Vision Correction for Myopia and Astigmatism in Patients with Thin Corneas

HO CHI MINH CITY – Unable to undergo laser vision correction because her corneas were too thin, Linh, 24, was advised by doctors to undergo implantable collamer lens (ICL) surgery to improve her vision after living with myopia and astigmatism for more than a decade.

According to her medical records, Linh had 8 diopters of myopia with 4.5 diopters of astigmatism in her right eye, while her left eye had 6 diopters of myopia and 3 diopters of astigmatism. During uncorrected visual acuity testing, she could only count fingers at a distance of approximately 2–4 meters. As her work in the aviation industry requires good vision, Linh began exploring treatment options that could reduce her dependence on eyeglasses.

MSc. MD. Pham Huy Vu Tung, Deputy Head of the Department of Ophthalmology at the High-Tech Eye Center, Tam Anh General Hospital in Ho Chi Minh City, said the patient’s corneal thickness was only 310 micrometers, considerably below the minimum threshold of approximately 500 micrometers required for conventional laser procedures. However, following a comprehensive ophthalmic examination, the medical team determined that her refractive error was stable and that there were no signs of elevated intraocular pressure or corneal scarring, making her eligible for Phakic ICL surgery.

Dr. Tung explained that the procedure involves implanting a lens behind the iris and in front of the eye’s natural crystalline lens through a small incision of approximately 3 mm at the edge of the cornea. The implanted lens is extremely thin, measuring approximately 2.2–2.8 mm, and is made from a soft, flexible material similar to that used in contact lenses. It is customized according to each patient’s ocular measurements and imported from Europe. One of the key advantages of this technique is that it does not alter the thickness or structure of the cornea, making it particularly suitable for patients with thin corneas or high degrees of myopia and astigmatism. The procedure also offers a high success rate and a relatively short recovery period.

Linh undergoes refractive testing before surgery. Photo: Tam Anh General Hospital

According to the doctor, Phakic ICL surgery can address a relatively wide range of refractive errors, including myopia of up to 18 diopters, hyperopia of up to 10 diopters, and astigmatism of up to 6 diopters, and is intended for patients aged 21–45. In certain circumstances, an implanted lens can be replaced with a new one if the patient’s refractive parameters change. The lens is made from collamer, a combination of collagen and polymer with good biocompatibility, making it suitable for people who frequently travel by air, such as Linh.

One week after surgery, a follow-up examination showed that Linh’s uncorrected visual acuity had reached 10/10 in both eyes. Dr. Tung noted that patients with thin corneas require careful postoperative monitoring. They should avoid strenuous activities during the first few days, refrain from rubbing their eyes or engaging in vigorous exercise, limit prolonged periods of bending their head downward, and strictly follow their scheduled follow-up appointments. If unusual symptoms occur, such as eye pain or flashes and spots resembling “floaters,” patients should seek medical attention immediately.

The doctor also noted that people aged 18 and above who have stable refractive errors, no underlying eye diseases, and wish to undergo vision correction may have several treatment options available, including Phakic ICL, LASIK, and SMILE. Before choosing a procedure, patients should undergo comprehensive preoperative screening to assess corneal thickness and structure as well as the amount of residual corneal tissue expected after treatment. Based on these measurements, the ophthalmologist can recommend the most appropriate technique, with priority given to less invasive approaches that preserve as much corneal tissue as possible.