Intralimbal GP Fit on a Post-Lasik Central Island

History

Patient is a 45-year-old physiotherapist in Rio de Janeiro. He had laser-assisted in situ keratomileusis (LASIK) in 2013 to correct hyperopia. Six months later, he developed halos, monocular diplopia, and ghost vision. The first attempts to correct the optical aberrations with GP contact lenses were unsuccessful; he could not tolerate them, and the visual outcome was poor.

The patient traveled presented to our clinic for specialty GP lens fitting.

Corneal Biomicroscopy

Slit lamp examination was performed on both eyes. The patient presented clear corneas with no visible haze, although with the cross-section view, it is possible to observe a central area with less transparency.

Corneal Anterior Tomography

Corneal anterior tomograpy maps utilized were: anterior sagittal curvature, anterior tangential curvature, anterior elevation, corneal thickness, and corneal density average.

The exam maps below show a central anterior elevation developed after the LASIK procedure and that both eyes still have a normal corneal thickness (Figures 9 and 13), which indicates that this is not a case of an iatrogenic keratectasia. The maps clearly indicate a case of a post-LASIK central island. The corneal density average shows the amount and measure of corneal opacity due to the procedure (Figures 10 and 14).

All anterior cornea maps clearly show the evidence of a central island that is responsible for the symptoms perceived by the patient. The anterior tangential and anterior elevation maps (Figures 7 and 9) confirm a central area of an abnormal aspect (Sahay et al, 2021).

The corneal thickness seems to be relatively normal and the cornea density average map show the area of treatment with some mild opacity. These patients tend to have more problems with daylight vision than with night vision. During the day or in a highly illuminated environment, the patient will perceive more symptoms due to the miosis. At night or in a less illuminated environment, the patient will have less symptoms due the mydriasis.

These complications may be associated with the photoablation or with the microkeratome and may occur presurgery or postsurgery (Urbano et al, 2007).

The central island is defined as a localized central area, larger than 1mm, surrounded by a 1D or more flatter area. This complication is generally associated with a large ablation diameter. There is a greater potential for the formation of central island following treatment with broad-beam lasers than with scanning lasers (Azar, 2001). The differential diagnosis of central islands includes irregular epithelial healing, increased corneal prolateness and progressive ectasia (Urbano et al, 2007).

The GP contact lens or scleral lens fitting are the best options to neutralize the aberrations originated by the central island irregularities. A new laser procedure may be attempted, but there is some risk involved, as more cornea stroma will be removed, which may induce other complications.

Contact Lens Fitting

Initial tests and evaluation were performed with aspheric GP lenses with 10.5mm diameter. The larger diameter was not sufficient to neutralize all the symptoms despite a better visual acuity (VA); visual quality was still bad. The patient used to wear GPs for many years; he insisted on GPs rather than scleral lenses.

Based on his tomography exam, both Ks and midperiphery readings were used to choose the base curve. When using only the Ks readings, the lens sag certainly would be elevated. We chose an intralimbal GP design. The parameters were:

His pre-surgery prescription was not known, but the patient shared that his vision became worst and hyperopia returned. With the GP intralimbal design fitting, his VA went from 20/40 to 20/15⁺ OD and OS.

The larger, intralimbal GP design with a larger optical zone allowed a perfect centralization, an optimal tear exchange, and even a fluorescein pattern. The optical aberrations were adequately corrected. The patient was happy with the result and with the comfort.

The final fitting outcome was excellent, providing an optimal tear exchange, minimal movement, and centralization (Figures 15 to 18).

The frontal images above were obtained right after application of fluorescein. The cross-section view gives an idea of how well aligned the lenses are on the entire corneal surface.

Conclusion

GP Intralimbal design lenses have an important place in some situations where scleral lenses or corneal GPs are not the best option. They may be applied in larger and advanced keratoconus, post-penetrating keratoplasty, post-trauma, high myopia, and post-refractive surgery. In most cases, it is possible to achieve a satisfactory fit. It should give the patient a better visual outcome, comfort, and maintain corneal physiological health.

It is important to keep in mind that larger diameter GPs, like the intralimbal designs, need to have a higher and larger peripheral eccentricity as the corneal periphery is commonly flatter than the central and mid-peripheral cornea.

REFERENCES:

1. Sahay P, Bafna RK, Reddy JC, Vajpayee RB, Sharma N. Complications of laser-assisted in situ keratomileusis. Indian J Ophthalmol. 2021 Jul;69:1658-1669.
2. Urbano A, Urbano A, Urbano I. Cirurgia Refrativa a Laser, 2nd edition. Cultura Medica. 2007:325-327.
3. Azar DT. Managing a Central Island After LASIK. Cataract Refract Surg Today. 2001 Nov. Available at https://crstoday.com/articles/2001-nov/1101_06-html . Accessed Nov. 4, 2023.
4. Bastos L. Online Photo Diagnosis. Contact Lens Spectrum. 2021 Jun;36:13.

Mr. Bastos is the director and clinical instructor of specialty contact lenses at the Instituto de Olhos Dr. Saul Bastos (IOSB) and is the director and specialty lens consultant of Ultralentes, a small laboratory specializing in GP and scleral lens designs in Porto Alegre, RS, Brazil.