By Damon Ezekiel
BOptom BSC FAAO FCLSA
The management available to correct keratoconus is varied, with speciality lenses including soft keratoconus, hybrid, piggyback, corneal, miniscleral and scleral, and patients need to understand the pros and cons of each option.
Fitting a gas permeable lens to an already compromised keratoconic eye is the optimal long-term outcome. If possible, I will fit my patients with a corneal GP trial lens and show them the vast improvement in visual acuity and how this will translate into a huge improvement in quality of life.
CA, a 21-year-old male, was first diagnosed with keratoconus at the age of 18 years. He consulted me three years later, after struggling with spectacles and obtaining visual acuities of R 6/60 (pinhole 6/9-) and L 6/18 (pinhole 6/9). Corneal topography showed his keratoconus was mild (Figures 1 and 2).
Figure 1. Topography
Figure 2. Topography
I trial fitted CA with a pair of corneal GP contact lenses of parameters:
R 7.65/9.80/-0.75 L 7.75/9.80/+0.25
Aspheric Gelflex design BXO blue
These improved his visual acuities to R 6/6 and L 6/6.
At the delivery consultation, CA was obtaining visual acuities of 6/6 OU. He managed the contact lens handling and Boston solutions cleaning regime well.
At his first after-care visit, CA was obtaining a wearing time of eight hours per day with excellent vision and was encouraged to increase to all-day wearing. However, at his annual review a few years after first being fitted, CA walked in wearing his spectacles as he could no longer tolerate the lenses.
We explored other avenues and I trial fitted CA with the new miniscleral lenses from Gelflex Laboratories, the SoClear lenses.
SoClear is a miniscleral contact lens that provides superb initial comfort and rapid adaptation times. The lens shows smaller movement on blink than a corneal GP lens and sits comfortably under the patient’s lid, reducing lid interaction and improving lens comfort. SoClear lenses enable correction of significant regular and irregular astigmatism without the need for complex toric designs.
These lenses are manufactured from Boston XO2, a gas permeable material with high oxygen transmittance for ocular health and good stability. Its highly wettable surface sustains wearer comfort for long periods and reduces the dryness sensations often associated with soft lens wear. SoClear lenses are also plasma treated to further enhance wettability and all-day comfort.
I trial fitted CA with a pair of SoClear Aspheric/Cone lenses. I looked for a central corneal clearance of approximately 400 µm, as these lenses will settle with wearing. I then performed an over refraction and evaluated the obtainable visual acuity.
I evaluated the mid-peripheral fit of the trial lens, looking for a landing area of the lens on the sclera of approximately 1800 µm or clearance from just inside the limbus to clearance 2 mm beyond the limbus onto the sclera.
In CA’s case I trialled a:
R 6.49/14.50/-8.00 Aspheric/Cone over Rx -1.00sphere 6/6
Central clearance 368 µm (Figure 3), landing zone 1312 µm (Figure 4)
L 6.49/14.50/-6.00 Aspheric/Cone over Rx +0.50sphere 6/6
Central clearance 394 µm, landing zone 1304 µm
CA obtained a visual acuity of 6/6 OU.
Figure 3. Central clearance
|Figure 4. Landing zone area
It was important for CA to have had his lenses in for four to six hours before the first after-care consultation. I generally find the lenses have dropped back onto the eye with a central corneal clearance of approximately 200-300 µm.
At CA’s first after-care, the central corneal clearance was:
R 194 µm, landing zone 1262 µm
L 140 µm, landing zone 2222 µm
Over Rx was OD Plano 6/7.5+, OS -0.75 6/7.5+
Both lenses had dropped back too much onto CA’s corneas. The fit was now too tight and removal towards the end of eight hours of wear was difficult.
I asked CA to cease wearing the lenses and to make another appointment to be refitted with steeper SoClear trial lenses. He was refitted with these lenses:
R 6.14/14.50/-11.00 Aspheric/Cone over Rx -2.00sphere 6/6
Central clearance 429 µm, landing zone 2075 µm
L 6.25/14.50/-10.00 Aspheric/Cone over Rx -0.50sphere 6/6
Central clearance 400 µm, landing zone was 2222 µm
CA was delivered a pair of SoClear Mini Sclerals with the following parameters:
R 6.14/14.50/-13.00 Aspheric/Cone
L 6.25/14.50/-10.50 Aspheric/Cone
At CA’s visit a week after collecting his lenses, he was wearing them for nine hours a day and achieving visual acuities of OD 6/6, OS 6/6 and 6/6 OU.
R central clearance 331 µm, landing zone 2075 µm
L central clearance 279 µm, landing zone 2222 µm
The SoClear miniscleral is not difficult to fit but it will take some time for the patient to master the lens handling.
Insertion of this lens is with preservative free saline and the lens cannot be worn with an air bubble. If on insertion there is a bubble of any size, the lens needs to be removed and reinserted. I teach my patients lens removal by using their fingers, which is preferable to using a suction cup.
CA is now wearing his SoClear contact lenses for most of the day and enjoying the quality of his vision and enhanced quality of life.
Damon Ezekiel owns a specialist contact lens and general optometry practice, Ezekiel Eyes, in Perth WA. He is a consultant to research organisations including Gelflex Laboratories.