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All lenses great and small

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Damon J Ezekiel
BOptom FAAO FCLSA FSLS
Director, Ezekiel Eyes, WA

 

My philosophy for fitting keratoconus patients is to work through the options with them. The various options range from soft toric contact lenses, piggy-back soft lenses with corneal RGPs, and corneal RGPs, to gas permeable mini-scleral and gas permeable scleral contact lenses.

The range of options available depends on the severity of the patient’s cone. Ultimately, this will determine the path that will give the patient the best visual acuity improvement.

CASE REPORT

 

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Figure 1. Corneal topography map reveals the extent of PC’s keratoconus, right eye

 

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Figure 2. Corneal topography map reveals the extent of PC’s keratoconus, left eye

 

PC, a 30-year-old patient, presented to my office concerned about his quality of life. He had been diagnosed with keratoconus when he was 22 years old and he admitted his vision had been poor for a few years before the diagnosis.

PC was only just managing with the spectacle prescription: R Plano/-5.25 x 45, VA 6/48; L -0.50/-1.75 x 100, VA 6/9.5. His Flat and Steep K readings were R 49.36/54.96 and L 46.40/48.47.

PC worried whether he would be able to continue to hold down a job and drive, which are aspects of life that most of us take for granted. He was at a crossroad in his life, as his lack of vision was becoming a liability for him as well as for other road users.

In discussions with PC, it emerged that he had tried only soft disposable toric contact lenses, which were not satisfactory due to very poor visual acuities and comfort. We decided to start with corneal gas permeable contact lenses.

I trial-fitted PC with the Keracon lens in a 9.6 diameter. After a few trial fittings to establish a good three-point touch fit, PC’s visual acuities improved to R 6/7.5- and L 6/6-.

At the first aftercare consultation review, PC was wearing the lenses full time with great vision and reasonable comfort. No contact lens adjustments were required; another review was scheduled for two weeks later.

At the following aftercare consultation, PC informed me that he had been to his work site north of Perth and been surrounded by dust, heat and wind. His comfort was a real issue. The fit of the lens in my clean, cool consulting room was great and the vision was good.

The next option we discussed was to move PC into a gas permeable mini-scleral lens. He returned the following day with no lens wear and we undertook the trial fitting of the gas permeable SoClear mini-scleral lenses.

The gas permeable SoClear mini-scleral lens is made by Dakota Sciences in the USA, and Gelflex Laboratories is the agent for these lenses. It is a sealed design, nice and thin, made in the Boston XO2 material, and I find that it is a terrific lens for my patients.

After a few trial lenses to establish the correct fitting, I decided on the following lens parameters: R 5.19/15.00/-19.50, L 5.27/15.00/-19.50.

 

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Figure 3. Right eye central fit

 

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Figure 4. Left eye central fit

 

Figures 3 and 4 show the central corneal tear layer at delivery of R 410 µm and L 442 µm. We aim for a central corneal tear layer of around 400 µm; with increased wearing time this central tear layer will drop to approximately 200 µm. A small central tear layer initially will become too tight as the lens drops onto the cornea. With increased wearing time, this will cause corneal staining. An excessively large corneal tear layer will cause dimple veiling and compromise the corneal health; vision will be poor as the lens will not drop back on the eye.

The landing zone of the SoClear lens is to fit the periphery of the lens on the sclera and clear the limbus. We measure this landing zone with our anterior OCT. A landing zone of approximately 1500 µm is great. If the landing zone is too small, the lens will become too tight and if the landing zone is too large, the bearing of the lens will encroach across the limbus and compromise the fit and lens comfort. In this case it was R 1560 µm and L 1474 µm as shown in Figures 5 and 6.

 

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Figure 5. Right eye landing zone

 

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Figure 6. Left eye landing zone

 

During PC’s next aftercare consultation, he was achieving wearing his lenses with comfortable all day wear and achieving visual acuities of R 6/7.5 and L 6/6.

PC was very happy that his visual acuities and overall quality of life had greatly improved. He appreciated the effort of trying a modality of contact lenses and then moving on to the next level to enhance either the vision or the comfort.

______________________________

Damon Ezekiel is the Practising Fellow of the Scleral Lens Education Society in Australia. In 2018, he will be the first Australian to become president of the International Society of Contact Lens Specialists.



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