Keratoconus Post Intacs®: Rob Ensley, OD, FAAO, FSLS
A 44-year-old Caucasian male was referred for a specialty contact lens consultation and fitting. He had been previously diagnosed with keratoconus in both eyes and underwent bilateral Intacs® implantation about eight months prior. He presented without any form of vision correction, complaining of blurry, distorted vision in both eyes.
Test Procedures, Fitting/Refitting, Design, and Ordering
Visit #1: Initial Visit
Unaided Distance Visual Acuities
OD: -9.25 -2.50 x 003 (20/70)
OS: -3.75 -0.75 x 045 (20/70)
Zeiss Humphrey 599 Autorefractor/Keratometer
Pupils were equal, round, and reactive to light and accommodation. Extraocular motility was smooth and full and confrontational visual fields were grossly full. Intraocular pressure was 14 mmHg in the right eye and 15 mmHg in the left eye using an iCare tonometer.
Anterior and Posterior Segment Evaluation
Anterior segment examination revealed 1+ bulbar conjunctival injection and trace, early nasal pingueculae in both eyes. Both corneas had mild stromal thinning, but no evidence of stromal scarring. Each eye had double Intacs® in the superior and inferior quadrants of the cornea (Figures 1a and 1b). Posterior lid margins were significant for early lid telangiectasia and inspissation, indicating 2+ meibomian gland dysfunction. The crystalline lenses were clear in each eye. Posterior pole examination using Daytona Optomap® retinal imaging, was unremarkable.
Corneal topography was ordered for both eyes using the Medmont E300 corneal topographer (Figures 2a and 2b). Both eyes revealed a central area of steepening with a steep K reading in the mid to upper 50’s dioptric range. The double Intacs® now provide a distorted shape to the cornea with what appeared to be a flatter superior cornea and steeper area, inferior to the apex of what appears to be an oval cone in each eye.
Scleral Lens Fitting Visit
Diagnostic Lens Selection
Given the corneal irregularity and the highly anisometropic refraction, spectacles would not provide optimal vision correction for the patient. Rigid gas permeable (GP) lenses would provide the best acuity given their ability to mask corneal irregularity and reduce higher order aberrations. Based on the patient’s prior history, topographies, and comfort demands, we elected to proceed with fitting him in scleral lenses. The typical keratoconic eye requires a prolate design scleral lens; however, Intacs® can potentially flatten the central cornea, which may require an oblate design. The patient was fit using the Zenlens by Alden Optical, as the diagnostic set contains both prolate and oblate design lenses.
Diagnostic Lenses: Zenlens
OD: 4.20 sag/8.20 BC/16.0 mm prolate/-2.00/Standard APS and LCD
OS: 4.20 sag/8.20 BC/16.0 mm prolate/-2.00/Standard APS and LCD
After allowing approximately 15 minutes to settle, for the right eye the central clearance was estimated to be approximately 150 microns using an optic section in the slit lamp. It was noted that the lens was decentered inferiorly just slightly; however, there was no significant blanching, impingement, or edge lift of the haptic zone. An over-refraction of +4.50DS yielded 20/25 visual acuity at distance.
For the left eye, the central clearance was estimated to be slightly greater than the right eye at approximately 200 microns. It was also noted that there was very faint blanching at 3 and 9 o’clock, most notably over the trace nasal pinguecula. Over-refraction of the left lens was +3.25DS, with distance acuity of 20/25.
Based on this information, the goal for the initial lenses was to increase the sagittal depth of both lenses and incorporate a slightly toric periphery for better centration and to alleviate the mild blanching.
Final Lens Order: Zenlens #1 OU
OD: 4.30 sag/8.20 BC/16.0 mm/+2.75 CLP/APS Flat-1 H, Std V/LCD Std/CT 0.54
OS: 4.30 sag/8.20 BC/16.0 mm/+1.25 CLP/APS Flat-1 H, Std V/LCD Std/CT 0.49
Patient Consultation and Education
Visit #2: Zenlens #1 Dispense Appointment
The patient returned two weeks later for the dispensing. The lenses were placed on eye by an optometric technician using 0.9% sodium chloride inhalation solution and mixed with a sodium fluorescein strip to aid in assessing the lens
fit. After allowing several minutes to settle, vision was recorded as 20/25 in both right and left eyes. The lenses were well centered with the back surface toric markings, denoting the flat meridian, at 3 and 9 o’clock. There was no blanching or impingement noted, but the in-office settling time was no more than 15 minutes. Central clearance was estimated to be approximately 200 microns in the right eye and 250 microns in the left eye. There was no apparent limbal touch, and the patient reported good comfort.
Application, Removal, and Care Education
The patient was able to successfully complete application and removal training with our trained staff. He was instructed to fill the lenses with 0.9% non-preserved sodium chloride inhalation solution (off-label) and disinfect the lenses with a peroxide-based solution, which was demonstrated in-office. A two-week follow-up visit was scheduled.
Follow-up Care and Final Outcome
Visit #3: Two Week Follow-Up
The patient presented to his follow-up two weeks later, having worn his lenses for five hours. He reported good comfort and vision over the course of the two weeks, with a maximum wearing time of 13 hours. Visual acuity was measured as 20/25 in the right eye and 20/40 in the left eye, with a loose lens over-refraction of +0.50D in the right eye and +1.00D in the left eye to achieve 20/25 acuity. Central clearance was measured at 109 microns in the right eye and 179 microns in the left eye using a Cirrus optical coherence tomographer (OCT) (Figures 3a and 3b). There did appear to be very faint blanching in both eyes nasally, over the mild pingueculae. After removing the lenses, the corneas were stained with a sodium fluorescein strip. There were no areas of coalesced staining over the central cornea or the limbus in either eye.
Over the course of two weeks, it appears the lenses settled approximately 75 to 100 microns in both eyes. New lenses were ordered to incorporate added sagittal depth in the right eye and a power change in both eyes, as indicated by the over-refraction. The center thickness was also reduced to 0.38mm in the right eye and 0.35mm in the left eye, in order to reduce the overall weight of the lenses and hopefully reduce the faint blanching. The following parameters were ordered:
Second Lens Order: Zenlens #2 OU
OD: 4.40 sag/8.20 BC/16.0 mm/+3.25 CLP/APS Flat-1 H, Std V/LCD Std/CT 0.38
OS: 4.30 sag/8.20 BC/16.0 mm/+2.25 CLP/APS Flat-1 H, Std V/LCD Std/CT 0.35
Visits #4 & #5: Dispense of Zenlens #2 and Follow-Up
The patient returned one month later for his dispensing appointment of the second pair of lenses. Visual acuity was 20/25 in both eyes. Central clearance was estimated in the slit lamp at approximately 200 microns after approximately 15 to 20 minutes of settling. The lenses were still landing on the nasal pingueculae, but there was no immediate blanching and the patient did not report discomfort. He was instructed to return in two to three weeks for one last follow-up visit.
At the follow-up three and a half weeks later, the patient was doing well, with an average wearing time of 12 hours per day. Visual acuity was stable at 20/25 in each eye, and central clearance was still estimated with the slit lamp to be approximately 200 microns. He reported good comfort, with no significant injection or compression around the periphery of the lens. He had been wearing scleral lenses now for approximately eight weeks, with no significant difficulties or complications. The fit with the second pair of lenses had proven to be stable for nearly a month. We discussed the importance of long-term follow-up to reassess the fit of the lenses and corneal health. He was scheduled for follow-up in six months.
Visit #6: Six Month Follow-Up
The patient returned six months later reporting stable vision, good comfort, and no difficulties with the lenses. Average wearing time was still 12 hours per day. At this visit, he had been wearing the lenses for about five hours. Visual acuity was measured at 20/25 in both right and left eyes. OCT measurements of the central clearance were 221 microns in the right eye and 170 microns in the left eye (Figures 4a and 4b). Both lenses are settling on the nasal pinguecula, with very faint blanching (Figures 5a and 5b). After lens removal, there was no coalesced limbal staining, although there was evidence of mild compression on the bulbar conjunctiva nasally in both eyes. The patient denied any significant discomfort with lens wear, so we elected to continue to monitor the fit. In the future, a microvault will likely be incorporated to reduce the pressure on the mild pingueculae. He was scheduled to return in six months for follow-up and probable re-fit.
Discussion/Alternative Management Options
Intacs®, the only available ICRS in the United States, was originally approved by the Food and Drug Administration for the reduction of myopia in 1999. In 2004, Intacs® received a humanitarian device exemption for use in the treatment of keratoconus.3 Manufactured from PMMA, the segments have a fixed outer diameter and width, but vary in thickness from 0.210 mm to 0.450 mm.4 A tunnel is created at approximately 70 percent depth of the corneal stroma to insert the segments.4 The segments act as a spacer between lamellar bundles, thus shortening the arc length.5 This serves to reduce mean keratometry readings and refractive error.
To be eligible for ICRS, patients must be 21 years of age or older, have a corneal thickness of 450 microns or greater at the incision site, and a clear visual axis.4 There are no absolute contraindications in regards to keratometry measurements or refractive status; however, studies reveal better outcomes when the max steep K is less than 55.0 to 57.0 diopters, and cylinder power is less than 3.50 diopters and spherical myopia is greater than 1.75 diopters.6 Contraindications include patients with abnormally thin corneas or a thickness of less than 450 microns at the incision site, autoimmune or immunodeficiency disease, or presence of ocular conditions that would predispose to complications such as recurrent corneal erosion syndrome, corneal dystrophies or degenerations, and corneal endothelial cell compromise.4
There are several complications that can occur with ICRS. The most serious complications include infection due to poor wound healing, and further corneal thinning over the segments. Minor complications include foreign body sensation, photophobia, and glare.4,5 Most patients that undergo ICRS also expect improvement in their vision. While studies show that ICRS implantation can improve uncorrected visual acuity, many patients still require a contact lens to provide optimal levels of vision correction.6 For these patients, fitting contact lenses is often more complicated.
Mild-to-moderate keratoconic patients can be successfully fit with a wide variety of contact lenses including corneal GPs, hybrid lenses, and scleral lens designs. In many cases corneal GP lenses are still the lenses of choice because of their ease of fitting. Post Intacs® implantation, the corneal shape is altered, often creating a more oblate-shaped cornea. This can make centration with corneal GPs difficult, resulting in poor optics or discomfort. In these situations, scleral lenses may provide a better outcome.
Scleral lenses are large diameter GP lenses that vault over the cornea and rest entirely on the sclera. The scleral lens chamber is filled with a preservative-free fluid that bathes the corneal surface. These features allow scleral lenses to improve vision for a variety of corneal irregularities and provide a therapeutic effect for moderate-to-severe ocular surface disease. More recently, scleral lenses are being introduced as refractive correction options for the normal cornea.
Over the past several years there has been a proliferation of scleral lens designs. Although individual designs may have unique characteristics or nomenclatures, all scleral lenses share three basic zones.7 The first zone moving from the center of the lens towards the periphery is the optic zone. This zone is manipulated by the base curve and should approximately match the shape of the central cornea. The optic zone can be spherical or have front surface toric or multifocal optics incorporated. Similar to a corneal GP lens, when the base curve is adjusted, “SAM-FAP” rules apply to scleral lenses to account for changes in the post-lens tear layer. The next zone is the transition zone, which can be one or more curves that vault the mid-peripheral cornea and limbus. This zone can manipulate the sagittal height of the lens. If reverse geometry is needed, the transition zone may be steepened, while flattening the base curve. The landing zone or haptic zone is the outermost zone that aligns to the bulbar conjunctiva. In cases of poor alignment, toric haptics or quadrant-specific haptics can be utilized.
One of the many benefits of modern scleral designs is their high degree of customization. With both prolate and oblate designs widely available, nearly any degree of irregular or diseased cornea can be successfully vaulted. Recent studies indicate the sclera is asymmetric, often requiring back-surface toric haptics.7,8 Accordingly, newer diagnostic sets include lenses with toric haptics. Improved alignment to the bulbar conjunctiva reduces complications including conjunctival blanching or impingement, and lens flexure leading to poor optics. If conjunctival irregularities are present, such as pingueculae or filtering blebs, some scleral designs have the capability to vault or notch over the irregularity. In the most advanced cases of corneal or conjunctival abnormalities, impression molding and 3D printed scleral prosthetics can be made.
Despite undergoing bilateral double Intacs® implantation to improve uncorrected visual acuity, the patient in this case report still suffered from blurry, distorted vision. Given his steep K readings in both eyes, this result is not unexpected when comparing to available study results. Fortunately, scleral lenses have been able to provide this patient with both good vision and comfort. The fitting process was fairly uncomplicated. We did adjust the sagittal depth to account for lens settling, and decreased the center thickness to improve oxygen permeability. His nasal pingueculae have not been of significant concern, but increasing the haptic toricity or adding a microvault may improve the lens fit. If no changes are to be made, we will continue to monitor the patient every six months.
- Rabinowitz YS. Keratoconus. Surv Ophthalmol. 1998; 42:297 – 319.
- 2014 Eye Banking Statistical Report. Eye Bank Association of America. Available at www.restoresight.org. Accessibility verified June 2, 2016.
- History of Intacs®. Intacs® Corneal Implants. Available at http://intacsforkeratoconus.com/aboutintacs. Accessibility verified December 20, 2016.
- Intacs® for Keratoconus Professional Use Information Manual. Intacs® Corneal Implants. Available at http://intacsforkeratoconus.com/wp-content/uploads/2015/05/Intacs-for-Keratoconus- 11400-116001.pdf . Accessibility verified December 20, 2016.
- Vega-Estrada A, Alio JL. The use of intracorneal ring segments in keratoconus. Eye and Vision.2016; 3:8.
- Rabinowitz YS. Intacs for keratoconus. Curr Opin Ophthalmol. 2007; 18:279 – 283.
- van der Worp E. A Guide to Scleral Lens Fitting, Version 2.0 [monograph online]. Forest Grove, OR: Pacific University; 2015. Available from: http://commons.pacificu.edu/mono/10/.
- Ritzmann M, Caroline P, Walker M, Stephens P, Kojima R, Kinoshita B, Lampa M, André M, Zheng F. Understanding scleral shape with the Eaglet Eye Surface Profiler. Scientific Poster presented at the Global Specialty Lens Symposium. Las Vegas. January 2015.
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