hypoxia with high-Dk soft lens extended wear: Is the cornea convinced? Eye Contact Lens 2003; 29 (IS): S22-S25.
- Efron N. Contact Lens Complications: 3rd ed. 2012. Edinburgh: Elsevier Saunders.
- Harvitt DM, Bonanno JA. Re-evaluation of the oxygen diffusion model for predicting minimum contact lens Dk/t values needed to avoid corneal anoxia. Optom Vis Sci 1999; 76: 10: 712-719.