Case study: Obstetric forceps injury leads to Descemet’s membrane scar

Sub-Bowman keratomileusis was utilized in a 30-year-old man who had high cylindrical error secondary to birth trauma-related Descemet’s scars.

Amar Agarwal

Birth injuries to the eye occur due to placement of the forceps blade across the globe and orbit, leading to blunt trauma to Descemet’s membrane. This often results in a transient increase in IOP, leading to rupture of Descemet’s membrane, which heals later by scarring, leading to high astigmatism and often resistant amblyopia. We report a case of an adult who presented to us with bilateral birth trauma scars, amblyopia and high cylinder and underwent sub-Bowman keratomileusis with successful 1-year follow-up.

Case study

A 30-year-old man presented to us for LASIK in September 2009. He complained of poor improvement of vision in the left eye despite corrective glasses. He had a stable, documented refraction over the last 5 years and no systemic contraindications to LASIK. On slit lamp examination, deep vertical scars at the level of Descemet’s membrane were found in both eyes, more in the left compared with the right (Figure 1). The patient’s history was suggestive of poor vision in his left eye since childhood. The history was confirmed with the mother, who told us that she had a complicated forceps delivery and there were white opacities in both eyes of the child that resolved in a few weeks.

Figure 1. On slit lamp examination, deep vertical scars at the level of Descemet’s membrane were found in both eyes, more in the left compared with the right. Images: Agarwal A

The subjective refraction was –2.5 D of sphere and –1.0 D of cylinder at 20° in the right eye and +1.5 D of sphere –6.0 D of cylinder at 160° in the left eye. Best corrected distance visual acuity was 20/25 in the right eye and 20/80 in the left eye. A rigid contact lens trial with over-refraction resulted in no improvement in best corrected visual acuity. Anterior segment optical coherence tomography showed hyper-reflective scars at the Descemet’s level, more prominently in the left eye. Corneal topography obtained with an Orbscan IIz (Bausch + Lomb) revealed a keratometric power of 49.8 D/48.0 D (maximum/minimum) in the right eye and 51.9 D/46.7 D (maximum/minimum) in the left eye (Figure 2). The white-to-white diameter was 11.5 mm in the right eye and 11.4 mm in the left eye. IOP was 14 mm Hg in the right eye and 16 mm Hg in the left eye on applanation tonometry. The mean central pachymetry was 581 µm in the right eye (thinnest point: 572 µm) and 650 µm in the left eye (thinnest point: 604 µm). However, as Orbscan pachymetry is considered to be unreliable in cases with corneal scars, we performed ultrasonic pachymetry. The ultrasonic pachymetry was 575 µm in the right eye and 615 µm in the left eye. Specular count with the SP-2000P (Topcon Europe) was 2,311 cells/mm² in the right eye and 2,252 cells/mm² in the left eye. Posterior segment evaluation was uneventful.

Figure 2. Before and after corneal topography.

A diagnosis of Descemet’s scar secondary to birth trauma was made. After explaining alternative options and the risks and benefits of the excimer laser and femtosecond laser procedure, informed consent was obtained from the patient.

The patient underwent an uneventful 100-µm flap creation with the IntraLase 60 kHz femtosecond laser (Abbott Medical Optics) and successful iris recognition and dynamic eye tracking-based excimer laser photoablation with the Technolas 217z100 with ACE dynamic rotational eye tracking (Technolas Perfect Vision). The excimer ablation simulation was based on residual bed calculations of the ultrasonic pachymetry. A tissue-saving algorithm with iris recognition and dynamic rotational eye tracking was used in both eyes. Successful pre-ablation iris recognition and intraoperative dynamic tracking were done in both eyes. The cyclotorsional values were pre-ablation static cyclotorsion of +3.5° in the right eye and +2.1° in the left eye, and mean intra-ablation cyclotorsion of +3.3° in the right eye (ranging from +2.8° to +4.2°) and +1.8° in the left eye (ranging from +1.4° to +2.8°). Ablation in the right eye was linked throughout treatment to the diagnostic image; however, new image linkage was required intraoperatively for the left eye. There were no intraoperative complications.

At 1-month follow-up, uncorrected distance visual acuity was 20/25 in the right eye and 20/60-2 in the left eye. The residual refractive error was –0.5 D of cylinder at 140° in the right eye and –0.25 D of sphere and -0.75 D of cylinder at 10° in the left eye. Corrected distance visual acuity was 20/20 in the right eye and 20/60 in the left eye. The patient was followed for 1 year. Until the last follow-up, the refractive and visual outcomes were maintained. At 1 year, in October 2010, the uncorrected distance visual acuity was 20/25 in the right eye and 20/60-1 in the left eye. The residual refractive error was –0.25 D of sphere and –0.25 D of cylinder at 170° in the right eye and –0.25 D of sphere and –0.50 D of cylinder at 175° in the left eye. Corrected distance visual acuity was 20/20 in the right eye and 20/60 in the left eye.

Preoperative Orbscan had shown a topographic cylinder of –1.8 D at 3° in the right eye and –5.1 D at 159° in the left eye. At 1-year postoperative follow-up, the topographic cylinder was –1.0 D at 19° in the right eye and –0.7 D at 1° in the left eye (Figure 2). Specular count at 1 year was 2,244 cells/mm² in the right eye and 2,282 cells/mm² in the left eye.

The difference map between preoperative, 1-month and 1-year follow-ups showed fairly stable, predicted phoropter refraction and 2-D plots between the two postoperative follow-ups (Figures 3a and 3b). Anterior segment OCT with the Visante (Carl Zeiss Meditec) showed a stable Descemet’s scar and margins of the flap (Figure 4).

Figures 3a and 3b. The difference map between preop, 1-month and 1-year follow-ups showed fairly stable, predicted phoropter refraction and 2-D plots between the two postoperative follow-ups.

Figure 4. Anterior segment OCT showed a stable Descemet’s scar and margins of the flap.

Discussion

Descemet’s scar due to birth trauma is a challenging situation to manage. The combination of Descemet’s scar, amblyopia, and clinical signs and topographic pictures of high astigmatism can result in a wrong diagnosis of keratoconus with a healed hydrops. However, this entity is different from keratoconus because it has a normal corneal thickness and an essentially normal structure in the uninvolved cornea, as shown in confocal studies.

One of the concerns with a case like this can be the risk of late regression. One year of follow-up in this case showed that there was no evidence of regression or increase in the cylindrical refraction. A previous study with longitudinal follow-up of two children with birth trauma showed stability of myopic error in one case and decrease in the other. Our patient was an adult with a noted stable refraction for the last 5 years. He had corneal thickness in the high normal zone for our population cohort, and specular counts were normal in the preoperative and postoperative periods. The difference maps between 1 month and 1 year of follow-up did not show any clinically significant fluctuations.

To conclude, our study suggests that sub-Bowman keratomileusis for high cylindrical error secondary to birth trauma-related Descemet’s scars appears to have a stable, safe and effective follow-up over 1 year. However, longer follow-up and more cases are required to conclusively predict the usefulness of this procedure. A study is under way to look at the result of LASIK in pediatric cases with birth trauma scars at our center.

• Amar Agarwal, MS, FRCS, FRCOphth, is director of Dr. Agarwal’s Eye Hospital and Eye Research Centre. Prof. Agarwal is the author of several books published by SLACK Incorporated, publisher of Ocular Surgery News, including Phaco Nightmares: Conquering Cataract Catastrophes, Bimanual Phaco: Mastering the Phakonit/MICS Technique, Dry Eye: A Practical Guide to Ocular Surface Disorders and Stem Cell Surgery and Presbyopia: A Surgical Textbook. He can be reached at 19 Cathedral Road, Chennai 600 086, India; fax: 91-44-28115871; e-mail: dragarwal@vsnl.com; website: www.dragarwal.com.
• Disclosures: Prof. Agarwal is a paid consultant to Abbott Medical Optics and Bausch + Lomb. Drs. Prakash and Chari have no relevant financial disclosures.