OPINION OF THE COURT BY LUM, J.

Plaintiff-appellant Donald Yamaguchi appeals from summary judgment entered in favor of defendants-appellees The Queen's Medical Center ("Queen's Hospital") and Dr. Richard S. Dodge, dismissing appellant's medical malpractice action against them as barred by the statute of limitations applicable to medical tort proceedings contained in HRS § 657-7.3 (1976). From what we have ascertained to be the pertinent factual and legal issues concerning the statute, and from the state of the record herein, however, we conclude that summary judgment was improper and remand this case for trial.

I.

Appellant, then sixteen years of age, entered Queen's Hospital on December 9, 1947 for treatment of an ailing right knee. Dr. Richard Dodge performed a surgical biopsy on the joint, and the specimen obtained was diagnosed as malignant bone cancer by Dr. Sumner Price of the hospital's pathology laboratory. Queen's Hospital radiologists Drs. L.L. Buzaid and G.P. Van Nuys administered radiation therapy to the diseased area on eight separate occasions between 1948 and 1949.

Apparently unbeknownst to appellant, Queen's Hospital pathologist Dr. W. Harold Civin, re-examining tissue taken from the knee, disagreed with the original diagnosis and concluded in 1951, 1955 and again in 1958 that the abnormal mass in appellant's knee was a benign tumor. Dr. Civin recorded his findings in three reports stored in the hospital's files, and appellant alleges that neither the hospital nor any physician made an effort to inform him of the new diagnosis or to otherwise follow up on the matter.

Appellant did not learn of the alleged misdiagnosis until 1961 when physicians at the Mayo Clinic informed him that his condition had been erroneously assessed. No signs of trouble appeared, however, until November, 1975, when appellant suffered a slight injury to his knee. Appellant's physicians advised him the following month that he had developed malignant post-radiation cancer in his right thigh bone, and that amputation of his entire right leg was imperative. Appellant alleges that this was the first time he was informed of the potentially dangerous consequences of radiation treatment and of the fact that he had been administered an unnecessary and excessive dose of radiation in 1948 and 1949.

Appellant's right leg was amputated in December, 1975, and he commenced his action six months later on June 30, 1976 against Queen's Hospital, Dr. Dodge and approximately fifty unidentified defendants for damages flowing primarily from the alleged negligent misdiagnosis and the unnecessary and negligently administered treatment. The circuit court granted appellees' motions for summary judgment in November, 1978, however, agreeing with them that the statute of limitations set forth in HRS § 657-7.3 had run on appellant's claim.

Appellant's principal contention on appeal is that the statute of limitations was tolled by appellees' (essentially the hospital's) failure to disclose information of alleged acts of negligence constituting the basis of his claim, or at least that an issue of material fact concerning appellees' concealment of incriminating information remained, precluding summary judgment.

II.

The statute at the heart of this controversy, HRS § 657-7.3 (1976), provides that

(n)o action for injury or death against a chiropractor, clinical laboratory technologist or technician, dentist, naturopath, nurse, nursing home administrator, dispensing optician, optometrist, osteopath, physician or surgeon, physical therapist, podiatrist, psychologist, or veterinarian duly licensed or registered under the laws of the State, or a licensed hospital as the employer of any such person, based upon such person's alleged, professional negligence, or for rendering professional services without consent, or for error or omission in such person's practice, shall be brought more than two years after the plaintiff discovers, or through the use of reasonable diligence should have discovered, the injury, but in any event not more than six years after the date of the alleged act or omission causing the injury or death. This time limitation shall be tolled for any period during which the person had failed to disclose any act, error, or omission upon which the action is based and which is known or through the use of reasonable diligence should have been known to him or as provided in section [ 671-18].

(emphasis added). Enacted in 1973, this legislation created a statute of limitations specifically for medical malpractice actions which theretofore had been governed by the two-year statute of limitations set forth in HRS § 657-7 applicable to property damage and personal injury claims. The statute also codified the rule this court adopted in construing HRS § 657-7 in Yoshizaki v. Hilo Hospital, 50 Haw. 150, 433 P.2d 220 (1967), that the statutory period does not begin to run on medical malpractice claims until the plaintiff discovers, or by acting reasonably should have discovered, "the injury." Jacoby v. Kaiser Foundation Hospital, 1 Haw. App. 519, 523, 622 P.2d 613, 617 (1981). At the same time, however, the legislature was not blind to the rising cost of malpractice insurance and problems of proof attendant with stale claims, both of which were subject to exacerbation under an open-ended "discovery rule." See House Stand. Comm. Rep. No. 455, 7th Haw. Leg., 1st Sess., reprinted in House Journal 947 (1973); Senate Stand. Comm. Rep. No. 665, 7th Haw. Leg., 1st Sess., reprinted in Senate Journal 907 (1973). It imposed a six-year outer limitation on all suits computed from the date of the alleged act or omission regardless of whether the injury caused thereby had or should have been discovered by that time, which period would be tolled only by the defendant's withholding of information of alleged negligent conduct known or which should have been known to him.

At the outset, appellant questions the very applicability of HRS § 657-7.3 to his action since the alleged torts occurred in 1949, twenty-four years prior to the statute's enactment. His argument in favor of applying the general tort statute of limitations in HRS § 657-7 rests upon the well-established rule of construction forbidding the retrospective operation of statutes in the absence of clearly expressed contrary legislative intent. See Clark v. Cassidy, 64 Haw. 74, 77, 636 P.2d 1344, 1346 (1981); Graham Construction Supply, Inc. v. Schraeder Construction, Inc., 63 Haw. 540, 546, 632 P.2d 649, 653 (1981); HRS § 1-3 (1976). We find no impediment to application of this rule to HRS § 657-7.3 to require that the statute be given prospective effect only, as there exists no indication in either the statutory language or the accompanying committee reports that the legislature intended a different result. See House Stand. Comm. Rep. No. 455, supra; Senate Stand. Comm. Rep. No. 665, supra. The problem then becomes one of identifying the event in the lawsuit's evolution, beginning with the injurious act and ending with the filing of the complaint, which is determinative for the purposes of ascertaining when a statute of limitations in effect applies.

The Idaho Supreme Court in Stoner v. Carr, 97 Idaho 641, 550 P.2d 259 (1971) was faced with a malpractice action brought on December 24, 1974 for damages arising from the alleged negligence of a physician in leaving a surgical needle in plaintiff's abdomen on March 9, 1971. The needle was discovered on July 31, 1973 and surgically removed. Defendants argued that the statute of limitations for malpractice actions, as amended in 1971 to include a one-year limitation for claims based on the leaving of foreign objects in the body, applied rather than the pre-1971 version setting forth a two-year limitation for medical tort suits generally. Disagreeing with plaintiff's assertion that application of the 1971 amendment to her claim would be retroactive since the alleged wrong occurred prior to its enactment, the plurality explained that "`[a] law is not retroactive merely because part of the factual situation to which it is applied occurred prior to its enactment; rather, a law is retroactive only when it operates upon transactions which have been completed or upon rights which have been acquired or upon obligations which have existed prior to its passage.'" 550 P.2d at 261, quoting Arnold v. Woolley, 95 Idaho 604, 605, 514 P.2d 599, 601 (1973). It accordingly ruled that the statute of limitations in force at the time the plaintiff's cause of action accrues, rather than that effective at the time of the wrongful act where the two fail to coincide, is that which defines the governing statutory period. Since under Idaho's "discovery" rule plaintiff's cause of action accrued in 1973 with the location of the surgical needle, her suit was precluded by the amended statute's special one-year limitation as it was brought seventeen months from the needle's discovery. See Valenzuela v. Mercy Hospital, 34 Colo. App. 5, 521 P.2d 1289 (1974); Johnson v. Szymanski, 368 So.2d 370 (Fla. Dist. Ct. App. 1979); Patrick v. Morin, 115 N.H. 513, 345 A.2d 389, 390-91 (1975). But see Penrod v. Hoskinson, 170 Mont. 277, 552 P.2d 325, 328 (1976).

We accept the Stoner rule as that which accords logically with the language of HRS § 657-7.3 and our position in Yoshizaki v. Hilo Hospital with respect to HRS § 657-7, by requiring the statute of limitations in effect to run the moment the plaintiff's cause of action accrues — that is, under HRS §§ 657-7 and 657-7.3, the moment plaintiff discovers or should have discovered the negligent act, the damage, and the causal connection between the former and the latter. Jacoby v. Kaiser Foundation Hospital, supra. In the instant case, appellant learned of the alleged negligent misdiagnosis in 1961, but lacked an actionable claim until 1975 when the injury he claims such misdiagnosis caused surfaced. Appellant similarly lacked an accrued cause of action with respect to the negligently administered radiation therapy until that same year when he discovered both the physical injury and its link to the excessive treatment. Assuming that due diligence on plaintiff's part could not have hastened discovery of these elements, HRS § 657-7.3, in effect at that time, applies to both aspects of appellant's claim. We thus now turn to the question of whether the circuit court was correct in determining that the statute of limitations set forth in HRS § 657-7.3 barred appellant's suit.

III.

"It is well settled that summary judgment should not be granted unless the entire record shows a right to judgment with such clarity as to leave no room for controversy and establishes affirmatively that the adverse party cannot prevail under any circumstances." Jacoby v. Kaiser Foundation Hospital, supra at 527, 622 P.2d at 618, quoting State v. Zimring, 52 Haw. 472, 475, 479 P.2d 203, 204 (1970). More specifically, "[s]ummary judgment is to be granted only where there is no genuine issue as to any material fact and the moving party is entitled to judgment as a matter of law." Pickering v. State, 57 Haw. 405, 407, 557 P.2d 125, 127 (1976). In considering whether an issue of material fact exists, "the inferences to be drawn from the underlying facts alleged in the materials (such as depositions, answers to interrogatories, admissions and affidavits) . . . must be viewed in the light most favorable to the party opposing the motion." Technicolor, Inc. v. Traeger, 57 Haw. 113, 118-19, 551 P.2d 163, 168 (1976), quoting Gum v. Nakamura, 57 Haw. 39, 42, 549 P.2d 471, 474 (1976).

Appellant's action for damages based on both the alleged negligent misdiagnosis and unnecessary and excessive radiation treatment, instituted within seven months of his discovery of both the physical injury and alleged wrongs, fell well within the two-year limitation period but beyond the six-year outside limit computed from the date of the injurious act. His claim as to the misdiagnosis, moreover, is not saved by the statutory tolling provision, since appellant had acquired actual knowledge of the alleged negligent act from an independent source in 1961, negating the defendants' duty to inform him of the same from that date. The sole question remaining relative to the effect of HRS § 657-7.3 on appellant's suit was therefore whether the six-year period had been tolled by a failure to reveal information concerning the alleged negligently administered treatment to appellant. This question is ordinarily regarded as one of fact. Blake v. Wernette, 57 Cal.App.3d 656, 129 Cal. Rptr. 426, 429 (1976); see Swope v. Prinz, 468 S.W.2d 34, 42 (Mo. 1971).

The parties to the motion for summary judgment below, as well as the ruling judge, assumed that the tolling provision's operation depended upon a determination of whether the hospital knew or should have known of the alleged tortious acts which it did not disclose to appellant. HRS § 657-7.3, however, touches actions brought against the licensed hospital as the employer of the enumerated health care professionals, "based on such person's alleged, professional negligence . . . or for error or omission in such person's practice . . .," and protects injured patients from concealment of potential claims by allowing the tolling of the six-year limitation only for that period in which " the person had failed to disclose any act, error, or omission upon which the action is based. . . ." HRS § 657-7.3 (1976) (emphasis added). Application of HRS § 657-7.3 to the instant action at all thus requires that appellant have sued Queen's Hospital as the employer of the tortfeasor or tortfeasors. Assuming for the purposes of summary judgment that he had, the pertinent inquiry then becomes (a) whether the employee or employees who committed the tortious act knew or with reasonable diligence should have known of the alleged error in treatment, and (b) if so, whether such person or persons failed to disclose this information to appellant.

Appellant maintains that Queen's Hospital and his doctors knew or should have known of his over-exposure to radiation, that they did not inform him of this fact, and that he discovered it only at the time his cancer surfaced in 1975. The hospital's response, framed with the objective of denying its own knowledge of and duty to reveal the facts alleged, did not discuss the possibility of knowledge of the alleged negligent treatment on the part of any other defendants. The record, consisting primarily of the pleadings and answers to interrogatories served on appellant and Queen's Hospital by each other, neither affirmatively demonstrates nor negates knowledge of the excessive radiation therapy on the part of those defendants other than Queen's Hospital who were named as responsible for the same. Whether those treating appellant would have known of the alleged negligent therapy had they exercised reasonable diligence is likewise not answered by the record and was not addressed by the lower court. Viewing the record and inferences to be drawn from the facts contained therein in a light most favorable to appellant, we find, therefore, at the very least that a genuine issue of fact material to the determination of whether the statutory period was tolled remains, precluding summary judgment.

We reverse and remand this case for further proceedings not inconsistent with this opinion.