Introduction: Glaucoma is a degenerative disease in the optic nerve with associated visual field defects (VFD). Trabeculectomy is the most common glaucoma surgery. Surgery is indicated if glaucomatous optic neuropathy progresses despite tolerated medical treatment or in patients with severe VFD. The purpose of this paper is to describe the severity of visual field damage in patients undergoing their first trabeculectomy in Iceland.

Methods: A retrospective review of medical records of all patients with open angle glaucoma that underwent first trabeculectomy at Landspítali University Hospital, from June 2013 to March 2016. Visual fields were examined by Octopus automated perimetry and the severity of glaucoma damage was staged according to the mean defect (MD).

Results: 86 eyes were included in the study, mean age 75 ± 11 years, 57% men. Patients used on average three IOP lowering medications. Mean MD at referral to surgery was 13.4 ± 7.7dB (min 0.8dB, max 26.2 dB), 21% had early glaucomatous damage (MD < 6dB), 23% moderate (MD 6-12 dB) and 56% severe (MD > 12).

Conclusion: VFD at referral to surgery varied from mild VFD to severe damage. Like clinical guidelines recommend, treatment seems to be individualized and the most common indication for surgery was increased VFD despite medical treatment. Mean MD at referral to surgery was high compared to other studies. Eyes with severe VFD had on average lower IOP and thinner cornea. This might indicate that great emphasis is placed on high IOP and perhaps too little emphasis on VFD and cornea thickness.

Table I  Demographics and characteristics in different stages of glaucoma.

Figure I Histogram showing distribution of visual field mean defect (MD value) before surgery. 

Figure II Box plot showing visual field mean defect (MD) distribution by reason for surgery. Patients that were referred to surgery because of intolerance to medication had lower MD than those that were referred because of VF deterioration (p < 0.05).

Figure III Histogram showing total number of IOP lowering medication taken at the time at referred to surgery. Includes IOP lowering drops and system medication (azetisolamide).

Figure IV Box plot showing visual field mean defect (MD) by number of drugs. There was no statistically significant difference between the groups.