Hyperopia and hyperopic astigmatism are less frequent in refractive patient population. Their excimer laser treatments became available in the mid-1990s thanks to new ablation profiles, focused on the midperiphery of the cornea [13].

Simple astigmatic hyperopic laser treatment results in a steepening of the flattest meridian with a midperipheral selective ablation (Fig. 10.3 and Video 10.1). Compound hyperopic photoablation includes an additional annular spherical treatment to correct the spherical part of the refraction (Fig. 10.4 and Video 10.1). As opposed to myopic treatment, hyperopic photoablation is located at the periphery of the cornea, with a 6.5–9 mm optical zone, in order to decrease the risk of regression and improve the postoperative quality of vision [14–16]. Theoretically, several ablation profiles can be applied depending on how we consider the sign of the spherical and cylindrical component of the refraction. However, with current laser platforms, simple and compound hyperopic astigmatic treatments tend to privilege a combination of positive cylinder and sphere notation, which implies a peripheral ablation and provides the best pattern to preserve the central cornea thickness with optimized stromal ablation depth [17].

The treatment of mixed astigmatism has been a significant challenge to refractive surgeons for quite some time. Incisional techniques, such as AK, were considered an adequate option to reduce astigmatism. In particular, they were used to correct mild and moderate degrees of astigmatism. However, they are reserved for patients with a spherical equivalent close to zero as it is known that arcuate incisions flatten the steep meridian with an associated flattening effect 90° away, on the flat axis, with a negligible coupling effect, leaving the spherical equivalent of the patient almost unchanged.

Excimer laser treatments for mixed astigmatism were developed at the end of the 1990s. This technology changed the surgical approach of mixed astigmatism, widening the pool of candidates and improving the refractive outcome. Mixed astigmatism ablation profiles are now based on a combination of previously detailed principles, a flattening of the steepest meridian and a steepening of the flattest one [18, 19].

Initially, first ablation patterns involved the use of a toric ablation to flatten the steep meridian, in combination with a hyperopic ablation to compensate for the residual hyperopic shift [20]. Other options included a steepening of the flat meridian combined with a myopic spherical ablation [8].

Subsequently, another ablation pattern, named bitoric LASIK, consisted of flattening the steep meridian doing a cylindrical ablation, in combination with a paracentral ablation over the flat meridian to steepen it. Its rationale was to provide the largest optical zone to prevent visual symptoms and to correct the hyperopic shift induced by the toric ablation over the steep meridian. Additionally, it compensated for the need of a spherical ablation to correct the residual myopia after the toric ablation of the flat meridian [21].

Current laser platforms optimize the treatment to reduce stromal depth ablation and provide an improved quality of vision. The ablation profile prioritizes peripheral hyperopic treatment combined with minimal central myopic treatment [10] (Fig. 10.5).

Astigmatic excimer laser surgery can be performed on refractive and cataract patients. Refractive patients must be older than 18 years of age and with a stable refraction for at least 1 year before surgery. Exclusion criteria for surgery are pregnancy and nursing, any active ocular or systemic disease affecting corneal healing, and keratoconus suspect. A minimal estimated residual posterior stromal bed of 250 μm is required to allow for LASIK technique and preserve corneal architecture integrity. Today, a more conservative 300 μm posterior stromal bed thickness limit has become more widely accepted. In cataract patients, photoastigmatic laser surgery is a valuable option when the postoperative refractive result needs to be fine-tuned. Incisional techniques can be used with success, with limited additional cost, when the residual refractive error is limited and the spherical equivalent is close to zero. For significant spherical or astigmatic refractive errors, LASIK can be performed 3 months after the surgery and provides excellent results. However, this technique has a certain cost, which implies a proper patient counseling preoperatively to guarantee patient satisfaction. Ideally, the astigmatism needs to be regular and symmetrical. In terms of magnitude, myopic and hyperopic astigmatisms can be corrected up to 6 D of cylinder. The latest laser platforms provide fast photoablation, thanks to high ablation rate, optimized ablation profiles with large optical and blend zones, and efficient rotational eye tracking systems able to compensate for cyclotorsional movements between seated and supine position and during the photoablation as well. Advances in excimer laser technology have significantly reduced the risk of postoperative haze after PRK. Surface ablation remains a primary indication in patients with thin corneas or asymmetrical astigmatisms, whenever LASIK is susceptible to expose the patient to a potential postoperative ectasia. The use of MMC during surface excimer laser ablation has proven to be safe and beneficial in terms of haze prevention, particularly for treatments superior to −4 to −6 D of myopia, astigmatism greater than 1.25 D, or ablation depth superior to 50–75 μm. The most important effect of MMC in preventing haze is inhibition of keratocyte proliferation [22]. Today, published studies agree on a standard concentration of 0.02%, with a brief exposition time of 10 s. The application of MMC must be confined to the central part of the cornea, and prevent any contact with the limbus and conjunctiva, to avoid reepithelialization delay (Video 10.1). A nomogram adjustment is recommended to avoid overcorrection, up to 8%, as the use of MMC minimizes the postoperative hyperopic regression during the reduced wound healing process [23].

Over the last 25 years, excimer laser treatment of astigmatism has become the technique of reference with excellent outcomes in terms of safety and predictability. Clinical results have certainly improved with technological evolutions. Constant improvements in laser platform software and hardware, coupled with surgical technique evolutions, such as PARK and then LASIK, have enabled more reliable photoastigmatic treaments and faster visual recovery.