Penetrating Keratoplasty for Keratoconus : Visual and Graft Survival Outcomes

Objectives: To evaluate the complications, and visual and graft survival outcomes in eyes that had undergone penetrating keratoplasty (PKP) for keratoconus. Methodology: This restrospective study includes 311 patients with keratoconus who had undergone PKP between January 1, 2001, and December 31, 2002, at King Khaled Eye Specialist Hospital. All patients were followed up postoperatively (maximum follow-up, 65.77 months). Results: The mean age of patients with keratoconus at transplantation was 23.72 years. A preoperative best spectaclecorrected visual acuity (BSCVA) OF 20/40 or better was achieved in 13 eyes (4.2%). At a mean follow-up of 27 months, 212 eyes (68.2%) achieved a BSCVA of 20/40 or better. Postoperative visual acuity was significantly associated with preoperative visual acuity (P < 0.00). Only 6 eyes (1.9%) experienced graft failure, with a mean follow-up of 23.62 months. The graft rejection rate (6.8%) was a significant risk factor for failure (P = 0.00). Age, gender, corneal graft diameter, and intraoperative vitreous loss had no statistically significant effects on the PKP outcome (P> 0.05). Kaplan-Meier analysis revealed that the probabilities of graft survival were 99.8% at 1 year and 97.6% at 5 years after transplantation. Conclusion: Performing PKP in eyes with keratoconus is associated with good visual results and an excellent graft outcome.


Introduction
In keratoconus, the cornea progressively thins and steepens, leading to the development of myopia and irregular astigmatism and, eventually, to the loss of best spectacle-corrected visual acuity (BSCVA); this noninflammatory ecstatic corneal disorder occurs naturally and is characterized as bilateral but asymmetrical. (1)Various therapeutic modalities for this disorder exist, including spectacles, contact lenses, lamellar keratoplasty (LK), penetrating keratoplasty (PKP), and, recently, intracorneal rings (ICRs).(1, 2) The type of treatment chosen depends on the severity of the disorder.In patients with keratoconus who have contact lens failure or apical scarring, PKP is a well-accepted treatment.
(2, 3) Previous researches have revealed that keratoconus is one of the leading indications for corneal transplantation in Saudi Arabia and throughout the world.(3, 13) The purpose of this retrospective study is to determine the outcomes of a series of consecutive PKPs performed for patients with keratoconus at King Kahled Eye Specialist Hospital in Riyadh, Saudi Arabia.

Methods
After approval was obtained from the Institutional Review Board, a retrospective review was conducted of the medical records of all patients with keratoconus who had undergone PKP from January
At the most recent visit, 305 grafts (98.1%) were clear, and only 6 grafts (1.9%) had failed.The mean time to graft failure was 23.62 months (range, 2.63-44.7 months) after transplantation.The overall probabilities of graft survival were 99.8% at 1 year and 97.6% at 5 years (Figure 2).At least one episode of a rejection reaction occurred in 21 eyes (6.8%) of 311 eyes, with 3 eyes (0.96%) developing irreversible graft failure (P = 0.009).Of 218 eyes with a recipient size of ≥7.5 mm, 15 eyes (6.9%) developed a graft rejection episode compared with 6 eyes (6.45%) of 93 eyes with a recipient size of <7.5 mm, which is not statistically significant (P > 0.05).

Discussion
The number of keratoconus surgeries being performed in Saudi Arabia is rising.This rise has been attributed to population explosion, better patient access, improved healthcare availability, and an increased availability of grafts. (7)(16) In this study, PKP was performed in relatively young patients (mean age was 23.72 years at the time of PKP), with a male predominance of 64.0%.In a study by Javadi et al, (16) the mean age at the time of surgery was 28.2 years, with 73.2% of patients being male.However, de Lavalette et al (17)   reported a female predominance of 65% in their study.Various studies have reported that keratoconus has an equal prevalence in both genders, (1, 18) a greater prevalence in males, (14-16, 19) and a greater prevalence in females. (20)One possible reason for the increased relative frequency of male subjects undergoing transplantation compared with female subjects is an increased tendency for males to receive surgical treatment so as to improve occupational performance.
7)21,22) In a previous series of 90 consecutive PKPs performed in eyes with keratoconus and vernal keratoconjunctivitis between 1986 and 1996 in Saudi Arabia, 83 grafts (92.2%) were clear after a mean followup period of 44.7 months. (22)Price et al (21)   found a 5-year graft survival rate of 98% among patients who underwent PKP for keratoconus.
In the present study, complications other than graft rejection were not significantly related to graft failure after PKP (P = 0.511).Of the 311 eyes in this study, 21 eyes (6.8%) had rejection episodes, and 3 eyes (0.96%) developed irreversible graft failure.This rate of rejection episodes is lower than in other series.For instance, Watson et al (23) reported 11 rejection episodes in 22 patients who underwent PKP, and Troutman and Lawless (8) reported a rejection rate of 18.5%.There was no significant difference in graft failure rates between male and female patients in any age group.In the current series, donor-recipient disparity had no effect on survival outcome.
The prognosis for graft survival in patients with keratoconus is considered excellent if surgery is performed on young patients who are highly motivated and compliant and who do not have other conditions that compromise visual potential (eg, age-related retinal disease).The 5-year Kaplan-Meier survival rate in the present series of 97.6% is comparable to those of other series. (24,25)Age, gender, and recipient size did not contribute to an increased risk of graft failure after PKP in the present study's patients.
The incidence of successful 20/40 VA was not significantly affected by graft rejections.Only 2 patients who had experienced an episode of rejection had a VA worse than 20/60.These findings may indicate that an adverse effect on VA cannot be attributed to a rejection episode that has been successfully treated.
In summary, PKP is associated with a good visual outcome and prognosis for graft survival with a low complication rate in eyes with keratoconus.