Original article
Long-term Results of Thin Corneas After Refractive Laser Surgery

https://doi.org/10.1016/j.ajo.2007.04.010Get rights and content

Purpose

To report the long-term refractive results of photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) in patients with thin corneas.

Design

A long-term, retrospective, non-randomized follow-up study.

Methods

Sixty-three patients (124 eyes) (28 males and 35 females), who had a preoperative central corneal thickness (CCT) of less than 500 microns and completed at least one year of follow-up examinations after surgery. Thirty-five patients (68 eyes) underwent PRK and 28 patients (56 eyes) underwent LASIK.

Results

Mean preoperative corneal pachymetry was 484.95 ± 6.65 μm (range, 470 to 498 μm) and 482.38 ± 10.73 μm (range, 453 to 499 μm) for LASIK and PRK, respectively. No intraoperative complications were found in both groups. None of the included eyes developed postrefractive corneal ectasia. The mean predictability for the PRK group was 0.08 diopters (D) with a standard deviation of 0.40 D (range, −1.38 to 1.00 D), and the mean predictability for the LASIK group was 0.14 D with a standard deviation of 0.55 D (range, −1.25 to 1.33 D).

Conclusions

Refractive laser surgery with LASIK or PRK in patients with thin corneas (less than 500 μm) seems to be a safe and predictable technique for myopic refractive corrections.

Section snippets

Patient Population

This was a retrospective case series of 63 patients (124 eyes) (28 males and 35 females), aged 17 to 57 years old (mean age, 33.48 ± 9.22 years), who had a preoperative CCT of less than 500 microns and no known preoperative risk factors for keratectasia and who completed at least one year of follow-up examinations after surgery. Thirty-five patients (68 eyes) underwent PRK and 28 patients (56 eyes) underwent LASIK.

All eyes underwent primary procedures (61 patients with bilateral and two with

Results

Mean follow-up was 16.33 ± 5.72 months (range, 12 to 36 months). Mean preoperative spherical equivalent (SE) refraction was –3.74 ± 1.27 D (range, −6.50 to –1.50 D) and −3.95 ± 1.20 D (range, −6.75 to −1.00 D) for LASIK and PRK, respectively.

Mean preoperative corneal pachymetry was 484.95 ± 6.65 μm (range, 470 to 498 μm) and 482.38 ± 10.73 μm (range, 453 to 499 μm) for LASIK and PRK, respectively. Flap thickness (intraoperative measurements after flap lifting with DGH 5100 Technology) was 69 to

Discussion

Preoperative CCT is a crucial parameter for successful outcomes in refractive patients. Several studies have correlated the preoperative CCT and flap thickness with the presence of post-LASIK corneal ectasia. There continues to be increasing concern regarding the relationship of corneal thickness and the induced corneal biomechanical alterations after refractive surgery.13

The average CCT has been found to range from 537 to 550 μm.14 Although evidence is lacking as to what is truly a safe

George Kymionis, MD, PhD, graduated from the Medical School of University of Athens, Greece and three years later he finished his first PhD (apoptosis in human carotid atheroma) in the same university. He worked as a fellow in Ophthalmology in Vardinoyiannion Eye Institute of Crete for several years in which he finished his second PhD (ocular rigidity in AMD patients). Dr Kymionis has concluded his residency training in the University Hospital of Crete, and currently he is doing a fellowship in

References (19)

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Cited by (52)

  • Evaluation of the percentage tissue altered as a risk factor for developing post-laser in situ keratomileusis ectasia

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    These analyses increased our awareness and concerns about the risk for ectasia. In time, several studies of the ERSS8,27,33,42–46 seemed to show that on an individual basis, preoperative corneal thickness, thick LASIK flaps, and residual bed thickness do not individually predict the risk for ectasia. The effect of preoperative patient age remains controversial because whereas 1 study did not find it important,1 a recent presentation of an analysis from the Optical Express database by SchallhornA suggests it is.

  • Biomechanical properties of early keratoconus: Suppressed deformation signal wave

    2017, Contact Lens and Anterior Eye
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    However, there are still unknown facts, especially in regard to cases of post-surgical ectasia who had a residual stromal bed (RSB) >250 μm after keratorefractive procedures [3,4]. On the other hand, there have also been cases with RSB less than 250 μm who did not develop any post-operative complications [5,6]. Current protocols for the preoperative evaluation of surgical candidates includes special attention to their corneal topography and thickness.

  • Association between the percent tissue altered and post-laser in situ keratomileusis ectasia in eyes with normal preoperative topography

    2014, American Journal of Ophthalmology
    Citation Excerpt :

    In contrast, reports of successful LASIK in patients with thin corneas inversely support the role of percent tissue altered in ectasia risk. Table 6 lists recent studies26–28 investigating safety of LASIK in thin corneas that have sufficient data published to calculate percent tissue altered; in each of these reports, even though the authors were not specifically using the percent tissue altered equation, the mean percent tissue altered value was significantly lower than 40 and therefore was most likely within the safety limits for LASIK even in thin corneas. With surface ablation the chances of having percent tissue altered greater than 40 are quite low, and studies have also shown that surface ablation is safe to treat either high corrections or thin corneas26–30 (Table 6).

  • Corneal Parameters in Patients with Multiple Sclerosis: A Pilot Study

    2022, Klinische Monatsblatter fur Augenheilkunde
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George Kymionis, MD, PhD, graduated from the Medical School of University of Athens, Greece and three years later he finished his first PhD (apoptosis in human carotid atheroma) in the same university. He worked as a fellow in Ophthalmology in Vardinoyiannion Eye Institute of Crete for several years in which he finished his second PhD (ocular rigidity in AMD patients). Dr Kymionis has concluded his residency training in the University Hospital of Crete, and currently he is doing a fellowship in Bascom Palmer Eye Institute in Miami, Florida.

Sonia H. Yoo, MD, is a corneal and refractive surgeon at Bascom Palmer Eye Institute in Miami, Florida. Dr Yoo is an Associate Professor of Clinical Ophthalmology and serves as the cornea fellowship director at Bascom Palmer Eye Institute of the University of Miami Miller School of Medicine.

See accompanying Editorial on page 284.

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