A one-point technique for per-operative corneal meridian identification: Corneal marking technique

Graefes Arch Clin Exp Ophthalmol (2013) 251:24812482 DOI 10.1007/s00417-013-2385-5

LETTER TO THE EDITOR

A one-point technique for per-operative corneal meridian identification

Corneal marking technique

Shane R. Durkin & Michael Goggin

Received: 3 March 2013 /Revised: 13 May 2013 /Accepted: 15 May 2013 /Published online: 29 May 2013 # Springer-Verlag Berlin Heidelberg 2013

Dear Editor,It is increasingly important for cataract and refractive surgery to achieve an emmetropic, astigmatic result. The efficacy of the many techniques that are available to achieve this is dependent upon the accurate identification of corneal meridia, to ensure the correct placement of corneal incisions or toric intraocular lenses.

In cataract surgery, the incision can be astigmatically active, with a recent paper demonstrating a mean surgically induced astigmatism (SIA) of 0.66 dioptres in patients undergoing biaxial microincisional cataract surgery with enlargement of one wound to 2.8 mm [1]. Surgically induced astigmatism can be used to the surgeons advantage to reduce small cylinder errors with on-axis incisions [2]. This is facilitated by the pre-operative marking of a known meridian on the cornea.

For our technique, we placed one drop of 1 % tetracaine hydrochloride (Minims, Bausch & Lomb, France) into the inferior fornix of the operative eye. The patient was then seated upright and instructed to look straight ahead (primary position) to avoid torsion brought on by postural change [3, 4]. The ophthalmic surgeon (MG), standing in front of the patient, then used the tip of a bevelled 25-gauge needle to mark the limbal epithelium with a radial vertical line at the most inferior point of the limbus. This line coincides with the 90 corneal meridian (Fig. 1a).

Following routine peribulbar anaesthesia and sterile preparation of the eye, the 90 mark on a Mendez ring (Geuder, Germany) was aligned with the epithelial mark on the limbus whilst viewing through the operating microscope (Fig. 1b/c). The ring was then centred on the cornea. To ensure centration, the ring was placed to expose equal strips of conjunctiva on the vertical meridian above and below the limbus and similarly on the horizontal meridian, nasal and temporal to the limbus (Fig. 1d). The appropriate corneal meridian could then be chosen.

The location of the main incision and paracentesis were measured at day 1 review using a slit lamp (HaagStreit, Germany), with 10 graticules marked on the platform indicating the rotation of the slit beam about the z-axis. The positions of the main wound and paracentesis were recorded in the case notes, and compared with the targeted axes noted in the operation record.

The technique was analysed for 41 patients who underwent phacoemulsification surgery by a single surgeon (MG) in the one centre. There were 24 right eyes (58.5 %) and 17 left eyes (41.5 %) operated upon. The majority (33,80.5 %) of the main incisions were created at either 0 or 180, and more than 78 % (32/41) of the paracenteses fell between 115 and 125.

Eighty-five percent (35/41) of the main wound incision sites were exactly aligned with their target site. Six main wounds (15 %) were misaligned by between 5 and 10. No main wound incisions were misaligned by more than 10. Misalignment was anti-clockwise from the intended site in all misaligned cases. Only four paracenteses (9.8 %) were 5 or more degrees away from the per-operatively recorded site. Each of these errors was made in favour of a more counter-clockwise position. There were two paracenteses that were on their per-operatively recorded merdia despite their associated main wounds being distant from their intended meridia.

The authors have full control of all primary data, and agree to allow Graefes Archive for Clinical and Experimental Ophthalmology to review the data upon request.

S. R. Durkin (*) : M. GogginDepartment of Ophthalmology, The Queen Elizabeth Hospital, Woodville Rd, Woodville South,South Australia, Australiae-mail: [email protected]

S. R. Durkin : M. GogginDiscipline of Ophthalmology and Visual Sciences, The University of Adelaide, North Terrace, Adelaide, South Australia, Australia

2482 Graefes Arch Clin Exp Ophthalmol (2013) 251:24812482

Fig. 1 a This photograph demonstrates the patient sitting upright while the limbal epithelium is marked by the ophthalmic surgeon, standing in front of the patient. The tip of a bevelled 25-gauge needle is used to make a radial vertical line on the epithelium at the most inferior point of the limbus, which coincides with the 90 corneal meridian. b The arrow in this photograph demonstrates the line of marked epithelium at the inferior limbus as viewed through the operating microscope. Alternatively, c shows a small subconjunctival haemorrhage at the inferior limbus. These marks identify the vertical meridian, which can then be aligned with the Mendez ring as described in the text. d This intra-operative photograph demonstrates the placement of the Mendez ring over the limbus in order to align the 90 meridian with the inferior corneal epithelial mark and/or subconjunctival haemorrhage

Techniques for marking the cornea are manifold but go unreported, and the efficacy of these techniques has not been investigated. Some authors have described a technique of corneal marking that involves ink [5]. We have found marking pens to have poor persistence, washing off the ocular surface within a short time of application. This results in an inability to correctly align the Mendez ring, and a greater potential for inaccurate alignment of corneal incisions. Marking with a needle provides a fixed point of reference that only fades with epithelial healing, to become

invisible at the day 1 review. Corneal marking with a needle has been described previously [6], but results were not reported, and our technique marks only one meridian.

This technique represents a simple method for accurately determining the vertical corneal meridian pre-operatively. This can then assist with the correct placement of on-axis wounds, limbal-relaxing incisions or toric intraocular lenses [7, 8] during cataract surgery. The technique may also be employed to guide excimer laser astigmatism treatments.

Conflict of interest There are no financial relationships to disclose.

References

1. Kaufmann C, Thiel MA, Esterman A, Dougherty PJ, Goggin M (2009) Astigmatic change in biaxial microincisional cataract surgery with enlargement of one incision: a prospective controlled study. Clin Experiment Ophthalmol 37:254261

2. Kaufmann C, Peter J, Ooi K, Phipps S, Cooper P, Goggin M (2005) Limbal relaxing incisions versus on-axis incisions to reduce corneal astigmatism at the time of cataract surgery. J Cataract Refract Surg 31:22612265

3. Smith EM Jr, Talamo JH (1995) Cyclotorsion in the seated and supine patient. J Cataract Refract Surg 21:402403

4. Smith EM Jr, Talamo JH, Assil KK, Petashnick DE (1994) Comparison of astigmatic axis in the seated and supine positions. J Refract Corneal Surg 10:615620

5. Allarakhia L, Thornton SP (1991) Ophthalmic pre-inked marking pad. J Cataract Refract Surg 17:374375

6. De Silva DJ, Ramkissoon YD, Bloom PA (2006) Evaluation of a toric intraocular lens with a Z-haptic. J Cataract Refract Surg 32:14921498

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8. Goggin M, Moore S, Esterman A (2011) Outcome of toric intraocular lens implantation after adjusting for anterior chamber depth and intraocular lens sphere equivalent power effects. Arch Ophthalmol 129:9981003