Complications
The loss of BCVA (≥2 lines of vision) after intracorneal ring segment insertion has been found to be approximately 1% at 1 year postoperatively. Adverse events (defined as events that, if left untreated, could be serious or result in permanent sequelae) have been reported to occur in approximately 1% of patients. Reported adverse events include
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anterior chamber perforation
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microbial keratitis
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implant extrusion (Fig 4-7)
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shallow ring segment placement
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corneal thinning over Intacs (Fig 4-8)
Ocular complications (defined as clinically significant events that do not result in permanent sequelae) have been reported in 11% of patients at 12 months postoperatively. These complications include
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reduced corneal sensitivity (5.5%)
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induced astigmatism between 1.00 and 2.00 D (3.7%)
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deep neovascularization at the incision site (1.2%)
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persistent epithelial defect (0.2%)
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iritis/uveitis (0.2%)
Visual symptoms rated as severe and always present have been reported in approximately 14% of patients and may be related to large pupil diameter. These complications include
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difficulty with night vision (4.8%)
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blurred vision (2.9%)
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diplopia (1.6%)
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glare (1.3%)
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halos (1.3%)
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fluctuating distance vision (1.0%)
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fluctuating near vision (0.3%)
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photophobia (0.3%)
Fine white deposits occur frequently within the lamellar ring channels after Intacs placement (Fig 4-9). The incidence and density of the deposits increase with the thickness of the ring segment and the duration of implantation. Deposits do not seem to alter the optical performance of the ring segments or to cause corneal thinning or necrosis, although some patients are bothered by their appearance.
Intacs achieve the best results in eyes with mild to moderate keratoconus. The goals are generally to improve vision and reduce distortions and are determined on the basis of the degree of keratoconus. For example, a patient with mild keratoconus and a BCVA of 20/30 may have the goal of improved quality of vision in glasses or soft contact lenses. However, a contact lens–intolerant patient with more advanced keratoconus and a BCVA of 20/60 may have the goal of improved ability to wear a rigid gas-permeable (RGP) contact lens. For some advanced cases of keratoconus, such as eyes with keratometry values greater than 60.00 D, the likelihood of functional improvement of vision is lower than for eyes with flatter keratometry values. In such cases, despite the use of Intacs, a corneal transplant may be unavoidable. If required, penetrating or lamellar keratoplasty may be performed after Intacs placement.
Excerpted from BCSC 2020-2021 series: Section 13 - Refractive Surgery. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.