Jamie Ng, Marcus Tan, Lennard Thean National University Health System Case Report: Phacoemulsification Induced Transient Corneal Ectasia In A Rigid Gas Permeable Contact Lens User Jamie Ng, Marcus Tan, Lennard Thean National University Health System Singapore All authors do not have any financial interests

Purpose To report a case of transient induced astigmatism after 1.8mm micro-incision phacoemulsification surgery in a rigid gas permeable (RGP) contact lens (CL) user.

Introduction Corneal warpage includes changes in refraction, steepening or flattening of corneal curvature, resulting in an increase of regular or irregular astigmatism or a decrease in best corrected visual acuity. This is most often associated with the use of rigid gas permeable contact lenses. However, studies have shown that majority are transitory and regressive. The time estimated for stabalisation of corneal curvature after CL removal is typically thought to be 2 to 3 weeks. Hence, patients are advised for a 2 week CL holiday prior to any procedures.

Methodology Review of clinical findings in a 56 yr Chinese lady with moderate myopia with mild astigmatism (OD: -5.50/-0.75x135o; OS: -7.50/-1.00x65o) and moderate nuclear sclerotic cataract who underwent an uneventful left micro-incision (1.8mm) phacoemuslfication surgery. She had a 2 weeks CL holiday before pre-operative biometry assessment using the Zeiss IOL master. Noted to have pre-existing astigmatism of OS: -0.89DC@3o. Using the SRK/T formulation, an Arci.Tec +9.5D IOL was implanted in her left eye for a target refraction of emmetropia. She had post-operative refractive surprise, documented on corneal topography and clinical refraction that resolved completely and spontaneously after 1 month.

Results Following an uncomplicated phacoemulsification by an experienced surgeon, a refractive surprise of +3.50/-2.50x6o manifested on the 1st post-operative day. Clinical examination was unremarkable. Initial refractive surprise attributed to RGP lens should resolve in 2 weeks. At the 2nd post-operative week, there was still a significant subjective astigmatism (+0.75/-1.75x180o). This was confirmed with Orbscan showing astigmatism of -1.8D@11o and IOL master reading showing astigmatism of -1.74D@17o. However, at one and two months post-surgery, her refraction was noted to be PL/-0.25x5o and PL with the corroborative Orbscan and IOL master readings.

Results Visual acuity and refractive status of left eye Visual acuity Refraction Pre-operative 6 / 21  6 / 12 -750 / -100 x 65 POD 1 6 / 45  6 / 15 +300 / -200 x 10 POD 7 6 / 18 +300 / -250 X 10 POW 3 6 / 9 +075 / -125 x 180 POM 1 6 / 7.5 Plano / -025 x 5 POM 2 Plano

Corneal Topography Preoperative K on IOL master: (Off RGP lens for 2 weeks prior) K1: 40.42 @ 3°, K2: 41.31D @ 93° Cyl: -0.89 @ 3° Preoperative

Corneal Topography 1 Week Post-op 3 Weeks Post-op 2 Months Post-op Sim K: 3.25D @108 deg Max: 41.37D @108 deg Min: 38.12D @18 deg

Discussion Sub 1.8mm micro-incision phacoemulsification surgery is meant to minimise the surgically induced astigmatism. In patients who are long term RGP CLs users, the corneal bio-mechanics may be altered and lead to a post operative refractive surprise. In our patient, she had a 2 week CL holiday prior to biometry measurement that gave accurate readings. However, her post operative refractive surprise persisted longer than expected, suggesting another mechanism for the unexpected outcome. Hence we postulate that it was induced by the biomechinics of phacoemulsification. Phacoemulsification induced astigmatism is likely transient in nature and should resolve spontaneously. Surgical intervention can be considered if the astigmatism is persistent after 3 months.

Conclusion Long-term RGP CL alters corneal bio-mechanics that may lead to refractive surprises. In our patient, we postulate that phacoemulsification energy itself could have resulted in additional transient corneal ectasia by an unknown mechanism. Hence, any refractive intervention should be considered if the astigmatism persists 3 months after surgery.

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