This is a fantastic time to be fitting contact lenses. The lenses available today have the potential to really improve the lives of our patients—not only by helping them see better, but by providing all-day comfort. In recent years with the development of scleral lenses and hybrid lenses, we have more options for our patients. Scleral lenses are large-diameter, gas-permeable lenses that rest beyond the limits of the cornea and extend onto the sclera. Hybrid lenses have a gas-permeable center and a soft skirt. Both types of lenses can be used when conventional lenses fail.
Scleral Lenses: A Case Study
Let me introduce you to one of my patients. R.P. is a 61-year-old Caucasian male with a history of LASIK presented for a contact lens fitting. His LASIK, performed in Canada in 1999, bilaterally addressed myopia with high astigmatism. An enhancement was performed in the left eye later that same year. Initial vision was good for the first five years after LASIK, until he noticed vision changes in both eyes. When he returned for a LASIK re-evaluation, he was told that he was not a candidate for additional surgery. At that time, he was fitted and started wearing piggyback contact lenses.
R.P. initially presented three years ago, experiencing blurry vision with piggyback lenses and difficulty obtaining a good contact lens fit with hybrid contact lenses for both eyes—the left eye being more difficult than the right.
Entering visual acuity with piggyback contact lenses was 20/25-1 in the right eye and 20/60-2 in the left eye. Pinhole improved vision in the left eye to 20/25-2. Manifest refraction improved vision to 20/20 in the right eye and 20/25 in the left eye. Anterior segment examination was significant for blepharitis in each eye. The corneas in both eyes were clear, without evidence of Vogt’s striae or a Fleischer ring in either eye. LASIK flaps were present in both eyes. Inferior thinning with inferior protrusion was present in each eye. Grade 1+ inferior paracentral punctate epithelial staining was present in each eye. Intraocular pressures were normal. Dilated examination revealed mild nuclear sclerosis of the lens in both eyes. The rest of the dilated examination was normal in each eye.
Corneal topography demonstrated high irregular astigmatism in both eyes with a pellucid-like pattern in both eyes. Sim Ks were 48.71/44.36 at 051 O.D. and 47.80/44.33 at 101 O.S. Central corneal thickness was 436μm in the right eye and 453μm in the left eye. Inferior corneal thickness was 523μm in the right eye and 311μm in the left eye.
The fit with the piggyback lens system demonstrated well-centered soft and gas-permeable (GP) lenses in each eye. The GP lenses fit well centrally; however, trace inferior touch was present in both eyes.
After discussing contact lens options, R.P. decided to proceed with a scleral lens fitting. The initial lenses ordered were 16.0mm lenses in a Jupiter design (Essilor). After several lens adjustments, he is now successfully wearing Jupiter scleral lenses and reports good vision with monovision (binocular 20/20+3 and J1) and comfort with Jupiter scleral lenses. In fact, he believes this is the best his eyesight has been in 30 years.
Both lenses demonstrated good central corneal clearance. There was also limbal clearance with an adequate scleral landing. With both lenses, there was no evidence of edge lift or compression of the conjunctival vessels. Mild sebaceous tear debris was present under both lenses.
Slit lamp evaluation demonstrated 1+ blepharitis in each eye. The conjunctivae were clear in both eyes. The corneas in both eyes were clear with stable LASIK flaps. There was no evidence of microcystic edema or corneal staining in either eye. Continuation of good eyelid hygiene, including eyelid scrubs, warm compresses and AzaSite (azithromycin, Inspire Pharmaceuticals) eye drops, was recommended. In this case, scleral lenses were a very successful option for a patient with post-LASIK ectasia.
Understanding Scleral Lenses
|A cross-sectional view of R.P.’s scleral lens.
Scleral lenses are large-diameter, GP lenses that vault the cornea and rest on the sclera. Scleral lenses were initially used in the late 1800s and early 1900s and have now been reintroduced. However, the manufacturing process for scleral lenses has been improved and larger lens diameters can now be accurately reproduced. Don Ezekiel, O.D. and Perry Rosenthal, M.D., are credited for developing the modern scleral lens.1,2
The late Rob Breece, founder of Medlens Innovations, designed the classification of scleral lens categories. The classification is based on bearing and clearance relative to the average corneal diameter of 12.8mm (see “Scleral Lens Classifications”).
• Indications: Scleral lenses are indicated for primary corneal ectasias (keratoconus, keratoglobus, pellucid marginal degeneration) and secondary corneal ectasias (post-LASIK, post-PRK, post-RK). They are also used for corneal transplants, trauma or corneal scars. These lenses have also been recognized to benefit patients with corneal degenerations or dystrophies such as Salzmann’s nodular degeneration or Terrien’s marginal degeneration.
Scleral lenses can be utilized for severe dry eyes—Graft vs. host disease, Sjögren’s syndrome and Stevens Johnson syndrome, or inflammatory conditions such as limbal stem cell deficiency or ocular cicatricial pemphigoid. Other indications for scleral lenses are neovascularization with hybrid lens designs, poor comfort with traditional gas permeable designs, and high refractive error.
The contraindications for scleral lenses are corneas with significant edema from reduced endothelial cell count.2,4
• Fit: Scleral lenses are fit on the principle of sagittal depth, which is the measurement from the flat plane to the highest point of a concave surface. If the sagittal depth is too high, it leads to central bubbles. If the sagittal depth is too low, it can cause excessive central touch and bubbles in the sclera. If there is excessive mid-peripheral clearance, this can bring about bubbles in the mid-peripheral and limbal zones.
• Pros and Cons: The advantages of scleral lenses include the ability to completely clear the corneal surface, provide good centration and stable visual acuity. The disadvantages may include increased difficulty with respect to application and removal of larger diameter lenses.
• Design: In addition to the standard spherical lens, more specialized design options are available today. Reverse geometry designs and toric peripheral curves can be incorporated into scleral lenses. Back surface and front surface toric options, as well as multifocal scleral lenses, are also available. Patients with a healthy anterior surface and normal topography are more appropriate candidates for multifocal scleral lenses.5
Hybrid Contact Lenses: A Case Study
C.F., a 26-year-old Caucasian male was referred for a comprehensive eye examination due to blurry vision and vision changes with his glasses. C.F last wore soft toric contact lenses for astigmatism one year ago and has not worn them since due to difficulty adjusting to the prescription. GP lenses were tried, but not tolerated due to poor comfort. He was not interested in a contact lens fitting at the time of his examination. Medical history was significant for congenital hydrocephalus with patent ventriculo-peritoneal shunt (VP shunt).
Entering visual acuity with glasses was 20/20 in each eye. Manifest refraction yielded 20/20 vision with subjective improvement in each eye. Astigmatism was present in both eyes, 1.00D in the right eye and 2.25D in the left eye. Anterior segment examination was normal in both eyes. Intraocular pressures were normal. Dilated examination was normal without evidence of optic nerve swelling or optic nerve pallor in either eye. Keratometry measurements were 41.00/42.75 at 109 O.D. and 40.50/43.75 at 083 O.S.
After discussing the contact lens options, C.F. decided to proceed with a hybrid contact lens fitting with Duette contact lenses (SynergEyes). After a single adjustment, C.F. is now successfully wearing O.D. Duette 7.9/-1.75/flat and O.S. Duette 7.9/-2.25/med. Good vision (20/20+2) and comfort was obtained with both lenses.
Both contact lenses demonstrated good central clearance with a thin layer of sodium flourescein. More clearance was present peripherally. Good centration and movement was present with both lenses. Anterior segment examination was normal in both eyes. No evidence of corneal staining was present in either eye. In this case, hybrid contact lenses were a very successful option for a patient with regular astigmatism.
Understanding Hybrid Contact Lenses
Hybrid contact lenses have a gas-permeable center and a soft skirt. More current hybrid lenses are the SynergEyes lenses.
• Duette: The newest SynergEyes lens is the Duette lens. It is comprised of a gas-permeable center with a 130 Dk and a silicone hydrogel skirt with a 84 Dk. The lens is 14.5mm in diameter with a rigid central diameter of 8.4mm. Good vision is obtained due to the rigid gas-permeable optical portion of the lens.
Unlike soft toric lenses, the rotation of the lens does not cause blurring of vision due to the tear layer between the gas-permeable central part of the lens and the cornea. The soft skirt has a low modulus and low wetting angle of 38°—providing tear exchange, movement and comfort.
Appropriate patient candidates for the Duette lens are those who have normal corneas with refractive error, either with or without astigmatism. Patients wearing soft or soft toric contact lenses who would like improved vision are also good candidates for Duette lenses. Additional candidates are gas-permeable contact lens wearers desiring improved lens comfort. Patients involved in sports or those who lead active lifestyles are particularly good candidates for Duette lenses.
In the Duette lens, the gas-permeable portion of the lens vaults the cornea. The junction lift area, corresponding to the peripheral curve of an RGP, has a flatter radius than the skirt curve and lifts the RGP off the cornea. The soft skirt has a revere geometry design.
The ideal fit is central clearance with a thin layer of sodium fluorescein with more clearance present peripherally. Fit adjustments are made by changing the skirt curve instead of the base curve. For example, if there is excessive central pooling under the RGP, the skirt curve is flattened. If there is excessive central bearing under the RGP, the skirt curve is steepened.
• SynergEyes A and KC: The SynergEyes A lens design, by SynergEyes, used for patients with early or moderate keratoconus (in addition to standard corneas). The SynergEyes KC lens design is used in more advanced keratoconus.
Both the central base curve and skirt curvature of SynergEyes lenses are adjustable parameters. The lens should fit with apical clearance over the central cornea with little or no touch in the gas-permeable portion of the lens.
|An ideal fit of the Duette lens.
No bubbles should be present in the central part of lens, and light touch should be present at the rigid/soft junction. The SynergEyes lens should land evenly on the soft skirt without impingement or edge fluting. The lens should move slightly with blinking or if the clinician pushes on the lens using the patients lower lid.
The ideal fit for SynergEyes KC lenses are apical clearance with minimal touch in the rigid portion of the lens and a soft landing where base curve meets the skirt curve.
• SynergEyes ClearKone: The SynergEyes ClearKone lens is designed to vault over the irregular corneal surface without bearing, so that it does not compromise the ocular surface with a reverse geometry design. Unlike gas-permeable lenses, the hybrid platform centers optics independent of the location of the cone. It may be used for central and the majority of de-centered cones, but can also be used for corneas status post-RK, PRK or LASIK-induced ectasia. It may also be able to fit globus, PMD and irregular corneas.6
• Duette Multifocal: The Duette multifocal lens by SynergEyes was recently introduced. It is a hybrid contact lens that provides simultaneous vision while correcting astigmatism. The aspheric center zone incorporates the near add. There is a gradation of power from the near aspheric to the distance aspheric zone.
Like the Duette lens, the rotation of the lens does not cause blurring of vision due to the tear layer between the gas-permeable central part of the lens and the cornea. The fitting of the Duette Multifocal is based on the same principles as the Duette lens, with the addition of a small or large add zone size.
Now, more than ever, we have an opportunity to help our patients successfully wear contact lenses. Scleral and hybrid lenses can change the lives of our patients, by providing good vision with comfortable lenses. I invite you to embrace this new technology—either by fitting the lenses in your practice or consulting with another practitioner.
Dr. Barnett is a senior optometrist at the UC Davis Medical Center in Sacramento, where she performs primary care and eye examinations and fits contact lenses including specialty lenses. She also lectures on optics and contact lenses to ophthalmology residents.
1. Ezekiel DF. Gas Permeable Haptic Lenses. J Br Contact Lens Assoc. 1983 Oct;6(4):158-61.
2. Rosenthal, P, Croteau A. Fluid-ventilated, gas-permeable scleral contact lens is an effective option for managing severe ocular surface disease and many corneal disorders that would otherwise require penetrating keratoplasty. Eye Contact Lens. 2005 May;31(3):130-4.
3. Bennett, ES. New findings from the 2008 Global Keratoconus Congress. CL Spectrum. 2008 May. Available at:
www.clspectrum.com/article.aspx?article=101654 (accessed July 2011).
4. DeNaeyer, GW, Breece, R. Fitting techniques for a scleral lens design. CL Spectrum. 2009 Jan. Available at:
www.clspectrum.com/article.aspx?article=102474 (accessed July 2011).
5. DeNaeyer GW. Modern scleral contact lens fitting. CL Spectrum. 2010 Jun. Available at:
www.clspectrum.com/article.aspx?article=104342 (accessed July 2011).
6. SynergEyes. Introducing ClearKone: Restoring Vision. Changing Lives. 2009 May. Available at:
www.synergeyes.com/documents/CK_pracFLYER_FINAL_snglRevB.pdf (accessed July 2011).