Man presents with progressive blurry vision, monocular diplopia
He was previously diagnosed with mild to moderate cataracts in both eyes, keratoconus in both eyes and ptosis of bilateral upper eyelids.
A 76-year-old man was referred to the Lahey Medical Center ophthalmology department for a cataract evaluation. He complained of progressive blurry vision in both eyes associated with glare worse at night and a monocular diplopia in his left eye.
He had previously been seen by an outside ophthalmologist who diagnosed him with mild to moderate cataracts in both eyes, keratoconus in both eyes and ptosis of bilateral upper eyelids. He trialed rigid gas permeable contact lenses several years ago but had difficulty with insertion and removal. Artificial tears did not improve the patient’s monocular diplopia. The patient was told cataract surgery would help with his blurry vision but that he would need to see a cornea specialist due to his keratoconus.
His medical history was notable for Parkinson’s disease, hyperlipidemia, benign prostatic hyperplasia and untreated anxiety. His medications included levodopa-carbidopa, hyperlipidemia, atorvastatin and tamsulosin.
The patient’s best corrected visual acuity was 20/40 in the right eye and 20/200 in the left eye. Pupils were symmetric, round and reactive with no afferent pupillary defect. IOPs were within normal limits in each eye, and ocular motility was full. On external examination, he was noted to have bilateral ptosis that appeared to cross the visual axis (Figure 1) with unusually tight eyelids. His upper lid excursion was 10 mm in both eyes, and he had an MRD1 of 1 mm in both eyes. On slit lamp examination, he had Vogt’s striae, mild inferior corneal thinning and a Fleisher ring in both eyes. His left cornea had a clear apical corneal nodule approximately 2 mm × 2 mm. He had 1 to 2+ nuclear sclerotic cataracts in both eyes. Fundus exam was unremarkable in both eyes.
Before obtaining biometry and topography measurements to complete the cataract evaluation, it was deemed necessary to remove the corneal nodule, which was thought to be due to nodular epithelial hyperplasia. The patient tolerated a superficial keratectomy in his left eye and afterward reported resolution of his monocular diplopia. After this procedure, the epithelium was smooth, and the patient had a small central corneal scar at the site of the previous corneal nodule.
Accurate biometry readings were unable to be obtained due to the patient’s ptosis and tight eyelids.
Galilei corneal topography was obtained while holding the patient’s eyelids up and away from his globes. This demonstrated 10.15 D of with-the-rule astigmatism at 91° in his right eye and 21.80 D of with-the-rule astigmatism at 86° in his left eye (Figure 2).
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Progressive blurry vision
The patient’s clinical exam was consistent with keratoconus (Vogt’s striae, corneal thinning and Fleischer ring in both eyes); however, he did not have the typical inferior steepening often seen in keratoconus. His topography was notable for a large amount of truncated bow tie astigmatism oriented with-the-rule in both eyes, which is not consistent with other corneal ectasias, such as pellucid marginal degeneration and keratoglobus. Besides his ptotic and tight upper eyelids, the patient did not have other findings on exam to account for the degree of astigmatism. It was felt that his tight upper eyelids in combination with ectatic corneas caused a chronic deformation of his corneas with subsequent marked with-the-rule astigmatism.
Due to the large amount of astigmatism in our patient, it was determined he would likely require either a gas permeable lens or a scleral lens, in addition to any corneal, lenticular or adnexal surgery. He worked with our optometrists but had significant difficulty with insertion and removal of the contact lenses due to a small palpebral aperture and poor dexterity. He was referred to BostonSight for evaluation of a PROSE lens but declined due to out-of-pocket cost. The option of corneal transplant was discussed with the patient, but he was not interested.
The patient was evaluated by oculoplastics for his visually significant ptosis and tight eyelids. Due to his poor levator function bilaterally, he was felt to have myogenic ptosis, perhaps related to his statin use, his Parkinson disease or an undiagnosed myotonic dystrophy. Myasthenia gravis testing was normal, and the patient underwent bilateral ptosis repair via maximum levator resection to Whitnall’s ligament. Topography after ptosis repair was notable for a marked improvement in astigmatism; corneal astigmatism decreased from 10.15 D to 3.96 D ( 6.96) in his right eye and 21.80 D to 8.46 D ( 13.6) in his left eye (Figure 3). His vision was unchanged in his right eye and improved to 20/125 in his left eye.
At this point, the patient wished to proceed with cataract surgery in his left eye. IOL biometry was able to be accurately obtained. Toric IOL use in keratoconus eyes is a topic of debate; however, given the regular astigmatism in our patient, it was felt to be a reasonable option. Unfortunately, the out-of-pocket cost was too high for the patient to pursue a toric lens, and a monofocal IOL was chosen with a target of plano. After left eye cataract surgery, his best corrected vision was 20/50, for which he was happy. Visual acuity in his right eye remained stable at 20/40, and he chose to defer cataract surgery.
Keratoconus is a noninflammatory and progressive disorder characterized by thinning and protrusion of the cornea. Findings include Vogt’s striae (vertical lines in the deep stroma and Descemet’s membrane), Fleisher rings (iron deposition within the epithelium at the base of the cone), irregular astigmatism and corneal thinning with occasional overlying scarring. Topography in keratoconus commonly demonstrates inferior steeping, but other patterns including asymmetric bow tie with a skewed axis, and truncated bow tie is also documented in the literature.
Treatment of cataracts in patients with severe keratoconus, which is why our patient was referred, often requires multimodal intervention and understanding of treatment options. The first step in treating keratoconic eyes with visually significant cataracts is ensuring topographic stability, as small variations can greatly affect biometry and lens choice. Corneal cross-linking can be used to help stabilize progression by stiffening an ectatic cornea and reduce the risk for worsening irregular astigmatism after surgery. Ideally, topographic stability would be demonstrated on sequential visits at least 12 months apart to ensure accurate and reliable measurements are obtained.
Upon stability, biometry and cataract calculations can be obtained, ideally with an IOL formula that has been validated and shown to have good predictability in keratoconic eyes, such as the SRK/T formula. It is important to keep in mind that the axial length and anterior chamber depth are often elongated in keratoconic eyes, which will affect the effective lens position, and that the keratoconic cone is often outside of the visual axis, which can lead to falsely high K measurements. Recent literature suggests that surgeons use the actual K value in mild to moderate keratoconus (defined as Kmax < 55 D) and the standard K value (43.25 D) in severe keratoconus (K > 55 D). The reliability of IOL calculations is inversely proportional to the severity of keratoconus, and patients should be counseled about the possibility of refractive surprise.
When counseling patients on their options for IOL implants, it is important to discuss residual corneal astigmatism after surgery and the possibility of new irregular astigmatism from disease progression and surgical wound creation. Patients should be aware that they may still need RGP or scleral contact lenses to achieve their best vision after cataract surgery. At our institution, most patients receive a monofocal lens as this allows for easier fitting of toric-correcting contact lenses and simplifies any future keratoplasty surgeries. Toric IOLs are a reasonable option in patients with stable and mild keratoconus, good spectacle corrected vision, no anticipated future keratoplasty or RGP/scleral lens requirement, and regular astigmatism. It is important to note that the maximum corneal astigmatism correction from a toric lens is 4.11 D (Alcon SN6AT9). Multifocal and extended depth of field lenses are risky in all but stable and mild cases of keratoconus.
Intraoperative considerations in keratoconus cataract surgery include surgeon’s view and wound creation. At the microscope, the surgeon may note image distortion from severe corneal astigmatism. Some surgeons have reported benefit from using an RGP lens intraoperatively to reduce this image distortion. Wound creation with a clear corneal incision has the potential for inducing new corneal astigmatism. A scleral tunnel wound is preferred by some surgeons although it prolongs surgery, requires more than topical anesthesia and has more postoperative pain. At our institution, surgeons have good outcomes with temporal perilimbal clear corneal incisions.
At the time of this publication, the literature regarding corneal astigmatic change in keratoconus patients undergoing ptosis repair is limited; however, multiple reports have documented topographic and astigmatic changes after ptosis surgery. It is well documented that external pressure from eyelids contributes to corneal astigmatism, and that elevation of lids (with a speculum) reduces overall with-the-rule astigmatism while increasing any against-the-rule astigmatism. This effect seems to have been magnified in the ectatic corneas of our patient. This case highlights the importance of considering all etiologies as well as treatments for astigmatism, especially in keratoconus eyes.
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- For more information:
- Gavin Gorrell, MD, and Naveen K. Rao, MD, can be reached at New England Eye Center, Tufts University School of Medicine. 800 Washington Street, Box 450, Boston, MA 02111; website: www.neec.com.
- Edited by Alison J. Lauter, MD, and Sarah E. Thornton, MD. They can be reached at the New England Eye Center, Tufts University School of Medicine, 800 Washington St., Box 450, Boston, MA 02111; website: www.neec.com.