Effect of 0.5 mm larger donor corneal size on intraocular pressure following penetrating keratoplasty

Background

Glaucoma can develop after penetrating keratoplasty resulting in irreversible loss of vision. The incidence of post-penetrating keratoplasty glaucoma varies from 31% in the early postoperative period to 29% after three months. Various factors are responsible for the rise of intraocular pressure (IOP). This study was carried out to evaluate the effect of 0.5 mm larger donor corneal size on IOP following penetrating keratoplasty.

Methods

Patients were divided into two groups: group I was phakic and group II consisted of aphakic and pseudophakic patients. The same surgical technique was used for obtaining and suturing the donor graft. The viscoelastics and the postoperative regime also remained the same in all cases. IOP was measured by the rebound tonometer.

Results

The incidence of postoperative raised IOP in the first seven days in the phakic group was found to range from 16 mmHg to 25 mmHg and IOP in the aphakic/pseudophakic group ranged from 16 mmHg to 42 mmHg. The IOP in the phakic group after three weeks of surgery was around 12.3 mmHg and that in the pseudophakic/aphakic group was 14.8 mmHg-16.2 mmHg. In aphakic patients, IOP was controlled in the first six months with eyedrops Timolol 0.5% and tablet acetazolamide which was given only for short periods. IOP settled to <12 mmHg with timolol 0.5% after six months. In the pseudophakic patients, IOP became normal by six months. These were inclusive of patients who had undergone anterior reconstruction and/or vitrectomy.

Conclusion

The study proves that keeping the donor corneal size 0.5 mm larger does not affect IOP and that aphakia itself is a factor responsible for rise of IOP due to anterior chamber angle compression.