(a) The judgment of a court providing permanent alimony for the support of a wife or child or children, or both, rendered prior to July 1, 1977, shall be subject to revision upon petition filed by either the husband or the wife showing a change in the income and financial status of the husband. The petition shall be filed and returnable under the same rules of procedure applicable to divorce proceedings. The petition shall be filed in the proper venue provided by law in civil cases. No petition may be filed by the wife under this Code section within a period of two years from the date of the filing of a previous petition by the wife under this Code section. No petition may be filed by the husband under this Code section within a period of two years from the date of the filing of a previous petition by the husband under this Code section. After hearing both parties and the evidence, the jury, or the judge where a jury is not demanded, may modify and revise the previous judgment so as to provide for the wife or child or children, or both, in accordance with the changed income and financial status of the husband, if such a change in the income and financial status of the husband is satisfactorily proved so as to warrant the modification and revision. In the hearing upon a petition filed as provided in this Code section, testimony may be given and evidence introduced relative to the income and financial status of the wife.

(b) Upon an application as authorized in subsection (a) of this Code section, the merits of whether the wife, or child or children, or both, are entitled to alimony and support are not in issue, but only whether there has been such a substantial change in the income and financial status of the husband as to warrant either a downward or upward revision and modification of the permanent alimony judgment.

(c) An application authorized in subsection (a) of this Code section can be filed only where the husband has been ordered by the final judgment in an alimony or divorce and alimony action to pay permanent alimony in weekly, monthly, annual, or similar periodic payments, and not where the wife, or child or children, or both, have been given an award from the corpus of the husband's estate in lieu of such periodic payment.

(d) Where an application authorized in subsection (a) of this Code section is filed by the husband, the court may require the husband to pay reasonable expenses of litigation as may be incurred by the wife, either for herself or the child or children, or both, in defense thereof.