Case Report

Post-op Dry Eye
Pesters LASIK Patient

Multiple predisposing factors coupled with surgical trauma trigger troublesome symptoms. Copious lubrication provides an effective remedy.

Debra L. Denton

Carl Powers, O.D.

Philip E. Walling, O.D.

Petoskey, Mich.

Optometrists who comanage LASIK must screen candidates to determine if they fall within the right physical and optical parameters to make for a good outcome with minimal complications. Corneal integrity is a key parameter. Any compromise to the cornea, such as the effects associated with dry eye, can have a negative impact on the patient’s post-surgical comfort and visual outcome. This case describes what happened to a LASIK patient with multiple predisposing factors for dry eye.

History and Findings

A 49-year-old white female presented for a pre-LASIK evaluation. She was a long-time soft contact lens wearer, but dry eyes had made lens wear intolerable. Her systemic history included hormonal changes, depression and heart palpitations. She was taking the synthetic hormones Premarin (conjugated estrogens) and Provera (medroxyprogesterone), the antidepressant Paxil (paroxetine), the antihypertensive Vaseretic (enalapril-hydrochlorothiazide) and the antiarrhythmic Norpace (disopyramide). Her ocular history was unremarkable.


One month after LASIK, slit lamp evaluation revealed light peripheral staining O.D. and heavy peripheral staining O.S., especially inferonasally. Breakdown of the epithelium and Bowman’s membrane caused some stromal fluorescein staining. The central cornea was clear and free of stromal haze. (The top images depict the right eye, the bottom images the left.)

The subjective refraction resulted in -5.50 O.D. and -4.50 -2.75 x 174 O.S., giving 20/20-2 O.D., 20/20-2 O.S. and 20/20-1 O.U. Cycloplegic refraction yielded visual acuities of 20/20-1 O.D., 20/20-1 O.S. and 20/15 O.U. through -5.00 O.D. and -4.00 -1.50 x 176 O.S. Keratometry readings were 44.75@180, 44.00@90 O.D.; and 44.75@150, 46.12@60 O.S. Slit lamp biomicroscopy, binocular indirect ophthalmoscopy and applanation tonometry were within normal limits.

We discussed with the patient the risk of complications due to the inconsistency of astigmatism in her left eye. One month later she underwent bilateral LASIK with no immediate complications.

Follow-up Visits

Four days post-op, her refraction was -0.50 O.D., +0.25 O.S., resulting in visual acuities of 20/20-2 O.D., 20/20-2 O.S. and 20/20 O.U. She was prescribed TobraDex (tobramycin/dexamethasone) 1gtt qid O.U. and Refresh (Allergan) prn while the cornea healed.

The patient returned to the clinic a month after the procedure with erythema, edema, photosensitivity, dry eye, pain, foreign body sensation and fluctuating vision. The symptoms were worse in her left eye. Visual acuities were 20/40+2 O.D., 20/50 O.S. and 20/25-3 O.U. Slit lamp evaluation revealed light peripheral staining O.D. and heavy peripheral staining O.S., especially inferonasally. Breakdown of the epithelium and Bowman’s membrane caused some stromal fluorescein staining. The central cornea was clear and free of stromal haze. A 1mm epithelial ingrowth was apparent in the temporal cornea of her left eye.

The next day the clinician at the laser center diagnosed severe dry eye and treated it with TearGel (CIBA Vision) 1gtt qid O.U. The epithelial ingrowth was no cause for concern.

Four days later the patient returned to the clinic after touching the tube of TearGel to her left eye. Her signs and symptoms persisted, and her visual acuity had worsened to a blurry 20/200 O.D. and 20/50+3 O.S. Pinhole visual acuities were 20/25+ O.U. A correction of -2.50 O.D. and -1.00 O.S. yielded 20/20 O.U. Keratometry was 42.50@180, 43.75@90 O.D.; and 41.75@180, 42.00@90 O.S. The staining pattern was similar to the previous visit, except now there was an additional abrasion in the left eye from the TearGel tube. There were no cells or flare in the anterior chamber or endothelium.

We treated the abrasion with Polytrim (trimethoprim/polymyxin B) qid for 2-3 days. The patient continued using Refresh and TearGel O.U. She was closely monitored for the next month as her signs and symptoms improved.

At her three-month post-op evaluation her vision was good and her eyes felt comfortable. Unaided visual acuity was 20/20-3 O.D. and 20/20-1 O.S. Slit lamp evaluation revealed some lingering epithelial staining, worse in the left eye. We reduced the TearGel dosing to once daily at bedtime O.U. with Refresh q3-4h O.U.

Discussion

Numerous factors can inhibit the normal production and function of the tear layer.^2,4 The compromise of corneal integrity that occurs in refractive surgery can exacerbate any predisposing factors for dry eye and magnify the effects of the condition. When recommending refractive surgery, it’s important to consider dry eye and any predisposing factors. As this case illustrates, these factors can lead to postoperative complications.

Factors such as increasing age, changing hormone levels and systemic medications can decrease the quantity and compromise the quality of tears, resulting in dry eye.⁴ Aging as well as hormone fluctuations both decrease tear production. Middle-aged women have decreasing estrogen levels throughout menopause. This not only affects the ocular surface, but also reduces aqueous output.⁴ Various classes of systemic medications can further contribute to dry eye.^1,13 This patient was taking three such medications—the antidepressant Paxil, the antihypertensive Vaseretic, and the antiarrhythmic Norpace.

FDA investigators concluded that “hormone replacement therapy (HRT) is probably not a factor affecting the outcome of laser refractive procedures … the changes in outcomes among older female laser patients appear to be age-related.”¹ The report said nothing about the influence of other systemic medications on LASIK outcomes. Nor did it propose a definite answer as to why older females have more complications than other populations. The authors merely said this “continues to be a confounding problem.”¹

This patient’s increasing age, changing hormone levels and use of systemic medications were clearly predisposing factors for dry eye. But there’s probably more to it than that. Refractive procedures affect the cornea’s normal physiology and hydration.¹² Diminished corneal sensitivity can decrease the blink reflex, impede epithelial healing, compromise the rate of epithelial cell mitosis, decrease tear flow, and set the stage for various types of keratitis.¹²

During LASIK, a corneal flap is cut 75-150um deep and retracted nasally. This depth involves the epithelium, Bowman’s layer and the anterior stroma, affecting the nerves of the latter. The laser ablation itself affects the deeper stromal nerves.

It was originally believed that LASIK preserved corneal sensitivity because the anterior cornea remained intact. Studies now show that pre-operative sensitivity levels do not return until about 6 months after the procedure.¹² Sensitivity returns first in the nasal portion of the flap and later in the central cornea.¹² Compared with PRK, the corneal sensitivity in LASIK is significantly more depressed at the 3-month check. Sensitivity 6 months out is comparable between the two procedures.¹²

For most patients, 6 months of reduced sensitivity may have little effect on the healing process. However, it’s difficult to determine the implications when the cornea’s integrity is already compromised. Corneal sensitivity can definitely decrease tear flow and reflex blinking, thus exacerbate dry eye.¹²

Corneal contour is another factor to consider following LASIK. After LASIK, the center of the cornea is significantly flatter than the periphery. A study involving myopes of -3.00D to -6.00D found an average corneal flattening of 4.98D (11.3%) following LASIK.¹⁰

The irregular corneal shape can inhibit the proper functioning of tears. But does this altered shape also affect blinking?⁴ Reflex blinking protects the eyes from infection, distributes the tears, and brushes tears and debris toward the puncta for drainage. If the cornea is misshapen, the blinking lid may miss an area as it swipes over irregular curves, resulting in areas of non-wetting or stagnation of tears. An ineffective blink would then fail to clear debris or fully rehydrate the cornea. The effects of corneal alterations compound the problems of decreased corneal sensitivity and dry eye.

There may be another reason for dry eye after LASIK: it may disrupt the goblet cells. Suction at the limbus—the site of most goblet cells—might cause a temporary breakdown in goblet cell physiology and result in decreased tear adherence.¹⁴

LASIK can trigger dry eye or exacerbate a preexisting dry eye. But that doesn’t necessarily rule out dry eye patients as candidates for laser vision correction. Optometrists should address the dry eye problem before recommending LASIK. Non-preserved artificial tears, ointments and punctal plugs are the most common treatments. But these aren’t the only options. There are also ocular inserts and mucolytic agents. Environmental solutions may include decreasing room temperatures and using a humidifier.⁴

After the procedure, keep these patients on a more stringent dosage of artificial tears. An as-needed schedule is not sufficient for everyone and they can easily forget it until the dry eye symptoms become bothersome and problematic. If you treat the dry eye effectively prior to LASIK and take cautionary steps postoperatively, then even a dry eye patient can be a successful candidate.

Ms. Denton is a fourth-year student at the Michigan College of Optometry. Dr. Powers is in private practice. Dr. Walling teaches at MCO. Ms. Denton wishes to thank John De Groot, O.D., for his assistance.

top

1. Hormone replacement therapy not factor in laser refraction, study suggests. American Optometric Association News 1998;37(9):8.

2. Cullum RD Jr., Chang B. The Wills Eye Manual Office and Emergency Room Diagnosis and Treatment of Eye Disease. 2nd ed. Philadelphia: Lippincott-Raven, 1994.

3. Doane JF. A comprehensive approach to LASIK. J Ophthal Nurs Technol 1996;15:144-7.

4. Hart WM Jr. Adler’s Physiology of the Eye. 9th ed. St. Louis: Mosby-Year Book Inc. 1992.

5. Jones SS. Effects of laser in situ keratomileusis (LASIK) on the corneal endothelium. Am J Ophthalmol 1998;125(4):465-71.

6. Kanellopoulos AJ. Comparison of corneal sensation following photorefractive keratectomy and laser in situ kertomileusis. J Cataract Refract Surg 1997;23(1):34-8.

7. Kanski JJ. Clinical Ophthalmology. 3rd ed. Oxford: Butterworth-Heinemann 1997.

8. Krachmer JH. Cornea Volume II. St. Louis: Mosby-Year Book Inc. 1997.

9. Machat JJ. Excimer Laser Refractive Surgery. Thorofare, N.J,: SLACK Inc. 1996.

10. Maldonado BA, Onnis R. Results of laser in situ keratomileusis in different degrees of myopia. Ophthalmology 1998;105(4):606-11.

11. Onofrey B, Skorin L Jr., Holdeman NR. Ocular Therapeutics Handbook: A Clinical Manual. Philadelphia: Lippincott-Ravin Publishers 1998.

12. Perez-Santonja JJ, et. al. Corneal sensitivity after photorefractive keratectomy and laser in situ keratomileusis for low myopia. American Journal of Ophthalmology 1999;127(5):497-504.

13. Phillips S, Phillips J. Quick Drug Reference for the Optometrists. Ohio: Anadem Publishing 1998.

14. Karpecki P. Personal communication 1999.

top

Return to March Highlights