COVID-19 is a systemic disease that causes symptoms throughout the body. The general symptoms of COVID-19 include cough, fever, sore throat, fatigue, headache, loss of taste, loss of smell, lower back pain, and muscle pain. This disease, transmitted through droplets, has led to a global pandemic . The first case in Turkey was detected on March 11, 2020. To prevent the spread of the disease, paying attention to personal hygiene, hand washing, wearing a mask, and social isolation have been recommended [3, 6].
Many countries in the world have had to resort to additional measures to tackle the COVID-19 pandemic, with the virus spreading rapidly, infecting many people, and resulting in millions of deaths. In Turkey, various measures have been implemented, including lockdowns, home quarantine, closure of shopping centers, reduction of public transportation use, closure of certain workplaces, and transition to home office working. Both the necessity of social isolation caused by the fear of contracting the virus and implemented lockdowns have resulted in a decrease in the rates of hospital visits [6, 7].
Units operating under ophthalmology outpatient clinics can be listed as cornea, uvea, glaucoma, retina, contact lens, strabismus, and oculoplasty . Among these units, the retina unit follows up patients diagnosed with retinal detachment, vitreous hemorrhage, epiretinal membrane, and macular holes, as well as those that have undergone vitreoretinal surgery due to retinal vascular diseases, such as diabetic retinopathy, retinal vein occlusion, retinal artery occlusion, and ocular ischemic syndrome. These patients should attends regular follow-up every three to six months. In patients with retinal vascular disease without follow-up, neovascularization may occur in the retina, and as a result neovascular glaucoma may develop [8–10]. If patients who have undergone vitreoretinal surgery and have had silicone tamponade inserted into the eye are not followed up regularly, and thus their silicone tamponade is not removed when necessary, it may emulsify over time and cause glaucoma by obstructing the trabecular meshwork [11–12].
Trabeculectomy is the gold standard surgical treatment in patients with glaucoma. This surgery aims to reduce intraocular pressure by creating a fistula between the subconjunctival area and the anterior chamber [13, 14]. The Ahmed glaucoma valve is a drainage device that uses a venturi valve mechanism to control excessive aqueous drainage into the posterior episcleral or subconjunctival area. It allows the aqueous to flow slowly through a chamber, and when intraocular pressure reaches the threshold value, the valve allows the fluid to exit the silicone tube, thus lowering intraocular pressure [15, 16].
In this study, we found a decrease in the total number of patients who presented to the retina unit and underwent glaucoma surgery in Group 3 compared to Groups 1 and 2. In addition, there was a decrease in the number of patients presenting to the retina unit in Group 4 compared to Groups 1 and 2. This decrease was due to the patients not attending their regular follow-up. We consider that the fear of contracting COVID-19 and dying, restrictions implemented to prevent the spread of the virus, and need for social isolation are effective in this situation.
Although the number of patients who presented to our retina unit was statistically significantly decreased in Group 4 compared to Groups 1 and 2, the number of those that underwent glaucoma surgery was higher. The ratio of the number of patients that underwent glaucoma surgery to the total number of those presenting to the retinal unit was statistically significantly higher in Group 4 than all the remaining groups. The number of glaucoma operations being higher in Group 4 compared to the remaining groups may be because many patients did not attend their necessary follow-up after March 11, 2020, when the first case of COVID-19 was reported in Turkey, and therefore they were not able to undergo timely interventions, such as anti-glaucomatous treatment, intravitreal injections, argon laser photocoagulation, and removal of silicone tamponade.
In Group 4, 42.10% (8/19) of the glaucoma operations were due to neovascular glaucoma and 36.84% (7/19) were due to silicone oil occluding the trabecular meshwork. The ratio of the number of patients who underwent glaucoma surgery due to neovascular glaucoma and silicon oil-induced glaucoma to the total number of patients who underwent glaucoma surgery, and the ratio of the number of patients who underwent glaucoma surgery due to neovascular glaucoma and silicon oil-induced glaucoma to the total number of patients who presented to the retina unit were statistically significantly higher in Group 4 compared to Groups 1 and 2. We consider that the increase in the number of patients with neovascular glaucoma may be due to the patients with retinal vascular disease not receiving intravitreal injections, argon laser photocoagulation, and anti-glaucomatous drug therapy on time because they did not attend their follow-up. Similarly, the increase in the number of patients with silicone oil-induced glaucoma is probably because the patients who had undergone vitreoretinal surgery did not attend follow-up and did not realize that the silicone had emulsified, and therefore they did not receive anti-glaucomatous and silicone removal treatment in a timely manner.
Although studies in the literature suggest that the main cause of silicone oil-induced glaucoma is the emulsification of the silicone, it has been stated that the duration of silicone tamponade stay in the eye may also be effective in the development of glaucoma. It has been shown that as the duration of silicone stay in the eye increases, the rate of emulsified silicone increases, and accordingly there is a greater possibility of glaucoma development due to various reasons, such as silicone transfer to the anterior chamber, angle closure, and rubeosis iridis . The development of silicone oil-induced glaucoma occurs after an average of five to 24 months postoperatively . However, it has also been reported that silicone oil-induced glaucoma can occur even in the postoperative first month . It has also been determined that the decrease in postoperative BCVA is associated with the duration of silicone tamponade stay in the eye .
Similar to the above-mentioned studies, we found that the duration of silicone tamponade stay in the eye had a negative correlation with the preoperative and postoperative BCVA values of the patients who underwent glaucoma surgery due to silicone oil-induced glaucoma. Accordingly, the preoperative and postoperative BCVA values decreased as the duration of silicone stay increased. The longer the silicone remains in the eye, the higher the emulsification rate, resulting in glaucoma and eventually retinal nerve fiber and vision loss. In our study, the mean duration of silicone tamponade stay was significantly longer significantly in Group 4 compared to the remaining groups, which was attributed to the patients not visiting the hospital for their follow-up due to the pandemic.