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Cataract SURGERY Treating Cataracts and Irregular Astigmatism Irregular astigmatism can be addressed before, during, or after surgery, with the best choice depending on the patient’s individual characteristics. By Justin Schweitzer, OD C ataracts and irregular corneal astigmatism are conditions that are often encountered simultaneously by eye care providers. Conditions such as Salzmann nodular degeneration, pterygium, epithelial basement membrane dystrophy (EBMD), keratoconus, corneal ectasia, corneal scars, and ocular surface disease often induce irregular astigmatism.1,2 These conditions present additional challenges when cataract surgery is imminent. Depending on its cause and severity, irregular astigmatism can be addressed before surgery with phototherapeutic keratectomy (PTK), at the time of cataract surgery with astigmatic keratotomy (AK) or toric IOLs, or after surgery with specialty contact lenses. Each technology is indicated in different conditions and situations. Preoperative Evaluation A detailed cataract workup should be performed on all patients prior to surgery. Workups include corneal topography, optical biometry measurement to calculate IOL power, and evaluation of the anterior and posterior segments. Conditions such as keratoconus, corneal ectasia, and other subtle irregularities of the cornea are best discovered with corneal topography. Corneal topographers provide the best assessment of the degree of astigmatism present, its location, and the severity of the irregularity. Topographers also assist in obtaining accurate corneal curvature measurements that can be used in determining the correct IOL power for the patient. Salzmann nodular degeneration, pterygia, EBMD, corneal scars and other corneal dystrophies will usually be seen on slit-lamp examination, and the amount of astigmatism can be quantified with topography. If the irregularities are subtle and the astigmatism Figure 1. An 85-year-old patient presented with decreased vision (20/40) with a topography that is regular, the eye care exhibits irregular astigmatism and a questionable early keratoconic pattern. Anterior segment provider can move examination revealed significant ocular surface disease. forward with preparing July/August 2014 Advanced ocular care 1 Cataract SURGERY Treatment of Irregular Astigmatism at the Time of Cataract Surgery Toric IOLs and AK are important tools in the arsenal for treating cataracts and astigmatism at the time of surgery.6 The arcuate incisions used in AK can be a powerful tool for correcting regular astigmatic corneas, but when the cornea is irregular they can further destabilize the cornea and cause more irregularities.7 Toric Figure 2. Same patient as Figure 1 after 4 weeks of aggressive dry eye treatment. The irregularity of the IOLs have the ability cornea has decreased, and it is now beginning to have a more symmetric, regular topographic pattern. to correct 1.00 D to slightly the patient for cataract surgery. In situations in which more than 4.00 D of astigmatism.6,8 These implants the irregularities are significant, treatment may be necwork best in eyes that have regular astigmatism, but in essary before surgery to facilitate accurate IOL power some situations they can be used in eyes that have a calculations. mild amount of irregular corneal astigmatism. Patients with mild irregularities who have recently Treatment of Irregular Astigmatism done well with spectacle correction are good candibefore Cataract Surgery dates to consider for a toric IOL. Those who achieve Accurate IOL power calculations can be difficult to good vision with spectacles have fairly regular and symobtain with many conditions that cause irregular astigmetric corneal astigmatism, as eyeglasses will not fully matism. In certain situations, treating the corneal surface correct irregular astigmatism.9 Certain corneal conditions that show irregularities first and then repeating IOL calculations and corneal topography maximizes accuracy. Patients with advanced on corneal topography, such as mild keratoconus and mild corneal ectasia, can also do well with a toric IOL. Salzmann nodules or EBMD may benefit from a PTK to Evaluating the central 3 to 5 mm on corneal topograreduce the irregularities of the corneal surface.3,4 Ocular surface disease can cause significant changes to the corphy helps to determine the degree of irregularity overneal surface and should be treated aggressively before lying the pupil. Regardless of irregularities in peripheral cataract surgery (Figures 1 and 2).2 A pterygium can zones, if the central 3- to 5-mm zone is reasonably induce several diopters of irregular astigmatism, and it regular the patient will likely do well with a toric IOL may warrant surgical removal before moving forward (Figure 3).10 5 with cataract surgery. Treatment of Irregular Astigmatism Once these conditions are treated, repeating IOL calAfter Cataract Surgery culations and corneal topography is necessary. In some Patients who present with keratoconus, corneal ectacases previously irregular corneas will return to a regular sia, corneal scars, and other irregularities may benefit astigmatic shape. The eye care provider can then profrom a specialty contact lens fitting after implantation ceed with choosing a surgical plan based on accurate of a nontoric monofocal IOL. Looking closely at corneal biometric data to ensure good patient outcomes. 2 Advanced ocular care July/August 2014 Cataract SURGERY (Figure 4). If the patient has previously worn a specialty contact lens, such as a rigid gas permeable (RGP) lens, and he or she wants to continue wearing contacts after cataract surgery, then a nontoric IOL may be the best choice for cataract surgery. If a toric IOL is implanted and the patient wants to continue wearing a specialty contact lens, the contact lens will mask the corneal astigmatism and thus unmask the lenticular astigmatism from the toric IOL. The design of the specialty contact lens would then Figure 3. Topography of a 49-year-old man with previous PKP preparing to have cataract surhave to have an anterior gery. Note the regularity of the central 3- to 5-mm zone. The decision was made to implant a toric surface to balance toric IOL because of the regular nature of the central 3- to 5-mm zone. out the unmasked toric IOL effect.11,12 Certain patients will present with corneas that are highly irregular or unstable. In these cases the eye care provider must decide if a specialty contact lens fitting will be possible after cataract surgery or if the patient would benefit from penetrating keratoplasty (PKP) with subsequent cataract surgery.13 A discussion with the patient is imperative to set expectations and determine the patient’s comfort level for proceeding with a specialty contact lens fitting after cataract surgery. If the eye care provider believes that an accurate contact lens fit will not be attainable or the patient does not have a desire to wear a contact lens, then PKP with subsequent cataract surgery will likely yield the best outcome, despite the long postoperative recovery. Figure 4. A 16-mm diameter scleral contact lens fit on a 47-year-old man with keratoconus who underwent cataract surgery. topography readings, considering any previous corneal surgery, and determining if the patient is capable of wearing a specialty contact lens will help in making this decision. Cataract surgery with a planned postoperative contact lens fitting can be a powerful tool in cases in which significant corneal irregularity exists but it is difficult to decide in what axis the toric IOL should be placed Case Study A 47-year-old man was referred to our center with complaints of decreased near and distance visual acuity, glare and halos at night. He had a history of keratoconus and successful RGP contact lens wear over the past 15 years. He wondered if a corneal transplant and cataract surgery would help his vision. Three years before the patient presented to our center, his BCVA with RGP contact lenses was 20/20 in the right eye and 20/60+ in the left. His BCVA at this visit was 20/40 in the right eye and 20/400 in the left. RGP July/August 2014 Advanced ocular care 3 Cataract SURGERY Figure 5. Topography OD showing keratoconus. Figure 6. Topography OS showing keratoconus. over-refraction improved the BCVA in his right eye to 20/20 but showed no improvement in the left. Brightness acuity testing was 20/400 in the right eye and was not performed in the left. Intraocular pressures were 7 mm Hg in the right eye and 8 mm Hg in the left. Ultrasound pachymetry was thin at 513 µm in the right eye and 534 µm in the left. Corneal topography (Pentacam; Oculus) confirmed 4 Advanced ocular care July/August 2014 significant keratoconus in both eyes (Figures 5 and 6). Examining the topographies closely showed inferior steepening in both eyes, and, more important, steepening and irregularity in the central 3- to 5-mm zone. Topography confirmed irregular, asymmetric astigmatism of nearly 10.00 D in the right eye and 6.00 D in the left. Anterior segment evaluation showed mild central scarring consistent with keratoconus in each eye. Examination through a dilated pupil revealed a 2+ posterior subcapsular cataract in the right eye and a 3+ posterior subcapsular cataract in the left. Examination of the fundus was normal. Properly addressing the irregular astigmatism was the key decision point in this case. A toric IOL was not the best option because of the significant irregularity of his cornea in the central 3- to 5-mm zone on corneal topography and the mild corneal scarring present centrally. A combined procedure of a corneal transplant plus cataract extraction is a consideration, but avoiding the morbidity of PKP would be desirable. Finally, cataract extraction followed by a specialty contact lens fitting postoperatively could be a likely solution. Because this patient had worn contacts successfully for the past 15 years and he has significant cataracts in both eyes, it was felt that there was a good chance removing his cataracts and fitting him with a contact would provide quality vision. The patient agreed, and uneventful cataract surgery was performed in the left eye. Three weeks postopera- Cataract SURGERY tively, the patient was successfully fit with a 16-mm diameter scleral lens in the left eye, and his subsequent BCVA was 20/20. Uneventful cataract surgery was then scheduled and performed in the right eye. Three weeks postoperatively a 16 mm diameter scleral lens was successfully fit in the right eye, and BCVA was 20/20. Conclusion Patients with cataracts and irregular corneal astigmatism present unique challenges in making cataract surgical decisions. Treatment of irregular astigmatism must be personalized for each patient. Treatment of irregular astigmatism preoperatively can be beneficial in obtaining more accurate IOL calculations. At times, patients with mild irregularities or asymmetry in the central 3 to 5 mm of the cornea will be able to move forward with surgery with consideration of implanting a toric IOL. In other cases, patients with significant irregular astigmatism may benefit from cataract extraction and a postoperative specialty contact lens fitting. It is crucial that eye care providers customize treatment for each patient with cataracts and irregular corneal astigmatism. If irregular astigmatism is properly addressed, successful surgical outcomes will be achieved to restore vision. n Justin Schweitzer, OD, is in practice at Vance Thompson Vision in Sioux Falls, South Dakota. He acknowledged no financial interest in the product or company mentioned herein. Dr. Schweitzer may be reached at [email protected]. 1. Basic and Clinical Science Course: External Diseases and Cornea. 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