Importance of Preoperative Pupillary Reflex in Traumatic Optic Neuropathy

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J Korean Neurosurg Soc. 2025;68(1):19-24

Publication date (electronic) : 2024 August 13

doi : https://doi.org/10.3340/jkns.2024.0083

Min Ho Lee, Tae-Kyu Lee

Department of Neurosurgery, Uijeongbu St. Mary's Hospital, School of Medicine, The Catholic University of Korea, Seoul, Korea

Address for reprints : Tae-Kyu Lee Department of Neurosurgery, Uijeongbu St. Mary’s Hospital, School of Medicine, The Catholic University of Korea, 271 Cheonbo-ro, Uijeongbu 11765, Korea Tel : +82-31-820-3796, Fax : +82-31-820-5378, E-mail : magpie67@catholic.ac.kr

Min Ho Lee Department of Neurosurgery, Uijeongbu St. Mary’s Hospital, School of Medicine, The Catholic University of Korea, 271 Cheonbo-ro, Uijeongbu 11765, Korea Tel : +82-31-820-3796, Fax : +82-31-820-5378, E-mail : minho919.lee@catholic.ac.kr

Received 2024 April 15; Revised 2024 June 10; Accepted 2024 August 12.

Abstract

INTRODUCTION

Traumatic optic neuropathy (TON) refers to a pathological condition caused by direct or indirect injury to the optic nerves. Direct TON results from anatomical disruption of the optic nerve, for example a projectile penetrating the orbit and impinging on the optic nerve. Successful treatment of direct TON is challenging. Meanwhile indirect TON is caused by the transmission of force on the optic nerve from a distant site without disruption of normal tissue structures, which tends to yield better outcomes. TON occurs in 0.5–5% of patients with traumatic head injury [1,3]. Many researchers have studied both direct and indirect TON and reported various surgical and medical treatments [4-6,8,13].

The optic nerve can be classified into four portions, depending on location : 1) intraocular, 2) intraorbital, 3) intracanalicular, and 4) intracranial. Among them, the intracanalicular portion is tightly bound within a confined space, and the optic nerve’s dural sheath fuses with the periosteum inside the optic canal. As a result, the intracanalicular portion is more susceptible to indirect injury than other portions. This portion is also where surgical treatment is frequently attempted. Previous researchers suggested that early decompression is essential factor to a good prognosis. In practice, TON patients encountered by physicians often also exhibit traumatic brain injury, as mentioned above. In the case of patients with traumatic brain injury, adequate vision evaluation is difficult in many cases due to altered mentality.

In order to address this problem, we investigated preoperative pupillary light reflex in TON patients as a predictive factor of surgical outcomes after optic nerve decompression.

MATERIALS AND METHODS

The study protocol was reviewed and approved by the Institutional Review Board (IRB) of The Catholic Medical Center (IRB No. UC22RISI0014) and the need for informed consent was waived due to the retrospective nature of the study.

From April 2020 to September 2022, we enrolled patients who were diagnosed with TON and underwent endoscopic optic nerve decompression at our institution. Among patients with craniofacial trauma, 1) patients who were fully alert and able to complain of visual deterioration, 2) patients whose vision was at a level below which hand motion could be detected, and 3) those with a fracture line of the optic canal on the side with decreased vision identified on computed tomography (CT) scan underwent optic nerve decompression. Patients who were unable to adequately describe their vision due to confusion were excluded.

Vision and pupil reflex tests were performed by an ophthalmologist before and after surgery. Outcomes were defined as “good” when patient vision improved to serviceable status (the patient could count fingers ≥30 cm to near-normal vision), as “fair” when there was postoperative improvement but not to the level of serviceable vision, and as “poor” when there was no difference compared to before surgery [10].

After fully explaining to the patient and/or guardian that the surgery may not restore vision and that vision may worsen even after surgery, informed consent was obtained and surgery was performed.

RESULTS

From April 2020 to September 2022, seven patients were enrolled. Their ages ranged from 9 to 78 years and all were male. Five cases reported acute onset, and complained of decreased vision in the emergency room. Two cases (cases 1 and 4) involved delayed onset, with vision deterioration reported 4 and 5 days after trauma, respectively.

Two patients had light perception but were unable to see hand motion, and the other five patients could not perceive light. Prior to surgery, on pupillary light reflex examination, the direct reflex of the affected site was prompt in three patients, sluggish in two, and absent in two patients. Additionally, the indirect reflex on the contralateral side was prompt in five patients, sluggish in one patient, and absent in one patient. All patients underwent steroid treatment (methylprednisolone 250 mg qid for 4 days) right after deterioration of visual acuity. All patients underwent endoscopic endonasal optic nerve decompression. The median time from onset of decreased vision to surgery was 20 hours (range, 4 hours to 10 days). The median follow-up period from surgery to the last outpatient visit was 16 months (range, 2–34 months). On the last visual acuity test performed at the last outpatient visit, five patients had recovered to a “good” level (serviceable vision; uncorrected visual acuity 0.5, 0.4, 0.3, and finger count at 50 cm), one patient to a “fair” level (light perception), and the remaining two patients no light perception. There were no complications from steroid treatment or surgery in any patients (Fig. 1 and Table 1). Among the seven patients, the patient whose pupillary light reflex was sluggish with 6 mm-sized pupil and absent with 7 mm-sized pupil before surgery showed no improvement in vision. Patients with some response to direct reflex or contralateral indirect reflex testing preoperative showed vision improvement postoperative (Fig. 2).

Fig. 1.

Pre (left of A-G) and postoperative (right of A-G) computed tomography of enrolled patients. All patients underwent endoscopic endonasal optic nerve decompression. D : Patient 4 underwent surgery on the right side, and the other patients underwent surgery on the left side. A fracture around the optic nerve was confirmed in all cases, and as much bone was removed from around the optic nerve as possible. Yellow arrows indicate fracture line near the optic nerve.

Table 1.

Changes in visual function after endoscopic optic nerve decompression

Fig. 2.

Improvement in visual acuity after endoscopic optic nerve decompression according to the interval from detection of visual deterioration to the start of surgery and pupillary light reflex. UCVA : uncorrected visual acuity, FC : finger count, HM : hand motion, LP : light perception, p : prompt, s : sluggish, f : fixed.

DISCUSSION

In this study, endoscopic optic nerve decompression was performed on seven patients with TON, and five patients showed improvement. Four patients showed good improvement to serviceable vision, and one patient showed fair improvement. All five patients who showed improvement had positive pupillary light reflex before surgery; the two patients who showed no improvement had negative pupillary light reflex before surgery.

Optic nerve decompression in TON patients remains controversial. A meta-analysis conducted in 1996 reported that active surgical intervention had more benefits than risks in 244 cases [2]. However, the International Optic Nerve Trauma Study published in 1999 did not find any benefit of surgical decompression in 133 TON patients [7]. In a situation where no conclusion has yet been reached, it seems difficult to completely deprive the opportunity to improve through surgery. In addition, a recent systematic review contended that there is no convincing evidence that steroids provide any additional benefit, but rather increase the risk of complications in patients with TON [15]. However, this does not mean that steroids are banned in patients with TON. There was only one study that met the selection criteria of this review article; a double-masked, placebo-controlled, randomized trial. Comparing other previous papers, finding the effectiveness of steroids was difficult. Therefore, it is recommended that steroids be used with caution. All patients enrolled in this study received steroids immediately after their vision deterioration, and no complications related to steroid treatment were observed. Due to the nature of TON, it is difficult to conduct a well-organized randomized control study; thus, it is expected that the debate over appropriate treatment will continue. Therefore, the surgeon has no choice but to perform the surgery as safely as possible.

The Northern Finland Birth Cohort study found an average annual incidence of traumatic brain injury of 188/1000000 [12]. Among those aged between 16 and 34, 67.4% were mild traumatic brain injuries, but 12.5% were moderate to severe, and 20.1% were fatal [12]. A considerable number of traumatic brain injuries are initially accompanied by decreased consciousness. In severe cases of diffuse axonal injury, coma duration is longer than 24 hours. In such cases, TON cannot receive timely treatment. There might be many patients who miss the opportunity for timely treatment and vision recovery due to altered mentality. Further research on TON soon after injury is also needed to further explore the natural course of this injury. Seiff [9] reviewed CT scans of TON cases, and approximately half of all TON cases had an associated bone fracture around the optic nerve. This may the cause of an indirect measure of the significant compressive forces involved. And, vice versa, the presence of such a fracture may thus be an indication of TON.

In the present study, all patients with intact pupillary reflexes showed improvement, and vice versa, all patients without reflexes showed no improvement. The authors would like to suggest that the presence of the pupillary reflex is an important prognostic factor that can predict the improvement of a patient’s vision. The previous study showed similar results [11]. Thus, we recommend that pupillary light reflex be checked in unconscious patients suspected of having TON to facilitate timely treatment. Pupillary reflex can be checked in unconscious patients. Comprehensive evaluation should include not only the direct but also the indirect reflex. If ipsilateral third nerve damage is present, the response in not reliable even if there is input through the ipsilateral optic nerve. However, if the contralateral oculomotor nerve is preserved, there will be a response in the indirect pupillary reflex measured on the contralateral side. To compensate for this, the indirect pupillary reflex related to the contralateral third nerve can be checked also.

This study enrolled a small number of subjects, which made it difficult to derive statistical significance. However, in previous studies, the importance of treatment for TON was focused on early surgery. Considering the pupillary light reflex of unconscious patients is an important aspect of this study. Based on our results, even when it is difficult to check visual acuity due to lack of consciousness, if there is a fracture around the optic canal on imaging, and the direct and/or indirect pupillary reflex is reactive, optic nerve decompression should be performed.

CONCLUSION

Direct and indirect pupillary reflexes can be important factors determining treatment for TON. In unconscious patients with a fracture involving the optic canal, timely surgical intervention based on pupillary reflex can prevent permanent loss of vision.

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