Limited Vitrectomy in Patients with Idiopathic Macular Hole

Comparison of outcomes of idiopathic macular holes treated by vitrectomy with air or silicone oil tamponade based on the hole size

AIM

To compare the efficacy of vitrectomy combined with air or silicone oil in the treatment of idiopathic macular hole (IMH).

METHODS

According to the results of high-definition optical coherence tomography (HD-OCT), 75 cases (75 eyes) of IMH in stage II-IV (Gass stage) in the General Hospital of Chinese PLA from January 2017 to December 2019 were collected for this retrospective study. The best corrected visual acuity (BCVA) and minimum diameter of IMH (MMHD) were measured. Eyes underwent vitrectomy combined with internal limiting membrane peeling operation, and were divided into disinfection air group (30 eyes) and silicone oil group (45 eyes) according to the intraocular tamponade. For MMHD≤400 µm (MMHD1), there were 23 eyes in air group and 16 eyes in silicone oil group. For MMHD2>400 µm (MMHD2), there were 7 eyes in air group and 29 eyes in silicone oil group. One month after surgery, the closure rates of IMH and BCVA were compared and analyzed. According to HD-OCT, the closure shape was graded with A (bridge closure) and B (good closure).

RESULTS

The closure rates of air group and silicone oil group were 86.67% and 95.56% respectively with no significant difference (P>0.05); For MMHD1, those of air group and silicone oil group were 95.65% and 100% respectively with no significant difference (P>0.05); For MMHD2, those of air group and silicone oil group were 57.14% and 93.10% respectively, and those of the silicone oil group were higher than the air group (P<0.05). There was no significant difference in the closure shape grade between MMHD1 air group and silicone oil group (P>0.05). The proportion of Grade B in MMHD2 silicone oil group was higher than that in the air group (P<0.05). BCVA of each group after operation was better than that before operation, and there was no significant difference between air group and silicone oil group. While among them, MMHD1 air group was better than silicone oil group (P<0.05), and there was no significant difference between MMHD2 air group and silicone oil group (P>0.05).

CONCLUSION

For smaller IMH (≤400 µm), the efficacy of vitrectomy combined with air should be considered better than silicone oil; for larger IMH (>400 µm), the efficacy of silicone oil may be better than air.

Pre-retinal delivery of recombinant adeno-associated virus vector significantly improves retinal transduction efficiency

Intravitreal injection is the most widely used injection technique for ocular gene delivery. However, vector diffusion is attenuated by physical barriers and neutralizing antibodies in the vitreous. The 13-lined ground squirrel (13-LGS), as in humans, has a larger relative vitreous body volume than the more common rodent models such as rats and mice, which would further reduce transduction efficiency with the intravitreal injection route. We report here a “pre-retinal” injection approach that leads to detachment of the posterior hyaloid membrane and delivers vector into the space between vitreous and inner retina. Vectors carrying a ubiquitously expressing mCherry reporter were injected into the deep vitreous or pre-retinal space in adult wild-type 13-LGSs. Then, adeno-associated virus (AAV)-mediated mCherry expression was evaluated with non-invasive imaging, immunofluorescence, and flow cytometry. Compared to deep vitreous delivery, pre-retinal administration achieved pan-retinal gene expression with a lower vector dose volume and significantly increased the number of transduced cone photoreceptors. These results suggest that pre-retinal injection is a promising tool in the development of gene therapy strategies in animal models and is a potential approach for use in human research, particularly in younger individuals with an intact posterior hyaloid membrane and stable vitreous.

Comparison of postoperative anterior segment changes associated with pars plana vitrectomy with and without vitreous base shaving

AIM

To compare changes in anterior segment topography and axial length (AL) evaluated with Pentacam and IOL Master after pars plana vitrectomy (PPV) performed with and without vitreous base shaving.

METHODS

This prospective study included patients who underwent PPV or phacoemulsification+PPV (Phaco+PPV) for various indications. Patients who underwent total posterior hyaloid detachment and excessive vitreous base shaving with scleral indentation were referred to as complete PPV (c-PPV). The patients whom posterior hyaloid was separated as far as the posterior arcades and vitreous base shaving with scleral depression was not performed were classified as the partial PPV (p-PPV) group. All patients underwent detailed ophthalmologic examinations preoperatively and 1wk, 1, and 3mo postoperatively. Changes in the anterior chamber depth (ACD), anterior chamber volume (ACV), iridocorneal angle (ICA), central corneal thickness (CCT), and keratometric measurements (K₁ and K₂) were evaluated with Pentacam HR. Changes in the AL measurements were analyzed with IOL Master.

RESULTS

A significant increase in ACD was observed in c-PPV cases (P=0.02), but this increase was not significant in the p-PPV group (P=0.053). In contrast, ICA increased significantly in the c-PPV group (P=0.02) but decreased in the p-PPV group (P=0.09). BCVA was significantly improved in the c-PPV group from week 1 (P<0.001) while the increase in the p-PPV group reached significance at 3mo (P=0.035). CCT increased in the first week and later returned to baseline in both groups. No significant differences in the other parameters were observed between the groups, and there were no significant changes in intraocular pressure, ACV, AL, K₁ or K₂ values (P>0.05 for all).

CONCLUSION

Incomplete posterior hyaloid excision and not removing the vitreous base in PPV surgeries may create a more stable anterior chamber, thus preventing the downward movement of the lens-iris diaphragm, and may cause ciliary body retraction, thereby reducing ICA. Awareness of these effects can provide some amount of guidance to physicians in selecting the appropriate PPV procedure and preempting surgical complications.