Keratoconus and corneal ectasia (post-LASIK) are characterized by progressive thinning and steepening of the cornea.1 The risk factors identified for ectasia and keratoconus include high myopia and low residual stromal bed thickness. Generally, after refractive surgeries, the biomechanical strength of the cornea is compromised, leading to mechanical instability and development of keratectasia.2 The prevalence of corneal ectasia after LASIK is found to be 0.66%.3 Common symptoms experienced by patients with corneal ectasia range from mild impairments, severe vision impairments, and an array of visual symptoms such as glare and ghosting. Various treatment options available include variations of soft contact lenses, rigid gas-permeable lenses, scleral contact lenses, corneal collagen cross-linking procedures, and lamellar keratoplasty well before a penetrating keratoplasty is indicated.1
Scleral lenses are considered a vision-saving device when all other treatment modalities fail.4 A prosthetic replacement of ocular surface ecosystem (PROSE) device is a variation of a modern scleral lens. The advantages of PROSE include visual benefits, ability to reduce visual symptoms, increased wearing hours, and improved quality of life.5–8 This case report details an Indian experience with the PROSE device in a post-LASIK patient with corneal ectasia. It gives an overview of how scleral profile can have an effect on the corneal/contact lens relationship when using a PROSE device.
A 29-year-old man presented with a complaint of decreased vision in the left eye during the last 2 years. His ocular history revealed that he had undergone LASIK 11 years before in both eyes. The patient presented a history of wearing a high myopic correction device soon after the procedure. The symptoms experienced by the patient were diplopia attributable to anisometropia, ocular dryness, and halos.
The patient underwent clinical examination, including keratometry, corneal topography, and refraction, establishing the diagnosis of corneal ectasia. The patient was advised to undergo corneal collagen cross-linkage for the right eye and referred for use of a PROSE device to assess visual improvement in the left eye. The alternative plan for the left eye was to conduct a deep anterior lamellar keratoplasty (DALK). Manifest refraction and keratometry values of the patient on presenting to the clinic were as follows:
Manifest refraction: OD: −4.50/−6.00 @ 15 (20/25, N6); OS: ±/−16.00 @ 120 (20/60, N6).
Keratometry: OD: K1 48.44 D @ 110, K2 45.55 D @ 20; OS: K1 75.90 D @ 82, K2 67.35 D @ 172.
Corneal topography was performed for both eyes (Fig. 1). Unaided visual acuity in the left eye was 20/200 with a best corrected spectacle visual acuity of 20/60. The patient complained of experiencing shadows with spectacles in the right eye. He was comfortable with a conventional gas-permeable contact lens in the right eye. The best corrected visual acuity with a gas-permeable contact lens in the right eye was 20/30. The PROSE device trial was performed in the left eye with the consent of the patient. The sequence of visits and trials performed are documented in the following sections.
The initial PROSE device trial was performed. Because a larger device is better for a scleral fit, lenses of 18.5-, 19.5-, and 20.5-mm diameter were fitted alternatively with different ranges of vault. All the devices showed an improper settling on the sclera and were not stable on the eye. Considering the poor stability of larger-diameter devices in this particular case, smaller-diameter lenses of 16.5- and 5.00-mm vault were then tried. The smaller device was comparatively stable. Fit assessment revealed a just adequate vault with mild scleral impingement nasally and temporally after 3 hours of wear. The best corrected visual acuity was 20/30-with a Snellen chart.
During this visit, a flatter haptic with a similar diameter was tried, expecting to avoid impingement. The fit assessment showed an edge lift at the 6- and 12-o’clock positions and impingement staining nasally and temporally. Two devices were then ordered with a customized design using the CAD-CAM technology. The two devices ordered were of smaller diameter, one with an even flatter spherical haptic and another with a toric haptic (Table 1).
The assessment of the fit with device 1 with a spherical haptic design presented tiny bubbles, edge lift at 6- and 12-o’clock positions, and mild impingement staining observed after 1 hour of wear. Device 1 was deemed unacceptable. Another trial was then performed with device 2. The fit assessment of device 2 revealed an optimal fit with an adequate vault and good haptic with no edge lift and impingement staining or bubbles after 1 hour of device wear. The patient was comfortable wearing the device. After demonstrating insertion, removal, and handling procedures, the patient was advised to report to the clinic after 6 hours of device wear the next day. The patient was instructed to report any symptoms such as discomfort or redness along the edges of the device.
After the consecutive 6 hours of wearing time, the fit assessment revealed a mild edge lift and impingement staining, with no symptoms experienced by the patient. The patient was prescribed device 2 for minimal hours of use. The patient was advised not to wear the device for more than 8 hours a day.
After wearing the device for 1 week, the patient reported redness after 4 hours of wear. On examination with device 2 after 4 hours of wear, there was a significant edge lift at 12- and 6-o’clock positions and mild impingement staining at 3- and 9-o’clock positions. Another customized device 3 was designed using CAD-CAM technology. Device 3 was designed with an increased toricity and flatter haptic, and all other parameters were similar to those of the previous device. Device 3 was shipped directly to the patient because he was not able to come for the visit. The patient was advised to use the device for a week and come for review with device 3 after 6 hours of wear.
The patient reported redness nasally after 5 hours of wear with device 3. After 6 hours of wear, device 3 showed a relatively lesser edge lift than device 2 and mild impingement in 3- and 9-o’clock positions without significant staining. Device 4, with a slightly flatter haptic and more toricity, was then designed and ordered (Table 1).
Device 4 was dispensed after 1 week. There was no impingement or redness observed after 6 hours of wear. The patient was advised to restrict wearing time to 6 to 8 hours until the next office visit for confirmation of a final fit. He was asked to watch out for pain, redness, intolerance, or any unusual symptoms. Because he could not report for 2- and 4-week reviews, he was followed up over the phone.
On review after 2 months of device 4 wear, the patient presented with no complaints regarding vision or comfort and successful 8 to 12 hours of device wear, although he was advised to wear only 6 to 8 hours. After 6 hours of wear, fit assessment was performed. There was neither impingement staining nor lift, with an adequate amount of vaulting and a stable haptic fit.
The best corrected visual acuity of the patient definitely improved with the PROSE device. There was significant improvement in the patient’s symptoms. The patient had a reduction in dryness, shadows, and double vision after successful wear of the device. The success could be caused by the front surface eccentricity incorporated in PROSE, which has been shown to minimize higher-order aberrations, thereby reducing shadows and glare.9,10
On examining the topography, biomicroscopy, and scleral device fitting images, it was observed that the patient had a larger palpebral aperture with a steeper cornea and scleral toricity. With the cornea being steeper and the adjacent sclera flatter, the optimal fit was a smaller-diameter device. The smaller device increased the stability and resulted in a better sclera-haptic relationship despite the fact that steeper corneas usually dictate using a larger-diameter device.11 In this instance, the haptic alignment on the sclera was responsible for the change in vault of the device. The alignment of a device on the sclera can affect the limbal clearance and corneal clearance in a PROSE device. Also, multiple trials were required to arrive at a haptic without any compression on the sclera. Impingement changes in the sclera were noted because of different haptic curvatures and with increasing wearing hours. With the underlying scleral conjunctival tissue being deformable with external forces or pressure, an increased chair time is required to observe noticeable reactions in post–device wear.11 The toricity of the sclera can produce symptoms in patients even after 6 hours of device wear. There is the absolute need for continuous follow-up of the patient after prescribing the device. A number of studies are currently assessing these unpredictable relationships.11–13
This case report describes post-LASIK keratectasia using cutting-edge scleral contact lens fitting. In this case, the PROSE device ultimately solved all vision issues and ocular comfort.
We thank Boston Foundation for Sight (Needham, MA) for its continuous support in designing and manufacturing of the PROSE scleral devices.
Received September 4, 2013; accepted November 22, 2013.
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