NOV 06, 2017
Refractive Subspecialty Day 2016
- Complications are uncommon, and surface ablation is a relatively safe refractive surgical procedure.
- Complications can occur from the ablation, the epithelial defect, wound healing, or medications used perioperatively.
- Laser delivery technology continues to improve.
- Wound healing is better understood than in the past.
Ablation-Related Complications: Irregular Astigmatism
- Irregular astigmatism can occur because of decentration of the optical aspect of the ablation. This can occur due to misalignment, poor patient fixation, or malfunction of the laser.
- Decentration may result in a patient complaining of glare or halo; in severe cases it may lead to loss of BCVA.
- Prevention includes understanding the alignment process for your laser equipment as well as verifying proper patient fixation on the target of the laser. Pupil tracking technology has improved but has not eliminated decentration.
- Detection of a decentration is done through topography once the epithelium has healed and stabilized after surface ablation. Wavefront will typically show large amounts of coma when performed in an eye with a decentration.
- Symptoms are greater in patients who have larger amounts of decentration, or deeper ablations.
- Wavefront-guided ablation may reduce the amount of decentration of the optics because it takes into consideration changes in the center of the pupil in bright and dim light. Most wavefront optical systems work to center the optical aspect of the distance correction on the dim light pupil of the aberrometer instead of the bright light pupil center that the laser treats under. This may reduce small amounts of error in alignment for the patient.
- Irregular ablation
- Uneven ablation may occur when fluid, sponge material, or residual epithelium is blocking the laser treatment. It is important to make sure that the epithelium is completely removed in the area of the ablation, and that no excess fluid blocks the ablation of the laser. Other debris such as sponge material or meibomian gland secretions should be removed from the surface of the eye prior to the ablation.
- These other reasons for irregular astigmatism may also cause symptoms of glare or halo as well as potential for loss of BCVA. Detection of irregular astigmatism is also done through topography and wavefront analysis.
- Often irregular astigmatism can improve over time through epithelial remodeling, and so waiting 6-12 months for this to occur is often helpful in mitigating symptoms. Glasses may help in some mild cases of irregular astigmatism. Rigid contact lens wear can also mitigate symptoms in patients with more severe irregular astigmatism. Miotics may be helpful in some patients. Wavefront-guided and topographic guided laser correction are also helpful in patients who have significant irregular astigmatism where a surgical process for improvement is desired.
- In treating patients with irregular astigmatism, rule out ectasia by reviewing old topographies if possible. Ectasia is less common with surface ablation but may be present. Understand whether there are other issues related to the irregular astigmatism like corneal haze, dryness, basement membrane dystrophy, or pre-existing corneal scarring.
- Patients with fixation errors on the original treatment may exhibit variable fixation on testing, such as corneal topography or wavefront analysis, and may be more prone to variable fixation with retreatment.
- Subepithelial corneal haze will typically appear in the first few months after PRK, with a peak of intensity at 2 months, and then typically improve over 6-12 months.
- Topical steroids are often used after surface ablation to reduce the incidence of haze.
- Mitomycin C (MMC) is often used at the time of the treatment to reduce the incidence of haze and has been used in varying concentrations for varying lengths of time with no clear evidence for specific dosing. Effective concentrations appear to be from 0.02 mg/cc (0.002%) to 0.2 mg/cc (0.02% for 10-120 seconds. The safety profile of MMC appears to be excellent.
- If haze does occur, then mechanical removal followed by laser removal and MMC and steroids during healing can often improve the haze significantly. Keratoplasty for haze is rare.
- Many patients who seek refractive surgery do so because of contact lens intolerance.
- Much of the contact lens intolerance is from aqueous deficiency and meibomian gland dysfunction– related evaporative dry eye.
- Identification of this group of patients preoperatively allows management of the dry eye and education of the patient as to the chronicity of the dry eye.
- Many patients will have an increase in dry eye symptoms and findings after corneal surgery.
- Lid hygiene, tear supplementation, and oral omega-3 are often helpful.
- In patients with more severe disease, topical cyclosporine, lubricant ointments, and oral doxycycline may be useful.
- Typically, the tear function and epithelial health will return to baseline at 6-12 months.
- In many patients, even though they return to baseline, there may still be dissatisfaction if they were unaware that they originally had the problem with their tear film.
- Sterile or infectious infiltrates can be found after surface ablation.
- Careful monitoring of the cornea can help to detect the occurrence of these issues.
- In suspected infectious keratitis, culturing and antibiotics tailored to the infection can help to resolve the infectious process and hopefully minimize scarring that might affect long-term vision.
- Sterile infiltrates can occur due to overuse of topical nonsteroidal drugs or in patients with significant ocular rosacea and staph marginal keratitis.
Steroid Response Pressure Problems
- Elevated IOP can occur with use of topical steroids in some patients.
- Monitoring the IOP at the postoperative visits can help to monitor the IOP.
- Fortunately, elevated IOP is uncommon.
- Alio JL, Muftuoglu O, Ortiz D, et al. Ten-year follow-up of photorefractive for myopia of less than -6 diopters. Am J Ophthalmol. 2008; 145:29-36.
- Alio JL, Muftuoglu O, Ortiz D, et al. Ten-year follow-up of photorefractive keratectomy for myopia of more than -6 diopters. Am J Ophthalmol. 2008; 145:37-45.
- Bricola G, Scotto R, Mete M, et al. A 14-year follow-up of photorefractive keratectomy. J Refract Surg. 2009; 25:545-552.
- Edwards JD, Bower KS, Sediq DA, et al. Effects of lotrafilcon A and omafilcon A bandage contact lenses on visual outcomes after photorefractive keratectomy. J Cataract Refract Surg. 2008; 34:1288-1294.
- Fahmy AM, Hardten DR. Dry eye after refractive surgery. In: Chang DF, ed. Mastering Refractive IOLs: The Art and Science. Thorofare, N.J.: Slack Inc.; 2008: ch. 234, pp. 855-862.
- Koshimizu J, Dhanuka R, Yamaguchi T. Ten-year follow-up of photorefractive keratectomy for myopia. Graefes Arch Clin Exp Ophthalmol. 2010; 248:1817-1825.
- Kramarevsky N, Hardten DR. Excimer laser photorefractive keratectomy. In: Yanoff M and Duker JS, eds. Ophthalmology, 3rd ed. Philadelphia: Mosby; 2009: ch. 3.4, pp. 131-144.
- Leccisotti A. Mitomycin-C in hyperopic photorefractive keratectomy. J Cataract Refract Surg. 2009; 35:682-687.
- Lee SB, Hwang BS, Lee J. Effects of decentration of photorefractive keratectomy on the induction of higher order wavefront aberrations. J Refract Surg. 2010; 26:731-743.
- Lichtinger A, Purcell TL, Schanzlin DJ, et al. Gabapentin for postoperative pain after photorefractive keratectomy: a prospective, randomized, double-blind, placebo-controlled trial. J Refract Surg. 2011; 27:613-617.
- Magli A, Forte R, Rombetto L, Carelli R. Bilateral methicillinresistant Staphylococcus aureus keratitis following hyperopic photorefractive surgery. Int Ophthalmol. 2012; 32:47-49.
- Mah FS, Davidson R, Holland EJ, et al; for the ASCRS Cornea Clinical Committee. Current knowledge about and recommendations for ocular methicillin-resistant Staphylococcus aureus. J Cataract Refract Surg. 2014; 40:1894-1908,
- Nassaralla BA, McLeod SD, Nassaralla JJ. Prophylactic mitomycin C to inhibit corneal haze after photorefractive keratectomy for residual myopia following radial keratotomy. J Refract Surg. 2007; 23:226-232.
- Shalaby A, Kaye GB, Gimbel HV. Mitomycin C in photorefractive keratectomy. J Refract Surg. 2009; 25:S93-97.
- Shojaei A, Mohammad-Rabei H, Eslani M. Long-term evaluation of complications and results of photorefractive keratectomy in myopia: an 8-year follow-up. Cornea 2009; 28:304-310.
- Taylor KR, Caldwell MC, Payne AM, et al. Comparison of 3 silicone hydrogel bandage soft contact lenses for pain control after photorefractive keratectomy. J Cataract Refract Surg. 2014; 40:1798-1804.
- Thornton I, Xu M, Krueger RR. Comparison of standard (0.02%) and low dose (0.002%) mitomycin C in the prevention of corneal haze following surface ablation for myopia. J Refract Surg. 2008; 24:S68-76.
- Torricelli AA, Santhiago MR, Wilson SE. Topical cyclosporine A treatment in corneal refractive surgery and patients with dry eye. J Refract Surg. 2014; 30:558-564.