Central islands are steep spots on the cornea after LASIK. Reported causes of central islands include shielding of the corneal bed by pulverized tissue plume, collection of fluid in the center of the cornea as the ablation is performed, non-homogenity of the laser beam, regional differences in corneal hydration, and large ablation diameters. Central islands are more common with first- and second-generation laser systems.
Symptoms include ghost imaging, halos, starbursts, night-driving disability, reduced best-corrected visual acuity, loss of contrast sensitivity, and double vision.
Central islands after LASIK generally do not resolve on their own. Hard contact lenses may be required for visual rehabiliation.
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Medical articles about central islands after LASIK
J Refract Surg. 2003 May-Jun;19(3):309-15.
Proper positioning of the plume evacuator in the VISX Star3 excimer laser minimizes central island formation in patients undergoing laser in situ keratomileusis.
Cua IY, Pepose JS.
Pepose Vision Institute, Chesterfield, MO 63017, USA.
PURPOSE: To identify risk factors in a series of patients who developed steep central islands after laser in situ keratomileusis (LASIK).
METHODS: We analyzed and compared the refractive and topographic outcome of a study group composed of 83 eyes of 44 patients who underwent LASIK using the VISX Star3 excimer laser with a refraction-matched control group of 83 eyes treated later. The vacuum aspirator of the excimer laser was abnormally positioned during the surgeries performed in the study group.
RESULTS: Mean preoperative spherical equivalent refraction in the study group was -6.75 +/- 2.50 D. Four eyes with a mean preoperative spherical equivalent refraction of -9.27 +/- 2.29 D developed steep central islands. Thirty-three (38%) of 83 eyes treated needed retreatment for residual myopia or myopic astigmatism. In the control group, mean preoperative spherical equivalent refraction was -6.76 +/- 2.50 D. Ninety-three percent of eyes were within +/- 1.00 D of target refraction. Five (6.02%) of 83 eyes required retreatment and no eyes developed central islands.
CONCLUSION: The abnormally positioned vacuum aspirator coupled with the higher preoperative refractive correction were the likely causative factors for central island formation and the increased incidence of undercorrection in these patients.
J Cataract Refract Surg. 2000 Dec;26(12):1742-7.
Large optical ablation zone using the VISX S2 smoothscan excimer laser.
Haw WW, Manche EE.
Stanford University School of Medicine, Department of Ophthalmology, Stanford, California, USA.
PURPOSE: To prospectively evaluate the safety and efficacy of the new large-zone (6.5 mm) photoablation technology using the VISX S2 Smoothscan excimer laser.
SETTING: University-based hospital, Stanford, California, USA. METHODS: Forty-two eyes of 21 patients with a mean preoperative spherical equivalent (SE) of-5.55 diopters (D)+/- 2.24 (SD) (range-2.13 to-10.75 D) had laser in situ keratomileusis (LASIK) using the VISX Smoothscan S2 excimer laser for simple myopia or compound myopic astigmatism. A 6.5 mm optical zone was used in all eyes. Patients were prospectively followed 1 day and 1 and 3 months postoperatively.
RESULTS: At 3 months, the mean SE was reduced 94% to-0. 31+/- 0.55 D. Ninety-one percent of eyes had an uncorrected visual acuity of 20/40 or better. Eighty-eight percent were within+/-1.00 D of attempted correction and 84%, within +/-0.50 D. Stability within+/-0.50 D occurred after the first postoperative month. Vector analysis of eyes that had toric ablations demonstrated a difference vector within+/-1.00 D in 100% of eyes. The mean angle of error was-0.04+/- 6.37 degrees. Visually significant steep central islands associated with loss of best spectacle-corrected visual acuity was observed in 7.5% of eyes at 1 month. No eyes experienced significant glare or halos.
CONCLUSIONS: The new large-zone (6.5 mm) photoablation technology with the VISX S2 Smoothscan resulted in effective reduction of simple myopia and compound myopic astigmatism. However, with the 6.5 mm zone, there may be an increased risk of developing symptomatic steep central islands in the early post-LASIK period compared with the standard 6.0 mm treatment zone.
J Cataract Refract Surg. 2000 Jun;26(6):853-8.
Natural history of central islands after laser in situ keratomileusis.
Tsai YY, Lin JM.
Department of Ophthalmology, China Medical College Hospital, (Tsai), Taichung, Taiwan.
PURPOSE: To assess the incidence and natural history of central islands following laser in situ keratomileusis (LASIK) and evaluate the association of central island characteristics with visual acuity.
SETTING: Department of Ophthalmology, China Medical College Hospital, Taichung, Taiwan. METHODS: A consecutive series of 406 eyes of 212 patients who had LASIK was retrospectively evaluated. Uncorrected visual acuity (UCVA) was measured and corneal topography performed preoperatively and 1 week and 1, 3, 6, and 9 months postoperatively. Best spectacle-corrected visual acuity (BSCVA) was evaluated preoperatively and 1, 3, and 6 months postoperatively.
RESULTS: The topographic images obtained at 1 week demonstrated central islands in 23 eyes of 20 patients (5.7%). No new cases of central island formation were identified after 1 week. Of the 23 eyes with central islands, the 6 month post-LASIK maps were available in 20 eyes of 18 patients. There was a significant difference in the size and power of the central islands between 1 week and 6 months. However, the power and size decreased slowly. Within 6 months, only 5 of 20 central islands (25.0%) had resolved. Eight eyes were undercorrected, and 1 eye lost 2 lines of BSCVA. Central islands larger than 1.8 mm or 3.0 diopters (D) were significantly correlated with lower UCVA.
CONCLUSION: Most central islands that occur with LASIK persist more than 6 months. Large central islands (>/=1.8 mm or >/=3.0 D) are risk factors for lower UCVA. Preventive measures are necessary.
J Cataract Refract Surg. 2000 Apr;26(4):536-42.
Clinical analysis of central islands after laser in situ keratomileusis.
Kang SW, Chung ES, Kim WJ.
Department of Ophthalmology, Samsung Medical Center School of Medicine, Sungkyunkwan University, Seoul, South Korea.
PURPOSE: To analyze the incidence and clinical characteristics of central islands after laser in situ keratomileusis (LASIK) and to elucidate factors associated with their formation.
SETTING: Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
METHODS: Laser in situ keratomileusis was performed in 103 eyes of 61 patients with myopia ranging from -4.0 to -13.5 diopters (D) using the Hansatome (Chiron) and SVS Apex Plus (version 3.2.1) excimer laser (Summit Technology) in which the anti-central-island program was implemented. After 1 week, corneal topography (Orbscan, Orbtek) was done and manifest refraction and visual acuity were measured.
RESULTS: Postoperatively, the mean uncorrected visual acuity (UCVA) and best corrected visual acuity (BCVA) were 0.12 and 0.06 (logMAR scale), respectively, and the mean refractive error (spherical equivalent) was 0.07 D +/- 0.76 (SD). On topographic examination, a central island was defined as an area of higher refractive power of more than 1.5 D and 2.5 mm or more in diameter. Budding or isolated central islands were observed in 12 eyes of 12 patients (11.7%). The peak, height, and area of the islands were 41.5 +/- 3.1 D, 5.6 +/- 1. 9 D, and 3.5 +/- 1.1 mm(2), respectively. In the eyes with central islands, there were statistically significant differences in the postoperative change in UCVA and BCVA (P <.05). There was no significant correlation between the occurrence of a central island and preoperative refractive error, corneal thickness, age, or in sex and correction of astigmatism (P >.05).
CONCLUSION: Despite use of the anti-central-island pretreatment program, the occurrence of central islands after LASIK was significant, as in photorefractive keratectomy. Further studies of the effect of central islands on surgical results and clinical progress and measures to prevent the occurrence are needed.
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