Nanophthalmus originates from the Latin word "nanos" meaning dwarf and means small eye. However, it differs from microphthalmia, which is also used to mean small eyes, in that it is not accompanied by developmental defects such as coloboma. It is typically bilateral and all eye structures except the lens are small. For this reason, while the ratio of lens volume to the entire eye volume is normally 4%, it is around 10-30% in these eyes. Since the size of the lens narrows the angle, pupillary block and angle-closure glaucoma are common in these cases. Generally, the anterior-posterior diameter of the eye is less than 21 mm and there is high hyperopia between +8 and +21 D.1
Posterior segment findings are caused by the abnormally thick sclera, which shows structural differences. The most common finding is loss of choroidal pattern due to thickened choroid and exudative retinal detachment.1 Exudative retinal detachment usually progresses with remissions and exacerbations and is a long-term condition. It has been observed that it does not respond to medical treatment and conventional retinal detachment surgery.2 At first, it was thought that exudative retinal detachment was caused by thickened sclera pressing on the vortex veins, and it was shown that the detachment regressed with vortex vein decompression.3 Later, in nanophthalmic eyes, there was resistance to the transscleral outflow of intraocular protein and fluid, and this It has been reported in different studies that scleral resection (sclerectomy) and sclerostomy surgeries performed for this reason provide successful results. 4-9
Here, two nanophthalmus cases who underwent four-quadrant deep sclerectomy with mitomycin-C due to exudative retinal detachment are presented.
CASE 1: A 15-year-old male patient was sent to our clinic with the diagnosis of serous macular detachment in both eyes that had been going on for 6 months. On examination of the patient, who also complained of night blindness, the visual acuity was +17.00 D and 20/400 (right-left), the eyes appeared enophthalmic and small, the intraocular pressure was 18 mmHg bilaterally, the corneal horizontal diameter was 10.5 mm in the right eye and 10 mm in the left eye. and the anterior chamber is slightly shallow and angle 2-3. It was found to be slightly open. Fundus examination revealed bilateral exudative foveal retinal detachment and peripheral retinal pigmentary changes (Figure 1). Ultrasonography (USG) and it While optical coherence tomography (OCT) confirmed the diagnosis of bilateral macular detachment (Figure 2), the axial length of both eyes was measured as 17 mm in USG.
With these findings, the patient had both eyes as described previously by Johnson and Gass5. Sclerectomy surgery was performed accordingly. Briefly, rectangular sclerectomies of 2/3 sclera thickness were created in each quadrant, with the anterior border in the equatorial region being the insertion area of the recti and the posterior border being the anterior of the vortex veins. Sclerostomies of 1-2 mm size were opened in the center of each sclerectomy bed, but no effort was made to drain the subretinal fluid. After surgery, fundus examination and OCT showed that the macular detachment had regressed somewhat, and at the end of 5-month follow-up, visual acuity was 20/200 in the right eye and 20/250 in the left eye. However, nine months after surgery, the patient's visual acuity remained at the same level, but an increase in macular detachment was observed along with a worsening of subjective symptoms. Considering that the clinical deterioration might be due to episcleral scar development, the patient was operated again. After sclerectomies were performed in the second operation, 0.02 mg mitomycin-C was injected into the sclera for 3 minutes, as previously described by Akduman et al.10. applied for a period of time. While there was a slight decrease in subretinal fluid in the postoperative period, there was no change in vision levels.
CASE 2: A 24-year-old male patient, who stated that he has had low vision since birth, came to our clinic with the complaint of decreased vision in his right eye for 20 days. applied. On examination, visual acuity was +18.00 D, 20/400 in the right eye and 20/200 in the left eye. Anterior segment examination revealed that both eyes were smaller than normal. Intraocular pressure values were 17mmHg right and left. On fundus examination, there was exudative foveal and peripheral retinal detachment in both eyes, although it was more bullous in the right (Figure 3). On USG, the axial axes were 13 mm in the right eye and 12 mm in the left eye. A four-quadrant deep sclerectomy was performed on the patient's right eye with mitomycin-C as mentioned above. While a rapid regression was observed in the exudative retinal detachment on the first postoperative day, in the first postoperative month, the visual acuity of the right eye was 20/200 and there was a very significant decrease in the exudative retinal detachment. The patient was examined again in the 2nd month postoperatively. When evaluated, it was observed that although the visual acuity was at the same level, the peripheral retinal detachment completely regressed and the foveal detachment decreased significantly (Figure 4).
DISCUSSION
Exudative retinal detachment is one of the common findings of nanophthalmus. Histopathological studies on nanophthalmic sclera show accumulation of glycosaminoglycans in the matrix between irregular collagen bundles. These abnormalities in the structure cause a thick and hard sclera.11 Thickened sclera increases the resistance to transscleral fluid and protein flow and can also cause congestion in the choroidal vessels by applying pressure to the vortex veins.12 Thus, fluid and protein accumulate in the choroidal stroma, which lasts for a long time. The condition causes decompensation of the retinal pigment epithelium, accumulation of fluid in the subretinal space, and ultimately exudative retinal detachment.
Although it has been reported that serous retinal detachment is successfully treated with vortex vein decompression 3, Gass later developed a vortex vein He put forward a new theory about the formation of serous detachment due to the recovery of the serous detachment in the patient despite the rupture of the vein during decompression, and stated that in fact the subretinal fluid is absorbed transsclerally and this is prevented in nanophthalmos patients due to the thickened sclera, that is, the drainage is from the sclera, not from the vortex veins, and that serous detachment occurs as a result of thinning of the sclera with sclerectomies. claimed that it regressed.4 As a matter of fact, in a group of patients with serous retinal detachment due to uveal effusion and nanophthalmus, they reported that they achieved resorption of the detachment by performing only sclerectomies.5 Akduman et al. They argued that the reason for the closure of the scleral window after sclerectomy may be episcleral scarring, and that this complication can be prevented with topical mitomycin-C applied during surgery. 10
After sclerectomy surgery was first proposed by Gass in 1983, different studies have found it to be secondary to Hunter syndrome and nanophthalmus. It has been shown to be successful in the treatment of uveal effusion that develops.6-9 In a study of 20 patients who underwent sclerectomy due to idiopathic uveal effusion, 96% of the eyes were treated within 6 months following one or two scleral thinning procedures. They reported that the subretinal fluid completely receded within 2.4 months (average of 2.4 months), and the recurrences that developed in 23% of the eyes regressed spontaneously or with surgery after an average follow-up of 41 months. In the same study, it was stated that an increase or stabilization in visual acuity was observed in 91% of the eyes, but this increase was limited due to photoreceptor and retinal pigment epithelium damage caused by chronic retinal detachment.5
In the first case, it was accompanied by exudative retinal detachment. There were peripheral retinal pigmentary changes. Khairallah et al. reported that retinal pigmentary changes were observed in 22.2% of posterior microphthalmos.13 Nanophthalmus may be caused by mutations in genes specific to the retinal pigment epithelium. Yardley et al. They suggested that the mutation in the vitelliform macular dystrophy gene may cause nanophthalmus, which is associated with diffuse retinal dystrophy.14
The clinical improvement in the second case was much faster and more pronounced than in the first case, and the pigmentary retinopathy in the first case caused a decrease in the number of healthy RPEs, resulting in a decrease in the number of healthy RPEs in the subretinal space. It can be explained as preventing the liquid from being pumped sufficiently. In the first case, subretinal fluid drainage and gas tamponade with subretinal fluid drainage by pars Uzman vitrectomy may be a more effective alternative in removing the existing subretinal fluid.
As a result, four-quadrant sclerectomy seems to be an effective method in the treatment of serous retinal detachment secondary to nanophthalmus. However, in some cases of nanophthalmus, pigmentary retinopathy accompanies the picture, and this situation negatively affects the response to treatment due to decreased RPE functions.
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