Ocular complications, like loss of vision, are a rare postoperative finding in patients operated for spine conditions in the prone position with a reported incidence of 0.028 – 0.2% [1]. Anisocoria is even more infrequent. To the best of the authors' knowledge, only two such cases have been reported [2,3]. We want to share our experience in this regard.

A 71-year-old female patient suffered a slip and fall. She was bedridden due to severe pain in her lower back and weakness in her lower limbs. As her pain continued to worsen and could no longer be alleviated by oral medications, she was advised to X-ray the lumbosacral spine. The finding of fracture of the first lumbar (L1) vertebra and worsening pain prompted her to seek more specialized care.

On arrival at our center, she was examined and investigated thoroughly. Decreased power (3/5) at the hip, knee, and ankle were observed in bilateral lower limbs. Sensory, bladder, and bowel function were found to be intact. Tenderness in the epigastrium and right hypochondrium was elicited on systemic examination. Magnetic resonance imaging (MRI) of the lumbosacral spine confirmed compression fracture of the vertebral body of L1 vertebra with cord changes. Posterior cortical pulsion into the thecal sac at level of L1 and narrowed canal at the fourth and fifth lumbar vertebrae was also found. The patient was planned for eleventh thoracic to third lumbar vertebrae pedicle screw fixation with decompression at the level of L1 vertebra.

Pre-anesthetic workup involved a multidisciplinary approach. The patient had a history of cardiac stenting, and her echocardiography showed mild global hypokinesia and left ventricular ejection fraction of 40 %.  Antiplatelets were stopped before surgery. Conservative approach was advised by the general surgeon regarding cholelithiasis, while the endocrinologist started her on Tab Methimazole 5 mg twice a day for hyperthyroidism. 

She underwent a single session of dialysis for hyperkalemia. 

On the day of surgery, after obtaining requisite consents, the patient was shifted to the operating room, routine monitors were attached, and anesthesia was induced with Etomidate 0.2 mg/kg, Fentanyl 2 mcg/kg, Succinylcholine 1.5 mg/kg. Endotracheal intubation was done with cuffed flexo metallic tube sized 7.5 mm. The patient was positioned carefully in the prone position with padding of all the pressure points and free the abdomen.  The head was placed on soft gel foam at the heart level with avoidance of pressure on the eyes. All pressure points were meticulously padded. D11-L3 bilateral pedicle screw fixation and L1 laminectomy were done.

Dura was found to be thinned out and adherent to ligamentum flavum at L1. Primary dural repair was done because inadvertent durotomy occurred while doing decompression at L1. The surgery lasted for 3 hours. Intra-operatively, 1800 ml of crystalloids and four units of platelets were transfused. Urine output was 250 ml, and 250 ml of blood was lost during four hours of surgery. After the surgery, the patient was reversed with 2.5 mg neostigmine and 0.5 mg glycopyrrolate, extubated, and shifted to the intensive care unit for observation. At no point was atropine given to the patient.

Postoperatively patient's GCS was E4V5M6 with power same as preoperative status.No periorbital or facial edema was observed. Pupillary examination revealed that the left pupil was 4 mm in size, sluggishly reacting to light, while the right pupil was 2 mm reacting normally to light. The patient did not complain of decreased vision or diplopia. Her visual acuity was the same as before (right eye 6/12 and left eye 6/18). Intraocular pressure was 15 mm Hg in the right eye and 13 mm Hg in the left eye. In view of postoperative anisocoria, computed tomography (CT) head was obtained to rule out any intracranial pathology. No acute finding that would explain anisocoria was found. Intraocular pressure was 15 mm Hg in the right eye and 13 mm Hg in the left eye. Anisocoria improved spontaneously within 48 hours during her stay, and she was discharged on the sixth day postoperatively. The patient had no visual complaints or evidence of anisocoria during her follow-up visits.

REVIEW OF LITERATURE

To the best of our knowledge, only two similar cases have been published. 

In a case reported by Gupta [2] L4-5, L5-S1 micro-discectomy was done in a 48-year-old male patient. Blood loss of 200-300 ml was reported. Postoperatively patient complained of diplopia and blurred vision, and the left pupil was dilated (5mm). Parasympathetic postganglionic nerve injury causing segmental pupillary palsy was considered to be the probable cause of anisocoria. Corrective lenses were used, and the patient was discharged on the 11^th postoperative day with mild anisocoria.

In another case reported by Papaioannou [3] L1-S2 fixation, L5 decompression, Illizarov application for calcaneal fracture was done in a 23-year-old female. The surgery lasted about 4.5 hours. Postoperatively, the left pupil was found to be dilated, although the patient was asymptomatic. At 24hours after surgery, anisocoria resolved. Iris sphincter muscle tears were the probable cause of anisocoria.

Anisocoria may be drug-induced, or due to ocular trauma or consequent to intracranial pathology [4]. Transient oculomotor paralysis is the likely cause of postoperative anisocoria in our case. One should be aware of various causes of such findings and do a thorough pre-anesthetic workup. Highlights of updated recommendations by the American Society of Anesthesiologists task force on perioperative visual loss [5], to avoid ocular complications in the prone position after spinal surgeries, have been summarized in Table 1. Though rare, ocular complications lead to a physical and emotional challenge for the patients; therefore, clinicians should be vigilant about any such changes and scrutinize the aetiologies to prevent the same.

Table 1: Highlights of Updated Recommendations by the American Society of Anesthesiologists Task Force on Perioperative Visual Loss5

“High-risk patients" are defined as those who undergo spine procedures while positioned in prone position and who have prolonged procedures, experience substantial blood loss, or both (American Society of Anesthesiologists Task Force on Perioperative Visual Loss. 2012).

Although rare, ocular complications lead to a physical and emotional challenge for the patients; therefore, the clinician should be vigilant about any such changes and scrutinize the aetiologies to prevent the same.

Acknowledgment

• This case report was published with the written consent of the patient.

• The authors declare no conflict of interest and no source of external funding. 

1. Newman, N.J. “Perioperative Visual Loss after Nonocular Surgeries.” American Journal of Ophthalmology, vol. 145, no. 4, 2008, pp. 604–610, https://doi.org/10.1016/j.ajo.2007.12.019.

2. Gupta, P., et al. “Unilateral Mydriasis: A Complication of Spine Surgery in Prone Position.” Revista Brasileira de Anestesiologia, vol. 69, 2019, pp. 319–321, https://doi.org/10.1016/j.bjan.2018.12.003.

3. Papaioannou, I., et al. “Anisocoria after Posterior Spine Surgery: A Rare but Disastrous Complication—A Case Report and Literature Review.” Journal of Orthopaedic Case Reports, vol. 9, no. 4, 2019, p. 92, https://doi.org/10.13107/jocr.2250-0685.1380.

4. Lee, A.G., et al. “A Guide to the Isolated Dilated Pupil.” Archives of Family Medicine, vol. 6, no. 4, 1997, pp. 385–388, https://doi.org/10.1001/archfami.6.4.385.

5. American Society of Anesthesiologists Task Force on Perioperative Visual Loss. “Practice Advisory for Perioperative Visual Loss Associated with Spine Surgery: An Updated Report by the American Society of Anesthesiologists Task Force on Perioperative Visual Loss.” Anesthesiology, vol. 116, no. 2, 2012, pp. 274–285, https://doi.org/10.1097/ALN.0b013e31823c104d.